IFCEE 2015

In this paper, a reliability analysis is presented to compute the allowable bearing capacity of shallow strip footing resting on jointed rock masses. The rock is assumed to follow the non Hoek–Brown failure criterion. Vertical loading case is considered in the analysis. In this study, the Bell’s approach has been used for the computation of ultimate bearing capacity. Jointed rock mass properties generally vary from location to location and also may change with time. Additional uncertainties may arise due to the laboratory estimation of the in situ rock properties. The conventional deterministic analysis based on the factor of safety concept in the estimation of bearing capacity fails to properly account variability. The variability is systematically incorporated in the bearing capacity calculations using reliability based design optimization (RBDO). In this study, the orientation, spacing, and strength parameters of discontinuities are considered to be random variables. Allowable bearing capacity is computed by considering the variability associated with the discontinuity orientation (θ₁), rock material frictional angle (ϕ_r), and discontinuity frictional angle (ϕ_j), uniaxial compressive strength of intact rock (σ_ci) and joint spacing (S). The graphs are plotted for the discontinuity orientation of joints in rock mass against allowable bearing capacity for the target reliability index (β) = 3.

Two centrifuge tests were performed at the University of Colorado Boulder to fundamentally evaluate site performance and soil-foundation-structure-interaction (SFSI) on uniform, medium-dense, saturated sand undergoing a range of broadband earthquake motions with different characteristics. The test results were also used to evaluate and quantify the capability of a state-of-the-art numerical tool in capturing the key response parameters of interest, such as excess pore pressures, accelerations, and settlements at key locations. In this paper, the experimentally measured and numerically computed excess pore pressures and accelerations within the soil in free-field and under the foundation are compared, showing reasonable agreement (with residuals in spectral accelerations and Arias intensities ranging from −1.5 to 1). Neither experimental nor numerical results indicated a decrease in foundation accelerations compared to the free-field soil at higher frequencies, which is due to a larger degree of excess pore pressure generation and strength loss in the free-field compared to the soil under the confining pressure of the structure.

The evaporative and sedimentary environment that has prevailed over the southern shores of the Persian Gulf region (eastern Saudi Arabia, Qatar, and United Arab Emirates) has produced salt-encrusted flat areas known in Arabic as “sabkha”. Building activities on sabkha areas have posed problems and challenges to the construction industry, triggered primarily by the excessive salts present in both the sediments and their shallow ground waters. In general, sabkha sediments are cemented and uncemented layers of sand/silt material, interbedded with pockets of clay and mud, where calcium carbonate and more recent digenetic minerals (gypsum, anhydrite) serve as the principal cementing agent. The geotechnical aspects of sabkha are addressed with particular reference to building foundations. Simplified soil profiles from selected sabkha sites with standard penetration test results are shown. The effectiveness of some soil densification methods, as a means of improving engineering properties of sabkha sediments, is touched upon. The paper concludes by offering guidelines for proper field investigation in sabkha terrain, with a geochemical component as an essential part of the geotechnical investigation.

Piedmont residual soils (PRS) comprise much of Virginia, Georgia, and the Carolinas. Thus, a better understanding of their stiffness properties is of paramount importance. The hallmarks of the soils within the Piedmont region are their low Standard Penetration Test (SPT) blow counts, saprolitic and its silty nature. To understand the stiffness properties of PRS, geotechnical exploration and in situ testing were conducted using SPT and Flat Dilatometer (DMT) testing. The results of the geotechnical explorations and in situ testing were studied and used to predict the settlement of the PRS. The results of the predicted settlement calculations were verified with the post-construction monitoring data and the recommendation of a method to predict the settlement of Piedmont soils was provided.

The analyses of shallow foundations are mainly based on the assumption of Taylor (1948). Taylor (1948) assumed uniform contact stresses under footings. Until now, this assumption has been widely used as an appropriate assumption. Since that early date, researchers have been interested in studying the real distribution of the contact stress. Strip foundations are typically used in building construction, so researchers considered this footing in their experimental measurements of the contact stress. In this paper, the comparison is established between the contact stress distribution of the finite element method (FEM) using different soil models and the measured distribution under strip footing. The contact stresses are found to be concentrated near the edges and slightly lower under the footing center. This distribution resulted from experimental measurements and FEM using Mohr-Coulomb soil model. Additionally, the effects of the soil type and depth of footing embedment on the analyses of the strip footings are investigated. The paper also discusses the analyses of the isolated and the combined footings using 3D FEM. For the studied footings, the contact stresses are concentrated near the edges and low under the footing center. The concentrations near the edges have long arms when calculating the maximum bending moments (M_max). Therefore, the resultant moments from the real distribution under a single footing are always more than those obtained using the Taylor assumption. Real distributions of the contact stresses under shallow foundations should be investigated using large-scale models in field.

The first of these companion papers shows the effect of footing rigidities on the distribution of contact stresses under footings and presents the effect of footing rigidities on increasing maximum flexural moments under footings to be more than that calculated using uniform contact stress. The assumption of uniform contact stresses is widely used in Egypt and overseas when analyzing foundations. Since early implementations, footings were designed and did not collapse due to this problem. Therefore, a study of the factors that are not considered in foundation analyses is required. In this paper, the effects of superstructure rigidity and a foundation’s tie beams, or “semmels”, on the design of foundations are investigated. The superstructure rigidity has significant effects on the redistribution of column loads and the damping of the differential settlements between columns. Superstructure rigidity also affects the values of the modulus of subgrade reactions, which are presented by the geotechnical engineer without considering superstructure rigidity. Therefore, cooperation between the structural and geotechnical engineers is essential to obtain the appropriate straining actions on the superstructure and foundation members. The semmels affect the shape of the contact stress under footings and change the static system of footings. Semmels have minor effects on differential settlement damping, which is not commonly known. The superstructure rigidity also affects the strap foundations, and has a major effect on the redistribution of inner and outer column loads. The strap beam prevents the overturning of outer footings and makes the contact stress under outer footings near uniform.

Seismic isolation systems have been extensively used in a number of critical structures to protect important civil infrastructure from risks posed by earthquakes. Despite the maturity of this technology, the application of seismic isolation to Nuclear Power Plant (NPP) facilities is quite limited. The effectiveness of the isolation system on NPPs has been questioned due to the significant and well-documented soil-structure interaction (SSI) effects on the response of large structures. The tendency of SSI to significantly shorten the predominant frequencies of the excitations felt by the heavy structure could reduce the effectiveness of isolation. On the other hand, base isolation leads to considerably lower frequency and significantly smaller base shear. Thus, the effect of SSI on seismically isolated NNPs is of great interest, since base isolation offers the opportunity to use existing standard designs in regions with higher seismicity. In this paper, an isolated NPP model is used to study the effects of soil-structure interaction effects on the seismic response of the system. Different ground motions are used to estimate the dispersion of the NPP response. Similarly, different soil profiles are examined parametrically to assess the influence of soil properties on the system behavior. The response of the isolated structure is compared to that of the conventional structure to illustrate the effectiveness of the seismic isolation system. Issues related to the numerical simulation of the problem are discussed as well.

The nonlinear response of shallow foundations when subjected to combined loading has been extensively studied by several researchers that have used sophisticated numerical tools and performed large or small-scale experimental investigations to explore the underlying mechanisms. It has been shown that failure in the form of soil yielding or foundation uplifting may accommodate high ductility demand and increase the safety margins, providing promising evidence for incorporation of such response in design provisions. The rocking response of a single degree of freedom system (SDOF) on sand was explored through a series of centrifuge tests that were performed at the Center for Earthquake Engineering Simulation (CEES) at Rensselaer Polytechnic Institute. The SDOF system was supported by a surface foundation and a tactile pressure sensor was placed at the soil-foundation interface to capture the evolution of the foundation contact area and the vertical stress distribution while the system was subjected to cyclic loading of increasing amplitude. The results obtained from experiments on loose and dense dry sand are discussed in this paper.

The concern of soil compressibility is critical in settlement calculation for foundation engineering. Consolidation parameters of soil are generally obtained from laboratory testing, which is time-consuming and beyond the scope of many project budgets. There are numerous approaches to estimate the consolidation parameters, particularly the compression index (C_c) in order to determine the potential settlement in practice. However, due to the limitation in computational aids in the past, the correlations only appeared as linear functions. Furthermore, most proposed equations were based on a single soil property index while the compressibility of soil may be affected by more than a single soil parameter at the same time. Thus, most derived empirical equations resulted in a low statistical fitness compared to the actual experimental data. This study attempts to develop a correlation of C_c from the soil liquid limit (LL) and natural water content (W_n) as two independent variables in a more mathematically complex relation. For this study, 150 consolidation test results were obtained from various locations across the Gulf Coast of Texas by professional service industries, Inc. from over 60 projects dating from 2009 to 2012. The proposed empirical equation was compared with other empirical equations derived in the past in term of statistical fitness. The results of this study can provide a better estimation technique for C_c and thus, better estimation for settlement of foundation in the Guld Coast area.

Sands have been reported to experience changes in penetration resistance, small strain stiffness, and liquefaction resistance over time under sustained loads. These phenomena are particularly distinct after disturbances, such as dynamic in situ compaction. A hypothesis of static fatigue indicates delayed fracturing of micro-morphological features at inter-granular contacts as a key cause of the time-dependent effects in sands. The micromechanical evolution of grain surfaces at contacts was studied using discrete element method (DEM) simulations. Grains were simulated as sets of multi-bodies joined by bonds described by the parallel-bond stress corrosion model (PSC), capable of simulating the time-dependent stress corrosion process of sand grains. This process is central to static fatigue of asperities at inter-granular contacts. Numerical loading tests and static fatigue tests of a single contact were simulated. A single inter-granular contact comprises of many sub-contacts or contact “points”, with a number of sub-contacts increasing during grain convergence. Contact stiffness and friction were shown to increase during static fatigue. Biaxial tests on a model of a sand grain assembly were then conducted, with different contact stiffness and friction. The results are consistent with the static-fatigue hypothesis.

The discrete element method (DEM) was developed about 35 years ago to simulate particulate interaction of granular materials. However, DEM is a computationally expensive method despite significant algorithmic developments that have been made to enhance the computational performance. In this study, a new simulation approach is proposed that runs nearly as fast as the simulation methods used in the computer graphics area while keeping the simulation fidelity required for engineering applications. The proposed impulse-based DEM (iDEM) uses collision impulse instead of contact force, and directly handles velocity while bypassing integration at the acceleration level. Contact force is not an integral part of simulation, but retrieved via an original proposed formulation. The method is robust, numerically stable and results in significant speed-up of almost two orders of magnitude relative to conventional DEM, which makes iDEM as a suitable tool for large scale simulation of granular materials.

A numerical model is presented for one-dimensional large strain consolidation of a layered soil stratum. The algorithm accounts for vertical strain, soil self-weight, conventional constitutive relationships, changing material properties during consolidation, unload/reload, time-dependent loading and boundary conditions, an externally applied hydraulic gradient, and multiple soil layers with different material properties. The model can also accommodate depth-dependent loading and variable preconsolidation stress profiles. Verification checks of the model show excellent agreement with available analytical and numerical solutions for consolidation of soils with multiple layers and depth-dependent loading. An overview of this model is presented and a parametric study is performed to illustrate the effects of large strain and depth-dependent loading on consolidation response of layered soils. The simulations indicate that large errors may occur when stress reduction with depth is not correctly accounted for.

Several recent construction projects in Northeast Ohio have experienced significant sulfate induced heaving in cement stabilized soils. It is well known that the reaction between the sulfate and alumina in soils and calcium of a lime or cement stabilizer often leads to the formation of ettringite, an expansive sulfate mineral that may contribute to the expansion. This subject has been extensively researched in the past but most of the studies have been focused on the experimental aspects. This paper presents a numerical approach to understanding the observed heaving in stabilized soils. A chemo-mechanical constitutive model is employed to address the chemically induced swelling strain. Kinetics of gypsum water reaction is used to explore the evolutionary processes involved. A number of important studies have shown that multiple mechanisms may be involved in addition to formation of ettringite. Consequently, in the present study, numerical simulations are performed to explore different scenarios characterized by different predominant mechanisms. The results have shown that ettringite formation and osmosis swelling can act as separate dominant mechanisms or play comparable roles in this heaving process.

To clarify the pore water chemistry effect on the mechanical behaviors of the soft marine clays, artificial soil samples with a mixture of kaolinite/bentonite are prepared by controlling its mineral composition, specific surface area and pore water salinity in the experimental investigation. Then, a specific oedometer test was developed to conduct pore water percolation with sodium chloride salt solution of 4.9% in mass ratio and deionized water. During the percolation tests, the deformation and injection volume were observed to study the influence of freshwater or seawater process. After percolation, a loading and unloading procedure is performed to clarify the pore water desalination effect on mechanical behaviors. The results indicated that the compression index C_c and swelling index C_s did not change significantly after the yield stress, whereas the initial oedometer modulus E_Oed increases with pore water salinity and a larger secondary deformation was observed for the salt intrusion process. The hydraulic conductivity k is 7 to 10 times larger with a salt solution than that with distilled water in the beginning of injection. When the oedometer tests were finished, the microstructure was studied by mercury intrusion porosimetry (MIP), and it was demonstrated that deionised water led to a porosity increase.

In this study, a three-dimensional microscale framework utilizing the discrete element method (DEM) is presented to analyze the seismic response of soil-foundation-structure systems subjected to three-directional base motion. The granular soil deposit is idealized as a collection of spherical particles using DEM. The foundation is modeled as a rigid block composed of clumped particles and its motion is described by the resultant forces and moments acting upon it. The structure is modeled as a column made of particles that are clumped to idealize a rigid structure. Analysis is done in a fully coupled scheme in time domain. Simulations were conducted to investigate the response of the deposit with and without the structure to various scenarios of multidirectional shaking patterns. Vertical motion amplification in the free-field was similar to that of shear wave propagation. However, there was less nonlinearity for vertical motion compared to horizontal motion. Lateral motion had small impact on the amplification of vertical input motion. The inclusion of vertical motion did not influence the amplification of horizontal motion at frequencies far from the resonance frequency of vertical motion.

The Sacramento-San Joaquin Delta hosts approximately 1800 km of man-made levees most of which rest atop peaty soils. The cyclic behavior of the levees and the settlement potential of the soft underlying peat are studied via large scale 9 m radius centrifuge testing at the NEES@UCDavis equipment site. Given the high compressibility of peat, it is crucial to properly estimate the expected settlements during model construction and spin up due to the increased effective stresses. The consolidation behavior is nonlinear at low effective stress, and traditional calculations assuming a linear relation between void ratio and logarithm of effective stress do not provide reasonable predictions. Preliminary small scale 1 m radius centrifuge experiments helped to evaluate the variation of the consolidation index C_c during testing and to iterate a suitable pre-consolidation procedure. Shear strength for normally consolidated peat was also identified as critical parameter, and a simple procedure to calculate a factor of safety against bearing capacity failure during spin-up is proposed. Settlement predictions using the 1-D theory along with models from literature and analysis results from SETTLE3D were plotted against the measured settlements observed during the 9 m radius centrifuge study. SETTLE3D analysis, calibrated with C_c parameters measured during the various g-levels from the small scale centrifuge tests, provided the most reliable results and matched the test data very well. Models found in the literature under predicted the settlements at low confining pressures but showed similar consolidation indices at larger stress levels.

Expanded polystyrene (EPS) geofoams are being widely used in civil engineering. They are mainly used to construct embankments over weak sub soils because of their light weight property. Embankment constructed with geofoam as fill material typically consists of geofoam blocks with a load distribution slab and a soil cover above it. Settlement of such embankments is critical in the design due to high compressibility of geofoam. In this paper, finite difference program (FLAC—fast lagrangian analysis of continua) is used to obtain the settlements at the top of embankment due to applied loading. Live loads as per ASSHTO specifications are applied on the embankment. The numerical model is also used to analyze the vertical stresses on geofoam due to applied loading. Parametric studies are performed for various thicknesses of soil cover above geofoam (30 cm, 75 cm, and 100 cm), and for two different values of elastic modulus of geofoam (1 MPa and 10 MPa).

An experimental program was conducted to quantify the strain rate dependency of silica sand under different low to intermediate strain rates. Measurements of axial stress, axial strain and stiffness were explored to assess the sensitivity of mechanical properties to strain rate. Strain rates were applied on samples subjected to uniaxial compression stresses within a range of 0.01 to 100 %/s. The tests help facilitate the incorporation of strain rate dependency of soil response in geotechnical modeling of soil-structure interaction problems. Available observations of the response of sand under monotonic loading suggest that sand may exhibit significant strain rate dependency.

Three types of undrained behavior: flow, limited flow and non-flow have been observed for sands. According to critical state soil mechanics (CSSM), these types of behavior depend on the initial state of sands. 3D discrete element method (DEM) was used in this study to simulate these undrained behaviors. Soil elements consisted of assemblies of 3D ellipsoid particles were used as soil element. The effects of both contact stiffness and the strain rate in terms of time step were investigated on undrained behavior. The micro-mechanical response, as measured by coordination number showed a relationship with the key types of behavior. Finally, the undrained responses were evaluated within a critical state soil mechanics framework as obtained from the DEM simulations.

T-walls are floodwalls that consist of reinforced concrete in an inverted “T” shape. These structures are supported on batter piles, and they are commonly used in New Orleans and the surrounding area to protect low-lying regions against hurricane-induced flooding. Since the soils in southern Louisiana often include very soft and compressible clays, T-walls need to be designed to resist the stresses and bending moments that can develop in the batter piles due to settlements. However, the current T-wall design procedure for estimating settlement-induced bending moments is largely based on numerical models that have only been validated to a limited extent. Therefore, a series of centrifuge tests is currently being performed to investigate and physically model the effects of settlement-induced bending moments on pile-supported T-walls. This paper describes one of these centrifuge tests as well as the development and validation of a corresponding numerical model. The results from the numerical model are in good agreement with the centrifuge test results, which is an indication that numerical modeling can be used to realistically estimate the magnitude and distribution of settlement-induced bending moments.

Using a large database derived from 153 full scale load tests on axially loaded pile foundations, a more refined direct cone penetration test (CPT) method of pile capacity analysis is developed from the 1997 UniCone approach proposed by Eslami and Fellenius (1997). A larger database permits separation of pile type and installation method: drilled, augered, jacked, and driven. Also, tension tests are separated from compression load tests. It is found that the original 5-part zonal soil behavior classification by piezocone test (CPTu) can be subdivided into finer categories of soil type. Furthermore, the pile side coefficient (C_se) linking effective cone resistance (q_E = q_t – u₂) to pile unit shaft resistance (f_p = C_se q_E) can be related as a continuous function, rather than just five discrete values. The continuous function for C_se is provided via use of the CPT material index (I_c). A refined definition of the pile toe resistance (q_b = C_te q_E-toe) is made where C_te is also expressed as a continuous function of I_c. A case study is presented to demonstrate the improved assessments of the axial pile capacity via the proposed modifications.

Sustainable design of foundations and structural members requires safe and environmental friendly structure with minimum material use. Piled-raft foundations are commonly used to support heavy structures in soft soil. Traditionally, seismic design of such structure is carried out considering fixity at base level in a soil-pile raft-structure system while pile head is considered to be fixed for design of pile. Major drawback of this fixed base assumption is that it cannot capture soil structure interaction (SSI) effect. Incorporation of SSI may result in increased or decreased transmitted shear to the pile and column as compared to fixed base shear which may lead to unsafe or over-safe pile design. Since natural soil properties vary at different points within geologically distinct layers. As a result, transmitted shear to the pile and column depends on in situ variability of design soil parameters, thus leads to transformation of the whole problem to reliability based SSI design problem. Thus, precise estimation of safety margin is needed for rational and sustainable design of pile. Hence, a probabilistic analysis incorporating SSI is performed in present study to develop insight into the problem for refining the existing design guidelines.

A new procedure is proposed for design of individual drilled shafts in shale at service limit states. The procedure utilizes t-z analyses and adopts the factored strength approach to account for variability and uncertainty in the design method and associated input parameters. The resistance factors used in the procedure were calibrated using a finite-element code to model load transfer in drilled shafts and Monte Carlo simulations. The variability and uncertainty considered for calibration of the resistance factors were derived from full-scale load tests performed on drilled shafts founded in shales in the central United States. The calibrated resistance factors generally range between 0.1 and 0.4, depending upon the uncertainty in the shale uniaxial compressive strength. Such values are substantially less than those commonly used in current practice, but reasonably reflect the collective variability and uncertainty present for design of drilled shafts in shale. The primary appeal of the proposed procedure is that it eliminates the need to design for the service limit state on a case-by-case basis.

Foundation load test databases are needed by researchers in the reliability calibration to develop accurate and economical foundation geotechnical design methods (LRFD implementation), and also can be used by designers to evaluate and improve the geotechnical design for production foundations in their field projects. These databases should include quality, complete, and adequate number of records of data at load test sites. The FHWA developed the deep foundation load test database (DFLTD), which was considered by researchers and State Departments of Transportation (State DOTs) to develop their databases. Presently, just a very small number of reliability-based resistance factors for foundations were developed by AASHTO and State DOTs due to lack of quality foundation load test databases. The public and private highway engineering agencies need to work together to develop local, regional, and national foundation load test databases that cover all the common foundation design and construction conditions encountered in the USA. The goal of this paper is to help these agencies develop and use quality deep foundations load test databases. The paper initially describes the applications of foundation load test databases. Then, it describes the contents, limitation, and distribution of the DFLTD. Finally, the contents and use of other deep foundation load tests databases is described.

This paper outlines the Imperial College Pile (ICP) approach for developing reliable predictions for the axial capacity of driven piles. The ICP’s advantages over traditional design methods have led to widespread use in offshore oil and gas developments. The methods are now playing a critical role in major Northern European offshore wind projects. Hundreds of large steel tubular piles are being driven in the North and Baltic seas and improving design efficiency is crucial to the industry’s economic success. This paper provides an overview of the development of the ICP design methods and summarizes their key features, together with experience-based guidance on their application. Their application is illustrated by reference to the North Sea Borkum West II wind farm, where 40 turbines have been installed on steel tripods founded on large diameter steel piles driven in very dense sands. The paper reports how the significant effects of axial and lateral cyclic loading were addressed for Borkum West II through the ICP design methodology.

A site investigation, pile installation, and pile load testing program were performed at John F. Kennedy International Airport (JFKIA) for the extension of the existing Terminal 4. As part of the site investigation, cone penetration tests were performed to characterize the subsurface conditions. The pile load testing program consisted of dynamic testing by means of the pile driving analyzer (PDA) and full scale static load tests. The results of the cone penetration tests, dynamic and static load tests, and pile driving records were analyzed to form a database of high quality, well-correlated data to inform the models. Characterization of the subsurface conditions at JFKIA and subsequent pile designs have traditionally been based entirely on the results of standard penetration tests or estimated from back-analysis of static load tests. The results of the cone penetration tests were compared to the PDA tests and the results of the static load tests. The results indicate that cone penetration tests can be used to accurately predict capacity and required embedment lengths for the tapered piles. The results of the cone penetration tests and correlation to the results of the PDA testing at EOID were then used to calibrate a one-dimensional wave equation analysis model to allow predictions of drivability and capacity at EOID for different hammer types and energies.

The effect of random variation of material parameters (cohesion) on bearing capacity problem was investigated. Cohesion (c) was considered as a spatially random set of parameters within finite elements. In nature, the neighboring soil elements tend to have some correlations over a distance, which is called correlation length. Both variability of cohesion and correlation length were found to have significant effects on probability of failure. However, most studies in bearing capacity problem considered isotropic condition of correlation length, although soil elements deposit in layers (i.e. correlated more in horizontal than vertical direction). This research also explored anisotropic correlation length and its influence on the design probability of failure. The correlation length (or correlation length ratio), coefficient of variation and the design factor of safety showed inter-correlating effects on the obtained probability of failure.

The behavior of multiple anchor plates embedded in sandy soil has been investigated numerically. Numerical analyses were performed by a series of three-dimensional non-linear finite element analysis by using Plaxis. The effects of the parameters like the horizontal spacing between anchors, the embedment ratio of the anchors, the relative density of sand, and the configuration of anchor plates have been investigated. The results were presented in terms of uplift capacity for one anchor plate and the value of group efficiency for multiple anchor plates. It was clearly noted that the value of group efficiency was approximately 100% with an increase in spacing between the anchors. Based on the FE analysis, it can be concluded that the relative density of sand and the embedment ratio of anchor plates are main parameters affect the uplift capacity of anchor plates.

The paper presents a new method for nonlinear analysis of Euler-Bernoulli beams on soil. The governing differential equations for beam and soil displacements are derived using the principle of virtual work, and these equations are solved using finite element and finite difference methods, respectively. Using the analysis, beam displacements can be obtained very quickly as a nonlinear function of applied loads if the beam and soil geometry and properties are known. The advantage of the method is that it is based on robust continuum theory yet produces results as fast as those produced by the spring models.

In the modern design codes adopting load and resistance factor design (LRFD), the resistance factors for various models for the design of geotechnical systems were calibrated with the load factors that had been determined by structural engineers. Although the consistent performance or risk level was intended for LRFD, the uncertainty remains in the geotechnical design obtained with LRFD, as the variability of input parameters at a given site could be quite different from those variation levels assumed in the calibration of resistance factors. Thus, the question of how likely the completed geotechnical system meets the performance requirement does not vanish even with LRFD. A logical question then is “how can we perform LRFD so that the geotechnical system will remain feasible (i.e., being able to satisfy the performance requirement) in the face of uncertainties.” In this paper, we proposed an approach that integrates the robust design concept with LRFD, termed robust LRFD (R-LRFD) approach, to help solve this problem. We demonstrated this R-LRFD approach with a drilled shaft design example documented in ETC10. Comparison was made between the LRFD solution with that obtained using the proposed R-LRFD approach.

Integral Abutment Bridges (IABs) are jointless bridges and are increasingly being used to eliminate undesirable effects of bridge joints on the long-term performance of bridges. However, the behavior of abutments in an IAB is poorly understood. This paper describes an effort to understand the complex soil-structure interactions occurring in IABs through field performance and numerical modeling. Data from the field monitoring of an existing 64.0 m long, three span IAB with a 10° skew in Oklahoma are presented. Results are presented for a 40-month period of monitoring covering a bridge temperature change of 95 °F. Field measured bridge temperatures agree with the temperature range specified in AASHTO LRFD Bridge Design Specifications. Earth pressures on the abutments induced by thermal loading of bridge are consistent with temperature changes and fairly significant amount of abutment back pressures have been recorded during summer. Recorded abutment pile strains show piles are experiencing bending moments beyond the yield bending moment at shallow depths for seasonal temperature variations. Numerical modeling of this IAB confirms abutment piles have yielded at shallow depths, however, computed bending moments are greater than field measured values. Several factors are attributed to the difference between field measured and computed bending moment values.

Scour around bridge pier is known as one of the most critical causes to bridge failure. Countermeasures suggested by HEC-23 (2009) include riprap, gabions, spurs, guide banks, and so on. The principals of these countermeasures are either mechanically stabilizing the channel bed surface to prevent the development of the scour hole, or reducing the vortex intensity. Streamlining of the piers is a potentially feasible countermeasure to bridge scour by reducing the vortex strength. In this paper, Computational Fluid Dynamics (CFD) models are developed to evaluate the feasibility of streamlining as a countermeasure. Five test cases with different streamlining features are systematically analyzed and compared. It is found that the vertical profile of the pier nose and sidewalls has significant effects on the development of vortex structures around piers. Streamlined pier nose and sidewalls help reduce the downward flow in front of the piers, the vortex extent around the pier and the bed shear stress intensity. If the pier is not aligned with the incoming flow, however, the effectiveness of streamlining as a scour countermeasure may be highly compromised.

This paper presents a particle tracking method to visualize the deformation response of a soft soil due to the insertion of a T-bar penetrometer at shallow embedment depths. The T-bar is a type of full-flow penetrometer commonly used in centrifuge testing and offshore geotechnics to obtain the peak and remolded undrained shear strength profile of soft clay with depth. A series of T-bar penetration tests were conducted in Laponite RD, a transparent soil surrogate representing soft clay, to visualize the resulting deformations and the shallow embedment failure mechanism in the soil along the length of the T-bar during peak shear strength testing. The experimental set-up consisted of a laser-based computer vision capture system; a particle tracking algorithm was utilized to determine the deformation around the T-bar. Results of the experimental study showed a shallow embedment failure mechanism characterized by surface heave, gap formation, and gap closure above the T-bar. Tracked deformations were similar along the length of the bar with no deformation occurring past the axial ends of the bar. The deformations resulting from the particle tracking algorithm are consistent with previous numerical models of T-bar penetration with the exception that gap closure was observed along both the long and short axis of the bar indicating that plane strain may not be applicable at the ends of the bar.

Due to an increasing rate of traffic volume and truckloads in recent years, asphalt binders are often modified with polymers to increase stiffness and sustain excessive heat during hot summer days. However, the cost of polymer-modified binders (PMB) is significantly higher than un-modified binders. Nanoclays, on the other hand, are relatively inexpensive, naturally abundant, and environmentally sustainable, and have favorable intrinsic properties such as nanoscopic size and high surface area. The current study evaluated moisture resistance and healing potential of a commonly used performance grade (PG 64-22) binder modified with different dosages of two selected nanoclay (Cloisite® 15A and Cloisite® 11B) through a surface free energy (SFE) technique. The adhesive energies, an indicator of bond strength, values of nanoclay-modified binders and two selected aggregates (sandstone and limestone) were also evaluated. It is observed that the work of cohesion increases when the asphalt binder is modified with nanoclays, which implies increased healing potential of microcracks. A 4% Cloisite® 15A seems to be effective in maintaining good wetting ability with different aggregates. Cloisite® 15A, consisting of smaller particle size than Cloisite® 11B, is found to be more compatible than Cloisite® 11B.

This paper evaluates cold in-place CIR moisture-density relationships. Phase 1 describes the Mississippi Department of Transportation (MDOT) US-49 CIR project and performs complementary Proctor compaction testing, a key component of MDOT’s US-49 design/construction protocols. Phase 2 evaluates the Superpave Gyratory Compactor (SGC) in place of Proctor compaction as MDOT is interested in its future use. Over 300 SGC specimens were compacted using different materials, gradations, binders, and moisture contents. The key finding is that moisture content had no meaningful effect on dry density in the range where Proctor compaction would detect an optimum moisture content (OMC). Because SGC-compacted dry density appears unrelated to moisture content (within reason), Proctor OMC does not seem as informative for CIR as for soil or crushed stone. Therefore, SGC compaction is recommended, likely at a fixed moisture content, for CIR mixture design.

About 300 million scrap tires are generated each year in Unites States. The improper disposal of these scrap tires has posed serious threat to public health and environmental safety over the last few decades. The objective of this study is to assess the viability of sustainable utilization of scrap tires as ground tire rubber (GTR) to prepare new asphalt rubber (AR) by investigating their rheological and mechanistic properties. AR is reported to provide a longer lasting road surface, reduced road maintenance, reduced noise, and shorten breaking distance. The current study has gathered lessons learned and best practices from prior studies. Toward evaluating the mechanistic performance, three different amounts (10%, 15%, and 20%, by the weight of the binder). GTR have been blended with a base binder (PG 64-22) to prepare AR binder samples though the wet process and their rheological properties were tested in accordance with Superpave test protocols. Viscosity and penetration test results reveal that AR is significantly stiffer and it possesses higher rutting resistance compare to the base binder. Preliminary test data and life cycle cost analysis of a typical pavement section suggest that AR is a viable and sustainable alternative to the commonly used polymers.

Within the pavement industry, there exists a continually growing sustainability emphasis. Cold in-place recycling (CIR) of flexible pavements has some potential sustainability implications but has yet to be soundly established on a large scale or fully characterized in terms of performance. Currently-established design and testing procedures for traditional asphalt provide a logical starting point but should be evaluated and possibly modified to accommodate differences within CIR relative to traditional asphalt (e.g. use of mixing water). This paper’s objective is to evaluate CIR using several available performance tests originally developed for asphalt concrete and assess their ability to characterize CIR, specifically for a diverse array of binding agents. Tests evaluated are the Cantabro durability test, the bending beam rheometer (BBR) mixture beam test, wheel tracking in the Asphalt Pavement Analyzer (APA) and Hamburg Loaded Wheel Tester (HLWT), a loaded wheel fatigue test, and an indirect tensile (IDT) crack characterization test. Based on results of this paper, Cantabro and BBR tests are not recommended, HLWT and loaded wheel fatigue do not appear promising, APA appears promising, and IDT appears promising and should be studied further.

Expansive soil is considered one of the most common causes of pavement distresses. Depending upon the moisture level, expansive soils will experience changes in volume due to moisture fluctuations from seasonal variations. The objective of this research was to evaluate existing repair projects on selected roadways. Those roadways experienced failures in the form of fatigue and rutting in the wheel path, and longitudinal (faulted) cracking including edge cracking. The causes of those failures were mainly linked to high plasticity expansive soil and narrow pavement. The study involved visual survey, field and laboratory testing, surface condition/ride data and structural design calculations for three project sites. The study concluded, from 3-14 years of performance records, that geogrid reinforcement, lime-treated subgrade and cement-treated base were found to be effective treatment options for low-volume roadways where high plasticity expansive soil exists.

Large scale pile tests underpin our basic understanding of foundation behavior for specific boundary conditions and soil types and enable engineers to conduct a performance based design approach. Among several analytical design tools such as Limit Equilibrium Methods, Winkler Method, Elasticity Methods, Hybrid Methods, Closed Form Solutions, FEM, and finite difference analyses, the p-y method has become a popular tool to design and analyze pile foundations subject to lateral loading. Many advances have been made since the American Petroleum Institute (API) sponsored a pioneering large scale research program in the 1960s to mid-70s. However, due to lack of knowledge and familiarity with recent advances, many engineers rely on well-known sources and obtain pile designs that may not be accurate in terms of stiffness and capacities- hence yielding uneconomical pile geometries. This paper reviews recent developments in p-y curve formulations derived from large-scale pile experiments conducted in the last forty years. A summary is presented of studies that target effects such as: (1) pile geometry, (2) head fixities, (3) cyclic loading and strength degradation, and (4) group configurations. A recently developed database of large-scale lateral pile tests is also introduced. The database is a resource that will help practicing geotechnical engineers to obtain accurate and economical pile designs. It contains test data and p-y formulations derived from academic research and tests conducted as part of industry projects.

Premature pavement failure is often associated with loss of support in the subgrade layer, especially in regions with soft subgrade soils. The support provided by the subgrade layer can be quantified in terms of the resilient modulus (M_r), which represents the stiffness of the subgrade under cyclical loading. However, the M_r value of subgrade soils is not constant and varies due to the effects of moisture content and the state of stress. For unsaturated subgrade soils, the impact of moisture variation on the M_r value can be captured through matric suction, which also effects the stress state of unsaturated soils. This study reinforces the relationship between M_r and matric suction for unsaturated soils. M_r values, for four (4) different fine-grained soils representing a range of subgrade soils commonly found in southern Louisiana, were obtained by performing repeated load triaxial tests. Matric suction values were obtained by measuring the Soil Water Characteristic Curves (SWCC) utilizing a combination of techniques, axis-translation and chilled mirror hygrometer, which allowed for representation of the SWCC across the entire range of saturation even for soils with a high Plasticity Index (PI). It was seen that the PI of a soil has an effect on the shape of the SWCC. Matric suction estimates for the M_r specimens were obtained by correlating the degree of saturation of the M_r specimen with the SWCC for a given soil. It was seen that incorporating matric suction in a M_r constitutive model allowed for capturing the effect of moisture variation on the M_r value. However, recognizing that matric suction can be difficult to measure, the impact of moisture variation on the M_r value was also evaluated in terms of changes in the degree of saturation.

Depletion of good quality aggregate sources combined with strict environmental regulations has forced transportation agencies to consistently seek unconventional and sustainable alternatives for pavement construction materials. Accordingly, the Illinois Department of Transportation (IDOT) uses a wide variety of recycled materials for pavement construction platform as well as base/subbase course applications. However, no established design standards are available to govern the design and construction of pavement systems incorporating such recycled materials. This paper presents findings from an ongoing research study at the University of Illinois focused on the performance evaluation of different unconventional aggregates in low volume road base/subbase course applications through accelerated pavement testing (APT). Seven different aggregate materials incorporating different proportions of recycled concrete and reclaimed asphalt pavement materials were used to construct twenty four full-scale pavement test sections. Performance under loading of each pavement section is currently being studied through accelerated pavement testing and periodic rut-depth measurements after different number of load applications. Results from accelerated testing of four such pavement sections are presented in this paper.

The pozzolanic nature of fly ash makes it an excellent material for partial replacement of hydraulic cement in many road construction applications. This paper presents such an application for a specific type of cementitious fly ash from a power generating plant using fluidized bed combustion (FBC) called FBC ash. The Portland cement-FBC ash combination was used in full depth reclamation (FDR) of a low volume road in Pennsylvania. The initial mixture design for FDR was conducted for 100% cement as the chemical stabilizer, optimizing the water and cement contents through an engineered design process. Subsequent to the development of the initial mixture design, 50% of the cement was replaced by FBC ash and density and unconfined compressive strength tests were conducted on the cement-FBC ash blend to determine the impact of this replacement on strength and density. Construction of this cement-FBC ash FDR and the all-cement FDR were conducted successfully. Results from unconfined compressive tests on field cores obtained after construction indicated that specimens obtained from cement-FBC ash sections had slightly higher strength than the all-cement specimens.

This paper presents data and analysis of the measurements from earth pressure cells installed to measure vertical pressures in two trenches during the installation of a vitrified clay pipe (VCP) embedded in Class 5 material (concrete). The trench walls above the Class 5 embedment were temporarily supported with steel plates and hydraulic struts. The installed earth pressure cells measured the vertical pressures induced during the placement of Controlled Low-Strength Material (CLSM) backfill and under subsequent traffic loads. Vertical pressures induced on the top of the concrete-encased pipe by the CLSM backfill were continuously recorded during various stages of trench completion. The measured vertical pressures demonstrate that arching developed between the CLSM and the steel trench plates as the trench was being backfilled. Upon removal of the trench plates, substantial increases in vertical pressures, approximately corresponding to the full unit weight of the slurry, were measured indicating that a complete loss of arching occurred because of the trench plate removal. The combination of loss of arching, high stiffness, and extending the CLSM up to the base of the pavement system causes a significant increase in the loads imparted onto the pipeline from traffic loads. When slurry backfill is used, care must be exercised in estimating pipe loads and developing the construction sequence, particularly the timing of trench plate removal. Additionally, provisions such as placing compacted granular backfill in the upper few feet of the trench, below the pavement system, would likely be helpful in mitigating the magnitude of traffic loads imparted to the top of the pipe.

In late 2013, Maid of the Mist constructed a single winter storage facility along the U.S. shoreline for the storage of floating docks and tour boats operating in the lower Niagara River for both the United States and Canada. Micropiles grouted to rock were originally considered by others for support of the storage facility, which is retained by a cantilever concrete wall. The test borings indicated that the site is underlain by talus over bedrock. Due to the depth of competent rock that was found to be much deeper than anticipated over nearly half of the project site, micropiles were proposed to be grouted into the talus. During construction, substantial grout loss occurred during installation of the test micropiles in the talus deposits, resulting in delays in completion of the test micropiles. To allay the concern over the lengthy construction delay required for installing production micropiles, the design team decided to support the retaining wall on a significantly modified shallow foundation over the talus deposits without any micropiles. This prompted a concern over the overall performance of the retaining wall, given the inherent heterogeneity of the talus deposits. This issue was addressed in the design, and the project moved ahead without micropiles in the talus deposits. The project was successfully completed within construction schedule and below budget, with over 150 micropiles being eliminated. Instrumentation of the wall during and after construction indicated that the wall performs very well with insignificant ground deformations. This paper presents (1) the design logistics of using a conventional retaining wall in lieu of micropiling over the talus deposits, (2) an overview of the construction challenges encountered in the field, and (3) the importance of team work and partnership with contractor for a design-build project.

The Minnesota Department of Transportation (MnDOT) has conducted several driven pile performance monitoring projects to investigate and assess the practical impact of the phenomenon of downdrag and the resulting dragload, often called “negative skin friction” on driven pile design and construction practice. While the current design guidance addressees downdrag and its associated dragload, there has been significant discussion by MnDOT personnel and the engineering community as to when negative skin friction can be expected, how to predict the magnitude of the dragload to be considered in design, and what scenarios, if any, exist when dragload may be safely ignored. This case history paper presents observations from five projects in Minnesota where driven piles were instrumented and monitored over periods of months to years, through construction and initial service, including lessons learned on those projects relative to the downdrag phenomenon. These projects have examined, among other things: the difference in behavior between standard pipe piles relative to Teflon-coated pipe piles; the impact of sleeves placed around stick-up lengths of piling in reducing dragload; the dragload distribution difference between subsurfaces composed of loose sands compared to soft clays; etc. While there is much to consider when dealing with negative skin friction and downdrag, a number of findings have allowed more knowledgeable decisions to be made, resulting in revisions to agency practice. Initial work proved that dragload existed, was measurable and permanent, and the behavior and observed magnitudes appeared consistent with predictions given geotechnical site conditions and structural loading.

Stone retaining walls over a century old are common in the New York Metropolitan area. Some of these walls are dry (no mortar). The 2005 failure of the stone wall along Riverside Drive in New York City blocked the Henry Hudson Parkway in both directions and the reason for failure was attributed to blocked weep holes buildup and of water pressure which in hindsight could have been possible to relieve. Unlike reinforced concrete walls, stone walls (especially dry walls) have no tensile resistance and the modes of failure therefore, are different. Some stone walls are less than 1 m in thickness and owe their stability to rock ledges behind the wall that produces a silo effect. In this paper, published literature on the performance of stone retaining walls is reviewed with respect to stability assessment and mechanical properties of stone walls. Case histories are described illustrating the key issues in assessing the stability of existing stone walls. Methodologies for the stability analysis of existing walls are presented.

Base grouting is becoming more widely promoted in the drilled shaft industry as a means to improve shaft response to load. This paper presents several case histories of full-scale static load tests conducted on adjacent shafts with and without base grouting on projects in various parts of the United States. All tests were performed by Loadtest USA using the Osterberg cell (O-cell) test method. The comparisons yielded some intriguing results. In some cases, the results matched theory quite well and showed improvement to stiffness and/or overall capacity. In other circumstances, this was not the case. These case histories illustrate the need for further load testing and research to better understand how drilled shaft capacity is affected by base grouting, particularly, how the capacity is affected by drilling, base cleaning, and base grouting techniques and quality control in various soil materials. Portions of this article appeared previously in the 7th ICCHGE (Sinnreich and Simpson 2013), and are reproduced with permission.

There are currently no static analysis methods available for estimating the geotechnical resistance of a driven pile in rock. According to the American Association of State Highway and Transportation Officials (AASHTO), the limiting factor for a pile in rock is its structural capacity. The estimation of its structural axial capacity depends strongly on an effective length factor (K) and its unbraced length (L). These parameters significantly depend on its soil confinement along the pile and rock support at its toe, which lead to a large discrepancy between estimated and measured resistances. In this paper, three case studies of completed pile projects in Wyoming are presented to highlight the limited knowledge and challenges pertaining to present design and construction practices of driven piles in rock. Steel H-piles were installed at Burns South, Casper, and Torrington sites in Wyoming. Static analysis method was used to estimate the geotechnical resistances of these piles. Wave Equation Analysis Program (WEAP) and Case Pile Wave Analysis Program (CAPWAP) were used to verify their performances during construction. Structural capacities of these piles were also calculated. The results of the studies show that the static analysis methods and structural analyses yield inconsistent pile resistance estimations. Several recommendations are proposed: (1) develop an analytical method for piles in rock; (2) conduct full-scale load test of piles in rock; (3) characterize rock properties; and (4) develop a relationship of percent pile bracing, soil properties and embedded pile length.

Virginia state highway Route 33 crosses wide marshes and two rivers that join at the peninsula town of West Point and form the York River. The Route 33 project required reconstruction of two former low-level, 2-lane bascule span bridges. One of the reconstructed bridges crosses the Pamunkey River on the West Point peninsula’s west side, and other crosses the Mattaponi River on the east side of the peninsula. Both new river crossing bridges are significantly longer, higher, and wider than the original. The new Pamunkey River bridge includes a higher bascule span that greatly reduces the frequency of openings for river navigation traffic. The new Mattaponi River bridge was constructed high enough to eliminate the former swing-span altogether. Lengthening of the on-land portions of the bridges also allowed the Virginia Department of Transportation to eliminate a disruptive at-grade railroad and street crossings. Together, these improvements have greatly improved flow of highway, river, and railroad traffic, accomplishing this while addressing difficult environmental and geotechnical challenges presented by the river crossings. The project required a mix of foundations and soft ground construction technologies, including 1.68-m (66-in.) diameter prestressed concrete cylinder piles and a variety of smaller square prestressed concrete piles for the bridges, prestressed concrete pile-supported embankments, lightweight aggregate embankment fill, and staged surcharge preloading for the bridge approach embankments.

This paper presents a comparison between the measurements taken from Statnamic Load Test and Conventional Static Load Test on 30-inch square prestressed concrete piles, to verify Statnamic test’s ability to determine pile’s capacity and movements. The data was collected at two New Jersey bridge construction sites, located within proximity to each other. The information presented also includes a brief overview of the Statnamic load test, references project details and provides an evaluation regarding the accuracy of the Statnamic testing method.

The United States Army Corps of Engineers (USACE) manages the Houston Ship Channel dredging operations, required to maintain the flow of barges within the ship channel. Disposing of the dredge materials requires the creation of disposal islands throughout the channel. A levee surrounds each island to contain the dredge material during a storm event, preventing spillage into the ship channel, which would inhibit movement of barges through the channel and shutting down all commerce. In 2009, the USACE led a project to increase the existing levee heights at a number of the islands to increase dredge storage capacity, including the Lost Lake Dredge Material Placement Area (DMPA). Lost Lake’s current levee elevation of EL. +8.2 m (27.0 ft) required a change in grade to EL. +10.9 m (36.0 ft) an increase of 2.7 m (9 ft). During construction, the levee failed several times over a 640.0 m (2,100 ft) stretch. This portion of the levee had a history of failure. The poor soils beneath the levee footprint in this area required stabilization prior to increasing the elevation. The design-build team designed a deep soil mix (DSM) ground improvement program, which included shear panels with overlapping dry soil mix columns, to improve soil beneath the levee with a combined shear strength of 1,000 psf. The panels were constructed at varying depths and lengths depending on the strength of the in situ soil, and were perpendicular to the levee. Dry soil mixing proved to be challenging and required very precise planning and execution because it was located on an island, but also proved to be the most cost effective method due to the remote nature of the work. The levee now performs as designed since raising its elevation to EL. +10.9 m (36.0 ft) after ground improvement.

A seven story residential apartment complex located in the Northbridge area of Perth, Western Australia presented an opportunity for a novel application of Cutter Soil Mix technology (CSM). The development included a two-level basement for car parking which covered the full site area. However, the basement was also required to extend under an existing single story heritage building. A site boundary consisting of a CSM retention system was designed and installed to allow the excavation to proceed to basement level. Two rows of temporary soils anchors or inclined struts were required to achieve this. A CSM support system for the heritage building was also designed and constructed to provide temporary support during excavation and permanent construction works. The brief for the contract works emphasized that it was vital that settlements of the heritage building be kept within strict limits. CSM is a relatively new introduction to the Australian construction market, using a modified trench cutter to mix binder slurry with in situ soils, generally to form cut-off walls, retaining walls and soil improvement works. This project is understood to be first application of the CSM for underpinning work in Australia.

The San Francisco Bay Area Rapid Transit (BART) is a heavy rail transit system connecting San Francisco with other cities in the Bay Area, California. Currently, BART is extending the existing Fremont line approximately 8.7 km south to a new Warm Springs Station. The project is divided into two major contracts, Fremont Central Park Subway (FCPS) and Line, Track, Station and Systems (LTSS). The FCPS contract primarily consisted of the construction of a 1.9 km long cut-and-cover subway box tunnel through challenging ground conditions and under a lake within a major recreational park. As part of the cut-and-cover subway box construction, ground improvements including installation of large diameter jet grout columns and cement deep soil mixing (CDSM) walls. Jet grout columns were installed using the conventional double-fluid system (grout and air) and a new method called the “jetting down” method. To support the subway excavation and to cut off the groundwater, contiguous walls consisting of overlapping CDSM columns were installed. To resist uplift from excess hydrostatic pressure and significant water inflow, a 3 to 7.3-m thick soil cement grout plug was constructed under the subway box. This paper will discuss the challenges during construction of ground improvement for the FCPS project and lessons learned during installation of large diameter jet grout columns and CDSM cut off wall.

The construction of a coastal industrial/ energy facility in Australia involved extensive cut and fill of native residual soil material which was highly variable (generally clayey) in nature. The specification for compacted fill required placement within +2% and -3% of optimum moisture content (OMC) and minimum 90% or 95% relative compaction (RC), modified Proctor compactive effort, depending on location and elevation. The earthwork subcontractor initially had difficulty obtaining consistent compaction results due to the heterogeneity of the residual soil, and there were additional concerns raised regarding swell potential of the compacted fill material. Using a suite of readily-available laboratory tests primarily from an onsite laboratory, the swell potential and strength of laboratory samples at various RCs and moisture contents were measured. These site-specific data were then used to modify and/ or confirm the specification to meet project goals.

A series of cylindrical steel storage tanks with fixed roofs were constructed for expansion of an industrial facility in the Gulf coast of the USA. Tank diameters ranged from approximately 80 to 210 ft (24.4 to 64.0 m). Soils at the site consist of an upper layer of very loose silty sand and soft clay underlain by medium to stiff clay to depth of about 100 ft (30.5 m). For the case being presented, ground improvement using Deep Mixing Method (DMM), popularly known as Cement Deep Soil Mixing (CDSM) was selected as an efficient and cost effective foundation alternative to reduce settlement and achieve an acceptable factor of safety against bearing capacity failure. The design consisted of 8 ft (2.4 m) diameter DMM columns, spaced at 11 ft (3.4 m) center to center and extending to a depth of about 20 ft (6.1 m). Settlement monitoring during hydrotesting was performed via topographical surveys of the ring wall and settlement profilers installed below the tank bottom plate. Vertical inclinometers monitored lateral movements around selected tanks. The data were used to: (1) assess differential settlement since excessive movement could affect the shell, the roof structure and the bottom plate; (2) estimate tank settlement during operation with the aid of hydrotest settlement and (3) observe bearing capacity performance. Performance of the first hydrotested tank is discussed in this paper.

Stone columns have been successfully used for transportation projects across the United States to treat clays, clayey sands, and silty sands for over three decades. However, stone column specific knowledge is generally accessible to only a select group of stone column experts and specialty contractors. Data mining identified numerous case histories that allowed both (1) lessons learned to be compiled from projects that encountered unsatisfactory performance and (2) current settlement estimating methods to be evaluated. The unsatisfactory performance revealed inadequacies in three broad aspects of every project: site investigation, design, and construction monitoring. Current methods of estimating settlements were evaluated with a case history and found the Priebe method to be preferred for routine settlement estimations. Numerical modeling confirmed that the change in stress resulting from the surface load in the layers underlying the stone column reinforced ground can be approximated using a traditional elastic, Boussinesq-type stress distribution.

This paper presents a case history where a steel sheet pile wall was designed and constructed in soft industrial waste as part of an ongoing lake cleanup project. The wall functions as a barrier in a groundwater control system that intercepts impacted groundwater from adjacent legacy industrial sites and prevents it from reaching the lake. It also serves as an earth retaining structure to facilitate excavation and dredging of the industrial waste and impacted lake sediments in front of the wall. The paper discusses the geotechnical design challenges associated with the industrial waste and presents the geotechnical monitoring results of the wall.

During road realignment activities in 2012 on the I-495 Washington Capital Beltway, the Virginia Department of Transportation (VDOT) demolished a MSE wall originally built in 1976. The wall supported traffic on the interstate bridge ramp and was therefore salted each winter as part of VDOT’s standard winter maintenance program; the wall did not have any observable performance issues. Demolition provided an opportunity for researchers at the Federal Highway Administration (FHWA) to investigate the condition of the reinforcement in the 36-year old wall and determine any key factors affecting corrosion related to the design, construction, and maintenance practices. Steel and soil samples were collected from various locations behind the concrete panels along the length of the wall to assess the thickness of the remaining zinc coating on the bar mats. This thickness was analyzed as a function of wall elevation and distance from the bridge abutment face. This paper will describe the corrosion sampling and testing program and present preliminary conclusions on the results.

A multi-phase subsurface investigation (SI) program was performed to provide geo-characterization of a brownfield site for the modernization of a large industrial facility. During the planning and implementation of the sitewide SI, the following factors were considered: (1) facility/structure loading, geometry, and function; (2) site subsurface conditions disclosed by multiple previous SI programs; (3) field testing methodology, (4) new and revised geohazard evaluation criteria; and (5) funding and schedule constraints. The adopted SI program planning and implementation approach/philosophy is described, and the work carried out for one specific structure is used for illustration. The benefits of the SI approach in mitigating subsurface risk in a cost effective manner are demonstrated. Lessons learned that could be useful to practitioners confronted with site geo-characterization for large-scale projects are discussed. The focus of this manuscript is on the geotechnical aspects of the site; environmental considerations are not addressed.

The Frank Lautenberg (FRL) intermodal facility is located in Secaucus, New Jersey. The site is an Intermodal Facility linking NJ Transit rail and bus systems. New Jersey Transit decided to expand the parking facility by about 9,300 m² for additional parking, a traffic circulation area, and pedestrian loading areas with bus canopies and shelters. The construction also required extending a 2440 mm diameter equalizer pipe to beyond the southern limit of the new construction. The area of the improvements was covered by very soft peat, 2.75 to 4 m thick which in turn overlies glacial lake deposits (varved clay) in thicknesses varying from 3.40 to 9.75 m, over till and bedrock. The compressible and weak peat had moisture content about 980%, a dry unit weight near 0.65 kPa, and a shear strength of less than 2.4 kPa. Groundwater levels were generally at the ground surface. The varved clays consisted of mostly a preconsolidated upper crust overlying a softer, normally consolidated clay in few borings where the layer is relatively thick. In order to develop the new area, grade had to be raised at least 1.85 m. Several options were considered to mitigate the projected shear failure of the peat and future settlements as a result of the required fills. Excavation and replacement, and piled foundations were ruled out and the two remaining options were evaluated in detail. The first option, installation of wick drains with preloading was considered problematic as the peat, is very soft and there is potential for failure of the drains themselves and the tight construction schedule. The solution that was adopted is the one believed to be used in building the rail embankment leading to the station: replacement of the very soft soils with boulders. As the soft soil was as thick as 4 m, it was decided that pushing boulders into the muck required assistance by dynamic compaction or more appropriately tamping. The purpose was to push the large boulder material to make contact with the stiffer varved clay below.

The 20-km (12.5-mi) Causeway was constructed in 1956–1959 to replace a wood trestle and maintain rail traffic across the Great Salt Lake. Most of the Causeway consists of rock fill founded on Glauber’s Salt that is underlain by fine-grained lake sediments. To make the project economically feasible, Southern Pacific Railroad (then owner) accepted the risk of designing the Causeway to a factor of safety near 1.0, and Casagrande (1965) described the Causeway as an outstanding example of calculated risk. The original Causeway design considered that safety factors would improve with time as underlying fine-grained sediments gained strength. However, strength gain has not progressed as expected, and miles of the Causeway still have marginal factors of safety. This paper revisits the calculated risk, 55 years after construction, 30 years after a Haley & Aldrich investigation, and over 10 years after a failure along the Causeway. The results of a recent Jacobs Associates geotechnical investigation show that consolidation is not complete and the Glauber’s Salt continues to be important in areas of marginal stability. The results have been used to assist the Union Pacific Railroad (now owner) in developing maintenance plans for the Causeway.

Based on the geology of the area, soil profiles can vary with depth. Construction of drilled piles in these varying soil formations is a challenge and it is important to better quantify the overall behavior of the piles. In this study, 21 load-displacement behavior of ACIP piles in mixed soil profiles were analyzed. The data was collected from full-scale tests performed over the past two decades in Texas. For the Auger cast in place (ACIP) piles, the diameters varied from 356 mm (14 in.) to 610 mm (24 in.) and the length varied from 7.6 m (25 ft) to 35 m (116 ft). The measured pile capacities varied from 756 to 4003 kN (85 to 450 t). The tests were modeled using a non-linear load–displacement relationship. For the ACIP piles in mixed soil profile, the ratio of pile displacement (at 50% of the ultimate capacity) to diameter ratio (₅₀/d) was in the range of 0.1% to 1.8%. The ultimate capacities of the piles were predicted well using the hyperbolic relationship.

Static pile loading tests and high strain dynamic tests were performed to confirm the foundation design for a major expansion to a hospital on the Stanford University campus in Palo Alto, California. The foundations were 610 mm (24 in) diameter continuous flight auger (CFA) piles to be installed at the bottom of a staged excavation. Advantages to the construction schedule made it desirable to execute this test program on piles installed approximately 6.1 m (20 ft) above the final excavation level; however, such an approach was recognized to require accounting for the overburden effect prior to application of the results to design. Therefore, the test piles were instrumented with strain gages and subsequently monitored throughout testing in an effort to allow meaningful interpretation of the overburden effect. Dynamic testing of one of the test piles after excavation to grade suggests that the implemented methodology resulted in a conservative geotechnical design.

The estimation of displacements of augered cast-in-place (ACIP) piles is often based on load transfer models that have been developed for other foundation types, such as drilled shafts or driven piles. Owing to differences in construction procedure from drilled shafts, such as providing continuous support of the drilled cavity and the delivery of grout under pressure, ACIP piles may transfer load from its shaft differently than drilled shafts. This paper describes the development of an empirical t-z model based on static loading tests on instrumented ACIP piles installed in Western Washington. An existing q-z model is paired with the new t-z model to make estimates of load transfer profiles and load–displacement curves of the instrumented piles. The load transfer and load–displacement curves are compared to results derived using the existing O’Neill and Reese (1999) and Vijayvergia (1977) models. In order to make an independent assessment of the model accuracy, comparisons are made to the load–displacement curves of several non-instrumented ACIP piles tested in Western Washington. The region-specific load transfer model is shown to provide more accurate estimates of ACIP pile performance than those existing, and is recommended for ACIP piles constructed in Western Washington.

Augered Cast-in-Place (ACIP) piles are often utilized as a deep foundation solution for certain soil conditions. Rapid production allows for shorter construction schedules while depths and diameters continually increase in scale. Quality assurance of ACIP piles generally relies upon installation monitoring as well as post construction integrity testing. A relatively new testing technique is Thermal Integrity Profiling (TIP). For relatively small diameter ACIP piles, a cable comprised of temperature sensors is attached along the center rebar, and placed in the grout of the ACIP column, such that temperature measurements can be recorded during the cement hydration process. These measurements are then post processed, along with installation records, to assess overall ACIP pile integrity. A project site in Rockport, Indiana utilized over 400 ACIP piles which had integrity analysis performed via TIP. In addition, pulse echo testing and dynamic load testing was performed on a small number of test piles. This paper presents a case study on techniques of TIP instrument installation and data analysis as well as a discussion of recommendations for future use.

A series of pile jacking and driving tests in a plane strain calibration chamber is presented in this paper. The calibration chamber was made of transparent acrylic that allows visualization of the pile installation process. High resolution images were taken while the pile was jacked into confined granular media. Parallel tests were performed in which a drop weight was employed to drive the pile into place. The two installation methods were compared in terms of soil response in the near field. Digital Image Correlation (DIC, aka. PIV) was employed to construct the incremental displacement field during penetration. Test results were used to gain insight into the nature and magnitude of spatial distribution of displacements in the vicinity of a pile as a result of jacking and driving. Evaluation of the displacement fields revealed that jacking results in lower lateral displacements compared to driving.

This paper describes the first experimental research effort conducted in the United States on load distributive compressive anchors (LDCA). LDCAs were developed and first used in South Korea. The research effort was aimed at developing design, installation, and testing criteria suitable for U.S. practices. This paper presents a summary of the research findings that will serve as reference for use by practitioners when selecting, designing, installing, and testing LDCAs. The paper describes the process used for removing the anchors after installation, which achieved a 100% success rate during the tests. Since the completion of the research report, LDCAs have been used successfully for several projects in the U.S. Some of these projects include Hudsons Yards in Manhattan and Maryland Public Health Building in Baltimore, where LDCAs were implemented successfully. The authors recommend that similar research efforts be undertaken in other geological formations within the potential geographical market area to obtain average ultimate bond strengths for preliminary design, and to advance the understanding of this innovative technology.

Sheet piles are widely used for earth retaining and water cut-off purposes. Construction under an existing low bridge girder with a relatively high water level has to deal with very low head room, often necessitating costly dismantling and reconstruction of the superstructure or otherwise temporary detouring. A new press-in sheet pile driver is developed to work in only 1.0 m (3.3 ft) head room to avoid such costly countermeasures. In order to realize this challenging goal, the following new techniques are developed and combined:

Microbial induced carbonate precipitation (MICP) is considered an environmental-friendly soil improvement technique and laboratory studies have demonstrated that it can improve the soil shear strength and stiffness. In addition to the lab-scale tests, a limited number of field scale tests have been performed for mass soil stabilization using MICP. However, the improvement of soil at the field-scale has encountered practical difficulties including bio-clogging and heterogeneity of CaCO₃ precipitation, which limits the precipitated CaCO₃ to a small zone around the injection points. This paper focuses on verifying limited zone improvement surrounding permeable piles to enhance their axial capacity and improvement of the soil–pile interaction using MICP. To verify this, two pervious concrete pile tests subjected to uplift loading were conducted with and without MICP treatment. The same pervious concrete pile was used and embedded in a small soil box filled with poorly graded sand for the tests. For the MICP-treated test, the treatment solution was percolated from the top of the pile to induce CaCO₃ precipitation at the soil–pile interface. After the treatment, the pile was subjected to an increasing uplift load. The load and displacement at the pile top were measured and the responses from the MICP-treated and untreated tests are compared in this paper.

A suction caisson is installed by applying suction inside the caisson to create a downward net force to sink the caisson into soil. However, the applied suction pressure will also result in formation of a soil plug. This is particularly the case when the soil is soft and when the caisson wall is thick. In this paper, the results of several model tests carried out using a 1 m in diameter consolidation tank and 205 mm in diameter concrete caisson are reported to study the installation process of a suction caisson in clay. Different caissons and different soil conditions were used. Thus study show that the caisson wall thickness and the properties of clay are two major factors affecting the formation of soil plug which in turn, affects the installation of suction caisson.

The effectiveness of torpedo anchor as offshore foundation was investigated through numerical modeling. The installation was modeled in an explicit dynamics code, capable of simulating large strain deformation and matched favorably with data from field installations. Anchor tilt during installation was simulated through artificial columns of soil, resulting in movements that closely match those reported from field tests. Results from anchors with and without fins were compared to assess the potential benefits of fins. Excess pore water pressure generated during anchor installation was included in analyses to accurately characterize the shear strength properties of the soil in the immediate vicinity of an anchor. Pullout capacity was significantly reduced due to increase in excess pore water pressure (and consequent reduction in shear strength). The pullout capacity increased, following dissipation of excess pore water pressure. Results of pullout capacity with and without consolidation matched field results for corresponding conditions.

Scour removes soil around piles and changes the behavior of piles laterally loaded from flow wave, earthquake, and wind. Limited experimental studies have been conducted so far on the behavior of laterally loaded piles under a scoured condition. To evaluate their behavior under a scoured condition, model tests of laterally loaded piles were conducted in this study to investigate the effect of the scour depth. The scour depth, which was represented as the eccentricity between the sand surface and the point where the lateral loads act, was changed from 0 to 500 mm in 100-mm increments and an experiment was conducted for each scour depth. A horizontal scour surface was assumed and no scour slope was considered in this study. Pile failure was defined when the lateral displacement at the point where the lateral load was applied reached 20% the diameter of the pile. The ultimate lateral loads obtained at the failure of the tested pile were close to those calculated using Broms’ method for laterally loaded piles without scour. This comparison indicates that Broms’ method is valid for calculating the ultimate lateral load of a pile under a horizontally scoured condition. Furthermore, the results showed that when the scour depth was increased, the load required to reach failure of the pile decreased significantly.

Pile installation affects the soil-pile interaction and influences the pile behaviors under different loading conditions. Most studies in the literature focus on analytical methods to evaluate the effects of pile installation. Few researches have used experimental approaches to investigate the pile installation effects, especially for piles under lateral load. This research focuses on experimentally investigating the effects of pile installation on the response of pile under vertical and lateral loads. Using the Soil-Structure Interaction (SSI) facility, four laboratory-scale tests have been performed (two vertical load tests and two lateral load tests). The piles were made of pervious concrete with a diameter of 102 mm (4 in). The two piles in vertical load tests have same embedded length of 1,219 mm (48 in) and piles for lateral load test have embedded length of 1,321 mm (52 in). Two installation methods (referred to as precast and installed) were used as part of the experimental program. Precast piles were prefabricated and the soil was placed around them. Installed piles were constructed using a specially designed mandrel system. The load and displacement were measured during the tests. The load-displacement relationships of pervious concrete pile are compared and the effects of the installation method on pile behavior are discussed in this paper.

Significant insights into the characteristics and role of interfaces in geotechnical systems have been developed over the past three decades. In particular, interfaces between soils and man-made inclusions represent an opportunity to develop both new foundation systems as well as analysis procedures to predict their performance. This paper presents a summary of experimental insights that have been developed and their implications on the design of deep foundation systems. These studies examined the role of surface roughness in interface shear behavior, including the influence of “random” versus “structured” roughness patterns that can significantly affect the strength of interfaces. Furthermore, the effects of normal stress and relative hardness are revisited. The opportunity to impact foundation performance based on these insights is discussed.

The behavior of three shallow, drilled, cast-in-place and backfilled concrete pedestal foundations installed in clay and tested in axial uplift was investigated. The pedestals had a base diameter of 2 ft and a shaft diameter of 10 in. and were installed to a depth of 6 ft in a stiff clay fill. Initially, native soil excavated from the holes was used for the backfill but was placed using different compactive effort to give a wide range of construction quality that might be encountered in practice. After initial uplift load tests were completed, the clay backfill was removed and a well-graded sand backfill was placed, again at different compactive effort to evaluate the influence of both backfill type and quality on behavior. The results demonstrate that backfill placement has a pronounced effect on the load-displacement behavior and ultimate capacity of shallow pedestal foundations in uplift.

The foundations for most transmission line structures constructed in North America today are drilled shafts. However, drilled shafts are not always a suitable foundation choice. This paper details one example where helical piles were used as the foundation at select tower locations on the XCEL Energy Stinson-Bayfront Line 3315 32.1 Mile Re-Build 115 kV transmission line project. The structures were steel H-Frames, made by Thomas & Betts Meyer. The tangent structures were specified as direct embedded, and the running angle and dead-end structures were either helical piles or drilled shafts. The line is located in a remote area of northwest Wisconsin near Duluth, MN. Helical piles were used at tower locations with poor road access, and in areas considered environmentally sensitive where large vehicles would destroy the landscape and vegetation. Xcel, Hubbell / CHANCE, and Thomas & Betts teamed together to design this project. Xcel energy produced the load and design drawings, Thomas & Betts designed the H-Frame Pole structures and the pile transition connections, and Hubbell / CHANCE designed the helical pile foundations. Prior to line construction, full-scale load tests of the helical pile / connection were performed at the Thomas and Betts structure test facility located in Hager City, Wisconsin. The running angle and dead-end pile and transition systems were successfully loaded and tested to values that meet or exceed the ultimate design structure ground-line reactions. These results are presented. The piles, tested together in a multi-pile group, were subjected to a combination of axial tension, compression, and lateral shear. In addition, four full-scale load tests were conducted on the line right-of-way at the actual tower locations. The tests consisted of pile penetration tests, axial tension, and lateral shear tests. These test results are compared to the theoretical capacity of the piles based on site soil type and strength. The results of the tests allowed the helical pile design to be adjusted prior to start of construction to provide the contractor with minimum depth and installation torque requirements.

Hubbell Power Systems, Inc./CHANCE^®, in conjunction with Sailors Engineering, Inc. has updated its Helical Design Capacity Software. This latest version, “HeliCAP^® v2.0”, is a state-of-the-art helical anchor and pile capacity program designed to operate in the Microsoft^® environment. The program calculates the tension and compression capacity along with the frictional capacity, if applicable, of helical anchors and piles using design theories and methods adopted by the engineering staff at Hubbell Power Systems, Inc. This paper details the current state of practice employed by the software in the design methods and installation methodologies of helical anchors and piles.

The lateral performance of large-capacity helical piles is of significant interest because they can offer an efficient alternative to conventional piling systems in many applications. This paper presents the results of two field lateral load tests conducted on 6.0 m and 9.0 m large-capacity helical piles installed in cohesive soil. The test piles were close-ended steel shafts with outer shaft diameter of 324 mm. The piles were double-helix with helix diameter of 610 mm and inter-helix spacing of 1.5 times the helix diameter. The subsurface soil properties at the test site were determined using field and laboratory testing methods. The piles were load tested twice: two weeks and nine months after installation. The load-deflection curves were analyzed and the soil moduli of subgrade reaction were back-calculated to better understand the behavior of the test piles and the effect of pile installation on soil disturbance.

Information regarding the load transfer of micropiles during construction loading has not been reported in the literature. The instrumented micropile foundation system reported herein was for Bridge No. 2 of the Foothills Parkway in eastern Tennessee completed in December of 2012. Vibrating wire strain gages were installed at select locations along the micropiles within two of the pile groups. Two strain gages were installed in the bond zone and the remainder near the top and middle of the cased length. Subsurface conditions consisted of medium dense to very dense sand and gravel with varying amounts of silt and clay overlaying conglomerate bedrock. The bond zone of the micropiles was installed within the bedrock strata and the dramatic dipping of the top of rock impacted the length of the micropiles and load transfer. Data was collected from the array of strain gages, such that each set of data corresponded to a different bridge construction stage. Monitoring during construction loading indicated that the variable pile lengths that were necessary because of the geologic setting resulted in load concentration on the shorter piles within the pile groups. Based on the strain data measured along the entire length of the micropiles, load transfer occurred within the bond zone, but significant load was also transferred along the cased length. All the measured loads were well below the structural capacity for the piles.

Two new pusher furnaces were installed as part of an expansion to an aluminum facility in Alcoa, Tennessee. These pusher furnaces pre-heat ingots of aluminum prior to rolling into can sheets for beverage containers. The two $20M furnaces replaced 70 individual preheat furnaces of 1950s vintage with a streamlined automated process in a relatively small but heavily loaded footprint. As may be expected, the pusher furnace was very heavy and would be subjected to a wide variety of loading conditions with tight deflection requirements. The subsurface conditions consisted of clay overlying pinnacled limestone. Rock-socketed micropiles were selected as the foundation considering the performance requirements and the karst conditions including the potential for sinkholes, soft soils, and differential depth to bedrock. These challenges justified an innovative approach where the pusher furnace and foundation were modeled using FLAC3D. The FLAC3D model was incrementally updated during production installation to ensure that the computed displacements would be within the project criteria.

An investigation into the load-settlement behavior of two drilled shafts, founded in shale, is presented. The motivation for this research is to advance the understanding on how drilled shafts react under loading in stiff clays and shales. The objective of this study is to improve the understanding of axial capacities for rock-socketed shafts in hard clays and shales. In order to achieve this objective, the research team measured the strengths within the subsurface material at the test site, estimated the unit side shear and unit end bearing of the shale-shaft interaction by running two axial load tests using the patented Osterberg-Cell (O-Cell) loading technique, and compared the results to the current design methods that are used to predict the axial capacity of drilled shafts. The results of the study concluded that the current methods for estimating unit end bearing developed by the Texas Department of Transportation (TxDOT) and the Federal Highway Administration (FHWA) provide fairly accurate predictions when compared to the measured information However, it was discovered that the measured ultimate side resistance steadily decreased nearing the tip of the shaft. A limited amount of information is currently available for load tests performed in soils with Texas Cone Penetration (TCP) values harder than 2-in per 100 blows. The results presented herein demonstrate the effectiveness of the current design methods for drilled shafts and the non-uniformity of side resistance within one- to two-diameters of the shaft tip.

The Horseshoe project is a $818 million design-build project intended to reconstruct highway infrastructure through the middle of downtown Dallas and greatly improve traffic flow. A new signature bridge, the Margaret McDermott Bridge over I-30, is the centerpiece of this project. The bridge will provide separate eastbound and westbound pedestrian and bicycle access in and around downtown Dallas. Construction of the foundation for the bridge began in 2013 and included drilled shafts socketed into shale. Most notable were 48-in. diameter shafts installed on a 20 degree batter, using double walled sectional casing, oscillated down to bearing. These shafts were 19 to 25 m (63 to 83 ft) long and socketed approximately 8.5 m (28 ft) into sound and continuous shale. Installation of the battered shafts required special planning and unique field techniques to guarantee a suitable finished product. This case provides an important addition to the field data on installation of drilled shafts on a significant batter, a rarely used but attractive solution to a need for lateral load capacity, an increasingly critical requirement in seismically active zones.

Caliche is a cemented deposit of calcium carbonate that occurs in arid regions. The bonding between caliche layers and the shaft concrete is very strong and prevents slippage resulting in the shaft-caliche system to act monolithically. The presence of caliche layers in the soil profile alters the traditional design and analysis method of drilled shaft foundations. Thus, the typical design methodologies used to assess ultimate skin friction may not be applicable to drilled shafts analysis and design in caliche. In this paper, a new approach is introduced for the design of drilled shafts in soil profiles with intermediate caliche layers. In this approach, caliche is assumed to be a continuous plate with significant bending capacity. A case study is modeled with the commercially available finite element software PLAXIS 2D to simulate the results of the o-cell tests. Model results are compared to the o-cell test results in Las Vegas. The monolithic behavior of the deep foundation system results in limited slippage between the shaft and soil and caliche layers. Therefore, the soil layers do not experience any failure during the loading stages. The limited slippage of the soil and caliche layers endorses the monolith behavior hypothesis in soil profiles containing caliche. Moreover, the monolith behavior of shaft-caliche system requires the caliche layers to be the major load carrying element in the system.

A numerical simulation was conducted using FLAC3D to investigate the interaction between the drilled shaft and the MSE wall under lateral cyclic loading that are often encountered from bridges, traffic signs, and sound walls. The drilled shaft was built within the reinforced zone of an MSE wall and loaded toward the MSE wall under force-control mode. An elastoplastic constitutive model, able to consider shear and compression hardening, was selected for the backfill material. The MSE wall facing was simulated by discrete blocks which interacted with each other by friction. The selected constitutive model was calibrated by triaxial test data. Thereafter, the numerical modeling was conducted to simulate a published full-scale field study on the interaction between the drilled shaft and the MSE wall. It was found the developed numerical model can well represent the loading–unloading behavior of the drilled shaft and the MSE wall. As the drilled shaft was laterally loaded to a large deflection, only small percentage of the deflection could recover when the load was removed. As to the MSE wall, nearly all the deformations induced were not recoverable. It was suggested the numerical model be further improved by accounting for the separation between the MSE wall facing blocks.

In advance of conducting drilled-shaft load testing for a highway interchange in Las Vegas, Nevada, the site investigations have included borehole-based soil sampling and logging, standard penetration testing, and both surface-based and downhole seismic testing. Sediments in the area tend to be dense, deep, and sporadically carbonate-cemented. Locally measured velocities are significantly higher than global expectations for the same sediment types. The measured shear-wave velocity profiles fit local expectations in the dry zone (the upper 14 m) and in the presence of secondary carbonate cementation. For wet, uncemented media, velocities are closer to global-reference velocities. Compression-wave velocities indicate depth to moist soil, which reaches well above the observed groundwater table. Correlation of shear-wave velocity to blow count is weak. The measurements will be compared with data from O-Cell™ (Osterberg method) load tests of co-located drilled shafts, with the end goal of improving abilities to predict the capacity of drilled shafts in the Las Vegas area using site characteristics that are readily measured in situ.

The load-displacement response of drilled shafts has been shown to improve with application of pressurized grout to the shaft tip after construction (post-grouting). The pressurized grout applies a bi-directional force at the shaft tip during grouting, which results in upward movement of the shaft and downward movement of the soil beneath the tip. Displacements resulting from the bi-directional force increase the side resistance that can be mobilized and decrease the tip resistance that can be mobilized for subsequent top-down loading. This re-distribution of resistance, referred to as “pre-mobilization”, results in a “stiffer” load-displacement response to top-down loading compared to a similar ungrouted shaft but results in no change to the ultimate shaft resistance. Post-grouting may also produce an increase in the ultimate tip resistance by improving the ground beneath the shaft tip via mechanisms that include densification, tip enlargement, and grout permeation. A 1-D finite element model with capabilities for predicting the improvement due to pre-mobilization was used isolate contributions from pre-mobilization and ground improvement for load test measurements on similar post-grouted and conventional shafts at a representative site. Back-calculated values for unit tip resistance are compared to quantify the improved performance that can be attributed to pre-mobilization and ground improvement, respectively.

A study to assess the extent of corrosion on existing foundation piles was conducted for the Girard Avenue Bridge during the I-95 Section Girard Interchange Ramps (GIR) roadway improvement project in Philadelphia, Pennsylvania. The bridge was built in the early 1970s and carries roadway traffic and a historic trolley line over interchange ramps. A review of the existing borings in the project area revealed that the upper overburden soils consist of highly variable cinder-ash fill material, which is at the approximate same elevation as the groundwater. Due to the known corrosive nature of the cinder-ash fill material, corrosion of the steel pile section was suspected in this zone. Corrosion evaluation criteria recommended by several transportation authorities were reviewed during the process, as well as published historic corrosion rates from several sources. To supplement this data, a pile from the existing structure was extracted to allow for direct measurements of section loss. Extracted pile measurements, which showed up to 12% loss of original section, indicated that the critical zone for corrosion was located within the upper fill strata and the groundwater fluctuation zone. Soils obtained from the surface of the extracted pile were tested for soil index properties, pH, sulfate content, chloride content, moisture content, and resistivity. Corrosion rates based on the actual pile service period of 34 years were used to determine the reduced axial and lateral capacities of the existing piles. New piles with sacrificial section area and widened footings were proposed to strengthen the existing substructures. The paper presents the results of the pile extraction study, compares the observed deterioration against the design values, and provides recommendations for future projects with similar design challenges.

Rock-socketed piles are used to transfer through shaft and base resistances the loads from a superstructure to competent rock layers. In many situations, rock-socketed piles are expected to behave linear elastically under working loads. In this paper, we present an elastic analysis that applies to piles with circular cross sections installed in rock layers. The analysis follows from the solution of the differential equations governing the displacements of the pile-rock system obtained using variational principles. The input parameters needed for the analysis are the pile geometry and the elastic constants of the rock and pile. A parametric study is used to illustrate the most important factors that need to be considered in the design of rock-socketed piles.

After piles are driven into the soil, significant variations of pile resistance typically occur with time. When a pile’s axial resistance increases with time after installation, the increased amount of axial resistance is referred to as set-up. Incorporating the amount of increased axial resistance into the overall design of driven pile foundation systems of structures can potentially reduce sizes of elements, ultimately reducing cost. For over 25 years, the Alabama Department of Transportation (ALDOT) has been collecting pile installation and restrike data during the impact of a pile-driving hammer with Pile Driving Analyzers (PDA) to estimate the axial resistance of driven piles at the end of the initial driving (EOID) process as well as at various time periods after EOID. ALDOT is interested in organizing and evaluating the dynamic testing data to aid in more-efficient and cost-effective pile foundation designs. This research examines time-dependent changes in total, shaft, and toe resistances for 27 axially loaded driven test piles (concrete and H-piles) in Alabama soils using dynamic testing. Researchers filtered through this PDA data, and further analyzed the usable PDA data with an automatic signal matching program (iCAP) to improve the resistance estimates. This data is being utilized to estimate trends of set-up in various locations throughout the state. An ArcMap of Alabama was created using GIS software to display and explore information, data, and results for each pile testing site. This paper provides a summary of the process to analyze pile load tests, organize the data in a GIS system, and then utilize the information to produce trends and draw conclusions on improving the overall testing and design procedures for the state of Alabama.

Foundation support cost is a normalized parameter that permits the relative cost-effectiveness of viable foundation design options to be evaluated, thereby allowing designers to include cost among other decision parameters. Support costs related to driven-pile design have several components: piles, caps, and construction-control methods, the sum of which is total support cost. Two bases for pile support cost are presented and defined: available support, and utilized support. Data indicates that higher-allowable-load piles tend to have lower pile support costs based on available support; two explanations for this relationship are offered. Design efficiency and cost effectiveness should be evaluated using support cost based on utilized support, which provides an indication of how well allowable pile loads match structure design loads. It is demonstrated that higher-allowable-load piles also result in lower pile cap support costs. The effect of allowable pile loads on pile-supported mats and foundation walls is discussed. Construction-control methods affect design and construction in a number of ways, and their support costs alone may not indicate the most-cost-effective construction-control method. Construction-control methods’ effects on other costs, such as piles and caps, should be evaluated using total foundation support cost. An example total foundation support cost determination for a number of pile design options illustrates the approach.

The I-40/I-240 Interchange Improvement Project includes the construction of a four-level interchange that will improve the eastbound and westbound traffic on Interstates I-40 and I-240 in Memphis, Tennessee. The new interchange will include two flyover ramps that will extend up to 25 m (80 ft) above roadway level and will be supported on pre-stressed concrete and steel pipe piles. The project was designed using Load and Resistance Factor Design (LRFD) and uses multiple-stage dynamic testing for the design and construction of pile foundations. Several methods for predicting long-term pile resistance were evaluated and recommendations for using the driving information to evaluate pile resistance are presented.

A design-phase pile load test program has been performed to study the constructability and design parameters for large-diameter steel pipe piles for the proposed Kentucky Lake Bridge as part of the US68/KY 80 Bridge over Kentucky Lake project in Marshall and Trigg Counties, Kentucky. The pile load test program included a 26.7-MN (6000-kip) static axial pile load test, 26.7- and 37.8-MN (6000- and 8500-kip) axial pseudo-static pile load tests, a 1.87 MN (420-kip) lateral pseudo-static pile load test and dynamic pile testing on six large-diameter pipe piles in difficult soil conditions. The pile load test program confirmed that the proposed 1.22- and 1.83-meter-diameter (48- and 72-inch-diameter) steel pipe piles with wall thicknesses ranging from 25 to 51 mm (1 to 2 in.) could be installed to the anticipated target nominal resistances and respective elevations at the site using a Menck MHU800S hydraulic hammer. The pile load test program indicated that the proposed steel constrictor plates should be installed within the pipe piles to increase bearing resistance, and helped the design team to gather information regarding viable design of the constrictor plates, how to locate the constrictor plates relative to the pile tip location, and in what soil strata the constrictor plates should bear within to mobilize additional bearing resistance in the pile design. Axial static and pseudo-static pile load testing indicated that the skin resistance values used in the pile design phase were valid and likely somewhat conservative and indicated that the 1.22-meter-diameter (48-inch-diameter) piles were more likely to achieve a plugged condition.

At an offshore site along the Red Sea coast of Saudi Arabia, marine structures were supported on tubular steel piles driven into coral and coral contaminated sands and silts. Surprises and disappointments faced during the installation of the piled foundation were, to a large measure, due to inappropriate design methodology and absence of proper soil information. The paper describes the design evolution process, highlights the pile test program conducted to verify design parameters, and amplifies the need to prepare for worst possible scenario when coral deposits are encountered. Despite corrections made to the design, based on site-specific insitu parameters (skin friction, end bearing) perceived from load tests conducted on site; the final design adopted overestimated capacities in over 50% of total piles driven. The paper describes the changes introduced to the design during the execution of the project, highlights the pile test program conducted to verify the design, and compares pile design penetration with actual penetration depth. The unpredictable and erratic pile behavior observed, ascertains the need for more appropriate pile design and installation guidelines for driven piles in coral and coral contaminated formations.

Energy formulas have historically been used to estimate capacity for driven piles. Some engineers still rely on them today and researchers attempt to refine the safety factors or resistance factors to allow a more economic result. However, energy formulas make broad assumptions about “average hammer performance” that cannot always be properly accounted for during installation and thus leave themselves open to gross inaccuracies on any “individual project”, and therefore significant risk. Additionally, since common energy formulas do not model the driving system or pile or soil, observing hammer stroke and blow count is not sufficient to guarantee a specific capacity has been achieved on an individual project. It has been well documented by measurements that supposedly similarly rated hammers can transfer significantly different energies to the pile. Using the wave equation analysis to model these vastly different hammer system efficiencies, the resulting variance on calculated capacity from commonly used energy formulas is investigated and presented. Set-up assumptions contribute to further inaccuracies.

Due to the presence of soft saturated cohesive soils in New Orleans and vicinity, most civil engineering structures are supported on deep foundations, consisting of timber piles, precast concrete piles, open or closed end pipe piles, or steel H-piles. The piles at a project site derive their load carrying capacity from (a) “skin friction” along their embedded lengths and (b) “end bearing” when tipped firmly into dense sand or stiff clays. The piles are generally driven in the ground using pile-driving rigs equipped with (a) impact hammer or (b) vibratory equipment. Impact hammers drive the pile by inducing impact on the pile with a falling ram which moves the pile incrementally into the ground. Conversely, a vibratory system installs pile into the ground by applying a rapidly alternating force to the pile using rotating eccentric weights. Impact hammers produce vibration to the ground which can be detrimental to a nearby structure. Consequently, vibratory system has gained popularity in installing large number of pile types. However, the long term effects of vibratory system on soil-pile interaction and pile setup is not properly understood. The main objectives of this research study were to evaluate the set-up phenomenon for four different steel piles driven in soft clay formation in southeast Louisiana using impact hammer and vibratory pile driving system. This paper presents the results of several dynamic load tests performed on these piles over a period of several weeks and summarizes the effects of installation procedure on pile capacity gain.

Large open-ended pipe piles are widely used in offshore foundations. These piles, when properly constructed, offer superior load carrying capability compared to traditional ones. As they can be driven into the ground, there is no need to construct a cofferdam as required for smaller piles in a river or a lake. The savings in the construction cost and schedule can be substantial. The use of large open-ended pipe piles in the transportation project at a few states produced satisfactory results. As most experience with large diameter pipe piles are gained in the offshore industry, the existing knowledge on this type of foundation is rather limited. Formation of soil plug is very important for the bearing capacity of this type of foundation to be mobilized. This paper performed DEM simulations to study the soil plugging mechanism inside the large diameter pipe piles. The advantage of DEM is that it can holistically simulate the interactions between soil particles as well as between soil particles and pipe pile. The results are compared against that predicted by analytical model. A sensitivity study was performed on the effects of factors such as soil column length, pile internal diameter, particle size, friction coefficient of interface between soil and pile, etc. These offers insight on the formation mechanisms of soil plugs inside the large diameter pipe piles.

In most soils, driven H-Piles are generally considered as small displacement piles, that is, the volume of soil displaced during installation is generally small. In most soils the installation of H-Piles likely progresses without significant plugging and the pile advances giving full contact of soil along the web and between the flanges. Very little is known about the tension behavior of H-Piles in these soils. In order to evaluate the uplift capacity for use as foundations for solar panels arrays, tension tests were performed on driven H-Piles at six different test sites. The embedded lengths of the piles varied from 2.4 to 3 m (8 to 10 ft.). The sites consisted of a range of soils, from uniform clean medium sand, silty fine sand and silty clay and included both saturated and unsaturated site conditions. Short term tension tests (1 day and 7 day) to failure were conducted at each site. Examples of the installation driving records are also shown. The unit side resistance of the piles was evaluated assuming both full soil movement (plugged) and no soil movement (unplugged) during loading for each test. It is suggested that the unit side resistance may relate to the Effective Area Ratio of the piles.

Results of axial tension (uplift) tests on driven open-end pipe piles and H-Piles with difference surface coatings are presented. Piles included plain steel, galvanized steel and piles coated with Slickcoat, a silicone epoxy surface coating. Open-end pipe piles with outside diameters of 2.875 in. and 4.5 in. and H-piles consisting of standard steel W6x9 sections were evaluated. Piles were installed using a simple gravity drop hammer. Uplift tests were conducted at four sites consisting of both clay and sand to evaluate the influence of surface coating on the short-term behavior and long-term behavior. Short-term tests were performed seven to ten days after driving; long-term tests were performed on the same piles 200 to 400 days after driving. Axial tension tests were performed to failure for each pile. A comparison of the installation driving records is presented which shows a similarity in driving resistance for the different surface coatings. Load tests are also presented and show that the Slickcoat coated piles gave a substantial decrease in shaft resistance for both short-term and long-term behavior as compared with plain or galvanized piles.

The effect of demolition of support system used for deep excavation construction on surrounding structures may be inadvertently ignored by design engineers. However, structures adjacent to deep excavation construction may have stringent requirement on allowable deformation, hence it is important to study the potential deformations in adjacent structures to avoid irretrievable damage. This paper presents a case study involving the demolition of the deep excavation support system constructed for Shenzhen Ping-An Financial Center (SPFC) building (the tallest building in China when completed in 2015) on the adjacent operational metro line. An operational metro line exists along the north side of the deep excavation location, and the distance between the entrance of metro station and the deep excavation is only 5.6 m. In this study, numerical modeling approach is used to evaluate the deformation of metro line during the demolition of the deep excavation support system. Site construction observations and initial monitoring data were used to calibrate and verify the model results. The results show that the high stiffness of the metro station interdicts the displacement transfer induced by the demolition of the deep excavation. Based on the comparisons with the monitoring data, numerical analysis results are found to be reliable and they helped to evaluate the potential deformation of the adjacent metro line and provide guidance on construction sequences.

Performance of a single pile subjected to lateral loads was evaluated in a centrifuge experiment. The pile was embedded partly in a soft clay layer overlying a dense sand layer. A portion of the soft clay near the ground surface was improved with cement. Experimental results were used to extract the p-y curves for the cement-improved soft clay and these curves were compared with the curves obtained from the unimproved soil and the curves found in literature. The experimentally extracted p-y curves reflected the observed cracking pattern in the improved zone. Although the theory assumes that the p-y curve at a given depth is entirely controlled by soil at that depth, influence of adjacent soil layers were observed on the p-y curves.

This paper presents a full scale test on a pile group as part of a study on the lateral behavior of groups of piles subjected to impact loads. In recent years, pile groups have been installed as an efficient system to protect structures such as bridge piers, offshore platforms and significant buildings against extreme horizontal loads from ships or vehicles. There has been a crucial need to design such impact resisting structures embedded in soils. One of the most effective tools to understand the soil behavior during impacts is a full scale crash test. These tests are rare as they are expensive and difficult to run. This paper presents part of a comprehensive study on a group of four piles embedded 2 m in hard clay, connected together with two beams, and designed to arrest a 2,300 kg pickup truck with an approaching velocity of 100 km/h. In order to monitor the behavior of the piles and beams, the instrumentation included accelerometers on the truck, strain gages on the piles and high speed cameras for displacement. Such full scale tests can provide valuable data for calibration of analytical or numerical models. The details of the full scale test along with the measured response are presented.

In this study, behavior of a 3×3 pile group under lateral loading in sand is investigated by means of numerical modeling. A three-dimensional finite element model was developed using the ABAQUS software to simulate the behavior of steel pipe piles and soil. In this model, the behavior of the soil is described using an elastic-plastic constitutive model while the piles were treated as elastic materials. P-multipliers were developed for each row of the pile groups. Values of 0.78, 0.40, and 0.38 were calculated for a 3×3 free-headed pile group with 3D spacing in the both directions. Piles spacing and piles head conditions effects on the group interaction and consequently p-multipliers have been studied. It has been resulted that piles spacing in a group is an important parameter affecting the piles behavior under lateral loading, however, the piles head condition does not have a considerable effect on the values of p-multipliers.

During pile installation, the stresses and void ratios in the surrounding soils change significantly, creating large strains, soil distortion and excess porewater pressures. This makes the numerical modeling of pile installation process using finite element (FE) method a challenging task. In this paper, the pile installation process and the subsequent consolidation and load tests conducted at different times after end of driving were modeled for the Bayou Laccassine Bridge site. In the FE model, the pile was considered as an elastic material, and the modified cam-clay model was used to describe the behavior of the surrounding clayey soils. The surface to surface master-slave contact model was used to simulate the pile-soil interface. Pile installation was modeled by applying prescribed radial and vertical displacements on nodes at the soil-pile interface (volumetric cavity explanation), followed by vertical movement to activate the soil-pile interface friction. The results from the FE numerical simulation included porewater pressure generation and dissipation with time, increasing of effective normal stress at the pile-soil interface, and the setup ratios at different times. The results are compared with measured values obtained from the full-scale load tests on concrete piles, which showed good agreement.

The formation of water film is the extreme state of void redistribution in the soil profile with embedded low-permeability interlayer. The thickness of dilation zone (water film) caused by void redistribution is a significant factor to influence the failure or stability of soil. Direct reading method by ruler was utilized in the previous research to measure the dimension of dilating zone. This paper presents a new possible alternative, digital image processing (DIP) technology, to measure dilating zone due to void redistribution. The detailed information and procedures including five steps are presented. The experiment results of settlement, development of water film were measured by using DIP method. Differential settlement of the liquefiable sand layer results in the thickness of water film varies at different locations. The time history of water film at four different locations was analyzed and compared. The results from DIP agree very well with that of direct reading method, indicating that it is possibly a much more effective way than direct reading method.

We present a case study in which analytical predictions are compared to the observed behavior of a bridge pier that settled due to liquefaction during the 2010 M 7.2 El Mayor-Cucapah Earthquake in Baja California, Mexico. Liquefaction can reduce the axial resistance of deep foundations by decreasing frictional and end-bearing resistance, and may also impose downdrag loads due to differential soil and foundation settlement. This often results in the governing load combination for axial design, and can result in a plunging failure if the combined loads exceed the geotechnical or structural resistance of the foundation. The amount of settlement depends on lateral continuity of liquefied layers, interface shear transfer during liquefaction and post-liquefaction reconsolidation, and excess pore pressures mobilized in layers that do not fully liquefy. Our analytical results show that the original foundation design failed to account for the presence of a loose layer near the foundation tip elevation that ultimately caused a bearing capacity failure during the earthquake. Evidence also indicates that the soil may have settled more than the shafts such that downdrag loads were mobilized.

During past strong earthquakes, liquefaction-induced ground movements such as settlements and lateral spreads have caused considerable damages to buildings, bridges, and lifelines. Assessment of such ground movements is of great interest to engineers. This paper focuses on the subject of liquefaction-induced lateral spreads. An evaluation of the existing methods for predicting lateral spreads with the newly compiled dataset from the more recent earthquakes is desirable. In this paper, we compiled case histories of lateral spreads from two major events of the 2010–2011 Canterbury/Christchurch Earthquake Sequence. These cases were assessed from raw data and compiled into a database of lateral spread cases with seismic parameters (moment magnitude and PGA) and soil data (primarily consisting of CPTs). The newly compiled cases were used to evaluate the performance of the existing empirical methods. The results show large scatter in the plot of the predicted versus observed lateral displacements, although the general trend is quite satisfactory.

Levees in the Sacramento-San Joaquin Delta, located in Northern California, were constructed by placing soils dredged from adjacent channels in an unengineered manner atop highly compressible organic soils (i.e. peat). Two 9 m radius centrifuge experiments were performed at the NEES@UCDavis facility with the overall objective to evaluate (1) the seismic deformation potential of peat, (2) levee-peat interaction (analogous to soil-structure interaction), and (3) the liquefaction potential and seismic deformations of saturated loose sand fill overlying soft peat. This paper focuses on development and validation of a water pluviation device constructed to form saturated levee fill. P-wave velocity measurements using an ultrasound system were utilized to verify the degree of saturation achieved in the levee material by various construction methods. Correlations between P wave velocities and B-values are discussed. The vacuum saturation system is shown to provide a high degree of saturation, whereas more traditional water pluviation techniques are shown to produce unsaturated fill.

Characterization of soil response under cyclic loading is one of the major challenges in evaluating liquefaction triggering. In this paper, the results of numerical simulations are presented for dynamic soil behavior during uniform and earthquake loading. For this purpose, Plasticity Model for Sands (PM4Sand) was utilized to simulate soil behavior for a range of loading intensities. This model incorporates a 2-surface kinematic yield mechanism to simulate soil behavior, and more importantly, considers the effect of fabric change and void ratio evolution during loading. Cyclic soil behavior was simulated under a series of uniform sine wave loading and earthquake excitations under controlled boundary conditions and stress paths. Dissipated energy and accumulated pore water pressures were evaluated during these simulations. Triggering of liquefaction was also monitored with different failure criteria. Thereafter, soil behavior was characterized, and a new approach was developed to represent earthquake time histories by equivalent uniform stress series. The proposed approach relates earthquake to uniform loading by the energy dissipated during the stress time history.

A series of experiments were conducted on compacted clay slopes to determine a relationship between void ratio, seepage pattern, rainfall characteristics, and clay slope stability. Rainfall causes the development of perched water table, an increase in the groundwater level and soil erosion. It results in an increase in pore water pressure or a reduction in soil matric suction and loss in shear strength of soil. This study was conducted on compacted clay slopes typical in Southern California. The physical models were prepared by placing the collected soil into a Plexiglas container at the void ratio of 0.89 at different inclinations introducing a target rainfall using a rain simulation system. The seepage rate and pattern, change in moisture content, degree of saturation and matric suction were measured with time. Results showed that seepage velocity decreases with the inclination of slope and the slope of wetting front is gentler than the soil slope in clays. Pore water pressure does not increase uniformly over the entire slope and it depends on the seepage rate of water due to the anisotropic hydraulic conductivity of clays.

For more than 50 years, engineers have recognized that seismically-induced soil liquefaction can cause significant damage to structural foundations, particularly shallow foundations. As a result, many modern building codes such as the International Building Code require geotechnical engineers to analyze and address liquefaction and its potential effects when designing new structures in seismic-prone areas. However, potential liquefaction hazard is often ignored for new residential structures in many parts of the United States, which are often designed in accordance with the International Residential Code. This article presents some of the inconsistencies and dangers associated with neglecting liquefaction hazard mitigation for residential structures. Lessons learned from past liquefaction case histories involving residential structures are reviewed. Commonly observed reasons that engineers and building inspectors often give for neglecting liquefaction mitigation for residential structures are discussed, with concerns over cost identified as the most common reason for this neglect. A comparative study is presented in which two forms of liquefaction mitigation are considered for a hypothetical new residential development. The results of the study show that the cost to structurally strengthen the foundation of each house was only 21% of the cost to improve the soil for each house through the installation of stone columns.

In this study, we introduce results of a novel coupled pore-scale model of pore-fluid interacting with discrete particles for soil liquefaction. A mircoscale idealization of the solid phase is achieved using the discrete element method (DEM) while the fluid phase is modeled at a mesoscale using the lattice Boltzmann method (LBM). The fluid forces applied on the particles are calculated based on the momentum exchange between the fluid and particles. The proposed approach is used to model liquefaction of a saturated granular soil deposit subjected to seismic excitations. Results of conducted simulations suggest that liquefaction is due to reduction in void space during shaking that leads to buildup in pore-fluid pressure.

Pleistocene soil deposits show an increase in liquefaction resistance compared to younger deposits; thus, semi-empirical procedures for evaluating liquefaction potential that are derived from databases of young Holocene soils may not be applicable to aged soils. In this study, the minimum earthquake magnitude and peak ground acceleration required to initiate liquefaction were computed for soils estimated to be about 120,000 to 130,000 years old at the Hollywood site located in the South Carolina Coastal Plain. Discovered sandblows at this site are associated with earthquakes that date back to 11,000 years before present. In situ geotechnical data, including SPT and CPT with pore water pressure measurements, were used with empirical methods that account for the age of the soil deposit to back analyse the minimum earthquake magnitude and peak ground acceleration at the time of the prehistoric earthquakes. When the age of the earthquake was not considered, the magnitude ranged from 7 to 7.2 and the corresponding acceleration ranged from 0.23 to 0.35 g. The earthquake magnitude at the time of earthquake was found to be lower when accounting for age; for the most recent prehistoric earthquake with the age of 546±17, the magnitude was reduced and ranged from 5.7 to 6.7 with corresponding acceleration ranging from 0.17 to 0.30 g.

We present early results of a fully coupled transient three-dimensional model employed to study fundamentals of fine particles migration in granular filters. Filtration process and internal erosion are a particle level phenomenon. A numerical model that is capable of tracking the migration of the base soil particles through the filter pores at a microscale is therefore needed. The discrete element method is used to model the granular material. The pore fluid is modeled at a mesoscale and solved using the lattice Boltzmann method. The proposed approach is used to model the migration of base soil particles through a granular filter. Results of conducted simulation provide the erosion percentage and flow rate during the simulation.

A series of large-scale passive force-deflection tests were performed on a model abutment to investigate the effect of skew angle on performance.Tests were conducted at skew angles of 0°, 15°, and 30° with a backwall that was 3.35 m wide and a backfill that was 0.9 m deep and 6.7 m wide. Test results indicate that the passive force decreases significantly as the abutment skew angle increases to 30° relative to non-skewed walls. These results confirm observations from previous lab-scale tests and large-scale field tests where the abutment width to height ratio was about one-half of that in this series of tests. The results also indicate that the reduced passive force can be accounted for using a simple adjustment factor that is a function of skew angle.The initial stiffness of the passive force-deflection curves was relatively unaffected by skew angle. In addition, the displacement required to develop the peak passive force was about 3% of the wall height regardless of skew angle. Transverse shear resistance developed with displacements less than 2 mm.

The aftermath of the 2011 Mineral, VA earthquake raised concerns on site amplification effects in Washington, DC and the overall Central and Eastern United States (CEUS) region. Current design guidelines for site amplification are set by the National Earthquake Hazard Reduction Program (NEHRP) and are based on research primarily from the Western United States (WUS). However, geology in the WUS and the CEUS differ due to disparate levels of seismic activity. Frequent seismicity in the WUS results in gradually weathered rock, whereas CEUS rock is more intact at shallow depths. This results in impedance contrasts which affect site amplification. This paper presents a study of the site response characteristics of 62 sites in the greater Washington, DC area. Subsurface modeling and equivalent linear site response analyses were performed at each site. The results of this study indicate that current NEHRP design guidelines are inadequate for Washington, DC, specifically for the short-period site amplification factor, F_a. Consequently, the city is at risk of greater than anticipated ground surface shaking intensity in the event of an earthquake.

The estimation of liquefaction potential of soil deposits is mainly based on field liquefaction triggering charts based on the Seed and Idriss Simplified Method. Currently, these field liquefaction triggering charts seem to be generally conservative, as they do not take into account factors that tend to increase the liquefaction resistance of natural sand deposits located in seismic areas. The work presented in this paper incorporates data from the field, as well as centrifuge experiments performed at RPI. The experimental work involved simulating several decades to a century of earthquake events applied to a 6-m uniform silty sand deposit. The results show that repeated earthquake shaking generally has the effect of increasing the liquefaction resistance of soil deposits over time. This increase in liquefaction resistance does not seem to be fully accounted for by the simultaneous increase in the shear wave velocity of the soil. In other words, sites that have been subjected to hundreds of small earthquakes as well as some larger liquefying events may not liquefy again unless they are subjected to very intense earthquake shaking.

One of the major reasons of levee failure is erosion due to overtopping. The overtopping of levees is occasionally the consequence of a flood or hurricane. In these events, the surface layers of levees become saturated in advance of any overtopping due to rain and storm events. In this investigation, the effect of the saturation ratio and almost vertical impingement of overtopped water from floodwall on scour development is studied. For this purpose, laboratory physical models of a typical levee on the banks of Mississippi river with a scale of 1:20 were constructed. A 2.4 mm thick wooden plate, which was embedded in the crest of the levee represented the floodwall. Silty soil materials with various saturation ratios were used to observe scour potential of the soil. In all the tests, the scour development and the stability of the wall were monitored and analyzed for each test during overtopping. Hydraulic and geometric parameters including densimetric Froude number, compaction level, water content, and levee dimensions were recorded to have a representative comparison between the laboratory models and constructed levees in practice. In addition, the erodibility of the levee materials was determined using erosion function apparatus (EFA). The results of EFA tests were compared to physical model test results to explore and discuss the vulnerability of levee systems to erosion when the surface soils are saturated and floodwall overtopping is experienced.

Seismically induced soil liquefaction is a significant seismic hazard that has caused substantial damage to foundations and other aspects of infrastructure in past earthquakes. The risk of soil liquefaction and subsequent unsatisfactory foundation performance often leads to the installation of remedial ground improvement, usually at significant cost to the project. While the majority of engineering practitioners use empirical triggering models to evaluate liquefaction initiation hazard, there is typically substantial uncertainty associated with these types of approaches. Performance-based earthquake engineering (PBEE) design methods have recently been introduced that will allow engineers to directly account for this uncertainty and express liquefaction triggering potential in seismic hazard curves for factor of safety against liquefaction. However, many engineering practitioners are choosing to move away from subjective factor of safety metrics. Although PBEE liquefaction assessment methods already incorporate the probability of liquefaction into the development of factor of safety hazard curves, these engineers would prefer the development of probability of liquefaction hazard curves. This paper derives a simplified approach for obtaining such hazard curves directly from factor of safety or N_req hazard curves for two popular probabilistic liquefaction triggering models. Such an approach allows engineers to easily switch between factor of safety and/or probability of liquefaction metrics. An example case study is demonstrated with the two probabilistic liquefaction approaches. The potential for probability of liquefaction to be incorporated into the performance-based assessment of certain liquefaction effects is briefly discussed.

Most levee underseepage and uplift analyses are based on steady-state seepage and can yield conservative results. Although computations are simpler and steady-state seepage parameters are easier to determine and readily available, transient and unsaturated seepage analyses are more representative of levee seepage conditions. Transient seepage analyses using a case study floodwall indicate that as soil compressibility of the underseepage layer decreases, rapid landside pore-water pressures increase and can approach steady-state values. The transient results for this case study also indicate that uplift factor safety during the flood event are about 25% higher than steady-state. The effect of soil compressibility can delay or accelerate the onset of uplift water pressure increase from the initial steady-state conditions.

Construction of a large retail store in Silverthorne, CO required a permanent earth retention system to support an existing roadway. Site constraints imposed the use of top-down construction through two separate landslides and layers of stiff fissured clay shale. The design of the retaining walls accounts for the potential degradation of clay shear strength through the use of fully-softened values. It also accounts for the presence of weak clay at the interface of landslide rubble and underlying shale rock. A loose, blocky, weathered shale layer encountered within the geologic profile of the earth retention system provided a number of construction challenges. This paper describes the site conditions, design considerations, and key aspects of the wall construction.

A full-scale drilled shaft retaining wall was constructed in Manor, Texas on a site underlain by approximately 15 m of the highly overconsolidated, expansive Taylor clay. This wall was instrumented with inclinometers and fiber optic strain gauges. During a four-year monitoring period, performance data were recorded during construction, excavation, seasonal moisture fluctuations, and controlled inundation testing which provided the retained soil with access to water at the ground surface. This paper discusses performance of the test wall over a range of soil moisture conditions, including an extremely dry state caused by the most extreme drought on record in this area and the wettest possible state when wall deflections ultimately reached equilibrium after eight months of controlled inundation. The wettest possible state corresponded to the development of drained conditions in both the retained soil and the foundation soil. The maximum earth pressures applied by the retained soil were comparable to active conditions mobilizing the drained, fully-softened shear strength; there was no evidence of greater pressures being applied as the soil swelled to its ultimate equilibrium condition. The measured p–y curves for the foundation soil were consistent with passive conditions mobilizing a drained shear strength between the peak and fully-softened strengths.

Foundation and tunneling projects often require complex support of excavation (SOE) systems. Application of conventional shoring with sheet pile, soldier pile or soil nail walls can be limited by excavation depth, challenging ground conditions and high groundwater levels. Recently completed support of excavation systems, including Seattle’s Alaskan Way Viaduct Replacement and the Port of Miami Tunnel required shoring in extremely difficult conditions. Innovative ground improvement techniques were combined with traditional shoring methods on a massive scale to provide integrated lateral support and groundwater control for these projects. Powerful state-of-practice specialty foundation equipment was used to construct blocks of low permeability soil for safe-havens, emergency cross passages and the tunnel boring machine break in/out plugs. In situ mixing tools were advanced through variable, highly porous limestone formations. Large diameter secant pile walls, installed through extremely difficult ground conditions with running sands, wooden debris and cobbles and boulders, provided the support for the Tunnel Boring Machine launch and retrieval portals. Creative support of excavation solutions made practical by the most modern equipment and tooling made these cutting edge projects feasible and cost effective.

The active earth pressure developing in granular backfills is directly related to the internal friction angle. It is well known that the internal friction angle is a function of the level of mean effective stress and the level of shear strain in the retained soil. Both these variable change as the wall moves away from the backfill due to the compliance of the foundation soil. In this paper, simulations of the response of the wall-foundation-backfill system are performed using the finite element method in order to study the interaction between wall movement and active earth pressure. The granular soil is modeled using a bounding surface plasticity constitutive model for sands based on critical state soil mechanics. The finite element analyses show that the wall system reaches a minimum active stress state associated with a peak soil friction angle at wall crest displacement less than 0.5% of the wall height, relevant to a serviceability limit state rather than an ultimate limit state. By the time, the ULS is reached the friction angle mobilized in parts of the retained soil mass has approached the critical state friction angle value due to the intense shear straining.

Design of an excavation support system must satisfy the minimum factors of safety for stability requirements and the wall deformation and/or ground settlement requirements. In this paper, the authors present an application of robust geotechnical design (RGD) method on the design of braced excavations. The essence of RGD is to derive an optimal design through a careful adjustment of the design parameters so that the response of the braced excavation system is insensitive to the variation of “noise factors” such as uncertain soil parameters, model errors, and construction variation. The robust design of a diaphragm-wall-supported excavation requires an optimal selection of the design parameters such as the length (L) and thickness (t) of the wall, the vertical spacing of the struts (S), and the stiffness (EA) of the strut. Within the RGD framework, the effect of uncertainties in the noise factors on the variation of the system response is evaluated. Furthermore, the design robustness is sought along with the cost efficiency and safety. Thus, the RGD methodology involves a multi-objective optimization. As cost and robustness are conflicting objectives, such optimization usually leads to a Pareto front, which offers a tradeoff that can aid in making an informed decision.

A considerable number of authors and authorities have come to propose their own set of apparent lateral earth pressure diagrams for braced excavations. When stiff clays dominate, all diagrams reduce the apparent earth pressure to zero at the subgrade level. In the author’s experience, this practice is likely both unconservative and unsubstantiated for modern urban excavations and may lead to unsatisfactory wall performance. While the actual equivalent earth reaction at subgrade has rarely been directly measured it is still incorporated in apparent earth pressure diagrams. Hence, current practice diagrams truly cover earth pressures only down to midway between the lowest support level and the excavation subgrade. Furthermore, little guidance is offered in terms of defining the appropriate lateral driving earth pressure below subgrade and misguide designers to make questionable design assumptions or even assume zero lateral driving earth pressure below subgrade. A series of controlled finite element simulations were performed to examine the behavior of lateral earth pressures near and below the lowest support level. Finite element results from both the controlled cases and from benchmarked excavation models are compared. Last, results are condensed into simplified modifications and diagrams that can be applied to any apparent earth pressure diagram.

The expansive soil stabilization using lime and or cement is frequently considered by geotechnical engineers in many parts of the world as an effective treatment. This study investigated the changes in strength properties for one day and seven days curing of lime-treated expansive soil from Al-Qatif in Saudi Arabia. Variations in index and geotechnical properties were studied for clays treated with 4% and 8% lime. The trends of stress–strain relationship were viewed and variations in initial tangent modulus and secant tangent modulus were reported for different lime content and curing periods. The outcome of this study is helpful in forecasting strength development within stabilized expansive soils and will help geotechnical designers assessing the stabilization efficiency.

This study presents the outcome of an experimental investigation focused on lightly stabilised material’s durability under freeze-thaw (f-t) and wet-dry (w-d) conditions. A widely used road base granular base material was selected for the study which was then reconstituted to a particular particle size distribution. A combination of cement and flyash in a ratio of 3:1 was used to stabilise the material with two different binder contents of 1.5% and 3%. Unconfined compressive strength (UCS) of lightly stabilised material subjected to different number of f-t and w-d cycles was evaluated using cylindrical specimens molded at optimum moisture content and cured for 7 days. Strain measurements were taken internally using two extensiometers to calculate the modulus and to observe stress-strain behaviour. The effect of hydration or pozzolanic reaction and its significance in assessing the durability of the stabilised material was also evaluated. Another set of samples cured under normal curing conditions were made to compare with the f-t and w-d samples and to evaluate the degree of degradation with the age. It was found that samples subjected to w-d cycles deteriorated heavily compared with f-t cycles though the increase in binder content helped to deter the adverse w-d effect. Strength gain due to accelerated cementitious reaction was observed in the samples subjected to w-d cycles and the rate of strength gain was found to be dependent on samples’ curing days. Samples subjected to f-t cycles also showed increase in strength up to 12 f-t cycles possibly due to the decline in moisture content.

This paper explains the behavior of a cantilever retaining wall (CRW) backfilled with light weight fill material through small scale model wall tests. CRW model of height 60 cm and base width 50 cm was built with hollow aluminum sections. The model wall was installed in a Perspex container, tested under static and seismic loading conditions. Waste tire chips of 1 cm square cross section and 20 mm length mixed with the cohesionless sand in 5%, 10%, and 15% by weight were used as light weight backfill material. Concrete cubes were used as surcharge loading on the backfill during static testing. The lateral wall movements along the height of the wall were monitored during tests using displacement transformers. About 1 g shaking table tests have been conducted on the selective models to check the behavior of the cantilever wall under seismic loading conditions. It has been observed that the inclusion of tire chips in the backfill soil has led to the reduction of lateral wall movements due to the lesser unit weight of the mixtures. The reduction in the acceleration of the backfill was also observed during seismic testing in sand-tire chip (S-TC) backfill compared to the controlled case (only sand).

Reinforced earth or soil structures are becoming increasingly popular in the present day. For proper design of any reinforced structure, it is important to study the soil-reinforcement interface properties. The interaction mechanism can broadly be classified into two types: direct shear mechanism and pullout mechanism. In this study, tests were performed as per ASTM D5321 to study the interface characteristics of two types of reinforcements commonly used in practice (geogrid and metal grid) with Indian standard sand. A large-size direct shear test apparatus of dimensions equal to 300 mm x 300 mm x 200 mm (in length, width, and depth) is used in the study. Pluviation method is adopted to prepare uniform sand samples with a relative density of 90%. This paper provides details on sample preparation and interface properties of two types of reinforcements with sand material. Based on the test results, the average interface shear strength coefficients of geogrid-sand and metal grid-sand are found to be equal to 0.88 and 1.02 for the normal stresses considered in the study. These coefficients are in good agreement with the results reported in the literature.

Current engineering design methods for evaluating the seismic lateral earth pressures of retaining walls are based on limit equilibrium Mononobe–Okabe method. In limit equilibrium method, the effect of dynamic loading is introduced to the soil wedge behind the retaining wall as lateral and vertical inertia forces. The two most important simplifications of these methods are application of pseudo-static solution procedure for a fully dynamic problem and assumption of cohesionless backfill material. In this investigation, a full dynamic numerical modeling on a retaining wall with low frictional angle backfill material is conducted to evaluate the seismic performance of retaining wall and lateral earth pressure variation during the earthquake. A 6-m high cantilever wall with a base width of 4 m and thickness of 0.5 m is represented by structural element. The concrete wall was assumed to perform elastically and the Mohr–Coulomb constitutive model was selected for soil material. The interaction between concrete wall and soil was modeled by using elasto-plastic bilinear model to account for shear sliding and normal separation of wall and soil. The performance of the retaining wall was analyzed under three distinct earthquakes. The lateral earth pressure distribution along the wall height was evaluated during the earthquakes and was compared to static earth pressure. Furthermore, a set of dynamic analysis were conducted with normalized peak ground acceleration, PGA, of the earthquakes. The dynamic lateral earth pressure coefficients along the stem, middle and heel of the wall during the earthquake were analyzed for various horizontal PGAs induced by earthquakes. Consequently, the lateral earth pressure coefficients along the wall were compared to those concluded by Mononobe–Okabe method. According to the results, in low frictional angle soil backfills that have some cohesion, the lateral earth pressures are overestimated by Mononobe–Okabe method.

This paper presents results of three dimensional finite element simulations of vertically stiffened sheet-piles, the so-called composite sheet piles, in cohesionless soil. The research is intended to investigate the potential for cost savings and improving performance by using vertically stiffened sheet-piles supporting deep excavations. The effect of beam stiffness distribution ratio (BSDR; Z_beam/Z_sp), beam spacing to excavation depth ratio (S/H), and excavation height (H) on the performance of the composite section were investigated. The results are presented in terms of plane strain ratio (PSR), defined as the maximum horizontal deflection of the vertically stiffened wall obtained from 3D analysis divided by the maximum horizontal deflection of a wall having an equivalent stiffness in plane strain condition; the moment ratio, defined as the maximum bending moment on the vertically stiffened wall obtained from 3D analysis divided by the maximum bending moment of a wall having an equivalent stiffness in plane strain condition; and the weight ratio, defined as the weight of the steel section (including the weight of wall and vertical stiffener) per square meter in 3D analysis divided by the weight of steel section (weight of wall) per square meter in plane strain condition. The introduction of vertical stiffeners in a composite section helped reduce the bending moments on the sheet-piles, which is translated to reduction of materials (sheet-pile steel sections) required by a range of 20% to 35%, knowing that it would be best implemented in excavation depths ranging between 5 m and 7 m. On the other hand, the performance of the sheet-pile wall, in terms of deflections, did not improve.

Conventional methods of analysis and design of reinforced soil walls consider only axial direction of the pullout force and do not consider complex soil-reinforcement interaction and obliquity of the pullout force. However, kinematics of failure of the walls suggests that the failure surface intersects the reinforcement obliquely thus causing an oblique pullout of the reinforcement. Consequently, the reinforcement deforms downward and mobilizes additional normal and shear stresses at the soil-reinforcement interface. Thus, the pullout capacity of the reinforcement may be considerably different compared to the axial one. In this paper, a new analysis is presented for the design of reinforced soil walls considering that the reinforcement is subjected to an oblique pullout force and resting on a two-parameter Pasternak subgrade. The contribution of shear stiffness of the subgrade has been incorporated in the analysis by assuming a Pasternak shear layer resting on a set of Winkler’s springs. Thus, use of Pasternak model as subgrade makes the analysis more realistic. A modified factor of safety is defined, evaluated, and compared with the conventional one to establish the suitability and applicability of the present analysis in the design of reinforced soil walls. A parametric study is also conducted to study the effect of various geometrical and material properties on the stability of reinforced soil walls.

This paper pertains to the model testing results of cellular reinforced fly ash walls subjected to surcharge loading. Fly ash is fine residue produced from thermal power stations as a byproduct. The enormous quantity of fly ash produced requires huge disposal area and creates environmental problems. In India, where the land to population ratio is small, acquiring huge areas of land for the safe disposal of fly ash is not easy. The utilization of fly ash and its disposal in an environmentally friendly manner is a foremost concern in India. In the present study, a series of model experiments were carried out for proper utilization of fly ash as an alternative backfill material in the cellular reinforced fly ash walls. Locally available waste plastic water bottles were used to prepare the cellular reinforcement. The diameter of bottles used for cellular reinforcement is 50 mm and with varying heights of 10 mm and 20 mm. The effect of coverage ratio with single and double anchored cellular reinforcement systems on the horizontal displacement of full height facing panel and settlement of the backfill was studied. The observed failure surcharge pressure was higher for the double anchored system for both the reinforcement heights, indicating better performance of wall in terms of carrying load before failure. The cellular reinforcement of height 20 mm showed better performance over 10 mm.

Current AASHTO specifications for MSE wall construction require granular backfill used in wall construction to be compacted to achieve 95% of the maximum dry density as determined by AASHTO T-99. However, the degree of compaction specified above is rarely achieved in the field on a consistent basis. Lower compaction levels can adversely impact the pullout resistance capacities of soil reinforcements embedded in the backfill. This paper documents findings from a large scale laboratory test program in which a total of 99 ribbed strip type MSE reinforcement were tested in a sandy backfill to evaluate the impact of compaction level on the pullout resistance of reinforcements. The tests were conducted using a test box with dimensions of 3.6 m×3.6 m×1.2 m (12 ft×12 ft×4 ft). Test specimens of lengths 1.2 m (4 ft), 2.4 m (8 ft) and 3.6 m (12 ft) were tested at overburden pressures equivalent to 1.5 m (5 ft), 3m (10 ft), 6 m (20 ft) and 12 m (40 ft) of backfill at two different levels of backfill compaction. The data collected were then used to calculate the pullout resistance factor (i.e. F*) for each reinforcement. Subsequently, appropriate statistical analyses (ANOVA) were conducted on the calculated F* to evaluate the significance of the degree of backfill compaction on F*. Results from ANOVA show that compaction is a highly-significant variable (p=0.000). Moreover, review of F* data collected show that “slight” under-compaction can lower MSE pullout resistance for ribbed strips significantly. Data for the under-compacted pullout tests approached the AASHTO reference line for F* while data for the properly compacted tests yielded F* values that were significantly higher. The influence of the compaction level on F* decreased as the depth of fill increased.

An innovative alternative to conventional bridge support technology, the Federal Highway Administration’s (FHWA) Geosynthetic Reinforced Soil Integrated Bridge System (GRS-IBS) utilizes closely spaced layers of geosynthetic reinforcement and compacted granular fill material to provide direct bearing support for structural bridge members. The current paper describes a series of parametric model analyses that were performed to simulate the behavior of a typical GRS-IBS using the finite element method. Numerical simulation of the structure and its foundation were performed for both the construction and operation phases of the project. The input parameters that were assessed parametrically include: the friction angle of the reinforced soil, the cohesion of the reinforced soil, the geotextile stiffness, and the interface rigidity. The relative effects of changes in the input parameters were assessed by examining the resulting GRS-IBS abutment deformations, the maximum tension in the geotextile layers, and the factor of safety against stability failure.

The geosynthetic-reinforced soil (GRS) bridge abutment is a new technology that has many advantages over traditional abutment designs, including cost savings, relatively easy and fast construction, and good performance with regard to differential settlements. The GRS bridge abutment is a complex system that includes a lower GRS wall, bridge seat, and upper GRS wall, with the bridge superstructure load applied directly to the backfill for the lower GRS wall. This paper presents numerical simulations of the static response of a typical GRS bridge abutment during construction and service. The numerical simulations include soil–reinforcement, soil–block, block–block, and soil–bridge seat interactions. Analyses were performed in stages to simulate the abutment construction process. A uniform surcharge load was applied on the bridge deck and approach roadway to simulate traffic loads during service. Results for construction and in-service conditions are presented and discussed, with particular focus on wall facing lateral displacements and bridge seat settlements. The effect of bridge load on the deformation behavior of the GRS bridge abutment was also investigated. Numerical results indicate that the abutment has good performance under static loading conditions with relatively small lateral deflection and settlement, and relatively large load bearing capacity.

Results are presented of numerical parametric analyses on the phase difference between seismic earth thrust and wall inertia, in the case of non-yielding earth retaining structures under earthquake loading. The FEM is used for modelling gravity, non-yielding walls with heights 4.0 m and 7.5 m, supporting horizontal cohesionless backfill with varying density (loose to dense) under earthquake shaking, with PGA varying from 0.05 g to 0.70 g and frequency equal to 3Hz. The results of analyses indicate that the phase difference between the two dynamic actions is small and thus it is justified to use the sum of their maximum values in the design of this type of earth retaining structures.

With a population over 8 million, New York City is the most densely populated city in the United States. With each passing year, more and more people move into such large cities. When considering new construction in New York City, a building owner typically faces zoning limitations on construction height, so owners often build multilevel deep cellars coupled with building to the property line limits. Deep cellars in densely populated New York City are particularly difficult to excavate because of varied subsurface conditions, site constraints, and adjacent structures. This paper discusses two case studies relating to varying subsurface conditions, foundation challenges, lot-line construction limitations, and site constraints. These two case studies are presented for new construction with design challenges related to multiple basement levels, lot-line construction, landmarked buildings, groundwater control, adjacent structures, and varying subsurface conditions. The first site discussed was partially landmarked, surrounded by eight landmarked structures, and required detailed underpinning and monitoring. The second site had a steeply dipping bedrock surface and a shallow water table, making a secant wall necessary for constructing the multiple basement levels required for the project.

Construction of a new multi-story high school in downtown Chicago, Illinois required a 5.5 m (18 ft) deep supported excavation. The 122 m (400 ft) × 30.5 m (100 ft) site was bordered on two sides by city streets and buried utilities, and on the other two sides by existing multi-story structures founded on shallow spread footings. The initial geotechnical exploration revealed the presence of urban fill underlain by very soft clay to depths well below the proposed excavation depth. An earth retention system (ERS) consisting of sheet piles and internal bracing was designed and constructed to protect the surrounding utilities and structures. Additionally, global stability was a concern due to the depth of the very soft clay and adjacent surcharge loads. This paper presents information about the design, construction, and observed performance of the excavation support system.

This paper will explore a series of design and construction issues which have been encountered while developing urban sites throughout the past 15 to 20 years. The sites are not identified by specific name, but rather by general area. The intent here is to provide insight into a design process that recognizes the subsurface conditions in the development environment and allows an engineer to envision strategies to solve problems.

Examples of braced excavation and foundation systems of tall buildings in the Houston Area are presented through a case study of the recently completed B G Group Place, Houston’s tallest building to start the 21st millennium. The building is considered one of the tallest soil-supported buildings in the world at 48 stories from basement to top when compared to the 75 story Chase Tower. The presentation is expanded by performance information from other local braced excavation projects in the Texas Gulf Coast to capture the broad character of excavation behavior. Properly designed and built Houston Area excavations enjoy behavior characteristics unique to those reported in other locations.

Estimating movements and the effects of deep excavations on existing improvements is a critical step in the design process. Important questions include, what are acceptable levels of movement considering the built environment and the surrounding population. Boston is an old city with aging infrastructure often located below narrow streets originally intended for horse carriages: poor soils, high groundwater level, and activity pose underground development challenges. The effects of excavations on buildings and utilities such as old water and sewer pipes and new fiber optic cables need to be considered. Detrimental or unanticipated performance during construction can affect existing improvements and cause construction delays. Potential impacts to nearby improvements caused by excavation induced soil displacements need to be identified, addressed and communicated within and outside the project team. Abutters can influence the design, requiring designers to consider construction means and methods to reduce impact from settlement, vibration, odor, dust, and noise. This paper discusses anticipated and measured performance of deep excavations in the soft clay soils that underlie the Boston Basin and provides the authors’ experience defining tolerable movements and public involvement. The case history data presented is based on designs developed to provide a system that performed to tolerable levels. The design must balance economics with the project’s risk tolerance level. Identifying this risk tolerance early in the design is critical as it varies significantly between different owners.

The March 11, 2011 earthquake (Magnitude 9.0) and the subsequent tsunami in northeastern Japan caused a loss of many lives and structures. The 17.9 km　(11.8 mile) long reconstruction of heavily damaged levees of Old Kitakami River in Ishinomaki City is being conducted by driving sheet piles and tubular piles into the riverbed in front of the existing but damaged levees and river walls. The press-in piling method is widely utilized on the project, which only generates low noise and very low vibration. Therefore, it is suited for the area where homes, schools, and business are flanking the levees. In order to effectively deal with the gravely soil conditions and sunken debris brought by the tsunami in addition to previously installed ripraps, the press-in piling equipment with an auger attachment for sheet piles and the Gyro press piling equipment for tubular piles are utilized. The Gyro press piling equipment is rotating and simultaneously pressing in tubular piles with drill bits welded at the toe of each tube pile. This method enables the pipe piles to be driven through the ripraps, large boulders, and/or concrete debris without removing them.

Removable compressive and distributive strand anchors were successfully used to anchor portions of the temporary support of excavation for the Hudson Yards development in Manhattan, New York. The removable strand anchors were implemented in lieu of conventional anchors to allow future excavation for a cut-and-cover tunnel and caissons. This paper describes the principles of removable compressive and distributive anchors, the installation and testing methods typically used, and the de-tensioning and removal procedures for the anchors. This paper also discusses lessons learned from the installation, testing, and removal of the anchors at Hudson Yards. The anchors used at Hudson Yards were bonded in bedrock. The findings from this study may prove useful to engineers considering the use of removable compressive and load distributive strand anchors for temporary support of excavation systems.

This study involves an evaluation of the design and construction process for a soil-borehole thermal energy storage (SBTES) system installed in a sandy-silt deposit. A series of simplified numerical simulations were performed to understand the role of different variables on the heat storage in the SBTES system. The results indicate that soils with lower thermal conductivity have less lateral heat loss, and that arrays with smaller borehole spacings permit more concentrated storage of heat at higher temperatures.

Energy piles satisfy two main functions: they transfer the load from the building to the ground and they also exchange heat with the ground; which is used for heating and cooling purposes. Because energy piles are relatively short, they may be partially embedded in unsaturated soils. Saturation conditions influence the thermal properties of the soil and therefore the heat exchange rate and thermodynamic efficiency of energy piles. This paper evaluates the effect of unsaturated soil conditions on the heat exchange rate and thermal efficiency of energy piles through laboratory experiments and numerical simulations. The laboratory tests considered an energy pile slice at a certain depth. The temperature field evolution generated from the operation of the energy pile in different soil saturation conditions was measured at the soil-pile interface and in the soil. The laboratory test was then modeled numerically and the results of the numerical model were used to evaluate the heat exchange rate and thermal efficiency of energy piles in unsaturated soil conditions. The results of this paper showed that saturation conditions could significantly impact the heat exchange rate of energy piles. In addition, the results showed that assuming that conduction is the primary mode of heat transfer, the thermodynamic efficiency of energy piles could drop by 40% in sand at very low saturation.

Ground-source heating of bridge decks is a promising technology that can drastically reduce the use of corrosive and environmentally unfriendly deicing salts. In this concept, the foundation system of the bridge substructure and the approach embankment are designed to access the ground as a renewable energy source. During the winter, heat energy is extracted from the ground and can be circulated as warm fluid through the tubing system within the bridge deck slab to prevent icing and freezing. Heat energy can be collected in the summer through circulation tubes embedded in the concrete bridge deck and stored in the ground for use in the winter. This paper presents experimental results from several tests performed using a model-scale bridge deck connected to energy piles. The results include the response of temperatures in both the bridge deck and ground during winter heating and summer recharge operations. During heating operations, it was observed that the system was able to extract enough energy from the energy piles to keep the deck snow free during moderate snow storms. The temperature in the ground around the pile decreased during heat exchange operations and then recovered quickly afterwards in a matter of days. During summer recharge, the system was able to increase the temperature of the ground as it injected thermal energy. From this study, conclusions are drawn about the system’s ability to perform under a variety of environmental conditions and recommendations are given for system operation.

Energy piles are deep foundation elements designed to utilize near-surface geothermal energy, while at the same time serve as foundations for buildings. The use of energy piles for geothermal heat exchange has been steadily increasing during the last decade, yet there are still pending questions on their behavior during temperature changes. A series of field tests on three different energy piles was carried out in Richmond, TX, with the aim of quantifying the thermal influences on the performance and capacity of energy piles. The field test program included conventional pile load tests and application of temperature cycles with maximum temperature of 45°C (113°F) and minimum of 8°C (47°F) over a total duration of six weeks. The test piles with and without maintained structural loads were exposed to heating-cooling cycles to investigate the effect of thermo-mechanical and thermal loads on the energy piles, respectively. With the use of fiber optic cables, vibrating wire strain gauges, thermistors and thermal integrity profile wires, the temperature and strain profiles were monitored on the test piles throughout the field tests. This paper presents the findings inferred from the recorded data along with the details of the in-situ tests on energy piles.

The combination of the Ground Source Heat Pump (GSHP) with energy piles has become a viable alternative to traditional indoor climate control. As geothermal energy pile applications increase in size and demand, maintaining the highest possible efficiency is paramount. Therefore, a numerical analysis was performed to investigate the relationship between construction specifications and energy pile efficiency. In particular, inlet flow rate and concrete cover were parameterized within two heat exchanger tube configurations including “U-shape” and “W-shape” configurations. Additionally, cyclic and constant thermal loadings were compared using COMSOL multi-physics software. Simulation results indicate that heat rejected is limited by surface area of the heat exchangers and residence time of working fluid. For this model, an apparent maximum heat rejected was achieved at 240 cm³/s/pile (3.8 gpm) for both U-shape and W-shape configurations. Beyond 240 cm³/s, the increase of rejected heat was negligible. The study also demonstrated that concrete cover contributes significantly to energy pile efficiency. A reduction of concrete cover decreased potential cyclic heat rejected by up to 20%. The comparison of tube configurations bolstered conclusions in the literature that the W-shape configuration is most effective at rejecting heat, improving efficiency by approximately 20% compared to the U-shape configuration.

Geothermal deep foundations (or energy piles) are used to support structural loads and to exchange heat with the surrounding soil. The operation of the heat pump (heating vs. cooling or working vs. stopping) presents new challenges to foundation engineers; one of which is the change of soil-pile interface force (skin friction). The heating and cooling of the pile leads to expansion and contraction which affect the soilpile interface properties. To characterize temperature effects on the soilpile interface and interaction for energy piles, a new testing device (thermal-modified borehole shear test or thermal-mBST) was developed. The developed automated testing device permits direct measurement of the shear stressvertical displacement relationship (tz curves). Furthermore, the device permits evaluation of the effects of temperature change and cycles, and the effects of pile expansion and contraction on soilpile interface properties. The thermal-mBST test was performed in a soil container at three different temperatures simulating a baseline ambient temperature (21°C) and the temperatures of energy piles during the heating and cooling seasons (2°C and 40°C). The pile expansion and contraction were also simulated during the tests. The primary experimental findings of expansion and contraction effects on the shearing behavior were presented in this paper.

Among several parameters that affect pile-soil heat exchange, ground thermal properties play a major role. Although heat conduction is commonly considered to be the key heat transfer mechanism within the ground, heat convection in the presence of ground water flow can increase heat rejection and extraction to and from the ground. On the other hand, temperature gradient induced by thermal operations of geothermal piles may alter pore fluid density, and consequently, buoyant flow can occur even under hydrostatic condition within saturated soil in the vicinity of heat exchanger piles. Thermally induced pore water flow and its effect on temperature increment in the soil surrounding geothermal piles are investigated in this paper by coupling heat transfer equations and Brinkman’s momentum equation that considers a Boussinesq buoyancy term. Results demonstrate that thermally induced pore water flow in saturated soil may cause a considerable reduction in ground temperature increment in a zone surrounding the pile. Such a reduction in ground temperature increment for most part of the pile length is expected to increase heat exchange efficiency of geothermal piles.

There are a great number of abandoned mine shafts in the US as well as other countries. Taking the Upper Peninsula (U.P.) in Michigan, for example, abandoned copper mine shafts are widely distributed in the area and about 90% of them are filled with water. This study presents preliminary results on the use of abandoned mine shafts for geothermal applications, which include a field study, a theoretical framework, and preliminary simulations results. The field study involved measurements of temperatures and chemicals in the mine water, which are of major concern in recovering geothermal energy from mine water. The theoretical framework provided a mathematical description for studying the scientific issue. It is the first time such a framework is established for holistically formulating the coupled physical processes in the mine water-surrounding porous material system. Preliminary simulations were conducted to test a critical part of the theoretical framework. The simulation results provided interesting insights into the phenomena observed in the data measured in the field study.

This paper focuses on the evaluation of the thermo-mechanical response of a 15.2 m-long energy foundation in dry sandstone over a 4-month period. Although the foundation was not actively heated or cooled using a heat pump, the fluctuations in the temperature of the heat exchange fluid occurred due to seasonal variations in the mechanical room temperature. Although these fluctuations only led to small changes in foundation temperature (from −1 to 1°C), these were sufficient to evaluate the mobilized coefficient of thermal expansion of the foundation. Further, the trends in the thermal axial stress and strain with depth in the foundation were evaluated, along with the mobilized side shear stress and axial displacement.

Geothermal heat pump has been spotlighted since 1990s for its characteristics of environmental friendly, cost effective, sustainable and reliable. To study such a complex system with various influencing factors, it is important to explore a reliable model with optimized parameters. In this paper, we report a 3D geothermal heat pump model for the prototype geothermal heat pump system installed under a three-floor resident house located in Cleveland, OH, USA, based on which a sensitivity analysis is carried out to explore the influence of pipe depth, fluid flow velocity, pipe diameter, thermal properties of borehole refilling material on the underground geothermal heat exchanger performance. The relationship between the extracted heat per depth of geothermal heat pump system and those influencing factors are obtained so that the key influencing factors on the geothermal heat exchanger performance are decided. This study may provide support for the optimized design of geothermal heat pump system for both commercial and residential house applications in the USA.

Deep foundation/soil interfaces are subjected to temperature variations due to seasonal effects, extreme climates, and energy foundation applications. This investigation was conducted to determine the effects of temperature on the interface shear strength between sand and steel. The materials used for the experimental investigation included mild A36 steel to represent pile foundations and medium, well-graded sand. A large-scale interface direct shear apparatus (300 x 300 x 150 mm depth) was used for testing. Tests were conducted at three normal stresses (50, 100, 150 kPa) and at three temperatures (2°C, 20°C, and 40°C). The sand was prepared to a relative density of 75%. The steel plates were analyzed before and after shearing using a noncontact white light optical interferometer to characterize changes in surface texture of the steel due to shearing against sand. Overall, interface friction angle decreased slightly with temperature. Peak interface friction angles were 20.1°, 19.9°, and 19.0° for tests conducted at 2°C, 20°C, and 40°C, respectively. The surface characteristics of the steel plates varied significantly due to shearing at the test temperatures and normal stresses.

Thermal operation of geothermal piles changes ground temperature as heat is injected to or extracted from the ground. Formulation of a finite difference (FD) model that can predict heat exchange through geothermal piles with an embedded heat exchanger element is briefly described. The FD model simulates heat transport by the circulation fluid and heat conduction in the surrounding media (circulation tube, concrete pile, and soil). Numerical predictions are compared with data gathered from a thermal test on a model-scale geothermal pile installed in dry sand. Results obtained from numerical analysis are in excellent agreement with physical model test data. Thus, validated numerical model can further be used for predicting thermal performance of full-scale geothermal piles under varying field conditions.

The present work investigates the behaviour of geothermal energy piles in sand subjected to thermal loading and the resulting soil-structure interaction numerically, using the finite element software Abaqus and user-defined material subroutines for soil. The stress–strain response of sand has been simulated using CASM constitutive model based on critical-state soil mechanics. Detailed parametric sensitivity studies have been carried out to understand the effects of relative densities of the soil, coefficients of lateral earth pressure of the ground, lengths and diameters of the pile on the deformation of pile and soil and stress response of soil. The results show that the negative shear stress generates in soil at the pile-soil interface. The lateral earth pressure coefficient in soil surrounding the pile increases due to thermal loading.

With the rapid development of offshore wind energy, the seismic stability of foundation structures is a concern, especially if the soil is sandy soil that is susceptible to liquefaction. One of the commonly used foundation structures for offshore wind is the bucket foundation. A group of centrifuge tests were performed to study the seismic behavior of the foundation. Acceleration, pore water pressure, settlement, and lateral displacement were recorded to analyze the seismic response of both the upper structure and foundation. The influences of design parameters such as size of the foundation, depth of penetration in the ground, compartments within the foundation were evaluated. The experimental data show that the bucket foundation is capable of resisting failure under seismic event.

An increase in the height of new generation of wind towers is foreseen in order to improve their performance. This will imply larger shallow foundations, which represent a substantial percentage of the overall budget. Consequently, it is of interest to develop alternative foundation solutions, with a smaller environmental impact, in particular in terms of the required volume of excavation and reinforced concrete. The proposed improvement consists in the use of micropiles placed along the foundation perimeter as a way to increase the overturning resistance of the system as well as the foundation behavior. The main focus of this paper is the characterization of the behavior of single and groups of micropiles, tested under controlled conditions. An extensive set of experimental tests were conducted on single and 2x2 groups of micropiles under monotonic or cyclic loading installed in loose sand. The effect of the cyclic loading on the behavior of the micropiles was assessed as well as the effect of the grouting on the improvement of the micropile resistance and stiffness and also on the improvement of the soil mechanical properties. The assembly and procedure of the tests are described and the corresponding resistance and stiffness are presented and compared.

The state of Texas currently produces over 12,000 MW of electricity from wind power (AWEA 2014), accounting for 8.3% of all electricity generated in the state in 2013 (AWEA 2014b). With continually expanding statewide renewable energy goals, Los Vientos, the new wind farm, constructed in Willacy County, Texas, added 402 MW of wind power to the state in 2012. Due to poor soil conditions, ground improvement was required at a number of the individual turbine tower foundation locations. Dry mass soil mixing proved to be an effective method to treat the 26 of the sites that had shallow groundwater. This paper discusses the design, construction, and verification of a dry mass soil mixing treatment program conducted at these sites.

In this study, the preliminary design of suction pile as the supporting system for floating structures has been performed at the offshore pilot project of the southwest coast area in Korea. The suction pile has to satisfy the lateral resistance against external force, as well as the penetration ability according to the soil conditions. In the study, the embedment depths were calculated for the stability of the lateral resistance, in terms of aspect ratio. Also, the design suction pressure was assessed. Finally, the suitable diameter and length of the suction pile has been recommended.

Liquefaction of soil resulting from earthquakes can lead to the failure of structures due to the significant reduction of the foundation bearing capacity. Offshore wind foundations are the type of structures that may be susceptible to earthquake damage. Gravity and Mono-pile foundations are typically adopted for offshore wind turbines in past projects. This study is focused on a new type of group-pile foundation with four legs. A group of centrifuge tests was performed to evaluate the seismic stability of this type of foundation. Acceleration, pore water pressure, settlement, and lateral displacement were recorded to analyze the seismic response of both the upper structure and foundation. Comparisons with test data of other types of foundations were made. Data analysis and comparison shows that this type of foundation has some advantages in improving seismic stability.

A methodology is presented for employing the Deep Foundation System Analysis Program (DFSAP) to predict the performance of an axially loaded drilled shaft. The methodology is evaluated with respect to the outcomes of calculations following the AASHTO LRFD Bridge Design Specification, as well as from Osterberg Cell (O-Cell) load test data. While the AASHTO based design method can be carried out by hand and tends to be conservative, the DFSAP projections are established using the t-z method for axial settlement analysis and have the potential to be more accurate and precise. The procedure presented herein is developed based on an approach used for blind prediction of an O-Cell load test conducted on a 7-ft diameter, 116-ft long drilled shaft in Washoe County, Nevada. The test shaft was a part of the foundation system of a ten-span bridge over the Truckee River in the Reno area. Although the preliminary model achieved an adequate prediction, the formal procedure from this analysis employs updated information about the test shaft as well as a more detailed soil profile to generate a significantly closer fit to the published O-Cell test data.

This paper discusses the probabilistic approach in landfill veneer cover design as well as the impact of variability associated with the design parameters. A framework for the reliability based design optimization methodology as reported in the literature is considered. Conventional deterministic design uses a factor of safety approach that do not cater for these uncertainties that arise due to heterogeneity of Municipal Solid Waste (MSW). The formulation considers a two-part wedge mechanism with the soil-geosynthetic interface acting as the plane of weakness. Random variables considered in the present study are unit weight, cohesion, and friction angle of the cover soil, adhesion between cover soil of active wedge and geosynthetic, and long term design strength of the reinforcement. Generally the long term design strength of the reinforcement (T_D) can be derived from the ultimate value of geosynthetic reinforcement strength by applying reduction factors for chemical/biological degradation, creep, and installation damage. As opposed to the use of conventional reduction factors, in the present contribution, the geosynthetic force required to stabilize the cover soils for the stability is treated as random variable. The mean value of required geosynthetic force is computed for different coefficients of variation of soil-geosynthetic interaction coefficient and ultimate tensile strength of the geosynthetic reinforcement.

During the process of shale gas extraction, water is one of the resources used in order to fracture the formation and retrieve the trapped gas. A portion of the injected water is recovered during the initial extraction of the gas, which is known as flow-back water. Flow-back water was found to contain very high concentrations of dissolved solids (e.g. calcium, barium, magnesium, chloride, and iron), which renders its treatment highly challenging for most of the existing treatment methods. Electrodialysis is an alternative for onsite treatment (or pre-treatment) and recycling of the flow-back water, which has gained more attention in recent years. The method is based on an electrically assisted membrane process for separation of salts from the water. In this study, the efficiency of the electrodialysis as a desalination process for flow-back water was investigated in the laboratory scale using samples of flow-back water from the Marcellus shale gas formation. The preliminary findings indicated a removal of total dissolved solids of between 35% and 90%.

The cohesion and angle of internal friction are generally the key parameters required in the analysis of different geotechnical problems. Variably, expansive soils undergo volume changes when subjected to moisture increase. Accordingly, the attraction forces between the clay particles and the internal friction are deemed to vary for different soil fabrics and different states of stresses. The influence of moisture on the shear strength parameters of clay liners need to be established to achieve adequate design. In this study, undrained direct shear tests were carried out for Al-Qatif clay sand mixtures at variable moisture contents in order to assess the variation of shear strength parameters when sand clay liners are inundated. The mold placement density was maintained the same for all moistures tested. The influence of moisture change on the shear strength parameters was assessed for the material used. In order to forecast the moisture profile in a clay liner, hydraulic conductivity as well as water retention properties was investigated.

Collapsible soils are generally considered to be soils that settle upon wetting and loading. Settlement of collapsible soils is a common problem particularly in arid and semi-arid regions of the United States because these soils exist at very low moisture contents in their natural environment. Locally, geotechnical engineers refer to native soils that settle due to self-weight upon wetting as “collapsible soils” or “hydro-collapsible soils.” This paper presents some observations and findings of a study on natural collapsible granular soils that formed in alluvial fans in central New Mexico. The paper describes the soil structure observed in microphotographs and scanning electron microscope images and the effects of sample disturbance on the prediction of soil collapse upon wetting from laboratory test results. The paper offers a hypothesis on the mechanism that could have produced some features of the structure of the collapsible soils in the area.

Determination of the factor of safety in slope stability problems is a common issue in geotechnical engineering. This paper calculates the factor of safety against failure in a reference case of a levee slope stability considering uncertainty of input parameters. Two different constitutive models are chosen to represent different levels of sophistication to predict soil mechanical behavior and consequently require different levels of formulation complexity. These two models are (1) the Mohr Coulomb model (MC); and (2) the soft soil model in a PLAXIS 2D software. Both models are calibrated to the same reference material (Boston Blue Clay, BBC). The paper investigates the effect of uncertainty regarding the input parameters of the soil model on the level of confidence in the factor of safety by performing a numerical experiment in both drained and undrained conditions. The research shows that in drained conditions, the more sophisticated volume–stress relations in the soft soil model are mobilized resulting in higher variations and less confidence in the factor of safety.

Traditionally, proof-load tests have been utilized to validate design methods and construction procedures. There is currently an inconsistency in the recommendations that are available in pile design codes and practices regarding the required number of proof-load tests and the level of the proof loads. Recently, and in the framework of reliability-based design, researchers have shown that information from pile load tests may have a considerable impact on reducing the probability of failure of piles at a site, thus allowing for the use of lower factors of safety for the piles. This paper presents the results of a thorough investigation that is conducted to study the effect of choosing different proof-load test programs on the reliability of piles. This is achieved by utilizing a Bayesian approach to update the capacity distributions of piles at a site given the results of the proof-load test program. In the updating exercise, an effort is made to update both the mean and the lower-bound capacity to maximize the benefit of the collected proof load data. The significance of the results presented lies in the fact that these results constitute necessary input to any practical decision framework for choosing the number and the magnitude of the proof load test that would maximize the value of information of the test program.

Soil-structure interface systems are encountered in various Geotechnical Engineering projects such as pile foundations, retaining structures, and pipeline infrastructure. The interaction between soil and structures is complex and increases in complexity after movements or failure. Research has shown that residual strength within a soil mass or along a soil/structure interface can increase, yet is difficult to quantify. Also, after structures are installed, the frictional interaction between the soils and the structure tends to increase. This increase has been attributed to many factors including the dissipation of induced excess pore water pressure, soil aging, or the relaxation of the arching effect. Understanding this behavior to be able to predict the amount of increase can significantly improve design and analysis efficiency of many geotechnical and structural engineering projects. A testing procedure has been developed to quantify the change in residual strength over time utilizing a standard direct shear machine. This procedure experimentally quantifies the amount of interface frictional strength increase over time between soil and various types of construction materials. An undisturbed silty, clay soil was tested to determine the changes of interface residual shear strength with time when interacting with steel and concrete plates. The results are consistent with previous experimentation that there is a considerable increase in shear strength as time increases. Also, the increase of shear strength is higher between the soil and concrete than it is with steel.

Open-graded aggregates (OGAs) are commonly used for the construction of roads and bridges due to their ease of construction, lower unit weight, and favorable drainage characteristics. However, their material characteristics are not well understood leading to the common practice of assigning conservative default strength parameters in the absence of testing or basing strength on conventional test methods with scalped samples using either 63-mm triaxial (TX) compression or direct shear tests. The practice of removal of the large grain sizes of OGAs may contribute to under representation of OGA strength. As part of a larger effort by the Federal Highway Administration to characterize OGAs, two of AASHTO M43-05 designated samples having small and large grain sizes were tested at two relative densities in a large-scale (152 mm diameter) TX device under consolidated drained conditions at confining stresses of 34, 69, 138, and 207 kPa. The effect of relative density on strength parameters was significant at all studied stress levels. The computed strength values even at worse case scenarios were relatively higher than the conservative default strength values. The implication is that higher strength values can be used in design. The quantitative information can also be used for improved constitutive modeling.

The design of shallow foundations is becoming an attractive choice for supporting highway bridge structures. The analysis is considered as a semi-empirical methodology that is based on linear and nonlinear models of behavior for settlement prediction. In this paper, the performance prediction methods for spread footing foundations are verified by using compiled field data based on vertical settlements measured on 23 sites of footings for 12 highway bridges selected in Ohio and Northeast of the United States. Six settlement prediction methods are selected for calculation immediate settlement of spread footings on cohesionless soils for each site and compared with measured values of settlement. The settlements of footings in sandy soils are often estimated based on the results of in situ tests. In particular, the standard penetration test (SPT) is considered in this study for all six prediction methods. Statistical parameters corresponding to each of the six settlement prediction methods are evaluated and summarized.

NEHRP guidelines for simplified seismic design provide site amplification factors as a function of the average shear wave velocity (V_s) of the top 30 m of a site, or V_s30. These guidelines are mainly based on experience and observations from the Western United States (WUS), where regional geology is conditioned by frequent tectonic activity. However, the V_s30 value does not capture sharp V_s contrasts due to very hard rock overlain by softer soil, conditions prevalent in the Central and Eastern United States (CEUS), which lead to significant ground motion amplification. Site response analyses performed on CEUS sites have confirmed this inconsistency between NEHRP and calculated amplification factors. This paper presents the development of a model to generate V_s profiles from measurements in the WUS. Parameters such as variation, correlation, and transition frequency of V_s values were defined in order to capture geological trends for the WUS. This same model can then be applied to CEUS V_s profiles and in order to generate groups of V_s profiles representing regional geological trends. From site response analyses using generated V_s profiles, amplification factors can be calculated and compared to verify if region-specific amplification factors should be implemented.

This study investigates the effect of considering anisotropy in correlation structure of random fields on the settlement of shallow foundations. For this purpose, soil Young’s modulus, E, is considered as a random field with an anisotropic correlation structure and stochastic finite difference modelling is conducted with the aid of the FISH programming feature in FLAC 2D. The Monte Carlo simulation technique is then applied to 16 cases of single footing cases, where 1000 realizations are performed on each. For the cases evaluated, it is found that the calculated total settlement results represent a normal distribution. Probabilistic analyses results also indicate that in calculating total settlement and the corresponding mean values, the vertical correlation length is more effective than the horizontal correlation length. Increasing the vertical correlation length and coefficient of variation both increase the calculated settlement. However, changing the horizontal correlation length has a negligible impact on the computed settlement results.

Use of simplified reliability methods in geotechnical engineering has been in practice for several decades. Some of these simplified reliability methods are described in Christian et al. (1994), Tang et al. (1999) and Duncan (2000), among others. These simplified reliability methods include both first-order second moment (FOSM) and first-order reliability methods (FORM). Disadvantages to simplified reliability methods include: (1) an assumption on the distribution of the factor of safety and (2) only the standard deviation and mean of the uncertain variables are used as opposed to the entire probability density function (pdf) (Sleep and Duncan 2014, Polanco and Rice 2011). The perceived disadvantages of simplified reliability approaches and the automation of Monte Carlo simulation into many geotechnical computer programs have caused designers to shift away from simplified reliability approaches in favor of Monte Carlo simulation method. Using the context of stability calculations for unreinforced slopes, this paper compares the results of simplified reliability methods, including the Taylor series, point estimate and Hasofer Lind methods, to Monte Carlo simulation methods. Reliability of modeled slope failures will be compared with Monte Carlo simulation and simplified reliability methods. Additionally, this paper explores the relationship between the uncertainty in parameter values used in stability calculations and the probability of failure.

In this paper, a robust geotechnical design (RGD) methodology is applied to design of rock bolts for slope stabilization. In rock engineering practice, the variation of shear strength characteristics of rock discontinuities is often quite difficult to ascertain. The RGD methodology is utilized to achieve a certain level of design robustness against the uncertainty in the estimated statistics of rock properties, in addition to meeting safety and cost requirements. A multi-objective optimization is used to identify a set of robust designs. The example of rock bolts design for slope stabilization is used to showcase the merit of the RGD methodology.

Bridge scour is the soil erosion caused by water flowing around bridge supports. Research has shown that scour has been the number one cause of bridge failure in the United States with an average annual rate of 22 bridges collapsing or being closed due to severe deformation. In this paper, the authors aimed to quantify the bridge scour risk in order to help people understand how risky the bridge scour is. The widely accepted definition of risk was adopted in the paper, the probability of failure times the value of the consequence. First, the NYSDOT Bridge Failure database and FDOT Unknown Foundation Bridges Database were used to quantify the bridge scour risk. Second, several other societal risks, including cancer, car accidents, and plane crashes, were analyzed to be comparable to bridge scour risk. Finally, the authors proposed the acceptable risk level, medium risk level, and unacceptable risk level in the United States based on the analyses in the paper. The outcome of this paper will aid people or authorities in understanding the risk of bridge failure as well as other society risks.

This paper presents the results of probabilistic analyses in slope stability problems using the Random Finite Element Method (RFEM). The influence of spatially variable soil properties on design outcomes relating to slope stability analysis has been assessed through parametric studies, with focus on the “worst case” (critical) spatial correlation length that leads to a minimum reliability of the soil mass. This critical value is of particular interest, because it could be used for design in the absence of good site specific data.

Due to increased oil demand worldwide, a new trend has been emerging in the offshore oil extraction industry in the Gulf Region. This new approach applies the construction of durable platforms in the form of reclaimed offshore islands. This trend was proven to be feasible solution due to the shallow water depths at oil field locations combined with minor maintenance requirements compared to traditional offshore jacket drilling platforms. However, this new trend came with its own set of concerns, one of which was the estimation of settlement of these platforms under the applied loads. The accuracy of estimating the settlement was therefore studied carefully including the determination of the deformation modulus for the foundation layers including the UCS-E_i relationship. This paper focuses on quantifying and analyzing the variability of two major carbonate rock calcarenite and calcisiltitie formations through the geotechnical laboratory testing results. The statistical analysis of the testing results indicated that a 2nd degree polynomial relationship can be developed to link the UCS with E_i. The proposed relationship in this paper should provide a more accurate tool for assessment of the E_i value compared to the mostly linear correlations currently reported in literature for these local formations.

Proof load tests measure the capacity of piles and are commonly used to confirm the design capacity of the piles has been achieved. The statistical reliability of the pile foundations can also be updated based on these test results. Low factor of safety can be used in the design stage if a certain number of tests will be performed. Research has been previously conducted on updating the mean capacity of piles. This paper develops new methods for updating the capacity of individual piles. It provides directly the updated population parameters, which can be used to predict the reliability of another pile in the same site.

The technique of borehole-based full waveform inversion (FWI) using a regularized Gauss–Newton method has been developed to provide high-resolution velocity images along and around a borehole at depth and within a socket proposed for use in the design of a drilled shaft foundation. The capability of the proposed imaging technique has been demonstrated through comprehensive synthetic model studies. Accurate 3D borehole models and axisymmetric borehole models were both formulated using ABAQUS, and the regularized Gauss–Newton method proved to work well for time-domain FWI within a borehole. High nonlinearity of FWI coupled with a downhill optimization scheme requires a reasonably good starting model to avoid local minima, thus, the strategies of frequency filtering and temporal windowing were adopted to improve convergence. The proposed imaging technique is capable of delineating earth models that are either horizontally or cylindrically multi-layered. It is also capable of locating ring-type anomalies at various distances away from the borehole wall, embedded inside a homogeneous or a layered background. Despite the fact that the forward model is axisymmetric, the proposed imaging technique appears to be capable of finding indications of isolated anomalies in the vicinity of a borehole.

Surface wave techniques for soil characterization have undergone significant development over the past several decades. Herein, a new generation of techniques is compared against traditional methodologies at a test site in Florida. In particular, data from active-source MASW, a new non-uniform active-source array, ReMi, and two dimensional (2D) passive-source arrays are compared. A non-uniform linear array of receivers together with a small vibration shaker significantly improves the resolution of dispersion curves as compared to conventional multi-channel sledgehammer source arrays, particularly at low frequencies. To evaluate dispersion images at the lowest frequencies, passive-source arrays were conducted. Comparing dispersion curves at frequencies that overlapped, the phase velocity estimates from ReMi were low, whereas non-uniform array active-source and 2D passive-source methods produced similar results provided modifications are made to account for near-field effects. Inversion of the combined dispersion curve from a non-uniform active-source array and a 2D passive-source array yielded a significantly deeper shear wave velocity profile for the site than produced in a previous study using dispersion data from a sledgehammer source uniform array and ReMi.

Shear wave velocity of granular materials is often measured by bender elements in laboratory to determine its engineering properties. However, the accurate interpretation of measured wave propagation can be challenging which requires better understanding of bender element and soil particle interactions, and shear wave propagation in granular materials. In this study, bender element tests were performed on three granular materials: silicate and glass sphere beads, and ASTM fine graded sand. These bender element tests are simulated with discrete element method using software PFC3D. The DEM models were calibrated with the physical laboratory tests. The results from DEM simulations are useful to identify shear and compression wave propagation and to improve interpretation of the receiver signals.

Foundation failure due to liquefaction induced by earthquakes is a major hazard that causes casualties as well as significant damage to the buildings. Based on some previous research and studies, anisotropy of the fabric of soil grains plays an important role in dynamic soil response. However, there are few data recorded during earthquakes in the field about seismic response of foundations, let alone realistic ones that can be used to analyze the influence of soil anisotropy. In this study, twelve centrifuge tests were conducted to investigate the influence of soil anisotropy on seismic response of foundations.

Image-based vibration measurement is a cost-effective way for remote monitoring of transportation structures as well as other structures, especially for situations where accessibility is restricted which does not allow installation of conventional monitoring devices. The technical bases of video-based remote vibration measurement are digital image analyses. Comparison of the images allows the field of motion to be accurately delineated. Such information is important to understand the structural behaviors including the motion and strain distribution. This paper presents a case study to estimate the velocity field of a vibrating pole captured in image sequences. Three different methods (i.e., Particle Image Velocimetry, Frame Difference Method, and Optical Flow Method) are utilized to analyze the image sequences to extract the feature of motion. The performance of these methods are compared. The results indicate that all three methods can estimate the velocity field of the target, although the results can be affected by factors such as background noise and environmental interference. Optical flow method achieved the best performance among these three methods studied. With further development of system hardware and image processing software, it might be possible to develop a remote video based monitoring system for structural health monitoring of transportation infrastructure to real time determine the velocity field and strain distributions.

Deformational properties of organic-rich shale formations control the success of hydraulic fracturing process, and affect transport properties during production. Usually, these deformational properties cannot be captured by geophysical techniques, which can only measure elastic properties. The relationship between ductile deformation and elastic properties of the shale formation are of significant importance. In order to investigate this relationship, laboratory experiments were conducted on shale gas samples taken from a Marcellus outcrop at State Game Lands 252, located in Lycoming and Union counties, Allenwood, Pennsylvania. Laboratory results indicate that creep behavior is significant in the shale samples. Also, close agreement between experimental and power law model results for creep behavior of shale samples were found.

In the current research, the main concern is to verify the behavior of gravelly soils. To that matter, with taking use of CU triaxial tests and variations in parameters of interest, gradation, relative density, isotropic pressure and anisotropy of consolidation during the tests, the effects on the steady state condition and monotonic liquefaction of gravelly soils are investigated. The test results indicated that as the isotropic pressure increases, percentage increase of steady state strength resulting from the increase of relative density will decrease. Moreover, with the increase of anisotropy of consolidation, the effect of relative density on steady state strength and built-up pore water pressure decreases. Among the tests, the specimen with 60% gravel content, 0% initial relative density, the confining pressure of 100 kPa showed a behavior similar to monotonic liquefaction. The test results also indicated that with the decrease of gravel content and isotropic pressure and the increase in the initial relative density, anisotropy of consolidation coefficient, that is, , as a result, will be proportional to steady state strength.

Geomechanical properties of rocks are important parameters in the design procedure and construction of various geotechnical projects such as underground excavation, rock slope stabilities, and blasting in rock medium. These parameters have also wide applications in the mining industry since they are employed in the rock mass classification of coal mine roofs and roof control design. The strength indexes of the rocks are affected by changes in their moisture contents. Understanding of this correlation for rock medium is critical for mining companies during mine development. In this paper, an extensive database containing geomechanial properties of three different rock units including shale, limestone, and claystone is developed by collecting and performing tests on roof core samples of a coal mine in the Illinois Basin. These properties include moisture content, unit weight, unconfined compressive strength, indirect tensile strength index, axial point load index, diametral point load index, and slake durability index. In this study, a correlation between moisture content and strength of examined rock samples is investigated. It is also discussed how the results could affect the timing for the development of mine panels, keeping the main entries open and dealing with moisture sensitive rocks during the mining activity.

Reliable rock mass characterization is needed to design safer and more economical roof support systems of coal mines. Coal Mine Roof Rating (CMRR) index is a commonly used method by roof control engineers to characterize immediate rock units above the underground coal mines. This index ranges from 0 to 100 and was developed by studying the performance of the roofs in the Appalachian coal fields, which have typically strong roof units. Application of CMRR for weak and moisture sensitive rocks such as shale roof units in the Illinois Basin may misrepresent the rock mass. In this study, the rock laboratory test results are conducted to characterize the moisture sensitivity, axial and diametral strengths of roof units. The CMRR indexes and designed roof systems in a coal mine located in Illinois Basin will be presented. A sensitivity analysis is also performed to identify the most influential CMRR rock mass characterization parameters in weak rocks. This study shows while CMRR rock mass characterization has many advantages, it should be cautiously used for roof support design in weak and moisture sensitive roof conditions.

Over a period of several thousand years, the Mississippi River shaped what is today’s southeast Louisiana. This area was formed by sediments deposited by the Mississippi River and its tributaries, mostly during the flooding months of the year. However, since 1932, more than 66,000 acres of marshland have disappeared and been converted to open water; this amounts to more than 22% of the marshland that had existed. The primary causes of wetland loss are attributed to increased human activities leading to global climate change and sea level rise, increased number and intensity of hurricanes and storms, and regional subsidence that started many hundreds of years ago. Subsequent human activities such as the construction of levees and flood protection systems along the banks of Mississippi River have minimized the supply of fresh water, sediment, and nutrients. The river, restricted by these structures, has deposited this material into the Gulf of Mexico; material that once naturally replenished coastal wetlands. Over the last several years, a major goal towards reestablishing a healthy coastal ecosystem has been to rebuild land with diverted sediments from the Mississippi River or with dredged sediment conveyance projects. The engineering properties and material characteristics of the dredged material are input parameters in several mathematical models that have been used to predict the long-term performance measures of restoration projects. Therefore, proper characterization of the dredged sediments is of utmost importance in the correct design of coastal restoration and land building projects. This paper presents the results of laboratory tests performed on dredged sediments obtained from actual coastal restoration projects in different geographic locations within Louisiana. The effects of salinity, sediment grain size-distribution, and particle concentration, on the settling characteristics of the dredged slurry are discussed.

Suction-controlled triaxial tests have been widely used to characterize unsaturated soil behavior for the constitutive modelling purpose. This type of tests requires sophisticated and therefore expensive equipment, is time-consuming and unreliable, and cannot be justified for routine engineering projects. In comparison, suction-controlled odometer tests require much simpler testing equipment. Due to the smaller specimen thickness, the time needed for dissipating excess pore water pressure is about 10 times less. However, the stress path of a soil during odometer test is not clear since the lateral stress is unknown. At present, there is no method available to analyze the odometer test results for constitutive modeling purpose. This paper presents an analytical method to use results from odometer tests for constitutive modeling purpose. An example is used to demonstrate the effectiveness and simplicity of the proposed method from which some conclusions are made.

In the past, full-field deformation of unsaturated soils during triaxial testing has never been reported due to lack of a measurement method. In this paper, a photogrammetry-based method was presented to investigate the deformation of an unsaturated soil during triaxial testing. Measurement targets were attached to the surface of an unsaturated cylindrical specimen. With the newly developed photogrammetry-based method, the three-dimensional coordinates of these targets are accurately determined to monitor soil deformation during triaxial testing. Soil deformation non-uniformity was extracted based on the movements of those measurement targets on specimen surface. It was found that an unsaturated soil deformation under shear load was not uniformly distributed.

The co-existence of networks of liquid bridges and saturated pockets in partially saturated soils yields complex soil behavior. Attempts have been made to understand the evolution of liquid bridges and pockets under changing suction conditions in soils. Analyzing the evolution of inter-phase boundaries and quantifying interfacial contact angle can be cited as one example. However, to date, the lack of technological developments that enable microstructural observation has impeded the results of such efforts. This study utilizes advancements in the field of nondestructive testing and applies X-ray micro Computed Tomography (X-ray micro-CT) to investigate the evolution of contact angle. A partially saturated granular specimen is prepared and scanned under controlled suction conditions. Three dimensional images of interphase microstructure are acquired and processed with digital algorithms. The evolution of the liquid-air and solid-liquid interfaces is tracked from 3D images obtained with phase-based segmentation. Interfacial contact angles are measured on orthogonally projected images and values are reported.

Vertical moisture barriers have the potential to stabilize the moisture variations beneath covered areas (e.g., pavements, slab-on-ground foundations, etc.) in response to surface moisture flux boundary conditions, and can affectively be used in controlling the volume changes of expansive soils with wetting and drying cycles. However, vertical cracks formed outside the boundary of the covered area are pathways for moisture intrusion or escape depending on the weather cycle, and can significantly influence the moisture regime beneath the covered area. The paper analyzes the influences of the depths and locations of outside cracks on the distribution of suction and vertical displacement by finite element method. It is found that the performance of vertical moisture barriers can significantly be diminished with the presence of cracks. An outside crack with enough depth can completely counteract the benefits of moisture barrier. Also, how to determine the dimension of horizontal moisture barrier is discussed.

Reliable design of pavement base-course is possible by taking account the variation of resilient modulus (M_R) with respect to suction using mechanistic design methods. In this paper, a semi-empirical model is proposed to predict the M_R-suction relationships for base-course materials using the soil-water characteristic curve (SWCC) as a tool. The proposed model is validated by providing comparisons with the experimental results of four base-course materials. The approach proposed in this study is simple and can be used in the rational design of pavement base-course extending the mechanics of unsaturated soils.

High plasticity clays exhibit extensive volume change behavior when subjected to seasonal moisture fluctuations. Shrinkage induced pressure evolved during the drying process could result in moderate to severe damage to light infrastructures. Tensile strength and stress evolved during drying process will result in soil cracks when the later exceeds the former. A novel method is introduced in this research to effectively identify and study shrinkage induced pressure (SIP) of expansive clays. In this study, highly expansive Colorado soil is subjected to drying in a temperature controlled environment. A data acquisition system capable of continuously recording shrinkage induced pressure is utilized. The rate of soil drying, initial soil moisture, and sensor capacity is some of the variables addressed in this study. A comparison of SIP test results with indirect tensile strength (IDT) results was conducted in order to validate the test results.

Dynamic properties of soils including small-strain shear modulus (G_max), shear modulus reduction function (G/G_max), and damping (D) are affected by changes in the degree of saturation. Inter-particle suction forces in partially saturated soils result in higher effective stress values, which in turn, vary the dynamic soil properties. These alterations could lead to different wave propagation mechanisms, acceleration amplification patterns, and seismically induced settlements. This paper aims to identify the challenges involved in nonlinear seismic site response analysis of partially saturated soils by looking at the response of 10-m sand and silt layers with different constant suction profiles. A set of frequency domain equivalent linear and nonlinear site response analysis under scaled Northridge earthquake motion was performed. A modified version of Bishop’s effective stress equation for partially saturated soils has been utilized to calculate the dynamic soil properties (i.e. G_max, G/G_max, and D). Specifically, surface-to-base intensity amplifications (Peak Ground Amplifications and Arias Intensities), spectral accelerations, and lateral deformation profiles of the sand and silt layers with different suction profiles were generated and compared. The insight gained from this study was used to plan and design more complex nonlinear Finite Element site response analysis.

Triaxial testing of unsaturated geomaterials under suction-controlled conditions can be accomplished via either axis-translation technique, typically for matric suction values up to 1500 kPa; or the vapor-equilibrium technique, which allows for control and measurement of total suction at significantly higher values. In either case, empirical assessment of a suitable shearing rate depends essentially upon the nature of volume change and stress–strain response of the test soil during shearing. The main objective of the present work was to empirically assess the appropriate strain rate for drained triaxial testing of intermediate geomaterials in the higher total suction range. To accomplish this goal, a series of suction-controlled conventional triaxial compression (CTC) tests were conducted on statically compacted specimens of silty sand, at five different shearing rates, under a constant, vapor-induced total suction of 300 MPa (300,000 kPa). Total suction was controlled, prior to and during the shearing stage, via a fully automated relative humidity (RH) chamber assembled to a newly implemented, double-walled triaxial apparatus. The critical state based criteria for assessing the appropriate shearing rate at higher total suction values are compared and discussed over a wider range of induced suction states. In addition, observations pertaining to particle breakage and soil dilatancy phenomenon, associated to triaxial shearing at higher total suctions, are also discussed.

Service learning (SL) is a teaching and learning approach that couples service to a community partner with academic learning for students. Often the objectives of SL courses include academic or technical enhancement, civic engagement, and development of personal and interpersonal skills. A key component of SL is critical reflection, which is expected to help the students understand the significance of civic engagement as well as course contents. The civic engagement aspect of this educational approach aligns well with the service-oriented nature of the civil engineering profession. SL projects have been conducted in the civil and environmental engineering capstone senior design course at the University of Vermont since 2006. Students submit written semi-guided reflections on their experience at the conclusion of the course. The student reflections from 2011 through 2014 (n = 154 male and 61 female from a total of 50 different SL projects) were analyzed to assess if there is any difference in the attitude toward SL between male versus female students. The results of this analysis are presented here.

A team of geotechnical engineering faculty and students and educational technology faculty and students worked together to develop, pilot test, and disseminate learning materials in unsaturated soils for undergraduate geotechnical engineering courses. The eventual goal of the team is the institutionalization of this learning material. The geotechnical engineers served as the subject matter experts and were the primary resource for the content. The educational technology team members’ primary responsibilities were the development of materials and evaluation of the material’s effectiveness. Faculty resistance to change was another issue addressed. The educational technology team members assisted with the flexibility and seamlessness of the material into current undergraduate geotechnical engineering classes, thus lessening the resistance. This paper will emphasize challenges encountered in working with those outside of their own field of expertise, in this case, the interdisciplinary design team. Qualitative data in the form of notes, design logs, and surveys and interviews will show the challenge of learning new curriculum (educational technology) and/or methods (geotechnical engineers). Learning new material without the background knowledge and dealing with unfamiliar research methods and regulations are dominant themes. In the development of the curriculum material, established guidelines were followed. When a diverse team from different backgrounds is involved, it may benefit the team if some additional steps are taken at the initial stages. One major recommendation is that the team establishes roles and expectations for each member early on and leaning objectives for the learning materials.

To adequately prepare students for engineering practice, innovative methods of teaching, learning and assessment are required to facilitate development of adequate problem-solving skills. Emphasis should be placed on facilitating higher levels of learning and developing a systematic approach to problem solving as this helps students make the connection between theory and practice. The authors discuss the problem solving approach implemented using project based learning and case studies in two upper level undergraduate civil engineering courses at the United States Coast Guard Academy. Assessment data indicate that students gained more confidence solving engineering problems and were engaged at a higher level of learning and understanding of engineering principles. Student performance on capstone projects was noticeably improved due to the problem-solving skills developed in earlier courses.

While an instructor may not be able to control the diversity present in their classroom, what is under their control is the way in which this diversity is addressed. On certain levels general characteristics, such as an emphasis on respectful attitudes for example, can provide overarching support for all students. From a learning perspective however, the recognition of multiple learning styles may require a more specialized approach to ensure that benefits can be realized by everyone in the classroom. This paper will consider these learning styles from within both an introductory soil mechanics course, as well as an upper level geotechnical engineering design course. Additionally, the inclusion of several of AAC&U’s High Impact Practices such as writing intensive courses, collaborative assignments and projects, undergraduate research, and capstone projects that have shown to have a positive impact on diverse student populations and have been applied in these courses will be described.

The inability of the geotechnical engineering profession and individual institutions to create systemic equality in culture, outcomes and representation for women faculty results in persistent and severe isolation. This isolation generates a tandem set of challenges that directly impact the recruitment, retention and career success of women faculty. Current data sources indicates that approximately 11% of national geotechnical engineering faculty are women compared to sister disciplines such as structural engineering which range from 15% to 17%. Furthermore, over a third of the US research one universities with geotechnical engineering programs have no women faculty and only 1 out of 10 have two or more. These figures paint a clear and precarious picture of the isolation and underrepresentation which also contributes directly to the pipeline problem; fewer women entering and completing their education at the bachelors, masters, and doctoral levels. Given these numbers, retaining women faculty who have carved successful careers in geotechnical engineering is of even greater importance for the profession. The inclusion, advancement and resilience of women in geotechnical engineering require enduring support, professional development, and systemic change. This paper will examine the contemporary history of professional development at the national level for women in geotechnical engineering and the obstacles and challenges they face. In addition, future programs and strategies to recruit and retain women will also be discussed.

Amongst the many challenges that engineering education faces today, is the need for faculty to update their teaching skills, and continue to learn new approaches to teaching and learning, which in turn requires effective professional development for both new and experienced faculty alike. This paper focuses on “viable teaching-learning” strategies for potential adoption by engineering educators, strategies pertaining to: (i) planning courses, (ii) conducting courses, and (iii) developing positive learning environment, in and outside the classroom, are explored and supplemented with suggestions based on the experience of the author. It is also argued that colleges of engineering would excel at teaching and learning when the majority of the faculty develop and achieve a reasonable level of professional pedagogical knowledge. Engaging students in learning is primarily the responsibility of the instructor who must take necessary steps to improve his/ her skills of effective teaching, including the use of cooperative learning in particular. Also, students’ varied learning styles ought to be recognized and addressed. For the reforms in engineering education to be enacted, the culture of engineering colleges has to evolve to the point where the changes advocated would be reinforced by an explicit set of expectations, a support structure, and a compatible faculty reward system.

Rigid inclusions are used to improve the load-bearing capabilities of poor soils. The construction procedure for grouted rigid inclusions in the field involves displacement of the soft soil producing changes in pore-water pressures, and as a result, changes in effective stresses in the immediate vicinity of these elements. A numerical study was performed to examine the post-construction changes in the installation-induced stresses and pore-water pressures around the rigid inclusions. The finite element software PLAXIS was used in the numerical analysis. The soft soil is modeled as a linear elastic perfectly plastic Tresca material. Cylindrical cavity expansion is implemented in the finite element models to represent the rigid inclusion construction process. The results indicate that the installation-induced stresses in the vicinity of the rigid inclusions expressed in the form of earth pressure coefficient K, increase with the dissipation of excess pore-water pressures.

In this study, the smear zone due to vertical drain installation is studied using a large, in situ sample to capture the realistic characteristics of the smear zone in relation to the in situ soil structure. The smear zone extent for Bulli clay (New South Wales, Australia) is quantified on the basis of normalised permeability and the reduction in the water content prior to consolidation. The permeability and compressibility of the soil are used to determine the extent to which the soil surrounding the PVD had become disturbed. In laboratory testing, the soil consolidation behavior due to a prefabricated vertical drain (PVD) is studied using a large scale consolidometer apparatus.

Geotechnical characterization of soils typically relates to the macroscopic description. This is because properties at the macroscopic scale directly relate to the behavior of soils and the performance of built infrastructure. In this presentation, attention will be drawn to the microscopic characterization of sand grains, which is believed to be very important in determining the causes of time-dependent behavior of silica sand. In particular, the morphology of the sand grain surfaces will be characterized using Scanning Electron Microscopy and Atomic Force Microscopy. When particles with rich surface morphology come into contact, the prime response is fracture. However, after initial damage (fracturing and crushing), fracturing continues for days. This has been found in tests where a single contact between two grains was subjected to a sustained load. The process of the time-dependent interaction between two grains subjected to a contact load will be referred to as contact fatigue. The physics underpinning, this process is sought in the rate process concept, applied to fracture kinetics. Quantitative results from testing individual contacts and from tests on specimens of silica sand will be presented. An attempt is made at explaining a peculiar behavior of silica sand deposits after in-situ dynamic compaction.

Microbial induced calcite precipitation (MICP) is a novel ground improvement method to increase strength and stiffness of sand using natural biogeochemical processes. Cementation level and confining pressure are two important factors that control the behavior of MICP sand. The static mechanical responses of MICP cemented sand are systematically investigated using four cementation levels (untreated, lightly treated, moderately treated, and heavily treated) and three levels of confining pressure (100 kPa, 200 kPa, and 400 kPa). The experimental results indicate that the improvement in shear strength parameters is dependent on the level of cementation under peak and residual states. Uniformity of MICP cementation in laboratory scale is also discussed. When comparing the response of MICP sand with naturally cemented sand and artificially treated sand with portland cement, the MICP cemented sand is observed to better capture the small strain stiffness of the naturally cemented soil.

Columns of improved soil created by Enzyme Induced Carbonate Precipitation (EICP) offer the potential for non-disruptive, cost effective ground improvement for a variety of geotechnical purposes. EICP employs urease enzyme to precipitate CaCO₃ from an aqueous solution of calcium chloride and urea to fill the soil pores (increasing dilatancy and reducing compressibility) and cement soil particles (increasing shear strength). EICP is similar to Microbially Induced Carbonate Precipitation (MICP) except that, instead of employing microbes to generate the urease enzyme, the enzyme is obtained from agricultural sources. A major advantage of agriculturally-derived urease compared to microbial urease is its small size and water solubility, which allows penetration through the pore throat of finer grained soils such as silts, whereas ureolytic MICP is essentially restricted to soils of fine to medium sized sand or larger. The small size of the enzyme can also mitigate the potential for bio-clogging due to carbonate precipitation and biofilm formation, both of which my limit the applicability of MICP. Bench top tests in the laboratory show that cemented columns of soil can be created by infusing a cementation solution through a perforated tube or pipe or by mix and compact methods. EICP columns can be installed in patterns similar to root piles (pali radicii) for slope stability, micro piles for foundation support, and stone columns or soil cement columns to support embankments and restrict lateral spreading in liquefiable soils. Furthermore, EICP piles could be installed under existing structures without causing heave or settlement, making them ideal for remediation of poor (e.g. liquefiable) foundation soils.

Ground improvement of marine clays is the most inventive field of geotechnical engineering. Various techniques such as use of prefabricated vertical drains (PVDs), vacuum consolidation, stone columns, etc., are available for improving the mechanical and engineering properties of the marine clays. In the present paper, the use of PVDs with preload for improving the soft marine clay that support the sub grade of state highway No. 54 from Panvel to Uran at Mumbai, India is studied. The 3.25 km stretch of marine clay was present up to a depth of 12–15 m. As the road connects to the Jawaharlal Nehru Port (India’s major hub port) road, heavy traffic is expected to be moving through this road. Staged embankment construction of 4.30 m height with PVDs was employed to sustain the heavy vehicular traffic load and to reduce the post-construction settlement. A total of 650 thousand running meter PVDs were installed at a spacing of 1.20 m. The 4.30 m high preload was kept in stages for a period of 6 months. Various instruments were installed to monitor the pore water pressure, settlement, and lateral displacements. The substantial settlement of 636 mm was achieved during this period.

The site available for construction of new clean air environmental controls equipment at an existing electric power generating plant proved problematic, with 10.5 to 12 m (35 to 40 ft) of very loose, coarse granular fill underlain by 1.5 to 3 m (5 to 10 ft) of soft sediment, overlying competent residual soils and bedrock. While most structures would be supported by rock bearing drilled shafts, subsurface conditions presented challenges for shallow foundations, as well as seismic design requirements given a Site Class F designation. The need for ground improvement was identified early in the project to improve the seismic site class, reduce liquefaction potential, and reduce potential settlement of shallow foundations, while accommodating the installation of drilled shafts. Initially, compaction grouting was selected as the preferred alternative. A compaction grouting test program over a portion of the site was conducted, but the success of the grouting program was marginal and inconclusive at best. Alternate ground improvement methods were solicited in site improvement bids, and the use of 400 mm (16-in) diameter cast-in-place grouted elements (CGEs) was selected. CGEs were to be installed to the depth of bedrock on a spacing of 2.4 m (8 ft) center-to-center, “split-spaced” with CGEs that only went to the bottom of the granular fill, or a depth of about 12 m (40 ft) using reverse-auger techniques in an attempt to densify the granular fill between each element. A soil-cement load-transfer pad was constructed to distribute the fill and slab loads to the CGEs, and the site was raised to finished subgrade through the placement of compacted fill. CPT soundings, both conventional and seismic, were used to assess the improvement in soil density between the CGEs. While the ground improvement program was ultimately deemed successful, and the goals of the project were achieved, the interpretation of CPT soundings and assessment as to the effectiveness of the ground improvement program proved to be a difficult task.

Microbial denitrification or dissimilatory reduction of nitrate offers the potential of a sustainable and cost-effective method for mitigation of earthquake-induced liquefaction. Carbonate precipitation via microbial denitrification is a slow process and may take years to precipitate enough carbonate to provide the desired degree of mitigation. Fortunately, large amounts of nitrogen gas are generated immediately upon the onset of denitrification. As desaturation by biogas generation is itself a liquefaction mitigation mechanism, liquefaction mitigation via microbial denitrification may be viewed as a two-phase process: an initial phase wherein desaturation via biogas generation provides mitigation and a second phase in which sufficient carbonate precipitation has occurred to provide mitigation via particle cementation and/or an increase in dilatancy. Microbial denitrification is suitable for remediation under and around existing facilities because it is non-disruptive. An advantage of microbial denitrification compared to hydrolysis of urea (ureolysis), another technique for microbial precipitation of carbonate, is that its primary by-products are benign (non-toxic). Another advantage of microbial denitrification is that denitrifying bacteria are ubiquitous in the subsurface. Laboratory test data demonstrates the ability of microbial denitrification to both desaturate the soil and induce carbonate precipitation, leading to an increase in strength and dilatancy, substantiating the concept of microbial denitrification as a two-phase process for mitigation of earthquake-induced liquefaction.

Permeation grouting can be an effective way to deliver bentonite into porous media to control ground water flow. Bentonite slurries can be permeated into the porous media to reduce the hydraulic conductivity of the original soil. While some work has been done on the change in hydraulic conductivity of the soils when introducing bentonite, the stability of the bentonite within the pore space has not been significantly investigated. The current paper presents a study on the post-grouting stability of bentonite grouts within a porous media. The performance of bentonite grout in permeated sands was investigated by studying the rheological properties of bentonite suspensions (particularly, yield stress) and stability of the ground under in situ hydraulic gradients. The rheological parameters of bentonite suspensions were measured at various bentonite concentrations (ranging from 6 to 16% bentonite to total weight) with and without sodium pyrophosphate (SPP) modifications (SPP percentage ranged from 1 to 11% by dry weight of bentonite). SPP is an ionic additive used to temporary control the rheological properties of the bentonite grouts. The stability of bentonite grout was inspected by studying the hydraulic conductivity of sand permeated with bentonite suspensions under increasing hydraulic gradients; when washing out occurs, it results in an increase in hydraulic conductivity. The critical hydraulic gradient at which washing out of bentonite suspensions is initiated was examined. Accordingly, a relation between the yield stress of bentonite suspensions and the critical hydraulic conductivity is developed.

Soil improvement is commonly used in regions with seismic hazards to mitigate soil liquefaction and lateral spreading. Design evaluations must consider the mechanism of improvement (e.g., densification, reinforcement, and/or drainage) mitigating excess pore pressures as well as increases in stiffness of the improved ground. Despite its importance, the change of small strain stiffness of a site following treatment has received little attention. Measurements of post-improvement shear wave velocity are uncommon, and it is unclear whether or not the improved site stiffness can be accurately estimated before improvement. This paper presents a case history of ground improvement for liquefaction mitigation of silty sands, and includes surface wave measurements for determination of shear wave velocities of layered, unimproved and vibro-stone column-improved soils. Following the comparison of pre- and post-improvement in situ tests, the effect of the increase in stiffness on the site response analyses determined with equivalent linear approaches is evaluated. Several methods were used to assess the increase in site stiffness, ranging from area replacement-based estimation approaches to the shear wave velocity measured following improvement. The accuracy of the analyses following common estimation approaches is compared to the analyses using the measured values and recommendations for the evaluation of site response are provided.

Geosynthetic encased stone columns have the potential to contribute to the stability of soft clay deposits under embankments; however, there is a need to quantify the degree of this contribution. To evaluate this contribution, a two-dimensional finite difference method was used to investigate the effect of geosynthetic encased stone columns on the factor of safety of deep-seated slope failure of an embankment constructed over a soil deposit under the short-term condition. In this study, the effect of columns was evaluated using two different models with column walls and an equivalent improved area. A parametric study was conducted using these models to investigate the influence factors that may have a direct impact on the factor of safety, including the spacing and size of stone columns, cohesion of the soil deposit, and stiffness of geosynthetic. The results of this analysis are presented in several charts.

Chemical improvement techniques are used to increase strength and decrease deformability of soils. Addition of cement slurry changes the engineering properties of soft clays. In this paper, laboratory test results of an unimproved soft clay are compared with those of cement-improved samples. Laboratory testing of these specimens included one-dimensional consolidation testing and undrained triaxial compression, extension, and cyclic loading tests. Results of the laboratory testing show a change in the stress-strain behavior of the material due to the influence of the cementitious bonds formed during the improvement process. An indication of the strength of these bonds was estimated by determining an “apparent pre-consolidation pressure,” via the Casagrande method from the one-dimensional consolidation test results, and an artificial stress history was observed. Due to the range of triaxial confining stresses used in this study, all of the laboratory-improved soil triaxial test results exhibited behavior similar to those of heavily overconsolidated clays including high initial strength and dilation behavior.

Microbial induced calcium carbonate precipitation (MICP) has attracted attention as a sustainable means of soil improvement in recent years. Sporosarcina pasteurii is widely used in the MICP process for laboratory experiments due to its highly active urease enzyme. Although the process can bond around loose sand and improve the engineering properties of sand, it is difficult for cementation media (urea–CaCl₂ solution) to fully contact and react with the bacteria inside soil sample through pores of sand, and the calcium carbonate precipitation formed on the soil sample surface always clogs the pores during the MICP process. In this study, a full contact flexible mold was developed for a more uniform calcium carbonate precipitation in the soil sample during the MICP process. The new sample preparation mold provides supports for the bacteria to grow through fully contact cementation media and induce the calcium carbonate precipitated homogeneously within the pores of the sand. The development of the full contact flexible mold was described. Different size specimens were prepared using the full contact flexible mold to evaluate engineering properties improved by MICP treated soil. Direct shear test and unconfined compressive strength results showed that the improvement of MICP treated soil with full contact flexible mold is one-order of magnitude higher than that of the typical sample preparation method.

This paper describes the centrifuge model construction procedure for a soft clay profile reinforced by soil-cement grids and presents the results and observations of seismic site response during a preliminary dynamic centrifuge test. These tests are the first in a series of centrifuge tests investigating the stiffening effect of soil-cement grid reinforcement on the seismic response of soft clay sites. The results showed that for high intensity base motions, soil nonlinearity reduced the soil peak horizontal acceleration (PHA) in an unreinforced soil profile, while in a reinforced profile, the surface PGA was greater than the base peak acceleration. The soil-cement grid with A_r=30% and improvement depth/grid spacing = 0.7 did not help reduce the induced excess pore water pressure and settlement in the surrounding soil. However, the settlement of the soil-cement grid was significantly smaller than the surrounding soil settlement.

The effective reuse and recycling of industrial byproducts, namely coal wash (CW) and basic oxygen steel slag (BOS), through large-scale geotechnical projects (e.g. land and port reclamation) is economically beneficial and environmentally sustainable. Nevertheless, due to the heterogeneity of these granular waste materials, the actual performance of compacted fill in the field can be significantly different from that observed in the laboratory. This paper reports the results of a compaction field trial carried out at Port Kembla Outer Harbor reclamation site (Wollongong, Australia) to evaluate the in situ performance of two selected CW-BOS blends. Based on a number of field density tests, it was found that 4 passes of compaction were adequate for achieving a fill density > 90% standard Proctor compaction. A series of dynamic cone penetration tests (DCPTs) confirmed that compacted CW-BOS fills have a greater strength compared to compacted sandy fill, as the number of blows to penetrate 100 mm is greater than 20 for both materials. Furthermore, plate load tests were also performed and swelling was routinely monitored. The results are presented and discussed.

This paper describes an extensive mass soil mixing and stone column ground improvement program conducted for the expansion of a taxiway and runway at Fort Lauderdale-Hollywood International Airport in Fort Lauderdale, Florida, USA. The expansion, currently under construction, required a total elevation change of up to 18.3 m (60 ft) over the 2,438.4 m (8,000 ft) long, 45.7 m (150 ft) wide expansion to allow planes to traverse over US 1 and the Florida East Coast railroad tracks, and the airport’s perimeter and entrance roadways. The project includes a complex system of mechanically stabilized earth (MSE) walls, cast-in-place walls, and embankments to support the new taxiway and runway. A shallow organic layer and deeper pockets of organic soils underlie the bridge abutments and MSE walls on the project’s east side. Placement of embankment fill would produce excessive deformation and instability issues within the underlying organic and loose soils unless these soils were treated prior to construction. The design-build solution included nearly 152,911.0 m³ (200,000 yd³) of mass soil mixing and over 3,000 vibro replacement (VR) stone columns to depths up to 9.1 m (30 ft). The solution reduced settlement and increased stability for all treatment areas. This paper presents project design, execution, verification testing, data acquisition, and post-improvement performance.

One of the most comprehensive ground improvement projects was designed and built for prime waterfront lots located in Southern California within a high-risk seismic area with extensive environmental restrictions. The site’s subsurface materials consist of an uncertified fill underlain by layers of alluvial deposits resting on the volcanic formation. Site investigations identified four geotechnical challenges: (1) potential of uncontrolled differential settlement due to uncertified fill; (2) liquefaction potential of the fill and alluvial deposits; (3) potential lateral spreading; and (4) potential consolidation settlement of cohesive soils under the planned building load. To meet the tight construction schedule and the stringent performance criteria, a combined ground improvement program, including wick drains, dynamic compaction (DC), surcharge, and soil mixing buttress walls along the shoreline, was developed to address all geotechnical hazards. Instrumentation and construction monitoring played a vital role in meeting the design specifications, including providing an improved understanding of strength, deformation, consolidation characteristics, and liquefaction potential of the foundation soils. This paper discusses the design, instrumentation program, and how performance monitoring was implemented to control construction processes and improve the geotechnical design.

Since several decennia, the deep mixing method has been used to improve the strength and deformation characteristics of soft soils. A more recent trend is the use of this technique for the construction of soil mix walls designed as soil and water retaining structures. Within the framework of the BBRI Soil Mix project (2009-2013), seventeen large-scale bending tests have been performed on excavated soil mix elements previously executed in real construction sites. The purpose of this study was to question the contribution of the soil mix material to the bending resistance of the soil mix walls, up to now designed only on the basis of the steel (H- or I-) beam resistance. Various soil conditions and execution processes were considered in the course of this study. The present paper discusses the test results in terms of deflection, bending moment, steel-soil mix adherence and stresses in the steel reinforcement. The “real-scale” bending stiffness of the reinforced soil mix walls is then computed by back analysis. The measurement of the stresses in the steel (HEA or IPE) beams shows an efficient interaction between the soil mix material and the steel reinforcement: the yield strength was reached in the steel beam at bending moments 20 to 70% higher than without any contribution of the soil mix.

Improving the soft clay surrounding an existing pile group is an innovative, and cost efficient solution to restrict lateral displacements. However, this technique is not widely used in seismic regions due to lack of fundamental understanding of the behavior of improved and unimproved soils. Through a series of centrifuge tests, the seismic response of closely spaced groups of piles in unimproved and CDSM (cement deep soil mixing) improved soft clays was investigated. The soil profile consisted of four lightly overconsolidated clay layers overlaying a dense layer of Nevada sand. The piles in the groups were spaced at 3.0 pile diameters and had a 2 × 2 symmetrical configuration in the plan and were fixed to a rigid cap (superstructure) placed above the ground level. The centrifuge test results revealed that improving the ground was useful in decreasing displacement of the superstructure. The peak displacement of the superstructure of the improved pile group (GIL) was 18 cm compared to 25 cm for the superstructure of the pile group in the unimproved soft clay.

Deep Mixing Method (DMM) for the Rio Puerto Nuevo Project in San Juan was chosen by the Corps of Engineers to improve the soils adjacent to a 92” forced sewer main relocation and to improve the soils for the base of a new drainage channel. The soils consisted of sandy fill, soft clays, organics and stiff, plastic clays. Production comprised over 3,000 DMM elements, installed to a maximum depth of 57 ft deep. Each element consisted of two 5.5’ diameter overlapping columns installed simultaneously. The layout of the elements was such to meet the 100% area replacement ratio required by the design. Wet grab sampling and UCS testing of the retrieved specimens were designed as the main QC/QA method. Upon completion of production, approximately 3,000 specimens were cast. The contract also required continuous coring of at least 12 randomly selected DMM elements and the testing of 8 cored specimens per bore for strength assessment. This paper will illustrate means and methods used in field to collect the wet grab and the cored samples, focusing on the significant differences between the two UCS data sets.

Structure from motion (SfM) computer vision is a relatively new technology that allows engineers to reconstruct a three-dimensional (3D) model of a given scene using two-dimensional digital photographs captured from a single, moving camera. SfM computer vision provides an economic and user-friendly alternative to other 3D scene-capture and modeling tools such as light distance and ranging (LiDAR). Although the resolution and accuracy of laser-based modeling methods are generally superior to vision-based modeling methods, the economic advantages associated with the latter may make it a useful and practical alternative for many geotechnical engineering applications. Although other engineering disciplines have investigated the potential usefulness of SfM computer vision for years, its application to geotechnical engineering generally remains unexplored. Researchers are currently investigating the application of this technology to select full-scale geotechnical field experiments and assessing its potential usefulness as a high-resolution instrumentation/monitoring tool. This paper presents preliminary computer vision results and findings from these studies. The field experiments, as well as the hardware and software details used to develop 3D SfM computer models of the experiments are summarized. The developed 3D models are presented, and displacements measured in the models are compared against ground truth to evaluate accuracy. Observed advantages and limitations of SfM computer vision are discussed, and several potentially useful applications of the technology in geotechnical engineering are listed.

The slurry consolidation (K₀), one of the popular techniques producing specimens resembling field conditions, is usually carried out in large containers owing to large strains incurred during the process. The present studies investigate the influence of aspect ratio and wall friction of the container on the uniformity achieved in the consolidation of the soil specimens experimentally. Parametric studies are also carried out numerically so as to gain further insight into the consolidation behavior due to wall friction and aspect ratio (ratio of diameter-to-height) of the container. It is observed that the uniformity of the specimen is adversely affected by the wall friction especially at lower aspect ratios due to significant loss of applied pressure during transmission. However, even with the substantial wall friction the uniformity could be achieved within a certain zone if the aspect ratio is enhanced. The present studies also attempt to identify these zones and further suggest that any instrumentation for a physical modeling or the sample extrusion be carried out within this zone.

Prior studies have shown that the protection of landside slope of earthen levees against wave and surge overtopping during large storm surges is important. Overtopping protection system can resist the fast-flowing, overtopping turbulent flow on the landside slope that can damage the protective grass covering and expose the underlying soil to erosion. In this research, the overtopping erosion and failure mechanism of an innovative levee strengthening technique—High Performance Turf Reinforcement Mat (HPTRM) are conducted based on full-scale flume tests conducted during combined turbulent wave and storm overtopping. The HPTRM is a three-dimensional turf reinforcement mat joined at the intersections of randomly oriented nylon filaments with high tenacity polyester geogrid reinforcement at low strains. As the grass roots grow through the open space of HPTRM, roots become entwined within the turf reinforced mat. The interlocking between roots and HPTRM can enhance the resistance against hydraulic and shear forces created by high water flow hydraulic condition. Flow velocity, shear stress and average overtopping velocity on landward-side slope and levee crest are measured and calculated. An examination of soil loss from strengthened levee in the full-scale flume tests showed that overtopping flow velocity more correlated with soil erosion along the levee crest and landward-side slope than the shear stress did. Erosion mechanisms of levee surface were developed to study erosion starting position and the roles of the key hydraulic parameters (flow velocity/shear stress).

Barriers are built on the side of the road anytime there is a significant drop in elevation at the edge of the pavement. This includes the top of MSE retaining walls. In that case however, there is no possibility to anchor the barrier in the wall facing because of its lack of strength for this purpose. Instead, an L shape barrier is used to contain the truck during impact. The width of the moment slab must be large enough to resist any rotation under the horizontal force generated during impact. Furthermore, the load transferred to the MSE wall reinforcement must be accounted for in the design. An 18 wheeler truck weighing approximately 360 kN (36 tons) was crash tested against an instrumented Mechanically Stabilized Earth (MSE) wall. The test was successful because the truck was redirected on to the pavement, the barrier did not break, the wall panel movement was acceptable, and, while the top layer of reinforcement strips failed in friction, they did for such a short period of time that the displacement was acceptable. The paper describes the wall construction, the instrumentation, the crash test, and some of the results.

The nuclear density gauge (NDG) is currently the state-of-the-practice device used for quality control of compacted subgrade materials used in transportation construction. However, many transportation agencies have growing concerns over these devices because of the increasingly stringent storage and maintenance requirements of a device with a radioactive source, and with the costs associated with personnel training. These concerns have led to the development of non-nuclear devices as potential replacements for the NDG. The Electrical Density Gauge (EDG) is a non-nuclear device that calculates the dry unit weight and moisture content of soil by means of electromagnetic wave propagation theory. The device requires a soil-specific calibration process where soil moisture and density are correlated to electrical parameters. These correlations are referred to as soil models. Unfortunately, the manufacturer recommended procedure tends to be cumbersome and very labor-intensive. This paper presents a new, less labor-intensive calibration procedure. Calibrated soil models were generated using the manufacturer recommended procedures and the new proposed procedures. Models were then tested for accuracy using a large soil test box, which simulated field conditions. In general, it was found that the new procedures outperformed the manufacturer recommended procedures.

This paper describes results of an advanced suction controlled triaxial test device on a loessial soil in an attempt to define the constitutive relationship between suction stress and matric suction (suction stress characteristic curve) for highly collapsible soils. Due to the presence of void spaces with different degrees of collapse potential within the soil matrix, the collapse phenomenon in loess is believed to be a continuous-stepwise reduction in volume rather than a sudden drop during wetting. Due to this unique volume change behavior, the definition of the suction stress characteristic curve for loess may require a soil-specific experimental testing approach capable of making precise and continuous measurements of volume change and water outflow during loading. The testing approach includes a pressure-feedback control loop to provide the required pressure equilibrium in the system in the case of any change in pressure due to pore structure collapse and two independent digitized volume change measurement devices to measure possible changes in soil/water volume during testing. Based on the experimental measurements, depending on the applied unsaturated stress state variables (e.g., net stress and matric suction), and the consequent magnitude of wetting-induced collapse, the soil specimen may show different behavior during shear. For higher matric suctions, soil specimens experience small changes in volume during the suction equilibrium stage and shear strength curves show a dilative and brittle behavior as shearing proceeds. At lower levels of matric suction or higher magnitudes of net stress, a ductile behavior in the shear stress curves is observed and most specimens experience a decrease in volume during shear. Experimental results indicate a unique critical state line for specimens sheared under varying stress state conditions when defining the SSCC using the measured shear strength data in this study.

As part of a major rehabilitation program in 2001, several pavement sections of the Arkansas Interstate system was rubblized and overlayed. Recently, some of these sections west of Little Rock on Interstate-40 (I-40) experienced severe distresses (cracking, potholes, and roughness). However, I-40 east of Little Rock and I-30 west of Little Rock, reconstructed virtually at the same time, have exhibited no noticeable distresses. The objective of this study is to evaluate root causes of the premature failures of these pavements. To this end, the current pavement condition, historical data, and field core samples have been collected for developing a forensic evaluation framework. Pavement performance data extracted from an Automated Road Analyzer (ARAN) has been analyzed to evaluate the severity of the distresses. Toward establishing correlations, if any, candidate parameters influencing the aforementioned distresses will be gathered from structural and mix design sheets, construction and layout activities, in-service traffic and environmental conditions, interviews, and subgrade soil profiles. The collected core samples will be examined for defects and layer thicknesses, and they will be tested for mechanistic performance evaluation. The findings of the study can be used as a good pavement management tool for timely pavement maintenance actions and for constructing longer lasting pavements. This paper outlines the preliminary steps toward completion of this study.

Underground space development in large metropolitan areas has become a way to accommodate rapid population growth while sustaining and enhancing the quality of urban lifestyle. A common challenge to urban underground construction is in developing such a space in a heavily built environment with minimal impact on adjacent structures and limited disruption to economic activity. This challenge is exacerbated when soft-to-medium soil conditions are encountered. Hence, urban deep excavations are usually coupled with extensive instrumentation plans and continuous monitoring to evaluate performance and detect deviations from anticipated behavior. The massive transbay transit center (TTC) excavation in San Francisco is a unique excavation of unprecedented scale in soft soils characteristic to the Bay Area. It is approximately 1500 ft long, 85 ft wide, and 60 ft deep. Novel technologies were employed to support and enhance the construction control process and monitor ground deformations. This paper will highlight the key features of the field instrumentation program used for the TTC project along with a description of the developed and installed sensors. In addition, it will discuss the data storage and monitoring methods, including the display of construction progress and ground and building movements in a virtual reality environment. The evaluation of ground response to excavation activities will be the subject of future publications.

The dual tip penetrometer (DTP), a novel in situ test, was developed at the University of Florida (UF) to help identify cemented sands. Pairs of DTP and standard cone penetration (CPT) tests were performed at multiple Florida Department of Transportation (FDOT) project sites in Florida. These sites included the West Bay Bridge, and the Port Orange Relief Bridge. Cemented sand layers were present at different depths at these sites. Both DTP and CPT results were analyzed to screen cemented sand identifiers (tip resistance q_c, friction ratio R_f, and the ratio between the second and first resistances T2/T1). The ratio T2/T1 was determined to be best identifier for identifying cemented sand. Based on the above test results and analyses, it appears that the DTP could be an efficient tool to identify cemented sand and better predict pile capacity.

The Kentucky Lock Addition project is the construction of a new 34 m wide by 366 m long navigation lock that will be located landward and adjacent to the existing 34 x 183-m lock. The U.S. Army Corps of Engineers, Nashville District, has the primary responsibility for designing and constructing the project and will operate the lock once it is complete. However, the Tennessee Valley Authority (TVA) is an active partner in the new lock since it will be an integral component of TVA’s Kentucky Dam. Prior to construction of the new lock, a cofferdam had to be built to act as a temporary dam to hold back upstream water (Kentucky Lake). Once the cofferdam was constructed, excavation began for the new deep foundation by removal of soil material downstream from the cofferdam and immediately adjacent to the existing land-side lock wall. This leaves the cofferdam and existing lock wall unrestrained on the exposed land side which could result in movements or instability that could cause life-safety issues to construction workers, construction delays and closure of the existing lock. Having both the water loads on only one side of both the cofferdam and existing Lock wall required installation of an autonomous sensor array to continuously monitor horizontal soil displacement (in-place-inclinometers), water levels (piezometers) and Lock wall movement (tilt meters and joint meters). Data was automatically collected from IPIs, Piezometers (cofferdam), tilt meters and joint gages (Lock Wall) from remotely positioned Data Loggers powered by solar panels. Each sensor has limit values assigned that when exceeded, trip email messages to staff that allow for remote access and review of data for decisions related to changes in construction sequencing or implementation of contingency plans. The system is integrated into Geocomp’s iSiteCentral GIS database software for ease of data collection, review and reporting. Each data logger location and sensor is superimposed onto an aerial plan view of the project site. The sensor icons are active and provide pull-up plots of active, near real-time data. This system has been in continuous operation since 2008, providing continuous 24/7 monitoring and reducing risk for both the Contractor and Owner.

Settlement cell systems are widely used for measuring vertical ground movement of infrastructures during construction and operations. Settlement cell systems can be installed below ground and thereby, do not interfere with construction. This paper presents the installation, field calibration, and data interpretation of a settlement cell system, where multiple settlement cells were connected to one hydraulic line filled with a fluid to reduce the installation cost. A control settlement cell was also installed outside the loading area for the purpose of field calibration. This paper discusses sources of errors in readings and presents a procedure to correct the readings for the effect of barometric pressure, temperature, and systematic error in the settlement cell system. The accuracy of the settlement cell system was improved after implementing the field calibration approach.

This paper presents the preliminary results of an experimental study focused on investigating the fundamental mechanisms of particle–fluid interactions during soil erosion. Historically, researchers have focused primarily on how various soil properties (grain-size distribution, composition, plasticity) affect water-induced erosion. However, recent investigations suggested it is also important to consider permeating fluids other than pure water and how certain physicochemical properties of these fluids (pH, ionic strength, viscosity, composition and concentration of suspended solids) influence soil erosion behavior. The precise mechanisms of particle–fluid interactions and the role of these mechanisms in governing particle mobilization are not currently understood. In this study, pore-scale particle mobilization imaging experiments were utilized in an attempt to preliminarily characterize the mobilization process in terms of the hydraulic shear stress acting on individual particles. Tests were performed on ASTM 20-30 silica sand specimens formed within a custom-fabricated, acrylic, horizontally oriented flow cell that allowed for visual observation of the specimen. The particle mobilization process was captured using a high-definition CMOS camera and imaging system capable of acquiring clear images of individual particles at several hundred frames per second. To specifically focus on the capabilities of the test setup and avoid the inevitable complications associated with testing multiple permeating fluids, only distilled water was used as a permeating fluid. Preliminary results confirm the system’s potential to characterize particle behaviors during mobilization.

The long-term performance of a flexible pavement largely depends on the compaction level achieved in different layers during construction. Traditionally, the compaction level of the subgrade is monitored through spot checking of moisture content and dry density at some discrete points. However, this type of quality control work does not cover the entire pavement and may leave under-compacted areas. These under-compacted areas could likely lead to early failure of the pavement structure. Therefore, it is necessary to develop a real-time compaction monitoring tool that can provide an accurate measurement of the compaction level of the entire pavement. Such measurements could be used to identify and remediate under-compacted areas and provide adequate support to asphalt layers constructed on top of the prepared subgrade. The application of the Intelligent Compaction Analyzer (ICA) for real-time monitoring of compaction of a stabilized subgrade is addressed in this paper. Four case studies demonstrating the successful application of the ICA are included. The compaction level of the stabilized subgrade was monitored in terms of ICA density and modulus. In each case study, it was found that ICA could estimate the compaction level with a reasonable accuracy. It was also found that the ICA modulus and nuclear density gauge (NDG) measured density exhibits a good correlation with R² equal to 0.73.

The Cone Penetration Test (CPT) is widely used for classifying soils and assigning soil properties to the subsurface because it is robust and can be used to quickly collect continuous data with depth. During and subsequent to the construction of a very deep soil-bentonite (SB) slurry trench cut-off wall in Mayfield NSW, Australia, the CPT was used to check the continuity and quality of the SB backfill material. The numerous CPT profiles conducted in the Mayfield wall provided a unique research opportunity for examining how shear strength and effective stress vary with depth. A method is proposed to estimate the undrained shear strength of the Mayfield Wall from the CPT combined with some vane shear data. The results support previous studies that show that the shear strength and the effective stress distributions in SB slurry trench cutoff walls are less than would be expected from a geostatic stress distribution. While there is some increase in shear strength with depth, these data show that the increase is modest and consistent with the less than geostatic stresses. In addition, the authors recommend a general procedure for shear strength and horizontal stress estimation using CPT data in any SB slurry trench application.

Dynamic Load Testing (or High Strain Dynamic Testing as the test is called in the ASTM Standard D4945) is widely considered as a reliable method to determine the capacity of deep foundation elements. To illustrate the reliability of this test method, comparisons between the outcome of a Dynamic Load Test and a Static Load Test on the same pile are often used in the literature, which seem to confirm that the outcome of a Dynamic Load Test can accurately predict the capacity. However, these illustrations generally ignore the subjective aspect of the test result interpretation because, when this aspect is included, a completely different view on the method’s reliability emerges. This paper will use the results of the various international prediction events to illustrate this aspect, which will clearly demonstrate that the reliability of this test method should be reassessed where it has not been adequately validated by adequate site characterization and static load testing. The paper will finally address the impact of this reassessment on the resistance factors that have been derived solely from Dynamic Load Test results.

Microelectromechanical systems (MEMS) sensors have become a common part of everyday life and can be found in a number of consumer electronics. Specifically, MEMS accelerometers have become widespread because of their low cost, due to mass production techniques, and ability to sense constant acceleration. This ability allows devices, such as cellular phones, to measure their rotation relative to Earth's gravity. These properties also make MEMS accelerometers an option for measuring the rotation of geo-structures, such as foundations, in the field or in scale model geotechnical centrifuge tests. MEMS accelerometers appear to be especially beneficial for measuring orientation in centrifuge experiments because they are not limited by the design constraints of traditional tilt sensors: a single constant acceleration vector (Earth’s gravity). This paper presents the theory behind using single-axis MEMS accelerometers to measure the orientation of an object on a plane of reactive centrifugal acceleration and Earth's gravity within a geotechnical centrifuge. The paper specifically addresses cross-axis sensitivity which can significantly impact measurements and is typically excluded from simpler theories.

Four geosynthetic reinforced soil (GRS) piers were constructed in 2012 to support two decommissioned 25.9 m concrete I-girders at the FHWA’s Turner-Fairbank Highway Research Center in McLean, Virginia. Two of the GRS piers are built with an AASHTO No. 8 open-graded aggregate while two are built with an AASHTO A-1-a well-graded aggregate. Survey targets, strain gages, and pressure cells were installed on and in the piers to evaluate long term performance. Through these monitoring efforts, it was discovered that the piers with the well-graded aggregate behaved differently and experienced increased settlement after the first winter cycle. To investigate this further, one of these piers was wrapped with a warming blanket set to turn on when the ambient temperature drops to 1°C to ensure the system remained above freezing. In addition, slide wire potentiometers were installed to monitor the thermal movement of both the I-girders and the face of the walls. The relative movement between the face and the beam provides insight into the super-substructure interaction for GRS. As with the increased settlement for well-graded aggregates during thermal cycles, there is also thermal movement impacting performance. The use of well-graded backfill with any appreciable fine content, regardless of plasticity, may result in thaw weakening and increased movements. Observations also indicate that the I-girders and GRS piers move together. This paper will describe the testing, present results, and provide recommendations on the use of well-graded backfills for GRS piers.

Quality of cast-in-place foundation applications, including Augered-Cast-in-Place (ACIP) piles and Drilled Shafts (particularly those cast under slurry) is greatly dependent upon the practices of the site personnel. Due to the installation techniques used to install these elements, it is usually not possible to inspect the hole through any Non-Destructive Test (NDT) method prior to grout or concrete placement, but there are several NDT methods available to indirectly assess the integrity of these completed elements. This paper will compare several NDT methods with the method of Thermal Integrity Profiling (TIP) for confirming integrity in ACIP piles and drilled shafts. The TIP method evaluates the integrity over 100% of the element cross section by measuring the hydration temperature during the early curing of the grout/concrete along the length of the element. The temperature measurements are typically concluded within 4 to 48 h after placement, thus accelerating construction. For the generally small diameter ACIP piles, meaningful measurements often can be at as little as 4 to 8 h after casting. The use of TIP in ACIP piles and Drilled Shafts can effectively overcome several limitations inherent in other NDT methods. Thermal Integrity Profiling will be described and several examples will be presented where TIP testing was used to confirm the structural integrity of ACIP piles and Drilled Shafts.

In this paper, rapid penetration into soils is studied using reduced scale tests. Refractive index-matched fused quartz, with geotechnical properties closely mimicking those of natural angular sands, is used as the target media. Penetration tests are performed by accelerating a conical rod into the soil target. Meso-scale kinematic interactions are probed during penetration by means of high speed imaging. An embedded plane of dyed fused quartz within the sample allows observations of soil deformation during the penetration. The images are analyzed using digital image correlation. The analyses suggest that soil velocity in the soil-projectile interaction zone decays rapidly with distance from the projectile, diminishing to zero within 4 diameters of the penetrator.

Metal aggregate industry in India produces enormous quantity of stone dust as a waste product. Although a considerable percentage of this waste is used in various works like road construction, concrete, soil stabilization, large quantity still remains unutilized and creates environmental problem. In the present study, an attempt has been made to utilize this waste as alternate backfill material in reinforced soil walls. Experiments were performed on laboratory model of reinforced stone dust walls subjected to uniformly distributed loading. Manually prepared bamboo grid strips were used as reinforcement. The parameters considered for the study were, length of reinforcement as L/H ratio of 0.2, 0.3, 0.4, 0.5, and 0.6; vertical spacing between reinforcement layers and their effect on facia deformation and surcharge at failure. For all cases of reinforcement, stone dust behaves as a very strong backfill material and bamboo grid as reinforcement helps in reducing the facia deformations and increasing the failure load as compared to the load-deformation values with unreinforced stone dust walls.

Biochar is a solid byproduct generated during anaerobic biomass pyrolysis or gasification that has recently gained interest for both agricultural and environmental uses owing to its unique physical and chemical properties. These properties include high surface area and porosity, and ability to adsorb a variety of compounds, including nutrients, organic contaminants, and some gases. Physical and chemical properties of biochar are dictated by the feedstock and production conditions (i.e., pyrolysis temperature and conversion technology), which vary widely across commercial biochar producers. In this study, several commercially available biochars are characterized for key physical and chemical properties relevant to the common uses of biochars in environmental applications, specifically as an amendment to soil landfill covers for enhanced methane oxidation. SEM images of each biochar type were analyzed using Pore Crack Analysis Software (PCAS) in order to quantify differences in surface porosity and structure. Trends in these properties are related to feedstock and production method to aid in the proper selection of biochar for geoenvironmental applications. A high variability in chemical composition, surface properties, and pore structure among commercially available biochars was observed, highlighting the importance of pre-screening biochars prior to use in applications such as a landfill cover or soil amendment.

Landfill cover systems can be tailored to achieve effective methane adsorption as well as oxidation by adding organic materials such as biochars. In this study, a comprehensive investigation is performed to determine the influence of different physico-chemical properties of biochars on their respective methane adsorption characteristics so as to aid the selection of suitable biochar types for field application. Seven different types of wood-based biochars were characterized for their methane adsorption as well as physico-chemical properties. The experimental maximum adsorption capacity values for the biochars ranged between 0.04 and 0.18 mol/Kg. Overall, the methane adsorption capacity of biochars specific to this study increased with increasing porosity and surface area and decreased with increasing particle size, carbon content (total and fixed) and moisture content. Selected biochars are found to have ability to increase the adsorptive capacity of methane when used as a cover soil amendment.

Soil contamination with hazardous substances can be in solid or liquid forms such as petrochemicals or chlorinated solvents hydrocarbons. Contaminants in soil can be physically or chemically adsorbed to soil grains or only trapped in pore space. Soil contamination usually occurs through spillage or burial directly at the contaminated area or migration from a spillage or burial source occurred elsewhere. Some of most occurring sources of soil pollution are petrochemical and chemical contamination. This study investigates the use of electromagnetic (EM) waves with various radiation patterns to induce a controlled transportation of a nonhazardous dye (used as contamination simulant). The medium in this study is aqueous (i.e., water), which helps to monitor the contaminant simulant transport under EM stimulated conditions. EM waves can be launched into the medium at proper frequencies to minimize the heat generation and temperature increase, yet induce a transport according to the EM radiation pattern. Then, the contaminant-simulant transport under EM-stimulated and unstimulated conditions were studied, and the results suggest that dielectrophoresis can be the underlying mechanism of observed EM-induced flow of the contaminant Simulant in the aqueous medium. This is consistent with numerical results as well.