GeoFlorida 2010: Advances in Analysis, Modeling & Design

Rapid increases in processing power, convenient graphical user interfaces, and the commercial availability of sophisticated two and three-dimensional numerical codes have made detailed simulation of engineered geoenvironmental systems practical for many projects. Predictions made with these codes exhibit many of the nuances and perturbations evident in real systems that are stressed by temporally and spatially variable factors (e.g., rainfall or loads). However, these predictions can be very sensitive to the material properties input by the user, the boundary conditions that are applied, and the characteristics of the constitutive relationships that are selected. Examples are used to illustrate the sensitivity of model predictions to each of these factors when they are varied within a reasonable range. The power of inversion for parameterization and assessment of the conceptual model is also discussed. Comparison with field data is shown to be a key step in checking the reasonableness of predictive models.

The ground is a complex engineering material and how to characterize it realistically is a very difficult problem. It is well known that the engineering properties of the ground can vary quite dramatically from point to point throughout a site, and even more so from site to site, and that these properties are highly uncertain. It is also well known that the ground, when subjected to an imposed or self-load, will fail along its weakest path, however tortuous that might be. Given the complexity of the ground, it makes sense to characterize the ground using models which allow for its quite uncertain spatial variability. It also makes sense to use response prediction models which take both spatial variability in ground properties and the tendency of failure to follow weakest paths through the ground into account. The Random Finite Element Method (RFEM) combines spatially varying random field ground models with the finite element method to yield a reliability-based geotechnical methodology which accounts for both spatial variability and weakest path failure mechanisms. Besides being able to realistically model spatial variability in ground properties along with being able to follow the weakest path through the soil, mass, RFEM also provides the significant advantage of being able to account for site understanding in the design process. This paper describes the Random Finite Element Method along with a few of its significant results over a variety of common geotechnical problems. The latter include ground-water modeling, shallow foundation settlement and bearing capacity, deep foundation capacity, and slope stability. LRFD code development will be discussed along the way.

The simulation of free falling objects penetrating seabed soil deposits is one of the most sophisticated and challenging problems encountered in numerical modelling when using the Finite Element Method. This paper describes a robust numerical method for dealing with such complex and difficult problems. The approach is based on the Arbitrary Lagrangian-Eulerian (ALE) method of analysis, whose main features and challenges are described briefly in the paper. Application of this method to the simulation of dynamic penetration of instruments into undrained layers of uniform soil is discussed in some detail and comparisons with experimental observations are made.

Numerical analysis, in the form of the finite element, finite difference or boundary element method, has become a preferred calculation tool in the design of complex geotechnical structures. Even new codes of practice, such as the European EUROCODE 7, encourage the use of numerical analysis in design. However, as there is no general guidance and agreement in the international community on appropriate numerical solvers, constitutive models and boundary conditions, there are often examples of bad practice in the numerical analysis of geotechnical structures. Through examples of the analyses of real problems, this paper investigates the use of appropriate constitutive models and boundary conditions, to highlight both the successful use and the potential pitfalls of modern numerical analysis.

Unconfined compressive tests and suction measurements were carried out on sandy specimens with distinct Class F fly ash amounts (6.25%, 12.5% and 25%), lime contents (3% to 9%), porosities and 28 days as the curing period to assess key parameters controlling strength of fly ash-lime amended soil. A special effort has been allocated in order to develop a dosage methodology for fly ash-lime improved soils based in a rational criterion, as it exists in concrete technology where the water/cement ratio plays a fundamental role in the assessment of the target strength. The results show that the unconfined compressive strength (q_u) increased linearly with the amount of lime for soil-fly ash-lime mixtures at all curing time periods studied. A power function fits better the relation q_u — porosity for soil-fly ash-lime mixtures. The bigger the amount of fly ash and the curing time, the larger the q_u for any given porosity and lime content. Finally, the porosity/volumetric lime content ratio shows to be a good parameter in the evaluation of the unconfined compressive strength of the soil studied.

This paper presents a modeling study to evaluate the impacts of leaching on groundwater from fly ash stabilized layers in roadways. The computer program, WiscLEACH, based on two analytical solutions for the advection-dispersion-reaction process in the subsurface was used. The analytical method was compared to predictions made with IWEM roadway module, which was developed for assessing the potential for groundwater impacts caused by leaching from industrial material resources used as pavement materials in roadway construction. Predictions made with WiscLEACH and IWEM were compared to field data from a highway test section where the subgrade was stabilized with coal fly ash. Comparison with the field data showed that 90th percentile exposure level predicted by IWEM and concentrations predicted by WiscLEACH at a monitoring well were higher than measured data, which suggests that the predictions are conservative. Factors related to lower predicted concentrations of IWEM than WiscLEACH were discussed.

Accurate estimation of mass transport parameters of chemical contaminants through a soil system is a prerequisite for realistic inverse modeling. In this situation, a mathematical model of the transport process is solved numerically to optimize the design parameters. As the stability and convergence requirements of the numerical procedures limit the usage of large numerical time steps, these time-integral numerical methods either become computationally expensive or yield inaccurate solutions. A detailed convergence and error analyses of different numerical methods is performed in this paper. Further, an automated time stepping implicit algorithm is proposed by smartly adjusting the numerical time step for implicit time-integral numerical procedure using the numerical time step of the explicit schemes obtained by stability and convergence criteria. Thus, the procedure to estimate the numerical solution is rapid due to the implicit nature of the solution yet accurate as it satisfies stability and convergence requirements.

While simple closed form limit analysis solutions continue to be widely used in geotechnical engineering practice, many practitioners are unaware that recently developed computational limit analysis methods now allow direct analysis of the collapse (or `ultimate limit') state for problems of arbitrary geometry, obviating the need to resort to considerably more complex alternative techniques, such as nonlinear finite elements. This paper provides an overview of the state-of-the-art in the field of computational limit analysis, focusing in particular on the groundbreaking `Discontinuity Layout Optimization' (DLO) numerical procedure. In this paper the DLO procedure is applied to a wide range of geotechnical problems, including those involving soil reinforcement and seismic loading, and it is shown that this technique may easily be integrated with LFRD limit state design methods.

This paper presents an overview of experimental and computational research that has been conducted with regard to consolidation-induced transport of contaminants for high water content geo-materials. Recent research has indicated that this transport mechanism has the potential to significantly alter the behavior of a given system. Practical applications in geoenvironmental engineering include impoundment of wastes in confined disposal facilities, mechanical dewatering, in situ remediation of contaminated source zones and in situ capping of contaminated sediments. However, current understanding of the significance of this process is limited with respect to typical materials and chemical concentrations, colloid-facilitated transport, constant rate-of-strain and centrifuge loading conditions and the expected impacts for realistic design scenarios in geoenvironmental engineering.

A constitutive model for describing coupled damage and plastic behavior of Drucker-Prager geomaterials is developed in this study. Considering both plastic strain and damage variable as the role of internal variables, the formulation of constitutive equation is based on thermodynamic theory and Ziegler's orthogonality condition. The entire constitutive response is derived from two thermodynamic potential functions. The flow rules of both plasticity and damage are constructed by using a single yield function of generalized stress space. It was found that the coupled model is non-associated because of frictional and dilative properties of D-P materials. The relationship between plastic and damage variables is deduced and it is determined by parameters of potential functions. The model naturally satisfies the fundamental laws of thermodynamics and overcomes the limitation of phenomenological methods. The formulation of the model presented here can be used as a basic theory for geomaterials mechanical response analysis of coupled damage and plasticity.

In this paper, the free strain radial consolidation theory incorporating the changes of compressibility and permeability of the soil with the change in effective stress via time dependent surcharge preloading is presented. In contrast to the conventional analysis, the current study highlights the nonlinear characteristics of the soil during the consolidation process. A comparison of the nonlinear radial consolidation model, with the conventional theory and the equal strain theory i.e. constant volume compressibility, m_v and constant coefficient of horizontal permeability, k_h is presented. Finally, a case history at Muar coastal plain, Malaysia is analysed on the basis of the current solution. This case history indicates improved accuracy of the predictions in relation to the field measurements and observations.

This paper introduces development of a multiphysical model to simulate the coupled hydro-thermo-mechanical field for unsaturated porous materials. The coupling integrates the Fourier's laws for heat transfer, Richard's equation for fluid transfer, and a linear constitutive relationship. Numerical simulations were implemented by a FEM platform to solve the coupled nonlinear partial differential equations. A simulation case was carried out on a relatively simple geometry, using an accepted model for thermal, hydraulic and mechanical properties. Results of multiphysical simulations, (such as the freezing induced moisture redistribution, the thermal stresses, etc) are consistent with the basic laws and experience. A unique feature of this model is the coupling of the stress field in addition to the thermo-hydraulic process. The model is under further refinement to study freezing-induced stresses in porous materials.

The scope of the paper is to presente two general melhods to calculate Fs=γμ the factor of safety in relation to the Limit Equilibrium (EQU) of soil (and/or rock) masses. According to the Eurocode for Geotechnical Design (EC7), γμ is a reducing factor for the strength characteristics of the soils (cohesion c and tanφ, – φ=friction angle). The first is a generalized method of slices and the second is the "Rigid Blocks Method". Computer programs have been put forward to to calculate Fs= γμ not only for the stability of slopes, but also for problems such as shallow tunnels. Comparisons of results with those in published examples have been done. In conclusion it can be said that to get a safe answer for Fs= γμ in Engineering Practice, two or more mehords must be used and results must be compared.

The paper describes the influence of pile reinforcement on the stability of slopes through numerical analysis. Included in the paper is some discussion of the modifications made to include pile reinforcement in an existing finite element slope stability program that uses the strength reduction method. Then the finite element program developed is compared for accuracy in the solution of the piled slope problem with a popular proprietary code that uses the finite difference method. Finally, parametric studies are presented to assess the influence of pile location and length on the slope stability.

Encasing a stone column with a high-strength geosynthetic provides the column material with significant lateral confinement, which prevents lateral displacement of the column into potentially soft surrounding soil and consequently increases the bearing capacity of the column. Although this technique has been successfully applied in practice, the load transfer mechanism of encased stone columns and their performance in comparison with conventional stone columns have not been studied in detail. This paper describes three-dimensional finite element analyses that were carried out to simulate the behavior of a single stone column with and without encasement in a very soft clay soil using the computer program ABAQUS. A comprehensive study was performed to better understand the mechanism of load transfer in conventional stone columns and geosynthetic encased stone columns. The performance of partially encased columns was then compared to that of fully encased columns and conventional stone columns.

This paper proposes a new technique, which uses the high energy absorption net to upgrade the performance of existing rockfall protection fence. The high energy absorption net is set behind of the existing rockfall protection fence in this technique. In order to confirm the applicability of the proposed technique, field tests and numerical analyses are carried out. This paper describes the detail of the proposed technique and the results of the field tests and the numerical analyses as well as the effectiveness of the high energy absorption net to upgrade the performance of the existing rockfall protection fence.

It is common practice to rely on traditional relationships to compute the bearing capacity of deep foundations. In particular, when dealing with piles is essential to calibrate the load-displacement response, both for axial and lateral loading and to define the load transfer mechanism at the pile tip and along the shaft. These calibrations allow to reduce uncertainties and to design less expensive and safer foundations. The objective of this paper is to simulate the mechanical response obtained from a load test performed in a real scale cast in place concrete pile embedded in alluvial sand, using a 3D finite differences model. The pile was instrumented to monitor directly the reaction along its shaft and tip. The interface was modeled using a shear coupling-spring with frictional resistance. Both the soil and the pile were represented with four nodes axi-symmetric elements. The stress-strain behavior of the soil and soil-pile interface was described with a bilinear Mohr- Coulomb constitutive law. Although the simplicity of the bilinear model, good agreement was observed between the measured and computed responses when monotonic increasing loading was applied (i.e. static conditions). However, the bilinear constitutive model largely underestimates the measured permanent deformations prevailing in the pile-soil system after unloading. This should be accounted for when analyzing the dynamic response of the soil-pile system.

By means of a cyclic loading in a uniaxial compression with the MTS 816 Rock Test System, the fatigue strength and fragmentation of sandstone was measured for a various loading frequencies and amplitude. It was found that fragmentation of the rock increased at low loading frequency than that at high loading frequency. Micro-observations for fractured rock specimens indicated that, in thin section prepared of a specimen subjected to a cyclic loading, there were clear crack branching or bifurcation, and the lower the loading frequency were, the more branching cracks were developed. Finally, some applications of this investigation in engineering practice were discussed.

Studies on the effectiveness of deep ditches against rockfalls have shown that, the original Ritchie (1963) guidelines are not as conservative as previously thought. Moreover, following these guidelines, a unique ditch "depth - width" pair of values is obtained for a given rock cutting not allowing for the chosen of the most economical solution. The above findings gave rise to the research presented herein, where, a number of design charts based on a computer simulation program (RocFall^TM) are proposed for deep rockfall ditches. Rockfall concrete walls and fences became also subject of research as there are no relevant design charts currently available. The assumptions made for the derivation of the proposed charts are: a) the number of falling rocks is one hundred, b) the rocks are detached from the slope crest, c) the initial speed of falling rocks is zero, d) the material of slope is a clean hard bedrock and e) the base of the catchment area is covered by a layer of gravel to absorb the energy of falling rocks. For the case of deep rockfall ditches it was additionally assumed that, the ditch foreslope adjacent to the roadway is vegetated. Furthermore, as a cut slope can be of any rock type and thus, charts of this category provide indicative dimensions, the RocFall^TM default material settings (e.g. coefficient of restitution) were adopted. Finally, it is noted that, for the simple geometries studied using RocFall^TM (slopes without outcrops and benches) the rock impact distance was always zero and therefore, the calculated catchment area width should be corrected adding the maximum impact distance of rocks obtained by Pierson et al. (2001) empirical study.

A typical micropile section above a rock socket consists of a steel core, grout surrounding the core, and pipe casing installed through overburden then a short distance into rock. Within the rock socket, the only structural components are the core and grout. The pipe casing is usually left in the ground. The permissible stresses in the three components are specified by code. For example, the New York City code requires no more then 50% and 35% of ultimate steel stress to be used for the core and casing pipe respectively. 33% of grout compressive strength can be used as allowable. The codes are usually silent of treatment of permissible load in the rock socket as the casing pipe stops a short distance (typically less than 30 cm) below top of rock. Some designers ignore the contribution of the casing pipe while others allow for end bearing of the steel section (typically less than 10 tons) to be added to the socket core and grout load. In this paper an attempt is made to quantify (by analysis) the factors that control the load transferred to the socket after load dissipation through end bearing of the pipe steel section.

Many states allow construction of landfills over previously mined areas. However, mitigation of the underground mines by filling or removal is often required prior to landfill construction. A settlement analysis for the proposed vertical expansion of a residual waste landfill is presented in this paper. The primary purpose of the analysis was to evaluate the possibility of subsidence of an underground mined area underlying the landfill in response to the proposed 31 m high vertical expansion. The analysis was performed using the software FLAC (Fast Lagrangian Analysis of Continua) which is a two-dimensional explicit finite difference code. The results of the analysis show that the proposed vertical expansion would not cause mine subsidence but it would cause a small amount of elastic ground settlement. As a result, no negative impacts to the existing engineering components of the landfill liner system are anticipated after completion of the proposed vertical expansion. This settlement analysis provides an alternative to removal or filling of underground mines to obtain regulatory approval as demonstrated by this vertical expansion project.

Step-path slope failures in jointed bedrock are analyzed using the PCSTABL slope stability computer program. The model simulates bedrock as anistropic material with variable discontinuity lengths. Discontinuity lengths are varied by adjusting the number of boxes used in the BLOCK search routine. Bedrock discontinuity information is based on visual examination of rock cores and acoustic televiewer data. Anistropic strength parameters are obtained from direct shear testing of rock samples. Results provide an understanding of how slope factor of safety varies with slope direction and discontinuity length. The analysis methods are applied to a proposed 400-foot deep quarry in Central California. Slope stability evaluation is especially important in this case because a steep slope is desired for improved production, but the pit is located close to a highway and a canal.

There are many factors that influence the side resistance prediction of drilled shafts in poor quality rock. As part of a bridge replacement project in Oregon, we evaluated the performance of various design methodologies for predicting the side resistance in poor quality rock. In particular, we looked at the side resistance predicted in poor quality rock from the rock mass strength developed using Rock Quality Designation (RQD) as well as the Geological Strength Index (GSI) developed by Hoek and Brown. We predicted the capacities of drilled shafts at several bents along the bridge alignment and compared the estimated bedrock socket required to resist the structural loading. This paper summarizes the determination of rock mass quality using the RQD and GSI methods, describes the prediction methods used for determining the side resistance in poor quality rock, presents the comparison of RQD versus GSI predicted design values, and evaluates the performance of the predictive methods and discusses the difference in cost associated with the drilled shaft lengths predicted by each method. Based on the results of this study, using the RQD methods without any specific laboratory strength or deformation test results may under predict the ultimate shaft resistance within poor quality rock, i.e., RQD < 60 percent.

This paper presents the design and construction of permanent rock anchors for the stability of rock slope in Makkah, Kingdom of Saudi Arabia. The project site was located over the steep hillside along the Jabal Kaaba Road. The height of the slope was 58 m. The geology of the area surrounding the site was mainly composed of granodiorite rocks. Structurally the rock formation was affected with various discontinuities and local faulting. Both field and laboratory studies were carried out. The field study involved detailed discontinuity surveys. Based on the information collected in the field and laboratory, the slope stability of granodiorite was investigated. The kinematical, limit equilibrium and numerical analysis were carried out to determine slope stability. The extensive rock anchor programme undertaken as part of the rock slope stability required the formation of double corrosion protected permanent anchors in weathered granodiorite formation.

Borehole stability analysis plays an important role in the design of oil and gas well drilling. A main aspect of borehole stability analysis is the selection of an appropriate rock strength criterion. The two most commonly used rock strength criteria in borehole stability analysis are the Mohr-Coulomb criterion and the Drucker-Prager criterion. However, the Mohr-Coulomb criterion ignores the effect of the intermediate principal stress and is too conservative in estimating the critical overbalance pressure required to maintain borehole stability; while the Drucker-Prager criterion overestimate the effect of the intermediate principal stress and may result in non-sensible stability predictions. In this paper, a simple model based on a three-dimensional (3D) Hoek-Brown strength criterion is developed for stability analysis of vertical boreholes. Examples are presented to show the application of the 3D Hoek-Brown strength criterion for analyzing the stability of vertical boreholes and the results are compared with those using the Mohr-Coulomb and Drucker-Prager criteria. It shows that the 3D Hoek-Brown strength criterion predicts critical overbalance pressure values that are less conservative than those predicted by the Mohr-Coulomb criterion yet are not as unconservative as those predicted by the Drucker-Prager criterion.

Lattice Boltzmann (LB) method is a computational fluid dynamics method efficient in simulating fluid flow through complex geometries such as those of porous materials. A three dimensional LB model is developed for simulating fluid flow through loosely packed glass beads in this paper. Assemblage of the glass beads is modeled using PFC3D and the assemblage is converted into a binary image file to be used as an input for LB simulation. The numerically predicted relationship between the hydraulic gradient and discharge velocity is compared with constant head test results and excellent agreement is observed.

In order to understand the behavior change of intact Red clay during the drying process, the engineering properties of the direct shear strength, the unconfined compressive strength and swelling ratio of Red clay from Guigang, China, were investigated. It was discovered that the strengths and swelling parameters of the Red clay varying with the decreasing of moisture content are different at the relative high and low ranges of moisture contents, increasing initially then decreasing during the drying process. The critical points of moisture contents are close to the optimum moisture content of the modified proctor test. The reason is that the inherent engineering properties of the Red clay is determined by the coupled action of moisture content and fissures, the main controlling factors are different at the relative high and low ranges of moisture content, the former being the moisture content and the latter being the fissures.

Geotextiles are widely used in various applications including earthen structures, which are often built in unsaturated soil conditions. The design of these earthen structures is often dominated by the shear strength of the interface between soil and reinforcement (i.e. geotextile) layers. However, the unsaturated soil-geotextile interface interactions are not completely understood. This paper examines the shearing behavior of unsaturated soil-geotextile interfaces. Direct shear test results are used to define failure envelopes for unsaturated soil and soil-goetextile interfaces. Experimental results reveal a nonlinear relationship between the soil-geotextile interface strength and matric suction. The paper demonstrates that this non-linear failure envelope can be modeled using the Soil Water Characteristic Curve (SWCC) and saturated effective stress-strength parameters. The paper also compares the shearing behavior of unsaturated soil and unsaturated soil-geotextile interfaces.

The existing Louisiana Highway 1 (LA-1) runs along the bank of Bayou LaFourche in the coastal region of Louisiana and is a primary two-lane transportation route for foreign oil offloaded from ships in the Gulf of Mexico. The Louisiana Department of Transportation and Development (LADOTD) decided to upgrade the southern 28 km portion to a four-lane, fully access controlled, elevated bridge. Earthen embankments link the North and South Connectors to the existing roadway. These embankments would have fill heights of 0.6 m to slightly over 2 meters. Even with relatively low embankment heights, consolidation settlements of 46 cm to 150 cm were predicted. In order to meet the residual settlement requirement, a combination of wick drains, lightweight aggregate fill, and surcharges was used to reduce and accelerate the settlement. Vibrating wire settlement monitoring cells were used to measure the progress of settlement. Observations made from the settlement measurements indicate a strong tidal influence on the settlement behavior of the embankments. This paper presents the observed tidal impact to the settlement and the resulting difficulties associated with evaluation of the settlement data. Both Asaoka and hyperbolic curve matching methods were used to predict the final settlement values. The two methods produced comparable estimated final settlement values.

The soil-water characteristic curve of an unsaturated soil is usually measured at equilibrium or steady state. The measurement based on the conventional methods is time-consuming. Alternatively, multistep outflow tests can be introduced to determine the soil-water characteristic curve. In this paper, the presence of dynamic capillary effects during multistep outflow experiments is illustrated, its impact on the residual water content is discussed, and a theoretical model is developed to simulate the testing results. Finally, an effective procedure is presented to determine the equilibrium SWCC curve based on the results of a non-equilibrium outflow test. Compared to the conventional methods, the proposed procedure can save significant experimental time in determining the SWCC curve.

Ground fissuring at playa lakes is a common geohazard where differential settlement of aquifer sediments caused by groundwater extraction is considered to be the mechanism for fissure development. Although this mechanism may be a common problem, fissures may also originate from natural causes, including desiccation or tectonic movements. Broadwell Basin near the town of Ludlow, in San Bernardino County, California contains a narrow playa lake approximately four miles long and a mile wide that was considered as a site for possible industrial development. The location is isolated and not subject to groundwater extraction, but the lake bed contains numerous fissures that could be as wide as about 1.8 meters (six feet) across at the surface. The characterization of the Broadwell Basin fissures was conducted on the basis of several approaches. High-resolution S-wave seismic reflection surveying mapped the overall tectonic structure of the basin. The fissures were trenched to as deep as 9 meters (30 feet) to understand their physical characteristics as a function of depth. The timeframe of fissure activity was addressed by means of age dating of carbonized wood from the trench with the C¹⁴ technique. A comprehensive program of laboratory testing of disturbed and undisturbed samples was conducted with emphasis placed on understanding the mineralogy of the soils, the distribution of natural moisture content, and the nature of shrinkage of these soils when they are desiccated. The basic conclusion of these studies is that the fissures are not tectonic. They exhibit neither vertical nor horizontal displacement. The fissures currently visible formed hundreds and probably thousands of years ago. Laboratory testing confirms the slow rate of their formation and indicates that the lake sediments are currently at a moisture content where the formation of additional fissures would not be expected to develop under current climatic conditions.

Experimental investigation was carried out on a strip rigid footing resting on homogeneous and reinforced collapsible soils and subjected to inundation due to groundwater rise. The objective of this investigation is to examine the effect of reinforcements on the footing collapse settlement. Tests were conducted on homogeneous collapsible soil, partially replaced collapsible soil with compacted sand with geotextile reinforcement layer at the interface. Additional tests were performed after inserting geogrid reinforcement layer(s) within the compacted sand layer. An empirical formula is presented to predict the collapse settlement of the strip footing on homogeneous collapsible soil. The contributions of the replaced sand layer with the presence of the reinforcement layers to the collapse settlement were introduced in terms of reduction factors.

A reddish brown lateritic soil treated with up to 12% bagasse ash by dry weight of soil was compacted at –2, 0 and +2% of the optimum moisture content with four compactive efforts (reduced Proctor, standard Proctor, West African Standard or Íntermediate' and modified Proctor) for use as a suitable material in waste containment application. The treated soil was assessed to determine unsaturated hydraulic conductivity using Brooks - Corey and van Genuchten models. Generally, unsaturated hydraulic conductivity of specimens determined using both models decreased with higher matric suction regardless of the bagasse ash content, compactive effort and molding water content. On the other hand, unsaturated hydraulic conductivity increased with bagasse content for the various matric suctions considered but in all cases their values were less than 1 x 10^–9 m/s required for a liner material even at a low suction value of 10 kPa.

Deformation of swelling rocks causing convergence in tunnels has always been an ambiguous issue. These deformations can lead to convergence and reduction of tunnels area. The aim of the current paper is development an analytical model using differential equations for formulating swelling strains as a function of time and stress. By this model, the swelling strains can be computed from the start of excavation to the time of installation of tunnel lining. The stresses of the surrounding tunnel due to excavation are calculated by Finite Element Method. These calculations are computed in MATLAB programming code. Results from this model indicated good compatibility with experimental results.

This paper describes a servo-controlled true triaxial (cubical) device that has been developed to test 3-in (7.5-cm) side, cubical specimens of unsaturated soil under controlled-suction states for a wide range of stress paths not achievable in a conventional cylindrical apparatus. The cell is a mixed-boundary type of device, with the specimen seated on top of a high-air-entry disk and between five flexible (latex) membranes on the remaining sides of the cube. The new cell is an upgraded, more elaborate version of the one previously reported by Hoyos et al. (2005), featuring two independent pore-air pressure and pore-water pressure control systems via a PVC-100-UNSAT pressure panel, as well as a fully computer-driven stress application and control system via a PCP-5000-UNSAT pressure panel. Suction states, s = (u_a - u_w), are induced in the specimens via the axis-translation technique. The technique is implemented by utilizing the s = u_a testing concept (u_w = 0). The paper outlines the full development of the new cell, including details of its main components, the step-by-step assembling process and the selection of the appropriate sample compaction process and density for testing compacted clayey sand. The operational cell will play a fundamental role in the complete characterization of unsaturated soil behavior under multi-axial stress paths that are likely to be experienced in the field.

A series of shear strength tests were performed on six different types of fine grain soils at controlled densities and degrees of saturation. Since these variables were controlled the most important variable affecting the shear strength of the soil is the change in the degree of saturation producing a change in the suction stress. These changes in suction stress modify the state of effective stress, thus affecting soil behavior. These results were used to compare the variation in factors of safety for cantilever, gravity, and tie-back wall designs produced by the change in effective stress due to saturation, for short term condition. In addition, a desired safety factor was chosen and the influence in the final design due to changes in saturation was investigated, and was complemented with cost estimations. The final results have demonstrated a suction stress influence on the wall design, and cost, when short term conditions are considered.

A compacted glacial till sample was instrumented with pairs of water content and soil water potential sensors to capture its hydraulic response to a series of wetting and drying cycles. The measured paired values of soil suction and water content were used to determine the soil water characteristic curve (SWCC) for the sample following each drying cycle. Significant changes in the SWCC occurred mostly after the first drying cycle because the soil structure was extensively altered during the initial drying process. Moreover, substantial changes in the water retention parameters took place within the upper portion of the sample. This is because most fractures that were generated due to desiccation of the clay began at the surface and propagated downwards. The key finding of this paper is that SWCCs of earthen caps change when subjected to wetting and drying cycles and hence modeling parameters need to be treated "dynamically."

The dynamic shear modulus of soils is needed to predict soil behavior in response to cyclic loading. Even though the effective stress has been shown to have a significant impact on the dynamic modulus of water-saturated and dry soils, its effect on the dynamic shear modulus of unsaturated soils has not been evaluated. Specifically, studies on the dynamic response of unsaturated soils have characterized variations in small-strain shear modulus (G_max) as a function of the degree of saturation or matric suction alone. In contrast, this study evaluates the use of the suction stress characteristic curve to characterize the impact of mean effective stress (σ'_m) on the dynamic shear modulus of unsaturated sand. A fixed-free resonant column test device was adapted with a hanging column setup so that the small-strain dynamic shear modulus could be measured for sand specimens under different confining pressures and matric suction values. Trends between the small strain shear modulus and effective stress for unsaturated sand were found to be different from those reported in the literature, where G_max varied linearly with the square root of σ'_m.

The paper focuses on developing design charts that can be used to calculate, without iteration, the spacing of prefabricated vertical drains (PVDs) for a given soil condition and target degree of consolidation within a specified time. To this end, experimentally obtained hydraulic conductivity profiles in the disturbed zone surrounding the PVD are approximated by a sigmoidal function and incorporated in finite element analysis (FEA) for a parametric study. Subsequently, an analytical solution with bilinear variation of hydraulic conductivity in the disturbed zone is identified that produces PVD response comparable to those obtained from FEA. The analytical solution is used to develop design charts for a variety of conditions and hydraulic conductivity profiles that can be easily used in practice. The design charts can also be used for conditions in which overlapping of disturbed zones occurs.

The focus of this paper is on modeling the essential mechanical properties of moisture sensitive weathered coarse-grained materials like rockfill materials using a hypoplastic constitutive model. The model is based on the current void ratio, the effective stress, a moisture dependent solid hardness and the rate of deformation. Creep and stress relaxation during the time-dependent process of degradation of the solid hardness are also taken into account. Herein the solid hardness is related to the grain assembly in the sense of a continuum description and does not mean the hardness of an individual grain. The calibration of the model is performed for weathered broken granite and the performance of the model is demonstrated for triaxial compression tests under dry and water saturated conditions. The prediction of the model is compared with the corresponding experimental results.

Many authors have analyzed bifurcation with hypoplasticity, but they have not studied the influence of the hypoplastic parameters on strain localization analysis. The focus of this work is twofold: 1. To analyze the influence of the hypoplastic parameters, which control the strain-softening behavior, on the onset of bifurcation. 2. To study the influence of the mean pressure and the initial voids ratio on the generation of the bifurcation surface on the deviatoric plane and its relation to the limit state surface. Based on these results, it is possible to anticipate whether a shear band is generated in a given loading path. On the one hand, it was found that the more strain-softening the material develops, the earlier the onset of bifurcation in triaxial compression paths. On the other hand, the bifurcation surface is weakly influenced by the initial voids ratio, although this surface is strongly influenced by the confining pressure. Lastly, this work has found the intersection of the bifurcation surface and the limit state surface, and it shows the loading paths in which a shear band is not expected.

The Visco-hypoplastic constitutive model is developed for fine-grained soils and reproduces the viscous behavior of these materials such as creep, relaxation and rate dependence. The model adjusts to the Butterfield's compression law at isotropic states. Nevertheless, it is not able to simulate the influence of the structure in the materials mechanical behavior and hence, an extension has been proposed herein. This extension introduces a new state variable representing the material structure defined as the ratio of the preconsolidated mean stress at intact and remolded states for the same material. The structure follows a degradation law which accelerates after yielding and decreases until the remolded state is reached. The overconsolidation ratio OCR and the material stiffness increase along with the structure values. The structure influence in the stiffness is reproduced by modifying the Butterfield's compression law at the elastic range. Simulations on a high structured soil show satisfactory results, and a numerical implementation for FEM has been developed.

The Hypoplasticity model can accurately simulate the mechanical behavior of sands under different load paths without distinction between elastic and plastic deformation. Contrary to classical models of soil elastoplasticity, Hypoplasticity is an incremental, non-linear, state-dependent, constitutive model with smooth and continuous response envelopes; stemming from the Rational Mechanics framework, Hypoplasticity does not need a prior plastic potential criterion or pre-defined hardening rules. Recent studies have shown a complex behavior of sands under undrained conditions. Several researchers point out new features in the undrained stress-strain behavior. These include peak strength, peak dilatancy, ultimate steady state, critical steady state, critical void ratio, and transformation phase. All of these studies demonstrate that the features are dependent upon state variables, such as density and confining pressure. This work examines the state-dependent behavior of sands by introducing a bounding Drucker-Praguer surface and a state-dependent peak dilatancy function to the Hypoplasticity model.

The storage of nuclear waste is still an unresolved problem of the nuclear industry, geological disposal being the most favored option. Most conceptual designs for the deep geological disposal of nuclear waste envisage placing the canisters containing the waste in horizontal drifts or vertical boreholes. The empty space surrounding the canisters is filled by an engineered barrier often made up of compacted swelling clay. A good understanding of thermo-hydro-mechanical (THM) issues is therefore necessary to ensure a correct performance of engineered barriers and seals. The conditions of the bentonite in a typical engineered barrier are being simulated in a mock-up heating test at almost full scale. The aim of the paper is to assess the capabilities of CODE_BRIGHT to analyze the evolution of the main Thermo-Hydro-Mechanical (THM) variables of this test; and also to study the unexpected slow hydration of the clay barrier observed at the advanced staged (i.e. after years) of the experiment. The inclusion of thermo-osmotic effects in the analysis has assisted to a better understanding of experiment.

On Oct. 8, 2005, an earthquake triggered a landslide which blocked two tributaries of the Jhelum River, namely the Karli and Tang channels at their confluence, near Hattian Bala, Azad Kashmir, creating two lakes. Construction of spillways for the two lakes reduced the volume of water in Tang Lake. Karli Lake kept filling until April 2007, when its surface elevation reached its spillway level. Inundation upstream of this landslide dam can cause substantial downstream damage in case of failure. To assess this failure potential, different studies have been undertaken and developing scenarios monitored. Attempts have been made to visualize the subsurface conditions using various geotechnical investigation tools. Selected details of the electrical resistivity method of investigation are presented. These include resistivity imaging surveys in space as well as time. Spatial variations in the resistivity values enabled visualization of the subsurface profiles, while the temporal changes in resistivity values helped assessment of the tendency of water seepage into the dam body from Karli Lake. Laboratory resistivity tests were also conducted at different densities and saturation levels on the matrix material from the dam to calibrate the field resistivity values with the degrees of saturation.

Ocean Earth Technologies, Inc. (OET), a subsidiary of N.S. Nettles &Associates, Inc., was contracted to perform a geophysical mapping study andcomprehensive geotechnical investigation of a proposed resort property located inRendezvous Bay, Anguilla, British West Indies (BWI) (Figure 1). The purpose of themapping was to provide extensive detail into the geologic conditions across the siteand in the bay that would help to identify any anomalous subsurface features, such assolution zones or fractures in the limestone unit, which would be potential hazardsand areas of concern for construction purposes. Additionally, the testing was used toidentify the depth to competent rock across the site, the thicknesses of overlyingunconsolidated units, and ideal drilling locations for the placement of flushingchannels that will connect the inland salt pond on the resort property to RendezvousBay. The geophysical surveys consisted of both Multi-Electrode ElectricalResistivity (MER) testing, as well as Multi-Channel Analysis of Surface Waves(MASW), a seismic method of geophysical mapping (Nettles, 2005; Ocean EarthTechnologies, 2006; Ocean Earth Technologies, 2006). These surveys were followedby 45 Standard Penetration Test (SPT) borings and 60 ten foot long, four inch rockcore borings in order to ground-truth the geophysical data and obtain physicalsamples for laboratory analysis of engineering properties for design purposes.Additionally, 71 Cone Penetration Test (CPT) soundings were also performed on thebeach front unconsolidated sands.

Granular material packing is of considerable importance when considering the stability and shear strength of granular media. In this study, granular material packing at the grain scale is studied to see how packing is influenced by inherent particle characteristics such as shape, angularity and surface texture. Studies will show clear evidence of the influence of these factors on the granular packing obtained. Materials tested include glass beads, natural sands and a manufactured sand of varying shape, angularity and surface texture. X-ray CT is employed for imaging and 3-D volumetric reconstruction of sample assemblages. Image and volumetric processing routines are then performed on these reconstructions to measure local variations in packing density and generate density maps. In this paper, we demonstrate the success of our technique by exercising the method on several sets of granular particles.

Digital images are used commonly during site characterization. Placing range features in view permits dimensions to be estimated. Terrestrial photogrammetry developed for rock structure analyses can be used for reasonably precise measurements of boulders and blocks exposed at the ground surface. Simple image analysis provides a means of inexpensive, rapid estimates of parameters needed for block dimensions and size distributions. Images collected with calibrated cameras are needed for terrestrial photogrammetry; the same images or images taken with uncalibrated cameras can be used with public-domain software for simple collection of size information. ShapeMetriX3D (3G Software and Measurement) and ImageJ (National Institutes of Health) software are used to demonstrate the utility of these approaches for colluvial deposits in a California road cut, a boulder-bar on an Oregon stream, and a rocky headcut in a Utah channel. Parallax distortion is corrected with photogrammetry, but not with image analysis. Sources of error in image analysis need to be considered with the variability in earth materials and how well the distribution of rock blocks or boulders is represented by the visible exposure. Dimensions determined with photogrammetry can be used as image-analysis scale references.

A large number of aging bridges require a reliable inspection of their condition to determine if they are safe, or if they need to be rehabilitated or replaced. The direct assessment of foundations for existing structures would require excavation or, at least, an extensive drilling program. Such an effort would be extremely costly and impractical. It could also compromise the integrity and stability of the structure itself. The authors present the inspection technique that combines seismic cross-hole tomography and 3D imaging of seismic reflectors. The measurements are conducted using three drill holes that surround the investigated underground foundation components. The technique produces images of piles or other structural features through triangulation of reflected waves recorded at several points along each of drill holes. The authors also recognize new challenges when imaging a cluster of piles in a soft ground due to a need for seismic waves of the proper wavelength, and due to an intense dispersion of seismic waves in the space between the piles.

Time effects observed in tests on sand with different constant strain rates as well as creep tests and stress relaxation tests initiated at different stress levels exhibit patterns different from those observed in clays. It appears that time effects in sand may be associated with crushing of particles, and single particle crushing has therefore been studied. A mechanistic picture of deformation and time effects in granular materials is presented in which the time effects depend on interparticle friction, grain crushing and grain rearrangement. The phenomenon of static fatigue of individual particles appears to be at the root of time effects in sand. A review of previous studies of static fatigue is presented. Load-controlled tests on individual sand particles in the form of spherical glass beads (quartz) were performed by maintaining constant loads lower than the short term crushing loads. As do rock specimens in triaxial compression, the glass beads show effects of time to crushing.

Grain shape is a key factor affecting the mechanical properties of granular materials. However, grain shape quantification techniques to distinguish one granular material from another have not reached a stage of development for inclusion in modeling the behavior of granular materials. Part of the problem is the equipment of choice for grain shape measurement is the scanning electron microscope. This is a relatively expensive and complex device. In this paper, a practical approach using light microscopy to quantify grain shape and to identify the key shape parameters that can distinguish grains was investigated. A light microscope was found to produce grain images with sufficient quality for the purpose of observing the grain shape profile. Several grain shape parameters were determined for eight different sands — four sands chosen for this study and four sands from an outside source. Six of these - circularity, roundness, sphericity, aspect ratio, compactness and modratio — are shown to be the key shape parameters that differentiate these sand grains. Relationships between the six key grain shape parameters and dilatancy were developed to enable a better understanding of the mechanics of granular materials and for potential use in practice. Data to build the relationships were obtained using a light microscope, digital image processing software (ImageJ), and direct shear tests on four uniform sands composed of grains with shape profiles — ranging from very rounded grains in one granular conglomerate to very angular shaped grains in another.

Granular materials forming part of foundations and embankments experience crushing as a result of compressive loads. Crushing can not be visualized in standard geotechnical tests or in the field, but here the Discrete Element Method (DEM) was used to solve this problem. The DEM simulated compression tests were performed on cylindrical particles in a container subjected to either: (1) an increasing axial compressive load, or (2) an increasing gravity field (centrifuge test). In the uniaxial compressive tests, the axial load varied from 1 x 10⁴ N to 1 x 10⁵ N. In the centrifuge tests, the gravity varied from 1g to 1800g. The axially increasing compression tests indicated that the crushed particles were uniformly distributed throughout the sample. The centrifuge tests indicated that crushing was concentrated at the container's bottom. Both tests produced after crushing a granular assembly that was fractal. The tests' relevance to understanding crushing under footings and in embankments is also presented.

Gravels forming part of flexible pavements experience abrasion as a result of traffic loads. Abrasion takes place when the sharp corners of the particles break and produce a mixture of grains of varying sizes. Also, the original particles change in shape as well. In this study, the abrasion of gravels are evaluated experimentally and analytically. Experimentally, the gravels were subjected to abrasion in a jar milling test. Analytically, abrasion was measured using the fractal dimension concept. Two fractal dimension values were obtained. One was the shape fractal dimension value and the other was the fragmentation fractal dimension value. Two sets of gravels were used in this study. One was made of smooth gravel, the other was made of rough gravel. It was determined that with an increase in the level of abrasion, the shape fractal dimension number decreased in value and the fragmentation fractal dimension number increased in value.

The results presented in this paper are about the experimental and numerical studies of the trap-door problem in three dimensions with rectangular trap-door. Artificial materials (glass beads) were used in the experimental tests. The mechanisms were investigated with CT scanning and with numerical analysis using Discrete Element Method (DEM). DEM modeling was carried out on several particle size distributions. One of the samples presented the same characteristics as for the experimental tests (same particle shapes and size distributions). The friction parameters of the contact laws used in DEM analysis were determined by comparison of real triaxial compression tests with numerical modeling of triaxial tests. As the trap-door was moved downward, the response of the granular layers broke down into 2 main phases according to the amplitude of the trap-door displacement. The agreement between numerical and experimental results was satisfying. The mechanisms were described with regard to the shape of the failure zone and also from the strain field point of view. The effect of the particle size on the amplitude of load transfers and on shape of failure zone was observed.

Micro-mechanisms in the analysis of elastic shear stiffness were investigated by the simple multi-scale approach incorporating with the discrete element simulations. The stress-level dependent elastic stiffness and the cross-anisotropic elasticity were focused to characterize the experimental soil elasticity. To capture the micromechanical response of a granular assembly, the discrete element simulations with 10,000 spherical particles were conducted. The small-strain cyclic shear tests were simulated to obtain the elastic shear stiffness. The regression on the elastic shear moduli yields the power relationship between the elastic stiffness and stress components. The sums of the exponent are consistently around 0.35. The micro to macro scale analysis of the elastic properties was attempted. The apparent similarity between macroscale and microscale constitutive equations determines the macroscale parameter of the exponents. The simple multi-scale approach was confirmed by the numerical simulations which result in the similar value of the exponent to that in the Hertz's contact law.

Experimental evidence shows that the mechanical behavior of sands in triaxial conditions depends on the preparation of samples and the applied stress paths. The fabric of sands, as a function of formation conditions, is responsible for the establishment of load chains as a micromechanical response of grain assembles. Fabric tensors can affect the constitutive equations of sands by portraying different granular material responses when subjected to different stress paths. The spatial distribution of elongated particles, as related to fabric, affects fundamental aspects e.g., dilatancy, peak stress, picnotropy, and barotropy.

Recently developed American Society for Testing and Materials (ASTM) standards for direct simple shear (DSS) testing require that the sample be laterally confined in either a wire-reinforced membrane or stack of thin rings. Although wire-reinforced membranes are more commonly used in practice, it is uncertain how the results of the two confinement methods compare. This paper presents the results of direct simple shear tests performed on high plasticity clay and low plasticity organic silt to compare the effects of using either wire-reinforced membranes or Teflon-coated rings for lateral confinement. Comparisons are made for both the consolidation and shear phases of the test. The consolidation data suggest that the rings may provide increased lateral stiffness relative to the wire membranes. When appropriate system corrections were applied to the measured soil test data, the results of both confinement systems produced comparable results in terms of stress-strain behavior and strength.

The settlement behavior of compacted inorganic soils containing a small amount of organic matter is presented in this paper. The settlement behavior was studied using one-dimensional consolidation tests. Two assumptions were established regarding the decomposition of organic matter: (1) The organic matter can decompose completely and transform into liquid, and (2) The organic matter can decompose completely and transform into gas. Based on these assumptions, weight-volume relationships were developed and consolidation tests were conducted to study the settlement behavior of soil after the decomposition of organic matter into water and air. The results of these tests were utilized for settlement analysis of slab on grade supported on inorganic soils containing a small amount of organic matter. The results of this study indicate that soils containing a small amount of organic matter exhibit one-dimensional consolidation behavior similar to inorganic soils and conventional laboratory testing procedures provide a reasonable approach to study the effect of decomposition of organic matter on the settlement behavior of inorganic soils.

Pamper bacteria, they will help us: this sounds like a fairy tale that mothers tell their children. No way. These small creatures will help us, if we pamper them. This paper contains two very different cases where fairy tales come true. Feed the bacteria in an intelligent way and they will do the same work for us as traditional methods would, but with much less energy, materials and at lower costs.

While diatoms are used in many engineering and scientific applications ranging from filtering and construction to animal feed and natural pest control, very few geotechnical applications utilize diatoms. Natural soils containing diatoms are considered highly compressible, difficult to compact, and unstable when subjected to dynamic loads. Yet, given their unique characteristics (i.e., high water absorption and liquid limit and larger friction angle), there is great potential for utilizing diatoms and natural diatomaceous soils in the development of engineered particulate materials for geotechnical and geoenvironmental applications (e.g., hydraulic barrier layers and landfill covers). Two important considerations for clay barrier systems are (1) ionic concentration-induced aggregation leading to crack formation, and (2) water retention during wet-dry cycles. This study investigates the susceptibility of fine-grained mixtures to pore fluid ionic concentration using bench-scale fabric formation tests (Atterberg limits, sedimentation, viscosity) and the measurement of water retention curves and shrinkage for various diatom-kaolin clay mixtures. Preliminary results show that the presence of diatoms reduces (1) the sensitivity of the particulate mixture to increased ionic concentration and (2) the formation of drying cracks in the tested specimens even when water retention increases.

The static and dynamic behaviors of granular materials depend upon the shape of the grains. The shape includes form, roundness and surface texture. Form refers to the gross morphology. Roundness measures the sharpness of the particle corners. Surface texture refers to micro relief features. In this study a method based on the fractal dimension concept is used to determine separately the form, the roundness and the texture of granular materials. Straight pixel chains of different size are used to measure the length of a particle profile. The resulting number of pixel chains needed to cover the profile and the associated chain sizes are plotted on a log-log graph. The plot shows three distinctive straight line segments representing the fractal dimension of the form, roundness and texture of the particle respectively. The fractal dimension concept was found to be a powerful tool to measure these components of shape in granular materials.

The behaviors of granular materials are controlled by not only the material stiffness but also strain level. Rigid sand and soft rubber particle mixtures are prepared with various volumetric sand volume fractions (sf). Small strain resonant column, intermediate strain oedometer, and large strain direct shear tests are performed to explore the behavior of the mixtures with different volumetric sand fractions. Threshold stain and minimum damping ratio increase with a decrease in the sand fraction. The linear responses of shear strain and damping ratio with the shear strain are observed at the mixture of sf=0.2. A linear shear wave velocity-void ratio trend is observed for each sand fraction. Shear wave velocity-void ratio and stress-axial strain relations are categorized into three groups according to sand fraction: rubber-like, sand-like, and transitional behavior groups. The friction angle increases with an increase in the sand fraction and no apparent peak strength is observed in the mixture except for sf=1.0. This experimental study suggests that the strain level is one of the important factors to determine the behavior of the mixtures.

Soil properties such as void ratio, hydraulic conductivity and volume compressibility, which determine consolidation process, are usually spatially varying in natural soils. Such spatial variability of consolidation-related soil properties promotes the specific patterns of the excessive pore water pressure dissipation during consolidation process with respect to the heterogeneity configuration, which is not the same as the typical ones shown at homogeneous soils. This study highlights specific characteristics of consolidation at heterogeneous soils explored by numerical simulations.

One of the techniques currently used to reinforce road and railway platforms in areas subjected to localized sinkholes is reinforcement by geosynthetic sheet. To improve the existing design methods, based on simple assumptions, a new approach has been developed, taking better into account the real behavior of this reinforcement, in particular the geosynthetic behavior in anchorage areas and the increase in stress at the edges of the cavity. A numerical study based on the coupling between the finite element method (FEM) and the discrete element method (DEM) was performed to validate the new analytical approach and verify the assumptions. Comparison of the results obtained by this new analytical method with measurements of a full-scale experiment and the results of numerical model confirmed the relevance of these new developments.

Subsurface erosion threatens the stability of levees and earth dams. A less understood aspect of subsurface erosion is the erosion potential of peat. In the Sacramento-San Joaquin Delta in California, some levees were built on peat deposits. This paper reports the preliminary laboratory study of subsurface erosion of peat. Two types of peats are tested. Hole erosion tests are conducted using a triaxial apparatus. The triaxial cell is modified to allow the eroded peat particles to exit the cell into a pressurized sedimentation tank. The peat specimens are saturated and consolidated under four different effective stresses. Then hydraulic gradient is incrementally applied to the specimen to find the critical hydraulic gradient. Based on the preliminary research, it is concluded that (1) when peat is consolidated under embankment load, even with small effective stress of 34 kN/m², internal erosion is less likely to occur, (2) due to the high compressibility of peat, consolidation under increased embankment loads tends to close (or heal) initially formed piping channels.

In September 1999 a Regional Distribution Center in North Florida that included a 10 hectare single cell storm water retention basin was nearing completion. Runoff to the basin from a three inch rainfall event resulted in the occurrence of a cluster of multiple and spontaneous sinkholes within the basin. Compaction grouting was used to stabilize the sinkholes. In early 2000, as the basin partially filled from relatively small rain events and more sinkholes were experienced, which were repaired by sand filling. In late June 2000, a heavy storm filled 40% of design storage and resulted in about two dozen spontaneous sinkholes that emptied the basin rapidly. Upon review, evaluation and consultations, future multiple spontaneous sinkhole events were forecasted within other parts of the basin, and a Remedial Response Protocol was provided. In July of 2001, a heavy rain event filling about 60% of design capacity resulted in thirty sinkholes within forecasted areas, which were remediated in accordance with the response protocol. The magnitude and frequency and repeated occurrence of the sinkholes became a media event with considerable public concerns. The concerns were addressed to the satisfaction of the regulatory agencies and reasonable assurances were given that the sinkhole events have matured and did not result in environmental degradation of the ground water. Since then, even though the basin has experienced about 60% filling, no new multiple sinkholes of consequence have taken place. While multiple sinkholes in retention basins are frequently experienced, to our knowledge, no prior explanation has been made as to the reasons for Multiple Spontaneous Sinkholes. This paper provides a brief history of the project, the area hydrogeologic setting, and an explanation of the mechanism of Multiple Spontaneous Sinkholes. Remedial measures are presented to reduce or mitigate sinkhole events and the potential for contamination of groundwater.

This paper presents a case study of the construction and load testing of drilled shafts installed in residual soil that gradually transitions to weathered volcanic rock. The drilled shafts are 1219 mm non-production shafts installed in the vicinity of the foundations of a suspension bridge that carries petrochemical export pipelines over a marginally stable steep volcanic bluff.

In many areas of the United States clay soil is the major building material available for construction of foundations. However, in Florida, clay soils are shunned; they are either removed or covered by substantial thicknesses of granular material. Although only a small percentage of clay occurring in Florida is known to be expansive, this onerous quality has influenced many to label all clay expansive. In many sinkhole investigations when clay is found near the foundation, it is summarily decided that the clay is expansive and is declared the cause of building distress. This paper is intended to remove some of the myths surrounding Florida clay and provides practical methods for indentifying expansive clay. It also includes a review of clay testing methods and provides suggestions for efficient methods of testing for expansive clay. The discussions are directed to the occurrence of clay, particularly in sinkhole investigations, and the likelihood of its occurrence causing building distress.

An innovative approach to fully understand expansive soil identification and quantitative movement prediction lies in understanding the surface phenomena of individual clay particles within the soil matrix. The impact of incorporating such physicochemical fundamental material properties into unsaturated soil mechanics research will have a transformative influence on foundation design of critical infrastructure. The electrical properties of soil have been shown to be a good indicator of moisture, contamination and mineralogy and are being studied in order to gain a better insight into macroscopic soil behavior. This article will discuss the methodology of the low to medium frequency electromagnetic measurement and the limitations and subsequent solutions found to ensure accurate values of dielectric permittivity (dispersion) to be used in the prediction of expansive soil behavior.

Laboratory tests on unsaturated fine sand show that the equivalent effective stress (EES) in the sand is function of the water content. The EES is determined through direct tensile tests. Three intervals were identified for which the EES varies in different way. In the saturated-funicular state (high water contents) the EES increases as the water content is reduced. If the sand has a water content in the complete-pendular state (an intermediate interval) the EES tends to be constant. for air-water distribution in the partial-pendular state (low water contents) the sand presents lower EES as the water content is reduced, which is the opposite tendency for the interval of water contents in the saturated-funicular state. The EES is a fraction of the suction stress applied in the specimens. This article provides more evidence that there is an EES in unsaturated soils that may reflect the true effective stress in the soil.

This paper presents the case history of 77 sinkholes recorded during the Suncoast Parkway construction, in west-central Florida. These sinkholes occurred where limestone bedrock was excavated. The excavation revealed numerous preexisting solution pipe features in the limestone that were in-filled with clean fine sand. These features were pre-existing sinkholes and served as conduits to recharge the aquifer. The sinkholes that occurred during construction were re-openings of these pre-existing sinkholes. It is also believed that the bedrock excavation had altered the pathways of groundwater recharge at the overburden soil and bedrock interface. Specifically, the bedrock excavation directed larger volume of surface runoff into some pre-existing sinkholes, which previously did not experience large water recharge in recent geological history. The concentration of runoff destabilized the in-filled fine sand and caused the sinkholes to re-open during construction. Implemented remedial measures included hydraulic backfill, grouting, and installation of geotextile. The goal was to minimize potential sinkhole occurrence on the travel lanes of the new highway. Since the end of construction, maintenance records showed sinkholes had occurred only in retention ponds and swales during rainy seasons. They occurred frequently during the first three years after construction and have not been observed after; indicating that a new equilibrium has been reached and the remedial measures in the roadway area were successful.

This paper discusses the case history of mitigating karst conditions during construction of a bridge foundation in central Florida. The installation of a test pile triggered the initial sinkhole and subsequent operations such as drilling test borings and grout injection triggered additional sinkholes. Sinkhole formation at the site ceased only after a substantial quantity of grout was injected. Discovery of active sinkhole conditions during construction required a proactive approach to minimize construction delays and associated costs. Additional investigations were performed to better understand the extents of the problem in order to develop cost effective solutions. The available information indicated that karst subsurface conditions consisted of a cavity dome above the bedrock, below the anticipated pile tip elevations. After considering various remediation options a grouting program was implemented to fill the voids and densify raveled soils below the anticipated pile tip elevations.

The study assesses the possible effects of stress path on expansive soil simulating the different loading path similar to what is expected in the field. The testing program concentrated on a series of consolidated-drained triaxial compression and extension tests of expansive soil specimens on 50 mm diameter and 100 mm high samples. Testing was carried out at consolidating pressures ranging between 0.10– 0.60 MPa using Geotechnical Digital System computer control triaxial apparatus. The Cam-Clay model parameters for expansive soil was determined based on isotropically consolidated drained shear test and consolidation test results. Computations were performed using the model constant and finite element CAD software SIGMA/W to predict the stress-strain response for different consolidation pressure and stress path tests. Predicted results were compared with measured response to assess the validity of the Cam-Clay model and finite element model parameters. The model prediction was found to yield acceptable results and is quite effective in demonstrating the effects of stress paths, effective stresses and strains of consolidated expansive soils.

A laboratory study was undertaken to evaluate the effectiveness of lime and Class C fly ash (CFA) as soil stabilizing agents for a sulfate containing, A-7-6 type CL Oklahoma soil. Using various percentages and employing as criteria the 28 day unconfined compressive strength test (UCS) and the pH value, the optimum amount of lime (5 %) and CFA (16 %) were determined. Using these percentages further performance evaluation was effected. Cylindrical samples were compacted at optimum moisture content (OMC) and cured for 28 days for resilient modulus (M_R) and UCS tests. Laboratory tests revealed that the M_R and UCS of soil increased substantially with the addition of both lime and CFA compared to those of raw soil at OMC. The M_R value increased from 50 Mpa of the raw soil to 250 Mpa of its stabilized counterpart, and the UCS improved from approximately 100 kPa to 1000 kPa. In addition, 3-D swelling and Tube suction tests (TST) were conducted on cured samples to determine swelling and moisture susceptibility behaviors; however, the volume change was minimal, from 1651 cm³ to 1664 cm³, and the dielectric constant decreased from 30 to 20. The scanning electron microscopic (SEM) studies showed a change in the soil fabric with the formation of some crystals and qualitative changes in the densification resulting from the mastic filling part of the original voids. Finally, the change in the plasticity index was observed to be from 22 % to 10 %, a manifestation of the ameliorating effects of stabilization.

Lime treatment is a widely used method for stabilizing expansive soils. In certain types of clayey soils, the stabilization is ineffective, mainly due to the complex reactions of stabilizer with the Montmorillonite clay mineral (MM). Hence, a research study was conducted with an objective to understand the impacts of various lime dosage levels on the engineering performance of clays containing different amounts of montmorillonite mineral fraction. A series of experiments were carried out on three types of expansive clays stabilized with quick lime. These experiments included unconfined compressive strength and three dimensional volumetric swell strains on soil specimens subjected to durability studies. The higher the MM content of a soil, the treated soil has shown vulnerability to undergo premature failures. Results also showed that MM fraction has considerable influence on the stabilizing ability of the soil.

Some published material has shown the existence of the creep behavior in sands. To investigate the creep behavior of Yangtze River sand, a series of lab tests were conducted using a high-pressure compression setup developed for this study. The sand was compressed under pressures of 800, 1600, and 3200kPa. The results demonstrate particle crushing is partly responsible for the sand creep. To investigate the particle breakage during the creep process, the Yangtze River sand was also tested under a pressure of 800kPa for five different periods (i.e., 0.5, 1, 10, and 100min). The conclusion can be made from the sieve analysis test results that the particle breakage was associated with the sand creep developing.

Test results from an experimental investigation undertaken at the University of Texas at Arlington on small-strain shear modulus response of residual and saprolitic soils sampled from a graniodiorite rock in the region of Antioquia, Colombia, are presented. Residual and saprolitic soil specimens were tested for different isotropic (total) stress states under natural and statically compacted conditions. Natural samples were tested in a conventional resonant column device, whereas compacted samples were tested in a novel resonant column device featuring self-contained bender elements, which allows for the simultaneous determination of shear wave velocity and small-strain shear moduli using both techniques. Results show that the G_max increases with the level of confinement in a very distinctive fashion according to the weathering intensity of the test materials. Moreover, there is a reasonably close correspondence between values of shear moduli obtained from bender elements and those obtained from resonant column in compacted samples tested up to 200-kPa isotropic stress levels. Shear wave velocity values are also compared with those previously determined in the field in a similar weathering profile using down-hole testing. Test results were proven to be consistent with those reported by previous authors in similar soils and using different testing techniques.

Expansive soils are those that expand when hydrated, and shrink when they were drying. These soil movements cause extensive damage to buildings, roads, pipelines, and other structures and the repair costs are estimated to be billion dollars annually. Expansive soils cover across most of the continents in the world, including several regions in the Saudi Arabia. For example, the regions including Tabuk, Al-Hafuf, Al-Qatif and Al-Ghatt have expansive soils and several infrastructure problems were reported in these regions. A research study was conducted at the King Saud University to characterize the severity of problem natures of these soils. Soil samples from these regions were collected and cataloged and these soils were subjected to a multitude of geotechnical related swell and shrink characterization studies. Three dimensional swell and linear shrinkage bar tests were conducted on these soil samples at targeted moisture contents to measure their volume change potentials. Severity nature of these expansive soils is then characterized based on an established swell/shrinkage ranking method practiced in the expansive soils literature. This paper presents a summary of these results and ranking assessments on the four expansive soils.

Clayey soil found in coal mines in Appalachian Ohio is typically used for constructing Recompacted Soil Liners (RSL) in landfills. The suitability of mined clay for RSL in Ohio is first decided by its clay content. Even though the standard sampling and processing techniques should not produce different grain-size distributions, mined clay from Appalachian Ohio is an exception. This discrepancy poses a challenge to the geotechnical engineers who work on prequalification process of RSL material. This paper describes a laboratory investigation conducted on mined clay from Appalachian Ohio to determine how and why the standard sampling and/or processing methods affect the grain-size distributions. About a 10 percent decrease in the clay content was consistently observed in the samples obtained from clayey soil stockpiles, compared to those collected during reverse circulation drilling. It was discovered that the fragments of shale in underclay was responsible for the discrepancy.

Better understanding the erodibility of a given type of soil can help predict scour at bridge piers more accurately. In the past, researchers have looked into erosion of soils with the ultimate objective of understanding the erodibility with respect to the other geotechnical properties. Most research has shown the difficulties associated with correlating erodibility to any one soil property. The research described in this paper is about an investigation on erodibility and dry unit weight of soil with varying fractions of fines. Soils tested using laboratory Jet Erosion Test (JET) indicated that the logarithm of erodibility makes a linear inverse relationship with the dry unit weight. In situ JETs confirmed the range of erodibilities established by the laboratory JETs. The best correlations between erodibility and dry unit weight appeared within a single category of soil as classified by the Unified Soil Classification System.

In this investigation an attempt has been made to assess the stress-strain and interfacial frictional behavior of geotextile reinforced residual soil with different stress path tests. In detail, the research program concentrated on the study of normally consolidated drained triaxial compression tests of unreinforced and reinforced residual soil on sample size 100 mm diameter and 200 mm high compacted residual soil. Testing was carried out at consolidating pressures ranging 100–600 kPa using a computer control triaxial apparatus. Test observation indicated that the geotextile reinforced soil increased shear strength properties of residual soil in a significant manner. From the result it was also found that reinforced soils exhibit higher failure strains and volume contraction than unreinforced soil. Failure strains, volume change and the percentage increase in strength over soil were also stress path dependent. The simplified prediction procedures to determine the strength of reinforced and unreinforced soils for various stress paths were presented. Charts were also presented to predict the strength of reinforced soil and to determine the coefficient of the interface friction from test results and predictions are satisfactory.

In this paper, the strength and deformation behavior of pond ash under cyclic loading has been studied. A series of stress controlled one-way cyclic compressive triaxial shear tests were conducted on reconstituted samples of pond ash. Tests were conducted under undrained conditions with different cyclic stress ratios and relative densities. Initial effective confining pressure was kept at 200 kPa. A uniform cyclic sinusoidal loading at a frequency of 1.0 Hz was applied during shearing. Axial deformation and pore water pressure variations were recorded with respect to number of loading cycles. The rate of development of strain and pore water pressure were studied from laboratory experimental results and it shows that the rate is a function of number of loading cycles and applied cyclic shear stress amplitude. Results indicate that there is an increase in the liquefaction resistance with increase in relative density. Failure was considered at 5% total axial strain for all the samples.

This paper presents the results of a comprehensive experimental program to study the static and dynamic properties of calcareous sands from southwest Puerto Rico in an uncemented state (Cabo Rojo sand). For comparison purposes the paper presents experimental results from a comparison silica sand with a similar grain size distribution. The experimental program for both sands included: Index testing, XRD mineralogy, SEM imaging, direct shear tests, 1-D compression tests, Isotropic Consolidated Undrained (ICU) triaxials, and resonant column tests.

Many regions throughout Florida have shallow layers of plastic and organic soils under existing roadways. Due to low strength and extremely high compressibility characteristics of these soils, most of the roads built over these subgrades frequently exhibit vast amount of cracking, distortion, rutting and differential settlement, curtailing their useful life. This paper presents a case study in the use of a variety of pavement reinforcing products in an effort to alleviate excessive pavement distortion and degradation resulting from unstable foundation. A total of 24 test sections (each 500 feet long) were constructed which included 8 control sections, and 16 reinforced asphalt sections containing Glasgrid, PetroGrid, PaveTrac and Asphalt Rubber Membrane Interlayer (ARMI), at 2 different test locations representing significantly different site characteristics. Prior to rehabilitation, Falling Weight Deflectometer (FWD) tests were conducted at every 50 feet along the proposed test section alignment for evaluating the existing pavement capacity, and statistically determining the site variability among the test sections. Six months after the reconstruction project, FWD tests were repeated at the same locations ascertaining relative performance improvements of the test sections. The stiffness/strength of the test sections increased moderately, owing primarily to the reinforcements. The pavement performance over time, however, could be different depending on several factors, such as interlock between the grid and the asphalt and the restraint provided by each reinforcement; therefore, monitoring will continue for several years.

In September 2007, lots of slope collapses and landslides were occurred in Southern Jeolla Province in Korea due to heavy rain that was accompanied by Typhoon "Nari". The investigated slope is one of the areas affected by the typhoon. The Slope is 20m in length and has a maximum height of 22m. The slopes are made of pyroclastic rocks with highly developed faults and cracks while the residual soil is made of a yellowish mudstone layer which was a result of severe chemical and physical weathering.

Defect details in bored pile and drilled pier foundations are presented for multiple installation methods to a depth of 70 ft (22 m) in projects along the Texas Gulf Coast. Over 2000 bored pile and drilled pier foundations covering four projects are reviewed.

In Algeria during ten year ago, waste disposal has become a particularly sensitive issue. A new legislation concerning landfill liner design was adopted. Traditional methods of landfills liners characterization involve soil sampling and chemical analysis, which are costly, destructive and time-consuming process. New techniques are being investigated to provide non-destructive, liners characterisation. This paper details technical aspect associated with electrical conductivity measurements within landfill liners and presents experimental work to show the direct application of electrical techniques to track ionic movement through sand bentonite liner under chemically induced flow. Samples of sand bentonite were mixed and compacted with NaCl electrolytes at different concentrations. Electrical conductivity of compacted specimens was measured with a two electrode cell. The effects frequency and electrolyte concentration are introduced on the conductivity measurement. Also relationship between soil electrical conductivity and NaCl electrolyte concentration in interstitial pore fluid are determined. The conductivity measurements were used to quantify the pore fluid concentration and effective diffusion coefficient of sand bentonite liners. It is concluded here that the electrical conductivity of compacted specimens depends mainly on the salt concentration in the pore fluid and it could be used to track ionic movement through liners during diffusion.

Microtremors are measured and analized by spatial autocorrelation method (SPAC) for determination of shear-wave velocity (Vs) models. In SPAC method, estimating Vs profiles is a two-stage process. Conventionally, Rayleigh wave phase velocity dispersion data, which are obtained from SPAC coefficients, are inverted for the shear-wave velocity models. In this study, a more practical (one-stage) scheme is utilized where the SPAC coefficients are directly inverted for unknown shear-wave velocities. The method is based on a weighted damped-least squares solution. Stability of inversion is achieved by using differential smoothing approach that provides Vs models in which the velocity differences between adjacent layers are minimized.

Two-dimensional seismic refraction microtremor data were acquired, processed and interpreted for the Honolulu High-Capacity Transit Corridor Project — west of Honolulu, Oahu, Hawaii. The objective was to image the lateral and vertical extent of soft-soil conditions and determine the depth-to-bedrock. Approximately 4.28-line km (2.66 miles) of two-dimensional (2D) refraction microtremor (ReMi) data was acquired along 12 lines. Data were acquired along the Farrington and the Kamehameha Highways. Line locations were selected to obtain additional subsurface information between and below geotechnical borings. Results indicate that thick soft-soil conditions exist; and, that the basalt bedrock has considerable relief. The bedrock can be encountered as shallow as 1.5 m (5 ft), to as deep as 70 m (230 ft) in this area beneath the existing highways. An innovative application of 2D seismic testing successfully mapped the lateral and vertical variability of the soft-soils beneath areas with very high traffic volume, without interrupting vehicle flow.

The existing attenuation equation is examined to evaluate the reliability for ground vibration attenuation induced by high-speed trains. Several representative attenuation coefficients are applied to predict ground vibration and then compare them with field measured results for high-speed trains on bridge and embankment. Based on these analyses, the results are comparable for both bridge and embankment structures, and the existing attenuation equation can be used to reasonably predict ground vibration. Attenuation coefficients based on each one-third octave band center frequency and the frequency range for predicting ground vibration are more reliable and consistent. A simple and general methodology for the attenuation of ground vibration by high-speed trains is proposed for engineering practice.

A rugged and geologically complex site proposed for construction of a 1 million gallon water storage tank was investigated using geologic, geophysical, and geotechnical methods. Preliminary investigation confirmed that the site is underlain by highly fractured and extensively mineralized metamorphic parent rocks and igneous intrusions. Mine workings were identified in the vicinity of the proposed tank excavation. However, record drawings were not available to show the extent of mining that had occurred.

The application of modulus-based in-situ testing methods has been widely increasing for control of the compaction quality of earthwork construction in recent years. Since their introduction to the QA/QC process, it has been observed that there are several factors that influence the measured modulus of the soil, such as moisture content, influence depth, and temperature. To achieve more reliable test results, these factors should be accounted for in interpretation of the data. As noted by previous researchers, water content is one of the most important properties that affects the modulus measurements of compacted soil. To explore the sensitivity of measured modulus-based in-situ test results to the effect of compaction water content, a field study was performed in the State of Delaware in the summer of 2008. Two Light Weight Deflectometers (LWDs) were used in the study to measure compacted soil modulus values, one with a 300 mm contact plate diameter and one with a 200 mm plate diameter. The fill material tested during this study was a poorly graded sand with silt (SP-SM). The purpose of the current paper is to demonstrate the sensitivity of the measured soil modulus values to fluctuation in soil moisture content in the field, and to discuss possible approaches for interpreting this type of variable LWD data.

The reliable evaluation of shear stiffness in soft soils has become increasingly more important. Furthermore, the void ratio is an important design parameter in soft soils for the evaluation of soil behavior. The purpose of this study is to assess the elastic moduli and void ratios based on the compressional and shear wave velocities by using the penetration type Field Velocity Probe for void ratio(FVPe). The compressional and shear waves are obtained by using piezo disk elements and bender elements. The penetration tests are conducted in the using calibration chambers. The sand-clay mixtures are mixed at the liquid limit of 46% using a slurry mixer. After the specimen is consolidated, the FVPe is progressively penetrated. The elastic waves are measured at 10mm intervals. The elastic moduli and void ratio are estimated by using the compressional and shear wave velocities. This study suggests that the FVPe may be a useful tool for the evaluation of the elastic moduli and void ratio based on compressional and shear wave velocities in soft soils.

It is widely known that weathering has a negative effect on the physical and engineering properties of rock. The variably weathered near surface limestone bedrock in Florida presents a challenge to geotechnical engineers who must incorporate physical and engineering properties in their design. Twenty-two specimens of Ocala limestone were obtained from a geotechnical test site in central Florida. Weathering was assessed in the specimens by using the International Society of Rock Mechanics (ISRM) weathering scale and surface textures. Unit weights, compression wave velocities from free-free resonant column (FFRC) tests and unconfined compression tests were performed on the specimens. Weathering was then incorporated into the relationship between unconfined compressive strength (UCS) and compression wave velocity. Results showed the specimens with the lowest ISRM weathering state had the highest correlation between UCS and compression wave velocity, specimens with high unit weights had well defined positive trends between UCS and compression wave velocity, and specimens with pitted and pitted to vuggy surface textures had strong positive relationships between UCS and compression wave velocity. Furthermore, it was found that other variables aside from the limestone weathering state influence the relationship between UCS and compression wave velocity.

A new I-10 Twin Span Bridge over Lake Pontchartrain is being constructed to replace the existing bridge, which was heavily damaged by Hurricane Katrina in 2005. The elevation of the new bridge will be higher, making it less vulnerable to high storm surge. The bridge will be supported by groups of battered pile foundations. In order to verify the analysis method used in the design phase, LADOTD decided to install a health monitoring system on a selected M19 eastbound bridge pier of the main span. The system includes both sub-structure and superstructure instrumentations for use in short-term monitoring during a static lateral load testing and for long-term monitoring during selected events such as wave, wind, and vessel impact. A unique lateral load test was designed and conducted at the M19 pier to assess the validity of the analysis method used to design pile foundations. This paper will present the development of the sub-structure instrumentation plan of I-10 Twin Span Bridge and its use during the lateral load test.

Bridge scour monitoring using fixed instrumentation is a good way for the owner to be warned of imminent failure and take appropriate action before exposing the public to undue risk. The paper shows an easy way to predict imminent failure of bridges by installing a motion sensor on the bridge. A large scale lab test is described in the paper, and a relationship between the natural frequency of the bridge and the scour depth is presented. It is shown that the natural frequency of the simulated bridge-foundation system changes with time and becomes drastic near failure.

This study aims at presenting an integration of different downhole prospecting techniques for hydrogeologic investigation in an active landslide area. A series of subsurface exploration technologies were conducted, including borehole image scanning, electric logging, groundwater velocity measurements, and double packer testing. Both acoustic and optical borehole loggings as well as electric logging were applied to identify lithology, water bearing capacity and fracturing of the formation around the boring. Subsequently, borehole flow logs were used to indicate the distribution of permeability and hydraulic connectivity of fractures along the borehole. Based on the above prospecting results, test sections of hydraulic tests can be arranged. Finally, hydraulic packer tests were carried out to further characterize the hydrogeologic system of the site and quantitatively determine the hydraulic properties of major hydrogeologic units. Integrating multiple downhole prospecting techniques on slope hydrogeology investigation not only provides hydraulic properties for a study area, but also brings information to establish a hydrogeologic conceptual model and process the model simulation.

This study is to evaluate the in-situ properties of Jeju sands, which are the beach sands derived from volcanic rock and shells, from the cone penetration tests on the specimens prepared in a calibration chamber. A unique characteristics of Jeju sand is relatively large extreme void ratios (emax=1.439, emin=1.026), which result in a large deformation during compression test. Test result shows that the cone resistance of Jeju sand is closely matched to that of predominantly quartz sand with high compressibility. It is also observed that the relative density and confining stress affects the constrained modulus less significantly than cone tip resistance, because of the crushing of calcareous materials contained in Jeju sand.

In this study, small sized micro cone penetrometers with 3mm, 5mm and 7mm outer diameters are designed and manufactured in order to evaluate the dimension and shape of the smear zone of prefabricated vertical drain (PVD). The tip resistance is measured by using strain gauges and fiber optic sensors attached near the micro cone tip. The PVD smear zone is investigated by a series of radial penetration tests in the clay specimen prepared in a large-scale consolidometer. Almost constant value of the cone tip resistance is measured within the undisturbed zone. The outer boundary of the smear zone is identified as the location where the deviation of the measured cone tip resistance from the constant value is observed. In addition, the significant change in cone tip resistance is observed in the smear zone with remarkably consistent patterns. This study shows that the PVD smear zone has the asymmetric shape and is effectively detected by using micro penetrometer.

Undrained shear strengths (su) play important roles in geotechnical designs. In the context of geotechnical reliability-based design, reducing uncertainties in su can be an important research topic. There are at least two ways of reducing uncertainties in su: conduct (1) laboratory or (2) in-situ tests to obtain indices or parameters to correlate su indirectly. The way of reducing uncertainties in su can be challenging. The challenge lies in the fact that the so-obtained indices and parameters, e.g. CPT tip resistance, cannot be directly used to estimate su but can estimate su only through correlations. Above all, there is a challenge in combining information: how to reduce uncertainties in su when there are multiple sources of information? In this paper we will address the aforementioned challenges and propose a probabilistic framework to handle these difficulties. Sets of simplified equations will be obtained through the probabilistic analysis for the purpose of reducing uncertainties: the inputs to the equations are the results of in-situ or laboratory tests and the outputs are the updated mean values and coefficients of variation (c.o.v.) of the desirable undrained shear strengths. The uncertainties in su will decrease when the number of inputs increase, i.e. more information is available. The results of this research may be beneficial to geotechnical reliability-based design.

In this paper, existing methods for interpreting coefficient of consolidation in clays from piezocone dissipation tests are briefly reviewed. Piezocone tests have been conducted at different sites in Jiangsu province of China. Piezocone dissipation tests were performed at different penetration depths. Two existing interpretation methods were made on the CPT dissipation data analyzing both monotonic and dilatory pore pressure decay behaviors. The interpreted values are compared with the reference c_v values determined from the laboratory oedometer tests. It is shown that the CPT interpretation values are generally four times larger than the c_v values obtained through conventional oedometer test for Jiangsu Quaternary clay deposits. The values of c_vh obtained by the CPTU method are in the range of back-analyzed field values.

The cone factor is commonly used to relate the CPT cone resistance to the undrained shear strength in saturated clays. Uncertain aspects however still exist, including the soil pressure correction procedure and the variability of the cone factor itself. The soil pressure correction procedure requires the in-situ soil unit weight, and thus requires the process of undisturbed soil sampling. In the present paper, a new cone factor is presented, which can reduce the uncertainties contained in the conventional cone factor approach. The proposed cone factor does not require the soil pressure correction procedure. As a result, the soil disturbance-related uncertainties can be minimized at higher cost effectiveness as no undisturbed sampling is needed. Experimental test results adopted in this investigation are presented and used to validate the proposed method.

Suspension P-S logging is one of the available methods for determining the shear and compression wave velocity (V_S and V_P) profiles in both soil and rock formations. Measurements are made in single, uncased, fluid-filled boreholes. for nuclear power plants, nuclear regulatory guides provide guidance on conducting various field investigations to determine the site characteristics for the licensing of new generation units. Although these guides discuss surface and borehole geophysics to some extent, they do not specifically reference the suspension P-S logging method. However, because this method provides a specific measure of V_S and V_P at any chosen depth in the borehole (rather than interpretation from surface methods or integration through the soil column), it has been used as the main source of obtaining these velocities during site investigation and characterization for new nuclear generation work. This paper discusses the advantages (and some disadvantages) of this method for measuring V_S and V_P over down-hole (conventional and CPT) and cross-hole testing procedures. The results of multiple suspension P-S logging measurements are presented for two different sites, in soils and rocks that range from soft clays to silty sand to partially weathered/sound rock, to depths of over 120 m.

Hybrid in-situ penetration-geophysics tests offer an optimal and efficient means for geotechnical site characterization, including geostratigraphy and the interpretation of soil engineering parameters. Specifically, the seismic piezocone penetration test (SCPTù) provides up to 5 independent readings with depth in the same sounding: q_t, f_s, u₂, t₅₀, and V_s; as does the companion seismic flat dilatometer test (SDMT): p₀, p₁, p₂, t_flex, and V_s. The continuous readings of the cone penetrometer (1-cm readings) and near-continuous readings of the dilatometer (at 20-cm intervals) provide detailed layering, strata changes, and detection of lenses and weak zones in the subsurface profile, as well as provide a suite of geotechnical parameters towards the quantification of soil type, strength, stress history, stiffness, and permeability.

This study presents site classification using 30 m average concept and newly proposed soil average by considering 30 sets of boreholes and shear wave velocity data. Shear wave velocity (V_s) is measured by carrying out multichannel analysis of surface wave (MASW) survey close to the boreholes drilled up to standard penetration test (SPT) N value of up to 100 for no penetration. The SPT N and Vs values have been used to calculate 30m equivalent N (N₃₀) and Vs (Vs³⁰) values. These sites are classified and compared according to National Earthquake Hazards Reduction Program (NEHRP). Study shows that Vs based classifications are better representations for shallow overburden sites, compared to SPT. The amplification factors are estimated using Vs³⁰ and empirical equations, and compared with amplification factor from site response studies. Further, applicability of SPT N values and average 30m values are investigated for shallow engineering bed rock sites.

This paper presents the results of an investigation program conducted at different sites in the northeast region of Nile delta. This area happens to be a priority investment area for the Egyptian government where a number of huge projects are in progress. In situ tests; flat dilatometer (DMT), mechanical cone penetration (CPT), and vane shear (VST), as well as laboratory tests were performed in order to characterize the geotechnical properties of the clay deposits. These properties include soil classification, stress history, and undrained shear strength. The most commonly used correlations of these soil parameters with the in situ testing results are examined in light of direct laboratory measurements. This study emphasizes the key role of in situ tests as rapid and economical profiling tools that are able to provide useful information on a wide range of soil properties. However, the published correlations need always to be validated to suit local soil conditions. It is shown that these correlations mostly do not appear to hold for the investigated region, and hence area-specific correlations instead are developed.

The application of seismic methods in geotechnical site investigation is used to determine the initial shear stiffness in soils. Specific information about the reliability and the trust regions at the determined soil profiles are necessary to use these methods in geotechnical design processes. Therefore, experiences show that higher modes in seismic surface wave fields should be considered. Due to non-unique inversion processes a trust region and a reliability of the soil profile has to be given for geotechnical design processes. The reclaimed mining areas are loose artificial landfills of sand, silt and clay with depth up to 100 m with rising ground water levels. These areas offer a large geotechnical risk for the foundation of wind power stations up to a height of 140 m. To reduce the design risk and decrease the costs a combination of conventional tests, seismic field tests and supplemental laboratory tests are proved to get the significant increase in information about the true static and dynamic soil parameters.

Some geomaterials (soils and rocks) exhibit direction dependent linear elastic stiffness values due to their geological formation processes. This paper presents a numerical study, using ABAQUS finite element program, to investigate the effect of cross-anisotropy of geomaterials on the initial elastic pressuremeter response, in terms of K_i, i.e. the tangent to the initial portion of the Δ_p vs. ΔV / V_o curve, where Δ_p? is the change in the applied membrane pressure, Ä V is the change in the membrane volume due to the applied membrane pressure, and V_o is the initial volume of the membrane. The FE analysis results for the relationship between _i and the dip angle θ, defined as the angle between the plane of anisotropy and axis of the pressuremeter membrane, show that K_i increases with increasing sinθ up to 0.79 (i.e., θ=52°). Thereafter, K_i decreases slightly with increasing sinθ for the range between 0.79 and 1 (i.e., θ between 52° and 90°).

Shear wave velocity (V_s) is a key parameter for seismic amplification analyses, and for assessment of liquefaction potential of loose offshore sands. A number of methods are available to measure V_s offshore, including seismic Cone Penetration Testing (CPT), Multichannel Analysis of Surface Waves, and Downhole methods. A marine investigation was carried out offshore Croatia for a new bridge connecting the Croatian mainland to the Peljesac peninsula. During the investigation, direct V_s measurements were taken with the three methods outlined above. This paper presents the data acquisition, processing and results. Advantages and limitations of the three methods used for the survey are discussed.

FFEB JV has carried out more than 3,000 incremental consolidation tests on 101.6-mm (4-in) diameter undisturbed samples from the Gulf Coast, following ASTM D2435 Method A (24-hour duration for each load increment). As a preliminary analysis, 330 incremental consolidation results were randomly selected and analyzed. The analysis included silt, lean clay, fat clay, organic clay and peat materials. The end of primary consolidation was obtained from the Casagrande curve construction method. It was found that for most of the inorganic samples tested, a time duration less than 12 hours was enough to exceed the end of primary consolidation. While typically 2 weeks are needed to finish an incremental consolidation test using Test Method A, the analysis results suggest that a decreased load duration may reduce testing time to less than a week. The analysis results can be used as a useful reference for the incremental consolidation Test Method B.

The shear wave velocity profile of a soil column is often used to assist in the characterization of a site. Most often, this column consists of native, undisturbed materials. If backfill is required for the final site configuration, the shear wave velocity of the backfill is typically estimated from empirical relationships. Very seldom are measurements of the backfill made to obtain a site specific shear wave velocity profile.

Identifying stratigraphic changes from coarse to fine-grained soils was one of the primary goals of the subsurface investigation performed for a deep foundation project in Boston, Massachusetts, USA. A drilling parameter recorder (DPR) was used during the advancement of a tri-cone roller bit through the overburden glacial soils to aid in identifying changes in soil stratigraphy. By correlating soil samples obtained from 2-inch split spoons with the trends in the drilling parameters, it was possible to identify changes in stratigraphy in other boreholes based on the DPR data alone. The correlations were used to reduce the frequency and number of split spoon samples taken and ultimately increased the efficiency in which the borings were completed. In addition, DPR was used to record the drilling parameters during rock coring to better identify natural fractures in the formation. By correlating the trends in the DPR data with the physical characteristics of the bedrock core specimens, it was possible to identify zones of more fractured rock, and select depth intervals in which to perform packer tests. The results from the investigation were used to determine the design depth of a reinforced concrete diaphragm wall.

for preparing large granular specimens in the calibration chamber, most previous studies have used the pluviation technique adjusting the deposition intensity while maintaining a constant drop height. This study introduces a rainer system improved by adopting a porous plate. This system controls the relative density of the specimens by adjusting the drop height without changing the deposition intensity. From a series of laboratory tests, it is revealed that an improved rainer system with a porous plate is capable of reconstituting a granular specimen with a wider range of densities than a conventional rainer system. It is also observed that using the rainer system with a porous plate significantly improves the vertical and horizontal homogeneity of the specimen.

The resonance frequencies and site amplifications of a proposed development site on the Penrith campus of the University of Western Sydney have been studied by means of a non-invasive ambient noise Horizontal to Vertical Spectral Ratio (HVSR) method. Unlike other non-invasive surface wave techniques (such as the SASW, MASW, CSW etc) which require an array of connected sensors, the HVSR technique is a single station method requiring no such connection. Moreover, the HVSR technique is a passive method in relying only on the ambient microtremors caused by natural events (tides, large-scale meteorological conditions) and cultural activities (industrial machinery, cars and trains) as excitation sources. This paper presents one part of a study which aims to characterise the site effects and layered soil stratigraphy of a development site at the Penrith campus. In this study, measurements of the ground responses in the vertical and two orthogonal horizontal directions were carried out using a lightweight battery operated, wireless 3-component digital tomograph. The estimated HVSR curves, the resonance frequencies and site amplifications, and interpretations of the results obtained for the site are discussed. The experience from this study indicates that this could be a low-cost and attractive technique having a great potential in near surface geotechnical characterisation of urban sites. Further investigation is currently being undertaken to study its efficiency and accuracy in establishing the S-wave velocity profiles and soil stratigraphy of the site by inverse analysis of the HVSR curves.

The existing Lady Bug Point Bridge within the 10 million m² Winton Woods Park in Cincinnati, Ohio was closed in Winter of 2007, as a result of ongoing landslide movements under the south bridge abutment. An initial study indicated the landslide was triggered by bridge abutment loading, recent fluctuating lake water levels, and dredging activities. An extensive rock buttress fill at the toe of the abutment extending into the lake was suggested as a remedial option from the original investigation. However, the rock fill option was deemed expensive, and the fill placement permit process with USACE could be time-consuming. Due to the fact that the abutment movements had created tension cracks and settlements of over 10 cm in a short period of time, and endangered bridge integrity and public safety, a value-engineering study was conducted using both analytical and numerical modeling methods to estimate landslide forces. A structural system, consisting of twelve drilled piers and grade beams, was designed, capable of providing both slope stabilization and abutment underpinning. The extremely narrow clear space between bridge girders added significant challenges to the pier design and construction. The unique system was installed and the bridge was reopened for use in June 2008. The design was a collaborative effort between the geotechnical and structural engineers.

Landslides have been threatening infrastructures for decades. It is difficult to accurately predict the timing, magnitude, and location where movements will occur. Innovations in wireless and real-time inclinometer monitoring are replacing time-consuming tasks associated with manually collecting data from the field. In an effort to collect real-time data, multiplexed, 3-Dimensional, Micro-Electro-Mechanical-System based, in-place inclinometers have been deployed for two instrumentation monitoring projects; one at the crest of an interstate highway to monitor an active embankment landslide and one between slope stabilization piers for a hillside revitalization project to confirm slope stabilization design. Another case utilized a conventional analog type in-place inclinometer for comparison purposes. Short-range wireless receivers and/or long-range cellular transmitters were setup to transmit field data to the office. The office computer autonomously entered the data into a relational database for archiving, calculated field data using pre-programmed equations, triggered text alarms, and produced useful plots on a password-protected website. New generation inclinometers connected to a wireless remote platform have become a very valuable monitoring tool for slope monitoring and enhancing the safety of our public infrastructure.

The failure of a slope along a segment of Highway 8 near Harrisonburg, Louisiana resulted in its partial closure in December 2008. The Louisiana Department of Transportation and Development needed to assess the damage and find a way to remedy the problem. Soil borings were taken and the slope was monitored using a vertical inclinometer. Then the aerial photos were used to evaluate the site conditions and map the progress of slope failure over time. Further, a series of laboratory tests were performed on the samples obtained by boring from the site to determine the stress path followed by the soil which led to the slope failure. Laboratory testing program included conventional unconsolidated undrained (UU) triaxial tests, multistage consolidated undrained (CU) triaxial tests, and K_o-consolidated undrained (CKoU) triaxial lateral extension tests. Using the extensive laboratory test results, the soil design parameters were selected for slope stability analyses. The limit equilibrium analyses showed different results based on parameters obtained from different stress path testing. Further, partial stabilization at the toe of the slope was recommended as the most suitable remedial measure.

On-going studies of the flood-control levees in the Sacramento Valley in California have included airborne EM and magnetic surveys, geomorphologic studies, DC resistivity surveys, cone penetrometer testing and reverse-circulation borings. This paper reports on how airborne EM is being used in conjunction with these methods to provide a regional overview of the levee foundations, tie-together and extend the ground information, as well as provide mapping of the horizontal extent of sand channels.

Normally forensic engineering is applied to the analyses of a structure or anthropogenic material that has failed or undergoes unacceptable deformation. However, in a sinkhole investigation one does not normally consider all forensic information available. This paper provides a discussion of forensic methods and techniques available to geotechnical engineers in the investigation of foundation conditions where distress is caused by sinkhole activity. It discusses tools for analyzing and interpreting the natural conditions present in the investigation. An example is given of an investigation where forensic engineering should have been used to determine the cause for distress in a building.

Geogrids have been successfully used to improve soft subgrade and reinforce weak base course by providing lateral confinement. However, uniaxial and biaxial geogrids cannot provide uniform resistance in all directions. A new product termed "Triaxial geogrid" was developed to overcome this limitation. The triaxial geogrid is expected to have a more stable grid structure to provide uniform resistance in all directions as compared with uniaxial and biaxial geogrids. However, the effects of the triaxial geogrids on the performance of reinforced bases have not been well evaluated. In this study, unreinforced and triaxial geogrid-reinforced bases over a weak subgrade were constructed in a large geotechnical testing box (2m x 2.2m x 2m high) at the University of Kansas and tested under cyclic loading. During the tests, the surface deformations and the vertical stresses at the interface between the base and the subgrade were monitored. The test results showed that triaxial geogrids increased percentage of resilient displacement and reduced permanent displacement and vertical stresses at the interface as compared with the unreinforced base.

The anisotropy on shear moduli for K₀ consolidated clay is studied by performing small-strain triaxial tests and bender element (BE) tests on reconstituted Taipei silty clay specimens at different consolidation stresses. The newly developed triaxial testing system was equipped with a high-precision servo motor, a digital pressure controller system, and local measurement sensors. All the specimens were consolidated under the K₀ condition and then subjected to undrained shearing. The bender element tests were conducted along with the process of the K₀ consolidation, and the variation of shear moduli in different orientations with the changing in consolidation stress was observed. The shear wave velocities in two different directions were measured in undrained shearing stage by bender element tests as well. The test results showed that: 1) the shear modulus obtained from the shear wave propagating and vibrating parallel to the bedding plane, i.e. G_hh, is higher than G_vh for clay at K₀ state, 2) the empirical expressions for calculating the anisotropic shear moduli based on function of void ratio, OCR, and stress states were established, 3) the anisotropy for shear moduli measured from bender element tests was observed in the shearing process as well as in the consolidation stage.

In the present research the procedure for determining Rock Impact Hardness Number (R.I.H.N.) is being investigated. Experiments were carried out on marble and sandstone specimens, by using the earlier original procedure and a modified method. The preliminary results of the research indicate that the suggested approach is advantageous when it is necessary to better understand the variability of strength values in heterogeneous rock materials.

This project involved placing instrumentation on driven piles used on a bridge abutment in order to monitor downdrag effects due to negative skin friction. The overall scope included placing vibrating wire strain gages on a number of closed-end steel pipe piles and measuring the change in strain in the piles with time as consolidation occurred due to placement of backfill material after the pile driving process was completed. The instrumentation allowed the magnitude of downdrag forces to be monitored, providing field data as to the negative skin friction acting on the piles. It also provided the opportunity to compare the response of Teflon-coated piles versus uncoated piles. Having instrumentation on a variety of piles has provided a valuable collection of data that will offer better insights into the downdrag phenomenon. The purpose of this paper is to share some lessons learned in the instrumentation process and to provide insights to others as additional research occurs in the future.

In the stability analysis of Asato and Tyunjun landslides, the average shear strength acting along the slip surface has been calculated utilizing results of laboratory shear tests of the slip surface soils. For the Asato landslide, which is a large-movement along the whole slip surface, it is considered that most of the slip surface zone has been lying at residual state and the remaining parts at fully softened state. Average shear strength parameter, (¯c^'¯φ^' acting along the slip surface has been determined as ¯c^' = 0 kN/m² and ¯φ^' = 12.3°. Thus, the average shear strength was close to the residual strength, which is reflected in the well-defined slickenside on the slip surface. For the Tyunjun landslide, the slip surface consists of a fractured-mudstone zone in the toe part and slickenside in the upper/middle part. In the stability analysis, it is considered that in the upper/middle part of the slip surface residual strength has been mobilized, while in the toe part peak strength of the fractured-mudstone has been utilized. Thus, the calculated average cohesion for entire slip surface is greater than zero.

The measurement schemes and methods for analysis of ground vibration induced by passing trains on bridge structures are presented. The rail system consists of mass rapid transit and high-speed trains. The issues influencing the vibration measurement are discussed. Based on a wide variety of field measurements, the main vibration characteristics induced by passing trains are introduced. These characteristics include geological condition, frequency factor, vibration attenuation, structure type, and train speed. These factors are evaluated using the examples of field measurement results. Finally, some analysis recommendations and further studies are proposed.

Shear deformation behavior of the cemented interface between concrete and argillaceous siltstone was investigated by means of large-scale field shear tests conducted at the construction site of the Ganjiang Bridge. Based on the field test data, three stages of deformation were presented. Moreover, three failure modes of the cemented interface were established according to the behavior of each sample. Factors affecting the failure modes were also discussed. The relation between shear and normal stress indicated that dilation existed during shear tests. In addition, the shear strength for shear and friction tests was estimated from the testing results in consideration of field actual conditions.

The objective of the study presented herein is to show the usefulness of photoelasticity, in conjunction with digital image processing, for determining stresses in geotechnical laboratory tests. To illustrate this, photoelastic sensors were manufactured and calibrated to determine the lateral stress during loading and unloading in a 2-dimensional granular assembly under K_o conditions. The sensors are square glass plates with a circular opening in the center, which results in stress concentrations around the perimeter of the opening and thereby increases the sensors sensitivity. Using digital image processing to quantify the intensities of light colors in the photoelastic sensors according to red, green, and blue (RGB) components, it is shown that R-intensity is the most sensitive to applied stress and was thus used to determine induced stresses. The procedure used to calibrate, as well as the resulting calibration charts, are discussed in detail.

Unintrusive measurement of field modulus and moisture content of roadway subgrade and fill materials greatly enhances field control during construction. Establishing a measurement method in a laboratory setting provides an initial assessment of a tools possible usefulness in the field. An ultrasonic test system was used in this research in order to determine the wave velocities of cylindrical soil specimens in a laboratory setting in support of a Briaud Compactive Device (BCD) research project. The BCD is a non-destructive test method that can quickly determine soil modulus both in the laboratory and the field. Cylindrical soil samples of silt were compacted in two different molds: a standard proctor mold 152.4-mm (6-inch) diameter and a smaller 71.1 mm (2.8-inch) diameter mold. The p-wave and the s-wave velocities of samples manufactured in each of the molds were compared against sample moisture content and the dry unit weight. Trends in wave velocity versus moisture content were investigated using the two types of molds and compacting using two compactive efforts. It was found that specimens prepared in the two different molds generate similar trends of wave velocity versus moisture content. In general, the smaller compaction mold could be used for specimen preparation for ease in preparation, but care and experience are needed in order to match targeted dry unit weight values on a given compaction curve. Regardless of compaction mold sizes and compactive efforts, the wave velocities show the strongest correlation with moisture content. This ultrasonic test system is useful for calibration of the (BCD) in the laboratory setting, and could be applied to testing of samples extracted from the field.

Drilling a borehole is one of method to assess site condition and acquire design required engineering parameters. Acoustic and optic televiewers have been successfully applied for geotechnical application. Since each system has limitations for their application, a new system integrating the features of the systems is required. In this paper, features of opto-laser borehole scanner are introduced. Using the assemblage of the CCD camera and laser sensors, proto type of the system was developed and primitive level of image and laser scanned data set were obtained. From the image data, 0.1mm resolution of color data set could be obtained and from the laser scanned data, three dimensional features of target surface could be identified. The acquired data shows that the promising applicability of the opto-laser borehole scanner.

As an attempt to study systematically on the optimum source offset— the distance between source and the closest receiver— and total receiver spread length with the MASW method, we present our observations with modeling and field data sets indicating that the most accurate analysis of phase velocities can be accomplished only for wavelengths up to one spread length, and subsequent analysis for the longer wavelengths inevitably involves a certain degee of fluctuating inaccuracy that seems to originate from the Gibbs—phenomenon of Fourier transformation. The inaccuracy, however, seems to be within five percentfor those wavelengths shorter than twice the spread length. Also, results from the field data study suggest that importance of the source offset has been previously underestimated and the maximum wavelength can be extended simply by extending the source offset. In addition, they showedthat phase velocities tend to be underestimated if the source offset is smaller than one spread length. The degree of underestimation, however, appears highly site dependent and sometimes becomes negligible even if the source offsetis as short as only one receiver spacing.

Characteristic shear wave velocity profiles to 200 m depth were developed for basin-fill sediment types that predominate in the Las Vegas Valley. The profiles feed into a model that will be used to evaluate potential earthquake ground motions. Profiles were derived from a database that contains more than 1400 well logs and 200 velocity profiles. The sediment-type units used were predominantly clay, predominantly gravel, predominantly sand and mixed. Correlations between sediment type and shear wave velocity were derived from a subset of 76 shear-wave velocity profiles, most of which had at least one well log within 300 m. A single stepped velocity profile was created to represent each sediment-type unit. For each layer in each profile, the characteristic velocity was assigned using a histogram of velocities. Results demonstrate much variability but overall fit expectations that coarser grained sediments tend toward higher velocities and all velocities tend to increase with depth.

The concrete spillway associated with a small dam in Rapid City, South Dakota has evidenced persistent seepage since its construction in the 1970's. Visual inspection appears to indicate signs of worsening seepage. Geotechnical borings from dam pre-construction as well as modern boring logs taken on either side of the spillway have been consulted; however, budgetary, access, and logistical constraints restricted a more in-depth geotechnical boring program. A geophysical investigation was ordered to better define the subsurface stratigraphy. This data would be used to perform seepage/flow net analysis and determine some remedial solutions to mitigate seepage and extend the life of the structure.

The non-invasive seismic method of multi-channel analysis of surface waves (MASW) was utilized as part of a structural safety assessment of the 18.5 km (11.5 miles) long earthen Augusta Levee, Augusta, Georgia. This method was used to supplement the information derived from the conventional geotechnical exploration program which included soil borings, in-situ Standard Penetration Testing and collecting soil samples for laboratory testing. The findings from the MASW survey provided near continuous documentation of the subsurface conditions between the discrete soil test borings.

We proposed an integrated geophysical method which can non-invasively estimate soil condition of levees in order to evaluate their vulnerabilities. The geophysical method consists of a surface-wave method using a land streamer and a capacitively-coupled resistivity method. The method is mainly performed along levees at crest or levee toe in order to delineate lateral variation of soil condition. The effective performance of field measurements using these methods is assured because sensors are not fixed on the levee surface. We have also developed a cross-plot analysis of the measured geophysical properties in order to estimate soil type in body and base of levees. We have applied the method to many levees in Japan and evaluated the applicability of the method. In conclusion, the cross-plot analysis using S-wave velocity and resistivity obtained through the surface-wave method and the capacitively-coupled resistivity method provides reliable soil information of levee body and base.

The section of I-476 (Blue Route) between the Schuylkill Expressway (I-76) and the Mid-County Turnpike Interchange (I-276), Montgomery County, PA has a history of sinkhole activity. Where traditional drilling (unguided by geophysics) and a 2-D ERI (electrical resistivity imaging) survey proved partly effective, a MASW (multi-channel analysis of surface waves) survey linked a majority of sink activity (44 out of 52 reported sinkholes) to geologic conditions that included: enhanced weathering, the transition from shallow, competent rock to enhanced weathered rock, pinnacled rock, a potential fault or fracture, and potential voids. All of these features are expressed as differences in shear wave velocities (measure of material stiffness). The MASW survey was conducted in the southbound inside lane of the reinforced concrete roadway over the course of 3 nights, working between 10:00 P.M. and 5:30 A.M., averaging approximately 244 meters (800 feet) of continuous data per night. The process is documented in a 5-minute video (oral presentation only). The MASW survey explored to a depth of approximately 24 meters (80 feet) below grade, a difficult or impossible task by other geophysical profiling methods.

In a case where the active-source multi-channel analysis of surface waves method was applied to a site consisting of clay residuum overlying basalt bedrock, inversion for the fundamental-mode Rayleigh wave results in shear-wave velocities for the rock that are much lower than expected values. Preliminary results from multi-mode inversions incorporating data from the 1^st and 2^nd higher-order modes provide more realistic velocities within the bedrock than could be obtained using the fundamental-mode data alone. However, the model data fit shows much room for improvement. Acquiring, processing and interpreting multi-mode data poses some challenges that need further research.

This paper details research aimed at comparing the three most popular lineararray surface wave methods at a soft soil site in the Mississippi Embayment. As soft, normally dispersive soil sites are typically expected to be some of the most uncomplicated for surface wave propagation, this study provides a bench mark on the variability between surface wave methods at `easy' sites. The three methods considered are: (1) Spectral Analysis of Surface Waves (SASW), (2) Multi-channel Analysis of Surface Waves (MASW), and (3) Refraction Microtremor (ReMi). The dispersion curves and inverted shear wave velocity (V_s) profiles for each method are compared herein. The SASW and MASW V_s profiles are in good agreement, with less than 8% difference throughout. However, the ReMi V_s values are on average 25–35% different than the SASW and MASW V_s values. One cause for this discrepancy is the inability of passive ReMi measurements to resolve high frequency (short wavelength) data at the site.

The use of the methods based on the propagation of surface waves increased significantly during last decade. These methods give opportunity to evaluate the shear wave velocity profile from the ground surface without intrusion. The precise evaluation of V_s as a function of depth can find a large variety of application in geotechnical engineering since V_s is a fundamental parameter defined in the true insitu conditions. In order to evaluate V_s with precision, this paper shows through a number of examples the necessity to correctly isolate and use the different Rayleigh modes present in the field records.

An experiment using a microphone as a non-contact seismic receiver for surface wave testing of unbound pavement materials is presented. Measurements are based on the evanescent acoustic field in the air close to the soil surface. Results show that microphones can be successfully used to measure a surface wave dispersion curve comparable to a dispersion curve obtained with traditional contact receivers. This opens up the possibility for faster on-the-fly quality control of pavement layers since receiver surface contact is no longer required.

The Deccan basalt province controls the hydrologic regime of an area of ∼500,000 km² in the central India. These basalts are largely layered flows with massive, vesicular and amygdaloidal varieties. We have studied the basalt sequence in the Ghatia micro-watershed in Madhya Pradesh, India, using the multichannel analysis of surface waves at several sites. The shear wave velocity sections reveal the layered nature of the basalt sequence with a cap of low velocity weathered zones. In some sections, the weathering zones are undulating. Interestingly, in some of the massive flows, there are low-velocity vertical zones that can be interpreted to be either vertical columnar joints or tectonic fracture zones. It is suggested that the low-velocity weathered flows can be the good groundwater reservoirs, and the vertical low velocity zones can efficiently transport ground water from one flow to the other flows. Geotechnical applications of the results are also discussed.

This paper includes a comparison and discussion of the surface wave test results, as well as backgrounds of the MISW and SASW methods. The older Spectral Analysis of Surface Waves (SASW) and newer Multiple Impact of Surface Waves (MISW) test methods were performed at the same forensic investigation project on a concrete pavement underlain by a cement treated base, for comparison purposes. The older SASW and newer MISW methods differ only slightly from one another in the equipment used and method of data collection, but involve significantly different data processing. The SASW method greatly overestimates Young's moduli of less stiff base materials immediately below the much stiffer asphalt or concrete pavement layer. In contrast the MISW method is able to estimate the properties of these less stiff base materials immediately below the much stiffer pavement layers by accounting for higher order wave modes during the inversion process.

Mass mixing is one of main soil improvement methods by mixing the native soil and grout spoil to a relatively homogeneous mixture to increase the soil resistance. Numerical study using finite element method (FEM) of soil improvement effects by mass mixing on the lateral capacity of pile group in soft clay is presented. The clay is modeled by three-dimensional (3D) nonlinear pressure-independent elastoplastic solid elements, and the piles are modeled by one-dimensional (1D) linear elastic beam-column elements. The gapping between the soil and pile is taken into account using non-extension zero-length spring elements. The mass mixing block is also modeled as 3D linear elastic solid elements due to its relatively higher stiffness and strength than the surrounding virgin soft clay. The soil parameters are calibrated by simulating the lateral behavior of single pile in virgin weak clay, and of pile groups in virgin and improved soil. A series of parameter study including the depth and length effect of mass mix block, the effect of strength of mass mix on the lateral resistance of soil are preformed using the calibrated soil parameters and validated FEM model. Analyses show significant effect of mix depth and length and less significant effect of mix strength on the lateral capacity of pile group in soft clay.

The dynamic pile-soil-pile interaction under vertical motion is a very complex problem. In the present investigation, an attempt is made to study the dynamic response of pile groups in layered soil medium subjected to machine-induced vertical vibration by both experimental and numerical study. This paper presents the small prototype field test results of 2 x 2 group piles (L/d = 10, 15, 20 and s/d = 2, 3, 4) subjected to four different excitation intensities. Resonant frequency and amplitudes are determined from the observed response curves. The test results are used to develop models using artificial neural network (ANN). Different ANN models are developed using evolutionary learning algorithm and Bayesian regularization algorithms. Various statistical performance criteria are used to compare the developed ANN models. A neural interpretation diagram is presented showing the effects of input parameters. A model equation is also presented based on neural network parameters.

In recent years artificial neural networks (ANNs) have been applied to many geotechnical engineering problems with some degree of success. With respect to the design of pile foundations, accurate prediction of pile settlement is necessary to ensure appropriate structural and serviceability performance. In this paper, an ANN model is developed for predicting pile settlement based on the results of cone penetration test (CPT) data. Approximately, 300 data sets, obtained from the published literature, are used to develop the ANN model. In addition, the paper discusses the choice of input and internal network parameters which were examined to obtain the optimum model. Finally, the paper compares the predictions obtained by the ANN with those given by a number of traditional methods. It is demonstrated that the ANN model outperforms the traditional methods and provides accurate pile settlement predictions.

In this paper, closed form solutions were employed to predict nonlinear response of pile groups gained previously using FLAC^3D, centrifuge tests, and 1g model tests. The study shows (1) impact of pile-pile group interaction and high loading eccentricity is well captured; (2) The magnitudes of bending moment reported are not highly accurate in pertinent numerical simulations and model tests; (3) Quality tests, especially on large pile groups are required. Hand-calculation is elaborated via a typical example to highlight the features and use of the solutions to gain nonlinear response. It demonstrates the efficiency and accuracy of the solutions for relevant design.

In the Kaufman County area within the Texas Department of Transportation's Dallas District, several short drilled shaft foundations supporting three-cable median barrier systems were observed to be distressed during severe winter storm conditions in late 2006 to early 2007. A research study was initiated at UT Arlington to determine and understand the mechanisms causing these shaft failures. The ends of the three-cable median barrier systems are fastened to a single drilled shaft foundation. In general, these shafts are short in length and the same dimensions, diameter and length, are typically used for all soil conditions. This paper presents the initial tasks of this study which includes the estimations of loads on the shafts and the design of reaction test piers for the application of inclined loads on the test shafts simulating the field conditions. Lateral load analyses results are utilized in the design of reaction shaft dimensions and spacings between reaction and test shafts. Salient details of analytical approaches used for load calculations are also included.

The Rammed Aggregate Pier® foundation system serves as an alternative to deep foundations and overexcavation/replacement of compressible soils. Several case histories have documented the use of rammed aggregate piers for support of tanks, shallow foundations, retaining walls, and embankments. To investigate the mechanical behavior of the rammed aggregate pier system, numerical analyses of rammed aggregate pier foundations have recently been performed by several researchers. Even though the pier construction process is widely credited for the performance of rammed aggregate piers, these recent investigations have ignored or inadequately considered pier installation in the numerical modeling. This paper investigates how methods of modeling rammed aggregate pier construction influence predictions of the load-displacement response and material stress state of model piers. The modeling methods described in this paper involve: (1) prescribed cavity wall displacement, and (2) prescribed cavity volumetric strain. These methods are incorporated into finite element analyses of modulus load tests conducted on isolated piers. Effects of pier construction modeling method and magnitude of prescribed cavity expansion are investigated by comparing predicted pier load-displacement relationships and stress-dependent stiffness with the results from the field load tests. Stress paths of pier aggregate elements from numerical analyses incorporating the pier construction methods are also evaluated.

The paper presents a coupled hydro-mechanical (HM) numerical analysis simulating an in situ test involving an excavation in argillaceous rocks. The test has been performed in the Meuse/Haute Marne laboratory of Eastern France, sited in a thick stratum of Callovo-Oxfordian mudstone. A specially developed numerical formulation and constitutive model have been used. The results of the analyses concerning displacements, pore pressures, damage and permeability variations are compared with observations. A satisfactory reproduction of the most relevant behaviour is achieved.

When two spans of the Birmingham Bridge, a vital link in the Pittsburgh area transportation system, dropped up to 200 mm (8 in.) overnight, rapid response and a team approach was key to minimizing the impact to traffic and to the subsequent remediation. Initial inspection, initiated within hours of the discovery, revealed that the steel rocker bearings at Pier 10S had over-rotated and failed, causing the girders to drop onto the pier cap and resulting in damage to the pier itself. Repairing the bridge and reopening the roadway to traffic as soon as possible was critical. A closely-coordinated effort between PennDOT and all members of the quickly-assembled bridge retrofit team was instrumental in ensuring the immediate temporary stabilization of the structure to allow traffic flow to resume during the subsequent bridge rehabilitation. The cause of failure was determined to be the "ratcheting" of debris-choked and corroded rocker bearings at the top of the pier. However, this paper discusses the complete evaluation of the structure, conducted concurrent with emergency temporary shoring measures, including analysis of the original foundation system, and design, installation and testing of new micropile foundation systems that replaced the inadequate deep foundations at both Pier 10S and Pier 10N.

The piezocone penetration test (CPTU) provides near continuous measurements of three independent parameters: tip resistance (q_t), sleeve friction (f_s), and penetration pore pressure (u₂). The tip resistance and sleeve friction are roughly analogous to pile end bearing resistance (q_b) and the shaft resistance (τ_f) near the pile tip during installation, respectively, while the penetration pore pressure provides an indication of the drainage conditions during cone penetration. However, due to the differences in diameter between a pile and a CPT, as well as the differences in installation method, CPTU parameters (q_t and f_s) must be modified to assess the values of unit base and shaft resistance (q_b and τ_f) applicable to the static capacity of the pile and the soil resistance to driving (SRD). In this paper, back-analyses of installation records from eight large diameter (1.2 to 1.8m) open ended pipe piles driven through soft clays, silts, and sands at the Tokyo Port Bay Bridge site are conducted using the results of adjacent CPTUs. These analyses provide guidance on evolving methods for interpreting CPTU data to provide predictions of short term SRD, in addition to long term static capacity.

The Soil-Structure Interaction (SSI) facility at Lafayette College, which was funded by the National Science Foundation, was recently used to investigate the soil-pile interaction for laterally loaded piles with the main focus on the interaction pressure between the pile and surrounding soil. A precast concrete pile, that was 101.6 mm in diameter and 1.17 m long, was reinforced with one No. 4 rebar (diameter = 12.7 mm) located at the center of the pile cross-section. The pile was instrumented with strain gauges along the length of the pile, displacement and tilt gauges at the point of loading, displacement sensors along the length of the pile, and thin pressure sensors wrapped around the pile. The soil, which was rained around the pile, was classified as well-graded sand. This paper focuses on measuring the soil-pile interaction pressure for a laterally loaded pile. The paper also describes the installation procedure, the soil properties, the measured pile force-displacement relationship and the measured strain along the length of the pile. Measured interaction pressures present the first step to develop the soil force-displacement relationship (i.e., the soil reaction or the p-y curve) based on direct measurements. The experiment described in this paper presents the initial effort of the research team, which will be followed by further experimental work focusing on the behavior of laterally loaded piles in soft soils.

In general, a drilled shaft embedded in weathered rock has a large load bearing capacity. Therefore, most of the load tests are performed only up to the load level that confirms the design load capacity of the pile, and stopped much before the ultimate load of the pile is reached. If a reliable ultimate load value can be extracted from the non-failed load test data, it will be possible to greatly improve the economical and design efficiencies of a pile. The main purpose of this study is to propose a method for judging the reliability of the ultimate loads of piles obtained from extrapolated load test data. To this aim, ten static load test data were obtained from testing of piles to their failures from three different field sites. For each load-displacement curve, loading was assumed to be known, as being 25%, 50%, 60%, 70%, 80%, and 90% of the actual pile bearing capacity. The limited known data were then extrapolated using the hyperbolic function, and the ultimate capacity of a pile was re-determined by the Davisson method (1972). Statistical analysis of the reliability of the re-evaluated ultimate loads was carried out. The results showed that if the ratio of the maximum-available displacement to the predicted displacement at the extrapolated ultimate load exceeded 0.6, the ultimate load may be regarded as reliable, having less than a conservative 20% error on average. The applicability of the proposed method for reliability evaluation was also verified against static load test data of driven piles.

Model tests were conducted on vertically loaded single piles in sand subjected to either a uniform or a triangular profile of soil movement. Results of four tests are presented herein in the form of maximum bending moment (M_max), shear force, and pile deflection profiles. The evolution of the pile response with frame movements is examined, regarding the effects of soil movement depth and profiles, and axial load using the measured moment and deflection. In particular, the triangular profile causes 95∼160% higher `ultimate' M_max than the uniform movement does. The vertical load causes 5∼17% higher value of the M_max.

Augered cast-in-place (ACIP) piles and pressure-injected footings (PIF) are drilled foundations that can develop increased capacity and stiffness because of the construction processes used to build them. To evaluate these increases, load tests are used to evaluate the overall axial load-displacement behavior, which then can be generalized and compared with drilled shaft behavior. In this paper, the overall axial load-displacement behavior is examined using a database of 296 load tests developed for ACIP piles and PIFs. Issues of extrapolation of load test results and interpretation of the "failure load" are examined. Consistent procedures are suggested to extrapolate (where necessary) and interpret the data. A consistent correlation is found between the failure load interpreted by the slope tangent and L₁-L₂ methods. Results are compared with other drilled foundation types, and construction effects are discussed.

The wind energy sector is rapidly growing driven by the growing demand for sustainable energy. The past years have seen the wind industry develop and test not only more efficient, but also much larger wind turbines than those currently in use. These large wind turbines will place large demands on the support structures and foundations. As an increasing number of wind farms are being planned offshore in water depths of over 50 m, the combination of water depth, the increased windmill tower heights and rotor blade diameters will create loads that make foundation design very complex. Moreover, offshore foundations are exposed to additional loads such as from ocean currents, storm waves, ice and potential ship impact. All of these factors pose significant challenges in the design and construction of wind turbine foundations. This paper presents the various issues facing the designer in designing and constructing offshore wind turbine tower foundations. Current practices are examined and summarized to assist developers in foundation type selection and design.

This paper presents results and analyses of three full scale lateral load tests. The main objective of this study is to evaluate the influence of the pile bending stiffness in the resulting soil reactions acting around the laterally loaded pile. The case history involved three test piles installed at a well characterized sandy site and tested under similar conditions. The results presented in this paper show that the back-calculated soil reactions, at different depths and lateral deflections levels, yielded considerably different values on each test pile. This observation applied for both computational methods used which is revealing given the similar geotechnical conditions and installation procedures used for the three test piles. It is concluded that the differences in soil reactions are primarily related to the differences in flexural stiffness of the test piles (however, some variations are related to inherent soil variability within the test site). The influence of flexural stiffness in the soil reactions is explained reasonably well with the strain wedge model which allows including this important effect in the analyses. In summary, this paper presents a detailed full-scale case history hoping to shed some light on this potentially important factor of the pile flexural stiffness in the lateral soil reactions of laterally loaded piles.

The load test program for the Audubon Bridge project provides a comparison of the performance of base grouted and ungrouted shafts on large diameter foundations in sand. Comparison of several field load tests at the two pylon foundations indicate that the base grouting operations more than doubled the available base resistance, and provided for consistent load-deflection behavior in sand with varying properties. Base grouting of all the production shafts also provided a verification of axial resistance. The Audubon Bridge will be a new Mississippi River crossing near St. Francisville, Louisiana, and the two main pylons of the cable-stayed span are each supported by a 3 x 7 group of 2.29m (7.5ft) diameter drilled shafts. The drilled shafts bear in an alluvial sand and gravel formation at an elevation about 61m (200ft) below the surface. Underlying this formation was a clay with less potential base resistance for deep foundations.

Lateral load tests were performed on a full-scale pile cap in clay before and after construction of shallow soilcrete walls produced by soil mixing and jet grouting on either side of the pile cap. This relatively simple approach increased the lateral resistance of the pile cap by 60% for soil mixing and 160% for jet grouting. For the soil mixed wall, essentially all of the increased resistance was due to passive pressure and side/base shear against the soil mixed wall as the pile cap pushed the wall laterally. However, for the jet grout wall, about 25% of the increased resistance came from soil-pile interaction because the jet grout wall extended under the cap and against the piles. Soil mixing and jet grouting provide a means to significantly increase the lateral resistance of existing pile group foundations with relatively little investment of time, effort, and expense relative to adding more piles.

Based on the pile restrike data collected by the Louisiana Department of Transportation of Development (LADOTD) from the construction of phase 1B of the LA-1 relocation project, the Skov-Denvor (1988) pile setup prediction model has been implemented as a baseline by using the average unit skin friction and the normalized pile resistances. The pile resistance data were achieved from the CAPWAP analyses on restrikes of the piles from the North Connector segment. The research shows that for the soft clay soils at the LA-1 relocation project site a conservative setup parameter A of 0.2 may be used for predicting the shaft capacities. In addition, a growth-rate based capacity prediction model was developed. The rate-based model was compared with the Skov-Denver model, and it is found that the model gives better predictions. Furthermore, this rate-based model can be employed to estimate the ultimate pile resistance.

A fully coupled finite element computer code, TeraDysac, was used to study the influence of ground improvement around piles in a planned centrifuge model test. TeraDysac considers the coupled differential equations governing the behavior of the soil skeleton, pore water, and the piles. Bounding surface elastoplastic constitutive models are used to simulate the stress-strain behavior of soils in TeraDysac. The prototype of the centrifuge model consisted of 10 m of soft clay underlain by 8 m of dense sand. Four 0.36 m diameter single piles were simulated with various extents of CDSM around the piles. The simulations using TeraDysac involved base shaking of the entire deposit. Static lateral loading of slightly different piles using the computer code LPILE is presented in a companion paper (Sritharan and Huang, 2010). It was shown that CDSM around the piles is effective in reducing the lateral displacements of the piles during static and dynamic loading.

The majority of Florida Department of Transportation (FDOT) highway structures (e.g., bridges, signage, etc.) are founded on deep foundations, i.e., driven piles and drilled shafts. In the past, the most commonly used foundation type was driven piles. With increased urbanization, the noise and vibrations associated with pile driving has resulted in more drilled shaft usage due to its less intrusive characteristics. Unfortunately, due to horizontal soil stress relief during installation, drilled shafts suffer reduced axial and torsional resistance when compared to similar sized driven piles. Additionally, as-built drilled shaft integrity is generally more questionable than precast piles. To address these concerns, FDOT investigated post grouted drilled shaft tips, which not only increases the end bearing, but also proof tests every shaft. However, the issues of quality control (i.e., the structural integrity of the cast-in-place shaft) and the reduction in side friction due to horizontal stress relaxation still remained. Thus, the FDOT funded a research project to develop an innovative new deep foundation type which ensures both the quality control of a precast member with the lateral stress increase similar to a driven pile but with the minimum intrusion of a drilled shaft. It is referred to as a jet-grouted precast pile or jet-grout pile. The research was conducted in FDOT's new cylindrical 3.66 by 10.67 meter in-ground geotechnical test chamber, which is capable of monitoring soil stresses and deformations. The first trials involved jetting precast concrete piles with multiple sets of embedded grout delivery pipes. The early tests revealed higher horizontal versus vertical distribution of the compaction grout, as well as poor bonding between the grout and pile. Subsequently, the grout delivery system was re-designed; a new colloidal grout mix was developed along with the introduction of grout membranes on the outside of the pile. Small scale testing showed complete envelopment of the pile with excellent grout bond to the pile. Finally, a full scale (0.406m x 0.406m x 6 m) pile was jetted and subsequently grouted along its length in two stages with no tip grouting. The pile was then torque tested to 610 kN-m with 15° of rotation, resulting in a unit torsional side resistance of 77 kPa. Next, the tip of the pile was grouted and a top down compression test yielded 1,335 kN of resistance at 0.25 mm of vertical pile head movement that exceeded the resistance of a traditional similar size driven pile.

The lateral resistance of pile groups in soft clay is typically relatively low. Rather than drive additional piles, some have suggested that lateral resistance could be increased by replacing the top 5 to 10 pile diameters with compacted granular material. To evaluate this possibility, lateral load tests were first performed on a full-scale pile group in clay. The pile group consisted of 15 steel pipe piles with an outside diameter of 324 mm driven in a 3 x 5 arrangement. A second test was then performed after 0.9 m of clay was excavated and sand was added to produce a 2.4 m layer of compacted sand. This relatively simple approach increased the lateral resistance by about 30% or 450 kN at a displacement 70 mm. The cost effectiveness of this approach increases as the undrained shear strength of the clay decreases and the friction angle of the compacted sand increases.

The footprint and topography of New York City has changed dramatically over the last three centuries. The shorelines, particularly of the Manhattan Island, have expanded well beyond their original locations into the adjacent rivers and bays. As the city continues to expand, marginal filled-in land with difficult subsurface conditions is being developed. This paper discusses some of the design challenges and associated engineering analyses performed for a large waterfront development project that includes seventeen high-rise residential towers and a large multi-level riverfront park. An emphasis is placed on the numerical evaluations that were performed during design. The project area is a former railroad yard with hydraulic fill placed over compressible river bottom deposits. The presence of loose fills and compressible deposits presented numerous design challenges. The development required raising existing grades by placing over 10 meters (32 feet) of new fill to extend the existing street grid onto the site and to create the new park space. Measures had to be taken to limit the settlement induced by the new fill and to reduce the impact of the development on adjacent structures, including an elevated highway along one side and active passenger railroad tracks at grade along the other side of the project site. Those measures included construction of pile-supported relieving platforms, improvement of compressible soils by pre-loading with surcharge fill, and use of lightweight fill. Extensive engineering evaluations, including both analytical and numerical analyses have been performed to provide efficient designs.

Following the Winkler analysis concept, a simplified analysis method is investigated in this paper to characterize the lateral load behavior of piles in unimproved and improved soft clays. Several different ground improvement scenarios were used with cement deep soil mixing as the soil improvement technique and the extent of soil improvement region as the main variable. By using the proposed analysis method, modified p-y curves can be developed to model the nonlinear behavior of improved soft clay surrounded by unimproved soil as a homogenized composite material. This modified p-y curve was incorporated into LPILE analysis program to characterize the monotonic pseudo-static load response of a single pile subjected to lateral load in different ground improvement scenarios. Although the analysis results require validation based on test data and/or detailed 3-D analysis results, which are being currently performed in an ongoing study, the investigated method enabled the effects of soil improvement to be accounted for in a simplified manner.

Improving static and seismic foundation performance through vibro-replacement is a valuable alternative to traditional shallow and deep foundation options. However, appropriate design methods and field quality control (QC) measures are essential to implement a successful vibro-replacement program. Field QC, including comparison of pre-construction and post-construction soil exploration results (for seismic mitigation) and representative-scale performance testing of footings supported on stone columns provide valuable information about the effectiveness of the ground improvement program. This paper describes design, construction, and field verification testing of a vibro-replacement ground improvement program conducted to improve static and seismic performance of a shallow foundation system for a large structure in New Jersey. The field verification program, described herein, included a comparison of pre-construction and post-construction cone penetration testing and a full-scale footing performance test.

A generalized model is presented for a subgrade idealized as an elastic layer overlying a rigid base. In contrast to previous works no stresses, strains or displacements are neglected a priori. A second-order partial differential equation is obtained similar to Kerr's mechanical model. It is demonstrated that several variants of the model can be obtained by specifying two relations: a function for the horizontal-to-vertical stress ratio and another for the variation of the vertical shear stresses with depth. Two such variants are presented. Also, lower-order models are obtained by making just the necessary assumptions. Accordingly, models of the order of two-parameter mechanical models are obtained when the horizontal deformations alone are neglected; Winkler-type models result only when the vertical shear stresses are omitted. Two variants of each of these lower-order models are provided. The proposed models have applications in the analysis of beams and plates on elastic foundations. Such an application together with a calibration work is demonstrated on beams in the companion paper (Part II).

Variants of a new continuum subgrade model presented by the first author (Part I) are employed to analyze beams on elastic foundations. When the higher order model variants are used, the beam's differential equation becomes of order six. Closed-form solutions of finite and infinite beams are obtained for basic loadings. Deflections are compared with results of finite-element based software and a classical model. Though the comparison shows that the new model is sensitive to the subgrade thickness, a carefully conducted calibration work eliminated this drawback. Numerical examples illustrate that the calibrated variants give results in excellent agreement with the FE results. Also, the influence of the subgrade shear becomes less significant once the calibration is accomplished. This outcome suggests that the classical Winkler model can still be used together with the improved relation for the coefficient of subgrade reaction provided at the end of the paper.

One potential way to prevent overturning of an eccentrically loaded footing and increase its efficiency is to hold the heel of the footing down into the ground with a structural member such as a cable. This study involved the finite difference numerical modeling of square concrete reinforced footings, on a homogenous mass of soil, restrained at the tension side with steel cables. The numerical models concentrated on the elastic behavior of soil. From the output of the numerical model, the bearing stress underneath the footing and the tension force in the steel cable were analyzed. A similarity between the model stresses and the stresses in an elastic and cracked concrete beam was observed. In this study, a simplified method, using a transformed area of the cables and assuming a linear strain, was proposed and was compared with the numerical method in terms of the bearing stress and the cable force.

Geocells consist of a series of interconnected single cells made from different materials. The cell walls completely encase the infill material and provide an all-around confinement to the soil. During vertical loading hoop stresses within the cell walls and earth resistance in the adjacent cells are mobilized which increase the stiffness of the soil. As a result the applied vertical load is transferred over a larger area and the settlements and the vertical stresses on the subgrade are reduced. Settlement and vertical stress measurements in asphalt road constructions have shown that the geocells reduce the settlements and the vertical stresses on the subgrade about 30 percent. Placement of geocell reinforced soil layer over vertical columns has shown that the geocells transferred the loads to the vertical columns and reduced the vertical stresses on the soft subgrade. Details and results of model tests and in-situ field tests are presented in the paper.

Expansive soils pose a major maintenance nightmare for geotechnical practicing engineers in the semi-arid and arid zones of the world. The introduction of rigid substructure is a costly approach but can be made practical and financially tolerable for soils where expansion is characterized within medium to low problematic classes. This paper outlines justifications and design concepts for a rigid substructure foundation of a two story concrete frame structure. The project was constructed in a district in Saudi Arabia where many buildings experienced serious damage due to expansive soil problems. Upheaval forces likely to act against the proposed structure were determined and used in the finite element analysis and design of an appropriate rigid substructure design. Plots of moments and forces were determined and critical sections were pointed out. Methods and stages of construction were monitored and a baseline vertical movement was established for future verifications. The advantages and limitations of this system are also discussed.

Dublin, Ireland is scheduled to constructing its first metro in 2010, with a pair of tunnels connecting the city center to the airport. This study presents first-order predictions of the anticipated soil settlement and related building damage for a single structure on the route. The structure is a 19th century, stone church on glacial till situated almost directly above the shallowest portion of one of the tunnel crowns and immediately adjacent to a station box. To assess potential damage, a settlement trough is predicted based on another recent Dublin tunnel and the anticipated settlement is applied to the church. Damage predictions based on these freefield predictions are made and then revised as to the anticipated impact of the structure itself based on building stiffness, which significantly reduces the maximum differential settlement from 63mm to 36mm resulting in minimal predicted damage.

Settlement under seismic loading in dry sand is perplexing to predict due to the lack of authentic technique analysis. A laminar soil box (10 ft x 10 ft x 6 ft) of alternating layers of aluminum and rubber was designed and constructed at the University of Nevada, Reno. The laminar box was placed on a biaxial, multiple shake table and tested with different input motions including a series of simple sine waves and the El Centro earthquake motions scaled up to 1.0 g. Approximately 26.5 tons of Ione utility sand was deposited in the soil box under a loose to median dense condition and a square foundation (2 ft x 2 ft x 3 ft) with an attached light structure of three lumped masses was embedded in the middle of soil box. A series of test data including acceleration of different depths in the soil, on the soil box, the foundation and at levels on the structure; settlement measurements of the foundation and at the free-field soil surface; deformation and strain along the soil box boundary and relative density of dry sand for different input motions were achieved. Such collected data was used to assess the settlement and soil-structure interaction under seismic loading of dry sand. The test results present particular patterns of settlement at different sand density states under simple motion (sine wave) and earthquake acceleration (El Centro) with multiple magnitudes. The density of the sand is a dominant factor with respect to settlement throughout the series of tests.

The use of significantly different methods for estimating settlements of footings in sands and clays, under working loads, poses a problem when intermediate soils are encountered. In this paper we propose a method of analysis based on equivalent-linear elasticity that applies to all soil types, and is simple to apply. We also propose methods to determine and/or estimate the needed soil properties. We report here on a field test of a full scale footing in silty sand and sandy silt, in which measured settlement is compared with settlement predicted using the theory and soil properties determined in the field from seismic tests and in the laboratory from dynamic tests. We also compare measured settlements with values calculated with several widely used methods and make appropriate recommendations.

The rigid inclusions technique is based on the use of a network of piles covered by a load transfer granular layer which allows the construction of roads, railways and buildings on very poor subsoil. Today, there are no relevant design methods able to predict the behavior of such structures due to the lack of knowledge about the load transfer mechanisms in the granular layer. Consequently, experimental works and numerical studies based on the Discrete Element Method were carried out. Both experimental and numerical results show that the granular layer can reduce greatly the surface settlement and the load applied to the soft soil. The numerical analysis shows that the load transfer mechanisms take place in a specific area located over the piles and is highly influenced by the rigidity of the soft soil. Thanks to the good agreement obtained with the numerical analysis, a prediction of the load transfer amplitude close to the description of Carlsson was proposed.

Soil unloading and rebounding induced by large-scale deep excavation may affect the performance and integrity of existing piles inside the excavation zone. In this paper, nonlinear finite element technique is employed to investigate the behavior of uplift piles in Shanghai Expo Underground Substation Project during deep excavation. Parameters of subsoils are obtained by back analysis of the actual load test results of the uplift piles. The behavior of the uplift piles during excavation and under normal working load conditions are analyzed by FEM modeling. The numerical studies suggest that tension developed during excavation should be included in the analysis and design of pile foundations. The results reveal that the belled uplift piles may be subjected to much larger tension during excavation than those straight uplift piles.

A three-dimensional finite-element analysis was performed to analyze the interaction between pile and ground due to tunnel excavation in Guangzhou No. 2/8 extension Subway project. The 3D FE mesh includes 50 original piles and 80 underpinned piles surrounding the tunnel excavation. Three different tunneling scenarios were simulated, from which the ground settlement curves as affected by the surrounding pile groups were studied. The FE analysis further demonstrates that simultaneous two tunnels excavation (keeping abreast) is the worst scenario for the ground settlement and for the consequent effects on the superstructure. The separate 2-D FEM analysis shows that the piles can easily be subjected to negative skin friction and excessive bending during the shield tunnel excavation going through the piles. These additional bending and negative skin friction should be carefully considered during design and construction stages.

Shear strength of soil-structure interface is very important while designing structures pertinent to geotechnical engineering that include but not limited to design of shallow foundation, pile, retaining wall, and sheet pile. Although the interface shear strength is very important, designers use empirical values while designing such structures. There are numerous literatures available regarding the numerically simulated values of interface shear strength. However, very few researches have been done lately on the interface resistance of different types of soil and structure. Different soil specimens were tested in a multiple-reversal direct shear device to measure the shearing resistance of soil-concrete, soil-wood, and soil-steel interface. The types of soil included in the research were SP, SW, SM, SP-SM, MH, ML, and CL, based on the USCS system. The result shows that skin resistance of soil-structure interface depends on the surface material of the structure and the type of soil. The behavior of dry soil differs from that of saturated soil.

With the increasing use of auger pressure grouted (APG) piles in new construction, it is important that proper design parameters be incorporated when evaluating pile capacity and performance using reliability-based design methods. This paper focuses upon developing t-z model parameters and their variability from analysis of static axial compression tests on APG piles. Data from ten static pile load tests conducted on APG piles from construction sites and literature were obtained. Load-settlement curve fittings between the measured data and the theoretical data were conducted using the t-z method to back-calculate a set of soil-pile interfacial and tip parameters. The t-z model parameters are compared to standard field investigation data, including standard penetration test (SPT), cone penetration test (CPT) and effective stress of the ground to develop correlations suitable for the design of APG piles. Subsequently, the t-z model for APG pile design was developed and the model efficiency was evaluated by comparing the predicted and measured load-settlement and load transfer curves.

This paper introduces a simple chart method for laterally loaded short piles in cohesionless soils to account for the effect of "finite slope", which has a low slope height to pile diameter ratio. In the development of the simple chart method, p-y curves within the slope height are modified and manually input into the computer program, LPILE. Soils below the slope are modeled with the internally generated p-y curves for level ground. Separate LPILE runs using the steps above are conducted for various slope geometry, soil properties, pile properties, and structural loads. The results are plotted with normalized axes for various slope angles in a simple design chart. Results indicate that at a slope height (H) to pile diameter (D) ratio of 5 or greater, the pile behave similar to an infinite slope. For a H/D lower than 5, the designers may be able to use shorter pile lengths associated with the "finite slope". In addition, the authors conducted comparison analysis with a finite element model based on lateral load tests performed on level ground. Comparison results indicate that the predictions with modified p-y curves are conservative.

Geotextile tubes are being increasingly used in environmental applications for dewatering and containing slurry waste and contaminated sediments. An important design consideration from the geotechnical aspect is the stability of geotextile tubes when they are stacked in multiple layers. The paper presents a stability model that was developed to simulate stacked geotextile tubes using typical limit equilibrium slope stability analysis methods. The model takes into account the shear strength of slurry waste at different stages of dewatering, the high tensile strength of geotextiles, and the interface shear strength of the geotextile tubes and the liner system. Using the model, potential sliding of geotextile tubes along weak interfaces and potential global failure involving the foundation can be evaluated. The application of the model is demonstrated by an example engineering scenario. Based on the model results, a sample design chart that provides minimum interface strength values for the geotextile tubes and liner system is also presented.

Site characterization for a proposed 30± m (98 ft) cut slope indicated slickensided discontinuities in claystone rock cores, laterally discontinuous strata, and erratic topography that suggested the possible occurrence of pre-existing deep bedding plane shear surface(s). An instrumentation program was developed that consisted of inclinometers and piezometers to monitor slope movement and water levels during construction. The inclinometer data indicated movement along distinct shear planes which generally ceased upon completion of blasting and excavation operations. Approximately 8-months after construction, a 6,200± m³ (8,000 yd³) slide occurred in the overlying stiff clay with no apparent indication of prior inclinometer movement. A finite element model was developed to analyze the failed stiff clay slope and help understand the influence of horizontal stresses and how they increase the probability of progressive failure in heavily overconsolidated clay and shale slopes. These slopes tend to fail by a progressive mechanism as the soil in various portions of the slip surface is successively strained beyond the peak. The model predicts the development of a shear plane along the clay and claystone interface, as identified by the inclinometers in the actual slope, although the magnitude of movement is different. Stress concentrations exist at the tips of fissures and cause propagation that is inclined to the direction of the shear band. Fracture mechanics concepts can be used to study progressive failure of these fissures in stiff clay slopes.

Construction of a large sewer in Louisville, Kentucky required five tunnels under two railroad lines, a roadway, several high-pressure gas transmission pipelines, and a creek. The 4.3-m tunnels were to be built 8.2-13 m below grade in alluvium and lacustrine deposits. The 8-10-m-thick alluvium consisted primarily of sensitive silt and silty clay layers, whereas the lacustrine soils were silty clays of moderate plasticity. During hand mining of the liner-plate tunnels, the headings squeezed and the contractor resorted to poling, ground freezing and, finally, a tunnel boring machine. Three tunnels were completed before the contractor filed a claim of "changed conditions." A tunneling expert hired by the contractor inspected one of the tunnels and asked for samples from new borings. The 75-mm Shelby tube samples obtained at the site were shipped 400 km to the expert's laboratories, then were extruded and tested by graduate students. The expert reviewed the test results and said that the undrained shear strengths, as low as 9.6 kPa, were inadequate for hand mining, and much lower than strengths indicated in pre-construction documents. The expert noted contortions in thin bands of silt and clay, adjacent to uncontorted layers, and concluded that natural processes had caused the contortions, and low strengths. The authors were retained by the tunnel owner to investigate the claims of changed conditions and "naturally" caused contortions. Knowing the sensitive nature of the soils at the construction site, the authors worked with an expert driller to obtain best-quality 75-mm Shelby tube samples. These samples were extruded carefully and tested by the authors in their nearby laboratory. The measured strengths were equal to or higher than those reported in pre-construction documents. The source of the contortions also was discovered. Records of adjacent tunneling operations by another contractor also were used to explain the cause of the distress.

To simulate the field conditions of a partial-cut and partial-fill embankment, the 3D non-linear finite difference model (FLAC3D) was utilized in this study. FLAC3D is able to visualize and characterize the deformation characteristics and stress distributions. The material parameters were determined from the laboratory tests and knowledge of the site conditions. The analysis results demonstrated that one of the main contributing factors for the settlement is the backfilling thickness as the settlement tended to increase with the backfilling thickness. Also, the maximum differential settlements existed in a small region (about 1.5 meter wide) at the junction of partial-cut and partial-fill embankment. Field evaluations on many expressways have also confirmed that surface cracks often occur in this small region. Transportation authorities can benefit from this study by formulating initiatives to develop cost effective design and construction methods that minimizes cracking, with a focus on the ∼1.5 meter wide region.

This paper presents portions of a five-part study done to further investigate the behavior of a deep braced excavation and improve upon existing techniques for estimating the magnitude of the transitory forces in such structures. This year-long project, constructed in San Francisco Bay Mud, was completely instrumented and monitored throughout the construction process. This initial part of the research provided the measured geotechnical and structural data with which to compute and compare load predictions made at various stages of construction. The second part of the study consisted of the development of a three-dimensional finite element structural model to allow for the application and study of various earth pressure theories proposed in the literature as well as a new earth pressure hypothesis developed and presented for this project. Comparisons were calculated and tabulated in the third and fourth parts of the study which included the evaluation of the relative performance of each model in predicting structural loads. Conclusions and recommendations were presented within the fifth part. With respect to the five earth pressure models selected for comparison, those with triangular shapes performed slightly better in the prediction of structural loads than did those with trapezoidal configurations. For the new model proposed and developed, the use of the Tributary Area Method along with earth pressures from K_o effective stress plus best-estimate pore pressures without reshaping of the newly suggested earth pressure diagram is recommended. Bending stresses within specific strut members were found to be surprisingly high with measured values averaging approximately 85% of P/A stresses. Augmentation of the predicted compressive stresses by 150% is recommended until further studies are completed. The finite-element structural model developed was a valuable research tool but incredibly labor intensive. Continued use of the Tributary Area Method is recommended for routine design of braced excavations.

A design method for using the drilled shafts to stabilize an unstable slope is presented in this paper. The method is based on the concept that the presence of drilled shafts in a slope reduces the driving forces on the down slope side of the drilled shafts due to the soil arching by which the earth pressure was transferred to the drilled shafts. The presented design procedure allows for optimization of the drilled shafts size, shaft location, shaft fixity (the necessary rock-socket length), and the spacing between the drilled shafts for a given unstable slope with known slip surface to achieve the desired target FS of the slope/drilled shafts system.

In this study, a failed slope near Ohio River was used as a site for installing a row of three drilled shafts and an isolated single drilled shaft and for subsequent surcharge loading with a purpose to investigate the slope-drilled shaft interaction due to surcharge load induced slope movement. The drilled shafts and the slope were instrumented with strain gages and inclinometer casings so that drilled shaft behavior can be related to the slope movement due to the applied surcharge load at the top of the slope. The field measured data revealed that there was a difference in structural response between the middle drilled shaft in a row of three shafts and an isolated single drilled shaft when the surcharge load was applied. The difference was attributed to the arching effect. Furthermore, the arching effect was manifested in the small movement of the soil particles between the drilled shafts.

Extensive riverbank failure at a large industrial facility in central Alabama in 1991 endangered large tanks and air pollution control facilities, and a barge dock near the downstream end of the site. In the early 1970s, Leo Casagrande had investigated conditions at the barge dock. Porewater pressures in nearly vertical joints in underlying chalk apparently caused those failures. To remedy the situation, a graded filter under riprap was constructed to protect the bank but allow water to drain. Several years later, Casagrande investigated problems around the pumphouse at the upstream end of the site. High water pressure in basal sand, covered by a clay drape, was the culprit, according to Casagrande, but no action was taken. Continuing instability in 1990 prompted installation of a geosythetic filter unders sand and riprap, near the pumphouse. Despite the remedial work, recession of very high water in the following June caused a catastrophic failure. Was Casagrande wrong in his diagnosis?

Large diameter monopile foundations for offshore wind turbines are subject to large horizontal loads and overturning moments. These foundations have diameters ranging from four to seven meters with the potential to become larger with the development of larger wind turbines. They are often analyzed by means of the p-y method to characterize the pile-soil interaction. While the method is theoretically rigorous, the input p-y curves, for example those recommended by the American Petroleum Institute (API), are based upon very limited field data. This paper describes some analyses of a large diameter monopile in dense sand. The pile characteristics are representative of the foundations for a 3 to 5 MW wind turbine. The soil characteristics are representative of dense sandy soils that may be encountered at wind farm sites in the southern North Sea and offshore the Northeast United States. The pile was modeled by the p-y method and also by 3D finite element analysis (FEA). The paper describes the details of the FEA model development, important in minimizing numerical inaccuracies in 3D analyses. Equivalent p-y curves, back-calculated from the 3D FEA, may be useful for p-y analyses, which are simpler than 3D FEA. The results suggest that the API method over predicts soil resistance and under predicts pile deflection for large diameter monopiles subjected to lateral load and in stiff soils.

Bridge approach settlement is a common problem to the Transportation Departments nationwide. This uneven transition causes inconvenience to passengers and increases the cost of maintenance and repair of the distressed approach slabs. The Texas Department of Transportation spends millions of dollars annually to mitigate this problem across the state. The potential causes for this problem are numerous and purely site specific. Hence this problem may not have a unique solution. In an on-going research project, deep soil mixing (DSM) columns were utilized to stabilize soft subgrades and alleviate the bridge approach settlements. As a part of the assessment of DSM improvements, both embankment and foundation soils are extensively instrumented with inclinometers and extensometers to monitor for both lateral movements and settlements at different depths. Data collected from the instrumentation and a few laboratory experiments on the treated soil mixture were used to address the DSM treatment in stabilizing soft soils.

In this paper, excavation induced slope movement on the performance of drilled shafts of an office building in Taipei city is studied. Excavation is planned at four stages after a row of drilled shafts were installed before excavation. Severe slope movement occurred and extended outside the project area during excavation due to weak clay layer overlying bedrock and unpredicted local trough between soil/rock interface. Performance of drilled shafts is evaluated and compared via measured inclinometer data and available computer code PLAXIS.

This paper presents a Bayesian probabilistic framework to assess soil properties and model uncertainty to better predict excavation-induced deformations using field deformation data. The potential correlations between deformations at different depths are accounted for in the likelihood function needed in the Bayesian approach. The proposed approach also accounts for inclinometer measurement errors. The posterior statistics of the unknown soil properties and the model parameters are computed using the Delayed Rejection (DR) method and the Adaptive Metropolis (AM) method. As an application, the proposed framework is used to assess the unknown soil properties of multiple soil layers using deformation data at different locations and for incremental excavation stages. The developed approach can be used for the design of optimal revisions for supported excavation systems.

A major consideration in the design of excavation-related underground structures is the prediction of the movements associated with the construction operations. Excessive movements can lead to failure of the geotechnical structure or adjacent facilities. Most analytical methods currently used to estimate these deformations are deterministic, and ignore the many associated uncertainties such as the variability of the loadings and the variability of the geotechnical properties. A risk-based approach to performance failure is necessary to incorporate systematically the uncertainties associated with the various design parameters. This paper summarizes the procedure to assess the reliability of displacements associated with excavation-related construction activities such as tunnels and braced excavation systems using the first-order reliability method. Examples are presented to illustrate feasibility of the proposed method. With this method, it is possible to carry out sensitivity studies to examine the effect of the level of uncertainty of each parameter on the probability that the displacement-related limit state has been exceeded.

This study addresses the complexity of slope reliability problems based on limit equilibrium methods (LEM). The main focus is on the existence of multiple failure modes that poses difficulty to many LEM-based slope reliability methods. In particular, when weak seams are present, the failure modes associated with those seams may be difficult to detect. A systematic way of searching the failure modes is proposed, and its robustness over slopes with weak seams is demonstrated. It is found that in the presence of weak seams, assuming circular slip surfaces may cause underestimation of slope failure probability.

Spatial variability of soil undrained shear strength is usually not rigorously considered in the design of basal heave for deep excavations. In this study, the slip circle method is employed to investigate how the required safety factor against basal heave was affected by spatial variability in the context of reliability-based design. The non-stationary random field model is adopted to model spatial variability of undrained shear strength. Results show that the required safety factor obtained with the consideration of spatial variability is much smaller than that without the consideration. Parametric studies show that the vertical scale of fluctuation has a significant influence on the required safety factor: the longer the scale of fluctuation, the larger the required safety factor. For target failure probabilities of 0.01 and 0.001, the corresponding required safety factors are in the ranges of 1.4–1.9 and 1.6–2.5, respectively, for the average value of vertical scale of fluctuation of 2.5 m.

This paper presents an example of multiple uses of reliability methods employed by the project management team during the design and construction of the expansion of the Cherry Island Landfill, Delaware. The landfill expansion involves the installation of prefabricated vertical drains (PVDs) and the construction of a mechanically stabilized earth (MSE) berm over very soft river sediments and dredged materials. The critical nature of this structure and foundation required a high degree of reliability for the characterization of the key engineering parameters on which the design was based. This paper presents the use of reliability methods for the following purposes: (i) to develop geotechnical characterization of the soil parameters; (ii) to perform stability analyses during the design phase; and (iii) to more effectively communicate design scenarios and their associated risks and costs to all project stakeholders during the design process. The use of reliability methods, beginning at the onset of the project led to a better-informed site exploration, a highly-detailed geotechnical characterization, a design with a high degree of reliability, and better- informed stakeholders during the design and permitting of the expansion.

San Francisco, Athens, Boston, and Singapore are among the major coastal cities of the world whose wastewater systems, including marine outfalls, are located in very challenging natural and anthropogenic environments. Assessment of regional geotechnical conditions early in the site selection and overall design process substantially reduced costs by identifying factors that might require extensive variations from anticipated designs. Knowledge of the potential hazards and risks resulted in realistic geotechnical and oceanographic investigative programs, analyses, designs, and cost estimates. Geohazards and other factors important to the design and construction of these coastal wastewater systems are discussed herein.

There are many ways to approach risk modeling for geotechnical applications, some highly refined, some fairly simple; some highly mathematical, and some relying mostly on expert judgment. What one best uses depends on the problem at hand, the adequacy of the data and assumptions, and the time and budget available. The paper draws on three examples of appropriate levels of analysis from projects that the authors have recently been involved with: (1) the question of screening for levee safety in flood hazard damage reduction inventories, (2) mine waste safety studies, and (3) the IPET risk studies in New Orleans.

Reliability tools have been applied to slope stability analysis more than any other geotechnical application on account of the readily understood concept of "probability of failure" as an alternative or complement to the traditional "factor of safety". Probabilistic slope stability methods in the literature are reviewed. Particular attention is focused on the ability of the methods to correctly model spatially varying soil properties. A benchmark slope is reanalyzed and conclusions reached about their suitability for meaningful and conservative prediction of slope reliability.

The evaluation or design of levees is often based on very sparse data. Explorations typically consist of borings spaced at about 1,000-foot centers along a levee alignment. The levee system may be divided into reaches where important factors such as height of the levee, type of levee foundation soils, and/or type of soil used for levee construction are similar. The engineer may determine which boring within each reach exhibits the most adverse foundation or levee soil conditions with respect to levee design criteria. This information is then used as the basis of an analysis of the entire reach under the assumption that the most adverse condition encountered among the borings is representative of the most adverse conditions in the entire reach. However, the most adverse conditions in the entire levee reach may not have been encountered by widely spaced borings. A method is presented to evaluate this risk when an adequate amount of geotechnical data is available.

Load tests are often carried out to verify design assumptions and to reduce the design factor of safety (FOS). In this paper, a method based on Bayesian preposterior analysis is suggested to evaluate the expected design FOS when a load test program is planned but not yet implemented. Two algorithms, i.e., Monte Carlo simulation (MCS) and a mean first order method (MFOM) are employed to calculate the expected design FOS. The accuracy of Monte Carlo simulation can be sufficiently accurate when enough samples are drawn. MFOM slightly underestimates the expected design FOS and it becomes more accurate as the number of piles in a test program increases. Results in this study reveal that the inherent variability within a site controls the amount of uncertainty that can be reduced by pile load tests, and that a few tests are often sufficient to remove the majority of uncertainty caused by cross-site variability. If a given number of piles are to be tested, the expected design FOS increases almost linearly with the target reliability index.

The interface shear strength characteristics of soil-geomembrane are usually obtained by using large direct shear test device in a laboratory. The repeatability of these tests is very important as the design relies on the properties obtained from the test results. This paper investigates the variability of large direct shear test results by performing series of tests on smooth high-density polyethylene geomembrane samples. For the tests performed in this study, the test results show a scatter ranging from 5 to 65 percent depending on the parameter investigated. This magnitude of variability in the test results is significant and should be considered in the design. This paper presents the test results and a statistical analysis of repeatability of large shear tests used to obtain soil-geomembrane interface shear strength characteristics.

Risk assessment and risk management of large projects are essential for the quality and safety of civil engineering. A dynamic risk management system for large construction projects in China is proposed. The dynamic risk management system is composed of six main parts, which are event database, risk database, risk identification, risk assessment, risk pre-control, and risk tracking. The results of risk assessment can promote reasonable decision-making for risk tracking. The risk tracking is an essential part of risk management, which contains a process of site risk exploration, risk re-identification, risk treatment and formation of risk tracking report. By using the risk management system in large project construction, the key risk events we caring about are monitored and new risk events may be found. Then the new risk event will be assessed and the decision will be made whether monitoring or not. Through the dynamic risk management system, we can clearly know the real-time statement and developing trend of every risk events, and then can take some precaution and control measures to treat the risk events for the purpose of preventing the occurrence of risk events or reducing the risk to an acceptable level.

The great Wenchuan Earthquake of May 12, 2008 formed more than 100 quake lakes with considerable risks. These Quake lakes are mostly distributed on the mountainous rivers in the worst-hit areas. Some are densely distributed in a segment of river channels; others in remote areas. 90% of the Quake lakes have gone through emergency treatment process or have self-burst, and have weathered through the flood seasons in 2008 and 2009. However, their long-term stability and safety need to be thoroughly evaluated, and some may require proper retrofit to ensure their long-term stability. Retrofit techniques will depend upon the risks imposed to the downstream area, geological conditions, landforms, hydrology, and the size and composition of the landslide dam. By using cases selected from Quake lakes formed by Wenchuan Earthquake, this paper discusses techniques for improved safety assessment of Quake lakes.

Over the past 30 years, the Geotechnical Baseline Report (GBR) has evolved as a contractual tool to manage subsurface risk for tunneling and other underground excavation projects. At this time, GBRs are beginning to be considered for major foundation construction contracts, for similar purposes of better management and allocation of risks. To successfully apply GBRs to non-underground projects, it is important to make effective use of the lessons learned from their application in underground construction practice, and to recognize the significant respects in which evolving practice for non-underground contract applications may differ. This paper includes a brief background discussion on the development of GBRs; outlines the transfer of underground-GBR principles to non-underground projects; highlights key differences; notes conditions that may be conducive to the use of a GBR; provides suggested guidelines for the application of GBRs to non-underground projects; and illustrates the application of these principles to the development of a GBR for a design-build elevated guideway rail project.

Rainfall infiltration affects the stability of dam slopes significantly. This paper studies the changes in the instability probability and the factor of safety of earth dam slopes during rainfall with different patterns. The influences of the maximum intensity, duration and total precipitation of the rainfall on the instability probability and the factor of safety are investigated. The results show that the instability probability of the dam slope increases at first and reaches a maximum value after some time then decreases with time. Generally, the instability probability increases with the increase in the maximum intensity, the duration and the total precipitation of the rainfall. These analyses provide some references for the dam safety evaluation considering rainfall infiltration.

This paper presents a case study of the failure of an excavation shoring (bracing) system with a sloping backfill. The initial stages of the failure were detected by a continuous automated monitoring system. Early detection allowed remedial measures to be implemented to minimize the effects of the failure and restore stability to the slope. An evaluation of the site conditions after the failure concludes that the failure mechanism was related to slickensides present within the weathered rock and rock matrix. Prior to the failure, the slickensides were undetected by previous design geotechnical studies completed by the project geotechnical engineer or preliminary observations of the excavation. Geotechnical and construction conditions that led to the failure are examined as well as an analysis of the failure using reliability methods. The results of the analysis considering the presence of slickensides are compared with the results of the analysis with the absence of slickensides. This enabled the authors to estimate the probability of failure in either case and make a comparison as to the likely cause.

The long-term functionality of composite landfill final cover systems and composite floor liner systems depends on the distortions imposed on these systems by differential settlement. The evaluation of differential settlement is particularly challenging for final cover systems, because of the heterogeneity of waste, and for floor liners over highly variable subgrades (e.g. existing waste, mine spoil, etc.). The present ability to forecast these distortions is limited by a scarcity of long-term settlement measurements at modern landfills and difficulty characterizing waste and subgrade properties. Furthermore, deterministic approaches to landfill settlement prediction are not able to capture the spatial variability in the waste mass and subgrade properties which control this behavior. This paper considers a probabilistic approach to the long-term estimates of differential settlement beneath landfill final cover and floor liner systems using random fields to model the waste and subgrade properties. Finite element analysis of two dimensional random fields is used to calibrate appropriate spatial correlation parameters for use in simpler, one-dimensional analyses to estimate differential settlement.

This paper presents a method to consider the spatial variability of the soil shear strength parameters for determining the critical collapse pressure of a pressurized tunnel face. Only the case of a cohesionless soil is considered in the analysis. The present method is based on the kinematic theorem of limit analysis. A new 2D kinematically admissible collapse mechanism whose shape depends on the spatial distribution of the soil friction angle (φ) is proposed. In this mechanism, the normality condition imposed by limit analysis is enforced everywhere along the slip surfaces of the failure mechanism. The results obtained using the present approach are presented and compared to those based on common numerical methods such as the Finite Element Method (FEM) or the Finite Difference Method (FDM). The proposed method is computationally more efficient and has significant potential for simulation studies involving random fields.

In this work a random field model for shear-wave velocity profiles is presented. This model is compared with an existing model. Their relative merits in terms of their validity for use in site response analyzes are evaluated. A large database of site profiles from sites in Japan is used to calibrate the parameters of the random field models. Randomly generated profiles using both random field models are generated and compared with measured profiles. The uncertainties associated with the shear wave velocity measurements (i.e. epistemic uncertainty), are also included in the simulations and their effect on the resulting variability is analyzed. The randomly generated profiles are then used in site response analyses. Ground motion variability is also taken into account. The two models are compared in terms of the statistics of the shear-wave velocity random field and in terms of the predicted site response.

Ground motion models at downhole seismic arrays are often inaccurate at frequencies where the upgoing wave interferes with the downgoing wave. At these frequencies, the interference of the waves creates spectral holes in the theoretical amplifications that are often not observed in the empirical transfer function (ETF). We illustrate this behavior by comparing estimates of the ETF to the plane SH-wave theoretical transfer function (TTF) within a laterally constant medium at two KiK-Net stations. One example site, where the 1D plane SH-wave formulation poorly predicts the ETF, shows that modeling the seismic properties as spatially correlated random fields can dramatically improve the fit of the TTF to the ETF. The improved fit results from the seismic scattering produced by the heterogeneities of the random field, thus diminishing the destructive interference between the upgoing and downgoing waves. The scale of fluctuation, or range parameter, of the random field controls the wavelengths of the scattered waves, and thus the frequencies where the scattering will influence the TTF.

Probabilistic risk analyses can provide a quantitative measure of error propagation in the analysis of slope stability and help determine the probability of slope failure. This study proposes two closed-form solutions that estimate the pore fluid load for the Culmann failure mode. The First Order Second Moment and Hasofer-Lind methods make it possible to compute the contribution of the uncertainty in each individual parameter to the overall uncertainty in the slope stability, enabling an assessment of the influence of pore pressure and anisotropic permeability on the probability of failure. Evaluations include an initial comparison of the closed-form solutions with a simple finite element model for flow through porous media, followed by a parametric analysis implementing the closed-form equations. The proposed closed-form solutions for flow effects are comparable to the finite element solutions and thus have the potential to be valuable tools in reliability analyses, provided that the scope of applicability is well understood.

The Terzaghi and Peck (1948) method was the first for predicting the settlement of footings on sand using standard penetration test blow counts (N values). Over the following 26 years, various modifications to this basic method were suggested. Herein, an extensive database of 426 settlement case histories is used to assess the model factors for this family of methods. The uncertainty of the model factors is characterized using the coefficient of variation. Considering the model factor as a random variable, the common "log-normality" assumption is investigated critically. The impact of model uncertainty on the reliability of settlement estimations is discussed, and criteria are given to assess their accuracy and conservatism. For settlement prediction, the uncertainty from the model factor is most influential. The results indicate a low accuracy for all of the methods considered.

This paper addresses an issue often encountered in calibrating resistance factors for pile ultimate capacities based on load test database. In practice, many pile load tests are not conducted to failure but rather only to a multiple of the design load (e.g. twice the design load). This leads to a difficult situation of incomplete information: for these test results, the ultimate bearing capacities of the test piles are unknown. How can these test results still be used to calibrate resistance factors of piles? A full probabilistic framework is proposed in this research to resolve this issue. A local pile test database of Taipei (Taiwan) is presented for demonstration. The analysis results show that the inclusion of the incomplete pile load test data helps in calibrating the resistance factors. Moreover, it is found that the calibrated resistance factors are consistent with the safety factors that are adopted in the current Taiwan design code.

Design rules for reinforced soil walls are being developed using reliability methods, and expressed in Load and Resistance Factor Design (LRFD) format. The main objective of the paper is to summarize the development of methodology and reliability-based LRFD guidelines for reinforced soil structures. First order reliability method (FORM) is used to estimate the probability of failure in four modes of failure viz. sliding, bearing, overturning∖eccentricity failure. Load and resistance factors needed to maintain the stability against four modes of failure by targeting component reliability indices of 3.0 and 4.0 are obtained for various values of coefficients of variation (COV) of friction angle of backfill and foundation soil and horizontal seismic acceleration coefficient. The results have been provided in the tabular form.

The use of the Load-Resistance Factor Design (LRFD) method found in the AASHTO Bridge Design Specifications for design of MSE walls has steadily replaced the Allowable Stress Design (ASD) method, as part of a FHWA mandate to state DOTs for a change over by 2010. Incorporated in the change of design methods has been the core practice for seismic analysis of MSE walls, which adopts a modified Mononabe-Okabe (M-O) pseudo static method together with a horizontal displacement-to-dynamic coefficient reduction developed from a simplified Newmark sliding block model. In this paper, the outcome of seismic design for MSE walls between the LRFD and ASD methods are discussed. Parametric studies are used to highlight the variations that occur in MSE reinforcement design. In addition, the results from dynamic constitutive models are provided for comparison to the M-O pseudo static approach with corresponding reduction basis found in AASHTO.

This paper presents a reliability-based approach at the ultimate limit state for the analysis of a shallow strip footing resting on a frictional and cohesive soil and subjected to an inclined or an eccentric loading. Only the soil shear strength parameters are modeled as random variables. The Hasofer-Lind reliability index is used for the computation of the footing reliability. The response surface methodology is employed for the assessment of the reliability index. The performance function adopted in the analysis makes use of the safety factor defined with respect to the soil shear strength parameters c and tanφ. For both cases of an inclined and an eccentric loading, it was shown that there is a load inclination and a load eccentricity for which the two failure modes involved by the loading case are not predominant. It was also shown that the hypothesis of negative correlation between random variables increases the reliability of the footing and that the failure probability is very sensitive to the variation of the angle of internal friction compared to that of the cohesion.

The efficient design of shallow foundations on granular soil is governed by the accuracy and reliability of current settlement prediction models. Conventional deterministic approaches for settlement prediction disregard uncertainties due to settlement prediction models, inherent variability in soil properties, applied loads, and tolerable settlements. The objectives of this paper are to (1) create probabilistic design charts for two commonly used SPT-based settlement prediction methods based on tolerable settlements and target levels of reliability, and (2) investigate the sensitivity of the reliability-based design of the foundation to the uncertainty in the tolerable settlement, target serviceability limit state reliability index, SPT N-values, and applied loads. Results indicate that the design of shallow foundations on granular soils is significantly affected by model uncertainties, uncertainties in the definition of the tolerable settlement, and the target serviceability reliability index, indicating that future LRFD codes need to incorporate the effects of these parameters in design.

American Association of State Highway and Transportation Officials (AASHTO) allows individual states to use regionally calibrated resistance factors based on the local soil conditions to improve the cost effectiveness of pile foundations as long as the development of these factors comply with the Load and Resistance Factor Design (LRFD) concept. This paper presents preliminary resistance factors developed for the Wave Equation Analysis Program (WEAP) using the PIle LOad Test database of the Iowa Department of Transportation (PILOT-IA). Using the pile penetration rate (blows/m) at the end of driving as the main variable, the LRFD calibrations for WEAP were conducted using 32 sites comprising the following four soil categories: clay (8 sites), mixed soil (11 sites), sand (13 sites), and all soil types (32 sites). Three different procedures, namely the Iowa DOT steel pile design chart, the DRIVEN program, and the GRLWEAP^TM SPT N-value based method (SA), were used to estimate the soil driving resistance. When compared to the AASHTO (2007) recommended LRFD resistance factors, the developed resistance factors for clay increased by 125%, while the resistance factors for the mixed, sand and all soil types improved by 50%. Among the procedures used for estimating the soil driving resistance, the resistance factor based on the SA method yielded the highest efficiency factor for mixed, sand and all soil types, while the Iowa DOT design chart led to the best efficiency factors for clay soil. In addition to using 32 data sets from PILOT-IA, data from three recently completed load tests were used to examine the effect of the pile setup on the resistance factors. Pile driving records and restrike data were used to predict the pile capacity as a function of time and establish a modified empirical pile setup equation incorporating a soil property using the Standard Penetration Test (SPT) N-value. In addition to incorporating this information, the paper demonstrates the benefits of incorporating the soil setup in resistance factor calculations.

Current deep foundation design practice does not account for spatially variable ground (i.e., soil or rock) strength, which may have crucial effects on foundation reliability / failure. Geostatistics and, in particular, the variogram (or spatial covariance function) are tools to characterize spatial variability by quantifying he likelihood of encountering more similar strength values at close-by locations. Using the mean and coefficient of variation CV_q of ground strength point data in conjunction with the spatial covariance allows for "up-scaling" or spatial summation of local strengths over the shaft surface to assess the reduction in shaft resistance variability CV_R with respect to CV_q. Knowing CV_R allows the assessment of LRFD resistance factors Φ asa function of both site properties and shaft dimensions by using the assumption of lognormal load and resistance distributions. Important practical aspects discussed herein are the minimum amount of data required to reliably infer mean, CV_q and variogram of the local strength distribution at a site. A simple equation is given that expresses the benefit of additional samples in terms of uncertainty reduction and increase in Φ. Based on experience with observed field data, a generic variogram is used to illustrate effects of particular spatial correlation features on Φ. Overall, the larger the sill (variance) and scale (range) of spatial variability, the larger is the uncertainty in shaft resistance and correspondingly smaller (more conservative) becomes Φ. Finally, a simple graphical iteration method is presented to directly determine Φ and shaft dimensions from given probability of failure (reliability index), load parameters and core sample strength data.

After the city of New Orleans, Louisiana was hit by Hurricane Katrina and Rita in 2005, significant damages to the Hurricane Protection System (HPS) in the New Orleans area were observed. Due to the unsatisfactory performance of some of the HPS measures, such as floodwalls, during those hurricanes, extensive investigation of the performance of the HPS in the New Orleans area has been undertaken by the New Orleans District of the U.S. Army Corps of Engineers and others. T-walls are one of the most important components of the existing and future HPS systems. The T-walls must be analyzed for unbalanced loads resulting from the stability analysis which are assumed to be carried by the supporting piles beneath the wall. In the past, the New Orleans District of the U.S Army Corps of Engineers had mostly relied upon the Method of Planes (MOP) slope stability analysis for design of hurricane protection measures in the New Orleans area. However, MOP is a simplified procedure which satisfies only force equilibrium. Thus, there is a need to compare the unbalanced loads computed from MOP analysis with those obtained using more robust limit equilibrium methods, such as the Spencer's Method which satisfies both force and moment equilibriums. This paper focuses on the comparative evaluation of the unbalanced loads of New Orleans T-walls using the above two distinct approaches of slope stability analysis. Some results of a typical T-wall analysis using the two procedures are also presented.

Finite Element Analysis (FEA) was performed to evaluate time dependent settlement of a three-stage approach embankment of Lake Jessup Bridge in Central Florida. The subsoil consisted of fine silty to clayey sands with interbedded shallow clays. FEA was performed utilizing Mohr-Coulomb and Soft Soil Creep models, which captured settlement and pore water pressure profiles during construction stages. The Soft Soil Creep model provided better predictions for the long term secondary settlement. Settlement plates were installed to monitor the in-field settlement during and after construction. The monitoring program continued for 8 months, at which, settlement rates substantially decreased. The recorded settlement-time profile was in general agreement with the settlement profile predicted using numerical analysis.

Tangjiashan Landslide Dam, with a height of 82-124 m, a volume of 20.4 million m³ and a reservoir volume of 316 million m³, is the largest landslide dam induced by the Ms 8.0 Wenchuan Earthquake on 12 May 2008. The breaching of the dam threatens more than 1.3 million people downstream. This paper outlines a procedure to estimate the loss of lives (LOL) due to various potential modes of failure of the landslide dam. A regression model with parameters of population at risk (PAR), warning time (WT) is studied. Based on empirical breach parameters, analysis of flood routing in the river downstream the dam is performed using a river analysis program, HEC-RAS. Both the real failure scenario and two assumed overtopping failure scenarios are considered. The inundation area and warning time for each affected zone in each scenario are obtained. A physical model is selected to obtain the population at risk based on historical data and the information of water depth, flow velocity, warning time etc from the analyses using HEC-RAS. Some possible situations of warning time are compared. Based on the regression model with data of PAR, WT, force, and population distribution along the downstream of Tangjiashan Landslide Dam, the LOL can be estimated in different scenarios.

The Rattlesnake Hollow Ash Pond, located in north-central Alabama, was originally constructed in the 1950s with a rock fill dam to provide ash storage for a fossil-fueled electric generating plant. The dam underwent a major renovation in 1979, with a crest raise of approximately 17 m (55 feet), bringing the total height of the dam to approximately 44 m (145 feet). A second crest raise was proposed in early 2004. Feasibility studies and preliminary design evaluated the impact of various crest raise configurations, focusing on stability and seepage issues. After evaluation of options, the decision was made to raise the existing dam 6 m (20 feet) using a steep-sided upstream section consisting of roller compacted concrete (RCC), rock fill on the downstream slope, and a silty clay central core and a granular vertical drain between. Final configuration of the new dam resulted in a maximum height of approximately 50 m (165 feet) and a centerline length of about 500 m (1650 feet). Construction began in late 2006, and was completed in the fall of 2007.

In environmental geotechnics, the valorization of dredging sediments and their use in embankments is a way increasingly prospected by researchers these last years. It constitutes therefore a research orientation in harmony with the concept of sustainable development. This paper relates to the study of physico-chemical, mineralogical and mechanical properties of a sediment obtained by dredging in the Cheurfas dam (west of Algeria) and their influence on the hydro-mechanical behaviour in the case of their valorization in the design of road embankments. Various aspects were studied: (i) influence of the natural content of organic matter and salts on the mechanical properties (ii) influence of water content on the density and the strength of the material. With an aim of valorization, a treatment with sand, lime and cement proved to be necessary. Various formulations were elaborated in this direction. The paper presents a preliminary synthesis of the influence of the formulation on the mechanical behaviour.

The Siah Bishe Pumped Storage Dam is located in the northern part of the Alborz mountain range in Iran. The investigation results and the effect of brittle deformation of two fault sets in the right pressure shaft of Siah Bisheh Dam are discussed in this paper. The shaft is arranged in sedimentary and volcanic highly jointed rocks of Triasic and Jurasic ages. The length of the shaft is 450m and its diameter is 6m with 65 degree inclination relatively south-north trend. The results of geo-engineering surveys using boreholes and statistical joint-graphics of stereograms reveal at least two sets of faults in the rock mass. Several transversal sections along the shafts were studied in order to analyze the effect of faults in shaft collapse. The findings from the surface and underground mapping and investigation boreholes are described and interpreted in a geological map of pressure shaft slope including sections and stereograms. The site area and especially the area of the pressure shaft are characterized by the presence of three important thrust faults that cut through the whole stratigraphic series. The Main Thrust Fault (MTF), fault Nr. 2, both dipping to the north and fault Nr.3 that dips to the south. East of the site, faults 2 and 3 border a large `pop-up' structure while the Main Thrust Fault occupies a lower tectonic position. The results show that the collapse could be a local occurrence which is limited to a critical, fractured and water-saturated rock zone at the boundary between MTF and fault 3. Stability of the shaft was analysed with Unwegde 3.0 software. Result of rock bolting of the shaft was not suitable because of depth of the tip wedges are longer than maximum allowable rock bolt length. The lowest safety factor occurred on wedge number 4 (SF=0.873). But using of shotcrete as a support shows that safety factor of the wedge is increased to 3.219, when shotcrete thickness is 20 cm.

This paper presents a case history of a mechanically stabilized earth (MSE) wall failure along with the results of finite element modeling and evaluation of the failure mechanism. The 11.5-meter high wall is comprised of steel reinforcing strips embedded in compacted backfill and connected to reinforced concrete facing panels. Some of the facing panels were installed atop abandoned drilled caissons that were originally constructed for an adjacent building. At ten of the caisson locations, the reinforcing strips sheared at the connection with the wall panels, and the panels fell off the wall. Results of the finite element analyses indicate that failure occurred due to excessive tensile stresses in the reinforcing strips as a result of differential settlement between the panels and the strips. Parametric analyses were performed for the present and final loading conditions to help devise corrective measures to prevent any future failure of the MSE wall.

This paper evaluates a new analysis approach for reinforced soil walls which considers the structural role of the facing. The three component (soil — reinforcement - wall) system is statically indeterminate, and hence cannot be solved by equilibrium equations alone. In the new approach, this indeterminacy is resolved using kinematic constraints on the compatibility between the reinforcement layers and the wall. The resultant system is fully coupled whereby upper reinforcement layers are affected by the behavior of lower layers. The method has a certain advantage over sophisticated analysis methods, such as finite elements, since it requires fewer input parameters. This paper evaluates the capability of the method to reliably predict the values of tensile forces, bending moment, shear forces and displacement along the wall. The evaluation is conducted through a comparison to sophisticated finite different analyses. The method is also compared to design codes, where it is shown that the design codes may be overconservative.

A finite element (FE) simulation of plane strain compression (PSC) tests of dense sands reinforced with a smooth brass plate is described. In the FEM analyses, the effects of the following factors on sands were taken into account: (a) confining pressures; (b) anisotropy; (c) non-linear pre-peak strain-hardening and strain-softening; (d) dilatancy; and (e) strain localization into a shear band or bands with a thickness in proportional to the particle size. Considering the slippage at the interface between the sands and the reinforcement, Goodman type joint elements were used as interface elements in the numerical simulation, which could reasonably model the interaction behavior between the sands and the reinforcement. The results indicate that the strain-stress relationship obtained by FEM analyses is generally in good agreement with that of plane strain compression tests. It is found that the relationship between maximum stress ratio and pre-peak stiffness obtained from the FEM analyses is close to the experimental result. In addition, it is also shown that the progressive failure of reinforced sands with a development of shear bands can be reasonably examined by the proposed FE analyses, and interaction behavior between the sands and the reinforcement can be better understood.

Finite Element Method has been used to investigate the interaction of soil-retaining wall under the effect of earthquake induced forces. By numerical analysis the behavior of modeled gravity retaining walls have been evaluated under the effect of four real earthquake spectra. Different soil mechanical properties, cohesion and internal friction angle, has been considered. Height of wall was also varied in numerical analysis. Results obtained from numerical analysis then were compared with those calculated by using Mononobe-Okabe method.

Nailed wall is used to support both temporary and permanent structures. The objective of this study is to propose a simplified method of design of nailed soil wall based on experimental investigation and analysis through program SNAILZ. Experimental investigations are carried and to find the influence of nail rigidity number in the failure surface and nail displacement. A simplified method for optimum design of nailed soil wall is proposed based on Nail Rigidity Number (Juran 1990). The SNAILZ program is used to check the validity of proposed method.

Cellular sandwich structures constitute efficient technological solutions to protect elements at risk from rockfall hazard. The design of these structures is for the most part empirically based which does not allow optimization. The mechanical behaviour of a cellular structure is investigated using a multi-scale approach: from the individual layers of the structure made up of rocky particles contained in wire netting cages, fine granular material and reinforced embankment, to the entire structure which is an assembly of these different layers. A computational tool based on discrete modelling of the structure is developed for design purposes. Information is gathered from experiments at the layer scale to calibrate the parameters of the structure model. These experimental results are also used to evaluate the capability of the model to provide relevant results for the impact of falling rocks on the structure.

The paper pertains to the behavior of small-scale model studies on strip footings subjected to vertical loading resting on the surface of a wrap around reinforced vertical soil walls with sand backfill. Finite element analysis (using Plaxis 2D version 8 software) of the soil wall was also made to find its response and the predicted values were then compared with experimentally observed values. Effect of the number of reinforcement layers on the overall response was studied. Comparison of the predicted horizontal displacement of the vertical wall face and bearing capacity of the footing resting on the same showed reasonable agreement with the experimental data.

The paper presents a formulation for evaluating the effects of tunneling induced displacement on existing buildings. Using the matrix condensation method, the building behavior is represented by a relatively small matrix, associated with the foundations of the superstructure. In the formulation, each foundation (with up to 6 degrees of freedom) is represented by a macro-element that captures the elasto-plastic behavior of the soil, using a yield function, a plastic flow potential, and a hardening law. The formulation includes new features that allow interaction between macro-elements, and the effects of the tunneling induced displacements. Since the solution depends on the foundations force level before tunneling (due to the soil nonlinear behavior), the construction process of the building is taken into account in the solution scheme. The formulation is used for the solution of an example problem of a tunnel excavation underneath a six story 3D frame structure. It is shown that vertical plastic displacement may increase even when there is vertical unloading of the foundation, as an outcome of the coupling between the degrees of freedom in the plastic flow potential.

The capabilities to evaluate and control the ground movements due to tunneling are very important to ensure the safety of construction and to reduce the project cost. When a tunnel is constructed at shallow depths in soft soils, even small ground movements may cause detrimental effects to the nearby buildings, underground facilities and sensitive municipal pipelines. This paper introduces the successive surface displacements during the construction period due to a large-diameter (D) slurry shield tunnel, which was built at shallow depths in soft soils in Shanghai, China. Ground movements directly above the centerline of the tunnel were monitored before and after shield passage. Field observations showed that the ground response related closely to depths and deviated from those predicted by those empirical techniques. Moreover, it was observed that when the depth is low enough such as 0.75D, the machine's overall weight and its distribution are unneglectable factors to control the ground deformation.

Accidents caused by lining damage are commonly faced problems of tunnels. These accidents may have detrimental effects on drivers and cars in the form of injury, disability, etc. One of the main causes of lining damage is void behind the lining. This study proposes a risk evaluation methodology for assessment and management of risk associated with void behind lining. In the proposed methodology, risk assessment requires the determination of probabilities and possible consequences. In order to define probability, a statistical method is used; and to define consequence, a finite element analysis is carried out; finally, the proposed method is illustrated with an example and it is found to be useful to evaluate and manage such risks.

This study presents the results from a series of centrifuge modeling experiments performed on tunnels in sand. The goal of these experiments was to evaluate the role of tunnel face movements on both tunnel lining deformations and collapse of the overburden soil. Specifically, a half-space tunnel was modeled, in which a strain-controlled stepper motor was used to withdraw a tunnel face at a constant displacement rate during centrifugation under a target acceleration level. In these experiments, the effects of overburden height, tunnel lining stiffness, and staged construction using the New Austrian Tunneling Method (NATM) were investigated. Relatively narrow shear bands were noticed in all of the collapse tests. Moments and shear forces measured within the tunnel lining indicate that construction staging has the greatest impact on tunnel lining behaviour. The results of the experiments are suitable for investigating whether the design approaches and partial safety factors suggested in EuroCode 7 are appropriate for ultimate state analysis of tunnel faces. Further, they are useful to identify whether modifications of the safety factors for soil and shotcrete lining are needed to achieve low and consistent failure probabilities.

Two-dimensional finite element analyses were performed using the PLAXIS program to investigate the seismic response of an idealized, shallow, cut-and-cover twin-tunnel. The soils underlying the tunnel include a layer of soft clay which is to be improved with cement deep soil mixing (CDSM). The seismic response is mainly evaluated in terms of tunnel drift (the relative horizontal displacement between the upper and lower corners). The results indicate that the maximum drift is generally reduced by the increase in tunnel lining thickness and the CDSM replacement ratio. A 50% of CDSM replacement ratio appears to be most effective in reducing the drift. Effects of other factors, such as acceleration time history, material damping, meshing and calculation step numbers, on the modeling results are also examined.

The Fenghuangling Tunnel is located within collapsible loess and has a cross-section area of 170 m² for excavation. To overcome the difficulty in excavation, the Cross Diaphragm (CRD) Method was adopted to construct this tunnel. This paper presents a three-dimensional numerical analysis using a finite element method program (PLAXIS 3D Tunnel) to simulate the tunnel's excavation process. The effect of rainfall was considered in the analysis. The analysis yields the settlement of the ground surface and subsidence of the tunnel arch, which were compared with the values measured in the field. In addition, axial forces and bending moments of the lining structure and axial forces of the rock bolts were obtained from the analysis. The results show that the bolts within a certain range of the tunnel arc top play a trivial role. The computed safety factors indicate the most vulnerable stage of the entire system during tunnel excavation and also reflect the significant impact on tunnel excavation from rainfall.

This paper presents 3D numerical analysis of a shallow tunnel with advancing face supported by horizontal glass fiber anchors. A hypoplastic constitutive model is used. The model is based on nonlinear tensorial functions and is developed without recourse to the concepts of elasto-plasticity theory. The influence of installation of anchors on surface settlement is studied for the Lainzer Tunnel in Vienna, which is currently being constructed according to the principles of New Austrian Tunneling Method (NATM). The numerical results are compared with the instrumentation data.

Health monitoring of shotcrete on excavated rock surfaces is a crucial issue when considering the short-term and long-term stability of tunnels. The state of the back-surface of shotcrete is investigated using impact-echo (IE) techniques and ground penetration radar (GPR). A laboratory-scale experimental study was performed as a field application in this study. Three different bonding conditions (i.e., void, de-bonded, or fully bonded) were experimentally modeled. Signals obtained from the IE tests were analyzed at the time-frequency domain. Using an integrated active signal-processing technique coupled with a Short-Time Fourier Transform (STFT) analysis, the bonding state of shotcrete can be effectively evaluated compared to GPR. The IE method coupled with the Short-Time Fourier Transformation shows better performance than GPR for monitoring the quality of shotcrete. Limited field tests were also performed to verify the evaluation chart for the health monitoring of tunnel shotcrete linings.

Ballasted Rail tracks are widely used throughout the world due to its resiliency to the repeated wheel loads, low construction cost and ease of maintenance. However, the ballast layer needs periodic maintenance due to its deformation and degradation associated with particle breakage and fouling. A proper understanding of the contamination due to various types of fines and its implications on track drainage is a pre-requisite for effective implementation of track maintenance operations. A new parameter Void Contaminant Index (VCI) can accurately assess the contamination as it includes the effect of void ratio, specific gravity and gradation of ballast and fouling material. A series of constant head hydraulic conductivity tests using a specially designed large-scale permeability apparatus were performed on fresh ballast mixed with different proportions of fines to study the relationship between the percentage of fouling and drainage characteristics. A field trial is conducted on an instrumented track at Bulli, NSW Australia, to study the benefits of a geocomposite layer installed at the ballast-capping interface, and to evaluate the performance of recycled ballast in comparison to traditionally uniform fresh ballast. It is found that recycled ballast can be effectively reused if reinforced with a geocomposite. The geocomposite can effectively reduce vertical and lateral deformations of the ballast with obvious implications on improved track stability thereby reducing maintenance costs.

Sand columns represent one of the options for strengthening weak, soft clays. In some field applications geosynthetic filter materials are used to separate the sand columns from the surrounding clay. The effect of encapsulating granular columns with geofabrics of different strengths and stiffnesses has been investigated by several researchers through laboratory and numerical modeling. This paper presents results from a laboratory program designed to explore the effects of encasing sand columns with geofabrics on the load response of the composite material. A series of consolidated-undrained triaxial tests were performed on samples of kaolin clay reinforced with non-encased sand columns and fabric-encased sand columns. The results are discussed and the effects of the various parameters which govern the load response of the sand column/clay composite are explored. Implications regarding the design methodology and expected behavior of sand column/clay composites are discussed in relation to actual field behavior.

The site of a warehouse expansion in Tampa, Florida was underlain by sand overlying limestone. The performance criteria required ground improvement to densify the upper sand in order to maintain a maximum total settlement of 25 mm (1 inch) for an applied subgrade pressure of 110 kPa (2300 psf). Considering the objectives, displacement grout columns were selected as the ground improvement technique. The efficacy of the displacement grout columns for densifying the upper sands was verified by a pre-production test program that included cone penetration tests and a large-scale plate load test. The cone penetration test results showed a significant increase in tip resistance after ground improvement. The plate load test results showed that improved ground performed consistent with the design requirements. It is concluded that the design methodology proposed by the authors provides a very good estimate of the behavior of ground improved by displacement grout columns beneath shallow foundations.

Greengate Mall was initially developed by placing up to 15 m (50 ft.) of fill. Construction of Greengate Super Center at the same site required additional 15 m (50 ft.) of new fill. The subsurface investigation and analysis indicated possibility of excessive long-term settlement. Wick drains and rock fill were used to solve settlement and time constraint problems and at the same time cut down the overall construction costs. Old concrete was crushed and used as porous blanket over wick drains. Nearby borrow site provided hard sandstone as new fill and a source of pavement base. Rock blasting required monitoring of adjacent dam, bridges, and other buildings. Under new fill the old fill settled by several centimeters (inches) and work was completed on schedule. Thoughtful engineering and careful construction planning saved valuable time and money. The Greengate Super Center and the rock fill embankment have performed well for the last six years with no obvious signs of stress.

This paper presents a review of two models (i.e., arching and lateral squeezing) developed for predicting earth pressures in soil-bentonite (SB) cutoff walls. The assumptions of these existing models are discussed, a modified lateral squeezing (MLS) model is presented, and all three models are compared based on predicted horizontal stresses for representative field conditions. Each model predicts that the stress distribution within a SB cutoff wall may be considerably lower than a geostatic distribution, particularly at depth. The arching model yields the lowest stress distribution but may underestimate the true distribution due to the assumption of rigid trench sidewalls. The MLS model (1) allows sidewall deformation and (2) accounts for the stress-dependent nature of SB backfill compressibility. The study also finds that additional model development is needed to characterize the stress state of a SB cutoff wall in three dimensions.

The strength of deep-mixed ground has relatively high variability with coefficients of variation ranging from about 0.3 to 0.8. This variability can be taken into account in stability analyses by performing reliability calculations. Alternatively, if design is based on deterministic calculations, the specified strength of deep-mixed ground can be adjusted to obtain a design value that accounts for the higher variability of the strength of deep-mixed ground compared to the typical variability of the strength of soil deposits. The magnitude of the adjustment depends on five factors: (1) the probability that the actual untreated soil strength exceeds the assumed design strength of the untreated soil, p_s, (2) the coefficient of variation of the soil strength, V_s, (3) the probability that the actual deep-mixed ground strength exceeds the specified deep-mixed ground strength, P_dm, (4) the coefficient of variation of the deep-mixed ground strength, V_dm, and (5) the design value of the factor of safety, F_d. Statistical calculations provide values of the variability factor, f_v, that can be applied to produce a design strength of the deep-mixed ground such that the probability that the shear strength of the deep-mixed ground will exceed the shear stress in the deep-mixed ground along a potential failure surface is the same as the probability that the actual shear strength of the untreated soil will exceed the shear stress in the untreated soil along the same potential failure surface in limit equilibrium analyses. The methodology and results of such statistical calculations are presented in this paper.

The design, construction and performance of two major Lehigh Valley PA highways are presented as well as special geohazard mitigation measures that were developed for I-78 based upon the PA-33 sinkhole history. The geologic setting, sinkhole history, and subsurface conditions of both I-78 and PA-33 are compared and contrasted. An update of the PA-33 sinkhole activity is presented along with proposed sinkhole mitigation measures currently under consideration. Sinkhole risks posed by planned residential development along I-78 are highlighted along with plans for an expanded Schantz Spring groundwater protection program.

An iterative approach combining boundary element method (BEM) and roller-drum geometry has been developed to estimate the drum-soil contact width. The approach shows good agreement with Hertz theory predictions on half space of known elastic properties. Contact width dependency to layer characteristics has also been examined and indicates the influence of soft subgrade on the variation of contact width. The developed method allows an understanding of contact width variation with roller geometry as well as layered soil characteristics and can be used in sensitivity studies.

In this study the effects of cement kiln dust (CKD), a by-product of cement, on the geotechnical properties and erosion control of a natural slope consisting of fine-grained soil in the state of New Mexico, USA are investigated. Laboratory tests to determine Atterberg limits, compaction characteristics, unconfined compressive strength, and pH were performed on the native soil as well as the treated soil with CKD. The slope in the field was divided into several different portions, and each portion was treated with different percentage of CKD. Laboratory results showed that CKD reduces the plasticity index, maximum dry unit weight, and ductility of the soil while it increases the optimum water content, unconfined compressive strength, and pH of the soil. The field results showed that CKD reduces soil erosion significantly.

The objective of this study was to analyze the micro-structural behavior of composite mixtures of residual soil and sodic bentonite used as contaminant barriers, with and without cement addition permeated by water and caustic soda in a concentration of 5%. The micro-structural behavior was studied in order to explain the results of hydraulic conductivity tests performed in a rigid wall permeameter, using mixtures of soil-bentonite (12% bentonite, 100% water content) and soil-cement-bentonite (water-cement ratio = 4). In order to analyze the interaction between the barrier constituents and the alkaline contaminant, a series of micro-structural analysis were carried out: X-Ray Diffraction, Scanning Electronic Microscopy (SEM) and Energy Dispersive Spectrometer (EDS) Detector. Results demonstrated that the uncemented mixture is destructured after percolation by the alkaline liquid, while the cemented mixture is kept stable without major changes.

Stabilization with binder of oily sediments and recently deposited dredged marine sediments was used in connection with the cap closure of an oil refinery waste management unit. The main objective of binder stabilization was to improve the strength and reduce the permeability and compressibility of a layer of sediments to serve as a cap foundation layer. The design of sediments stabilization was developed on the basis of a phased approach. First a grid sampling investigation was carried out to characterize the composition and engineering properties of the sediments. A laboratory treatability testing program was then carried out to assess feasibility of stabilization with binder, identify the optimum mix design, and evaluate curing parameters. Eventually, a field pilot test was performed to evaluate consistency of mix design performance between bench-scale and full-scale and design a construction and materials acceptance procedure applicable to full scale implementation. The results of the laboratory treatability tests are presented in a companion paper. This paper presents the results of the grid sampling investigation and of the field pilot test. In particular, the paper discusses an approach for in-situ assessment of strength and permeability of the binder stabilized sediments based on the results of cone penetration and double ring infiltrometer tests. This approach, other than providing information on greater volumes of materials and a more rapid response than the conventional sampling and laboratory testing, is considered more appropriate for stabilized materials whose properties are sensitive to curing conditions and sampling disturbance effects.

This paper discusses the results of a laboratory testing program associated with the design a cap foundation layer for the closure of a 66-acre former effluent treatment pond of an oil refinery. Stabilization with binder of a layer of oily refinery sediments and recently deposited dredged marine sediments was selected as the more appropriate technique to improve the strength, reduce permeability and allow for future refinery uses of the capped area, while reducing settlements and long-term grading and maintenance issues that could potentially result from the cap placement and other construction activities. Strength, compressibility, and permeability performance improvement were achieved by using selected binder formulations and a sandy soil physical filler. The cementing effect due to pozzolanic reaction products resulted in a structuration of the very soft, normally consolidated sediments and in the development of a yield stress separating small strains from large strains, which governed the compression and shearing behavior of the treated sediments. Controlled moisture and stress conditions during curing minimized the deterioration of sediments cemented structure due to swell and shrinkage and consequent loss of strength and permeability performance.