IFCEE 2018: Advances in Geomaterial Modeling and Site Characterization

The determination of in-place unit weight and moisture content is a critical component of earthwork construction quality assurance and quality control (QA/QC). Direct measurement methods such as the drive cylinder test, sand cone test, or rubber balloon test can be utilized to determine a soil’s in-place unit weight and moisture content, and have a long history of use in geotechnical engineering. However, these direct measurement methods are destructive in nature and the tests are time consuming to conduct in the field. As a result, nuclear density gauge testing has emerged as the dominant approach for QA/QC of soil compaction in the United States, as this device allows for relatively nondestructive testing (only a small hole in needed to run the test), and quicker testing, which allows for better coverage of a compacted soil area in the field. Conventional nuclear density gauges utilize radioactive sources to determine a soil’s in-place unit weight and moisture content, which can be hazardous to the user and others nearby if proper safety protocols are not followed. A new density gauge has recently been developed (the “EGauge”), which uses the same general principles as the nuclear density gauge to measure in-place unit weight and moisture content of soils, with relatively low emission radioactive sources being utilized in the device compared to more traditional devices (allowing for safer testing). This paper describes the results from a study that was carried out to examine the relative differences between in situ unit weight and moisture content measurements made with a drive cylinder, nuclear density gauge, and EGauge. All testing was performed on an active project site, on soil areas that had been well compacted. After calibrating the EGauge for moisture content, it was observed that all three test approaches were generally in good agreement with one another for the wet and dry soil unit weight and the soil moisture content. The nuclear density gauge consistently underestimated moisture content and consequently overestimated dry unit weight values relative to the drive cylinder measurements. Overall, the EGauge measurements were in better agreement with measurements made by the drive cylinder than they were with the nuclear density gauge test results.

The Menard pressuremeter has been widely used in U.S. Geotechnical Engineering practice for more than 40 years. The Menard pressuremeter, similar to the Texam pressuremeter, requires a borehole to be prepared (and stabilized) followed by insertion of the somewhat tightly-fitting probe (often referred to as a pre-bored pressuremeter test). At times, the quality of the test data can suffer due to collapse of the borehole prior to insertion of the probe, particularly in looser cohesionless sands, soft cohesive soils, and in general soils below the groundwater table. The quality of the test results is often a function of the skill of the engineer/driller forming and stabilizing the probe annulus and not the equipment itself. A direct-push pressuremeter (Pencel model) initially conceived for use in pavement design (1989) has seen a growing increase in use for more traditional geotechnical applications (foundation bearing capacity and settlement, similar to the Menard device). The direct-push Pencel model pressuremeter does not require a stabilized borehole to perform the test with good results. Rather, the probe is merely pushed into the underlying soils much like one would advance a cone penetrometer test (CPT) or dilatometer (DMT) test. The Pencel model pressuremeter is fitted with a conical tip similar to the CPT and was in fact used initially with CPT rods and equipment. The direct push model probe does not require the contributions of a skilled driller, a scarce resource at times. The intent of this paper is to compare the results of the direct-push pressuremeter to the more commonly used pre-bored version, who’s results have been used to engineer many of the country’s more challenging foundation designs. The pressuremeter test results (e.g., pressuremeter modulus, failure pressure, and limit pressure) are used to predict foundation settlement, estimate soil shear strength parameters and evaluate lateral pile performance through several empirical relationships developed over the decades of use. Few studies have been completed to compare the results of differing devices in various geologic settings. This paper summarizes comparison testing between the direct push and pre-bored pressuremeter apparatus in various geologic settings along the East Coast from Florida to Pennsylvania.

The state of Florida is highly prone to sinkhole incident and formation, mainly because of the soluble carbonate bedrock and its susceptibility to dissolution. Numerous sinkholes, particularly Central Florida, have occurred. Florida subsidence incident reports (FSIR) contain verified sinkholes with global positioning system (GPS) information. In addition to existing detection methods such as subsurface exploration and geophysical methods, a remote sensing method can be a precise and efficient tool to detect and characterize sinkholes. By using light detection and ranging (LiDAR) data, the authors produce a GIS-based data layer of a selected area in Central Florida to identify probable sinkholes. A semi-automated model in ArcMap was then developed to detect sinkholes and also to determine geometric characteristics (e.g., depth, length, circularity, area, and volume). This remote sensing technique has a potential to detect unreported sinkholes in rural and/or inaccessible areas.

Since its development by Wolmar Fellenius around 1910, the Swedish weight sounding (SWS) test is among the easiest and most reliable in situ methods for testing soft clays and loose sands. Although, SWS tests have been widely utilized for post-earthquake liquefaction assessment, existing equations can vary depending on soil type and deposition conditions; hence, verification is recommended. In this study, we analyze the applicability of existing equations to estimate the undrained shear strength of a lacustrine clay. Deposits of this material are generally normally consolidated, reach depths of about 500 m, and near ground surface often alternate with very thin layers of fine sands. Structures founded on this material, sustained widespread damage during the 2015 Gorkha earthquake. The authors conducted SWS tests at six different locations within the same deposit, as well as, vane shear tests (VST) to compare existing correlations between the undrained shear strength and Swedish cone penetration values. Additionally, constant volume simple shear tests were performed in the laboratory and undrained strengths were compared to those from the in situ tests. The results obtained from the SWS, VST, and laboratory tests were comparable to each other.

Sinkholes are the most common geohazards occurring in east Central Florida (ECF). To understand the sinkhole formation and karst hydrogeology within the ECF region, it is necessary to investigate the sinkhole triggering factors. The main purposes of this study are: (1) to develop a decision-tree based model for sinkhole hazard assessment, which accounts for multiple sinkhole affecting factors; and (2) to construct a sinkhole hazard map of east Central Florida (ECF) using the developed decision tree model. The decision-tree model, a popular classification method in data mining, accounted for five identified factors including geology formation/epoch, overburden thickness, hydraulic head difference, groundwater recharge rate, and proximity to karst features. In this study, the recorded 757 sinkhole locations in ECF were randomly split into 70:30 for training and validation purposes, respectively. The performance test of a produced sinkhole hazard map was carried out with a density analysis where density values should increase from the very low to the very high hazard class.

South Florida has multiple limestone (carbonate-rocks) formations formed during the Pleistocene Epoch near the ground surface. The FDOT is considering their use to support shallow foundations beneath bridge piers or bents. Required for design is assessment of the rocks’ bearing capacity which requires a strength envelope for the rock, as well as identifying their stress-strain response, for identifying failure modes (general, local, and punching). Using Brazilian splitting tension and a Hoek triaxial compression cell (Hoek and Franklin 1968), various confining pressures and volumetric measurements were obtained for multiple rock formations in south Florida. Based on the triaxial measurements, the limestone samples transition from brittle behavior at lower confining pressures (50 kPa or 7 psi) to ductile response at higher confining pressures (1,400 kPa or 200 psi). Also based on triaxial testing, the south Florida formations exhibited volumetric contraction during shear. Influencing the response were several index measurements: dry densities, outer and inner porosities as well as chemical carbonate content of the rock, which are specific to each formation (e.g., Miami, Fort Thompson, Anastasia, and Key Largo).

During the construction of earth structures, it is essential that the fill material be uniformly compacted to meet the compaction specification requirements. Current compaction verification methods require field inspectors to perform in situ quality assurance/quality control (QA/QC) “spot tests” at a finite number of locations within the compacted area. As a result, a large percentage of the compacted area remains unverified. Innovative compaction verification techniques have been developed, such as continuous compaction control (CCC) and intelligent compaction (IC) systems, which provide real-time monitoring and feedback about the operation and performance of soil compaction. Typically, these CCC and IC systems measure the response of the coupled soil-drum interaction using indicator values which relate to the soil stiffness. To encourage adoption of IC and CCC technology, it is beneficial to have these technologies incorporated into construction specifications. Relating these “new” intelligent compactor measurements to more traditional in situ localized “spot test” results helps to illustrate their effectiveness, and makes users more comfortable with their deployment in a field environment; it can also help in the development of new specifications. This paper examines the relationship of two CCC measured values, compactometer value (CMV) and machine drive power (MDP), with measurements taken from four different in situ test devices, including the nuclear density gauge (NDG), lightweight deflectometer (LWD), soil stiffness gauge (GeoGauge), and dynamic cone penetrometer (DCP). The use of both univariate and multivariate regression analysis were examined to develop relationships between CCC measurements and in situ test measurements. The resulting relationships may be used to assess the potential of CCC systems as a QA/QC method for compaction verification of soils.

Soil can become hydrophobic following wildfires, oil-spills, or due to the presence of organic substances. While this phenomenon has been widely observed by researchers, there is little information regarding the shear strength properties of hydrophobic soil to date; therefore, this study investigated the shear strength of artificially hydrophobized sand particles. Hydrophobic particles were created by coating Ottawa sand particles with organic silane to form water repellent films around the particles. Direct shear tests were conducted at multiple normal stresses for the naturally hydrophilic and artificially hydrophobic sands under dry and submerged conditions. In the dry condition, the hydrophobic sand showed an average 26% reduction in peak shear stress, with the angle of friction reducing from 36.9 to 29.7° compared to the hydrophilic sand. The average peak shear stress reduction was 34%, with the angle of friction reducing from 38.7 to 26.1° in the submerged test. These results indicate that particle hydrophobicity reduces shear strength. This study highlights that with the increasing number of disasters that results in soil hydrophobicity, more research is needed on the strength properties of hydrophobic soils.

Fifty-five different soil samples were prepared in the laboratory from montmorillonite, kaolinite, illite and quartz to have plasticity indices ranging from 4 to 280 and activities between 0.2 and 4.7. In addition, 36 selected samples were prepared using saline water as the pore fluid. The hydraulic conductivities of these 91 soils were determined using 1D consolidation tests at effective vertical stresses between 25 and 1,600 kPa. An increase in the effective vertical stress resulted in an increase in the coefficient of consolidation in kaolinite or illite dominated soils, but a decrease in the coefficient of consolidation in the montmorillonite dominated soils. The hydraulic conductivity was observed to decrease with an increase in the effective vertical stress in all of the mixtures. The coefficient of consolidation would either remain unchanged or decrease with an increase in the salinity in kaolinite or illite dominated soils. However, in montmorillonite dominated soils, the influence of the salinity on the coefficient of consolidation depended on the effective vertical stress with a decrease observed for effective vertical stresses less than 100 kPa and an increase for effective vertical stresses greater than 100 kPa. In kaolinite or illite dominated soils, an increase in salinity resulted in reductions or negligible changes in the hydraulic conductivity, while in montmorillonite dominated soils, the hydraulic conductivity increased with an increase in salinity. Increasing the plasticity of the soil mass would result in decrease in the coefficient of consolidation and the hydraulic conductivity of the samples.

Due to the inherent nature of the deposition process of soils in costal and marine environments, the stability of clayey slopes requires accounting for the shear strength parameters when sodium chloride (NaCl) is present in the pore fluid. To examine the influence of the salinity on the undrained shear strength of clayey soils, seven soils, as mixtures of montmorillonite with quartz and kaolinite with quartz, were prepared in the laboratory with saline water of 0.5 M NaCl concentration, as the pore fluid. The soils were subjected to constant volume, strain-controlled static simple shear testing to obtain the undrained and fully softened shear strengths. Similar tests were conducted on soils with the same mineralogical compositions, but with distilled water as the pore fluid. The results from this study demonstrate that the undrained and fully softened shear strength of these soils will be greater when NaCl is present in the pore fluid, but a reduction in the shear strength can be expected when the NaCl is leached out from the soil samples. The experimental results suggest that the difference in both the total and effective fully softened friction angles will increase with an increase in plasticity index up to plasticity indices of 100. For soils with plasticity indices greater than 100, the difference remains constant at 9° for the total fully softened friction angle and 15° for the effective fully softened friction angle.

When expansive soils with high sulfate content treated with calcium-rich conventional stabilizers such as lime, cement, and fly ash, excessive swelling and heaving will occur due to the formation of highly expansive ettringite. Therefore, nontraditional chemical stabilizers including ionic soil stabilizers (ISS) are potential alternatives for stabilizing pavements subgrade soils. The objective of this research is to understand the impacts of different ISS dosage levels on the engineering performance of expansive clays located in Texas and Colorado. Atterberg limit tests, standard compaction tests, 1-D swell tests, and unconfined compressive strength (UCS) test of the clay before and after treatment with ISS were carried out. UCS results shows increase of ISS dosage lead to increase of UCS strength and decrease of swell strain.

The numerous issues associated with the excess steel slag that is disposed of in landfills every year can be reduced by using it as a geo-material. This paper provides the results of laboratory tests (i.e., sieve, hydrometer, specific gravity, compaction, compaction-particle degradation, and large-scale direct shear with a box size of 30.5 × 30.5 × 20 cm) performed on electric-arc-furnace ladle [EAF(L)] steel slag from a mini-mill in Indiana. Based on standard proctor test results, the maximum dry unit weight values of the EAF(L) steel slag were in the 16.8-to-20 kN/m³ range at the optimum moisture contents of 11–13%. The results of the large-scale direct shear tests performed on EAF(L) steel slag, compacted at 95–100% relative compaction and sheared with normal stress ranging from 50 to 300 kPa, showed that it has excellent frictional characteristics, with friction angles between 40 and 45°. Based on the results from this study, due to its shear strength characteristics, EAF(L) steel slag has the potential to be utilized as a geo-material to improve the shear strength of various marginal soils.

Soil classification systems for fine-grained soils use liquid and plastic limits to determine the soil group, and these are determined based on the soil water content at a given state. Natural soils deposited in freshwater or marine environments often contain diatom microfossils. This paper discusses the limitations of classifying soils that contain diatom microfossils using the unified soil classification system (USCS) and a fines classification based on pore-fluid sensitivity. Natural low-plasticity soils and diatomite-soil mixtures are used to illustrate the challenge for classification purposes. The mixtures fall in classification groups of medium or high plasticity despite being composed of low-plasticity materials. Classification results may not be representative of the consistency and engineering behavior based on material gradation and plasticity characteristics. This issue is explained by the large water holding capacity of the intraparticle pore space of diatom frustules, which increases considerably the soil water content and liquid and plastic limits.

The results of probabilistic analysis of simple and layered slopes with linearly increasing (mean) undrained shear strength with depth, and spatial variability using the 2D non-circular random limit equilibrium method (RLEM) are presented. For the case of simple slopes, the results of the circular RLEM approach and the random finite element method (RFEM) are also presented and are compared to the results of the non-circular RLEM approach. For the case of simple slopes, it is shown that the non-circular RLEM approach gives higher values of probability of failure compared to circular RLEM and RFEM. For the cases with mean value of factor of safety greater than one, considering spatial variability reduces probability of failure.

Expansive clay soils containing active clay minerals are considered to be among one of the most problematic soil types. As their overall behavior is controlled by the molecular level processes and interactions, a behavior model encompassing the contributions from these interactions is required. This interaction becomes increasingly complex for natural expansive clays where a complex composition of clay and non-clay minerals exists. The authors developed a nano level constitutive model for the natural expansive clays through a three-phased study consisting of macro level swell potential testing, micro investigation of the pre and post swell specimens, and molecular level modeling through molecular mechanics, molecular dynamics, and Monte Carlo techniques. In this paper, this nano level constitutive model, incorporating all the major contributing factors such as moisture content, density, cation exchange capacity, exchangeable cations, and interaction of clay minerals with non-clay minerals have been used to predict the swell behavior of the treated expansive clays.

The mechanical and hydraulic behavior of most soils is often directly reflected in the particle size distribution of the soil. For fine grained soils, the distribution of particle sizes smaller than 0.075 mm is determined by a sedimentation process, using the hydrometer analysis. The hydrometer analysis measures the change in specific gravity of a soil-water solution with time and relates that change with the distribution of various particle sizes. The change in specific gravity of a solution also results in a change in the electrical conductivity of a soil-water solution. This paper presents the development of a generalized model to predict the particle size distribution of fine grained soils from the changes in electrical conductivity measurements of a soil-water solution with time. The developed model included several fitting parameters, which were found to be dependent upon soil type. To enhance applicability of the developed model, the fitting parameters were formulated based on electrical conductivity measurements corresponding to Atterberg Limits of soils. This approach made it possible to predict the entire particle size distribution, smaller than 0.075 mm, without needing to conduct conventional hydrometer test.

Ground vibrations due to impact pile driving operations can become a major concern when affecting nearby structures and underground utilities. In an effort to better understand the transmission and dissipation of energy into the ground during impact pile installation, reduced-scale pile driving tests were conducted in an indoor cylindrical (6.5 m diameter and 1.8 m deep) sand pit at the University of Michigan. Sensors were placed at various depths from the ground surface and distances from the driven pile to record ground motions. In addition, the model pile was equipped with the pile driving analyzer (PDA) system to accurately assess the energy transfer from hammer to pile. The pile installation process was then simulated using 3D finite element (FE) dynamic analyses. The combination of ground vibration monitoring data and records of the impact force from the PDA testing collected from the small-scale pile driving tests in a controlled laboratory environment, offer a great opportunity to validate the numerical code. The recorded ground motion measurements from the impact driving of the model pile are compared with the calculated velocity-time histories from the FE numerical simulation of the pile driving test. Both measured and calculated ground motions verify the hypothesis of the wave propagation field generated by impact driven piles, as presented by Woods (1997).

Ground surface deformation due to subsurface structures has been one of the major concerns in foundation engineering. Pressurized subsurface cracks created by hydraulic fracturing may induce surface deformation and recently this technique has been employed in a variety of disciplines in civil and environmental engineering. Conventionally, analytical solutions have been used to predict surface deformation due to a pressurized crack, but they are typically based on an assumption of a planar crack with simple shape located in an infinite solid ignoring the impact of actual crack morphology and ground surface, which may lead to significant errors in estimating surface deformation. This paper describes a new numerical method to estimate ground deformation due to a pressurized crack with arbitrary surface morphology. In this approach, surface of the crack is discretized with a finite element mesh. We then calculate displacement field around the crack using Somigliana formula with given displacement at each node on the crack’s surface. Here, Mindlin’s solutions for nuclei of strain in a semi-finite solid are used as kernel functions. Integral equation of Somigliana formula is solved numerically with Gaussian quadrature. Comparison of the calculation results with those from analytical solutions indicates that the new numerical method can provide the same displacement field at points close to a crack where the impact of the ground surface is negligible. Furthermore, calculation results demonstrate that analytical solutions significantly underestimate displacement at points on the ground surface due to the lack of consideration of ground surface. These results validate that our method for a semi-infinite solid has advantages over analytical solutions for the estimation of ground surface deformation.

The random limit equilibrium method (RLEM) is a relatively new method of probabilistic slope stability analysis which uses a combination of 2D random field theory, limit equilibrium methods, and Monte Carlo simulation. The random finite element method (RFEM) uses a combination of 2D random field theory, finite element method of analysis, strength reduction method, and Monte Carlo simulation. In this paper, the effects of mesh size, number of slices, and number of Monte Carlo simulations on computed probability of failure are investigated using both approaches. Computation times using both methods to solve the same slope problem are also compared. Recommendations for mesh size, number of slices, and number of Monte Carlo simulations, with respect to the spatial correlation length, using RLEM are presented.

The bounding surface model for cohesive soils has been progressively improved and expanded over the last 30 years. The generalized bounding surface model (GBSM) has been developed to continue improving the predictive capabilities of the model. The GBSM for cohesive soils is a fully three-dimensional, time-dependent model that accounts for both inherent and stress induced anisotropy employing a non-associative flow rule. This paper evaluates the performance of the GBSM in the simulation of two different cohesive soil subjected to monotonic loading. These simulations illustrate the flexibility of the GBSM.

Lightweight fill materials, including foamed glass aggregates are increasingly being used in civil engineering and infrastructure applications in the U.S. The energy saving assessments have proven that the use of foamed recycled glass as engineering material has much lower energy consumption relative to a conventional aggregate-cement material. However, due to the large size and brittle nature of the aggregates, costly large-scale engineering tests are required to evaluate the properties of the material. Therefore, a unique simulation was developed within an open source molecular dynamics environment to model the behavior of these materials. The simulations incorporated a granular contact model coupled with a unique bonding mechanism to reproduce the brittle response of the material. Several geotechnical design characteristics such as stress-strain behavior and lateral earth pressure coefficient were obtained.

A method for directly computing the plastic modulus, and slopes of the plastic potential and yield surfaces was developed and applied to a uniformly graded sand. The method requires drained triaxial experiments under a constant mean effective stress subjected to small undrained perturbations at regular intervals. Using the incremental formulation of plasticity theory, the plastic modulus and slope of the yield surface is computed from measurements at points along the stress path where loading transitioned from drained to undrained. The proposed technique can map conventional isotropic or kinematic yield and plastic potential surfaces and may be used to develop new and more accurate elastoplastic constitutive models. To enable research verification and data reuse, the data, visualization codes, and corresponding documentation were curated and published on DesignSafe Cyber Infrastructure (http: www.designsafe-ci.org).

The undrained shear strength of normally and overconsolidated clays are required in a number of geotechnical applications including evaluation of the stability for embankments and slopes. While researchers have examined the effect of the overconsolidation ratio on the undrained shear strengths and proposed models such as SHANSEP to estimate the undrained shear strength of fine-grained soils, the influence of mineralogy and plasticity on the undrained shear strength has not been extensively studied. To do so, various mixtures of montmorillonite, kaolinite, and quartz were prepared in the laboratory and consolidated in oedometer to obtain soil samples at overconsolidation ratios ranging from 1 to 32. The undrained shear strengths of these overconsolidated soil samples were then measured using a constant volume simple shear device. As expected, the undrained strength ratio was found to increase as the overconsolidation ratio increases. At a given overconsolidation ratio, the value of the undrained strength ratio was greater for soils with a lower plasticity index. However, the dependence of the undrained strength ratio on the overconsolidation ratio was eliminated by normalizing the measured undrained strength ratios with the undrained strength ratio of normally consolidated soil sample. Unique relationships were developed between the rate of increase of undrained strength ratios with the overconsolidation ratios and plasticity characteristics, separately for high plasticity and low plasticity soils.

Granular column collapse has recently been an attractive topic of numerous experimental and numerical studies. Despite the importance of quasi-static collapse of granular construct (e.g., retaining structures), less focus has been dedicated toward simulation of this phenomenon compared to the dynamic granular collapse. This research tries to address this issue by simulating the quasi-static collapse of granular columns using the smoothed particle hydrodynamics method (SPH). The SPH rectangular columns are made of boxes with aspect ratios ranging 0.5–11. The slow movement of the side-wall of the box with a constant velocity triggers the quasi-static collapse. To model elastic–plastic soil behavior, the Drucker–Prager constitutive model with non-associated plastic flow rules is implemented into the SPH formulation. The dependency of flow pattern and final deposit profile (i.e., final height and runout distance) on initial aspect ratio, and sensitivity of the deposit profile to the wall velocity and material properties (e.g., friction angle) are investigated. The simulation results are compared with other experimental observations and numerical simulations available in literature.

Soil is a natural material formed through different complex processes. Therefore, inherent uncertainty in soil behaviour is inevitable. Considering the fact, present study analyses the reliability of observations made during an experimental investigation through a probabilistic approach. The probabilistic analysis can account the stochastic nature of test data for a rationale and reliable design methodology. The physical investigation was carried out on layered soil having different thickness of sand layers overlying clay subgrades of varying shear strengths. A considerable variation was found for the estimated soil parameters, which necessitates reliability analysis through finite element modelling (simulates ideal conditions) to study the acceptability of experimental outcomes. The FE analysis is carried out in commercially available numerical software, where, the soil is considered as an elastic-perfectly plastic material follows Mohr-Coulomb failure criteria. The probability of failure (P_f) is obtained by developing a “response surface” based on the finite element models. The 2^k factorial design is adopted for the analysis; wherein, the points are estimated at 3-standard deviations away from the mean value. The results obtained indicate the foundation performances are largely dependent on the subgrade strength. Although the deterministic finite element results show a good agreement with the experimental results, the geotechnical-variation of random variables results in an unacceptable P_f. The c_u is found to be the most sensible parameter affecting the foundation-behaviour; while the unit weight of soil has negligible influence.

Hydraulic conductivity and soil-water retention are both important transport properties in unsaturated soils. It is time consuming and labor intensive conducting experiments to measure these properties. This paper presents a heuristic approach that combines limited number of experimental measurement with computational model to accelerate the testing process. A microstructure-based finite element model is established to describe the unsaturated soils. In the model, phases of soil (soil particle, water, and air) are randomly distributed based on their respective volumetric contents. The intrinsic properties of each phase are applied based on the microscopic structures. The bulk hydraulic properties are then calculated according to the discharge rate using Darcy’s law. The intrinsic permeability of each phase of soils is firstly calibrated from the bulk hydraulic conductivities measured under dry and saturated conditions, the calibrated intrinsic permeability of each phase is then used to predict the hydraulic conductivities at different extent of saturations. Mualem’s equation is applied to fit the pore size parameter and the soil-water characteristic curve is predicted from Genuchten’s equation. The simulation results are compared with the experimental results from documented studies and excellent agreements were observed.

A parametric study was performed to understand the behavior under cyclic loading of natural soils having different mineralogical composition and depositional environments. Soil samples were collected from seven different locations including 2015 Gorkha Earthquake affected area in Nepal and the Portuguese Bend Landslide in southern California. Those soil samples were subjected to monotonic and cyclic simple shear tests at various testing conditions. Cyclic strength curves, stress-strain hysteresis, and shear modulus reduction curves were developed for all of the tested soil samples. The results demonstrated an increase in the cyclic strength with increases in the plasticity index. The cyclic strength was also found to depend upon the mineralogical composition of the soil mass. Highest relative cyclic strengths were observed at consolidation pressures of 50 kPa with little differences in the relative cyclic strengths between consolidation pressures of 100 and 800 kPa. The relative stiffness of the soil mass was seen to increase with an increase in the consolidation pressure.

Assessing post-liquefaction shear strength is critical to robust design within a performance-based earthquake engineering framework. However, most research in soil liquefaction has focused on triggering of liquefaction and not post-liquefaction response. In addition, the liquefaction and post-liquefaction response of gravelly soils is not as well understood as sandy soils due to the challenges of testing large particle size materials in the laboratory. In this study, a prototype large-size cyclic simple shear (CSS) device was utilized to evaluate the post-liquefaction response of uniform gravels. Tested materials included 9 mm sub-rounded pea gravel, 8 mm angular crushed limestone, and 5 mm angular crushed limestone. Constant volume simple shear tests were performed to assess post-liquefaction undrained shear strength. Shear wave velocity was also measured in every specimen using a custom-built accelerometer system and was used as a comparison metric for test data with other laboratory and field data. Comparisons were made between existing design charts for clean sands and the data for uniform gravels in this study. Test results show that, in general, uniform gravels have higher V_S1 values and greater post-liquefaction undrained shear strengths than the sands from case histories.

Recent studies have shown that numerical models of buildings subjected to earthquakes, reasonably matched observed performance of buildings in centrifuge testing, particularly if the foundations of the structure are placed on or close to the ground surface. Very little has been studied on the influence of basement levels on the seismic response of structures. Seismic response of buildings is highly influenced by substructures. Ignoring their presence in numerical models would lead to inaccurate predictions of the seismic response of low-rise buildings. Numerical simulations using the UBC3D-PLM model were performed in hypothetical low-rise buildings with and without basement levels, when subjected to different earthquakes. The numerical simulations suggested that the inclusion of a basement level positively influenced the seismic performance of a building and conclusions are drawn about the seismic-induced settlements, maximum building drifts, and peak story accelerations.

Soil liquefaction is one of the major geohazards triggered by an earthquake. It can cause lateral spreading, ground settlement, sand boiling, which in turn, may damage buildings and infrastructure and result in loss of life. While many case histories of soil liquefaction have been reported after recent major earthquakes, few focused on detailed study of liquefaction effects on buildings and infrastructure. The objective of this ongoing study is to develop case history database of liquefaction effects, in particular, liquefaction-induced building and infrastructure damages. Using the February 22, 2011 Canterbury earthquake as an example, this paper compiles nine case histories of liquefaction-induced building damages. The development of the case history database, including the compilation and processing of information on site condition (geological and geotechnical condition), earthquake shaking, and site response (land and building damage), is reported. Such a case history database could be used for the performance-based liquefaction risk assessment and as a basis for developing liquefaction hazard mitigation measures.

Most foundation design projects in seismically active regions include liquefaction potential evaluations at least to screen sites that are potentially susceptible to liquefaction. The existing guidelines based on the simplified procedure or the cyclic stress method for such screening procedure is based on field correlation that uses either field penetration resistance from standard penetration test and cone penetration test or shear wave velocity (V_s) measurements. Fines correction factor is one of the corrections that is routinely applied to these field measurements to estimate cyclic resistance ratio (CRR) of the foundation soil. However, soils containing fines, especially non-plastic fines, have been reported liquefied. A laboratory investigation was carried out to examine the effects of non-plastic fines on shear wave velocity measurements and undrained cyclic strength of a sand with varying percentages of non-plastic fines. Top and bottom platens of a triaxial cell were equipped with bender elements to facilitate shear wave velocity measurements on the same specimen that was tested cyclically. In general, V_s and CRR decreased as fines content increased in comparison to the host sand. The results do not quite support the present form of fines correction in the V_s-based simplified procedure.

Thermal conductivity dry out curves (TCDCs) representing the relationship between thermal conductivity and pore water saturation have been measured for two sandy soils under elevated temperatures. Experiments were conducted using an evaporative technique in a temperature-controlled oven at temperatures up to 75°C for concurrent thermal conductivity, temperature, and volumetric water content measurements. Thermal conductivity of both sands at low to intermediate saturations (S ~ 0.1–0.5) increases appreciably at elevated temperature. Maximum thermal conductivity occurs at 75°C and around the point of critical saturation (S_c ~ 0.1–0.13), where thermal conductivity is about twice that at room temperature (~23°C). This is attributed to the influence of latent heat transfer from vapor diffusion at air-water interfaces, which have a maximum surface area within this saturation regime. A new empirical model is proposed for predicting thermal conductivity dry out curves at elevated temperatures. Modeled TCDCs show good agreement with experimental results. Performance of the model is evaluated by comparison with existing models for TCDCs at elevated temperatures.

Multistage triaxial tests offer a convenient alternative to determine the mechanical response of saturated and unsaturated soils. However, the primary challenge is to accurately identify the point of termination of the initial shearing stages prior to the failure of the brittle specimens. Hence, in this paper, the previous methodology used to define the point of termination of the shearing stages were studied in detail. Based on the limitations of methods used in the previous studies, a new twofold criterion integrating the variation of initial tangent modulus and the volumetric strain response with shearing has been proposed. The new approach was validated by comparing the results obtained from multistage triaxial tests and those from single-stage triaxial tests at low suction state under drained conditions. Each multistage test was performed on an isotropically consolidated specimen of silty soil at constant matric suction and different net confining pressures. Subsequently, it was confirmed that the shear strength parameters from both types of tests were practically identical.

Microstructural testing techniques allow for precise examination of the micro-level characteristics of soil. In this study, various testing techniques were preformed to investigate the microstructural properties of Vicksburg Buckshot clay and to determine the effects of temperatures between 23 and 1,000°C on its microstructural characteristics. Thermal gravimetric analysis (TGA), field emission scanning electron microscopy (FESEM), and cation exchange capacity (CEC) were employed to examine how soil’s weight, fabric, and CEC change as a function of temperature, respectively. The TGA results indicate the temperatures at which mass changes occur in the soil. FESEM data revealed minimal changes with respect to temperature on the soil fabric. Also, it was shown that the CEC of the soil decreased significantly with increased temperature beyond 100°C. These findings are important for the first steps toward a complete thermal characterization of the microstructure of the material, which will yield a better understanding of any soil system subject to extreme thermal loading.

Climate change is expected to alter the statistics of extreme events including rainfall storms, floods, droughts, and heatwaves. Climate-adaptive geotechnical structures warrant a quantitative assessment of the impacts of emerging and projected extreme patterns on the short and long-term behaviors of earthen structures. Furthermore, long-term changes to soil carbon and moisture due to non-extreme climate events should also be considered. While several large-scale studies have been conducted to evaluate various aspects of climate change, there is a clear gap in the state of knowledge in terms of assessing the resilience of geotechnical structures to changes in climatic trends (e.g., warmer climate, protracted droughts, intensified extreme precipitations, and sea level rise). The majority of the aforementioned climatic trends pose multi-physics problems involving thermo-hydro-mechanical (THM) processes in partially saturated soils and earthen structures. This review paper discusses how soil-atmospheric interactions and extreme event patterns in a changing climate can alter soil properties and loading conditions, affecting the performance of partially saturated geotechnical structures. We speculate how changes in climatic trends may weaken partially saturated earthen structures through strength reduction, drying, soil desiccation cracking, shrinkage, microbial oxidation of soil organic matter, fluctuation in the ground water table, land and surface erosion, and highly dynamic pore pressure changes. Each of these weakening processes is primarily induced by variations in the soil moisture and temperature. Finally, we discuss potential modes of failure imposed on partially saturated earthen structures by climatic trends.

There is increasing activities in various types of rocks to not only produce oil and gas but also to construct transportation tunnels, support bridges, buildings, and storage facilities in sandstone, shale, and limestone. In this study, over 750 data were used to characterize the sandstone, shale, and limestone rocks behavior. The compressive strength and tensile strength of the rocks investigated varied up to 200 and 11 MPa respectively. The rocks were characterized based on the density, tensile strength to compression strength correlations. The density of sandstone, shale and limestone were in the range of 1.8–2.78 gm/cm³, 1.7–2.60 gm/cm³, and 1.7–3.0 gm/cm³ respectively. Vipulanandan correlation model was effective in relating the tensile strength to the compressive strength of the rocks. There was no direct correlation between the compressive strength and density or tensile strength and density of the rocks. A new Vipulanandan failure model was developed to not only better quantify the tensile strength but also to predict the maximum shear strength tolerance of the rocks. The prediction of the new failure model for all three rock types were compared to the Mohr-Coulomb failure model. Based on the coefficient of determination and the root mean square error values, the new Vipulanandan failure model predicted the results better than the Mohr-Coulomb model.

A sea-crossing bridge is able to shorten distance between two areas obviously, which are consequently developing rapidly in China recently. However, available bridge groups for sea-crossing bridges can be scattered in a sea-area island, which is limited by topographic settings. Construction conditions and stability of bridges are determined by the rock-mass strength of islands outcrops. Through laboratory tests of rock mass strength and large-scale field shearing tests, plus detailed analysis of special geological environment features of the islands and engineering analogy method, a method of acquiring rock-mass mechanical parameters was constructed reasonably. The suggestive value for physical and mechanics parameters for basic anchorage rock mass in a bridge case was proposed in this paper.

Thermal properties of geological materials are required for analysis and design of energy geostructures. In Florida the weathered limestone bedrock, which has highly variable engineering properties, can be found near the ground surface and its thermal properties will need to be incorporated into the design of such systems. Thermal conductivity values for split tension sized specimens were determined using a specially designed thermal apparatus. The apparatus is capable of determining four thermal conductivity values for each specimen, which provided a measure of variability of the measurements. Thermal conductivities ranged between 2.65 and 3.75 W/m-K with specimen measurement standard deviations and coefficient of variations as high as 0.415 W/m-K and 11.1%, respectively. The variability of the results can be attributed to both dissolution, which would decrease thermal conductivity, and dolotomitization, which would increase thermal conductivity. Thermal conductivity values are in the lower range of values reported in the literature.

Shale rocks have complex properties which need to be characterized for development of shale gas reservoirs. In particular, static-dynamic properties relationship, ductile behavior, and anisotropy are among the important characteristics of these formations. The hysteresis behavior of Marcellus shale formation through cyclic experiments is presented in this study. Shale specimen used in this study was extracted from a shallow well (~100 m deep) located at State Game Lands 252, Allenwood, Pennsylvania. The experiment was performed at a confining pressure of 30 MPa following cyclic stress path for deviatoric stress (DS). Young’s modulus during loading stages increases till DS of 40 MPa followed by continuous decrease of Young’s modulus at higher stresses. However, during the unloading stages, it is continuously decreasing. Moreover, as the loading level increases the permanent deformation on the specimen is more significant. Additional cyclic experiments are under way to better characterize the cyclic response of these formations.

Shale rocks are the source rocks for many world’s most important energy resources, i.e., oil and natural gas. Understanding the geomechanical properties of shale rocks, including the anisotropic behaviors, is crucial to develop the shale energy extraction technologies. This paper describes the multimodal characterization of the anisotropic behaviors of a typical gas shale rock in Ohio, USA. The multiple approaches, including contact angle test, micro-indentation test, non-invasive wave speed test, and drilling test, are employed and compared between parallel and perpendicular directions related to bedding planes. The results show that the first three approaches can successfully identify the anisotropic properties of gas shale rock regarding the surface energy, hardness, and elastic properties. The drilling test has great potential to characterize the anisotropic behaviors of the shale rocks.

The use of standard penetration testing (SPT) combined with Shelby tube sampling and incremental consolidation testing to select geotechnical design parameters for cohesive soils is standard practice in New England (and in most of the United States). Often, sample disturbance and insufficient data collection lead to conservative design parameters and conservative settlement estimates, which affects foundation selection, and ultimately cost and schedule for a project. This paper will present two case studies, one in greater Boston and one from western Massachusetts, where Sanborn Head conducted numerous test borings using SPT data, as well as, performed CPTu and DMT soundings to better understand soil behavior and strength parameters in Boston Blue Clay and Connecticut Valley Varved Clay. This paper will explain how in situ testing data along with geotechnical computer modeling were used to design the net allowable bearing capacity for spread footings, and eliminate the need for more expensive foundations—such as mat slabs and deep foundations.

Following AASHTO design recommendations, civil engineering designs of shallow bridge foundations must change from allowable stress design (ASD) to load resistance factor design (LRFD) specifications regarding limit states concerning allowable bearing stresses and tolerable settlement magnitudes. Two LRFD criteria (limit state and service state) can be used to develop design charts of applied foundation stress (factored bearing capacity) versus footing effective width at various adopted settlement. In the presented methodology, the bearing capacity is evaluated using limit plasticity theory, settlement values are predicted using elastic continuum solutions, and geoparameter evaluations are based on site-specific data input using in situ field data from either standard penetration tests (SPT) or cone penetration tests (CPT). The focus is on shallow foundations resting on sands, granular soils, and geomaterials exhibiting drained behavior given the relatively small use of shallow foundations on clays for bridge structures in the U.S. since these should be dealt with on case-by-case basis because of additional concerns regarding time-rate-of-settlement, undrained distortion, creep, and other concerns. Two case studies are presented for comparing the in situ measured load-displacement curves with the LRFD recommended design values obtained using in situ tests.

Accurate compressibility parameters are required for the design of shallow foundations and calculation of building settlements. Current geotechnical practice uses conventional incremental loading (IL) consolidation tests to evaluate soil compressibility. Alternatively, constant rate of strain (CRS) consolidation tests can be used to study soil compressibility, significantly reducing testing time. In this test, excess pore water pressures are measured and continuous load-deformation data is obtained leading to a better definition of the yielding or past pressure of the material. However, laboratory estimation of the at-rest earth pressure coefficient, K₀, is only possible via K₀-consolidation tests in a triaxial cell (pseudo K₀-TX). This paper presents a critical review of the results obtained from pseudo K₀-TX, IL, and CRS tests conducted on overconsolidated Bootlegger Cove clay samples. The discussion is centered on the results of CRS tests performed under strain rates of 1, 10, and 20% per hour and their effects on compressibility soil parameters. The evolution of K₀-values and maximum shear modulus during pseudo K₀-TX testing is also presented. Trimming-induced disturbance was evaluated for all specimens. Sample quality for the K₀-TX tests was better than samples for IL and CRS testing. It was found that CRS testing accelerates the definition of compressibility parameters with respect to conventional IL tests, yielding very similar results. However, compressibility parameters based on pseudo K₀-TX tests are more representative of the in situ conditions.

A square and embedded shallow foundation was dynamically loaded via the T-Rex dynamic loading device. The measured responses of the footing indicated that a rigid body motion model for movement of the footing was appropriate. This rigid body model based upon a single-degree-of-freedom (SDOF), mass-spring-dashpot concept, employing a dynamic impedance function computed via a cone model, and using free-field shear wave velocity values measured at the site with surface wave tests, provided a good assessment of the dynamic response of the foundation under vertical excitation. Shear wave velocity values determined using an inversion process that best-fit matched the measured and predicted dynamic vertical displacements of the foundation revealed two interesting patterns relevant to the design of foundations for dynamic load: an effective softening of the soil/foundation contact throughout the footing embedment and a stiffening of the soil below the bottom of the footing.

Stability is one of the most important problems of soil mechanics related to the condition of excessive settlements. A reliability-based approach can be applied for designing shallow foundations for which their design needs knowledge about the distribution of settlement under a given footing is considered. The performance of geotechnical structures, including shallow foundations depends mostly on loads and soil properties that are the random variables described by statistical parameters. The objective of this study is to develop the methodology for risk analysis procedures of shallow foundations. This required the development of the reliability models that can be applied to shallow foundations and involved the establishment of serviceability limit state functions. Reliability is expressed in terms of reliability indices, which are calculated for total settlement of shallow bridge foundations. The most important part of this study is the development of statistical models for total settlements of shallow foundations on cohesionless soils by Monte Carlo simulations technique. The study verifies the most accurate settlement prediction methods for calculating immediate settlement of spread footings for each site by using compiled field data from research projects based on vertical settlements measured on 23 sites of footings for ten bridges in Northeast U.S. and two bridges in Ohio. Reliability indices are determined for settlement of the spread footings assigned in this study. CE Database subject headings: Reliability analysis; Shallow foundations; Immediate settlement; Cohesionless soils; Settlement prediction methods; Statistical parameters; Reliability index.

A new global segmentation technique, namely refined statistics-based method is proposed. X-ray computed tomography (CT) images of partially saturated granular geomaterials are segmented using this technique. Index properties of the geomaterials are quantified using the new technique and compared with those of the Otsu- and iterative-Otsu techniques. For the tested silica sand specimen, the new-technique-estimated void ratio and the degree of saturation were 0.67 and 39.35%. The estimates for the glass bead specimen yielded 0.64 and 43.49%, respectively. The true void ratio (0.66) and degree of saturation (37.71%) were determined with user controlled Image-Pro software package. It was found that the proposed method estimated the void ratio and the degree of saturation with 1.52 and 4.35% errors for the silica sand and with 15.63 and 0.34% errors for the glass bead, respectively. The computational time of the proposed method was found to be shorter than other methods considered. Overall, it is concluded that the proposed technique performed better in segmenting three-phase granular geomaterials.

Our infrastructure is expanding and the existing infrastructure is aging. Most structures are expensive to maintain and some occasionally fail. A large number of retaining walls, bridge abutments, dams, tunnels, and other geotechnical structures use pre-stressed ground anchors. Many existing structures require installation of pre-stressed anchors as an upgrade. Force monitoring of these anchors is crucial during construction and for long term behavior of structure. Among available instruments strain gauges, load cells, or fiber optics are pre-installed. Mounting of strain gauges and fiber optics are challenging. If load cells are used, it will require larger and deeper block-out to stress and accommodate the end cap. Most do not provide reliable data after few years in service. The most reliable method is to use elasto-magnetic sensor which does not require the sensor to be attached to the steel. They have been used successfully in over 80 projects. Sensors receive attention in terms of accuracy, performance, ease of installation, durability, and cost effectiveness. This paper describes its application in tie-back force monitoring, force transfer in bond zone, anchor force monitoring during excavation of rocks and tie force monitoring in tunnel construction.

During rock excavation by blasting, part of explosive energy is exhibited in the form of elastic waves. These waves travelling in all directions, give rise to ground vibrations, which in excess may cause damage to the nearby structures and rock strata. This phenomenon is of more concern for construction projects where parallel excavation and concreting activity is executed. Gulpur hydropower project is a 102MW project located on Poonch River in Kotli Azad and Jammu Kashmir, Pakistan. The constraint of time enforced the construction team to carry out blasting and concreting activity side by side. To ensure that both activities were carried out mutually in a safe and progressive manner, a site specific attenuation curve was established. A set of almost 50 excavation blasts were recorded with their explosive charge and induced vibrations at varying scaled distances. This data was developed into a relationship between Peak particle velocity and Scaled distance. The capacity of any concrete to sustain damage against vibrations readily varies with respect to its strength and internal composition, which in turn is dependent upon several factors, like mix design, placement and curing method, and age of concrete. Hence to ensure the safety of concrete structures against blasting, the age of the concrete at the time of blasting was chosen as to be the governing factor to establish the safe vibrations limit for a concrete structure. The attenuation curve along with established safe PPV limits for the different ages of concrete helped establish guidelines which ensured the safe and timely execution of blasting activity at Gulpur hydropower project without any critical damage to the concrete.

Surface soil erosion is a world-wide engineering and environmental problem. Accurate measurements of the erodibility coefficient and critical shear stress are needed for soil erosion models. Unfortunately, soil erosion testing to obtain these parameters is often highly variable. The surface roughness following an erosion test is used for calculating shear stress on the sample and the erosion rate is used to determine the erodibility coefficient. The objectives of this study were to apply a photogrammetric technique to measure the roughness of soil samples and to use turbidity sensors to measure the volume of soil eroded in the erosion tests. Laboratory Kaolin clay samples were prepared using a clay mixer and tested for erodibility using an erosion function apparatus. Two turbidity sensors were installed in the upstream and downstream of the flume to measure the amount of suspended soil particles during the erosion tests. After each test, two photos of each sample were taken using a digital camera and processed in a custom computational program. The results of this study showed that the stereophotogrammetry computational program was able to measure the surface roughness of the soil samples accurately. Additionally, the results from turbidity measurements provide a secondary measurement of erosion and can determine the volume of soil eroded during testing.

The failure of flood-control infrastructure, such as levees, due to a natural or manmade hazard can have significant repercussions, sometimes with dramatic and unanticipated consequences on human life, property, and the country’s economy. Thus, the integrity of a levee is an important issue that needs to be checked frequently. This can be achieved by long-term monitoring of the subsidence of the levee to identify potential weak sections and prioritize maintenance efforts. This paper presents the use of affordable sensing technologies, such as satellite-based interferometric synthetic aperture radar (InSAR), to monitor the settlement of the New Orleans area. Data from TerraSAR-X, the German Space Agency’s X-band satellite, was processed with the interferometric point target analysis technique in the gamma remote sensing software for widespread settlement monitoring. The time frame of the data is from 2009 to 2014. In situ measurements from GPS and extensometers are used to verify the remote sensing results, and a good agreement of displacement trends between the two methods was obtained. The favorable comparison increases confidence in the suitability of remote sensing techniques to monitor the long-term displacement of entire levee systems.

Fly ash is a fine powder produced in a huge amount from coal burning thermal power plants as a by-product. The main problems of countries which have coal burning power stations as sources of energy are a lack of dumping areas. This is due to saturation of the backyards of the utilities by the by-product. As a result, environmental problems related to the soil, water, and air contamination are created. The simple solution to this problem is utilization of fly ash as a potential backfill material for different geotechnical engineering applications. In this research, an attempt was made to study the feasibility of Class F fly ash as a backfill material and bamboo geogrid as a reinforcement. Therefore, a series of direct shear tests on unreinforced fly ash, modified direct shear tests on fly ash and bamboo geogrid, and permeability tests were performed in the laboratory. The molding water contents of the fly ash paste preparation were 10, 15, 20, 25, and 30% and the applied normal stresses were 50, 100, and 150 kilo Pascal (kPa). The results showed: (1) as moisture content increased, apparent cohesion developed and increased up to optimum moisture content, and decreased onwards. However, the angle of internal friction reduced marginally, hence, increasing of moisture content greatly altered the shear strength of the fly ash; (2) the permeability of the fly ash at 10% moisture content was found encouraging to creating better drainage conditions for reinforced retaining walls; and (3) the value of the interface friction coefficient between the fly ash and bamboo geogrid indicates the presence of a very good bonding between the two materials. As a result, the feasibility study suggests the fly ash and the bamboo geogrid used in this study to be a potential backfill and reinforcement materials respectively.

Generally, researchers consider sustainability and resiliency aspects of infrastructure projects independently, without considering the relationship that exists between them. Unified approaches that combine sustainability, resiliency, and analyze risk are very minimal. This paper proposes a unified approach to assessing sustainability, resiliency, and risk for infrastructure via evaluating the performance of a tailings dam under various earthquake magnitudes. A tailings dam is typically in operation for many years, which means they may have a direct impact on the local environment, society, and economy. Due to the extended life of the dam, the probability of a major event occurring that could negatively impact the durability of the dam increases. Hence, it is important to study impacts on the environment and economy under regular (sustainability analysis) and extreme (resiliency analysis) conditions in conjunction with their probabilities of occurrence. This paper studies the interrelationships between sustainability, resiliency and the potential risks of a negative impact upon infrastructure. Results provided show that a unified approach with emphasis on risk offers a more holistic, and accurate depiction of a system’s overall quality.

It has been reported that the Atlantic razor clam can burrow with an extremely high efficiency due to its well-evolved dynamic penetration kinematics. In general, the periodic penetration process is essentially an issue involving dynamic interaction between a shape-changing penetrator and the soil particles. In this paper, the three-dimensional discrete element method (DEM) modeling method was used to preliminarily study the influence zone created by body expansion. The real penetrator was simplified as a two-body structure: a conical foot and a cylindrical body with a time-varying radius. To mathematically visualize the influence zone at different expansion conditions, distributions of average normal contact force and particle displacement across the sample are investigated. Results show that the expansion ratio and expanding rate have significant impact on the influence zone. Furthermore, a low lateral resisting force and large influence zone can be achieved by using a low expansion ratio and expansion coefficient.

Technological advancements have facilitated improved testing techniques and instrumentation used by researchers to enhance and supplement classic analytical models for predicting vertical and horizontal earth pressures acting on foundations and earth retention structures. Ideally, soil pressure sensors would be tailored to the specific engineering application and comply with the stiffness of the structural system in which they are embedded. Sufficient surface area to avoid pressure localization, flush surface contact to minimize arching effects, and high resolution and data acquisition capabilities are desirable features. This paper presents details pertaining to the design, fabrication, and calibration of a new load cell based soil pressure sensor with a diameter of 10 cm, and a sample application of the sensor in a representative soil-structure interaction (SSI) contact situation. A brief overview of experimental test program will highlight passive pressure recordings on an abutment backwall due to static loading.

Measurement of aggregate base layer modulus is one of the most important quality control and quality assurance concerns of constructed pavements. However, existing in situ testing methods have several limitations in measuring layer modulus due to the limited depth of influence of test equipment and unknown stress states in the layer required in the modulus estimation or back-calculation. This paper will introduce a new approach to evaluate in situ horizontal stiffness and stress state of constructed aggregate layers by using shear wave transducers at any layer depth of sensor installation. A pair of bender elements is used as embedded shear wave transducers, which generate and detect the shear waves transferred through the aggregate material. The bender elements are mounted in a steel frame with a span to be embedded into an aggregate layer. After construction of aggregate layer and installation of the bender element system, shear waves are recorded according to a static load applied by a single tire. As the wheel load is applied on the surface above the bender element system, the shear modulus increases. Using the power relation between the shear wave velocity and mean effective stress established in laboratory test, the mean effective stress of local area in aggregate layer is estimated. The bender element system proposed in this study can be used for monitoring of in situ stiffness and stress in aggregate layer.