Journal of Geotechnical and Geoenvironmental Engineering

To investigate the behavior of laterally loaded piles within mechanically stabilized earth (MSE) walls, reduced-scale physical model tests of single piles within the MSE walls were conducted inside a test box. Sensors were installed in each model test to monitor the responses of the wall facing and the pile during the laterally loaded pile test. The test results show that the lateral capacity of the pile at the distance of two times pile diameter behind the wall facing decreased by 21% as compared with that at four times pile diameter. The model test results were compared well with those of the full-scale field tests. An empirical relationship was developed to estimate the pile-induced maximum wall facing displacements. This paper describes an additional lateral earth pressure distribution on the wall facing based on test results, which may be used to estimate the pile-induced maximum tensile forces in the geosynthetic layers at different elevations.

Tunneling-induced ground movements can affect the equilibrium state of an existing pile, causing uneven settlement among pile groups and damage to connected structures. This paper presents results from five centrifuge tests aimed at evaluating the load redistribution mechanisms that occur within piles located close to tunnel excavation. Two main mechanisms are studied: first, those related to ground displacements and stress relief related to tunneling and, second, those related to pile head load changes caused by connected superstructures (accomplished using a hybrid centrifuge-numerical modeling method). A novel fiber Bragg grating sensor system was used to measure shaft shear stresses along model piles. Results are used to quantify the relative impact that these two mechanisms have on pile load redistribution during tunnel volume loss. In addition, posttunneling pile loading tests were performed, with results indicating that tunneling-induced ground volumetric strains could influence the posttunneling loading response of piles.

Two analytical models for interpreting piezocone penetration tests (CPTUs) in soft sensitive Presumpscot clay were applied to in situ and laboratory results from a highway embankment project in Dover, New Hampshire. A closed-form limit plasticity solution provided the effective stress friction angle at both peak strength (${\varphi }_1^{\prime }$) and maximum obliquity (${\varphi }_2^{\prime }$) from the total cone resistance ($q_t$) and pore-water pressure ($u_2$) readings. A hybrid cavity expansion–critical state model provides undrained rigidity index ($I_R$), undrained shear strength ($s_u$), and four profiles of yield stress ratio (YSR) with depth. The interpreted CPTU results compared favorably with independent benchmark values obtained from field vane shear tests and laboratory index, triaxial compression, and consolidation tests. As a supplement to soil behavior charts, an alternate means of identifying sensitive clays from regular insensitive clays is presented.

This article presents numerical simulations investigating pore pressure buildup of a sand layer with a free drainage boundary at the top under both low and high overburden pressures and subjected to earthquake base excitation. The numerical runs simulate two centrifuge experiments previously conducted and reported. In these tests, a 5-m layer of clean Ottawa sand with relative density $D_r=45\%$ was tested under overburden pressures of ∼100 and ∼600 kPa (1 and 6 atm). The simulations were performed using Dmod2000, a nonlinear effective stress numerical one-dimensional (1D) site response analysis code. The tests revealed that the response was partially drained rather than undrained, with much more partial drainage at ∼600 kPa (6 atm) compared to ∼100 kPa (1 atm). The simulations correctly modeled this behavior, with very good agreement between simulated and measured centrifuge excess pore pressures. A key aspect of this good accord in the simulations was the correct selection in the simulations of the 1D drained volumetric stiffness of the sand, $M^{\prime }=1/m_v$, because the coefficient of consolidation, $c_v$, is proportional to $M^{\prime }$. Both $c_v$ and $M^{\prime }$ were 2.5–3 times greater at ∼600 kPa (6 atm) than at ∼100 kPa (1 atm) in both centrifuge tests and simulations. Any future simulation of pore pressure response of sand under field drainage conditions needs to consider this large increase in volumetric stiffness at high overburden pressure. Good agreement was found between values of $M^{\prime }$ back-calculated from the centrifuge tests and from a consolidometer test on a different sand reported in the literature. The value of $M^{\prime }$ seems to increase approximately with the root square of the overburden pressure, and future simulations for high overburden and realistic field drainage conditions should account for this increase. The proper high-pressure correction factor, $K_{\sigma }$, to be used in conjunction with liquefaction charts may be higher than 1 for some realistic field drainage conditions due to this substantial decrease of sand compressibility under high overburden pressure.

Organic contaminant diffusion through a novel multilayer coextruded vapor barrier is examined for benzene, toluene, ethylbenzene, xylenes (BTEX), trichloroethylene (TCE), and tetrachloroethylene (PCE). The vapor barrier considered is composed of five materials: linear low-density polyethylene (LLDPE), high-density polyethylene (HDPE), ethylene vinyl alcohol (EVOH), a tie layer (TL), and a degradation layer (DL). Parameters for the LLDPE, HDPE, TL, and DL are developed using material-specific diffusion tests. Contaminant-specific permeation coefficients ($P_g$) for these materials range from 1.4 to $9.2\times {10}^{-11}{\mathrm{m}}^2/\mathrm{s}$. The diffusion parameters of the EVOH are inferred from testing of a thin (0.0889-mm) coextruded LLDPE/TL/EVOH/TL/EVOH membrane, and the contaminant specific $P_g$ values range from 1.9 to $7.0\times {10}^{-14}{\mathrm{m}}^2/\mathrm{s}$. These individual layer parameters are used to develop a single set of parameters for each contaminant for the entire vapor barrier, with overall contaminant specific $P_g$ values of $2.7-13.8\times {10}^{-13}{\mathrm{m}}^2/\mathrm{s}$. The parameters are used to model various vapor intrusion scenarios which show that the multilayer vapor barrier results in significant predicted decreases in airspace concentrations compared to HDPE or no barrier.

Rock-socketed piles are foundational elements designed to transmit large concentrated loads to stronger materials located at greater depths. The rock-socket side shear resistance is commonly estimated using empirical criteria as a percentage of the rock or concrete uniaxial compressive strength. However, this approach neglects the influence of other important aspects, such as the roughness of the pile-socket interface. In this work, numerical discrete-element models of rock-socketed piles with different degrees of socket roughness are employed to estimate the influence of the socket roughness on the load-settlement response and on the side shear resistance. The numerical simulation results are compared with predictions obtained using empirical correlations based on load test results and proposed by other authors. Results indicate that the discrete-element method is suitable to reproduce rock-socket pile behavior considering socket roughness; they also suggest that sockets drilled with standard tools in soft to medium rock tend to be relatively smooth unless artificially roughened with special tools and that damage to the interface asperities becomes more relevant after socket settlement of about 1% of the socket diameter, especially for rougher piles.

In North America, temperatures nearing 100°C have been reported in several municipal solid waste landfills. However, the temporal and spatial-dependent processes that result in excessive heat accumulation are not well understood. The objective of this study was to develop a transient finite-element three-dimensional model that incorporates gas-liquid-heat reactive transfer in a landfill with biotic and abiotic reactions and spatially dependent heat transfer processes to better understand heat generation, accumulation, and propagation. The model incorporates gas-liquid-heat reactive transfer with aerobic and anaerobic biological reactions, anaerobic metal corrosion, and ash hydration and carbonation. Increasing boundary temperature, biological reaction rates, and landfill height increase the maximum temperature in the central region of a landfill, whereas the impact of thermal properties of municipal solid waste (MSW) is small. Simulation results predict that placement of ash near the corner of a landfill reduces the size of the elevated temperature region relative to placement in the landfill center. Mixing heat-generating wastes (ash or Al) with MSW decreases maximum temperatures but results in elevated temperatures over a larger fraction of the landfill volume relative to segregated ash disposal.

A numerical model, called HT1, is presented for one-dimensional (1D) heat transfer in saturated incompressible layered soil with effective porosity and steady fluid flow. The model uses a series-parallel approach for heat transfer and accounts for advection, conduction, and thermal mechanical dispersion assuming local thermal equilibrium between solid and fluid phases. The key to HT1 is the definition of separate columns for the solid matrix and mobile pore fluid. The solid matrix column includes the solid phase and immobile pore fluid and consists of fixed elements. The mobile pore fluid column uses Lagrangian element-tracking to follow the fluid motion, which reduces numerical dispersion and simplifies heat transfer to that of dispersive flux between contiguous elements. Development of the HT1 model is first presented, followed by verification checks using available analytical and numerical solutions. Simulation results for several numeric examples are used to demonstrate model performance and the effects of various parameters, including effective porosity and multiple soil layers, on heat transfer behavior for saturated incompressible soil.

Near-surface soils in geotechnical and geoenvironmental applications are often unsaturated, and natural or imposed changes in temperature may lead to a softening effect at constant suction that causes a change in stiffness. To capture thermal effects on the stiffness of unsaturated soils, this paper presents an effective stress-based, temperature-dependent model for the small-strain shear modulus of unsaturated soils, with an emphasis on silts. The temperature dependency of the model was accounted for by employing temperature-dependent functions for matric suction and effective saturation characterized using the soil–water retention curve. To validate the proposed model, laboratory tests using a modified triaxial apparatus with bender elements were carried out on Bonny silt to measure the small-strain shear modulus at 23°C and 43°C for varying matric suctions of 0–110 kPa. The results from the proposed model were in a reasonable agreement with the experimentally measured values and demonstrate the importance of considering temperature effects on the shear modulus of unsaturated soils. The accuracy of the model was further validated by comparing the predicted values with laboratory test results on silts reported by two independent studies in the literature.

Glacial tills are widespread across North America, northern and central Asia, and northern Europe, where they are also found under the Baltic, North, and Norwegian Seas. Their geological and geotechnical characterization is important to a wide range of onshore and offshore engineering projects. One aspect of tills on which little has been reported is their mechanical anisotropy. This paper reports coordinated hollow cylinder apparatus (HCA) tests, triaxial shearing, and small-strain stress probing experiments, supported by index testing, on high-quality samples of natural low-to-medium plasticity, high overconsolidation ratios (OCR) stiff clay-till from the Bolders Bank Formation at Cowden, near Hull in the UK. Material variability and sampling bias are inevitably introduced by the till’s erratic gravel particles and fissure systems, and these aspects are addressed carefully. The experiments investigated the till’s stiffness and shear strength anisotropy from its limited linear elastic range up to ultimate failure, showing that stiffnesses are higher in the horizontal direction than in the vertical and that higher undrained shear strengths develop under passive horizontal loading than active vertical loading. Comparisons are made between the till’s patterns of anisotropy and those applying to previously studied sediments, and reference is made to in situ stiffness measurements. The important implications of anisotropic behavior for geotechnical design and the interpretation of field tests are emphasized.

A large-scale liquefaction testing program was carried out on a 10-t shake table to better unite lab and field measurements before, during, and after seismic soil liquefaction. The objectives of this research include cone penetration test (CPT) and shear-wave velocity V_s measurements before and after liquefaction, observation of void ratio redistribution due to liquefaction, measurements of residual strength during liquefaction, measurements of postliquefaction volumetric and shear strains, and measurements of ejecta due to liquefaction. A large cylindrical simple shear container was developed that is roughly 1.5 m tall by 2.3 m diameter to test a $6.4\text{-}{\mathrm{m}}^3$ sample of water-pluviated Monterey sand in a series of tests. The sample was excited using a sine wave at its resonant frequency to trigger and maintain liquefaction over 15 s of loading. Vertical arrays containing accelerometers and pore pressure transducers were arranged throughout the sample. Cone penetration and shear-wave velocity tests were performed before and after liquefaction. During liquefaction, T-bar measurements along with acceleration and pore pressure measurements were acquired. Void ratio redistribution was observed as inferred from changes in the measured preliquefaction and postliquefaction CPT tip resistance with depth. Volumetric strains and shear strains were observed and measured using displacement transducers. Ejecta volume that was expelled from the top of the container was observed and quantified. The liquefied residual strength was measured using the T-bar test. A summary of the results and how these relate to the broader field of liquefaction engineering are presented.

Adaptation to climate change requires careful evaluation of infrastructure performance under future climatic extremes. This study demonstrates how a multidisciplinary approach integrating geotechnical engineering, hydrology, and climate science can be employed to quantify site-specific impacts of climate change on geotechnical infrastructure. Specifically, this paper quantifies the effects of changes in future streamflow on the performance of an earthen levee in Sacramento, California, considering multiple modes of failure. The streamflows for historical (1950–2000) and projected (2049–2099) scenarios with different recurrence intervals were derived from routed hydrological simulations driven by bias-corrected global climate models. The historical and future flood levels were then applied in a set of transient coupled finite-element seepage and limit equilibrium slope stability analyses to simulate the levee subjected to extreme streamflow. Variability in hydraulic and mechanical properties of soils was addressed using a Monte Carlo sampling method to evaluate and compare the probability of failure of the levee under different historical and future climate scenarios. Three individual modes (underseepage, uplift, and slope stability) along with lower and upper bounds for the combined mode of failure were examined. The results showed that incorporating future floods into levee failure analysis led to considerable reductions in the mean factor of safety and increases in the levee’s probability of failure, suggesting that risk assessment based on historical records can significantly underestimate the levee’s failure probability in a warming climate. Despite inherent uncertainties in future projections and substantial variability across climate models, evaluating infrastructure against projected extremes offers insights into their likely performance for the future.

This paper presents pull-out capacity and creep behavior of a model helical pile and a model grouted shaft helical pile installed in frozen ice-rich silt in Gloucester, Ontario, Canada. The measured pull-out capacity of the model piles was compared to predicted capacities calculated using modified forms of previously published theoretical approaches based on the individual bearing model (IBM) and the cylindrical shear model (CSM). The modified IBM adequately captured the pull-out loading resistance of the helical pile; however, neither the modified IBM nor CSM could accurately predict the measured capacity of the grouted shaft helical pile in frozen ground. The creep behavior of the test piles in frozen soil was dependent on the applied creep stress and the frozen ground temperature. The pile creep rates increased when the ground exposure temperature increased, even under a constant creep loading condition. The pile creep rates measured in the current study were smaller compared to previously published results for similar stress and thermal boundary conditions. This could be attributed to creep rate hysteresis associated with ground warming, as well as the differences in the helix diameter. An improved graphical solution was also produced to predict creep rates for single-helix helical piles in frozen ground at various exposure temperatures.

Design of column-supported embankments (CSE) requires the evaluation of global stability using the conventional limit equilibrium method (LEM). Yet, for CSEs using unreinforced concrete columns and load transferring geogrids, the failure mechanisms and corresponding soil-structure interactions are not well understood. There is increasing evidence pointing to large bending moments in columns and failure of columns in flexure, as opposed to a failure by shear as assumed in limit equilibrium analyses. In response to these design uncertainties, the failure height, failure mode, and deformations of eight column-supported embankment scenarios were investigated using three-dimensional (3D) numerical analyses. For the same embankment scenarios at failure height, factors of safety (FS) were then calculated using the two-dimensional (2D) LEM for investigating its applicability in evaluating global stability of CSEs. The 3D numerical analyses examined CSE stability for the limiting conditions at undrained end-of-construction and after long-term dissipation of excess pore water pressures. The numerical model included representations of flexural tensile failure in the concrete columns and tensile failure in the geosynthetic reinforcement. Scenarios consisted of a base case with typical concrete column design, five single-parameter variations using base case conditions, and two multiparameter variations using base case conditions. The undrained condition was the most critical, and two failure modes were found: (1) multisurface shearing in the embankment coupled with bending failure of columns and near-circular shear failure in the clay, and (2) multisurface shearing in the embankment coupled with bending failure of columns and shearing in the upper portion of the soft foundation clay. Both failure modes were accompanied by a rupture of the geosynthetic when included in the load transfer platform. Soil-column interactions were complex, and many columns failed in bending at lower embankment heights than those that produced collapse. The factors of safety calculated using the LEM were overstated. This is because the LEM assumes failure by shear, which has limited applicability for examining the complex mechanisms by which CSEs fail. The practical implication is that the LEM should not be used for evaluating global stability of this system type and, by extension, other system types in which soil-structure interactions result in failures controlled by mechanisms other than shear.

The predicted severity of liquefaction manifested at the ground surface is a popular and pragmatic proxy of damage potential for infrastructure. Toward this end, the liquefaction potential index ($LPI$) and similar models are commonly used, and often codified, to predict surface manifestations on level ground. These predictions typically use deterministic thresholds from the literature—obtained via calibration on case-history data—to classify the expected manifestation. While widely adopted, such thresholds obscure the uncertainty of expected outcomes and are incompatible with probabilistic frameworks. Proposed thresholds are also intimately tied to the liquefaction analytics used to compute them and to the methodology used to select them, each of which can conflict with forward applications, leading to erroneous predictions. Accordingly, using 15,223 case histories from 24 earthquakes, this study develops fragility functions that probabilistically predict surficial manifestations of liquefaction using triggering and manifestation models popular in practice. Deterministic workflows are easily extended by selecting appropriate fragility coefficients; options are provided for six cone penetration test (CPT)–based triggering models, one CPT-inversion filter, three manifestation models, and three manifestation severities. The model application is demonstrated by predicting (1) liquefaction manifestations in Christchurch, New Zealand, resulting from an Alpine Fault earthquake, wherein a logic-tree is used to ensemble predictions from 18 models, and (2) the return period of liquefaction manifestations in the South-of-Downtown (SODO) district of Seattle, wherein predictions are compared to historical observations.

Observations of the performance of coastal and marine structures in weather events that produce standing and/or progressive waves have pointed to liquefaction of the seabed as a contributing cause of damage. The cyclic response of marine sediments under wave loading can serve to improve the understanding of seabed liquefaction triggering and its consequences. This paper presents the results of an experimental study of the cyclic behavior of loose isotropically and anisotropically consolidated calcareous sand under elliptical stress paths representing progressive waves. Various ratios, $\lambda$, of the axial stress difference and torsional shear stress amplitudes were investigated in a hollow-cylinder torsional shear apparatus. The results indicate that the failure mode of isotropically and anisotropically consolidated (IC and AC, respectively) specimens are cyclic mobility and residual deformation failure, respectively. The difference in the observed failure mode appears to be related to particle shape and is independent of $\lambda$. However, the cyclic resistance of the calcareous sand is strongly influenced by $\lambda$ and increases with decreasing consolidation stress ratio, $K_c$. The cyclic resistance of IC specimens is relatively independent of the orientation of elliptical stress paths, whereas the AC specimens exhibited a marked dependence. The terminal peak excess pore pressure ratio, $r_{u,\mathit{t}}$, and shear work required for cyclic failure, $W_f$, are independent of $\lambda$; however, $r_{u,\mathit{t}}$ and $W_f$ increases with increasing and decreasing $K_c$, respectively. Moreover, the relationship between the normalized peak excess pore pressure ratio and normalized shear work is related to the type of soil, but is independent of $\lambda$ and $K_c$.

The three principal methods specifically developed for the design of rock socketed piles were originally presented in the 1980s. One of the methods is an empirical technique based on the normalized performance of many full-scale pile tests while the other two are based on numerical and analytical techniques. However, there appears to be no detailed assessment of how well each method can predict the performance of piles socketed into rock. This paper discusses the three methods and then compares their predictions for load-settlement with the results of several foundation load tests particularly referencing settlements that might be acceptable for serviceability. It is demonstrated that while all three methods can produce reasonable predictions of performance, one of them tends to overpredict performance while the other two appear to underpredict performance. Only one of the methods produces load-settlement curves that bear a reasonable similarity to the expected shape of actual load-settlement curves.

This paper describes the application of unsaturated soil mechanics to an interstate connecting-ramp embankment that failed during construction. Specifically, matric suction is incorporated into the calculation of the tension crack (TC) depth induced by desiccation and strain incompatibility and the contribution of matric suction to embankment shear strength. The results are compared with field observations to assess the viability of unsaturated soil mechanics in modeling compacted embankments in stability analyses. Results from this study suggest that using unsaturated shear strength parameters while introducing a TC in the compacted fill yields a reasonable inverse analysis of this interstate embankment. This may be preferred in slope stability analyses to the current practice of using an undrained shear strength (i.e., cohesion) for the unsaturated compacted fill and including a TC to generate a reasonable factor of safety.

The FieldSed is an inexpensive portable device for performing an image-based soil particle size analysis. The process, which includes the image analysis, is referred to as SedImaging (short for sediment imaging). The FieldSed was used for an investigation of Kalamazoo River sediments to generate over 100 particle size distributions (PSDs). Core samples taken from the river were tested in a nearby field lab. When necessary, samples were processed prior to testing in the FieldSed to remove particles greater than 2.0 mm and those finer than 0.075 mm. Doing so was necessary to ensure the efficiency of the current SedImaging method. A small number of specimens was selected for quality control testing to determine the reproducibility of SedImaging results. This testing also involved sieve analyses in ascertaining the agreement between SedImaging and sieving results. The control test results presented in this paper demonstrate that the FieldSed is a promising device that can rapidly, accurately, and repeatedly determine particle size distributions in field labs for geotechnical and geoenvironmental applications.

The article presents a three-dimensional (3D) finite element (FE) model of the groundwater flow beneath a river embankment, aimed at developing a simple and reliable numerical strategy for the identification of hydraulic conditions that cause the reactivation of sand boils in flood defense systems prone to recurrent backward erosion piping. The seepage model is calibrated on a cross section of the Po River, where a large natural sand boil has been periodically observed during past high-water events. Monitored river water levels, piezometric measurements, and geotechnical testing data have been used for the calibration study. The numerical analysis proposes a suitable way to simulate a preexisting eroded zone, identifies the key parameters to be collected in the field, and discusses the criteria for the assessment of piping reactivation. The sensitivity analysis proposed herein enables one to identify the set of model parameters capable of capturing field evidence.

The residual strength of liquefied soil ($s_{u,r}$) is a large-strain strength variable often used for forecasting the seismic stability of dams, embankments, and mine tailings. This variable is usually arrived at by back-analysis of failure case histories and through laboratory experiments. Over the last few decades, there has been debate about whether the liquefied strength should be normalized by the prefailure vertical effective stress (${\sigma }_v^{\prime }$). Normalizing a variable is usually done for two reasons; (1) to render the variable dimensionless, and/or (2) to improve the relationship between the independent and dependent variables. The first objective has obvious benefits for engineering practice in the United States, where two unit systems are commonly used. For the second objective, the benefits of normalizing can be measured by the reduced uncertainty in the statistical relationship. In this study, it is shown that normalizing the residual strength by the prefailure vertical effective stress ($s_{u,r}/{\sigma }_v^{\prime }$) increases the scatter and uncertainty in the relationship between blow count and residual strength for flow failures. This increase in scatter means that the process of normalizing generates additional uncertainty, thereby making the statistical relationship more ambiguous (measured using R-squared and mean squared error). However, for lateral spreads, the opposite is true, and normalizing the liquefied strength reduces uncertainty and improves predictive power. The differences between the two types of seismic soil failures from a critical state perspective, and how these relate to the prefailure vertical effective stress conditions, are discussed.

Coordination number (CN) is a fundamental microscale variable in soils affecting the macroscale parameters of the material such as porosity, stiffness under loading, and stability under hydraulic gradients. However, most studies on CN have focused on sphere or ellipsoid packings using the discrete element method (DEM). By means of computed tomography (CT) and image-processing techniques, this work rigorously computes the three-dimensional (3D) sphericity and roundness of each grain in five sands and investigates the impact of particle shape on CN. The results show that the average coordination number ($C{N}_{\mathrm{ave}}$) of different sands and the CN of grains within a given sand may be impacted differently by particle shape. For a given equivalent diameter of a given sand, more irregular grain packings show a subtle higher CN, and this change in CN increases with increasing grain size. However, air-pluviated irregular particle packings with poor gradation may exhibit lower average $C{N}_{\mathrm{ave}}$ because of particle orientational alignment, particle interlocking, and surface roughness.

This technical paper investigates the bearing performance of precast concrete piles embedded within calcareous sands with biogrouting at the pile toe. Loading tests of biogrout-improved and unimproved concrete model piles were conducted to evaluate the performance of biogrout to enhance the toe bearing capacity of precast concrete piles. The total bearing capacity of the precast concrete pile with a biogrouted toe was 4.4 times as large as that without biogrout. A series of index tests were performed using a penetrometer to estimate the spatial distribution of strength of biocemented sands below the pile toe. It was found that the average strength of the biocemented sand below the biogrouted pile toe gradually decreased with increasing vertical distance or lateral distance from the pile toe. The novel application of biocement to treat bearing sands following pile installation represents a promising method to increase pile capacity.