Journal of Geotechnical and Geoenvironmental Engineering

In this research, a numerical investigation was conducted to study the effects of backfill constitutive behavior on the vertical and horizontal deformations of geosynthetic-reinforced soil (GRS) piers under static axial loads. A finite-difference program was used to model full-scale GRS piers. The backfill soil was simulated using three constitutive models: the elastic-perfectly-plastic Mohr-Coulomb model, the plastic-hardening model, and the plastic-hardening model combined with strain-softening behavior. The results showed that the deformation response of GRS piers under service loads is satisfactorily predicted by the plastic-hardening model. At ultimate failure loads, however, only the model accounting for the plastic-hardening and the strain-softening behaviors was judged to reasonably capture the behavior of GRS piers. The relative displacement of soil and geotextile at the soil–geotextile interface was also investigated. The results showed that under working conditions with small applied load, there is no sliding between the soil and geotextile; however, as the load increases, sliding is first initiated at the corners of the pier and progressively mobilized toward the center of the pier. A parametric study on the effects of soil–geotextile interface properties on the deformation behavior of GRS piers under axial loading was also conducted using the validated plastic-hardening model combined with strain-softening behavior. It was found that increasing the interface friction angle decreases the settlement of GRS piers when the axial strain is greater than 2% for piers with a concrete masonry unit (CMU) facing and 4% for piers without CMU facing. The results suggest that when calibrating the interface friction angle (or cohesion), the postyielding response of GRS pier should be used.

Dense granular columns (DGCs) are generally known to mitigate the liquefaction hazard through a combination of (1) installation-induced ground densification, (2) enhanced drainage, and (3) shear reinforcement. However, the relative contribution of these mitigation mechanisms remains poorly understood. A recent case history of successful embankment performance on a liquefiable site treated with DGCs that had relatively low area replacement ratios ($A_r$) (where drainage is not notably enhanced) suggested that shear reinforcement and installation-induced ground densification may be the two dominant mitigation mechanisms provided by DGCs. In this paper, we present a series of four dynamic centrifuge experiments designed and conducted to test this hypothesis under controlled conditions. Consistent with case history observations and supporting our initial working hypothesis, densification combined with shear reinforcement was shown to be primarily responsible for limiting the embankment’s seismic deformations. Additional drainage led to minor improvements in terms of embankment settlement, while increasing its permanent lateral displacement. The results suggest that the combined effects of $A_r$ and ratio of maximum shear modulus of the DGCs to that of the surrounding soil ($G_r$) can play a key role in the distribution of stress between DGCs and soil prior to shaking and the extent of softening and strain accumulation in various layers during shaking. For example, it was observed that densification of the liquefiable sand layer around DGCs shifted the generation of larger excess pore pressures to greater depths compared to the DGC-treated test without densification. This led to a base isolation effect that reduced accelerations, degree of softening, and accumulation of shear and volumetric strains at shallower depths, producing a notably improved performance for the soil–embankment system even when the DGC’s drainage capacity was inhibited. These observations were attributed to the reinforcement effect of DGCs, the simultaneous reduction in $G_r$ due to densification, and a more even transfer of the embankment load onto the soil–column matrix, increasing the stiffness and strength and reducing shear strains in the shallower and looser layer. The presented experimental results point to the importance of accounting for pre- and postinstallation soil density and stiffness in relation to DGCs, confining pressure distributions, kinematic constraints, and activity of various mitigation mechanisms when evaluating the potential influence of DGCs on seismic demand, liquefaction triggering, and deformations near embankment structures.

Estimation of Newmark sliding displacement plays an important role for evaluating seismic stability of slopes. Current empirical models generally utilize predefined functional forms and relatively large model uncertainty is involved. On the other hand, machine learning method typically has superior capacity in processing comprehensive data sets in a nonparametric way. In this study, a machine learning framework is proposed to predict Newmark sliding displacements using the extreme gradient boosting model (XGBoost) and the Next Generation Attenuation (NGA)-West2 database, where the subset simulation (SS) is coupled with the $K$-fold cross validation (CV) technique for the first time to tune hyperparameters of the XGBoost model. The framework can achieve excellent generalization capability in predicting displacements and prevent data overfitting by using optimized hyperparameters. The developed data-driven Newmark displacement models can better satisfy both sufficiency and efficiency criteria, and produce considerably smaller standard deviations compared with traditional empirical models. Application of the models in probabilistic seismic slope displacement hazard analysis is also demonstrated. The proposed SS-XGBoost framework has great potential in developing data-driven prediction models for a wide range of engineering applications.

Track degradation and defects of existing passenger and freight mixed railroads are concentrated in bridge–embankment transition zones. Heavy axle load (HAL) operation on existing railroads presents a complexity in evaluating the evolution of the differential settlement of the overloaded ballasted track, especially in bridge–embankment transition zones. In this paper, an iterative prediction methodology of track differential settlement in transition zones is developed. In this methodology, the history of the loading on the ballast and the history of the loading on the subgrade are considered as well as the vehicle–track interactions. The sleeper–ballast contact forces and the subgrade soil deviator stress field change with iterations. A case study was analyzed to investigate the track differential settlement in a bridge–embankment transition zone of an overloaded passenger and freight mixed line. The distribution of the sleeper–ballast contact forces along the track and the distribution of the subgrade soil deviator stress were calculated with a vehicle–track–subgrade model. Results indicate that the critical axle load of the vehicle for existing ballasted track transition zones without any reinforcement treatment is 27 t. Because HAL vehicles may have axle loads up to 39 t, the increase of the train axle load, reinforcement treatments, and remediations are required for existing transition zones. The maintenance scheduling for tracks under different axle loads was calculated.

Two of the most important parameters in any dynamic analysis involving soils are the shear modulus and damping ratio. Based on lab tests on gravels from 18 investigations, simplified equations to define $G/G_{\max }$ and the damping ratio as a function of shear strain, $\gamma$, have been developed. The $G/G_{\max }$ versus $\gamma$ equations rely on two parameters that can be defined in terms of confining pressure and uniformity coefficient. Increasing confining pressure leads to a more linear curve, while increasing the uniformity coefficient leads to a more nonlinear curve shape. $G/G_{\max }$ versus $\gamma$ curves for gravels tend to plot somewhat below curves for sands under similar conditions. Estimates of the standard deviation in $G/G_{\max }$ versus $\gamma$ curves are provided to consider scatter about the mean. The damping ratio versus $\gamma$ equation employs the modified Masing approach with a minimum damping ratio of 1%. In addition, about 67% of the damping data points fall within an error band of $\pm 33\%$ from the computed value. The damping ratio of gravel specimens also decreases as the confining pressure increases, whereas it increases for higher uniformity coefficients. Other direct correlations between damping ratio and factors such as shear strain, uniformity coefficient, and confining pressure did not provide significant improvements in predictive capacity.

Given that municipal solid waste (MSW) in landfills can reach temperatures greater than 50°C that may be sustained for several decades due to methanogenic bacteria activity, the generated heat is an alternative energy source that can be exploited for direct heating of nearby infrastructure or for augmenting industrial processes. However, in situ measurements of MSW thermal properties are needed to properly design heat extraction systems for landfills. In this study, the spatial and temporal evolution of the waste temperatures in a new MSW landfill cell in Santee, California, were monitored over 13 months. After the temperatures reached stable values, a 17-day heat extraction thermal response test was performed on serpentine geothermal heat exchangers that were installed at three elevations in the cell during waste placement. Because the serpentine segments were separated from each other to minimize thermal interference during the heat extraction test, the pipes were assumed to represent line heat sinks. The values of effective thermal conductivity estimated from infinite line source analyses ranged from 0.86 to $1.32\mathrm{W}/\mathrm{m}°\mathrm{C}$, which are consistent with values on the higher range of those from laboratory tests on MSW.

This paper describes large deformation finite element (LDFE) analysis of the penetration of the T-bar penetrometer in uniform clay, identifying soil flow mechanisms around the T-bar, the extent of any cavity above the T-bar and the evolving penetration resistance profile. A trapped cavity above the advancing T-bar penetrometer and its influence on the corresponding bearing capacity factor are the crucial findings of this paper. The formation and evolution of the trapped cavity mechanism are studied extensively, exploring a large range of normalized undrained shear strength of soil and surface roughness of the T-bar. It is shown that the depths of forming a trapped cavity and being fully filled with soil increase with increasing normalized undrained shear strength of soil and roughness of the T-bar. The trapped cavity results in a reduction (up to 13%) in the commonly used bearing capacity factors based on plasticity solutions and a flow-round failure mechanism. According to the depth span of an existing trapped cavity, there are three scenarios: (1) for clay deposits with $s_{\mathrm{u}}/{\gamma }^{\prime }D\le 1$, a shallow failure mechanism is directly followed by a flow-round mechanism since the trapped cavity span is negligible; (2) for clay deposits with $1<s_{\mathrm{u}}/{\gamma }^{\prime }D\le 8.3$, all three stages—shallow failure mechanism, trapped cavity mechanism, and flow-round mechanism—can be observed; and (3) for clay deposits with $s_{\mathrm{u}}/{\gamma }^{\prime }D>8.3$, the trapped cavity is not fully closed up to a penetration of $30D$, leading to a lower bearing capacity factor profile compared to the stabilized factors for the other two scenarios. A systematic interpretation procedure is therefore proposed to account for the effect of a trapped cavity for more accurate interpretation of soil undrained shear strength from the T-bar penetration resistance.

Energy pile groups generally show different behavior than single energy piles because of the presence of rafts and the thermomechanical interaction between piles. This paper presents the results from a series of full-scale field tests to investigate the thermomechanical behavior of an energy pile–raft foundation. The energy pile group was nonsymmetrically operated to analyze the thermally induced group effects. A nonuniform temperature increase may induce a significant change in the distributions of the thermal stress and mobilized shaft resistance. This paper demonstrates that group effects between energy piles can trigger effects in the pile-raft foundation. The nonsymmetrical thermal loading induces a differential displacement in the foundation. When the number of operating piles increases, a lower thermal stress develops along the operating pile and the differential displacement decreases. In addition, because of the indirect heating of the surrounding piles, the differential displacement will continuously decrease during long-term operation, and the thermal stress on the surrounding, nonoperating piles gradually becomes crucial.

Pile foundations supporting offshore structures, such as jacket platforms and wind turbines, are subjected to cyclic lateral loading. The capacity and deformation of these pile foundations under cyclic lateral loading are important and challenging design aspects. This paper presents the results of a series of four lateral load pile tests in an overconsolidated clay at the Haga site and their back-analysis using a $p\text{-}y$ framework based on fundamental soil behavior measured in the laboratory at the element level. This framework can account for site-specific cyclic soil properties, summarized in classic contour diagrams, and site-specific cyclic loading characteristics in design. The paper first provides a summary of the framework and outlines the important assumptions and calculation procedures. It then presents a detailed description of the test setup and soil conditions. The pile load test results and the back-analysis are subsequently presented. Generally, a good match between the test results and the model predictions was observed, demonstrating the model’s capability to capture the essential behavior of pile foundations under monotonic and cyclic lateral loading.

Design- and construction-related factors that affect leakage through geomembranes, used either alone or in a composite liner, are examined. The development, detection, and number of holes that can develop during construction and operation of a facility are discussed. The relationship between leakage through holes in a geomembrane, and the hydraulic conductivity of the material above (including tailings) and below a geomembrane, is examined, considering both a relatively permeable subgrade and an underlying clay liner (including the unstressed zone beneath a wrinkle) in a composite liner. The leakage observed in the primary liners of 180 landfill cells is explained by holes in geomembrane wrinkles with a length consistent with those observed in the field and an appropriate choice of hydraulic conductivity for the clay liner below the geomembrane wrinkle with a hole. Leakage through geosynthetic clay liner (GCL) overlaps below wrinkles is examined. The latest research into the physical and chemical aging of high-density polyethylene (HDPE) geomembranes liners is discussed in the context of the compatibility of the antioxidant package and resin with the solution to be retained, liner temperature, nature of exposure, sustained tensile strains, and welds. The estimation of the service life of a geomembrane based on immersion tests and simulated field conditions is examined in terms of antioxidant depletion, stress cracking, and the maximum allowable strain in a geomembrane. It is projected that the service life of a geomembrane may range from just a few years to many centuries.

This paper reports the use of optical fiber Bragg-grating (FBG) sensors to monitor the stress waves generated below ground during pile driving, combined with measurements using conventional pile driving analyzer (PDA) sensors mounted at the pile head. Fourteen tubular steel piles with a diameter of 508 mm and embedded length-to-diameter ratios of $6:20$ were impact driven at an established chalk test site in Kent, United Kingdom. The pile shafts were instrumented with multiple FBG strain gauges and pile head PDA sensors, which monitored the piles’ responses under each hammer blow. A high-frequency (5 kHz) fiber optic interrogator allowed a previously unseen resolution of the stress wave propagation along the pile. Estimates of the base soil resistances to driving and distributions of shaft shear resistances were found through signal matching that compared the time series of pile head PDA measurements and FBG strains measured below the ground surface. Numerical solutions of the one-dimensional wave equation were optimized by taking account of the data from multiple FBG gauges, leading to significant advantages that have potential for widespread application in cases where high-resolution strain measurements are made.

Statistical design of experiments was combined with coupled and uncoupled pile-reinforced slope stability analyses to draw conclusions about the factor of safety (FS) sensitivity to pile-related properties (pile location, spacing, embedment depth, and diameter), and to analyze differences between analytical techniques and space dimensionality. This evaluation performed two- and three-dimensional, limit equilibrium (LE), and finite-element (FE) analyses in a fully randomized block design, a definitive screening design, and a central composite design fashion. Pile location, embedment depth, and spacing had significant effects on FS. The optimum pile location is not fixed, and varies not only with changes in soil strength but also with variations in geometry properties because of the presence of interactions among the factors. The comparative analysis found no statistically significant difference between the studied methods. However, the confidence intervals indicated FS differences as high as 0.27, a variation of crucial importance for practical decision-making when FS is around the stability/failure threshold of 1. Recommendations for analysis and design of pile-reinforced slopes were given.

Estimating the permanent strain of granular materials in embankments subjected to cyclic loading is a major challenge for transport engineering projects. In practice, the development of permanent strain can be divided into two periods, postcompaction and secondary cyclic compression. In this study, the existing literature on prediction of permanent strain is reviewed in detail, and the key advantages and limitations of each model are presented and discussed. Based on the gaps identified in the existing literature, a new model for predicting the permanent strain of granular materials under low cyclic loadings is proposed. This model defines two new terms, “representative cycle number” and “reference strain line,” to distinguish the postcompaction and secondary cyclic compression periods accurately. Specifically, the new model correlates the stress states, first with the accumulated strain at the end of the postcompaction period, and then with the strain rate in the secondary cyclic compression period, with good accuracy. This model eliminates the requirement for static compression tests, which are normally needed for the existing models. The new model also avoids the determination of resilient modulus, which is not a competent definitive parameter for evaluating the performance of granular materials. Further, the new model is validated by predicting the permanent strain development of two types of granular materials that are adopted in pavement subgrade and railway subgrade, respectively, in cyclic triaxial tests. The new model is applied in a trial for predicting the long-term settlement of a full-scale physical model of railway embankment under cyclic loading. The results indicate that the new model can effectively capture and accurately predict the permanent strain of testing materials under various stress states and testing conditions. It is also proved that the practical value of the new model is promising. The effects of moisture content, particle size distribution, and compaction degree were not considered, and further studies are recommended to investigate these factors.

Soil is composed of particles of various sizes. Once some particles are removed in a physical or chemical process, the particle contacts and soil microstructure will change, leading to irreversible soil deformations and changes in soil behavior. Understanding soil deformation characteristics caused by particle removal under realistic stress conditions is of great importance to the safety of earth structures. In this study, soil deformations induced by particle removal under complex stress states were investigated through a series of tests on a triaxial internal erosion test apparatus in which fine soil particles were removed through salt dissolution. These tests were performed under common realistic stress conditions: isotropic stress state, triaxial compression stress state, and triaxial extension stress state. Soil deformations, both local and global, were systematically measured using a photographic method. With a gradual loss of soil particles, both the axial and radial strains and the void ratio increased. Greater soil deformations developed under a larger shear stress ratio or a higher mean effective stress. The test results provide solid evidence for verifying numerical analyses of particulate materials.

This study investigates the effect of loading boundary conditions on the mechanical behavior of cuboidal sand specimens during plane strain (PS) testing. Deformation-controlled PS compression tests were performed with flexible boundaries (FB) on varying densities of sand. Further, rigid-frictional and rigid-lubricated boundary triaxial compression tests were performed on cuboidal specimens with aspect ratios of $2:1$ and $1:1$, respectively. The results of PS testing with the loading boundary of different relative rigidity indicate a significant change in the observed response. The relatively rigid boundaries along the loading direction tend to overestimate the stress ratio compared with those with FBs. The FB-PS tests in the present study reveal no softening behavior, unlike those exhibited in conventional triaxial tests with rigid end boundaries. The imposed kinematic constraints for PS tests resulted in higher friction angle values compared with the triaxial tests. Local strain evolution and various deformation modes were analyzed using digital image analysis, which provides ensuing insights regarding its relation to the macro-scale global material response.

The effectiveness of a new liquefaction mitigation strategy is investigated experimentally for newly constructed shallow-founded structures: an in-ground gravel–rubber (GR) panel wall system. The goal was to limit the negative consequences of liquefaction in terms of permanent seismic deformation, while benefiting from the positive consequences of liquefaction in terms of base isolation. The influence of GRs was systematically evaluated in the centrifuge on the seismic performance of a layered liquefiable deposit in the far-field and near two different model structures. The structures represented the key properties of a 3-story building (Structure A) on a 1-m thick mat foundation and a 9-story building (Structure B) with a 1-story basement. The performance of Structure A with GRs was also compared with a similar structure without mitigation and with conventional mitigation strategies that either enhanced drainage alone (e.g., prefabricated vertical drains) or increased shear stiffness around the foundation’s perimeter (e.g., structural walls). Test results showed that the GR wall system could greatly improve the overall seismic performance of short-period structures like A, but may be detrimental to long-period structures like B. The GRs below Structure A effectively isolated the total system, reducing average and differential settlements below the foundation (although not necessarily to acceptable levels), while also reducing the seismic demand transferred to the superstructure, a combination rarely observed by conventional mitigation strategies. The same GR system under Structure B experienced greater seismic moments and shear stress, inducing large shear deformations in soil that led to this structure’s significant rotation and flexural deflection. The foundation continued to rotate even after shaking because of $P\text{-}\mathrm{\Delta }$ effects, resulting in its overturning failure. These results show that GR systems can be quite effective for low-rise structures, but additional reinforcement may be necessary to reduce foundation tilt. Use of such mitigation measures under taller and heavier structures must be accompanied with great caution. Despite their practical limitations, evaluation of GR panel walls may guide future developments of combined, economical, and sustainable mitigation strategies that improve the overall performance of the soil–foundation–structure system.

This article is the first of two companion papers studying the effect of overburden pressure on the liquefaction behavior of saturated Ottawa sand. A series of four centrifuge tests were conducted simulating a 5-m layer of this sand having two different relative densities, and subjected to overburden effective pressures of ~100 and 600 kPa (1 and 6 atm). The objective was to study the pore pressure response of the soil to base acceleration under low and high pressure, including evaluation of the overburden pressure factor $K_{\sigma }$ for idealized field drainage conditions. The sand layer had a bottom impervious and a top pervious boundary, approximating a common field situation. A novel experimental technique was developed using a dry lead shot layer to provide the necessary high level of pressure. The performances of the sand layer under low and high confining pressure were compared in terms of times histories and profiles of excess pore pressures, cyclic stress ratios (CSR), and cyclic shear strains ${\gamma }_c$, with some of the parameters determined using system identification. It was found that pore pressure dissipation started earlier at shallower depths, and that partial drainage was more significant in the 6-atm than in the 1-atm tests. Field overburden pressure correction factors at 6 atm, $K_{\sigma }$, obtained from the centrifuge tests for ${(r_u)}_{\max }=0.8$ in 10 cycles of shaking and including the partial drainage effect, were found to be higher than 1.0 for both $D_r=45\%$ and 80% This is different from the usual laboratory undrained $K_{\sigma }<1$ based on cyclic triaxial and simple shear laboratory tests and reflected in the current state of practice. The discrepancy is related to the more significant effect of partial drainage and deviation from the undrained assumption at the higher confining pressure for the field drainage and other conditions of these centrifuge tests.

This article is the second of two companion papers studying the effect of a high overburden pressure on the liquefaction behavior of saturated Ottawa sand. A series of four centrifuge experiments were conducted simulating a 5-m prototype layer of this sand in the field, having two relative densities and subjected to overburden effective pressures, ${\sigma }_{v0}^{\prime }$, of ~100 and 600 kPa (1 and 6 atm). The layer was on a rigid impervious base and could drain freely at the top. This was supplemented by undrained stress-controlled and strain-controlled cyclic triaxial tests on the same sand consolidated at 1 and 6 atm. The laboratory undrained overburden pressure factor at 6 atm obtained from the triaxial tests on loose sand, $K_{\sigma }=0.85$, is consistent with the state of practice (SoP), which assumes that $K_{\sigma }<1.0$ and $K_{\sigma }$ decreases with ${\sigma }_{v0}^{\prime }$. However, in the centrifuge experiments and ${\sigma }_{v0}^{\prime }=6\mathrm{atm}$, the field $K_{\sigma }=1.28$ for loose sand and $K_{\sigma }>1.15$ for dense sand. The discrepancy is due to more significant partial drainage during shaking in the 6-atm centrifuge models. Although the excess pore pressures at the bottom of the sand layer seem to have been close to undrained in the four experiments, they were much smaller at shallower elevations in the 6-atm tests compared with the 1-atm tests. Further analysis is conducted by evaluation in the four centrifuge experiments of the coefficient of consolidation, $c_v$, during the dissipation phase. This is done using the recorded pore pressure and settlement data. It is concluded that $c_v$ was two to four times greater during dissipation in the 6-atm centrifuge tests. The reason is the increase—also by a factor of two to three—of the drained constrained volumetric stiffness of the sand, $M^{\prime }=1/m_v$, when going from 1 to 6 atm. This finding plus other data from the literature suggest that for a range of sands, layer thicknesses, field conditions, earthquake shaking, and values of ${\sigma }_{v0}^{\prime }$, both $M^{\prime }$ and $c_v$ may increase proportionally to $\surd {\sigma }_{v0}^{\prime }$, with the field $K_{\sigma }>1.0$, and with $K_{\sigma }$ increasing instead of decreasing with ${\sigma }_{v0}^{\prime }$.

Static liquefaction failure and the ensuing flow slide of slopes have produced significant damages to structures and even loss of lives. Based on a very large number (1,632) of laboratory shear tests on cohesionless soils and mine tailings, a triggering excess pore-water pressure ratio ($r_{u,tr}$) is introduced in this study above which static liquefaction failure could occur. The effects of variations in the direction and relative magnitudes of principal stresses associated with different modes of shear, ground slope, and boundary conditions are incorporated for predicting $r_{u,tr}$. The findings compare favorably with pore-water pressures measured just prior to the onset of failure in a field case study and several flow-slide flume experiments. The triggering pore pressure ratio suggested in this study can be employed as a more tangible criterion for detecting liquefaction triggering and landslide warning in instrumented slopes of cohesionless soils and mine waste tailings.

Excavation beneath an existing building to add a new basement is an effective mean to expand underground space that caters to the increased need of space in urban areas. Because piles serve as load-bearing structures in high-rise buildings, excavation inevitably changes the bearing capacity of the existing piles and affects the safety of aboveground structures. This paper presents a series of experimental tests in a calibration chamber designed to clarify the effect of excavation on the performance of existing loaded piles. Excavation tests as well as pile load tests at the ground level and at the formation level of excavation were involved in capturing the effect of excavation on the capacity, stiffness, and load transfer of loaded piles. Test results showed that the reduction of pile capacity due to excavation is proportional to the magnitude of confinement of the area to be excavated. Constructing a new basement beneath an existing basement may result in a larger reduction of pile capacity when comparing that conducted at the ground surface. Unlike the nonloaded pile subjected to excavation, tensile force is not observed along the loaded pile shaft in the present test series. The results also indicated that the stress relief induced by excavation may be instrumental in the stiffness efficiency of the pile group.

Drying-induced consolidation in soil is defined as volumetric shrinkage by interparticle stresses (suction stress) during drying under conditions of zero external or total stress. A new analysis is presented to synthesize recently published and new experimental data for soil water retention, shrinkage, physicochemical properties, and index properties for a broad range of soils ranging from nonexpansive to highly expansive. The suction stress characteristic curves of these soils are computed and compared using two deformation-based methods: the previously established discretized element solution and a simpler bulk-volume solution. Drying-induced consolidation for unsaturated soils exhibits a similar behavior to traditional consolidation behavior for saturated soils. The demonstrated strong correlations between the compression index and soil water retention characteristics and between the compression index and geotechnical index properties provide rational linkages between the fundamental soil properties and bulk deformation properties, where in this case the compression index is defined as the slope of the void ratio versus logarithm of negative suction stress relationship. These correlations are expected to be useful as new fundamental index properties for soil classification and for geotechnical applications involving desiccation and volume change.

Backward erosion piping is a leading cause of levee failures, second only to overtopping, and is therefore of great concern to engineers involved in flood control. Backward erosion piping refers to a process by which shallow erosion channels propagate upstream through foundation sands beneath water-retaining structures. If the erosion channels reach the upstream source of water, the channels rapidly enlarge, which can ultimately lead to collapse of the structure. Observations from the Mississippi River indicate that most erosion incidents do not lead to failure. This may be in part due to the slow rate at which backward erosion piping advances, as observed in laboratory experiments. Unfortunately, very limited research has been conducted on backward erosion progression rates, making it difficult to assess the timing of development. This study evaluates the progression rate of backward erosion through analyses of small-scale flume experiments conducted on nine uniform sands with median particle diameters ranging from 0.30 to 2.52 mm. Results indicate that pipe progression rate is proportional to seepage velocity, but is also influenced by particle diameter and void ratio of the sand.

The proliferation of data collected by modern tunnel boring machines presents a substantial opportunity for the application of data-driven anomaly detection (AD) techniques that can adapt dynamically to site specific conditions. Based on jacking forces measured during microtunneling, this paper explores the potential for AD methods to provide a more accurate and robust detection of incipient faults. A selection of the most popular AD methods proposed in the literature, comprising both clustering- and regression-based techniques, are considered for this purpose. The relative merits of each approach is assessed through comparisons to three microtunneling case histories in which anomalous jacking force behavior was encountered. The results highlight an exciting potential for the use of anomaly detection techniques to reduce unplanned downtimes and operation costs.

Closed-form analytical solutions are presented for one-dimensional heat transfer through saturated soil with effective porosity and steady fluid flow. The solutions yield distributions of temperature and total heat flux for both transient and steady-state conditions within a soil block having constant temperature boundaries. The analysis adopts 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. Solutions are first developed and experimental data are provided to highlight the significance of effective porosity with regard to soil thermal conductivity. Numeric examples are presented to illustrate the effects of the thermal Peclet number, thermal dispersivity, and effective porosity on heat transfer behavior. Depending on conditions, each parameter can affect heat transfer in saturated soil significantly. The solutions also demonstrate the requisite uniqueness when cast in terms of dimensionless parameters.

Design of flexible pavements over fine-grained soils requires determination of subgrade resilient modulus over a wide range of degree of saturation and suction for different soils. A novel experimental setup was developed by integrating a cyclic triaxial apparatus with capability to control suction using axis-translation and automated vapor pressure control to the specimen gas phase. System performance was evaluated through repeated load triaxial (RLT) tests for suction ranging from 0 kPa at saturation to 600 MPa at drier conditions. Replicate tests performed on a silty soil and a high-plasticity clayey soil indicated excellent repeatability. Resilient modulus of the materials is essentially unaffected with drying at low-suction range near the air-entry value and the optimum moisture content condition. This property then increases rapidly with subsequent drying until reaching a residual state after which the rate of increase in resilient modulus with respect to suction decreases to a low value. Limitations of a recent prediction model in capturing this trend demonstrated the need to determine resilient moduli over a wider range of suction for developing robust resilient moduli prediction model.

The need to tunnel closely beneath piles is increasing due to the development of urban areas. This poses a risk to the stability and serviceability of overlying structures (e.g., buildings, piers, and piled embankments). The impact of tunneling on piles is usually assessed using a displacement threshold, yet this provides no information about the posttunneling pile safety factor. Knowledge of a pile’s safety factor under serviceability or extreme loading conditions is important, especially if future repurposing of the associated superstructure is a possibility. Tunneling can reduce the safety factor of a pile up to the point of geotechnical failure (i.e., when the pile capacity reduces to that of the applied load), yet little guidance is available to enable a straightforward means of assessing the posttunneling safety factor of a pile. This paper aims to address this shortcoming by providing design charts based on an analytical tunnel-single pile interaction approach that provides a means of determining a posttunneling pile safety factor. The methodology and design charts are applicable to drained soil conditions and include for the effects of the initial pile safety factor, the pile installation method [displacement (driven and jacked), nondisplacement (bored) with only the shaft capacity, and nondisplacement with base and shaft capacity] and varying water table depths. In the paper, as a validation exercise, analytical predictions are compared against data from geotechnical centrifuge tests designed to model both displacement and nondisplacement piles in sands, including a variety of tunnel–pile relative locations and initial pile safety factors. For a specified design value of a posttunneling pile safety factor, the design charts enable a quick assessment of the safe location of a pile or a tolerable tunnel volume loss considering ground parameters, water table position, pile installation method, and initial safety factor.

In situ pore pressure dissipation in soil primarily depends on the coefficient of consolidation and permeability of the soil. This study represents an initial effort to investigate pore pressure dissipation induced by high-velocity impacts of a portable free-fall penetrometer (pFFP), and to explore the applicability of existing solutions, developed for cone penetration testing (CPT), for estimating the coefficient of consolidation. For this purpose, pFFP data from four test sites across North America were reviewed, and the same pFFP was deployed in a large fabricated and instrumented clay sample. In the laboratory, pore pressure recordings from four pressure transducers placed in the clay sample surrounding the path of the pFFP were obtained in addition to recordings of the pFFP transducer in the $u_2$ position. Pore pressure dissipation behavior in line with dilatory dissipation was observed, characterized by an initial increase in pore pressures and a subsequent decrease. The dissipation curves were interpreted using a square-root time extrapolation technique from the literature. The results suggest that the square-root time extrapolation technique appears suitable for the interpretation of data from pFFP dissipation tests. Challenges regarding obtaining high-quality pressure data using pFFP, as well as regarding full-scale testing in the laboratory, are discussed. Among other observations, the preliminary data suggest that data impacted by issues in the filter may be interpreted using the same technique, although it will lead to overprediction of the time to 50% consolidation.

Fine-grained soils that expand when in contact with water can be a major issue in some geotechnical situations, but the soil can be stabilized through chemical means by hydrated lime incorporation. However, there is not yet any rational dosage methodology that combines the effects of both lime content and porosity of the treated soil specimen to predict its behavior regarding swelling. Thus, the present research intends to assess the one-dimensional swelling response of an expansive fine-grained soil stabilized with lime. For this purpose, compacted soil–lime blends were molded with three distinct amounts of lime (2%, 4%, and 6%), compacted to three different dry unit weights (14, 15, and $16\mathrm{kN}/{\mathrm{m}}^3$) and tested after 3 h of curing. The results show that lime content, porosity, and their interaction are statistically significant in altering the swelling behavior of the compacted blends. Moreover, both can be combined through the adjusted porosity/lime index and related to the one-dimensional swelling. As a result, a single unique relationship could be established between the swelling and the proposed index with a coefficient of correlation ($R^2$) of 96%. This approach was also successfully employed in other fine-grained soils treated with lime as validation.

Investigating the mechanical properties of rockfills requires laborious, time-consuming, and expensive large-scale testing. Therefore, practitioners frequently adopt design parameters based on a limited number of reports with experimental results. With the aim of enlarging and consolidating the database on the mechanical behavior of coarse rockfills, this paper compiles 158 drained triaxial compression tests conducted on 33 different materials, performed on samples $\sim 1\mathrm{m}$ in diameter and having a maximum particle size between 100 and 200 mm. Data are analyzed in terms of particle breakage, shear strength, and stiffness. The results are compared with limits for high and low shear strength previously reported. At confining pressures lower than 0.2 MPa, rockfills consistently have a maximum internal friction angle higher than 45°; at high pressure, this value decreases to a range between 30° and 40°, mainly due to degradation caused by particle breakage. Average secant Young’s moduli for all uniform and well-graded rockfills analyzed are in the typical range for loose sands, characterized by a normalized secant modulus of 100 to 200.

The prediction models of penetration resistances of spudcan footings on sand overlying clay have been established by extensive centrifuge tests and large-deformation numerical simulations. However, most existing models have been based on deterministic analyses, where the measurement deviation of soil strength profiles was not considered. A parameter estimation technique to improve the predictions of the deterministic models is developed by using the penetration resistance data measured at depths shallower than the current. The divergence between the prediction of the deterministic model and the measurement is attributed to the uncertainties of soil properties. A deterministic model, termed HU15, is used to provide the original prediction, and two properties of the clay layer are adjusted with measured resistances prior to the peak resistance in the upper sand layer and after punch-through in the underlying clay layer. The parameter estimation technique combined with the HU15 model shows satisfactory performance when it is verified against the existing data from centrifuge and field tests.

A complete understanding of soil–water interactions and the corresponding mechanical behavior of unsaturated soils requires differentiating adsorptive and capillary components of water retention and dominant water uptake mechanisms. Water vapor sorption (WVS) isotherms have historically been used to quantify the water uptake behavior of clayey soils and to determine related mineral surface properties, such as specific surface area and cation exchange capacity. This paper introduces the WVS kinetics curve as a new measure for gaining additional insights into the WVS behavior of clays. The sorption rate calculated from WVS kinetics curves scales with the cation heat of hydration at low relative humidity ($\mathrm{RH}<10\%$), indicating that cation hydration is the first mechanism for water uptake by dry clays. Sorption rates up to 25% RH are related to monolayer adsorption and specific surface area (SSA). A distinct relationship is proposed to relate SSA to the sorption rate normalized with predominant cation valence.