Journal of Geotechnical and Geoenvironmental Engineering

Lateral swelling pressure (LSP) can pose significant threats to the safety and stability of the geo-infrastructure. For this reason, it is necessary to take into account the influence of LSP in the design of geo-infrastructure such as basement walls, retaining walls, pile foundations, and pipelines built within or adjacent to expansive soils upon water infiltration. A relationship is developed to calculate the LSP upon free swelling from the vertical swelling pressure (VSP), which can be measured from conventional laboratory tests. This relationship is extended to calculate (1) the lateral earth pressure (LEP) behind a retaining structure with expansive soils as backfill material, and (2) the uplift friction along a single pile placed in expansive soils upon infiltration. Experimental results from large-scale tests and centrifuge tests from published literature are used to validate the proposed methods. The studies presented in this paper not only highlight the influence of LSP on the geo-infrastructure but also provide simple tools for taking account of it in the conventional geotechnical engineering practice for both saturated and unsaturated expansive soils.

A laboratory study was undertaken to assess the effects of polymer treatment (PT) on the monotonic, cyclic, and postcyclic behavior of a low plasticity slurry using a direct simple shear (DSS) apparatus. This study was conducted to extend the results of previous testing that assessed the effects of PT on the same material’s consolidation behavior and critical state line. Consistent with previous tests on this material, DSS testing indicated that PT resulted in lower consolidated densities at a given magnitude of effective stress, and higher undrained shear strengths at a given density. PT appeared to increase the effects of strain rate on strength, whereas both PT and untreated materials responded similarly to the effects of overconsolidation. Cyclic and postcyclic testing indicated essentially indistinguishable results for the two materials. The effects of PT were seen to persist at vertical effective stresses up to 800 kPa. The potential implications of these findings for tailings design are discussed.

This paper presents numerical simulations of the performance of the Geosynthetic Reinforced Soil–Integrated Bridge System (GRS-IBS) under static loading conditions. Simulations were conducted using a finite-difference program and realistic conditions for system geometry, backfill soil, geosynthetic reinforcement, and applied loads. Simulation results, including lateral facing displacements, settlements, lateral and vertical earth pressures, and reinforcement tensile strains and forces, indicate good performance of GRS-IBS during construction and under traffic loads. A parametric study was conducted to investigate the effects of backfill soil compaction, reinforcement length, reinforcement stiffness, bearing bed reinforcement, bridge seat setback distance, bridge load, and abutment height on the performance of GRS-IBS. Results indicate that reinforcement stiffness, bridge load, and abutment height have the most significant influences on lateral facing displacements and bridge seat settlements. Differential settlements between the bridge and approach roadway were small for all conditions.

The paper compares two liquefaction case histories in California: (1) the response of the Wildlife site in the Imperial Valley to the 2010 El-Mayor Cucapah earthquake ($M_w=7.2$, $a_{\max }=0.15\mathrm{g}$); and (2) the response of the Treasure Island Fire Station (F.S.) site in the San Francisco Bay area to the 1989 Loma Prieta earthquake ($M_w=6.9$, $a_{\max }=0.16\mathrm{g}$). Both histories involve silty sand critical layers with nonplastic fines contents, $\mathrm{FC}=24–27\%$, similar normalized shear wave velocities, $V_{s1}=145–155\mathrm{m}/\mathrm{s}$, low cone penetration test (CPT) cone penetration resistances, and groundwater tables at essentially the same depth. The corresponding data points plot almost on top of each other on the shear wave velocity field liquefaction charts, which predict liquefaction at both sites. While Treasure Island F.S. did liquefy during the shaking, Wildlife did not and was far from liquefaction as indicated by piezometers at the site. This paper constitutes an attempt to understand the reason for these very different pore pressure responses through a detailed analysis of similarities and differences between the two histories. It is concluded that preshaking by previous earthquakes is the most probable explanation of the higher liquefaction resistance exhibited by the Wildlife site and other sites in the Imperial Valley. While the Wildlife critical layer was subjected to about 60–70 earthquakes capable of generating significant excess pore pressures between its estimated 1907 deposition and the 2010 earthquake, the Treasure Island F.S. layer was subjected to only about two earthquakes capable of doing so between deposition in the 1930’s and the 1989 earthquake. This difference is due to the very high seismic activity in the last 100-plus years in the Imperial Valley compared with a seismically quiet San Francisco Bay Area after the 1906 earthquake. The significance of the prior seismic history is corroborated by recent results from centrifuge and large-scale experiments. These results as well as the methodology developed in the paper may be helpful when analyzing the observed high liquefaction resistance of sandy sites located in other seismic regions.

This study evaluated migration of five common volatile organic compounds (VOCs) through simulated composite landfill liners that employ a co-extruded geomembrane (GM) with an interior layer of ethylene-vinyl alcohol (EVOH). A series of column tests was conducted with composite liner configurations employing 1.5-mm- and 1.0-mm-co-extruded EVOH GMs with outer layers of high-density polyethylene (HDPE) or linear low-density polyethylene (LLDPE) and 1.5-mm HDPE GMs. A simulated compacted clay liner (CCL) or a geosynthetic clay liner (GCL) was placed under the GM in each test. VOC breakthrough in composite liners employing HDPE GMs (approximately 30 days) occurred approximately four times faster than for co-extruded EVOH GMs with a HDPE outer layer (approximately 130 days) and with significantly higher VOC concentrations. Co-extruded EVOH GMs with LLDPE and HDPE as an outer layer have diffusion coefficients ($0.11–0.58\times {10}^{-13}{\mathrm{m}}^2/\mathrm{s}$) more than 20 times lower than those for conventional HDPE GM ($2.86–11.05\times {10}^{-13}{\mathrm{m}}^2/\mathrm{s}$). Numerical modeling of toluene migration through a composite liner with a 0.6-m-thick CCL and a co-extruded EVOH GM indicates that toluene concentrations are approximately 42% lower at one hundred years compared with a similar composite liner with a HDPE GM.

Antioxidant depletion was evaluated in high-density polyethylene (HDPE) geomembrane (GM) coupons immersed in radioactive synthetic leachate (RSL) representative of leachate in low-level radioactive waste (LLW) disposal facilities operated by the U.S. Department of Energy’s environmental restoration programs. Depletion was assessed at four temperatures (25, 50, 70, and 90°C). Comparative tests were conducted with nonradioactive synthetic leachate (NSL) having the same chemistry as RSL, except radionuclides were excluded. Control tests were conducted with deionized (DI) water. One-sided exposure tests were also conducted with the HDPE GM in RSL at 70 and 90°C. Specimens were removed periodically and tested to determine antioxidant depletion, melt flow index (MFI), crystallinity, and stress crack resistance. Standard and high-pressure oxidative induction time (OIT) tests were conducted to measure antioxidant depletion. Antioxidant depletion rates in RSL were only slightly greater than those in NSL, indicating that radionuclides in the LLW leachate had only minor effect on antioxidant depletion. Antioxidant depletion in RSL and NSL occurred 1.1–1.9 times faster than in DI water. Antioxidant depletion in HDPE GMs exposed to RSL and NSL at 90°C was complete after 12 months. MFI decreased systematically after 15 months of immersion, which is indicative of crosslinking due to oxidation. Crystallinity also decreased slightly after 12 months, whereas stress crack resistance (SCR) showed no trend over the immersion period. Arrhenius modeling was used to extrapolate the laboratory data at elevated temperatures to a typical LLW liner at 15°C. Predicted time for antioxidant depletion for a 2-mm-thick HDPE GM in a composite liner in contact with LLW leachate is estimated to be 730 years. The total service life of HDPE GMs in contact with LLW leachate is estimated to be at least 1975 years.

Results from a series of hydraulic tests conducted on four compacted granular filters in a one-dimensional rigid cell under static and cyclic loading conditions are presented. It is revealed that cyclic loading promotes premature washout failures in internally unstable and marginal specimens. The constant agitation of granular media combined with internal pore pressure affects the geometrical arrangement of stable primary fabric (coarse fraction). The results prove that washout becomes excessive at higher loading frequencies, such that marginally stable specimens also become increasingly unstable (higher effluent turbidity). The analysis also reveals that the existing criteria developed for static filtration cannot accurately capture the true potential for internal instability of some specimens tested in this study. Consequently, a revised geometrical approach is proposed that incorporates cyclic conditions and demarcates a more distinct boundary between internally stable and unstable soils. A broad experimental database adopted from published studies for validation showed a close agreement with the proposed approach.

A database of shear-wave velocity ($V_s$) measurements using a variety of techniques and soil properties measured on high-quality samples for 28 Norwegian sites has been established. The purpose was to evaluate the different methods of measuring $V_s$, to present guidelines and correlations to assist in estimating $V_s$ profiles in these clays in the absence of site-specific data, and to outline relationships that can be used to give first-order estimates of soil properties. It was found that consistent measurements of $V_s$ can be obtained from a variety of techniques and that for practical engineering purposes the $V_s$ values obtained from the different methods are similar. Surface wave techniques can be particularly useful but careful survey design is necessary and in particular the inversion process needs to be carefully controlled. Differences of about 15–20% can be obtained in the $V_s$ values depending on the algorithm used. $V_s$ values for Norwegian clays are consistent with well-established frameworks for other materials, based on relationships between effective stress and index parameters. Piezocone penetration testing (CPTU) can be used to give acceptable estimates of $V_s$ and this includes techniques which utilize the CPTU data only and are independent of any index property. $V_s$ correlates well with triaxial compression and direct simple shear derived undrained shear strength ($s_u$) values. There appears to be a particularly good link between $V_s$ and preconsolidation stress ($p_c^{\prime }$). Satisfactory relationships also exist between $V_s$ and the tangent moduli of the clays at in situ stress ($M_0$) and at $p_c^{\prime }$ ($M_L$).

A constitutive model is presented in this paper to describe the isotropic compression response of unsaturated, compacted clay under drained conditions over a wide range of mean effective stresses. The model captures the key transition points of the compression curves at different stress levels, ranging from the preconsolidation stress, to pressurized saturation, to the initiation of void closure. The results from drained, isotropic compression tests on compacted clay specimens having different initial degrees of saturation up to a mean total stress of 160 MPa were used for model calibration. The suction hardening effect on the preconsolidation stress and the nonlinear compression curve of unsaturated clay up to the point of pressurized saturation were captured using an extended form of an existing effective stress-based constitutive model. For higher mean stresses, an empirical relationship to consider the transition to void closure was incorporated to fit the observed compression curves of the compacted clay specimens. The transition to void closure was found to be affected by the initial compaction conditions despite the fact that all of the specimens were pressure saturated in this mean stress range.

The deterioration of a rail track due to large dynamic wheel loads is inevitable over the years and leads to frequent, high-cost maintenance. This problem is more critical in isolated rail track locations such as bridges and tunnels, where the substructure is much stiffer than the surface track assembly. One measure used to minimize track deterioration is geosynthetic inclusions such as rubber mats under the layer of ballast. In this study, cyclic loads from fast and heavy-haul trains were simulated on stiffer track foundation conditions using a large-scale process simulation triaxial (prismoidal) apparatus (PSPTA) to investigate the performance of ballast improved by rubber mats locally manufactured from recycled tires. The laboratory results indicate that the energy-absorbing (damping) characteristics of rubber mats reduce the amount of deformation and degradation of ballast under stiffer track conditions. The study shows that rubber mats distribute the stress applied from moving trains more uniformly by increasing the effective contact area, which then reduces the dynamic amplification of applied vertical stress and leads to much less ballast degradation.

Among various ground-improvement techniques, soft-soil reinforcement by stone columns is one of the most common and convenient methods with numerous benefits including increased bearing capacity and consolidation, reduced postconstruction settlement and lateral movement, and improved slope stability and liquefaction control, among others. Because of the limited confinement offered by the surrounding soft soil especially at shallow depths, lateral deformation of stone columns is not uncommon. Although several analytical and numerical solutions are available to predict the load-settlement performance and consolidation characteristics of stone-column-improved soft ground, most existing models do not accurately capture the lateral deformation of stone columns. In view of this, the authors have developed in-house a novel numerical model based on the Fast Lagrangian Finite-Difference technique with associated subroutines to analyze the behavior of a stone column including its lateral deformation. In particular, the displacement compatibility and the barreling effect are considered in the model. Soft-soil consolidation under imposed loading is considered by adopting the modified Cam-clay theory. The proposed solutions are validated using available field observations and existing numerical solutions. The model was successfully applied to a selected case study at the Pacific Highway near the town of Ballina, New South Wales, Australia. It is demonstrated that both the deformation pattern and bulging depth of stone columns are dependent on several factors including the particle interlock, imposed load-intensity, soil-column stress concentration ratio, soil shear strength, and column geometry.

This paper presents four liquefaction and pile response case histories associated with highway bridges from the April 22, 1991 7.6 magnitude (M) earthquake near Limón, Costa Rica that were analyzed more than 20 years after the earthquake. Details regarding observed soil layering, measured soil properties, site geometries, structural details, and damage are presented. Back-analysis of lateral spread displacements, liquefaction triggering, and kinematic pile response are performed to assess methods and models commonly applied in modern engineering design. Results of the liquefaction and lateral spread back-analysis show that conventional empirical methods for estimating lateral spread displacements can yield reasonable displacement predictions if multiple models are used and averaged. Empirical models tend to underestimate displacements in cases where considerable fines were encountered in the liquefiable soil. Simplified Newmark-type slope displacement models significantly underpredict the ground displacements observed at the bridge abutments of the four case histories. Results of the kinematic pile response back-analysis demonstrate that simplified conventional superpile methods closely replicate the observed pile response from the four case studies, particularly when using a simplified hybrid p-y model for the liquefied soil. Additional important lessons regarding the resilience of damaged infrastructure, the contribution of the bridge deck in the kinematic loading of piles, and the importance of considering void-ratio redistribution and the potential development of water films in kinematic pile response are discussed.

A 24–33-m-deep cross excavation of a metro interchange station in Shanghai soft clay has been constructed and monitored for 2 years. The excavation area was $\mathrm{9,000}{\mathrm{m}}^2$ and supported by diaphragm walls. For construction convenience, the excavation was split into four zones (multiple pits) with varied sizes and depths. On the basis of the interpretation of field monitoring data, the following major findings were obtained: (1) the measured wall deflections and ground settlements were smaller compared with those of similar case histories; (2) both jet-grouting and the geometry of pit played a key role in determining pit performance; (3) the location of maximum wall deflection varied dramatically with excavation depth and displayed three patterns; (4) the measured column uplifts were closely related to excavation depth; and (5) the axial forces of most struts were within 40% of design value, indicating safe for the strut system.

This paper describes the application of 10 reduced-scale calibration chamber cone penetration tests for evaluating empirical correlations employed for correcting CPT tip resistance to the overburden stress at the same relative density. A 6 mm-diameter subtraction cone with an apex angle of 60° and a net area ratio of 0.75 is used in the laboratory tests. A unique relationship is determined to correct cone tip resistance in loose to very dense quartz sands for effective overburden pressure.

Resistance factors for load and resistance factor design (LRFD) of axially loaded drilled shafts in the Las Vegas Valley are calibrated using data from 41 field load tests. In addition to the traditional use of Monte Carlo (MC) simulations for calibration, a more robust technique is investigated in which nested MC simulations are employed to capture the uncertainty associated with the interpretation of material properties from in situ test data. Measures are also taken to improve design procedures regarding cemented sandy soils colloquially referred to as caliche. Although caliche is common in Las Vegas, its potential contribution to resistance is difficult to predict using typical site investigation data and there is currently no consensus among local engineers regarding how it should be considered in design. Thus, an approach for treating caliche is proposed and compared to three other potentially viable methods. Overall it is found that the proposed design approach produces the most accurate nominal axial capacity predictions and the nested MC simulations yield lower resistance factors than traditional calibration procedures.

Microbial-induced calcite precipitation (MICP) is a novel soil-improvement technique that improves the behavior of sands subjected to dynamic loading. The level of cementation of MICP-treated sands is commonly quantified using mass of calcite precipitation; however, mass of calcite is not a unique measure for material behavior as other factors, such as the distribution of calcite precipitation at the particle contacts, would also affect the mechanical behavior of MICP-treated sands. Therefore, mass of calcite alone may not be appropriate to characterize material behavior. This study illustrates the importance of using shear-wave velocity in addition to mass of calcite to quantify the level of MICP cementation to the corresponding material behavior, since shear-wave velocity is not only affected by the mass of calcite, but also influenced by the distribution of calcite precipitation at the particle contacts. Two specimens are cemented with the MICP process to the same mass of calcite value but to different shear-wave velocities and then cyclically loaded. The observed mechanical behavior of the specimens indicates the specimen with higher shear-wave velocity possesses larger liquefaction resistance compared to the specimen with lower shear velocity, which provides evidence that the material behavior of MICP-treated sands is not only affected by the precipitated mass of calcite, but also influenced by the distribution pattern of calcite precipitation.