Journal of Geotechnical and Geoenvironmental Engineering

This study investigated the thermomechanical behavior of thermal pile groups in sand. To analyze the influence of cyclic thermal loading on the stress–strain behavior of piles in a group, pile groups containing four thermal piles installed in dense Toyoura sand were numerically investigated. A concrete pile cap was considered on the piles. Axial mechanical load was applied instantaneously on the pile cap and thermal load was applied along the pile length for six thermal cycles consisting of alternate heating and cooling of the piles. The concrete piles and pile cap were considered to behave in a linear-elastic manner under the mechanical load and thermal load. The soil was assumed to possess elastoplastic behavior and was simulated using the Mohr–Coulomb plasticity model. The effect of mechanical and cyclic thermal load on the pile groups was studied by varying the pile group parameters such as pile spacing ($s_p$), pile diameter ($D_p$), and thickness of the pile cap ($t_{\mathit{pc}}$). In all the analyses, the effect of cyclic thermal load was compared in terms of development of axial displacement, axial strains, and axial stresses in the piles. Thermomechanically loaded piles exhibited higher displacements, strains and stresses than did mechanically loaded piles. The results also indicate that the axial load on the piles under cyclic thermal loading was larger for the piles with higher aspect ratio than for the piles with lower aspect ratio. The effect of pile spacing was more pronounced in case of piles with higher aspect ratio. An increased thickness of the pile cap resulted in higher axial load and displacement in the piles. The cyclic thermal load resulted in residual or plastic strains in the piles. The thermomechanical behavior of a pile group is influenced by parameters such as pile spacing, aspect ratio, and pile cap thickness, which should be considered in thermal pile group design for structural stability performance of the pile group.

Coal ash ponds or lagoons are surface impoundments constructed to store the unused coal ash generated from thermal power plants. In India, by the end of 2020 nearly 82,200 ha of land will be under ash ponds. Once the capacity of these ponds is reached, they are closed in compliance with the statutory regulations. Recent trends suggest that these lands could be reclaimed to accept light- to heavy-weight structures over them, which makes in situ characterization essential to ensure the safety of structures built over them. This paper presents the site characterization in terms of shear-wave velocity ($V_s$) of four hydraulically deposited coal ash lagoon sites (two existing and two abandoned) at two ash pond sites in India using the multichannel analysis of surface waves (MASW) technique. The ash is deposited using the wet slurry technique, and the age of deposition is found to have a significant effect on the shear-wave velocity of these deposits. An empirical correlation is presented between the mean $V_s$ and depth ($z$) for all the sites considered. The measured $V_s$ values were extrapolated using three different methods to obtain $V_{s,30}$ values, and the sites were classified as per the recommendations of the International Building Code. Standard penetration tests (SPTs) were conducted near the MASW testing locations at one of the abandoned ash ponds, and the SPT values ($N$ values) had significant scatter. An empirical correlation is proposed between the mean $V_s$ and $N$ values obtained.

Interface friction is a governing parameter in the performance of piled foundations and other applications. Piles and other foundation elements typically mobilize a similar interface friction angle during loading in tension and compression. However, some applications may benefit from surfaces that mobilize higher shear resistance in one direction of loading relative to another. Such behavior can be achieved through inspiration from the underbelly scales of snakes, which produce frictional directionality or anisotropy. This paper presents the results of an experimental investigation on the monotonic and cyclic interface shear behavior of snakeskin-inspired surfaces and piles with sand. Laboratory test results provide evidence that snakeskin-inspired surfaces mobilize shear resistance, volumetric behavior, and strength degradation that depend on the shearing direction. Boundary conditions, sand relative density, and cyclic displacement amplitude are also indicated to influence the interface shear response. Centrifuge pile load tests are used to evaluate the installation forces, pullout capacity, and cyclic loading response mobilized by snakeskin-inspired piles. These results suggest that snakeskin-inspired surfaces can readily mobilize skin friction that depends on the direction of the displacement in piling applications.

The evaluation of the foundation capacity under combined vertical, horizontal, and moment loading is an essential element of the site-specific assessment that ensures mobile jackup rigs are safe to operate in large storms. However, the prediction approaches available in design guidelines are restricted to jackup spudcan foundations on homogeneous sand or clay. The aim of this study is to examine the ultimate bearing capacity for spudcan foundations in clay overlying sand under combined vertical, horizontal, and moment loading. This study investigates the effects of the underlying sand layer on the three uniaxial capacities and on the combined failure envelope, with results derived from three-dimensional finite-element analyses. The findings show that, as the spudcan nears the underlying sand layer, the absolute horizontal capacity remains relatively constant while the vertical and moment capacities increase at around the same rate. A closed-form expression for the failure envelope is proposed. It allows for easy assessment of the bearing capacity of a spudcan that remains in clay overlying sand. This new expression can be used during site-specific assessments of jackup platforms.

Liquefaction-induced seismic vulnerability is still a major problem in geotechnical engineering applications. To address this issue, various liquefaction mitigation techniques have been proposed to reduce the excess pore water pressures and liquefaction-induced deformations. Recently, the induced partial saturation (IPS) method, by which the fully saturated condition in loose sands is altered to be partially saturated, was proposed. In the present research, undrained cyclic strain-controlled tests were performed on partially saturated sand specimens with degrees of saturation ($S$) of 70%–89% and relative densities ($D_r$) of 21%–43% in a dynamic simple shear device with confining pressure (DSS-C) at effective stresses and back pressures ranging from 50 to 200 kPa and under cyclic simple shear strain amplitudes ($\gamma$) of 0.1%–0.4%. Various specimen preparation techniques were explored, and the best specimen preparation method was determined to be wet pluviation of dry sand into a water-sodium percarbonate mixture to obtain loose, undeformed, partially saturated sand specimens at various degrees of saturation. The test results showed that as the degree of saturation decreases, the generation of excess pore water pressure ratios ($r_u$) also decreases significantly, especially under conditions of higher effective stresses. The $r_u$ values in partially saturated sand specimens decrease as the effective stress increases. However, $r_u$ increases as the backpressure increases. The back pressure has a significant effect on $r_u$ generation in partially saturated sands, unlike in fully saturated sand tests; the true liquefaction resistance of partially saturated sand samples should be investigated under the coupled effects of effective stress and back pressure, which is equivalent to the initial pore water pressure in the field. According to the test results, the beneficial effect of effective stress on liquefaction resistance is more prominent than the detrimental effect of back pressures; therefore, we have concluded that once IPS is implemented in the field, the degree of saturation can be reduced to lower values at shallower depths.

This paper compiles two expanded databases—NUS/SpreadFound/919 and NUS/RockFound/270—to evaluate the calculation methods of foundation capacity, where the number is the number of load tests collated. The mean (bias) and coefficient of variation (COV) (dispersion) of the model factor, defined as a ratio of measured-to-calculated capacity, are computed. With the statistics of a ratio of calculated-to-observed foundation settlement reported in literature, design methods for foundation capacity and settlement are classified according to their ability to match measured values. Such a statistical-based classification provides the designer with a sense of the accuracy of a capacity or settlement model. For the 298 case records in NUS/SpreadFound/919, the uncertainty exhibited by the load-movement curves over their full range of movements is captured by two parameters in a hyperbolic fitting of measured data. Copula analysis is adopted to evaluate the observed correlation structure between the hyperbolic parameters. Finally, the model statistics are applied to calibrate the resistance factors in load and resistance factor design of spread foundations at ultimate and serviceability limit states.

This paper investigates the response of framed buildings on raft foundations to tunnel construction using geotechnical centrifuge testing. Five framed building models were considered, and the influence of building configuration, weight, eccentricity, and soil density were evaluated. Soil and foundation displacements, frame deformed shape, maximum structure deformation parameters (deflection ratios and angular distortions), and associated modification factors are illustrated. Results indicate that unlike equivalent isotropic plates, framed buildings primarily exhibit shear behavior and a semi-flexible response. Building deformed shapes indicate that angular/shear distortions (considering bay slope and local tilt) are more appropriate for quantifying framed building distortions than deflection ratios. A relative stiffness parameter is suggested to relate maximum angular distortions to the greenfield settlement slope. Moreover, the efficiency of the available relative stiffness parameters for the deflection ratio modification factors is confirmed. Limitations of the equivalent plate approach and practical implications of the results for framed buildings are discussed.

Observing the fragmentation of individual particles within granular assemblies is a subject of evident theoretical and practical importance. A new technique using dyed gypsum particles (DGPs) to match the broken particles to their parents was adopted in this study. An image-based method of acquiring the shape information of particles from two orthogonal views was proposed. The mass survival probability and shape characteristics of the children particles were analyzed after a series of one-dimensional compression tests on the DGPs. It was found that medium-sized particles in the polydisperse samples underwent more breakage than the other particles, and this might have been attributed to the combined effects of the particle crushing strength and the coordination number. The shape evolution of broken particles and surviving particles showed opposite trends. Because the particles after the test within a given size range consisted of both the broken and surviving particles, their overall shape characteristics did not show a consistent trend. Furthermore, individual particle crushing tests on the children particles suggested that the breakage-induced shape irregularity did not change the Weibull modulus, but had a substantial effect on the magnitude of the survival probability.

This work presents a critical state plasticity model for predicting the response of sands to cyclic loading. The well-known bounding surface SANISAND framework by Dafalias and Manzari is enhanced with a memory surface to capture micromechanical, fabric-related processes directly affecting cyclic sand behavior. The resulting model, SANISAND-MS, was recently proposed by Liu et al. and successfully applied to the simulation of drained sand ratcheting under thousands of loading cycles. Herein, novel ingredients are embedded into Liu et al.’s formulation to better capture the effects of fabric evolution history on sand stiffness and dilatancy. The new features enable remarkable accuracy in simulating undrained pore pressure buildup and cyclic mobility behavior in medium-dense to dense sand. The performance of the upgraded SANISAND-MS is validated against experimental test results from the literature—including undrained cyclic triaxial tests at varying cyclic loading conditions and precyclic consolidation histories. The proposed modeling platform will positively impact the study of relevant cyclic and dynamic problems, for instance, in the fields of earthquake and offshore geotechnics.

The particle breakage and compressibility behavior of sands treated with microbially induced carbonate precipitation (MICP) has been investigated using oedometric compression tests. The acid washing technique was used to obtain the calcium carbonate (${\mathrm{CaCO}}_3$) content and facilitate quantification of particle breakage by measurement of the particle size distribution (PSD). It was found that the compressibility was lower for specimens with a large ${\mathrm{CaCO}}_3$ content. Particle breakage increased with an increase in the stress or input work for specimens with approximately the same ${\mathrm{CaCO}}_3$ content. In addition, for a given applied stress or input work, MICP-treated specimens exhibited smaller particle breakage than untreated specimens, which shows that the MICP treatment can effectively restrain particle breakage.

Nonlinear dynamic analyses (NDAs) of embankment dams of different heights founded on a spatially variable, liquefiable alluvial layer are used to examine factors influencing embankment deformations and develop guidance on selecting representative properties for uniform analysis models. Simulations are presented for embankments ranging from 5 to $45\mathrm{m}$ high on stochastic and uniform alluvial layers subjected to a range of input motions, with sensitivity cases including the effects of various parameters describing the alluvium and embankments. Crest settlements and slope displacements obtained from the analyses with stochastic and uniform alluvial layers are compared to obtain equivalent uniform or representative percentile properties for which a uniform model produces the same deformation as a stochastic model. The representative percentile properties to estimate median deformations from a set of stochastic realizations are generally between the 40th and 60th percentile, whereas the representative percentile properties to estimate deformations conservatively (i.e., exceeded in less than 16% of the analysis cases) are generally closer to the 30th percentile. The variability in deformation patterns obtained with the stochastic models increases as the alluvium’s scale of fluctuation in the horizontal direction increases relative to the embankment base width. Recommendations regarding factors to consider in selecting representative properties for spatially variable alluvial foundations in NDAs of embankment dams and the corresponding variability in deformations are presented.

Microbially induced calcite precipitation (MICP) is a ground improvement technique that uses ureolytic bacteria to biocement soils by precipitating calcium carbonate on soil contacts and surfaces. In this study, five 3.7-m long horizontal columns, each containing $0.15{\mathrm{m}}^3$ of natural sand, were treated to address current knowledge gaps regarding the application of MICP at field-scale including investigating treatment extent, improvement of spatial uniformity, stimulation strategies, and posttreatment removal of ammonium by-products. Two stimulated columns containing poorly graded alluvial sand were treated to achieve high and low ureolytic rates to investigate differences in treatment uniformity and extent. An additional column with the same sand was augmented with Sporosarcina pasteurii targeting a high ureolytic rate similar to the high rate stimulated column. Two additional stimulated columns, containing poorly graded alluvial and marine sands, were treated to achieve a low ureolytic rate to evaluate the effect of soil mineralogy. Treatments were first applied to establish either indigenous or augmented microorganisms, after which all columns received nine cementation treatments. Following cementation, produced ammonium by-products were removed using a rinse solution injection and soil samples were obtained and analyzed for calcite content. During all treatments, solution urea and ammonium concentrations as well as soil hydraulic conductivities and shear wave velocities were monitored. In all columns, insignificant changes in permeability were observed during treatments despite ${\mathrm{V}}_{\mathrm{s}}$ increases up to $\mathrm{1,325}\mathrm{m}/\mathrm{s}$. Results suggest that improvements in the spatial uniformity and extent of biocementation can be achieved through the use of lower ureolytic rates that minimize reactions during injections.

Lateral spreading analysis of column-supported embankments (CSEs) requires an understanding of lateral thrust distribution. This includes quantifying the portion of thrust that is resisted by tension in geosynthetic reinforcements installed in the load transfer platform. Results from a three-dimensional (3D) numerical parametric study using a half-embankment domain and totaling 140 scenarios are presented in terms of lateral thrust distribution. Forces examined include the lateral thrusts in the embankment and foundation soil, the geosynthetic tension, and the base shear at depth, and results are presented for the limiting cases of lateral spreading (i.e., undrained end-of-construction and long-term dissipated). Results show that lateral thrusts induced by embankment loading are significant in the embankment, foundation soil, and base shear beneath the columns. However, the portion of lateral thrust carried by the geosynthetic is limited, though it increases with the geosynthetic stiffness. Results also indicate that lateral spreading in CSEs is more critical at the undrained end-of-construction condition than in the long-term condition after excess pore water pressures have dissipated. Correlations for the thrust distribution at these limiting conditions and different embankment locations (i.e., centerline, shoulder, and toe) are provided.

A solution for the response of flexible retaining walls excited by vertically propagating shear waves in inhomogeneous elastic or viscoelastic soil is obtained using the weak form of the governing differential equation of motion associated with the Winkler representation of earth pressures, as a function of relative displacement between the wall and free-field soil. Inputs to the model include the soil shear wave velocity profile, flexural stiffness of the wall, elastic boundary conditions at the top and bottom of the wall, motion at the surface of the retained soil, and mass distribution along the wall. The proposed solution was first verified against an available closed-form Winkler solution for uniform soil and then with elastodynamic solutions for a wall supporting an infinite uniform elastic soil. A validation exercise was then performed using centrifuge data from flexible underground structures embedded in sand, shaken by suites of ground motions. Seismic earth pressures and bending moments were also computed using limit-equilibrium procedures based on horizontal inertial forces acting within an active wedge. The proposed solution compares favorably with the experimental data, whereas limit equilibrium procedures produce biased predictions.

Several noteworthy stability failures occurred at landfills in the United States in the 1980s and early 1990s, a timeframe coinciding with the promulgation of modern US environmental regulations. These failures were extensively studied, and lessons were learned. A state-of-practice developed to enable the design of waste fills to be stable throughout their construction, operation, and closure periods. However, a survey of landfill performance in the United States in the 2010–2019 timeframe shows that waste fill stability failures continue to occur. This paper, an expansion of the 2018 Terzaghi Lecture given by the first author, presents a brief review of several waste fill failures from the 1980s and 1990s and the lessons learned during that period. Several more recent waste fill failures are then reviewed, from which it is concluded that 20–30 years after the earlier failures, facility operators and design engineers are relearning the earlier lessons, as well as new lessons related to evolving waste streams and operating practices. The paper concludes with a discussion of the current standard-of-care for the design of US waste fills and suggests that this standard can be improved through application of the lessons described herein.

Deep and high-stress mining relies on backfill to support exposed host rock surfaces, but the backfill response to isotopic compression is virtually unknown. This paper studied the properties and behavior of a cemented paste backfill (CPB) for different cement contents (CCs) and specimen curing times (CTs), for isotropic stresses up to 6.5 MPa. The isotropic compressive behavior was characterized by an initial linear elastic preyield response quantified by the bulk modulus and a linear inelastic postyield response at high stress. The results showed that the postyield compression line loci depend on cement content and curing time of CPB, and fitting functions were determined to predict this evolving behavior based on cement content and specimen cure time. The results could form the basis for developing and calibrating the isotropic compression hardening laws for future constitutive models.

This technical note presents results from a series of undrained load tests performed at model scale on circular embedded footings founded in a two-layered stratigraphy, comprising uniform stiff clay overlying soft clay. The observed foundation stiffness and bearing capacities are compared with available empirical, analytical, and numerical solutions. The dependence of the equivalent linear stiffness at a settlement ratio of 1% ($E_{0.01}$) and the bearing capacity factor, $N_c$, on the normalized depth to the soft clay ($H/B$) and strength ratio of two clay layers ($s_{ut}/s_{ub}$) are presented. A simple expression is developed for $N_c$, which provides a good match to experimental data and is consistent with numerical predictions. It is also shown that the critical $H/B$ ratio, above which the underlying soft layer does not affect the footing response, is significantly smaller for $E_{0.01}$ than for $N_c$ at any given $s_{ut}/s_{ub}$ value. This finding has important practical design implications for footings on stiff-over-soft clay deposits.

Microbial-induced carbonate precipitation (MICP) methods have been developed in recent years for soil improvement to simultaneously increase the shear strength and reduce the permeability of soil or aggregate. However, this method is difficult to use for aggregate because many more injections are required. This technical note proposes a new biogrouting method for aggregates. In this method, biogrout solution containing bioslurry is injected before injection of cementation solution alone into aggregate, which is kept in an unsaturated state. Due to the capillary effect, more calcium carbonate crystals in the bioslurry are retained around the contact points of the particles, rather than in the pores. As a result, this method can achieve a higher shear strength (2.98 MPa) for biogrouted aggregate compared with that using other MICP methods (0.78 MPa) at the same level of calcium carbonate content. Therefore, the permeability reduction also is smaller using this method. The proposed method can be used for applications which require only an increase in strength, such as for granular base for pavement or the toe drainage of a slope.

This technical note addresses the possibility of replacing portland cement, the production of which is harmful to the environment, with a new, sustainable residue mixture. This new mixture, composed of ground glass powder (residue from glass waste recipients) and carbide lime (by-product of acetylene gas production), is examined through the performance of steel circular spread footings bearing on mixture-amended sandy layers over a residual soil site. Similar to portland cement–treated layers, the results showed an increase in the bearing capacity and two distinctive failure modes (soil punching and generalized failure of the improved layer). The coupling of existing analytical solutions proved to be a useful way to predict the failure mechanism and bearing capacity of sustainable treated layers bearing on a weakly bonded residual soil site. These results contribute to the understanding of the conditions in which sustainable materials can be applied in improved layers to replace traditionally used materials in infrastructural applications.