Journal of Geotechnical and Geoenvironmental Engineering

Abstract

The computations of the bearing capacity of foundations have generally been carried out with the usage of the Mohr-Coulomb failure criterion—a linear yield envelope in a shear stress–normal stress plot. However, as noted from many experimental observations, the failure criteria associated with most geomaterials are generally nonlinear. A novel computational analysis, based on the stress characteristics method, has been performed in the current study to compute very accurately the seismic bearing capacity of a rough strip foundation considering a nonlinear power-law yield criterion. The analysis incorporates the effect of pseudostatic horizontal seismic inertial forces. The obtained results can, however, be used to include even the effect of the vertical component of the seismic inertial forces. The present formulation is based on the consideration of a curvilinear nonplastic trapped wedge below the footing base. By carrying out a detailed parametric analysis, the effects of different material shear strength parameters, overburden pressure, seismic forces, and foundation width on the bearing capacity factor $N_{\sigma }$ have been examined. With the changes in horizontal seismic acceleration coefficients, the slip line patterns have also been explored. The results from the present analysis compare quite well with that reported from studies available in the literature.

Practical Applications

While designing shallow foundations for a given structure, depending on the designed life of the structure, the values of the peak earthquake accelerations in horizontal and vertical directions can be estimated based on the geospatial location of the site and its past earthquake history. This manuscript provides the rigorous procedure and also establishes the design charts for determining the nondimensional bearing capacity factor in the presence of earthquake acceleration for the nonlinear power-law yield criterion; one of the primary advantage of implementing the nonlinear criterion is that it automatically incorporates the scale effects of foundations. By knowing the material parameters of the soil mass, applicable for the nonlinear power-law yield criterion, the ultimate bearing capacity of the foundation can accordingly be estimated from the established values of the bearing capacity factor in the presence of earthquake acceleration. The foundation of a given structure can, therefore, be designed by accounting for the reduction in the bearing capacity on account of pseudostatic earthquake inertial forces.

Full-scale tests were performed to study the penetration resistance of steel plates (skirts), which are common foundation elements of jacket offshore wind structures. Penetration resistance is well-studied in clays and sands, but there is limited information on penetration in gravels, which are typically used as the scour protection of critical elements like offshore wind substations. Direct extrapolation of penetration resistance in sands is not possible because of the grain-size effect. Two steel plate thicknesses and two gravel sizes were used to study the influence of the grain-size effect on the penetration resistance. Moreover, the importance of tip shape has also been evaluated by means of beveled tip tests. The results of the experimental tests showed a strong dependence of penetration resistance on penetration depth as expected, but also a significant dependence on skirt thickness and gravel grain size. A good agreement with experimental results has been found when analytically interpreting the penetration resistance using traditional bearing capacity formulas, but with an equivalent skirt thickness equal to the real skirt thickness plus the mean grain size, to account for the grain-size effect.

The response of suction caisson (bucket) foundations subjected to horizontal head displacement, or head rotation, is parametrically studied by means of three-dimensional finite-element analyses. The undrained clay stratum is either homogeneous or linearly inhomogeneous (Gibson soil). The effect of the nature of the interface between foundation and surrounding soil is explored with two different scenarios: an ideal case of a fully bonded contact (FBC), and a possibly more realistic tensionless and sliding interface of limited shear resistance (TSI). The latter scenario results in a significant reduction of failure loads. Closed-form expressions are developed for the maximum horizontal and moment capacity for a range of bucket aspect ratios in both soil types, and with both interface conditions. They are validated through comparisons with available results from the literature. The contribution of the suction caisson’s cylindrical sidewall shell to the overall response of the system is investigated. It is shown that for an embedment depth exceeding the caisson’s radius the shell provides practically the same lateral bearing capacity as the whole suction caisson, in contrast with the vertical (axial) loading of a caisson with sliding interface in which the role of the shell is much less significant.

Establishing a reliable value for the axial pipe–soil interface resistance is critical for the design of offshore pipelines. Over the last few years, several independent research groups have modified existing methodologies or devised new testing setups to further develop our understanding of the behavior of the pipe–soil interface at low contact stresses. The most common laboratory experimental methods adopted have been based on either tilt table tests or interface direct shear tests. However, a direct comparison between the results of these two testing methodologies has not been established. This paper aims at designing and fabricating a tilt table and interface direct shear setup capable of accurately estimating the drained interface resistance at low normal stresses, in addition to comparing their results under identical testing conditions. Both setups tested the drained clay–solid interface response by varying the soil composition (high and low plasticity clay), the interface roughness (smooth and rough), and the normal stress range. Results showed that the drained residual failure envelopes for the clays and clay–solid interfaces were nonlinear and could be modeled by a simple power model. The interface response was clearly dependent on the interface roughness, particularly when the roughness was normalized with the mean grain size. In the case of smooth interfaces, identical friction angles were obtained from the tilt table and the interface direct shear, whereas in the case of rough interfaces, the interface direct shear yielded lower friction angle values.

The effect of overconsolidation on the cyclic resistance ratio (CRR) for both non-plastic and plastic soils is examined using a laboratory test database, including cyclic triaxial, cyclic torsional, and cyclic direct simple shear (DSS) tests compiled from the literature. Based on the plasticity index ($PI$) and the ratio between water content during testing and liquid limit ($w_o/LL$), soils were divided into three series to interpret the relationship between CRR and overconsolidation ratio (OCR) using the stress history and normalized soil engineering properties (SHANSEP) approach. The resulting SHANSEP exponent $m$ was examined relative to key index parameters for each soil series. For non-plastic soils (Series I) in the DSS mode of shear, $m\approx 0.55$ for $CR{R}_{M=7.5}$ and is relatively independent of selected key index properties. This value is consistent with the typical value of $m=0.52$ defined elsewhere to describe the increase in undrained critical state shear strength ratio in monotonic loading with OCR for non-plastic soils subject to a similar consolidation profile. For low- to moderate-plasticity soils susceptible or moderately susceptible to liquefaction (Series II), $w_o/LL$ and liquidity index ($LI$) appear to roughly capture the trend of $m$ for $CR{R}_{M=7.5}$. For a limited number of higher-plasticity soils that are susceptible to cyclic softening (Series III), the range of $m$ for $CR{R}_{M=7.5}$ is relatively broad. Furthermore, the limited data suggested that Series III soils that are undisturbed (intact) or have low $w_o/LL$ and $LI$ may exhibit $m$ values that are significantly less than those measured for other reconstituted specimens over the same range of OCR.

Ring foundations are used to support tall and heavy circular onshore structures such as chimneys, cooling towers, storage tanks, and silos and offshore structures such as wind turbines and annular platforms. The present study focused on developing failure envelopes for ring foundations subjected to the combined loading of vertical ($V$), horizontal ($H$), and moment ($M$). Parametric three-dimensional finite-element limit analyses were carried out for circular and ring foundations resting on the surface of cohesive soil following the Tresca criteria. The failure envelopes were generated separately under $V:H$, $V:M$, and $H:M$ loading combinations. Variations in the ring foundation geometry ($R_i/R_o$) of 0.2, 0.4, 0.6, and 0.8 and linearly increasing soil heterogeneity values ($kB/s_{um}$) of 0, 1, 2, 3, 6, and 10 were considered in this study. The results indicated variations in failure loci with a variation in $R_i/R_o$ and $kB/s_{um}$. The typical contours of failure loads under the combined loadings and three-dimensional failure surface patterns are presented for the ring foundations with $R_i/R_o=0.2$ and 0.8 to understand the shape of the failure surfaces.

This paper presents the experimental results and analysis from two centrifuge experiments that simulated the seismic response of a gentle slope in soft clay. The two models consisted of a three-degree and a six-degree slope in soft clay, respectively, which are representative of typical slopes found on marine seabeds on the continental margins. The models were built in a laminar container in order to reproduce infinite slope boundary conditions. In-flight characterization investigations consisting of T-bar tests and air hammer tests were performed to obtain undrained shear strength profiles and shear wave velocities at various depths, respectively. A suite of earthquakes was applied, including sinusoidal waves and scaled real motions, in order to observe the response of the models in terms of the propagation of shear waves and the generation of lateral displacements at various depths in the slopes. The results showed that the model preparation approach ensures the repeatability of the experiments, enabling the evaluation of the impact of the slope angle on the seismic response of the gentle slopes studied. On average, the permanent displacements measured at the surface of the six-degree slope were three times greater than those measured at the top of the three-degree slope. In these slopes, nonlinear effects were observed in terms of the peak ground acceleration (PGA) that depended both on the slope angle and the intensity of shaking.

Five dynamic, large-scale centrifuge tests on pile-supported wharves were used to investigate the time- and depth-dependent nature of kinematic and inertial demands on the deep foundations during earthquake loading. The wharf structures in the physical experiments were subjected to a suite of recorded ground motions and imposed superstructure inertial demands on the piles. Partial to full liquefaction in loose sand resulted in slope deformations of varying magnitudes that imposed kinematic demands on the piles. It was found that the wharf inertia and soil displacements were always in phase during the critical cycle when bending moments were at their maximum values. The test results were analyzed to provide the relative contributions of peak inertial loads and peak soil displacements during critical cycles, and the data revealed the depth dependency of these factors. The results of this study are used in a companion paper to provide recommendations for the design of pile-supported wharves subjected to foundation deformations.

An equivalent static analysis (ESA) procedure is proposed for the design of pile-supported wharves subjected to combined inertial and kinematic loads during earthquakes. The accuracy of the ESA procedure was evaluated against measurements from five large-scale centrifuge tests. The wharf structures in these tests were subjected to a suite of recorded ground motions and the associated superstructure inertia, as well as earthquake-induced slope deformations of varying magnitudes. It is shown that large bending moments at depths greater than 10 pile diameters were primarily induced by kinematic demands and can be estimated by applying soil displacements only (i.e., 100% kinematic). In contrast, the large bending moments at the pile head are primarily induced by wharf deck inertia and can be estimated by applying superstructure inertial loads at the pile head only (i.e., 100% inertial). Large bending moments at depths shallower than 10 pile diameters are affected by both inertial and kinematic loads; therefore, evaluation of pile performance should include soil displacements and a portion of the peak inertial load at the pile head that coincides with the peak kinematic loads. Ranges for inertial and kinematic load combinations in uncoupled analyses are provided for different soil profiles. The details on the back-calculated load combination factors are provided in the companion paper.

Muskeg soil is widespread in Canada. It covers around 15% of the Canadian landscape. Its problematic nature is attributed to its high compressibility and low shear strength when subjected to loads because of its high initial void ratio and water content. Therefore, in this study, microbially induced calcite precipitation (MICP), an emerging and potentially environmentally friendly technique for soil stabilization, is used for enhancing the compressibility and shear strength properties of muskeg soil. The urease active bioslurry approach is adopted in this study, which comprises the mechanical mixing of bioslurry with soil and the injection of cementation solutions in subsequent phases. Muskeg soil was collected from Bolivar Park, Surrey, British Columbia, Canada. Different bioslurry concentrations were tested for the compressibility properties to determine the optimum concentration. Afterward, the optimum concentration was used to check the effect of the bioslurry percentage by weight and the number of cementation solutions injected on the soil stiffness and strength. Microstructure analysis by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were conducted for untreated and treated samples to check the change in the soil microstructure due to stabilization. The results showed that the $0.4\mathrm{mol}/\mathrm{L}$ bioslurry concentration demonstrated the best compressibility properties.

The response of an inhomogeneous soil layer with exponentially varying stiffness with depth is explored using one-dimensional viscoelastic wave propagation theory. The governing equation is treated analytically, leading to an exact harmonic solution of the Bessel type. Both positive and negative velocity gradients are examined using a pertinent dimensionless parameter. It is shown that (1) for positive stiffness gradients, strains attenuate with depth faster than displacements that, in turn, attenuate faster than stresses; and (2) close to the soil surface, curvatures are controlled by acceleration, whereas they are controlled by strain at depth. The fundamental natural frequency of the layer compares well against approximations on the basis of the Rayleigh quotient. Novel asymptotic and ad hoc approximate solutions for the base-to-surface transfer function are proposed, providing good alternatives to the complex exact solution at both high and low frequencies. New expressions are derived relating (1) shear strain and peak particle velocity; and (2) curvature and peak ground acceleration close to the soil surface. A full-domain approximation is provided, allowing the practical implementation of the specific velocity model. Numerical examples are presented.

This paper presents the results of load and resistance factor design (LRFD) calibration of the facing limit states for soil nail walls. The current AASHTO facing load model and a modified model together with the AASHTO facing resistance models for both permanent and temporary facing load cases are considered. The facing design includes flexure, punching shear, and headed-stud tensile limit states. The calibration of resistance factors captures uncertainty in the accuracy of the load and resistance models, uncertainties in the nominal load and resistance values at time of design, and bias dependencies between model bias and nominal values. Resistance factors are calibrated for a range of load factors and target reliability indexes. Example designs for facing limit states demonstrate the implementation of the calibrated resistance factors in a LRFD framework using the current AASHTO and modified load models for the permanent facing load case. The practical values of this study are calibrated load and resistance factors for facing limit states of soil nail walls that are of interest to code writers for future editions of LRFD codes in the United States and Canada.

This study presents a novel geotechnical engineering approach that utilizes naturally occurring processes to reduce soil permeability in-situ. This approach is inspired by a soil stratification process (Podzolization), where a low permeability layer is formed by metal-organic matter precipitates. In a field experiment, a direct aluminum-organic matter (Al-OM) floc injection was applied to create a continuous vertical flow barrier in a dike. Direct injection uses the shear-dependent size of Al-OM flocs. High-shear conditions (i.e., during injection) lead to the breakage of Al-OM flocs and thus allow their transportation in soils. When the injection stops and low-shear conditions prevail, the Al-OM flocs re-grow in size and block the pores, which ultimately reduces soil permeability. Two different Al-OM floc concentrations were applied in the field. Results show that a continuous flow barrier is only formed at lower concentrations; at higher concentrations a scattered permeability reduction was achieved. This demonstrates the viability of this approach in reducing soil permeability in-situ and shows that the spatial distribution of the flocs depends on input concentration.

Pulse-like earthquakes are believed to impose larger structural demands on structures due to the sudden release of seismic energy. This can cause concern in areas that are near faults due to the possibility of structures not being designed to withstand higher seismic demands and could be significant for embedded retaining walls in nuclear power plants. A finite element model of a soil-embedded wall is developed to examine the non-linear response of this system to pulse-like earthquake ground motions. For the finite element analysis, the open-source program OpenSees version 3.3 is used for the simulation of an embedded rigid retaining wall. The analyses are performed using records that match narrow-band modified target spectra for different moment magnitude scenarios ranging from 5.03 to 7.70. The results from pressure methods will be compared with the full non-linear finite element model results. Generally, it is observed that this type of earthquake imposes larger demands on an embedded rigid retaining wall, but the magnitude of the demand is still comparable to normal ground motions.

The influence of the pile installation by vibratory or impact driving on the response to subsequent cyclic lateral loading, as faced in the offshore environment, is investigated numerically. Large-deformation analyses of the pile installation process using the coupled Eulerian–Lagrangian method considering partially drained conditions are performed. Following the installation, one million lateral load cycles are simulated using the high-cycle accumulation (HCA) model. The lower the hydraulic conductivity of the soil during driving, the higher the accumulation of lateral deformation when the pile is subjected to high-cyclic loading. The assumption of ideally drained conditions during pile driving results in a lower accumulation, in particular for the vibratory-driven pile. Compared to the influence of the drainage conditions during driving, the influence of the installation method is found to be of less importance. While the vibratory-driven piles tend to give less resistance to monotonic lateral loading for most conditions, slightly lower permanent pile head rotations after one million lateral loading cycles are observed compared to the impact-driven piles.

With the recent advances in the biogeotechnics field and specifically microbially induced calcite precipitation (MICP), cone penetration testing (CPT) has become a valuable tool to overcome the challenges associated with intact sampling of improved soils, evaluate the spatial extent and magnitude of the applied MICP treatment, and assess the consequential improvement of engineering properties. Although the CPT cone tip resistance ($q_c$) can effectively monitor the improvement of densified clean sands, no relationship exists to estimate cementation and strength parameters in MICP-treated sands. This paper proposes a relationship between the apparent cohesion ($c$) stemming from the MICP-induced cementation bonds at particle contacts and the change in tip resistance $\mathrm{\Delta }{q}_c$ in initially loose sands. To develop a broadly useful correlation, available experimental CPT data in biocemented soils were used to guide computation simulations using a direct axisymmetric model of cone penetration in biocemented sands. The CPT numerical model uses the finite-difference method with a rezoning algorithm for large-deformation problems along with the Mohr-Coulomb constitutive model. The biocemented sand was characterized by Mohr-Coulomb strength parameters and an elastic shear modulus informed by shear-wave velocity measurements ($V_s$). The correlation parameters of interest were identified ($c$, $q_c$, and $V_s$), and results of the numerical simulations were validated against available experimental data. Once validated, the numerical simulations were extended to different initial conditions, and the trends between parameters of interest were analyzed and interpreted. Results from the simulations are consistent with experimental data and show an increase in the cone tip resistance as the cementation level increases. The cementation level is modeled through apparent cohesion and the shear stiffness model parameters, which both increase as the cementation level increases. A linear relationship is proposed between the apparent cohesion and the change in cone tip resistance as a function of the confining stress.

Several widely used field methods for estimating postliquefaction ground deformation are based on the laboratory data from one series of cyclic simple shear tests performed on one uniform clean sand reconstituted to three relative densities. It is not clear if the trends of this one data set are applicable to other clean sands, nonplastic silty sands, and nonplastic silts. A database of 579 test results on postliquefaction volumetric strain, including 299 test results that relate maximum shear strain to the factor of safety against liquefaction triggering, was compiled and used to examine trends for these soils. The database includes postcyclic test data on 10 clean sands, 2 gravels, 3 silty sands, 5 silts, and 3 clayey soils. The enlarged cyclic testing database was used to develop models that estimate postliquefaction volumetric strain and maximum shear strain as a function of soil type, state, and seismic demand. The models are applicable to uniform nonplastic soil. The state parameter was used in addition to relative density and void ratio to characterize the state of the soil. Correlations between these parameters enable the full data set to inform the models.

A number of research studies have recognized that not all particles in a sand specimen are active in stress transmission, particularly in the case of gap-graded soils. This has implications for the use of the global void ratio ($e$), and variables/parameters that depend upon $e$, to predict the influence of the state on the mechanical behavior of gap-graded soils. This study explores the possibility of comparing the shear stiffness determined in dynamic wave propagation tests ($G_{dyn}$) with stiffness values determined in small-strain probes ($G_{sta}$) to assess the extent to which all the particles in a specimen are actively engaged in stress transmission. The idea is initially developed using three-dimensional discrete element method simulations and considering ideal specimens. The practical application of this approach is then tested in a series of drained triaxial compression tests. The numerical studies considered both specimens with continuous, linear particle size distributions as well as gap-graded soils. The results show that the ratio $G_{sta}/G_{dyn}$ may be associated with the ratio between the bulk density calculated considering only the stress transmitting particles, ${\rho }_m$, and the bulk density calculated considering all particles, $\rho$. The ratio ${\rho }_m/\rho$ is determined by the proportion of inactive particles, which varies with the proportion by mass of finer particles in the soil ($F_{\mathrm{finer}}$) for gap-graded soils. The relationship between $G_{sta}/G_{dyn}(e)$ and $F_{\mathrm{finer}}$ enables a qualitative assessment of the proportion of inactive particles. The corresponding experimental test results show a similar but weaker correlation between the ratio of $G_{sta}/G_{dyn}$ and $F_{\mathrm{finer}}$, this weaker correlation may be attributed to the differences between the simulations and the experimental conditions. However, despite the challenges with experimental implementation, the data presented here support the idea that it may be possible to qualitatively estimate the proportion by volume/mass of inactive particles in physical samples by comparing the stiffness results of static and dynamic testing.

This paper presents the results of nonlinear deformation analyses of an embankment on a spatially variable, liquefiable foundation soil reinforced with spatially variable soil-cement (SC) wall. The objective is to evaluate the merit of employing stochastic modeling approaches, such as spatially correlated random fields, relative to deterministic analysis with uniform properties for the soil and SC wall. Spatial variability, which is specified by mean, coefficient of variation (COV), and scale of fluctuation (SOF), can significantly influence the seismic performance of soils and embankments. The numerical analysis was first validated using data from a dynamic centrifuge test conducted at the Center for Geotechnical Modeling at University of California, Davis. Analyses were performed for different sets of realization of the foundation soil and SC wall as well as the range of the length and strength of SC wall and peak base acceleration. Simulation results of the stochastic models with spatially Gaussian random field were examined and compared with the results of the experiment with an emphasis on the crest vertical displacement, berm horizontal displacement, and contours of shear strain in the embankment, foundation soil, and SC wall. The results revealed that the representative percentile of unconfined compressive strength ($q_{ucs}$) in the range of 35th–50th percentile needed to be used in a uniform model to estimate the median of crest and berm displacement in spatially variable SC wall-supported embankment.

A series of centrifuge tests were performed to evaluate the backward erosion piping behavior that occurred in models with the same soil and same dimensions and to investigate the influence of the seepage length, exit-hole size, and gravitational acceleration. Pore-pressure measurements at various locations within the model, along with video recordings, were used to analyze the models. The mechanism began with seepage across the model, followed by emerging seepage, which changed the flow direction toward the exit hole. The mechanism developed steadily for models with shorter seepage lengths, allowing identifying soil loosening, the initiation of erosion, and failure. In comparison, the mechanism developed rapidly in models with longer seepage lengths, without a clear progression. The values of critical hydraulic gradients across the upstream and downstream reservoirs, the seepage length of the models, and near the exit holes were similar, regardless of the seepage length. The critical hydraulic gradients decreased as the gravitational acceleration increased, indicating some scaling effects. Regardless, the overall effect of centrifuge gravity on the critical hydraulic gradients was small compared with the range of values that have been reported in the literature.

Dual row retaining walls can be used as embankment structures and coastal defense against wave or even tsunami loads. However, their resiliency to a preceding earthquake and liquefaction of the foundation soil is not well understood. In this paper, dynamic centrifuge modeling is used to investigate the seismic response of a dual row retaining system where the walls are founded in a loose, saturated, and level deposit susceptible to earthquake-induced liquefaction. A combination of instrumentation techniques, ranging from measurements of the wall bending and displacements to the pore pressures and horizontal earth pressures acting on the walls, are used to elucidate the mechanics of the soil-structure system. The experiments reveal that the cyclic loading of PGA $0.4\mathrm{g}$ does not induce a catastrophic collapse. An understanding of the liquefaction phenomena, including shear-induced dilation and coseismic migration of the pore fluid toward a region of relative suction between the walls, is required to interpret the observed resilience of the wall-soil system to liquefaction. A ratcheting mechanism for the wall deformations, consistent with the coseismic measurements of the soil and structural response, is proposed. For the geometries tested, the findings challenge conventional conservative design recommendations, such as the need for sheet-pile walls to extend beyond a liquefiable layer to prevent the liquefaction-induced collapse of dual row wall systems.

In this study, the effect of fluctuating groundwater level (GWL) on the settlement of footing foundation placed on sand was investigated based on the results obtained from centrifuge tests. In the tests, rising and falling phases of GWL were both considered, and the values of footing settlement ($s_{ft}$) obtained from each phase were compared. The centrifuge testing program was designed with a specifically manufactured test box and hydraulic control system. Image-based particle-displacement analysis using particle image velocimetry (PIV) was performed to capture inner soil particle movement during GWL fluctuation. Ground subsidence occurred most significantly during the first GWL fluctuation. Fluctuating GWL caused considerable $s_{ft}$ while load was unchanged. $s_{ft}$ was larger for rising GWL than for the falling phase and decreased as the number of GWL fluctuation increased. PIV analysis indicated that GWL-induced settlement was not uniform but larger within higher-loaded zone below footing, even if GWL changed uniformly and load on footing was unchanged. The collapse potential was introduced to describe and explain GWL-induced footing settlement, which was consistent with the results observed from the centrifuge tests.

Field trials of microbially induced desaturation (MID) were conducted at two sites in Portland, Oregon underlain by liquefiable fine-grained soils. MID is an emerging method for mitigating the potential for triggering liquefaction. MID treatment stimulates native denitrifying microbes with a solution containing nitrate, as well as other substrates and nutrients. An end product of the denitrification reactions is nitrogen gas, which displaces soil porewater and in turn reduces the in situ degree of saturation (${\mathrm{S}}_{\mathrm{r}}$). Because during cyclic loading desaturated soils produce less excess porewater pressure than saturated soils, MID can mitigate the potential for triggering liquefaction. Monitoring for the two field trials was performed to evaluate the MID treatment performance and the associated subsurface desaturation. Monitoring data included seismic wave velocities measured with crosshole and downhole techniques, embedded in situ moisture and electrical conductivity sensors, water chemistry measurements, and recovery and testing of samples for changes in soil properties. Monitoring data were collected pretreatment, during treatment, and post-treatment, and then interpreted to evaluate the effectiveness of MID for reducing ${\mathrm{S}}_{\mathrm{r}}$ in fine grained, low plasticity silts in the two distinct sites. Despite geotechnical site characterization data that show the field trial sites have distinct geotechnical characteristics, including interbedding, that affect liquefaction susceptibility and MID treatment application, results indicate liquefiable soil at both sites was successfully desaturated and that the desaturation persisted for at least 92 days post-treatment.

Traditional interpretation and interpolation techniques have been extensively used in conjunction with geotechnical in-situ tests to evaluate subsurface conditions; however, these approaches, when applied at highly variable geomaterial sites, can lead to high uncertainties and inaccurate subsurface characterization. This paper presents the application of a proposed framework that combines geotechnical in-situ test data and a geostatistical modeling approach with visualization techniques to provide an advanced three-dimensional (3D) site characterization and visualization of an aging hydraulic fill dam. There were 66 cone penetration tests (CPT) performed along the crest, downstream, and upstream sides of the hydraulic fill dam and properties, such as the soil behavior type index ($I_c$), effective friction angle (${\varphi }^{\prime }$), and undrained shear strength ($S_u$), were determined using traditional CPT data correlations. Univariate statistics performed on the properties revealed high variability in the hydraulic fill dam configuration. Anisotropic semivariogram models were developed to incorporate the spatial variability and the directional anisotropy of soil properties in the proposed site characterization approach. A 3D kriging interpolation was then performed based on the anisotropic semivariograms to generate 3D geotechnical visualization models of the $I_c$, ${\varphi }^{\prime }$, and $S_u$ of the geomaterials encountered in the dam. Validation studies were performed by comparing the 3D interpolated soil properties with the ground-truth measured values obtained from laboratory tests. The visualization models based on a geostatistical interpolation approach can facilitate the identification of critical zones within the dam that could be susceptible to geotechnical hazards. This paper highlights a novel approach combining the in-situ data, 3D interpolation kriging analyses, and visualization techniques to evaluate the soil configuration within highly heterogeneous sites such as hydraulic fill dams and mine-tailings sites.

Laponite is a nanomaterial that can modify the behavior of the fluid in which it is dispersed, transforming it into a non-Newtonian fluid with initial low viscosity that hardens with time. Additionally, since the gel recovers after shear stress has been removed, it has resilient properties. In this study, several series of laboratory element testing, such as oedometer, drained, and undrained tests, were performed to assess the effect of adding 1% laponite on the geotechnical properties of loose saturated sand. The results of one-dimensional consolidation tests indicated that the addition of laponite did not influence the compressibility of the host sand, but monotonic undrained tests showed that laponite could reduce friction between particles. Furthermore, the laponite’s ability to recover was evaluated by subjecting the treated samples to a series of three cyclic loading phases. These specimens require up to 100 times more cycles to liquefy compared to untreated sand specimens with a similar relative density.

Foundation bearing capacity has been well studied in homogeneous soil under a condition of embedment depth within five times the foundation effective characteristic length. However, the penetration depth of deep-sea anchoring foundations can be far more than five times the effective characteristic length. This study aims to investigate the vertical bearing capacity of the strip, circular, and conical foundations within a large embedment depth range in normally consolidated clay. Parametric studies were conducted to analyze the effect of soil nonhomogeneity and foundation–soil interface roughness with the aid of the finite-element method combined with a developed subroutine. Results show that no critical value was found for the vertical bearing capacity even at a large embedment depth. The embedment depth also influences the relationship between the soil nonhomogeneity and the foundation bearing capacity factor, $N_c$. Friction coefficient has a great influence on $N_c$ of the conical foundation. Comprehensive formulas for calculating $N_c$ of the three common foundations are proposed based on parametric studies. The simple formulas will provide a reference for geotechnical engineers.