Journal of Geotechnical and Geoenvironmental Engineering

Groundwater seepage and an increased lateral earth pressure coefficient at rest ($K_0$) increase the potential for triggering large-scale landslides in sensitive clays. After the failure is triggered, the successive retrogressive failure of soil blocks in the undrained condition is influenced highly by $K_0$. This paper presents the numerical techniques for modeling seepage and $K_0$ using an Eulerian-based large deformation finite-element method. The finite-element simulation was performed first for a drained condition to calculate the in situ effective stresses and seepage forces, which then were used to model subsequent undrained retrogressive failure in total stress, triggered by toe erosion. A strain-softening- and strain-rate-dependent undrained soil strength model, which captures the behavior of soil failure from its intact condition to the fluidlike remolded material flow, was adopted in the retrogressive failure analysis. The simulation covered different phases of the landslide, including the initiation and retrogression of failure, and debris flow. Using the developed numerical technique, the 2010 Saint-Jude landslide in Quebec, Canada, was simulated.

Two of the conventional methods to improve soft soil deposits are evaporative dewatering and accelerated consolidation of the deposits using prefabricated vertical drains (PVDs). Evaporative dewatering is limited in application to densification of the surficial layers providing little to no improvement of the soft consistencies that lie at the bottom of the deposit. Development of smear zones around PVDs has been understood to affect their efficacy. To this end, this paper discusses a novel method of dewatering using controlled evaporation through ventilated wells [the ventilated well method (VWM)] that traverse the thickness of the deposit. Air, under controlled conditions, is circulated inside the perforated well, which progressively drives the moisture out of the soil skeleton. This is accompanied by development of an internal stress (suction) condition in the soil system leading to its densification. First, the paper introduces the method and discusses its underpinning physical principles and a laboratory-scale implementation of the VWM. Next, a systematic parametric study was carried out to understand the corresponding effects on the efficacy of the VWM due to varying dimensions of the well and the testing mold, rate of the air flow, and soil and pore fluid properties. Based on the laboratory-scale investigations, it is observed that the VWM performed better than surficial evaporative dewatering. The method is transferrable to the field and has a great potential in ground improvement exercises involving soft deposits such as those encountered in dredged sediments, mine tailings, and fluidized industrial waste.

This experimental study focused on cyclic degradation and cyclic pore-water pressure response of high-plasticity compacted clay under different dynamic loading and initial static shear stress conditions. The strain-controlled undrained cyclic simple shear tests were performed at different initial static shear stress ratios (${\tau }_s/S_u=0$, 0.45, 0.65, 0.79, and 0.87), cyclic strain amplitudes (${\gamma }_c=0.5\%$, 1.5%, 2.5%, and 3.75%), and frequencies ($f=0.1$, 0.5, 1, and 2 Hz). The results revealed that the initial static shear stress significantly increased the magnitude and rate of stiffness degradation and cyclic pore-water pressure generation. The mobilized shear stress under cyclic loading decreased below the static shear strength within only five loading cycles. The shear modulus increased and the damping ratio decreased with the increase in frequency and decrease in cyclic strain amplitude. The enhanced rate of stiffness degradation followed a power-law functional relationship with cyclic strain amplitude, and its trend was dependent on the magnitude of the initial static shear stress ratio and the cyclic strain-reversal conditions. The experimental results clearly demonstrated the coupling between cyclic degradation and pore-water pressure generation. A strain-based model was formulated for the risk assessment of compacted high-plasticity clay (CH soil) subjected to combined static and cyclic loading.

This study presents the results from a series of centrifuge modeling tests conducted to investigate the backward erosion piping across a sandy foundation underlying an impervious cohesive layer with a defined exit hole. Different levels of centrifuge gravitational acceleration and various exit hole sizes were tested. The behavior at different phases of erosion was analyzed based on in-flight video recordings and posttest observations, along with local and global pressure loss measurements. Results showed that the overall mechanism that was modeled was similar to the mechanism described in previous small-scale experimental studies. The results showed that the exit hole size had minimal impact on the critical hydraulic gradient but affected the characteristics of the piping path and the amount of eroded material. The critical hydraulic gradient that initiated the erosion decreased slightly as the centrifuge gravitational acceleration increased. The values of the critical hydraulic gradient, which was studied locally and globally, ranged between 0.15 and 0.40, and fell within a range of estimates from typical analytical methods. This study provides a means to improve the testing protocol and analysis of centrifuge modeling of internal erosion mechanisms, which currently is limited in the literature.

Wildfires and associated wetting-induced slope stability issues (i.e., erosion, shallow landslides, and debris flows) are common problems all around the world. The water-retention mechanism of the burnt soil after a severe wildfire is adsorption followed by capillary condensation as saturation increases. During this time, soil is more susceptible to runoff-dominated erosion and associated debris flows. The water vapor sorption behavior of wildfire-burnt soil and wildfire ash is not fully known. This study investigates the evolution of water vapor sorption behavior of wildfire-burnt soil over a year and the impact of wildfire ash on the sorption behavior of burnt soil. Soil samples were collected from the surface and from 50-cm depth, and ash samples were collected from the surface at varying times after the 2019 Williams Flats Wildfire in Colville Indian Reservation, Washington State. Soil water retention curves of the surface soil and 50-cm soil were measured using a potentiometer. Hysteretic water vapor sorption isotherms were obtained along adsorption and desorption paths using a dynamic water vapor sorption analyzer. Several different parameters including maximum adsorbed water content, degree of hysteresis, specific surface area, and transition relative humidity were calculated from water vapor sorption isotherms and used to evaluate the sorption behavior of wildfire-burnt soil and wildfire ash. The results indicate that (1) wildfire ash is hydrophilic, has an active surface, and contributes to water retention; and (2) spatial redistribution of ash may result in fluctuations in the water retention of burnt soil over time.

The paper compares the performance of two FEM approaches in reproducing the response of bare frame structures to tunneling in dry dense sand. A fully coupled approach, in which the tunnel, frame, and soil are accounted for, is compared with a two-stage method incorporating simpler structural and soil models. The two approaches are validated against centrifuge test results of tunneling in sand beneath frames founded on either rafts or separate footings. Both approaches provide good estimates of displacements and distortions experienced by the frames provided that the soil-foundation interface and structural stiffness are correctly accounted for. The numerical models are also employed to extend the range of eccentric configurations investigated with centrifuge tests. The results demonstrate that shear deformations play an important role for all considered buildings, whereas only frames on separate footings are sensitive to horizontal ground movements. Finally, data are synthesized using modification factors and recently proposed relative stiffness terms.

Microbially induced calcite precipitation (MICP) is currently appraised to improve sandy soils, but only a few studies use it to solidify loess soil. MICP solidification tests and undrained cyclic triaxial tests were conducted to study the liquefaction resistance of MICP-solidified loess soil samples. The results showed that because calcium carbonate (${\mathrm{CaCO}}_3$) cemented loess soil particles and filled voids in samples, the permeability coefficients of treated samples all decreased. However, the change pattern of the permeability coefficient of samples treated with various conditions was different. For the solidified samples, the liquefaction resistance was improved significantly, and increased treatment cycles resulted in the improvement of the liquefaction resistance. Adding bacterial suspension and the cementation solution together made the sample with initial density of $1.4\mathrm{g}/{\mathrm{cm}}^3$ have higher liquefaction resistance. However, for samples of 1.5 and $1.6\mathrm{g}/{\mathrm{cm}}^3$, adding bacterial suspension and the cementation solution separately also achieved better liquefaction mitigation effects. Increasing total solution volume per treatment cycle improved the liquefaction resistance of the solidified samples. With the increase of ${\mathrm{CaCO}}_3$ content, the number of cycles before liquefaction ($N_L$) and residual strength (${\tau }_r$) exponentially increased, while the damping ratio ($D$) exponentially decreased. Moreover, the linear corrections between specific gravity and ${\mathrm{CaCO}}_3$ content, $N_L$, ${\tau }_r$, and $D$ can be established for MICP-solidified loess soil. In addition, significant corrections also existed between plasticity index and ${\mathrm{CaCO}}_3$ content, $N_L$, ${\tau }_r$, and $D$. Results in this work had a great significance and provided the foundation for the application of the MICP technique for liquefaction mitigation of loess soil.

The present paper addresses the influence of shape, size, and frictional characteristics of granular materials by utilizing X-ray computed tomography (CT) imaging and FEM. High-fidelity triaxial shearing simulations are conducted on a realistic assembly of sand grains. Applicable boundary conditions are represented, including the latex membrane for applying confining pressure. For this research, two poorly graded clean sands (SP) with distinct grain morphologies of round and angular particle shapes are considered. The effect of the particle size is naturally embedded in two materials with a difference of small size fraction grains present in angular sand. The deviatoric stress and volume change response increase up to the value of friction coefficient ($\mu$) equal to 0.5 for rounded sand, and the strength-deformation response is unaffected by a further increase in friction. The axial strain, corresponding to peak deviatoric stress, did not depend on the friction value for identical initial microstructure and boundary conditions. The microscale investigation suggests a similar mean coordination number and percentage of grains with a coordination number less than two for friction values producing similar responses. The angular sand resulted in higher strength and low dilation compared to the rounded sand for friction value that best reproduces experimental results. The strength increase due to the particle shape effect becomes less pronounced for smooth grains. The grain-scale analysis indicates angular sand exhibits less dilation in contrast to the general observation in the literature due to smaller grain fractions absent in rounded sand, highlighting the need to introduce additional subclassifiers in classifying SP sands. The localized deformation pattern remains unchanged with friction and varies with grain shape. An attempt is made to link micromechanical insights to the macroscale response.

Permanent sliding displacement is a parameter that is used widely to evaluate the seismic performance of earthen slopes, and the inherent variability of soil strength parameters is considered simply using a logic tree in current practice. This study thus proposes a fully probabilistic framework to assess the seismic displacement hazard of earthen slopes by quantifying the inherent spatial variability of soil strength parameters. The framework incorporates the random field theory and a multiple quadratic response surface (MQRS) model into the fully probabilistic seismic sliding displacement hazard analysis. Random field theory was employed to characterize the spatial variability of soil parameters, and the MQRS model is proposed to estimate the yield acceleration ($k_y$) of slopes in an efficient way. The performance of the proposed framework was demonstrated by slope examples. The results indicated that (1) the predicted $k_y$ values of the MQRS model are comparable with those computed by the traditional pseudostatic procedure, validating its accuracy in applications; (2) slope strength parameters exhibiting a weaker spatial variability (larger scale of fluctuation) yield a larger dispersion of $k_y$ and a larger displacement hazard; and (3) a larger displacement hazard is produced for soil parameters exhibiting weaker correlation between cohesion and friction angle. The proposed framework enables assessment of the probabilistic seismic displacement hazard of earthen slopes with proper consideration of the spatial variability of soil parameters.

The implementation of unmanned aerial vehicles (UAVs) in civil engineering has primarily focused on remote sensing using optical cameras, light detection and ranging (LiDAR), and communicating with other sensing systems such as wireless sensor networks. However, UAV-enabled methods for subsurface characterization are still at their naissance. In this study, a UAV was used to lift and drop a mass onto the ground surface. The mass’s impact on the ground was used as the impulsive source for multichannel analysis of surface waves (MASW) testing. For this implementation, a hexarotor UAV was modified to lift and drop 4–7 kg masses to generate Rayleigh surface waves. The frequency domain characteristics of the seismic waves generated by UAV-dropped masses were compared to conventional MASW testing using a sledgehammer. The MASW method using a UAV-deployed source developed herein was applied to a soil site and a solid waste site. It was demonstrated that the UAV-dropped mass can generate Rayleigh surface waves below 10 Hz more effectively than the sledgehammer and could therefore support shear wave velocity profiling to greater depths in the subsurface, possibly without the need for signal stacking. Recommendations for drop mass selection and a discussion of observations made by the authors are also provided. Contributions made in this study are intended to contribute toward remote, fully autonomous subsurface mapping coupled with image-based surface mapping that will be critical for remote site characterization in postearthquake geotechnical reconnaissance and will allow the acquisition of more extensive subsurface data than presently feasible.

China National Offshore Oil Corporation (CNOOC) currently is developing a mat-supported wellhead production platform concept as an alternative solution to conventional jacket platforms in shallow-water oil fields. The platform is towed to the site with the mat foundation elevated. The mat then is lowered and embedded in the seabed as the hull is jacked out of the water. Steel pipe piles subsequently are driven through the tubular legs of the platform. After grouting the connection, the pile foundations provide permanent support for the platform. The mat foundation therefore provides only temporary support to the platform. This paper presents a case study focusing on the installation behavior of the mat foundation in a soft soil site as part of the platform concept development and suitability evaluation. The study determined (1) the expected penetration depth under the platform’s self-weight considering its irregular geometry and soft over stiff clay stratigraphy; (2) the target center of gravity to achieve even penetration and the potential for tilt development in the case of offset from the target position; (3) the effectiveness of using ballast tanks to correct the tilt; and (4) settlement after the installation due to dissipation of pore pressure and creep. Advanced large-deformation finite-element simulations featuring a strain softening soil model and analytical analyses were performed. A dedicated lab testing program geared was designed and executed to provide the necessary soil parameters for the analyses. This paper presents the techniques and considerations that were applied in this study and insights gained into the installation and subsequent postinstallation behavior of large-area mat foundations.

The response of sands stabilized with colloidal silica aqueous gel is investigated in the laboratory. The role of colloidal silica on subsequent sand behavior is examined with the aid of monotonic and cyclic loading tests so as to establish the mechanical response of the treated sand. Depending on the loading conditions when the strength of the treated sand is enhanced and liquefaction is averted, its stiffness may reduce and its compressibility increase. This contradictory behavior is investigated on the basis of an extended database including direct shear, triaxial, and normal compression tests. Initial stiffness is lower for treated sand compared with untreated sand under drained and undrained monotonic loading conditions. It is demonstrated that only dense treated sand shows similar stress-strain properties with the untreated sand under cyclic loading, whereas loose treated sand accumulates strain and excess pore-water pressure much faster than the untreated sand. The critical state line applying to the treated sand lies substantially above that manifested by untreated sand. The two lines converge as the stress level increases to around 2,000 kPa.

The thermal conductivity function (TCF) is an important constitutive function establishing the thermal conductivity–water content relationship in unsaturated soils. The existing TCFs do not account for the effects of confining pressure, nor do they consider thermal induced changes in pore structure and degree of saturation. This study presents a general TCF by considering the temperature effects on pore structure, degree of saturation, different heat transfer mechanisms (i.e., conduction, convection, and latent heat of vaporization), and the confining pressure. The TCF is linked to a temperature-dependent soil water retention curve (SWRC) model to include the impact of temperature on pore structure and degree of saturation. The proposed model applies a decay function to the degree of saturation to account for thermally induced changes in heat transfer mechanisms through conduction and convection of pore water in both liquid and vapor phases and latent heat transfer due to vaporization. A new function is introduced into the TCF to incorporate the effects of confining pressure on thermal conductivity that corresponds to the void ratio changes. The proposed TCF was validated against experimentally measured data for several different soils at zero confining pressure and one soil at various confining pressures reported in the literature. The comparison showed that the proposed TCF can capture laboratory-measured data properly, with prediction errors significantly lower than those from several alternative models.

Over the last three decades, cutoff walls using soil mix technology have been developed and deployed to deliver in situ containment of contaminated sites. The aggressive contaminated soil environment imposes significant long-term stresses on wall materials, and underground cracking is very difficult to detect and can compromise the integrity of walls. A recent relevant development is the concept of self-healing materials that can be triggered by damage and self-heal without the need for external intervention. This laboratory study developed, for the first time, a microcapsule-based self-healing soil mix cutoff wall material and demonstrated its performance in the healing processes, recovery of compressive strength, and hydraulic conductivity. The developed microcapsule-based cementitious grout was mixed with a sand soil using a laboratory-scale auger, and the embedded microcapsules were triggered upon cracking and released a sodium silicate cargo that healed the cracks. Micro–computed tomography (micro-CT) scan analysis verified the good survivability and uniform distribution of the microcapsules during the auger mixing process. Scanning electron microscopy–energy dispersive X-ray spectroscopy (SEM-EDX) and thermogravimetric analysis (TGA) revealed that the released sodium silicate microcapsule cargo reacted with the cementitious matrix to produce healing products in the form of calcium silicate hydrates. The microcapsule-containing posthealing specimens regained 44% of initial compressive strength and showed a recovered hydraulic conductivity only slightly higher than that of the undamaged specimens. The results demonstrated the great potential of microencapsulated sodium silicate as a self-healing agent for cement mixed soil, which could provide more resilient and reliable soil mix cutoff walls.

Preliminary estimations of shaft resistance of rock-socketed piles are usually conducted using empirical formulations that relate to the uniaxial compressive strength (${\sigma }_c$) of the weaker material involved (intact rock or pile). However, there are other factors, such as the degree of socket roughness, that could affect the shaft resistance of rock-socketed piles. In this paper, results from geotechnical centrifuge tests are presented to demonstrate the effect of socket roughness on the pile shaft resistance. Aluminum model piles with different degrees of shaft roughness were fabricated and embedded within an artificial rock mixture composed of sand, cement, bentonite, and water. Pile loading tests were conducted within the centrifuge and axial forces along the model piles were measured using fiber Bragg grating (FBG) sensing technology. Results are used to demonstrate that centrifuge testing provides a suitable experimental method to study and quantify the effect of socket roughness on the shaft shearing mechanism of rock-socketed piles. Finally, the centrifuge test measurements are compared with several formulations published in the literature, suggesting that centrifuge measurements tend to agree with the overall trend, despite the variability of predictions obtained with different formulations.

This paper presents an experimental study on the uplift behaviour of both pipes and strip plate anchors buried in sand. A total of 24 plane-strain uplift tests were performed using an image-based deformation measurement technique, by which the influences of anchor/pipe embedment ratio, sand relative density and pipe roughness on the load-displacement responses and associated failure and deformation mechanisms were systematically investigated. It was observed that the overall uplift responses of pipes and strip anchors were essentially similar. The peak uplift resistance of a strip anchor tended to be greater than that of a pipe at shallow depths, but the difference reduced as the sand-pipe interface frictional strength and the embedment ratio increased. Image analysis shows that the peak resistance of a shallow strip anchor/pipe was mobilised through the formation of an inverted trapezoidal block, bounded between a pair of inclined shear zones. The inclinations of the shear zones were dependent on sand dilatancy, and its average angle to the vertical for a strip anchor is slightly larger than that for a pipe. The shear zones initiate from the edges of an anchor invariably, whereas the initiation points may lie above the pipe waist, varying with sand-pipe interface conditions. These observations were used to modify a limit equilibrium method and a cavity expansion approach for predicting the peak uplift resistance of shallow pipes in sand. The modified methods were validated using a database of 125 shallow pipe uplift tests assembled from the literature. After the modifications, a good agreement with the overall database was shown, with average errors of less than 6%.

The stability of pile-supported structures under earthquake loads involves complex dynamic soil–structure interaction (SSI). A series of large-scale shaking table experiments was performed to investigate the seismic performance and SSI of pile-supported structures considering different ground conditions. Lateral soil resistance and dynamic displacements of superstructures located in nonliquefiable and liquefiable sites as well as a rigid foundation were measured during shaking tests. The measured responses were analyzed to investigate the P-$\mathrm{\Delta }$ effect on structural stability. It was observed that the soil lateral resistance to the pile cap at the nonliquefiable site was large and represented the main component of the lateral bearing capacity resisting structure overturning. On the other hand, the lateral resistance of liquefied soil on piles was insignificant and the lateral bearing capacity was derived primarily from soil resistance to pile cap. The analysis of the measured dynamic displacements demonstrated that the seismic instability of the structure was mainly due to the P-$\mathrm{\Delta }$ effect caused by the rotation of the foundation, especially in liquefied sites. In addition, comparison with the results of base shears and bending moments with the rigid base assumption allows for an in-depth discussion of the effect of SSI on structural seismic design.

Existing nondestructive pile integrity test (PIT) methods have certain limitations in the interpretation of test results for extended pile shafts supporting an existing structure. A novel multipoint traveling wave decomposition (MPTWD) method was developed in this study to address some of these limitations and predict the unknown length of an extended pile shaft with superstructure. The MPTWD method incorporates a test scheme that comprises multiple equally spaced sensors to separate the downward and upward waves and a corresponding data processing method. A pseudofrequency response (PFR) function was defined by dividing the measured upward wave by the downward wave in the frequency domain. Based on the PFR function, MPTWD results are obtained for a certain fictitious excitation. The unknown pile length can then be predicted by fitting the MPTWD results and the analytical solution to that of a laterally vibrating free-top pile. Because of their similar experimental layout, the MPTWD results are close to traditional PIT results and have fundamental advantages and disadvantages. The effects of technical test parameters on MPTWD results were investigated through a comprehensive parametric study. Then, the MPTWD method was applied in a field test, and the predicted pile length was found to be consistent with its actual precast length, verifying the feasibility and reliability of this novel method.

Piping has been a documented cause of collapse of multiple tailings dams, hydraulic structures and natural slopes. Important limitation of the existing piping criteria for a sloped ground is that they are treating soils as hydraulically isotropic, which is rarely the case in real life problems. Another obstacle for wider application of these criteria in engineering practice is that they have not been translated into an adequate definition of the safety factor against piping. This paper provides rigorous yet simple piping criteria and safety factors for slopes built of hydraulically stable anisotropic materials, as well as the safety factor against instability of an infinite anisotropic slope with a slope-parallel flow. It has been demonstrated why it is important to account for anisotropy, and how the proposed analytical expressions can be applied to practical problems with calculated flow nets and piezometric field measurements.

Upheaval buckling (UHB) is a common design issue for buried pipelines when the out-of-straightness of the pipeline combined with the high axial compressive forces induced by the extreme operating conditions causes the pipeline to buckle upwards. It is common to mitigate UHB for onshore pipelines by having deeper burial depths. However, a more practical and cost-effective solution would be to use compacted backfill, which would provide higher uplift resistance and smaller mobilization for buried onshore pipelines. Knowledge of uplift resistance in compacted soil is limited in the literature. This paper presents results from full-scale experiments in which uplift resistance of compacted and uncompacted soil was measured for cover depths ranging from 1.2 to 2.4 m. The effect of the degree of compaction, cover height, and backfill unit weights on uplift resistance and mobilization is presented. A new analytical relationship between the uplift resistance and displacement is proposed for pipelines buried in sand backfills in compacted and uncompacted states.

Using a database of approximately 900 data pairs from 230 sites of co-located cone penetration test (CPT) soundings and boreholes with standard penetration tests (SPT) in the South Island of New Zealand, this paper assesses the applicability of a range of existing SPT–CPT correlations. Simple linear SPT–CPT correlations for different soil types as well as correlations based on the soil behavior type index ($I_c$) from CPT data were assessed. The measured SPT $N_{60}$ data were poorly fit by all the correlations, with under- and over-predictions greater than 50% for between 40% and 55% of the database. The 95% confidence interval of the bias between predicted and measured SPT $N_{60}$ values was large across all variables. The bias varied significantly as a function of CPT tip resistance and sleeve friction, with underestimates at low values dominated by fine-grained soils ($I_c>2.05$), and overestimates at high values dominated by silty sand to dense sand ($I_c\le 2.05$). There was no clear effect of the different drilling methods on the bias observed across all parameters. These results highlight the significant uncertainty involved in the application of these correlations in geotechnical design and assessments.

This study presents an analytical framework to estimate the change in ultimate bearing capacity of energy piles in unsaturated fine-grained soils under drained mechanical loading conditions after drained heating. The framework was developed by extending conventional methods for the ultimate bearing capacity of piles in unsaturated soils to temperature-dependent conditions, where thermally induced changes in the characteristics of the unsaturated soil and soil–pile interface are considered. Specifically, the thermally induced variations in matric suction and effective saturation profiles with depth were incorporated into calculations of the shaft capacity and the end bearing capacity of piles in unsaturated soils. The proposed ultimate bearing capacity model is validated against experimental data for an energy pile loaded to failure in unsaturated Bonny silt, and a good match between measured and predicted values was obtained. A parametric study was carried out to evaluate the effects of infiltration rate and pile aspect ratio (i.e., pile embedment length/pile diameter) on the ultimate bearing capacity of energy piles in unsaturated clay and silt layers subjected to temperatures ranging from 5°C to 45°C. For both soils, the shaft, end bearing, and ultimate bearing capacities vary with an increase in temperature. At the reference temperature, the shaft, end, and ultimate bearing capacities vary monotonically with pile embedment length, while at elevated temperatures they vary nonmonotonically with pile embedment depth. At a given temperature, the parametric study shows that the bearing capacity of energy piles in clay decreases with increasing downward infiltration of water into the soil profile surrounding the energy pile, while in silt it may decrease or increase depending on pile embedment length. The ultimate bearing capacity increases with a decrease in pile aspect ratio at all temperatures. Estimates of the ultimate bearing capacity of energy piles in unsaturated fine-grained soils from the framework are a critical part of thermomechanical soil–structure interaction analyses needed to design energy piles, so this study contributes toward the widespread application of this emerging technology in practice.

A granular filter is required to satisfy two requirements of retention and hydraulic conductivity. The current design approaches are based on the representative grain sizes for retention and hydraulic conductivity requirements. The importance of consideration of the grain-size distribution (GSD) in satisfying the filter requirements is highlighted in this paper. An assessment criterion is presented for retention and hydraulic conductivity requirements based on GSD. A probabilistic assessment criterion is developed for retention requirements considering the grain size and constriction size as random variables. For hydraulic conductivity requirements, a probabilistic assessment criterion is defined by considering hydraulic conductivity’s variability and a semianalytical model for saturated hydraulic conductivity. The limit states for developed criteria are established based on published experimental data. The proposed approach is demonstrated with examples, and it is illustrated that the filter bandwidth is governed by the convexity of the soil GSD.

Two-dimensional nonlinear dynamic analyses (NDAs) are performed for a series of hypothetical embankment dams on a spatially variable liquefiable foundation layer to evaluate the utility of representing the foundation layer with random fields conditioned on different levels of site characterization information. A set of two-dimensional parent models (PMs), each representing a true foundation condition, were generated using unconditional random fields of equivalent clean sand, corrected standard penetration test $({\mathrm{N}}_1{)}_{60\mathrm{cs}}$ values. Different levels of site characterization were then represented by combining different numbers of local borings (i.e., columns of data from the PM) with the optional inclusion of constraints on the geostatistical properties that might come from sitewide explorations. NDAs were performed using the same input motions for the PM (which represents perfect knowledge of soil conditions), a set of realizations conditioned on the local borings alone, and a set of realizations conditioned on the local borings with sitewide statistics. Embankment deformations obtained for the conditional realizations are compared to those for the PM to evaluate the potential benefits of increasing levels of site characterization in terms of deformation prediction accuracy. Parametric analyses include varying the embankment size, scales of fluctuation in the foundation stratum, number of conditioning borings, and ground motions. The results of these comparisons illustrate that the beneficial effects of using conditional random fields were generally limited to cases with the horizontal scale of fluctuation approaching the scale of the embankment base width and to cases with a large number of borings (more than three borings per horizontal scale of fluctuation), which may not be practical in many situations. Additional potential benefits and limitations of using conditional random fields for representing spatial variable liquefiable foundation layers in embankment dam NDAs are discussed.

When penetrometers or probes are pushed into sand, complex displacement fields, strain fields, and shear band patterns develop. Deep and shallow penetration processes in sands generate substantially different patterns. This paper reports the results of penetration experiments performed in dense air-pluviated sand samples prepared in a half-cylindrical calibration chamber equipped with observation windows that allow the collection of images of the sand during penetration. Both a cone penetrometer (diameter $d=38\mathrm{mm}$) and a model footing (width $B=90\mathrm{mm}$) are used in the penetration experiments. Incremental displacement and strain fields in the soil domain are obtained by analysis of the collected images using digital image correlation (DIC) and continuum mechanics. The zero-extension line concept is used to study shear strain localization, and a method is proposed to automatically obtain the orientation of shear band patterns from the incremental strain fields. For the model footing, the strain fields are found to localize not only near the footing but also away from it, depending on the level of penetration. The shear bands develop in a traditional wedge shape below the model footing and in a fan shape on either side of it. In contrast, for the cone penetrometer, the strain fields localize more intensely near the penetrometer tip. The shear bands develop along the inclined face and near the shoulder of the penetrometer.

Deflection walls were considered for mitigating lateral spreading-induced bending moments on large-dimension foundations. The efficacy of the walls was tested using dynamic centrifuge testing of a large-dimension rectangular foundation (caisson) with and without an upslope ground deflection wall. The ground deflection walls were modeled as buttressed sheet pile walls and were intended to deflect the laterally spreading ground around the caisson and reduce the pressure transmitted to the caisson. Three wall shapes (chevron, arch, and truncated chevron) were tested in all-sand profiles and profiles with a clay cap underlain by sand. In contrast to the unprotected caisson tests, the deflection walls successfully redirected the laterally spreading sand-only profiles around the caisson and minimized passive wedge development upslope of the caisson. Maximum lateral pressures measured on the upslope face of protected caissons ranged from at-rest pressures to the total vertical stress and were about 30%–50% lower than those measured against unprotected caissons. Based on these results, the proposed buttressed sheet pile walls may be suitable to mitigate lateral spreading forces on existing foundations. These results also suggest that newly constructed large foundations or pile groups may be arranged in a diamond or circular pattern to better mitigate potential lateral spreading earth pressures.

This study clarifies the failure mechanisms of the 2014 catastrophic large deep-seated landslide and simulates the dam formation process at Jure Village, Nepal, through site investigations, ring shear tests, and LS-RAPID computer simulation model. The detailed analyses suggest that the Jure landslide triggered by a high cumulative rainfall slid along bedding-plane faults of weathered phyllite and schist on the slope of an ancient landslide terrain. The landslide comprised two separate subblocks; the upper and lower slopes, whose sliding mechanisms differed from each other. The test results indicate that the upper subblock of the landslide was triggered by rainfall with a critical pore pressure ratio of $0.22–0.26$. The lower slope failure resulted from a dynamic loading process initiated by the downward movement of the upper slope. In the LS-RAPID model, the evolution process of landslide damming the river was reproduced and verified based on the observed geomorphic evidence and recorded data. The study shows landslide mobility acted as the critical factor leading to the landslide dam formation, in addition to the geomorphic indexes.

The Regional Connector Transit Corridor (RCTC) project consists of an 89-m long, 17.7-m wide, and 11-m high span crossover cavern constructed beneath critical infrastructure using the sequential excavation method (SEM) at relatively shallow depth (15 m below ground surface) in downtown Los Angeles. The cavern construction involved a complex three-drift, two-sidewall configuration and was excavated in the Fernando formation, a weak clayey siltstone. This paper presents a comprehensive case study of the cavern excavation and initial support construction. The performance of the urban SEM was assessed and complex ground behavior was examined once per excavation step during the construction process. The overall average surface settlement was 20 mm and the largest single-stage incremental movements occurred in the center bench and invert excavation, accounting for 30%–40% of the total deformation. The subsurface experienced less differential settlement during the side drift excavations due to the ovate excavation profile and the restriction from surrounding infrastructure. The measured center crown vertical displacement varied between 5 and 10 mm and the center invert initial support was recorded to heave 8–12 mm. A systematic procedure was developed to apply a deliberate observational method. The lessons learned support that appropriate real-time analysis improves the quality of regular data review, continuously updating the knowledge of risk and enabling prompt adaptions and optimizations of the design and construction along the SEM tunneling process.

Jacking force is one of the most important parameters in pipe jacking engineering, and also the key in pipe jacking design. A lot of research has been done on the prediction of jacking force of a single pipe. However, the research on jacking force of a row of steel pipes is relatively rare. A case of pipe jacking project is studied in this paper. In construction the test pipes were successfully jacked into the designed position, but the subsequent pipes were stuck because the jacking machine could not provide enough jacking force. Based on this phenomenon, the influence on the jacking force from the pipe spacing and the number of pipes have been jacked around the pipe being jacked is studied by field measurement and numerical simulation. The mechanism of the steel pipes stuck after the test pipes is analysed in detail. The results show that the jacking force decreases nonlinearly with the increase of the pipe spacing, and the influence range of pipe jacking is three times the pipe diameter; the jacking force increases with the increment of the number of pipes that have been jacked, but the increasing trend gradually slows down. Based on the above results, the pipe group effect of jacking force is proposed which is verified by the measured data. The results indicate that the amplification and superposition effect of the jacking force should be considered in the design stage to avoid pipes stuck in the jacking process.

Xanthan gum (XG) biopolymer-based soil treatment is an effective soil improvement method. In this study, we explored the effect of XG on the undrained shear strength of clays (kaolinite and montmorillonite) in chemically distinct pore fluids. Among the pore fluids tested, the undrained shear strength of kaolinite was the highest in kerosene, followed by deionized (DI) water and brine. This study hypothesized that the interparticle forces and interactions dominated the undrained shear strength of the kaolinite clay. In contrast, montmorillonite showed the highest undrained shear strength with DI water, followed by brine and kerosene, likely due to the increase in thickness of the viscous double layer that reduced the undrained strength of the montmorillonite clay. XG also affected the undrained shear strength of the clays, possibly due to the increase in viscosity of the pore fluids and modification of the clay interparticle fabrics. In DI water, XG increased the undrained shear strength of kaolinite (maximum shear strength was observed in the sample with an XG-to-soil mass ratio of 0.5%) via water absorption. Simultaneously, XG decreased the undrained shear strength of montmorillonite, likely due to XG-induced particle aggregation resulting from the changes in the montmorillonite particle surface charges. In 2-M-NaCl brine, the undrained shear strength increased with the increase in XG content, regardless of the mineral types, owing to the salt-induced double-layer compression and increase in concurrent XG-induced pore–fluid viscosity. However, the unaffected and constant undrained shear strength of both clays in nonpolar kerosene suggests that hydrating XG is a prerequisite for its application in soil treatment.