Journal of Geotechnical and Geoenvironmental Engineering

During embankment construction, the deformation behavior of soil will vary with increasing fill height because the principal stresses applied on soil elements in $K_0$-consolidated subsoil will rotate. In this study, a series of tests is conducted on natural $K_0$-consolidated Wenzhou soft clay in a hollow cylinder apparatus (HCA) to clarify the response of soils during principal stress rotation. Specimens are sheared with different angles of inclination ($\beta$) with respect to the vertical direction in undrained conditions. The stress-strain relationship, pore-water pressure evolution, shear strength, and noncoaxiality are discussed. The test results show that the development of strain components (vertical, radial, circumferential, and shear strains) is clearly distinct during orientational shearing. The coupling action of the axial and shear stresses results in different evolution processes of the excess pore-water pressure in tests with different $\beta$ values. Under a critical state, the elliptical and asymmetric effective stress strength envelope conclusively shows a strong undrained strength anisotropy. In addition, the different noncoaxial angles between the major principal strain increment direction and corresponding major principal stress direction at failure is revealed, and the noncoaxial behavior is dependent on the $\beta$ value.

The use of jute and coir fibers as natural fiber drains to facilitate drainage and soft soil stabilization has been proposed for decades. However, their uncertain hydraulic behavior has often hampered their wider application in major infrastructure projects. Because these drains have a complex porous structure that can trap soil particles and reduce their discharge capacity, a comprehensive laboratory investigation in which soft soil was used to interact with different fiber drains under varying confining pressure was conducted via a discharge capacity test scheme. Nondestructive micro–computed tomography (CT) scanning followed by a series of image processing techniques was applied to the drains to capture their three-dimensional porous characteristics, which were then used to clarify their hydraulic behavior. The study revealed that there are two major types of components—intra- and interbundle voids—making porosity in a fiber drain, and they can be used to evaluate the drain discharge capacity. The larger the interbundle porosity, the higher the drain discharge capacity. Jute filters not only enlarge the interbundle porosity but also—if they are thick enough—help drains resist undue lateral pressure and clogging. Fiber drains are more sensitive to confinement than polymeric drains, because their discharge capacity decreases considerably at higher confining pressures. This study enables the hydraulic properties of natural fiber drains subjected to soil clogging to be properly understood so that drain designs can be optimized to make them more competitive with conventional polymeric drains.

Experiments were conducted to evaluate the hydraulic conductivity of geosynthetic clay liners (GCLs) containing bentonite–polymer composites (BPCs) permeated with coal combustion product (CCP) leachates. Eight synthetic CCP leachates were used: the five characteristic CCP leachates from a leachate database and three based on actual leachate chemistries. Hydraulic conductivity tests were conducted on non-prehydrated and prehydrated BPC GCL specimens at an effective stress of 20 kPa. Prehydration was achieved by contact with a subgrade for 60 days or by permeation with deionized (DI) water. Comparisons are made to the hydraulic conductivity and swell index of conventional sodium bentonite (NaB) GCLs permeated with the same leachates. The hydraulic conductivity of BPC GCLs with low polymer loading ($<1.9\%$) to the CCP leachates is similar to that of NaB GCLs, with hydraulic conductivity related inversely to swell index and directly to ionic strength. For higher polymer loading ($\ge 1.9\%$), the hydraulic conductivity of BPC GCLs appears to be controlled by the polymer hydrogel and is not related directly to the swell index of the BPC or ionic strength of the leachate. Higher hydraulic conductivity of BPC GCLs is associated with greater polymer elution and nonuniformity of the polymer within the GCL. Subgrade hydration had a modest beneficial effect on the hydraulic conductivity of a BPC GCL with low polymer loading ($<1.9\%$). Prehydration by permeation with DI water resulted in low hydraulic conductivity ($4.3\times {10}^{-11}\mathrm{m}/\mathrm{s}$) for this same GCL with one of the strongest leachates.

Embedded plates provide an attractive anchorage alternative for mooring floating structures owing to their light weight and high efficiency. They can be installed through a variety of means, including suction, driving, or dynamic installation. A primary measure of anchor performance is monotonic drained capacity, which increases with increasing embedment depth owing to increased soil strength and the diminishing effect of the free surface. While the performance of plate anchors in clay has received thorough coverage in the research literature, attention to plate anchors in sand has been relatively limited, particularly for deeply embedded plates. This paper presents a numerical study of the monotonic capacity of circular, horizontally oriented anchors in sand, subjected to centric loading. The finite-element study investigates a range of anchor embedment depths from 1 to more than 20 plate diameters. This depth range is sufficient to characterize the transition of the anchor behavior from a shallow to a deep failure mechanism, for which the latter has an associated depth-independent dimensionless breakout factor. The study employs a large-displacement finite-element analysis employing a Mohr-Coulomb soil model with a nonassociated flow rule. Key soil properties considered in the analysis include the friction angle, dilation angle, and rigidity index of the soil. At shallow anchor embedment depths, the rigidity index has a negligible influence on anchor capacity. However, the performance of deeply embedded anchors is strongly influenced by all three parameters considered in the study. Finite-element solutions proved to be in good agreement with previously published lower-bound plastic limit analyses. Comparisons to experimental data showed good agreement in terms of overall trends of anchor capacity versus depth. For design purposes, this research developed an empirical model for predicting anchor monotonic drained capacity as a function of relative density and anchor embedment depth.

This study proposes a limit equilibrium approach to estimating the bearing capacity of strip footings placed on geosynthetic-reinforced soil structures (GRSSs). To assess the multiple mechanisms that may govern the ultimate resistance sustained by GRSSs, logarithmic-spiral, two-part wedge, two-sided general shear, one-sided general shear, and failure above the uppermost geosynthetic layer are proposed. Each of these mechanisms is assessed considering geometry, geotechnical properties, and geosynthetic rupture, whereupon an algorithm selects the minimum, critical bearing capacity and associated failure mechanism for design. Additionally, the effects of foundations placed near the transition between reinforced and unreinforced soil are evaluated. Considering these factors, both the failure mechanism and bearing capacity attained from this analysis are compared with rigorous numerical models, demonstrating agreement. The multimechanism approach is then extended to assess bearing capacity considering various geometric configurations and material properties. Finally, a set of dimensionless charts are presented for convenient assessment of the ultimate bearing capacity of strip footings placed on GRSSs.

This paper presents the results of a series of tensile-compressive (TC) and compressive-tensile (CT) static load tests performed on instrumented model piles preinstalled in silica sand samples prepared in a half-cylindrical calibration chamber with viewing windows along its symmetry plane. Images of the model pile and the surrounding soil were captured during axial loading through the observation windows using digital cameras and were subsequently analyzed using the digital image correlation (DIC) technique to generate the displacement and strain fields in the sand domain. The shaft resistances mobilized during the experiments were obtained using load cells placed at the head and the base of the model piles. The results obtained from the load tests revealed that reversal of loading direction substantially reduces the unit shaft resistance. This response was attributed to a drop in the radial strain exhibited by the soil elements surrounding the model pile shaft, which could be explained by a misalignment of the principal axes of the stress and fabric tensors resulting from load reversal. The results also indicated that the tensile-to-compressive shaft resistance ratio of fresh preinstalled piles is always nearly one.

This study compiles 320 static-load tests to quantify the model factors in reliability-based limit-state design of drilled shafts under axial loading. At ultimate limit-state, the model factor is defined as the ratio of the measured capacity to the calculated capacity. It characterizes the bias in capacity calculation. The measured capacity is interpreted from load test data by the modified Davisson offset limit, and current design methods are utilized to compute the ultimate axial capacity. The load-displacement data are simulated by two-parameter hyperbolic curves. Based on the database, the statistics and probability distributions of the capacity and load-displacement model factors are established. Several copulas are selected for goodness-of-fit tests on the observed correlation of the hyperbolic model factors. The model factor at serviceability the limit-state is then described by two correlated hyperbolic parameters. Finally, the model statistics are applied to implement the LRFD of drilled shafts under axial loading by Monte Carlo simulations.

Cyclic temperature changes in an energy pile generate cyclic thermal expansive and contractive strains along the interface, which may impact both the serviceability and the ultimate pile resistance. This paper aims to assess induced changes in the shaft resistance of an energy pile after being subjected to different temperature variation, between 24°C and 34°C. This was done by measuring the load-settlement curve of a laboratory-scale floating energy pile installed in fully saturated normally-consolidated (NC) kaolin. A 10% relative settlement criterion was adopted to define the shaft resistance. Changes in temperature and pore pressure were also monitored in the surrounding clay using embedded thermocouples and a pore pressure transducer. Measurements during thermal loading showed that a positive excess pore water pressure was generated during the first thermal cycle followed by a negative pore pressure (suction) during the same cycle, while subsequent thermal cycles generated a cyclic pore pressure that remained negative regardless of the number of thermal loading cycles. It was also observed that piles subjected to heating exhibited greater shaft resistance than the reference pile tested at room temperature. Although the shaft resistance was considerably influenced by cyclic thermal loading, increasing the number of thermal cycles did not make appreciable differences in shaft resistance.

Soils deform as a function of time because of the consolidation and the creep processes. Under undrained conditions, the consolidation process is prevented and the creep deformations are isolated. A series of unconsolidated undrained (UU) triaxial tests were conducted to investigate a creep deformation model and a creep failure model. The creep deformation model estimates the deformation as a function of time for a sustained stress level. It is a simple power law able to describe the creep measurements observed in the experiments. The creep failure model predicts the approximate time for the creep failure to occur under a sustained stress level. It is based on a strain-failure concept in which the failure time is defined as the time necessary to reach the failure strain. The main model parameters are the creep exponent and the strain to failure, which can be obtained from creep triaxial tests and from standard triaxial experiments, respectively.

Microbial-induced calcium carbonate (${\mathrm{CaCO}}_3$) precipitation (MICP) has been explored for its potential engineering applications such as soil stabilization, but current understanding of the fundamental MICP processes at the microscale is limited. In this study, real-time in situ microscale experiments were conducted using glass slides and microfluidic chips (synthetic porous media that simulate soil matrices to model the conditions similar to actual MICP treatments) to visualize the ${\mathrm{CaCO}}_3$ precipitation process. The results of this study show that irregularly shaped ${\mathrm{CaCO}}_3$ precipitates initially emerged on bacterial aggregates and subsequently dissolved with time as regularly shaped ${\mathrm{CaCO}}_3$ crystals started growing; less stable and smaller ${\mathrm{CaCO}}_3$ crystals may dissolve at the expense of growth of more stable and larger ${\mathrm{CaCO}}_3$ crystals. The time-dependent phase transformation of ${\mathrm{CaCO}}_3$ precipitates makes the size of the crystals formed during MICP highly dependent on the time interval between cementation solution injections during a staged-injection procedure. When the injection interval was 3–5 h, a larger number of crystals (200–1,000 per ${10}^6{\mathrm{\mu m}}^3$) with smaller sizes (5–10 μm) was produced. When the injection interval was longer (23–25 h), the crystals were larger (10–80 μm) and fewer in number (5–20 per ${10}^6{\mathrm{\mu m}}^3$). The direct observation of MICP processes in this study improves the understanding of MICP fundamentals and the effect of MICP processes on the properties of ${\mathrm{CaCO}}_3$ crystals formed after MICP treatment. These observations will therefore be useful for designing future MICP treatment protocols that improve the properties and sustainability of MICP-treated samples.

Earthquake fault rupture-soil-foundation interaction (FR-SFI) was simulated using the discrete element method (DEM) with irregularly shaped sphere-clusters to capture the three-dimensional nature of sand grains. High-performance computing simulations of free-field fault rupture and FR-SFI compared well with geotechnical centrifuge experiments in terms of shear rupture development, surface deformation, and foundation response. Micromechanical analyses of particle rotations, interparticle contacts, and void ratio distributions provided key insight into the mechanisms of FR-SFI. Particle rotations showed clearly where rupture surfaces developed, and the distributions of void ratios showed which rupture surfaces softened fully. The rupture surfaces for reverse fault displacement deflect systematically toward the hanging wall side of the foundation as its contact pressure increases. The shear rupture produced by normal faulting migrates from one path propagating toward the hanging wall side of the foundation to a second path propagating toward the footwall side of the foundation due to the presence of the foundation. DEM shows promise for evaluating earthquake FR-SFI.

The present study investigates the rainfall-induced long-runout landslide that occurred in the Achanakkal area of the Nilgiris district in the Tamil Nadu state of India on November 11, 2009. The landslide damaged a house located on the runout path and killed its eight residents. The slide also damaged a road network, affecting traffic for several weeks. The main objective of the study is to understand the failure mechanism associated with Achanakkal 2009 landslide. This study is composed of a field investigation, laboratory experiments, and a numerical simulation of the landslide. Based on the field investigation including a topographical survey, a borehole investigation, a geophysical test, and laboratory classification tests, the slope geometry was identified and the subsoil was characterized. Ring shear tests were performed to estimate the shear strength parameters such as peak and residual friction angle (${\phi }_p$ and ${\phi }_m$) and steady-state shear resistance (${\tau }_{ss}$). Numerical simulation of the landslide was carried out using the LS-RAPID landslide simulation model by incorporating the shear strength parameters obtained from the ring shear tests. The simulation results reproduced the failure mechanism of the Achanakkal landslide and matched the runout distance, landslide boundary, and distribution of debris mass that were observed from the topographical survey well. The analysis results revealed that the rainfall infiltration due to 5 days’ antecedent rainfall of 594 mm; a very large amount of daily rainfall, 820 mm, on the event day; and accumulation of rainwater on the source area charging from the above plateau due to blocking of drainage culverts increased the soil saturation. An increase in saturation level of the soil developed the pore water pressure in the source area. The development of pore pressure to $r_u=0.5$ significantly reduced the shear resistance of the soil at the slip surface from the peak value to the residual value along with shear displacement was the possible cause for triggering of Achanakkal landslide. The analysis also revealed that the simulation model initiates the landslide at a smaller pore water pressure ratio than the limit equilibrium method of stability analysis due to progressive failure.

The strength properties of basalt fiber–reinforced biocemented (BFRB) sand specimens with various calcite contents and fiber contents are investigated through a series of unconfined compressive and splitting tensile tests. Reverse injection is introduced to improve the uniformity of the calcium carbonate precipitation. The test results show that both the unconfined compressive strength (UCS) and splitting tensile strength (STS) at a given basalt fiber content increase significantly with increasing calcite content, whereas the axial strain of the peak failure state decreases with increasing calcite content. The improved ductility has implications for loading conditions where large deformations may be anticipated. The UCS, STS, and peak failure state strain increase with increasing fiber content at a given calcite content, which is interpreted to be due to the interlocking, reinforcing, and bonding effects observed in scanning electron microscopy (SEM) images. A phase-volume framework for determining the porosity of BFRB sand is developed and used within an existing empirical formulation developed for other types of fiber-reinforced, cemented geomaterials. Moreover, the UCS and STS of the BFRB sand can be described by the existing empirical formulations incorporating the cementing factor index expressed in terms of the porosity and calcite volumetric content. Predictions based on the empirical formulations are in good agreement with the test results for the UCS and STS of the BFRB sand specimens.

This paper examines and reports on two new methods, i.e., the Stockwell transform based (ST) method and self-healing cross-correlation (SC) method, in determining the S-wave arrival time for bender element tests, especially for $V_s$ tomographic imaging. In the ST method, the Stockwell transform is first carried out to obtain a high-resolution time-frequency representation of the receiving signal; then, the energy in the frequencies around the resonant frequency is summed, followed calculation of the associated energy gradient. The maximum energy gradient is selected as the objective criterion to determine the arrival of the S-wave, since its arrival leads to a distinct amplitude increase and a notable change in the associated energy. The accuracy of this ST method is validated using both numerical and physical experiments. The ST method requires high computing power for signal processing; hence, the SC method is proposed to tackle this practical problem. Considering two consecutive measurements made by the same pair of bender elements in a time interval, subjected to only small changes in the stress states, both measurements should exhibit a similar waveform but with a minute time-shift. Therefore, the cross-correlation peak of the two consecutive measurements gives the travel time difference between them. The validity of the SC method is verified by a laboratory pile installation test equipped with a bender element sensing layer; and good agreement is found between the results obtained from the ST and SC methods. The strengths of these two methods enable us to objectively and automatically process the tremendous amount of bender element signals produced by the high-resolution time-lapsed $V_s$ tomographic images, as demonstrated by process monitoring of the pile installation.

Adaptive management is a design approach which allows one to change support and/or construction procedures during excavation based on observed responses to meet specific design objectives. To obtain the most benefit from an adaptive management approach, inverse analysis procedures are used to make parameter updates based on observations collected during the early stages of a project and applied to later stages to predict future performance. This paper describes the inverse analysis of lateral wall deformation data collected from a supported excavation in Chicago. The Hardening Soil (HS) model and the HS model with small-strain stiffness are used to represent stress-strain behavior of medium clay and stiff clay layers of an excavation in Chicago. Initial parameters for the soil models are based on previous inverse analysis studies conducted for excavations in Chicago soils. Deformations computed using the initial parameters are compared with the field measurements to evaluate the capabilities and limitations of each model. Optimization during inverse analysis is based on a gradient method using measured lateral wall deformations. Changes in the optimized parameters during various levels of excavation are assessed. Computations made with the optimized soil parameters are compared and their efficacies for prediction purposes are evaluated.

Flexible barriers trap large particles and boulders in debris flow but allow slurry and small particles to pass through. Field tests and real cases indicate that a certain amount of slurry and small particles in debris flow passes through a flexible barrier with residual velocities. In the design of flexible barriers for debris flow mitigation, accurate determination of the impact force is the key issue. Nevertheless, a few of the current simple methods have quantified the effect of passing through on the impact force reduction. Without considering the passing through of slurry, impact loading can be tremendously overestimated. In this study, a new simple method considering the passing through of slurry is proposed based on a two-phase flow model. This method is verified by the measured impact forces of two large-scale physical modeling tests. In the tests, debris flows with different water contents in mass (89.4% and 61.1%) were initiated to affect a flexible barrier. The volume of the retained debris and the velocity loss of the passing slurry in the two tests were measured. Furthermore, this proposed simple method is validated by the data from well-documented laboratory tests in the literature. Comparisons and validations lead to the conclusion that the proposed simple method provides an accurate and creative way to predict the dynamic impact force of muddy debris flow on a flexible barrier.

Internal erosion is the cause of significant damage in dams and river embankments in many countries. In the last 20 years, the use of fiber-optic distributed temperature sensing (DTS) has proved to be an effective tool for the detection and quantification of leakages and internal erosion in dams. This work investigates the effectiveness of DTS for levee monitoring and focuses on the early detection of backward erosion piping. The latter is a failure mechanism that affects the foundation layer of structures resting on sandy soils. The paper presents data from a piping test performed on a large-scale experimental levee equipped with a DTS system together with a large number of accompanying sensors. With the help of numerical modeling, the effect of seepage and backward erosion piping on the pore pressure and temperature field is analyzed, eventually bringing the identification of the processes that promote the onset of thermal anomalies.

Effective stress is a critical factor controlling the mechanical behavior of unsaturated soils. There has been an increasing interest toward fundamental and applied research on emerging applications that involve unsaturated soils subjected to elevated temperatures. However, major gaps remain in the development of a unified model that can properly represent temperature dependency of effective stress in unsaturated soils. The main objective of this study is to develop closed-form equations to describe the effective stress of unsaturated soils under nonisothermal conditions. For this purpose, suction stress-based formulations are developed for representing temperature-dependent suction stress and effective stress of unsaturated soils. The formulations incorporate temperature-dependent moist air pressure and matric suction into a skeleton stress equation originally developed using volume averaging. A nonisothermal soil water retention curve (SWRC) is used to account for thermal effects on the adsorbed water, surface tension, contact angle, and enthalpy of immersion per unit area. The validity of the model is examined by comparing predicted suction stress values against experimental data reported in the literature for various soils ranging from clay to sand. The effective stress equations developed in this study can provide further insight into the behavior of unsaturated soils under nonisothermal conditions. The models can be readily incorporated in numerical and analytical methods, leading to more accurate modeling of unsaturated soils subjected to nonisothermal loading conditions.

This paper reports the performance of a novel dynamically installed fish anchor under cyclic operational loading in calcareous silt. The investigation was carried out through a series of centrifuge model tests. The results demonstrate that the pullout capacity of the fish dynamically installed anchor (DIA) subjected to cyclic loading is dependent on the combination of cyclic mean load, cyclic load amplitude, and number of cycles. A design contour is proposed for estimating the anchor capacity under various magnitudes of cyclic load. The evolution of anchor displacement, inclination, and excess pore pressure are quantified and their influences on the fish DIA capacity are highlighted. With a tip embedment depth of 1.02–1.43 times the anchor length during dynamic installation, the fish DIA was found to dive in calcareous silt for mooring mudline inclinations $\le 45°$ under both monotonic and cyclic operational loadings, whereas by contrast, the OMNI-Max anchor with tip embedment of 1.4–2 times the anchor length did not dive for inclinations as low as 1°–10°. As such, the fish DIA has the potential for efficient anchoring to allow economic development of oil and gas reserves in deep water with calcareous seabed sediments.

This study was carried out to evaluate a technique to improve lateritic soil layers that are susceptible to collapse upon wetting so that they can be used to support shallow foundations. Specifically, this study focused on the impact of placing groups of compacted lateritic soil columns within a collapsible soil layer, because this may be a more cost-effective alternative than excavating the entire collapsible soil layer and replacing it with a monolithic compacted fill. For this research, oedometer and centrifuge model tests were performed on a lateritic soil collected in the southeastern part of Brazil. The results of the centrifuge tests were used in a numerical analysis to examine the performance of shallow foundations on collapsible soils reinforced with compacted columns under inundated conditions. The experimental and numerical results indicate that such a technique can improve the load-displacement response of shallow foundations constructed on the soil tested and reduce wetting-induced collapse settlements.

Increased seismic flexural demands on drilled shaft foundations have led to significant increases in the amount of steel reinforcement, leading to a greater number and/or larger sized steel bars and increased possibility of anomalies within drilled shafts due to reduced apertures between the reinforcement for concrete passage. High-strength steel reinforcement and/or permanent steel casing may be used to provide increased structural resistance in addition to mitigating the concern for voids or other potential anomalies. However, the comparison of lateral load transfer characteristics of drilled shafts with and without permanent steel casing and/or high-strength reinforcement bars has not been previously investigated, which raises questions regarding the suitability of existing analytical approaches for application in these circumstances. This paper presents the full-scale lateral response of drilled shaft foundations constructed with and without steel casing and with high- or mild-strength reinforcement. The lateral loading performance of a cased shaft without internal reinforcement exhibited similar characteristics to a cased shaft with internal reinforcement. Similar lateral loading performance between uncased shafts with mild- and high-strength reinforcement was also observed. The observations and test results indicate that high-strength reinforcement can be used without detriment to the lateral performance of drilled shafts, despite reduced physical confinement provided by transverse reinforcement. Back-calculated soil reaction-displacement ($p\text{-}y$) curves indicated significant differences between shafts of similar nominal diameter, indicating nonnegligible effects of soil–foundation interface and diameter.

The crushing behavior of carbonate sand, due to its porous and fragile structure, exerts a significant influence on the construction of coastal engineering. The collapse of porous material usually produces elastic wave dissipation and force drop in stress-strain curves. To study the acoustic and mechanical characteristics of carbonate sand crushing, both force and acoustic emission (AE) signals were measured as a function of run time in single-particle uniaxial compression tests. Rapid large force drops corresponding to avalanches led to obvious AE signals. The AE signal analysis of carbonate sand was consistent with avalanche statistic laws, e.g., the Gutenberg–Richter law of energies, the double power law distributions of waiting time, the statistics of aftershocks, and Båth’s law. The force drop data also exhibited good power law behavior. Moreover, the Weibull distribution of the peak stress and accumulated energy up to the peak state were established. Although carbonate sand had two failure modes in the experiments, these modes had the same statistical properties in terms of both mechanics and AE.

This paper presents a series of field snap-back experiments of a soil-footing-structure system equipped with rocking foundation on a cohesive soil. The objective was to investigate the nonlinear dynamic behavior of the rocking system subjected to particularly pulse-like motions. During the snap-back tests, an initial drift ratio was applied to the deck, at a maximum of 8.5%, and then released using a quick release mechanism to enable the free vibration of the system. Effects of initial factor of safety against the bearing failure, initial drift amplitude, and snap-back directions on the dynamic properties of the rocking system were investigated. Test results show that the rocking moment versus footing rotation is highly nonlinear and the moment capacity can be well predicted on cohesive soil. The shear capacity of footing did not significantly change with the number of trials or amplitude of initial drift. The damping ratio observed during the oscillations after snap-back release of the shallow foundations ranged from 8% to 30%. The average measured period of the rocking system was elongated by approximately 235% compared with the period of a fixed-base structure. An acceptably small residual settlement was observed even at a high cumulative rotation. The rocking system on clay exhibited a good recentering ability, which is even better than on sand. Finally, the increase in the density and shear strength of soil beneath the footing due to rocking cycles was observed.

Ground vibrations induced by human activities that can be considered a statistically stationary process can be represented by analytical solutions to Lamb’s problem. For a viscously damped half-space modeled as a Kelvin-Voigt solid, the attenuation is governed by radiation and an exponential law with an argument dependent on the soil’s damping ratio and Rayleigh wavelength. An estimator of the damping ratio is presented based on an energy analysis, and a field scale is introduced to filter near-field components from measurements. A spectral analysis of surface waves (SASW)–type test is used to determine the Rayleigh wave velocity through a frequency wavenumber transformation of the wave field, and the vibrations caused by a periodic excitation are used to determine the damping ratio. A comparison against a pseudo-attenuation power law is presented in terms of ground vibration prediction.

A failed embankment on a cement deep mixing (CDM)-formed column–improved soft clay deposit in Saga, Japan, has been reported and analyzed. Based on the results of the field investigation and numerical simulation, the postulated failure mechanism is that columns under the failed section failed by bending (tension), which caused the whole embankment system to collapse. However, bending failure of columns is not necessarily checked in the current design process in Japan. In addition, it has been found that the limited number of all-core boring checks as adopted in Japan cannot guarantee the quality of all constructed columns, and development of a more robust field quality-control technique is urgently needed. It has also been found that for an embankment system with a lower factor of safety, relatively large deformation of the system may cause cracks in the embankment; at the cracked locations, the shear strength ($s_u$) will practically reduce to zero. This phenomenon has to be considered in deformation and stability analyses. Finally, the numerical results indicate that in the design of a reinforced embankment slope on a soft clay deposit, both the stability of the reinforced slope itself and the interaction between the embankment and soft clay deposit should be considered.

The performance of Çark Canal in the 1999 $\mathrm{M}=7.5$ Kocaeli earthquake was evaluated using common liquefaction vulnerability index (LVI) methods, a nonlinear dynamic analysis (NDA) method, and a Newmark sliding block method to examine possible factors contributing to why different analysis approaches often overestimate liquefaction effects in interbedded deposits. The characterization of the interbedded fluvial stratum based on cone penetration test (CPT) data utilized an inverse filtering procedure to correct CPT data for thin-layer and transition zone effects. Common LVIs computed using the measured and inverse-filtered CPT data with a site-specific fines content calibration showed that the combination of these two steps reduced the LVIs by 30%–50% for this site and seismic loading. Two-dimensional NDAs were performed using stochastic realizations for the interbedded stratum and the PM4Sand and PM4Silt constitutive models for the sandlike and claylike portions, respectively. Computed deformations were evaluated for their sensitivity to stochastic model parameters, the cyclic strength assigned to the sandlike soils, the undrained shear strengths assigned to the claylike soils, the level of shaking, and other input parameters. Newmark sliding block analyses were performed with different allowances for the influence of interbedding on the composite strength of the interbedded stratum. The differences between results obtained with these analysis methods, along with those presented by others, provided insights into how the various factors can contribute to an overestimation of ground deformations in interbedded deposits of sands, silts, and clays.

Infiltration-induced landslides are among the most common natural disasters threatening modern civilization, but conventional methods for studying the triggering mechanisms and predicting the occurrence of these slides are limited by incomplete consideration of underlying physical processes and the lack of precision inherent in limit-equilibrium analyses. To address this problem, the spatial-temporal evolution of failure is investigated in a seasonally unstable section of an interstate highway embankment, known as the Straight Creek landslide, Colorado. The study includes multiyear site investigation, monitoring, and numerical simulation using a rigorous hydromechanical framework along with a field of local factor of safety method. The sensitivity of episodic landslide reactivation to infiltration characteristics is evaluated. Results indicate that annual cumulative snowmelt infiltration, which typically accounts for approximately 75% of total annual cumulative infiltration and occurs over a short period in the spring, has the most substantial impact on slide activation. The rate of snowmelt infiltration varies independently of annual cumulative snowmelt infiltration and cumulative infiltration in the previous year, but still affects antecedent soil-moisture conditions at the onset of snowmelt infiltration and therefore also the level of slide activation. These findings are used to establish specific thresholds for exacerbated slide movement using annual snowpack accumulation, forecasted snowmelt rate, and the previous year’s snowmelt, an approach that may be applied for predicting movement at this and other recurring or potential slide sites.

Geologic change tends to happen episodically, yet some natural slopes are more continuously active than many realize. Airborne lidar scan (ALS) data have made this evident around the tragic 2014 State Route (SR) 530 (Oso) landslide site in Washington State. ALS surveys since 2003 provide the opportunity to analyze landforms near the landslide site and their change through time. Changes can be dramatic, such as in 2014, but small changes may be more important for understanding risk. Intervals before and after the 2014 landslide, and comparison between similar slopes in the region, reveal important spatial and temporal variations. ALS data collection, change detection, and recognition of temporal and spatial variations can support regional landslide risk assessments, aid in risk communication, and promote better decision making to reduce risk from landslides. Had this practice been understood, implemented, and appropriately communicated prior to March 2014, the outcome of the Oso landslide could have been less tragic. This lesson is important for all levels of government, infrastructure owners, businesses, and the public.

This paper discusses the results of an experimental program to study the compressibility of mixtures of kaolin and diatom microfossils, particularly the effects of diatomite content (DC) on consolidation, swelling, and long-term compression. Thirty long- and short-term oedometer tests were performed on laboratory-sedimented, preconsolidated specimens of diatomite–kaolin (D-K) mixtures. The compression and swelling of the mixtures were affected by the DC, especially when the DC was 60% (by dry mass) or greater. The effect of preconsolidation on the compression curve was much less evident as DC increased. For soils with diatoms, $C_{\alpha }$ does not have the same meaning of secondary compression or creep as for fine-grained soils. Greater $C_c$ and $C_{\alpha }$ values with increasing DC were explained by contributions from three mechanisms that may overlap during loading: faster pore pressure dissipation due to larger interparticle and intraparticle porosities, rearrangement and bending of kaolin particles around frustules, and elastic compression and eventually breakage of frustule particles.

Soils reinforced with randomly distributed fibers will have higher shear strength and improved mechanical properties compared to unreinforced soil. Most of the previous research on fiber reinforcement focused on the behavior when the governing mode of failure is the pullout of fibers from a fiber matrix. In recent years, fibers with relatively low tensile strength (e.g., fibers made from recycled products or natural plant fibers) have been considered for soil reinforcement, but their mechanical response has not been studied extensively. In this paper, an experimental testing program is conducted using intentionally selected weak fibers (paper strip). The intention is not to demonstrate the usage of paper fibers as a reinforcement material, but to study the stress-strain behavior and shear strength envelope of fiber-reinforced soil when the governing mode of failure is fiber breakage.

When the ground is subject to dynamic compaction such as aircraft wheel loading and pile driving, the wave dissipates in soil, which has not been fully understood qualitatively and quantitatively. This paper reports a series of split-Hopkinson pressure bar (SHPB) tests on silica and calcareous sands with various length-to-diameter ratios, initial void ratios, and degrees of saturation. A dimensionless parameter, the modified attenuation coefficient, is introduced to quantify the wave dissipation in sand. It is found that the modified attenuation coefficient of dry sand increases linearly with the initial void ratio. The modified attenuation coefficient of unsaturated sand first increases with the degree of saturation and then decreases. The peak attenuation coefficient corresponds to the largest capacity of wave dissipation and the smallest loaded area. Based on experimental data, semiempirical predictive equations are obtained. The capacity of wave dissipation in the studied sand with various initial void ratios and moisture contents can be predicted preliminarily by four SHPB tests and the semiempirical equations.

Microbial-induced calcium carbonate precipitation (MICP) and enzyme-induced calcium carbonate precipitation (EICP) are both soil improvement techniques that improve the shear response of sands. However, the source of urease to hydrolyze the urea is different between the two techniques, and these differences may result in different shear responses. The macro- and microscale behavior of MICP- and EICP-treated sands are evaluated using triaxial tests and scanning electron microscopy (SEM) images. To compare the macroscale behavior, triaxial specimens were treated using MICP and EICP techniques to reach a moderate level of cementation, assessed using shear wave velocity. EICP-treated sand needs less calcium carbonate than MICP-treated sand to reach the same shear wave velocity. The specimens were sheared under drained conditions, and shear responses are compared. The obtained results show that a higher shear strength and larger dilative strain were observed for MICP-treated sand compared to EICP-treated sand when treated to the same shear wave velocity; however, more injections were required for the MICP treatment, which resulted in a higher carbonate content. The SEM images revealed that the shape and structure of precipitated ${\mathrm{CaCO}}_3$ is different in these two treatment techniques, which in turn likely influenced the macroscale response. The advantages of each method are also discussed.

A flow-through column test setup was developed to measure the breakthrough curves of ${}^{133}\mathrm{cesium}$ (Cs) and ${}^{88}\mathrm{strontium}$ (Sr) cations in a natural silty sand. Advantages of this column setup include ensuring full saturation with a back-pressure technique and maintaining a constant hydraulic gradient condition with overflow design. The former eliminates large variations in retardation factor ($R_d$) from reduced surface sites for contaminant-retarding reactions and increased duration time, both caused by unsaturation. The latter creates a more realistic simulation of the field condition than a constant-flow-rate setup. The retardation factors of Sr and Cs cations were found to be 3.561 and 27.369, which were slightly lower than the range under similar but broader ranges of fines content and pH. This slight difference is attributed to the lower fines content of the soil, high input concentrations of both Cs and Sr, and the competing monovalent and divalent cations in the influent with high ionic strength. Although not significant in this study, particle migration was observed.