Geo-Congress 2024: Geotechnics of Natural Hazards

Saturated oil sands tailings can be susceptible to static liquefaction if deposited loosely. The occurrence of static liquefaction can thus pose a major risk to an oil sands tailings dam. This study presents the results of a series of monotonic undrained and drained triaxial compression tests on moist-tamped specimens of coarse oil sands tailings. The experiments were conducted on specimens subjected to isotropic and laterally confined (K₀) consolidation loads to assess the effect of stress anisotropy and initial shear stress on the liquefaction behavior of oil sands tailings. The triggering and post-liquefaction undrained strengths normalized by the major consolidation stress were observed to decrease with decreasing relative density or increasing void ratio. A significant effect of anisotropic consolidation was observed, causing higher liquefaction triggering strengths in K₀-consolidated specimens than those mobilized in isotropically consolidated specimens. This was, however, diminished at large strains resulting in similar post-liquefaction undrained strength ratios.

Monopile foundations are known as the most common foundation solution for offshore wind turbines (OWTs). However, the state of practice for designing monopile foundations in high seismicity areas is still limited. In this paper, three-dimensional, fully coupled, nonlinear finite-element analyses were used to evaluate the seismic performance of hypothetical 5MW offshore wind turbines on monopile foundations in layered, liquefiable sites under motions with and without forward directivity. The numerical results showed that pile movements induced by wind loading led to a bias in settlement accumulation near the foundation. Velocity pulses increased the cyclic stress demand in soil and the potential for liquefaction triggering. The foundation rotations were influenced by ground motion characteristics such as polarity and velocity impulse, and the magnitude and direction of the applied wind load. This study highlights the importance of considering the effects of combined loads and pulse-like motions in the design and performance of OWT systems.

Performing nonlinear response history analyses for structural design and site ground motion response analyses requires selecting a suite of representative input ground motions as input to the analyses. Each selected ground motion can be amplitude-scaled such that the mean response spectrum (or resultant spectrum) of the entire suite matches approximately to a target spectrum. Spectral matching, such as tight spectral matching and mean spectral matching, can also be used to further adjust the selected suite of ground motions to produce a closer match of the suite mean to the target spectrum. This study proposes a new approach to mean spectral matching practice that defines the target variation (dispersion) within the ground motion suite to the probabilistic seismic hazard analysis framework. By using a fractile analysis, the dispersion of ground motions can be quantified to produce a more realistic variability that is consistent with the variability from the probabilistic seismic hazard analysis. A case study and scaling algorithm is presented. Two spectral matching tools, namely RSPMatch and REQPY, are used to modify the seed ground motions, and the results show the proposed method can be a potential expansion to the mean spectral matching method.

In the northwestern Himalayan region of Jammu and Kashmir, earthquakes of moderate to large magnitude were common. The development of infrastructure projects in this region has accelerated over the last two decades. Earthquake-resistant structural elements of any development project are extremely difficult to design, especially in seismically active areas. The seismic fragility curves for various tunnels located in three phases of the Udhampur Srinagar Baramulla Rail Link (USBRL) Project were developed in this paper. According to the findings of this study, the majority of the tunnels in Phase 1 of this project are subject to extensive damage. Active tectonic sources in the near field, weathered rock conditions, high seismicity, and landslide vulnerability all contributed to portal damage and significant lining failure at such sites. This research will aid design engineers in their advocacy for earthquake-resistant tunnels and underground facilities in Jammu and Kashmir. It will pave the way for the design of earthquake-resistant infrastructure projects in the Himalayas.

Cyclic triaxial tests have been used to evaluate the liquefaction susceptibility of cohesionless soils since the 1960s. While there is general agreement of test procedure for cyclic triaxial tests, one aspect of cyclic triaxial testing that is not standardized is the criterion chosen as the definition of liquefaction. The definition of liquefaction used to evaluate the cyclic triaxial test data can have a significant effect on subsequent analyses. In an attempt to quantify the effects of different liquefaction criteria, the results of over 250 cyclic triaxial tests were evaluated under a series of stress-based and strain-based liquefaction criteria. During this evaluation, a special focus was placed on the effects of specimen relative density and non-plastic fines content on the results obtained using different liquefaction criteria. It was found that if the soil is susceptible to flow liquefaction failures, there is little difference in the number of cycles of loading to cause liquefaction among the different failure criteria evaluated. Conversely, if the soil is susceptible to cyclic mobility/limited liquefaction failures, the number of cycles of loading to cause liquefaction varied significantly between the various failure criteria.

While the liquefaction susceptibility of fully saturated clean sands and their mixtures with low-plasticity fines has long been recognized in liquefaction engineering, gravelly soils were traditionally considered non-liquefiable due to their high pore pressure dissipation capacity, attributed to their larger grain sizes. However, with the increasing construction of gravelly earth fills, concerns about their liquefaction susceptibility have grown. Surprisingly, in these man-made earth fills, loose states were observed in some gravelly soil layers. The 2008 Wenchuan earthquake (M_w = 7.9) provided case histories revealing that natural gravelly soils can also exist in a loose state and, furthermore, they can liquefy. To assess this, probabilistic case history-based, liquefaction-triggering relationships have been developed. This paper discusses 65 available case histories of gravelly soil liquefaction, compiled from four earthquakes with magnitudes ranging from 6.5 to 9.2. It also explores the advantages of using alternative in situ testing methods such as the dynamic penetration test (DPT), large penetration test (LPT), Becker penetration test (BPT), and geophysical surveys like shear wave velocity (V_s) rather than relying solely on the standard penetration test (SPT) and cone penetration test (CPT). Simplified procedures are employed to assess the liquefaction-triggering potential of gravelly soil layers. The assessment process begins with identifying the susceptible critical layer, estimating in situ density, groundwater table depth, seismic intensity, and duration parameters, and considering grain size gradation characteristics, with an emphasis on addressing their uncertainties. The assessment results are presented in the cyclic stress ratio (CSR) vs. DPT blow count (N′₁₂₀) domain. Based on the developed case history database, probability-based liquefaction-triggering boundary curves have been established for engineering practice. Finally, these curves are compared with existing probabilistic models found in the literature.

This study presents the experimental investigation on the effect of loading frequency on the long-term cyclic response of coal ash under as-compacted conditions by performing cyclic triaxial testing. The specimens were prepared using the moist tamping method at 95% MDD (maximum dry density) and OMC (optimum moisture content) of coal ash. The frequency varied from 0.1 to 9 Hz at a cyclic stress ratio (CSR) of 0.15. The effective confining pressure was kept as 70 kPa for all the cyclic triaxial tests. The specimens were cyclically loaded for 20,000 loading cycles simulating long-term cyclic loading conditions. Initially, a static stress of 30 kPa in addition to the confining pressure (70 kPa) was applied before the application of cyclic loading. The cyclic loading was applied in the sinusoidal waveform in purely compressive mode. Total vertical deformation was determined as the summation of elastic/resilient and permanent deformation due to the application of long-term cyclic loading under cyclic triaxial conditions. Permanent deformation is defined as the accumulated plastic strain, which is non-recoverable on the application of cyclic loading. The dynamic modulus and stiffness degradation ratio were also evaluated with respect to the number of loading cycles. The results indicated that permanent vertical strain was found to reduce with frequency from 1 to 9 Hz for all the loading cycles. Dynamic modulus decreased with increasing number of loading cycles for all the frequencies (1−9 Hz), but became constant at a larger number of loading cycles.

The current state of practice for designing dense granular columns (DGCs) relies heavily on simplified procedures that assume free-field conditions (no structure or slope) and uniformly layered, level soil deposits composed of clean sand. These guidelines ignore stratigraphic variabilities in the permeability, groundwater table, layer thickness, or relative density of soil layers commonly found in natural deposits. Prior research has shown that such variability can significantly influence the contribution of different mechanisms of displacement, excess pore water pressure generation and redistribution, formation of soil ejecta at the ground surface, accelerations, and subsequent damage to the foundation and structure. These effects and the implications on system performance are poorly understood and, hence, not considered in the design of mitigation strategies. In this paper, fully coupled, three-dimensional (3D), nonlinear dynamic finite-element analyses in OpenSees, validated with centrifuge models, are performed to evaluate fundamentally how DGCs influence the seismic performance of sites with realistic stratigraphy and their overlying shallow-founded structures. The effectiveness of drainage and reinforcement provided by DGCs is shown to depend strongly on the heterogeneity of the soil profile. Draining DGCs are shown to have the potential to effectively reduce the permanent settlement of the foundation compared to an unmitigated structure. In addition, drains with an area replacement ratio (A_r) greater than 20% significantly reduced the severity of ejecta (quantified through hydraulic gradients) and excess pore pressure ratios in the liquefiable layers. This reduction was especially effective in the case when DGCs were accompanied by densification. However, treatment could adversely impact the acceleration demand transferred to the superstructure due to reduced damping and increased soil stiffness. The results highlight the critical importance of considering stratigraphic variations in the design of mitigation strategies that holistically improve the performance of the soil-foundation-structure system.

Geotechnical engineers often need to complete geotechnical site investigations with one of the outputs being the completion of liquefaction triggering assessments. Typically, these assessments rely on empirical procedures that have been developed from seismic case history data and use of various in situ test methods. The numerous investigation methods available each have their own different considerations for their use for these assessments such as the application of test specific or more general correction factors. In a perfect world, the liquefaction triggering conducted by the different assessment methods would yield the same level of liquefaction susceptibility for the same soil unit. Unfortunately, differences between the outputs of the triggering procedures and other epistemic uncertainties often occur leading to inconsistencies. This paper presents a case study from a recent project in the lower mainland reviewing different investigation methods and their respective liquefaction triggering assessments. In addition, lab tests conducted on undisturbed samples were compared to the empirically based triggering methods.

Fine-grained soils subjected to seismic loading often exhibit instability or failure of slopes, foundations, and embankments. To understand the behavior of clay soils under multiple earthquake loads, kaolinite samples were prepared and tested in the laboratory using a cyclic simple shear device. Each sample was subjected to two cyclic events separated by different degrees of reconsolidation periods to simulate different levels of excess pore water pressure dissipation. The results indicated that the degree to which excess pore water pressure generated during the first cyclic event was dissipated affected the cyclic resistance of the soil during the second cyclic event. The post-cyclic undrained shear strength was also found to be a function of the degree to which excess pore water pressure from the first cyclic load was allowed to dissipate prior to the application of the second cyclic load.

Southwest Christchurch, New Zealand, with thick successions of thinly interbedded fine sand and silt swamp deposits, had no-to-marginal liquefaction ejecta in the 2010–2011 Canterbury earthquakes even though state-of-practice liquefaction assessment procedures indicated severe ground failure would occur. To understand reasons for this discrepancy, the first cyclic simple shear tests were performed on high-quality “undisturbed” specimens of Christchurch silty soil. An alternative Japanese Standard JIS A 1224:2009 Test Method was developed to evaluate the minimum and maximum void ratios of the cyclic test specimens and establish their relative densities. The cyclic test specimens of the same soil unit were then mixed and reconstituted for steady-state testing in a triaxial device. This paper presents the stress-strain relationships, cyclic resistance ratio curves, and steady-state lines for three silty soils. The silty soils exhibited cyclic mobility with limited strain potential in the cyclic simple shear tests. The same dilative tendencies of the soil at its current state and effective stress were confirmed by the steady-state test results.

Realistic strong-motion accelerograms of earthquakes are required for various earthquake engineering tasks, including modeling structural and site response to large and near-source events. In this work, we introduce a data-driven framework for three-component ground motion synthesis intended for engineering applications. Leveraging the increase of ground-motion data from seismic networks and recent advancements in machine learning, we train a generative adversarial neural operator (GANO) to produce realistic three-component acceleration time histories conditioned on moment magnitude (M), rupture distance (Rrup), time-average shear-wave velocity at the top 30 m (Vs₃₀) based on a California dataset compiled from PEER NGA-West2 database, and a public DesignSafe California database. The results show that the framework can efficiently recover the magnitude, distance, and Vs₃₀ scaling of Fourier amplitude and pseudo-spectral accelerations. Through a comprehensive residual analysis using empirical data, we have verified that our model accurately captures both the mean values and aleatory variability of the evaluated ground-motion parameters.

Modeling uncertainty was assessed for nonlinear seismic ground response analyses at the Christchurch Hospital strong motion station (CHHC). Ground response analyses in the central business district of Christchurch must consider a clay layer at depth, and the approach used to discretize this layer results in different modeling uncertainty. The clay layer creates a shear wave velocity (V_s) inversion that attenuates short-to-moderate-period motions, which can underestimate surface response spectra. A design approach developed for a nearby site was applied at CHHC, comprising development of a smoothed V_s profile with a minimum V_s for the clay layer. Input motions were selected to represent the M7.1 September 4, 2010, Darfield and M6.2 February 22, 2011, Christchurch earthquakes. The design approach yielded mixed results between the input motions when applied to CHHC, yet the average modeling uncertainty was smallest using the design approach instead of explicitly modeling the clay with its estimated in situ V_s.

The increasing interest in studying diatomaceous earth stems from the challenges posed by their presence in various engineering projects, such as the US 97 at Wickiup Junction project in Oregon. Diatomaceous earth consists of fossilized remains of diatoms, which have a highly varied and interlocking shape, giving the impression of strength until the skeletons crush under excessive stress. The engineering properties and cyclic performance of diatomaceous earth are not well understood. This paper presents and discusses the results of geotechnical laboratory tests conducted on diatomaceous earth from Northern California, including grain-size distribution, Atterberg limits, specific gravity, direct shear, and 1-D consolidation. The soil’s performance under cyclic stress was evaluated through a series of cyclic triaxial shear tests. The required numbers of cycles to cause the cyclic failure of the diatomaceous earth sample under two confining pressures (103 and 52 kPa) were presented. The cyclic stress-strain responses of diatomaceous earth exhibit characteristics of cyclic softening, similar to behaviors of clay-like soils.

The assessment of the seismic performance of geo-structures via numerical modeling is crucial for ensuring their safety and serviceability. While the capability of numerical models to predict liquefaction in uniform clean sands has been widely studied, less attention has been given to reproducing the behavior of well-graded gravels using recorded seismic events. To this aim, this study simulates the dynamic behavior of a well-graded gravelly soil instrumented in the vertical array of Port Island, Japan, in response to the 1995 Kobe earthquake, utilizing both total and effective stress analyses according to both fully coupled and loosely coupled approaches. The calibration of the models is based on the results of site investigations, with a focus on laboratory tests collected in previous studies. The comparison between simulated and observed soil response contributes to improving the reproducibility of the nonlinear behavior of man-made gravelly soils, with potential implications for the design and verification of geo-structures.

Physics-based ground motion simulations are a valuable tool for studying seismic sources with missing historical records, such as Cascadia Subduction Zone (CSZ) interface earthquakes. The last such event occurred in 1700 CE and is believed to be an M8-M9 rupture. The United States Geological Survey recently developed 30 physics-based simulations of a CSZ rupture to predict ground motions across the Pacific Northwest. Consideration of key modeling uncertainties across these simulations leads to estimates of ground motion intensity that vary by ~100% in some areas (e.g., Seattle). Paleoliquefaction, or soil liquefaction from past earthquakes, provides the best geologic evidence for constraining or “ground truthing” the intensity of past shaking, yet while paleoliquefaction has been documented throughout Cascadia, limited analyses have been performed to exploit this evidence. This study focuses on Kellogg Island, 2 mi south of Seattle, where liquefaction has been documented from several earthquakes, but not from the 1700 CE event. Therefore, using the CSZ simulations and in situ cone penetration test data, this study predicts the probability of surficial liquefaction manifestation at Kellogg Island during an M9 CSZ event. As part of this effort, velocity profiles are developed from multichannel analysis of surface waves, and non-linear site response analyses are used to propagate simulated motions to the surface. Results show a high probability of liquefaction near Kellogg Island for most simulations, whereas to date no evidence of 1700 CE liquefaction has been discovered at Kellogg Island, nor at any other location in the Puget Sound. The discrepancy between predictions and observations might indicate that the 1700 CE ground motions were less intense in Seattle than most predictions of M9 earthquakes indicate. Toward the goal of elucidating the expected impacts of future CSZ earthquakes, similar analyses are ongoing at additional sites across the region.

As part of the next generation liquefaction (NGL) project, we are developing probabilistic triggering and manifestation models using laboratory data and cone penetration test (CPT) case histories in the NGL database. The case histories are used to develop probabilistic models for surface manifestation conditional on susceptibility, liquefaction triggering, soil properties, stratigraphic details, and other features. Susceptibility is interpreted as a sole function of soil composition and is expressed as a probabilistic function of soil behavior type index, I_c, obtained from CPT. A triggering model is derived based on laboratory tests on high-quality specimens from literature; this model captures mean responses and uncertainty reflective of data dispersion and is considered as a Bayesian prior that will subsequently be updated by field observation data. A manifestation model is then regressed from field case histories where surface manifestation was or was not observed, information on soil conditions that enables identification of layers likely to liquefy, and ground shaking conditions. We describe the approach applied to develop our manifestation model; for a given layer this model considers layer depth, thickness, CPT tip resistance, and I_c. The result of this process is a logistic function in which manifestation probability decreases with increasing depth, decreasing thickness, increasing tip resistance, and increasing I_c. Profile manifestation is then derived by aggregating individual layer manifestation probabilities.

Evaluations of liquefaction triggering and effects are commonly assessed by representing demand with intensity measures (IMs) such as peak ground acceleration (PGA), supplemented with earthquake magnitude (M). Past approaches estimated IMs at liquefaction case history sites by taking the recorded value from a nearby seismic station, estimating the IM using ground motion models or 1D site response analyses, and/or based on judgment. These approaches might not account for one or both of the following: (1) the differences in path and site effects between the site of interest and the nearest recording; and (2) the IM spatial correlation structure. A framework that addresses these limitations is presented and used to estimate PGA values at case history sites of the 1989 Loma Prieta Earthquake as a case example. Findings from this study suggest that PGAs computed using the presented framework differ from those traditionally used in the development of liquefaction triggering models.

This paper evaluates the large-strain (>0.2%) predictions of a new shear modulus reduction model for residual soil and saprolite in South Carolina using estimates of peak shear strength. The shear modulus reduction model was derived from available laboratory resonant column (RC) test measurements by other investigators on samples from the Piedmont regions of Alabama, North Carolina, South Carolina, and Virginia. Nearly all the compiled RC test measurements were made at shear strains less than 0.2%. Engineering properties needed to complete the evaluation (e.g., small-strain shear-wave velocity, total unit weight, plasticity index, dynamic peak shear strength) and their uncertainties are discussed in this paper. It is found that the dynamic peak shear strengths implied by the modulus reduction model are significantly greater than those estimated from published effective stress triaxial test results for unsaturated and saturated residual soil and saprolite specimens. A procedure for correcting the modulus reduction curves at large strains is described. The results are being used in site response analyses to develop amplification factors compatible with newly developed statewide seismic hazard maps for use by the South Carolina Department of Transportation.

As of May 2023, the Ministry of Oceans and Fisheries (MOF) in Korea is operating a port alert system for seismic response at 28 stations centered on 13 trade ports to monitor the stability of the port structures rapidly after earthquakes. The peak ground acceleration according to measuring stations can be analyzed using the data processing algorithm. Based on this, we review the excess rate of the design acceleration for port structures during earthquakes and utilize them as an emergency safety check. It plays a significant role in operating intelligent situation management under earthquake disasters. This system makes it possible to make quick decisions and respond to earthquake disaster fields in ports. This paper overviews the smart disaster management system for ports in Korea, with priority given to the response stage. And it introduced the application of these measurement data processing algorithms.

Understanding soil behavior under different strain rates is a key factor in many geotechnical applications, including earthquakes, dynamic compaction, rapid pile testing, roadway subgrade design, and projectile penetration. In this study, the stress-strain response of a clayey sand mixture at strain rates ranging from 0.0001/s to 10/s was studied. Remolded samples were prepared using a mixed soil consisting of 30% clay and 70% sand at a water content of 11%. This material is believed to represent materials commonly encountered in several formerly used defense sites that are in need of environmental remediation. The information is helpful for predicting the likely depth of burial of projectiles within the material to be remediated. Unconfined compression and unconsolidated undrained (UU) triaxial tests were conducted on 38-mm diameter cylindrical test specimens that were formed using previously hydrated mixed soils. The specimens were statically compacted at a constant rate of 1 mm/min. A hydraulic loading system equipped with an ultra-precise load cell and data acquisition system was used to capture load during tests. A strain rate logarithmic correlation was fitted to both unconfined and triaxial test results. Visual inspection of the test specimens suggests that rate dependence is due in part to changes in the failure mode. Test results can be implemented to account for the effect of strain rate in numerical simulation and analytical models.

The current study aims to investigate the potential of dual barriers in mitigating the vibrations induced due to impact loading. Field tests were conducted to understand the efficacy of the dual open and geofoam-infilled barriers. In the field tests, impact loading was applied to the soil system by a mechanical loading device consisting of weight dropping assembly. The amplitude of vertical velocities was recorded at designated locations before and after the construction of the barriers. The performance of dual open and geofoam-infilled barriers was compared with that of single open and geofoam-infilled barriers. The isolation efficacy of dual barriers was observed to be superior to that of the single barriers. The average amplitude reduction ratios for the dual-infilled and dual-open barriers were reported to be 31% and 29% lesser than the single-infilled and single-open barriers, respectively. The isolation efficiencies for the dual open barriers with depths of 1 and 1.5 m were observed as 68% and 74%, respectively. The findings from the study support the usage of dual barriers in place of single barriers.

Ring foundations provide better seismic performance over other foundations due to their inherent stiffness and even load distribution capabilities. This urges for the seismic stability analysis of these foundations. In the present study, the seismic stability of ring footing on homogeneous soil is performed by a pseudo-static approach. In this analysis, the foundation behavior is simulated as a rigid body. The seismic loads in this analysis are modeled as vertical and horizontal forces. The analysis is performed in ABAQUS Cae software where the Mohr-Coulomb plasticity model is used to model the soil. The effect of variation of the friction angle (ϕ) of the soil, seismic acceleration coefficient (k_h and k_v), and loading position on the ultimate bearing capacity in static, as well as seismic conditions, is also presented in this paper. Findings indicated that higher values of seismic acceleration coefficient correlated with diminished bearing capacity, while higher friction angles contributed to its enhancement. Maximum bearing capacity was obtained for the inner half-loaded ring out of all possible loading combinations considered here.

The abundance of post-earthquake data from the Canterbury, New Zealand (NZ), area can be leveraged for exploring machine learning (ML) opportunities for geotechnical earthquake engineering. Herein, random forest (RF) is chosen as the ML model to be utilized as it is a powerful non-parametric classification model that can also calculate global feature importance post-model building. The results and procedure are presented of building a multiclass liquefaction manifestation classification RF model with features engineered to preserve special relationships. The RF model hyperparameters are optimized with a two-step fivefold cross-validation grid search to avoid overfitting. The overall model accuracy is 96% over six ordinal categories predicting over the Canterbury earthquake sequence measurements from 2010, 2011, and 2016. The resultant RF model can serve as a blueprint for incorporation of other sources of physical data such as geological maps to widen the bounds of model usability.

This study utilizes the discrete element method (DEM) to investigate the mechanical behavior of a pressurized sand damper (PSD) and characterizes the dissipated energy under cyclic loading. The idea of a PSD is to exploit the increase in shearing resistance of sand under external pressure and the associated ability to dissipate energy through interparticle contact sliding. DEM employs a simple linear contact model for the entire assembly and utilizes irregularly shaped particles to mimic the behavior of sand grains. The series of DEM simulations reported herein examine the effects of multiple parameters on the magnitude of dissipated energy. These parameters include stroke amplitude, grain size distribution, the magnitude of pressure imposed on the sand, and different geometric configurations of the PSD. The results reveal that the main energy dissipation mechanism is interparticle frictional sliding in the sand. The numerical results compare favorably with experimental data recorded from a PSD that was subjected to cyclic testing.

The objective of the study is to assess when liquefaction is triggered in a suite of ground motions following simplified approaches and measure the remaining post-triggering energy content of those ground motions. For liquefaction-induced deformations, current simplified analysis procedures do not directly incorporate temporal effects and rely on peak transient intensity measurements. Liquefaction hazard from short-duration, small to moderate-magnitude (M) earthquakes (M4.5–7.5) is adequately expressed using transient intensity measurements. However, subduction-zone interface earthquakes can have magnitudes greater than 9.0, with ground-motion durations exceeding 300 s. Using 525 ground motions from the NGA-Subduction (NGA-Sub) database for subduction-zone earthquakes with M8.25–9.25, the timing of liquefaction was calculated using cyclic counting procedures by assuming a reference stress condition and incorporating cyclic strengths from laboratory element testing. A complementary analysis was completed using 514 crustal ground motion records from the NGA-West2 database for M6.75–7.75. Several trends were identified during this study. First, liquefaction will likely trigger during the first half of the ground motion duration, independent of the earthquake source type. However, subduction-zone motions have larger post-triggering energy content compared to crustal earthquakes. The findings from this work indicate that accurately predicting liquefaction-induced deformations from subduction-zone earthquakes may be substantially improved by using robust time-based liquefaction analysis procedures.

The liquefaction response of a site is attributed to a variety of factors including the configuration of the site’s stratigraphy and interaction of its layers and interlayers. However, the effects of configuration and interaction of soil units have been overlooked by the simplified liquefaction assessment methods that are currently widely used by practitioners for assessing liquefaction effects in a site, resulting in the overestimation of liquefaction manifestations in many cases. One of the cases that could highlight the role of a site’s configuration is the presence of a liquefiable interlayer in a profile mainly consisting of liquefaction-susceptible deposits. This study uses an advanced nonlinear dynamic analysis (NDA) procedure in a finite difference platform to simulate the response of a synthetic liquefaction-susceptible site with a silty liquefiable interlayer to seismic loading to investigate how the interlayer presence affects the system response. The effects of the liquefiable interlayer are evaluated using liquefaction triggering and manifestation parameters in the profile of the site and motion responses on the ground surface. This study also accounts for the role of interlayer thickness by developing NDAs with varying interlayer thicknesses. The soil properties used for the synthetic profile in this study are from a calibrated and validated NDA for the Wildlife Liquefaction Array (WLA) site thereby, presenting realistic materials. The results of this study indicated that contrary to the prediction of simplified methods, the presence of a liquefiable interlayer in the middle of the profile could considerably alleviate the potential shaking and liquefaction deformation damages on the surface.

Accurate seismic site response prediction is vital for resilient earthquake-resistant infrastructure. Nonlinear site response analysis, widely recognized for its accuracy across a broad range of shaking levels and soil stiffnesses, lacks clear guidelines for model selection and calibration. This study investigates the impact of DEEPSOIL’s constitutive models on surface response spectra, shear strains, and peak accelerations in South Carolina’s Blue Ridge and Piedmont regions. Utilizing the modified Kodner-Zelasko (MKZ), general quadratic/hyperbolic (GQ/H), and Yee et al. models, calibrated using DEEPSOIL’s MRDF technique, it was observed that the GQ/H model aligned best with low shear strain data. However, shear strength was underestimated across models, with the Yee et al. model exhibiting unrealistic oscillations. The GQ/H model consistently predicted lower peak accelerations and larger shear strains when using Kobe, Parkfield, Coyote, and Val-des-Bois motions. The characteristics of ground motion significantly influenced computed responses. Further studies are needed for model validation and optimal response prediction.

Liquefaction is a calamitous phenomenon that threatens the safety of infrastructure and buildings constructed in granular deposits during earthquakes. According to the response of different case histories to previous earthquakes, it has been found that the pre-seismic history significantly influences the post-liquefaction behavior of soils. To this end, a shaking table test was conducted to investigate the impact of past earthquakes or aftershocks on the liquefaction potential of saturated sands. A clean sand sample constructed in a laminar box was subjected to multiple seismic events (events A, B, and C). A series of accelerometers, pore water pressure transducer, and linear variable differential transducers (LVDT) were used to analyze the soil behavior during the shakings. The experimental results revealed that with increasing the number of shakings, settlement rate decreases due to an increase in the relative density of soil. Moreover, the excess pore water pressure (EPWP) generated during the shaking reduces as a consequence of previous shakings. Under the condition of no liquefaction, it was noted that the acceleration amplitude increases from the base to the surface of the sample.

The state-of-practice soil-structure interaction (SSI) analysis is based on analytical models with simplifying assumptions regarding the soil-structure system behavior. There is, however, a lack of validation studies of the available analytical solutions. In this study, we propose validating the existing analytical models through identifying soil-structure systems, using their real-world measured responses, and comparing the identified models to their analytical counterparts. The proposed soil-structure system identification framework is based on a Bayesian time-domain model updating and parameter estimation technique. In this paper, the proposed framework is employed for identifying a test structure located in Garner Valley, California, using its recorded response during a forced-vibration test. The estimated values of the soil-structure model parameters show a notable discrepancy with their analytical equivalents. The potential sources of this observed discrepancy are discussed, and a refined solution is proposed.

This study presents an improved numerical model for simulating cyclic liquefaction-induced lateral spreading. The enhancement is achieved by incorporating the effects of static shear stresses on the undrained cyclic shearing of sands in the SANISAND-MSf constitutive framework. This improvement allows the model to capture the undrained response of sands for different densities and stress states. The model is implemented in the finite element-based platform OpenSees for application to dynamic problems. The performance of the model is assessed by simulating cyclic direct simple shear tests and centrifuge experiments of mildly inclined liquefiable sand deposits, specifically designed to study lateral spreading. The results of the simulations demonstrate the effectiveness of the SANISAND-MSf model in replicating the liquefaction response observed in the centrifuge experiments, including the triggering of cyclic liquefaction and the subsequent development of large shear strains, which are key drivers of lateral spreading. The improved predictive capabilities of this constitutive model, particularly through the incorporation of the effect of static shear stresses, can help to better assess and mitigate the risks associated with liquefaction-induced lateral spreading during earthquakes.

The seismic performance of structures is a critical aspect of earthquake risk mitigation, and it relies heavily on seismic hazard analysis. The hazard analysis provides valuable information about the potential severity of earthquakes in Ahmedabad, which is essential for determining appropriate design criteria and building codes. Integrating seismic hazard analysis in the design phase helps engineer structures to withstand expected seismic forces, thus lowering the risk of structural failure and minimizing potential damage and losses. This study’s primary objective is to facilitate the development of peak ground acceleration at the bedrock level in the Ahmedabad region by performing DSHA and PSHA. This information can be utilized to calculate spectral acceleration in various soil conditions, aiding in the formulation of hazard mitigation strategies for Gujarat’s major city. This paper analyzes seismic hazards in mainland Gujarat and surface-level characteristics for structural seismic performance.

Non-linear dynamic analyses (NDAs) are widely used in engineering practice to evaluate the seismic performance of geotechnical structures affected by liquefaction or cyclic softening. The quality of results from an NDA study depends on several technical and nontechnical factors. Validation, wherein a numerical prediction is compared to its physical counterpart, can assess the ability of an NDA to capture the various metrics of the response and potentially provide guidance toward improving the prediction. This study investigates select methodologies and validation metrics commonly used in signal processing problems to assess their effectiveness in capturing discrepancies between experimental and simulation results for a specific response of interest. Three simple problems are initially evaluated to analyze the metrics’ capabilities and identify necessary modifications. Then, the metrics are applied to nine sets of experimental and simulation time series, focusing on one response of interest (pore water pressure). It is found that cross-correlation successfully captures the lag in the initiation of liquefaction triggering, while Russell’s error metric captures magnitude and phase discrepancies.

This paper presents a research study focusing on the impact of liquefaction-induced lateral spreading on pile foundations. Previous earthquakes have demonstrated that such lateral spreading deformations can lead to significant movement and localized plastic demands on the piles. To investigate this phenomenon, the authors conducted a 1g shake-table experiment using a medium-sized laminar soil container. In the experiment, a single reinforced concrete pile with a diameter of 25 cm was subjected to earthquake excitation in a mildly inclined soil profile. The response of the pile-soil system was analyzed using the employed dense instrumentation and post-test physical observations. The discussion encompasses various aspects, including soil and pile lateral displacement, as well as an examination of the pressure fields around the pile.

Liquefaction triggering results from 48 cyclic direct simple shear (DSS) tests are presented for Ottawa F65 sand under constant volume and level ground conditions, at a vertical stress of 100 kPa. An analytical framework is presented to relate relative density (D_R), cyclic stress ratio (CSR), and number of cycles to liquefaction (N) using a simple expression with three fitting parameters, which can provide improved interpretation of DSS test results. The expression can be rearranged to be in CSR versus N space, as is traditional when presenting DSS results, or in CSR versus D_R space, as is conventional with case history data. The mean liquefaction triggering surface for Ottawa F65 sand is presented together with an estimate of the uncertainty associated with the full experimental dataset. The results are then used to obtain element-level calibrations of the constitutive model PM4Sand across the experimental parameter range that bound the uncertainty from cyclic DSS tests.

This paper presents seismic numerical analysis of a proposed outfitting pier at Seaspan’s Vancouver Shipyards facility, located in North Vancouver, British Columbia. The study focuses on evaluating seismic liquefaction-induced deformation along the pier. Two-dimensional seismic ground deformation analyses were conducted using the finite difference computer program FLAC, incorporating advanced soil constitutive models PM4SAND and PM4SILT to simulate the response of sand and low-plasticity silt layers, respectively. The seismic response was analyzed using a dataset of 30 earthquake records, selected to capture a wide range of seismic scenarios. The analysis indicated that the nearshore slope area experiences the largest ground deformation, with magnitudes ranging from 4 to 6 m toward the downslope to the south. Beyond approximately 150 m from the north end of the pier, the deformation diminishes to insignificance. These findings align with the results obtained from the one-dimensional seismic response analysis, validating the consistency of the FLAC analysis approach. The results of the FLAC analysis were used as input in the structural analyses and design of the proposed pier’s pile foundations.

Deterministic and probabilistic procedures for estimating seismic displacements of engineered and natural slopes depend on the uncertainty of the seismic yield coefficient (k_y) and the initial fundamental period (T_s) of the potential sliding mass. However, inherent soil spatial variability within slopes can significantly contribute to the uncertainty in the potential sliding mass extent, which propagates to uncertainties in k_y and T_s. This study investigates the influence of subsurface soil variability, as modeled by non-stationary spatial random fields of the undrained shear strength, on the resulting variability of k_y and T_s for a hypothetical slope geometry. The random fields assume a lognormal distribution, with alternative assumptions for the mean, coefficient of variation, and horizontal correlation range. Pseudostatic stability analyses for determining k_y and the associated sliding mass geometry were performed using the finite difference program FLAC. The T_s was evaluated using a mass-weighting scheme and considered the influence of alternative soil shear wave velocity assumptions. The results demonstrate important considerations for interpreting the variability of k_y and T_s for deterministic and performance-based seismic displacement studies.

A probabilistic cone penetration test (CPT) based liquefaction triggering procedure for granular soil is developed utilizing adaptive kernel density estimation (KDE). KDE with a fixed bandwidth has been applied for the computation of conditional probabilities for liquefied and non-liquefied datasets in prior studies; however, liquefaction data inherently have a combination of different distributions, so the use of a fixed bandwidth is a suboptimal solution. In this study, we presented a mathematical framework for the calculation of adaptive bandwidth through an iteration process. We validated the proposed adaptive KDE by comparing the result of conditional probability with the true density function for one-dimensional and two-dimensional problems. Then, the proposed adaptive KDE was applied for two-dimensional probabilistic liquefaction triggering using Bayes theory. The variables of tip resistance and cyclic stress ratio were considered as main predictors for two-dimensional classification. The proposed method’s performance was evaluated using receiver operating characteristics (ROC) curves and the area under the curve (AUC) of the ROC. Training and testing data are selected randomly by a ratio of 80% and 20%. Three iterations were found as the best value satisfying the generality of conditional probability for liquefied and nonliquefied data and the performance of the Bayes classifier. An optimum classifier for this CPT database was found to be a threshold of 0.54 for the liquefaction probability. The results indicate that this estimator can effectively predict the liquefaction potential of CPT data, with an AUC above 0.88. The conclusion reached was that the variability in the probability of liquefaction calculated using the proposed method offers a better description of probabilities than the previous methods.

In practice, a unidirectional horizontal ground motion is often selected as input during the design of geotechnical systems. This recording is obtained either as the component with the greatest intensity [e.g., in terms of a primary intensity measure, IM, like peak ground acceleration (PGA)] or as the maximum rotated component (RotD100, again in terms of an IM like PGA). Although seismic ground deformations are generally assumed to be governed by the direction of maximum shaking intensity under unidirectional shaking (1D), prior experimental research has shown that bidirectional horizontal shaking (BD) can increase seismic settlements in dry sand or the buildup of excess pore water pressures in saturated granular soils. In this paper, we explore the influence and relative importance of bidirectional horizontal shaking numerically (as compared to maximum rotated 1D shaking) on the seismic response of shallow-founded structures on liquefiable soils. A suite of 3D, fully coupled, nonlinear finite-element analyses, previously validated with centrifuge recordings, are employed to evaluate soil-structure interaction (SSI) and its performance under bidirectional seismic loading. In general, bidirectional shaking is shown to amplify the foundation’s permanent settlement and permanent rotation by up to 10%−50% and 5.2−6.8 times greater than that under unidirectional shaking, respectively, due to its greater net seismic energy content compared to the models subject to unidirectional shaking. The limited numerical sensitivity study showed that evolutionary IMs correlated better with permanent foundation settlements, while the peak transient IMs could provide a better correlation with residual foundation rotations. Although much experimental and numerical research is needed in this area, the limited results presented here point to the importance of considering bidirectional shaking (as opposed to unidirectional maximum rotated component) when evaluating the key engineering demand parameters that quantify building performance on liquefiable soils.

Seismic soil-structure interaction (SSI), stratigraphic variability, and layering influence liquefaction triggering, the resulting total surface deformations, and damage to buildings and infrastructure. The existing empirical procedures for evaluating liquefaction triggering are primarily based on case history observations of surface manifestation and treat susceptible granular deposits as uniform and isolated. Meanwhile, most natural granular deposits are spatially variable due to heterogeneities in soil hydraulic conductivity, layer thickness, relative density, and continuity. In this paper, three-dimensional (3D), fully coupled, nonlinear finite-element analyses (FEA) in OpenSees, validated with centrifuge experimental results, are used to systematically evaluate the influence of layering and stratigraphic variations on the system’s performance. We evaluate the response of two dissimilar, multi-degree-of-freedom (MDOF), shallow-founded structures. The ejecta potential index (EPI) is used to quantify the potential for formation of soil ejecta in different configurations. EPI is shown to depend strongly on the location of the groundwater table, average thickness and continuity of the liquefiable layer, and properties of and proximity to the structure. The mechanisms of deformation captured by a continuum FEA (volumetric and deviatoric) as well as the extent of softening (quantified with r_u) within the critical layer are shown as uncorrelated with EPI, which depends primarily on the nature of hydraulic gradients developed within the profile. The results point to the importance of considering stratigraphic variability and potential variations in groundwater table together with average soil properties and structural characteristics when evaluating the ejecta potential on liquefiable sites.

We performed 2D dynamic finite-difference analyses, to understand the effects of gravelly soil liquefaction on the performance of CentrePort, under the Kaikōura, New Zealand, 2016 M_w7.8 earthquake, and compared the results to field observations. In this study, we focused on the development of appropriate seismic loading input used in the analysis. Ground acceleration time history recordings are available from eight strong motion stations (SMS) nearby. We selected the recording from station POTS as the “rock outcrop” motion, and the PIPS and CPLB recording as the “target” motions that we desire to match. The selections were made based on soil stratigraphy, and shear wave velocity (Vs) profiles at the site of CentrePort, and near the recording stations. To verify that the selection was appropriate, we then performed 1D equivalent linear site response analysis. In the site response analysis, we considered the mean Vs profile across the site, as well as the ±σ Vs profiles. The 5%-damped spectral accelerations at the top of the 1D soil column were compared to that of the PIPS and CPLB recording. Additionally, we applied frequency filtering to the input motion to reduce the computational cost of the model.

This study uses probabilistic seismic and tsunami hazard analyses to develop a joint seismic-tsunami hazard model. For a particular probability of exceedance, the joint model produces significantly lower seismic forces and tsunami wave heights than the independent models. The consequences of the lowered seismic and tsunami loads are demonstrated for a site in the Puget Sound region of Washington State. While the structure must still be designed to resist the independent seismic and tsunami loads, the demands from the coupled seismic-tsunami loading are greatly reduced.

The manifestation of ground shaking in sedimentary basins during an earthquake event depends on the energy released by the seismic source, the distance between the source and the basin in question, and the geologic characteristics of the basin. The combination of these components leads to amplification of ground shaking in basins relative to non-basin regions. Within sedimentary basins, spatial variability of ground shaking from location to location occurs due to the complexities associated with the interactions of seismic waves with the 3-dimensional characteristics of the subsurface and the variation of geologic material. This includes refraction which alters the propagation direction of seismic waves, diffraction which spreads and scatters the waves, reflection which can concentrate seismic energy, and their combinations which can generate propagating surface waves. The intensity of these basin-related site effects is drastically impacted by the path between the source and the site within basin (attenuation and basin boundary interactions). Both site effects and path effects are intertwined, and as such, the determination of site response in these geomorphic provinces requires proper understanding of their interactions in order to separate both effects. Using an expanded southern California ground motion dataset that comprises a subset of NGA-West2 plus recent event recordings, this study uses iterative mixed effects modelling scheme to propose a site-dependent path model for southern California. The site-dependent model attempts to partition path-site effects, and the regional model aims to release the ergodic assumption. It is expected that incorporating site dependence based on basin and non-basin features will show reduction in uncertainty in comparison to current in practice ergodic GMMs.

Recent studies found a significant underprediction in ground motion intensity measures for finite-fault simulations of moderate magnitude events in southern California relative to established ground motion models. This study aims to understand the source(s) of this bias by evaluating ground motion residuals. For this, simulations have been performed for a total of 27 well-recorded earthquakes in southern California. Systematic efforts have been employed to identify the source(s) of bias by ruling out factors that are insignificant. Preliminary findings indicate that the magnitude-area scaling used in the simulations is the likely major cause of the observed bias. Adjustment in the source attributes on event-by-event basis is underway to study if the observed bias can be reconciled.

Current design codes for the dynamic design of retaining walls have been criticized for being both over-conservative and under-conservative. However, much of the uncertainty in these cases comes from the dynamic earth pressure coefficients assumed. Recent research has suggested that the limiting dynamic horizontal effective stresses can be more straightforwardly predicted using static earth pressure coefficients once it is recognized that, in some cases, horizontal shaking can induce significant dynamic vertical effective stresses. In this research, results from a dynamic centrifuge test, conducted using the University of Colorado Boulder’s 400 g ton centrifuge, are used to demonstrate the occurrence of soil rocking and to inform finite element modeling of the problem. Dynamic analyses are conducted to investigate the rocking soil response, and the results are validated by comparing the system mechanics and the cyclic shear stress-strain loops mobilized. In this study, particular attention is paid to the numerical modeling of the boundary conditions with a discussion of rigid versus absorbing boundary conditions used to idealize the centrifuge test’s absorbing duct seal boundaries. Overall, the results evidence the occurrence of soil rocking under horizontal shaking and motivate a move away from traditionally used dynamic earth pressure coefficients.

The occurrence of earthquake surface fault rupture poses a significant hazard to the built environment in near-fault regions. Despite the prevalence of heterogeneous soils, current models of this hazard mostly treat soil to be a homogeneous medium. This research investigates the influence of soil heterogeneity on earthquake surface fault rupture using the explicit finite difference method (FDM). The study aims to bridge the gap in modeling the influence of soil heterogeneity on earthquake surface fault rupture by comparing the results of finite difference models with those obtained from virtual experiments using the discrete element method (DEM). Continuum numerical models using the FDM in the FLAC2D software are implemented based on a previous study that utilized the DEM to simulate fault rupture propagation through layered soils without direct input of common constitutive properties. The finite difference models extend the use of the linear elastic perfectly plastic Mohr Coulomb model and the PM4Sand constitutive model to account for contrasts in soil properties and how they influence fault rupture propagation. Results show that, overall, PM4Sand models performed better than the MC models when compared to the DEM output results. In reverse faulting, the pattern of broadening within loose layers and re-localization within dense layers is observed with both constitutive models independently if the layer is overlaid by either a dense or loose layer. Similarly, simulations of normal faulting in layered soils revealed similar trends in the direction of fault rupture propagation. However, deviations from the DEM results were greater with the MC models. This study highlights the importance of implementing remeshing and a more rigorous calibration of parameters used in the PM4Sand constitutive model. Finally, this study assesses the capability of traditional continuum methods to capture complex soil behavior during normal and reverse faulting in heterogeneous materials.

In this work, an integrated framework is proposed for the probabilistic evaluation and multiscale mapping of liquefaction-induced settlements exceedance rate considering both the spatial variation of soil parameters and uncertain ground motions. The framework consists of three key components: empirical CPT-based models to evaluate the probability of liquefaction and liquefaction-induced settlement, a probabilistic method to estimate settlement exceedance rate in a given exposure time considering all possible ground motions at all hazard levels through a joint probability distribution of peak horizontal ground surface acceleration and moment magnitude of earthquake, and a multiscale random field model to map settlement exceedance over the study region considering the spatial variations of soil parameters and the influence of surficial geology. The framework is applied to assess liquefaction-induced settlement exceedance rate in an earthquake-prone region, resulting in consistent results with existing analysis and knowledge of the earthquake hazard in the study region.

Coastal erosion and sea level rise have become common issues along the coast of Southern California not only from an environmental standpoint but also from a geotechnical standpoint. This case study presents reactivation and partial movement of an ancient landslide along the Orange County coastline due to the significant loss of sand buttressing the landslide at the beach. The landslide reactivation resulted in tension cracks that extended through a community parking lot and several residential lots above the beach. A forensic geotechnical engineering investigation was performed to characterize the subsurface soils and groundwater conditions and to monitor the landslide movements using inclinometers, piezometers, and crack monitors. This study indicated that a portion of the neighborhood was constructed over an ancient landslide which, until recently, was essentially buttressed by beach sand deposited along the toe of the landslide. Over the last several decades, the beach sand slowly eroded until the beach was almost completely gone following a high tide event in July of 2020. The removal of beach sand that buttressed the toe of the ancient landslide led to the reduction of the slope stability safety factor to less than 1.0 triggering reactivation of a portion of the landslide. The reactivation resulted in damage to the parking lot area, underground utilities, one empty residential lot, and four homes at the head scarp of the reactivated portion of the landslide as well as compromising and deforming the railroad track near the landslide toe. The beach sand depletion was confirmed through our geologic modeling and slope analyses as the triggering method for the reactivation. Temporary stabilization measures were put into place consisting of adding approximately 17,400 tons of rip-rap along the west side of the railroad that served to add weight at the toe of the active portion of landslide. The temporary stabilization measures served to temporarily halt the movement, however, high tide events triggered by Hurricane Kay resulted in additional beach sand loss and landslide movement. Several more rounds of rip-rap were added while permanent stabilization measures were being developed to satisfy the multiple stakeholders. As of July 2023, permanent stabilization measures have been completed. This case study of coastal erosion induced landsliding in southern Orange County highlights both the need for sustainable designs and future mitigation measures as well as the geotechnical challenges as the coastline erodes due to sea level rise, urban sprawl, state mandated water quality measures reducing sediment transport to the ocean, and other manmade improvements that otherwise change/impede sand deposition along the coast.

The susceptibility of cohesionless soil to erosion has been a significant factor contributing to the failure of geotechnical infrastructure. This study aims to investigate the erosion resistance of zein biopolymer-treated sands. Cohesionless sand is used, and its index properties are determined. Treated specimens are prepared by mixing dry sands with 1% biopolymer content and compacted in transparent molds. Comparative analyses are conducted between the treated and untreated specimens using a hole erosion test, considering two hydraulic gradients. The results show that the erosion resistance of treated specimens significantly improves by up to 97% to 99% compared to the untreated specimens. The hydraulic shear stress and erosion rate decrease with the curing period, while erosion mass flux decreases with increasing hydraulic gradients. Curing periods and hydraulic gradients are significant factors influencing internal erosion. The findings demonstrate the potential of zein biopolymer as a novel method to enhance erosion resistance, suggesting its application in soil erosion control.

Local scour occurs around pile foundations supporting bridges and marine structures due to currents and waves, which can severely undermine the performance of piles in extreme weather events such as floods and hurricanes. A scour hole is often developed around the pile foundation by local scour. In general design practice for pile foundations, scour-hole dimensions are either completely ignored or simply considered but with different methods. This paper reviews the current methods available for the evaluation of the effects of scour-hole dimensions on pile axial and lateral capacities. These methods include the methods outlined in the US Federal Highway Administration Driven Piles and Drilled Shafts as well as the American Petroleum Institute. A case regarding piles in dense sands subjected to different scour-hole conditions was analyzed using these methods. The analyzed results were compared to the results from the three-dimensional continuum finite element analysis and analytical solutions. Based on the comparisons, the pros and cons of each method were discussed. Recommendations on selecting a proper method for the design were also given.

Sediment erodibility in coastal environments is expected to be influenced by geotechnical properties. However, most common coastal geomorphological models do not consider geotechnical parameters measurable in the nearshore and intertidal zone or their variability. In this study, geotechnical properties, hydrodynamics, and geomorphological change were measured at a sandy beach to explore the implementation of geotechnical parameters into modern sediment transport and coastal geomorphodynamic models. The field data collection included wave and water-level information and high-resolution topographic and bathymetric mapping alongside geotechnical testing at the sandy Atlantic side beach at the USACE Field Research Facility in Duck, North Carolina. The proposed survey strategy yielded co-located information on geotechnical properties, hydrodynamics, and geomorphological change despite challenging environmental conditions. For example, surficial sediment strength in the intertidal zone varied with tidal fluctuation. Implementation of observed onshore sediment transport will be explored and considered for the proposed coupled model.

Surface erosion of soil is a process of transporting soil grains by flowing fluids. It has been recognized as one of the major risks associated with infrastructure built in rivers, estuaries, and the coast, such as bridges, quays, and levees. Removing soils during the erosion process reduces soil support to the structures and may eventually lead to structural collapse. In this study, surface erosion of clayey soil was investigated using a purpose-built rotating surface erosion apparatus (RSEA). It specifically focuses on the effects of saturation and soil slaking on the erodibility of the clayey soil. The results show that increase of soil saturation decreased the erosion rate of the soil at the same hydraulic condition but did not change the erodibility category. Moreover, it was also found that the time-dependent disintegration/slaking process of unsaturated soil was critical to erodibility of unsaturated soil.

This study investigates the recession of sandy coastal bluffs under random waves and changing water levels. A laboratory flume experiment was conducted in the wave flume at Stony Brook University using a sandy beach-bluff model subjected to waves and fluctuating surges. A laser-camera system monitored bluff profile evolution. Results showed rapid toe erosion and undercutting leading to major slope failures. Repeated wave impacts generated pore pressures, while toe erosion increased shear stresses, causing episodic collapses. Elevated pore pressures and lowered matric suction from wave run-up, and rising surges reduced stability. However, progressive toe erosion by waves was the most critical factor. The laser-camera technique effectively captured profile changes, revealing dynamics linking pore pressure fluctuations and bluff erosion from intermittent wave impacts.

Triaxial permeameter testing is a useful method for studying the mechanical behaviour of internally eroded specimens and involves four stages: reconstitution, consolidation, seepage, and axial compression. Under downward seepage, flow is introduced to the top of the specimen, erodes it, and leaves the specimen carrying eroded particles through the featured base pedestal designed to accommodate unimpeded outward movement of eroded particles. Careful collection and precise measurement of any mass loss is crucial for accurate void ratio estimation and characterization of erosion response. An internally unstable specimen reconstituted against featured boundaries experiences mass loss not only within but also out of the seepage window. This article reviews current mass loss measurement practices during the seepage stage, identifies challenges and the corresponding need for mass loss measurement throughout a triaxial permeameter test, and proposes a comprehensive method for measuring mass loss from the start of reconstitution to the end of axial compression.

With climate change causing sea level rise globally, as a low-lying island city, Singapore is particularly susceptible to the threat of the sea level rise. The 30% of coastline in Singapore comprises natural areas such as sandy beaches, rocky shorelines, and mangroves; they are vulnerable to the intensifying high tides and large waves. Beach erosion has become an urgent issue for the city to mitigate the overwash effect and stabilize the sand. Conventional measures to prevent coastal erosion include building seawalls or breakwaters, beach nourishment, geotextile wall installation, and planting vegetation. In this study, a new product, eco-cement, which is based on the enzymatic induced carbonate precipitation (EICP), was developed to stabilize the sand slope. Laboratory sand column tests have shown compressive stress strengthening and permeability reduction. A field-scale trial was carried out using the combined spray and injection method to solidify the beach sand. The calcium carbonate crystals effectively bond sand particles and furthermore forming a crust at the surface of sand slope to mitigate the erosion caused by waves. Challenges for the scale-up of EICP from laboratory technique to field application are addressed. Sequential injection and spray strategy is encouraged to achieve the uniformity of the calcium carbonate precipitation within the sand. Sand properties including the compressive strength and microscopic structures were examined to assess the improvement. A subsequent long-term monitoring of the treated sand slope has also shown the effectiveness of the EICP treatment and the increase of erosion resistance.

Soil erosion is critical in assessing bridge pier scours. To minimize the uncertainty in soil erosion analysis, the Federal Highway Administration (FHWA) introduced the portable scour test device (PSTD) to measure soil resistance by in situ testing in the field. The PSTD is a new erosion testing device that has a lot of similarities with the in situ scour testing device (ISTD) in mechanism and data acquisition. The fluid condition in PSTD is radial, and the recorded data in PSTD include flow rate, depth of eroding soil sample, and the eroding time. Shear stress induced by the fluid is an important parameter, which plays a load role in the soil erosion process. PSTD in its current setup lacks a sensor to measure shear stress at the soil-water interface. A computational fluid dynamics (CFD) method is used to simulate the shear stress imposing on the soil sample in a PSTD test. Also, a set of six controlled erosion function apparatus (EFA) and PSTD lab tests have been performed to compare the shear stress obtained from these two tests. The comparison allows for identifying a correlation of shear stress obtained from EFA and PSTD.

A new method for shoreline protection was developed by “seeding” oyster reefs with structures built from recycled oyster shell and Portland cement. These pervious oyster shell habitat (POSH) units attract young oysters more quickly than traditional concrete shoreline protection structures. From 2021 to 2023, several POSH units were placed in the mid-intertidal zone along the shoreline of the Fort George River within the Timucuan Ecological and Historic Preserve (Duval County, FL). Preliminary findings which showed stress reduction along the shorelines and erosion mitigation were presented at Geo-Congress 2023. This paper highlights further evaluation of the effectiveness of these units at reducing bed stress and mitigating erosion using a combination of field observations, wave measurements, aerial imagery, and computational fluid dynamics.

Erosion of surficial soils, whether topsoil or fill, is a significant problem. Geotechnical aspects of soil erosion from wind and water have been mitigated with a variety of covers and treatments over the last 100 years. While some methods have shown to be more successful than others, significant limitations to widespread application are trucking costs for the massive volumes of material needed to treat large areas of erosion susceptible soils in the time before vegetation can take hold and serve as long-term erosion mitigation. A particularly attractive, low-cost, and readily available material in wooded areas with active logging are the materials in the pits and piles at sawmills and log mills. While the bulk of the sawdust is captured for economic benefit, the residuals are often pushed into pits and piles where they slowly compost. The residuals contain soil, rock, bark, leaves, needles, gravels, sawdust, and other minor organic wastes from the mill operations. To validate the use of these residuals for erosion mitigation, a study of both wind and water erodibility of these residuals was performed using wind tunnel, rainfall simulator, and laminar flume. Their compatibility with revegetation was also experimentally studied by growth of a clover cover crop. Experimental findings show that log mill residuals tested herein outperformed saw dust, sand, wood chips, compost, and several other conventional erosion mitigations covers in all experiments, including revegetation.

A variety of laboratory devices are available to measure the erosion resistance of soils, each with its own advantages, limitations, and applicability. Two of those devices—the erosion function apparatus (EFA) and the ex situ scour testing device (ESTD)—are very similar in design and concept; however, there are notable differences in geometry and test procedures that can affect the results. As the Federal Highway Administration continues to perform both EFA and ESTD tests as part of its NextScour research efforts, it was critical to evaluate the inherent differences between these devices and more directly compare the resulting erosion rates and hydraulic shear stresses. As part of the initial work, three different engineered soils were prepared and tested in the EFA and ESTD using their respective procedures. Hydraulic shear stresses were then computed based on surface roughness of the specimens and the Moody chart. The preliminary findings indicate that the EFA and ESTD generally yielded comparable shear stresses for all soils. After application of best-fit power functions through the data, the resulting shear stress factors between the EFA and the ESTD were near unity, ranging from 0.92 to 1.13; however, there were larger differences in critical shear stresses—particularly in soils with higher sand content. Additional work is needed on a wider range of soils, but in the interpretation of erosion resistance from laboratory testing, it may be important to understand the device, the flow conditions, and the test methods involved.

Regional slope stability analyses can provide a system-level assessment of landslide susceptibility. This study aims to develop a regional back-analysis model for rainfall-induced landslides to compute ground shear strength that can be used for landslide prediction. Most commonly, mechanistic-based models for regional slope stability consist of simplified one-dimensional (1D) analyses compared to more realistic three-dimensional (3D) procedures. A pseudo-3D methodology is applied on 788 landslides over two 2.5 km² areas in the plutonic rocks of the Utuado Batholith. First, an infinite slope stability triggering model is applied on a 1 m-resolution digital elevation model (DEM) to identify the triggering grid cells. A spatial 3D projection procedure is then implemented to generate 3D landslides with defined location, area, and volume. Two inversion procedures are considered herein: inversion against landslide area density and inversion against individual landslides. Unlike inversion against landslide area density, inversion against individual landslides generated good match in landslides’ locations and sizes and resulted in lower scatter in regional strength estimates. The average back-calculated cohesion and friction angle were c′ = 1 kPa, ϕ′ = 57° and c′ = 2 kPa, ϕ′= 56° for the first and second study areas, respectively. Inversion against landslides’ volumes in addition to their areas and centroid locations reduced the uncertainty in the triggering depth and modeled shallower landslides, which better matched the mapped landslides.

Landslide susceptibility mapping (LSM) can provide valuable information for landslide characterization and mitigation. However, there are long-standing problems with LSM that have remained unaddressed or inadequately resolved, such as a lack of an effective framework to integrate the physical and statistical knowledge about landslide occurrence. To address the knowledge gap, this paper proposed to combine the physical model and machine learning techniques to produce a robust landslide hazard assessment. The hypothesis is that the physical modeling result itself can be a valuable model input to be incorporated in the training model of a machine learning framework. In this research, the tree augmented naïve (TAN) Bayes classifier has been selected as the machine learning model. In addition, we used PISA-m, a probabilistic landslide slope stability program, to estimate the probability of landslide occurrence in Magoffin County, Kentucky, United States. Results of physically assessed landslide susceptibility were used to be combined with other geomorphological variables in the TAN model to predict the landslide probability in the study area. We performed cross-validation to evaluate the model performance and reliability of the proposed methodology.

The occurrence or reactivation and acceleration of landslides can occur unannounced and can result in significant impacts to life, property, or the environment. The processes of slope deformation and progressive failure are more active than many realize; rapid slope failures are often preceded by years of erosion, deformation, and smaller failures. In the last 10 years, the use of lidar-derived elevation models has supported the identification of landslides across large regions and is increasing the ability of geoprofessionals to identify precursory signs of failures. During the same time period, advanced computational techniques to numerically compare multiple bare-earth lidar point cloud datasets, known as lidar change detection (LCD), coupled with the development of automated workflows, have resulted in the ability to conduct LCD rapidly across large areas. This paper demonstrates how regional LCD can provide a more complete understanding of landslide hazards and better management of risk. The paper also presents preliminary tests of applying image segmentation techniques to support LCD analysis.

Landslides along Alabama highways are a relatively common occurrence in many regions of the state. These landslides can lead to damage to transportation infrastructure and significant traffic disruptions. The current practice identifies landslide locations primarily through maintenance personnel reports or motorist complaints. Once an unstable region is identified, the suspected slide area is commonly instrumented with inclinometers, which are then read at regular intervals to understand the slide plane location and identify changes in behavior. This inclinometer data has been collected at unstable sites across the state for many years and provides a unique dataset to understand how precipitation events influence landslide behavior along highways. Previously developed precipitation thresholds considering storm magnitude and duration were consistent with landslide events observed around the state, but there are many non-triggering events that fall above the thresholds (false positives). Approximately 70% of false positive storm events occurred during drier than average periods based on normalized soil moisture data from NASA’s SMAP instrument, while large movements occurred primarily during periods of average or above-average soil moisture. This suggests that adding soil moisture data to landslide threshold predictions may help to reduce false positive events and to assess the likelihood of large movements occurring. These findings are now being used to develop improved warning thresholds that can highlight when landslides are likely to occur, allowing inspections and preventative maintenance to be prioritized.

Landslide initiation, movement, and arrest are controlled by coupled hydro-mechanical processes. In this paper, a modeling framework solving the coupling between excess pore pressure dissipation and the landslide sliding dynamics is discussed. The model focuses on the basal shear zone, where inelastic deformation and displacement concentrate. The framework simulates the entire life cycle of a landslide, from triggering to runout, and enables a versatile incorporation of multiple inelastic constitutive laws. With these features, the framework can be used to capture different trends of landslide motion, from episodic events with velocity lower than 1 m/year to highly mobile runaway failures faster than 10 m/s. Here the framework is tested with perfect plastic frictional behavior. It is shown that closed form analytical solutions can be recovered. Notably, it can be shown that at steady state, a creeping landslide moving under the effect of sustained hydrologic forcing can be depicted as an equivalent damper with a viscosity dictated by the hydro-mechanical couplings in the shear zone. Specifically, our analyses show that triggering and propagation are dominated by a small number of characteristic timescales, including those controlling the time of consolidation, shear wave propagation, and viscous soil response. In the presence of dilation, negative excess pore pressure regulates the landslide mobility resulting in stable seasonal creep. By contrast, vanishing dilation (i.e., critical state) leads to sharp acceleration and large runout. In addition, for liquefiable soils (negative dilation), we show that small shear pulses can lead to self-feeding excess pore pressure buildup if the load is imposed faster than a critical rate. The satisfactory performance displayed by the model in simulating several case studies corroborates its versatility to support the interpretation of slope movement patterns and the assessment and mitigation of landslide hazards.

Landslides are one of the most catastrophic natural disasters. These calamities that are often caused by heavy rainfall, rapid snowmelt, and human activities may cause significant damage to people and property in the affected regions. The risk of landslides can be eliminated by investigating the probable cause of failure in the specific slopes and then mitigating them with an appropriate stabilization technique. Even though the available methods of mitigating landslides are highly effective, they may need to be more sustainable in nature. In recent years, microbially induced calcite precipitation (MICP) has proved to be a sustainable measure for improving the stability of slopes and preventing landslides. However, the efficacy of this method, considering various circumstances, such as soil type, slope geometry, the effective area of cementation, the effect of long-term exposure to climatic conditions, is a matter of debate among various researchers. In the present study, the potential of MICP to stabilize a homogeneous slope has been investigated numerically. Various parametric studies depending on the slope geometry and the effective areas of cementation were carried out to assess the efficacy of MICP in mitigating landslides in the chosen homogeneous slope. Preliminary analysis results indicate that MICP can effectively reduce landslides even with significant variations in soil type and slope geometry. However, certain constraints must be appropriately identified and addressed while designing such slopes. Based on these extensive numerical investigations, design charts can also be provided to determine the suitable range of parameters for slope geometry and effective area of cementation for designing an adequate bio-cemented slope in mitigating landslides.

Intense urbanization is a phenomenon present in several Brazilian cities. If done in an uncontrolled and inadequately studied manner, it can cause significant negative impacts, among them landslides, which are felt more intensely by populations located in high-risk areas. To avoid or mitigate these impacts, environmental geotechnics can contribute by providing the necessary tools to assess the susceptibility of a certain region to landslide. In this sense, the objective of this study was to evaluate the possibility of landslide in the metropolitan region of Natal, Rio Grande do Norte, Brazil, by calculating the factor of safety (FS) using the QGis software. To analyze susceptibility, according to NBR (Brazilian Norm) 11.682, it was considered that regions with an FS less than 1.5 can be considered risky, with values of 1.30 and 1.15 suitable for regions with medium and low degrees of necessary safety. For this, an assessment of the acting and resisting forces was made, requiring the use of another study already conducted in the region that provided the soil parameters used in the calculations. Additionally, two methods were considered for calculating the thickness of the soil—the S and Z methods, which differ in the parameters used for this purpose. At the end of the study, it was estimated that this region has few points of concern. This may be due to the type of soil predominant in the area and the fact that the city is mostly flat. Furthermore, it was confirmed that most of the regions with a lower factor of safety are located under environmental protection, and therefore, construction is not allowed in their surroundings. However, some exceptions were observed, including a specific location with a factor of safety value of 1.02. Although this location is in an environmental protection zone, its landslide can present risks since it is located near an inhabited area.

A vulnerability index can be defined as a quantifiable measure of conditions pertaining to some type of hazard. In areas with karst landscapes (i.e., geologic conditions leading to the dissolution of bedrock and subsequent sinkhole formation), engineers and researchers have developed several point-based indices to be used when assessing the vulnerability, a project site has to sinkhole formation based on the encountered subsurface conditions. In the state of Florida, engineers have historically used an index based on the subsurface layer thicknesses, called the raveling index (RI). In recent years, researchers have introduced more comprehensive point-based indices, the sinkhole resistance ratio (SRR) and the vulnerability geometric and raveling empirical indexing (VI_G + VI_R), incorporating encountered soil strengths and other empirically based data fitting techniques. This study investigates the effectiveness of these three indices against a database of sinkhole sites throughout Florida—most of which forming following either a solution type or cover-collapse mechanism. Using a simplistic probabilistic approach coupled with categorical analysis based on the characteristics and hydrogeologic conditions of each site, it was determined that all proposed indices are feasible in identifying relative sinkhole conditions in cover-collapse type sinkholes only, and may potentially not be effective for solution type. Furthermore, a “most effective” index was determined for cover collapse sinkholes, as well as recommended thresholds of each index to be used in future investigations.

The Trans-Canada Highway passes through very steep terrain in the Kicking Horse Canyon east of Golden, BC, and a series of recent projects have improved and widened the highway through the region. Construction of the final and most technically challenging segment is now underway with the Kicking Horse Canyon Phase 4 design build project. The existing highway crosses a series of unstable slopes, active landslides, large ravines, and avalanche and rockfall paths. Key project goals were to improve the safety of the roadway and reduce geohazard risk. The required highway geometry combined with upslope geohazards and steep terrain required significant portion of the alignment to be constructed on the steep slopes below the existing highway which have marginal stability. The conventional solution for construction on steep slopes below the highway has been to support the highway on grade with downslope retaining walls, which are stabilized by piles below. When considering this option following completion of the geotechnical investigation for detailed design, it became apparent that due to a number of factors, including higher walls and deeper bedrock than expected, large diameter piles at very tight spacing would be required to meet project specifications for slope stability. These piles would be costly, time consuming to install, and there would be significant safety challenges associated with the heavy piling equipment required on the steep slopes for long durations. A bridge solution was therefore proposed to carry the roadway on structure over the unstable slopes. An innovative viaduct design was developed and was adopted for nine individual viaduct structures totaling over 1.8 km of highway length. The viaducts have regular 23 m spans with substructures consisting of precast concrete cap beams at each pier supported on three concrete-filled steel pipe piles drilled into bedrock. The highway is supported on the structures, and the piers were designed to resist the loading from slope movements, thus avoiding the need to stabilize the entire slope. There are no established design methodologies in geotechnical practice for design of piles embedded in a moving embankment, other than in seismic design for liquefiable soils. New methodologies were developed drawing on first principles and existing stabilization pile methodologies. Close coordination was required between the structural and geotechnical engineers to find solutions for a variety of different loading situations, ground slopes and below-ground bedrock surfaces, and an active landslide zone that was actively moving during construction. Other extreme loadings were also required to be defined and designed for including debris flow, rockfall, and avalanche impacts. This paper discusses the many design, loading, and constructability challenges faced in the foundation designs.

The need to identify vulnerable sections of roadways has increased in central coastal North Carolina (NC) due to rising groundwater table levels and nuisance flooding resulting from sea level rise (SLR). These events, in turn, adversely affect surface transportation’s social, ecological, and technical dimensions. Therefore, this study aims to identify vulnerable roadway subgrades sections in Beaufort County, NC, using the most recent groundwater levels. Our study focuses on US and NC routes as they serve as potential evacuation routes in the event of flooding. Based on relevant spatiotemporal scales of the roadways, a geodatabase was built using the Geographic Information System software ArcGIS Pro 2.9.5. Different geoprocessing and geostatistical tools were utilized in the spatial analysis of roadways, and the extent of the vulnerable road sections was determined based on the criterion for potential loss of subgrade soil stiffness susceptibility. Preliminary results show that 25% of the roadways are currently vulnerable. These findings are essential in improving predictions of vulnerable roadway sections since, currently, nuisance flooding happens 5−8 days annually in Beaufort and is likely to happen 70−100 days annually by 2050, as per NOAA’s SLR predictions.

Transportation geotechnical assets generally include walls, slopes, embankments, and subgrades within the right of way. This paper describes how we developed an inspection sheet for mechanically stabilized earth (MSE) walls and the condition of the assets, to be incorporated in a geotechnical asset management (GAM) plan. The inspection sheet was based on existing GAM programs and optimized to meet the Kansas Department of Transportation (KDOT) monitoring goals. This included 14 inspectable items, including a measurement of the backfill using electrical resistivity. Laboratory electrical resistivity measurements were obtained in previous research and an in situ electrical resistivity measurement was developed for inspection purposes, which is described herein. KDOT selected 18 walls that were surveyed using the new inspection sheet and in situ electrical resistivity method. The inspection tool used an overall rating on a four to one scale, where four was “good” and one was “severe,” based on a weighted average of the 14 item ratings. The weighting system was developed from the opinions of 30 experts from various industries related to MSE walls across North America. The final rating also accounted for safety/mobility risks. Using the final risk-adjusted score, four walls were considered very good, eight were good, three were satisfactory, and three were fair. When fully developed, access to data about MSE conditions via this rating system and photographs will be easily retrievable through a common, computer-based system. The life cycle of an asset or assets can be tracked individually or as a part of a class that could be based on asset type, construction method, contractor, material supplier, or any other criteria. This information can be used to evaluate the relative benefits of a wide range of engineering options. Furthermore, by implementing this system now, KDOT can begin to track how emphasizing the inspectable elements with the weighting system relates to the long-term behavior of an MSE wall. It will be valuable to reevaluate the weighting system in 10−15 years to note which elements were actually indicative of an issue with the wall. Such data are not currently available.

Rainfall-induced slope failure is a major problem for highways made of highly plastic clay in the southern United States. Alternative wet-dry cycles and seasonal moisture variation lead to recurring shrink-swell of soil. In Mississippi, sustained perched water conditions within highway slopes due to increased rainfall have exacerbated this problem. Real-time monitoring of soil moisture content and matric suction can aid highway authorities in detecting overall structural health and early slope failure. This study aims to develop a protocol for an early warning system for highway slope failures made of highly plastic clay based on field instrumentation data. A slope in Jackson, Mississippi, was instrumented with moisture sensors, water potential probes, and rain gauges. The data obtained from field instrumentation, including moisture content, matric suction, and rainfall, were analyzed to develop an early detection protocol. The analysis conducted based on the field-instrumentation data revealed the presence of a perched water zone, and a trend of slope movement associated with it was predicted. This finding was verified by the profiles through electrical resistivity imaging, where the lower resistivity meaning the existence of water within the soil profile clearly indicated the presence of the perched water zone. A slope movement trend was observed from the inclinometer data. The comprehensive analysis of the instrumentation data led to the development of a protocol that can aid highway authorities in detecting slope failure at an early stage using field instrumentations.

This paper addresses the risks associated with deep excavations in urban areas, particularly concerning the potential damage or collapse of nearby structures, networks, and roads due to horizontal movements caused by the excavation’s support system. The study focuses on a specific case in Bogotá, Colombia, involving a 10-m deep excavation in soft clay, which experienced basal heave failure and infrastructure deformation during construction. To assess the resilience of the support system, the paper introduces a methodology that employs fuzzy logic to define criteria like robustness, redundancy, rapidity, and resourcefulness. The resilience index is calculated using ordered weighted average (OWA) with the Orness parameter α, allowing for the modeling of different risk attitudes, optimistic or pessimistic. Results indicate that the support system was insufficiently robust to prevent basal heave failure, and the resilience index decreased after the failure event in various scenarios. This study highlights the importance of evaluating resilience as an intrinsic property of systems to enhance their performance and adaptability in urban excavation projects.

Estimation of short- and long-term settlement in compressible soils is complex and critical for building projects. Conventional prediction methods use in situ and laboratory geotechnical data obtained at selected locations during the site investigation. The reliability of designs that utilize selected design parameters is affected by the uncertainty associated with these parameters. Settlement monitoring during construction using the observational method can be used to reduce the uncertainty in settlement parameters. In this paper, the Bayesian method was used in association with laboratory data and settlement monitoring data to update the settlement parameters and predictions due to fill placement for construction of a data center project. Markov Chain Monte Carlo (MCMC) simulation and the Metropolis-Hastings algorithm were used to estimate updated geotechnical parameters for prediction of future settlement. The predictions were shown to converge to the field measurements, verifying closely the originally obtained investigation parameters, and greatly reducing uncertainty regarding future performance of the fill.

This study conducted probabilistic analyses of seismic slope stability considering the spatial variability and stratigraphy orientation of soil properties. The slope stability and consequence of slope failure were described using probability of failure and risk of failure, respectively. To reduce computational time, subset simulation was adopted. It is found that for seismic slope stability problems, the horizontal seismic coefficient has a significant effect on the probability of failure and risk of failure of the slope. The variability of soil properties, that is, the rotation angle and scale of fluctuation of the random field, has a large impact on the statistical outcomes. Critical scenarios were identified, where the main stratigraphy orientation is parallel or semi-parallel to the slope surface. The stratigraphy orientation is most influential when a small horizontal seismic coefficient is used. It is also noticed that the vertical seismic coefficient can have a moderate impact on probabilistic outcomes.

This paper presents an approach for assessing the risks associated with mechanically stabilized earth (MSE) walls commonly used in bridge abutments and highway projects as an alternative to traditional gravity walls. The stability and performance of MSE walls are influenced by different components, and any changes in these factors can considerably impact transportation and potentially place the wall at high risk. Risk assessment involves evaluating the significance and tolerability of estimated risks, considering the likelihood that the wall’s design will meet performance requirements and the severity of any expected shortfall. More than 25 factors are introduced to evaluate the risk rank of a wall during inspections. A semi-quantitative risk assessment based on 10 major influencing factors is described to demonstrate the application of the proposed method to assess the risks associated with MSE wall failure and evaluate the potential impacts and consequences.

With the emerging application of geotechnical asset management (GAM) and the increasing risks due to extreme events and the aging transportation infrastructure, resilience of geotechnical assets is a critical component that should be incorporated within GAM. In this paper, we introduce a quantitative risk-based approach to define and quantify resilience at individual geotechnical assets and the resilience of a network. The proposed general definition of resilience is the ability to anticipate and prepare for changing conditions and disruptive events to enable the asset or a system of assets to withstand and recover rapidly from disruptions (without failure) by restoring an acceptable level of service and condition in a specified time frame, which can be measured using observations and/or performance models. Following the discussion about the attributes encompassed in this definition, we introduce a holistic resilience assessment framework for geotechnical asset, focusing on its application within a GAM program.