Liquefaction Triggering Research Articles

Regional scale probabilistic procedure for estimating lateral spread displacements

Regional scale liquefaction assessments are currently performed using approaches such as qualitative liquefaction susceptibility rankings based on mapped geology and groundwater information, interpolation of liquefaction vulnerability indices from widely spaced subsurface explorations, or use of proxies for geologic, geotechnical, and groundwater conditions that affect liquefaction triggering calculations. These methods often do not include assessments of the consequences of liquefaction, such as the potential lateral spread displacement and its uncertainty. This study presents a procedure for probabilistically assessing liquefaction-induced lateral spread displacement at the regional scale by estimating a distribution of lateral displacement index (LDI) using models conditioned on surficial geology, depth to groundwater, peak ground acceleration, and earthquake magnitude. Existing topographic correlations are used to convert distributions of LDI to distributions of lateral spread displacement. Case histories illustrate its performance in regional assessments of the lateral spread hazard.

Roles of pre- and post-liquefaction stages in dynamic system response of liquefiable sand retained by a sheet-pile wall

This study examines the dynamic system response of a liquefiable deposit retained by a sheet-pile wall, with emphasis on the roles of pre- and post-liquefaction stages of soil response. A recently developed constitutive model, SANISAND-MSf, is utilized to simulate the pre- and post-liquefaction cyclic response of sands. The model is a stress-ratio controlled, critical state compatible, bounding surface plasticity model, which incorporates the concepts of memory surface and semifluidized state. The model’s performance is validated using a combination of cyclic simple shear tests and dynamic centrifuge tests from the LEAP-2020 project. A sensitivity analysis is then conducted by varying the base input motion intensity and duration. The results reveal that the amplitude of equivalent uniform base acceleration in pre-liquefaction correlates well with the timing of liquefaction triggering, and the cumulative absolute velocity of the base acceleration during the post-liquefaction stage correlates well with the post-liquefaction displacements. The study highlights the importance of accurately simulating response in the pre-liquefaction stage for the extent and timing of occurrence of liquefaction, which regulates the remaining intensity and duration of shaking, and in turn, affects the post-liquefaction permanent deformations at the system level.

On the In Situ Cyclic Resistance of Natural Sand and Silt Deposits

This study presents cyclic resistances of an instrumented medium dense sand (i.e., the Sand Array) and medium plastic silt (i.e., the Silt Array) deposit deduced from in situ dynamic testing using the controlled blasting test method. Particle velocity records were used to calculate the cyclic resistance ratios, CRRs, and convert the transient blast-induced ground motions into their equivalent number of shear stress cycles, Neq, through consideration of the cyclic resistance observed from stress-controlled, constant–volume, cyclic direct simple shear (DSS) tests. The CRR-Neq relationship developed for the medium dense sand deposit demonstrated that the in situ cyclic resistance is larger than that (1) expected from cyclic DSS test specimens reconstituted to the in situ vertical effective stress, relative density, and shear wave velocity, Vs; and (2) calculated using case history-based, penetration-, and Vs-based deterministic formulations of liquefaction triggering models. Differences between the in situ cyclic resistance and that computed using probabilistic liquefaction triggering models reduced somewhat when considering probabilities of liquefaction exceeding 50% and 85%, depending on the model. Partial drainage during dynamic loading of the Sand Array appears to have contributed to the cyclic resistance of the sand deposit, with an increase of 6% to 27% compared to that estimated for fully undrained conditions. Differences between the cyclic failure criteria used to interpret the cyclic resistance of intact laboratory specimens of silt result in significantly different interpretations of the in situ CRR; the use of maximum excess pore pressure-consistent criteria appears to provide the best representation of the in situ, stress-based cyclic resistance when high quality, intact silt specimens form the basis for conversion of transient seismic waveforms to uniform shear stress loading cycles. The investigation described herein suggests that the reduction of cyclic resistance for plastic soils to account for multidirectional shaking ranges from 0% to 7% over Neq of 1 to 100.

Geospatial data-driven assessment of earthquake-induced liquefaction impact mapping using classifier and cluster ensembles

A 5.4 ML earthquake occurred on November 15, 2017, in Pohang, South Korea. This earthquake was the second largest recorded earthquake in South Korea and had detrimental effects on the ground and infrastructure. Among all the ground deformations, hundreds of liquefaction-induced sand boils and ground failures observed near the epicenter were major issues. However, whether subsurface characteristics and liquefaction vulnerability indices trigger regional liquefaction manifestations and how local liquefaction occurs as a consequence remains elusive. In this study, we present a novel data-driven model for the analysis of site-specific liquefaction triggering that considers the spatial uncertainties of principal liquefaction vulnerability indices. This is achieved by establishing an advanced artificial intelligence technology that assembles optimization-oriented, supervised, and unsupervised machine-learning models. The phased decision-making process could develop unified liquefaction hazard zonation based on the clustering ensemble methodology and help identify feasible liquefaction impact mapping procedures via the optimized classification of their performance evaluation with liquefaction inventory. The alternative three-phase approach, depending on the feasibility of geo-data and geospatial modeling, consists of three zonation methods (macro-, micro-, and nano-zonation) based on a 3D grid network, which assigns the best-fitting machine-learning model. The resulting liquefaction impact map, which has a high resolution and is assigned nano-zonation-based clustered liquefaction indices, can assist in site-specific decision-making to zonate liquefaction-induced ground displacement.

Addressing complexities in MPM modeling of calibration chamber cone penetrometer tests in homogenous and highly interlayered soils

Cone penetrometer tests (CPTs) are used to characterize soil for a variety of geotechnical engineering applications, including earthquake-induced liquefaction triggering assessment. Numerical modeling of CPTs is frequently used to better understand soil behavior, soil-penetrometer interaction, and engineering estimates made from CPT data. However, calibrating and validating numerical CPT simulations with experimental calibration chamber (CC) data can be challenging. Specifically, uncertainties in the interpretation of laboratory strength and compression data compound with uncertainties in the CC testing and the assumptions made when developing the numerical model. This article provides a comprehensive review of uncertainties in the calibration and validation of CPT numerical simulations performed in homogenous sand, homogenous clay, and layered sand-clay soil profiles, comparing numerical results with well-documented experimental calibration chamber tests performed at Deltares. In particular, the Material Point Method (MPM) is used to perform the numerical analyses. A framework is presented to assess how uncertainty in the numerical model output is attributed to each input parameter. It is demonstrated that uncertainties can be explored numerically. Finally, recommendations for future experimental and numerical studies of CPTs are provided.

Liquefaction triggering of non-saturated sandy soils

In saturated sandy soils liquefaction triggering is generally well-identified according to stress or strain criteria. On the contrary, the attainment of liquefaction in non-saturated sandy soils is still a cause of discussion in the scientific community. Even if the liquefaction resistance of non-saturated soils is higher than that of saturated ones, these soils may liquefy, as well. The increasing interest for cyclically mechanical behaviour of non-saturated sandy soils is due to the fact that desaturation or induced partial saturation can be used as useful mitigation techniques against soil liquefaction. Therefore, it is important to define, as accurately as possible, the attainment of liquefaction, on which depends the estimation of liquefaction resistance. The relevance of the apparent viscosity as a physically based parameter for the correct identification of the liquefaction triggering for fully saturated soils has been already demonstrated. In this paper, the viscous triggering approach has been used for non-saturated soils, processing some cyclic triaxial tests carried out on different sandy soils. The results confirm the reliability of the apparent viscosity as a liquefaction triggering parameter, showing a tight correlation with the strain liquefaction triggering criterion. Therefore, strain criterion should be preferred in non-saturated sandy soils.

True Liquefaction Triggering Curve

Current simplified models for predicting liquefaction triggering and manifestation do not account for the mechanisms of liquefaction triggering and surface manifestation in a consistent and sufficient manner. Specifically, an artifact of the way simplified triggering curves have traditionally been developed is that they inherently include some factors that influence surface manifestations, particularly for medium-dense to dense soils. As a result, using the simplified triggering curves in conjunction with the manifestation models results in the double-counting, omission, or general obscuration of distinct factors that influence triggering and manifestation. Accordingly, the objective of this paper is to develop a framework for deriving a true simplified liquefaction triggering model consistent with a defined manifestation model, such that factors influential to triggering and manifestation are handled more rationally and consistently. Operating in conjunction with the LSNish manifestation model, the performance of the true triggering curve is compared with an existing, popular triggering curve using a set of 50 global case histories; the results are favorable for the proposed framework. Furthermore, the ability of the true liquefaction model to be used in conjunction with manifestation models that account for complex free-field soil profile stratigraphies or developed sites is a significant advantage over traditionally developed triggering models.

3D Numerical Assessment of Rammed Aggregate Pier Performance under Dynamic Loading in Liquefiable Soils

Ground improvement (GI) techniques have shown promise in effective liquefaction mitigation, but the physical mechanisms governing their three-dimensional (3D) response during dynamic loading are not yet fully understood. To evaluate the 3D performance of one GI technique, the rammed aggregate pier (RAP), in-situ site characterization, full-scale field test data, and calibrated baseline constitutive soil model parameters are combined to model the 3D fully coupled hydromechanical response of natural (unreinforced) and improved (reinforced) soil profiles. To the authors’ knowledge, this contribution represents the first 3D model of a columnar-reinforced soil profile being calibrated using full-scale field testing. The field observations from the comprehensive ground improvement testing (GIT) program in New Zealand and insights from two-dimensional (2D) finite-difference analyses using constitutive model parameters calibrated against the field measurements were used. The developed 3D models were subjected to dynamic loads simulating the excitation generated by a vibroseis truck at one of the in-situ test sites of the GIT program, as well as unidirectional and bidirectional earthquake ground motions from the Canterbury Earthquake Sequence events. The 3D simulations showed that the improved soil profiles experienced reduced excess pore pressures and reduced dynamically induced shear strains compared to the natural, unreinforced soil models. The developed 3D finite-element predictions were compared and validated vis-à-vis the field observations of the GIT program. Compared to 2D analyses, 3D analyses provide a more accurate description of actual field conditions, and, for instance, it was observed that multidirectional shaking has a significant effect on liquefaction triggering, particularly for natural soil profiles. Finally, it was shown that soil densification around the installed pier elements and the lateral earth pressure increase within the densified soil and are the primary ground improvement mechanisms contributing to the reduction of dynamically induced shear deformations and excess pore pressure generation during earthquake shaking. It was also found that the permeability and shear stiffness of the installed RAP piers did not have a significant influence on the pore pressure response and shear strains developed along the centerline of the improved area.

Analysis of Liquefaction Triggering in the Nakdong-river Delta Sediments Based on Broadband Hybrid Ground Motion Simulation and Microtremor Array Method

We present a case study of liquefaction triggering analysis performed in the Nakdong-river delta region, based on the shear wave velocities obtained by the Microtremor Array Method and the ground motions generated by the broadband hybrid ground motion simulation. Assuming a M<sub>w</sub>6.2 earthquake occuring at the Dongrae fault, the ground motions at the studied sites exceeded the design spectra provided by the Korean Design Standard and many of the studied sites exhibited low factors of safety against liquefaction triggering. We found that the Idriss and Boulanger (2008) method yields larger Cyclic Stress Ratios (CSR), compared with the site response analysis based method. Cyclic Resistance Ratios (CRR) estimated from the shear wave velocity were sensitive to small changes in the velocity, which suggests that high accuracy and depth resolution are desired when the shear wave velocity is used to estimate the CRR.

Assessment of the prediction of ground motion parameters in 1D ground response analysis using data from seismic arrays and centrifuge experiments

Peak ground acceleration (PGA), peak ground velocity (PGV), and spectral acceleration are among the most widely used metrics to represent seismic hazard characteristics in practice. Several simplified seismic design procedures to evaluate liquefaction triggering, slope stability, or structural response have also proposed other ground motion parameters (GMPs) to represent a ground motion’s intensity, duration, and frequency content. To account for soil effects, these parameters can be obtained from the results of one-dimensional (1D) ground response analyses. Few studies have systematically evaluated the prediction of these additional parameters from the results of ground response analyses. This study presents an exhaustive review of the accuracy and precision of the prediction of 19 common GMPs from the results of 1D ground response analyses using vertical seismic arrays and centrifuge tests. Total stress nonlinear analyses are conducted using the software DEEPSOIL along with equivalent-linear analysis. A reference dataset composed of 10 sites and 306 ground motion recordings representing varying conditions of seismic excitation is employed. The findings of this study showed that while the models produced a reasonable approximation of spectral accelerations, a general tendency toward the over-prediction of most parameters was revealed. The results identified that the mean period ( Tm) yielded the lowest bias, and other parameters, such as the predominant spectral period ( To), PGA, and PGV, also offered some improvements over the other parameters included in this study.

Intersectional Impacts of the 2021 Mw 7.2 Nippes, Haiti, Earthquake from Geotechnical and Social Perspectives

ABSTRACTThe Mw 7.2 Nippes, Haiti, earthquake occurred on 14 August 2021 in Haiti’s southwest peninsula and in the midst of significant social, economic, and political crises. A hybrid reconnaissance mission (i.e., combined remote and field investigation) was coordinated to document damage to the built environment after the event. This article evaluates two ground-motion records available in Haiti in the context of the geology of the region and known areas with significant damage, such as Les Cayes. We also present a new map of time-averaged shear-wave velocity values to 30 m depth (VS30) for Les Cayes and Port-au-Prince based on the geostatistical approach of kriging and accounting for region-specific geology proxies and field measurements of VS30. Case studies of ground failure observations, including landslides and liquefaction triggering, are described as well as the intersection of social and engineering observations. Maps depicting this important intersection are provided to facilitate the assessment of how natural hazards and social conflicts have influenced the vulnerability of Haiti’s population to earthquakes.

Observations on the Seismic Loading of Rigid Inclusions based on 3D Numerical Simulations

Rigid inclusions are increasingly being specified in seismic regions to transmit foundation loads to competent strata at depth due to their ability to provide excellent static performance and potential for cost-savings over other forms of ground improvement and/or deep foundations. Despite their widespread application in seismic regions, the seismic kinematic interaction of rigid inclusions is not well understood. This study presents a series of parametric numerical simulations specifically conducted to capture the kinematic soil-rigid inclusion interaction under seismic loading to identify key mechanisms that contribute to seismic performance. The effect of ground motion variability, area replacement ratio, surface crust thickness, embedment into a competent layer, liquefiable layer thickness, and steel reinforcement is systematically investigated. Although the rigid inclusion may not prevent liquefaction triggering, severe amplification associated with dilation spiking of transiently liquefied soil is mitigated and the onset of liquefaction delayed due to the soil-rigid inclusion interaction. The role of static arching to alter the geostatic stress state prior to and during shaking is shown to be responsible for significant and heretofore unknown coupled fluid-mechanical interaction that drives the performance of the rigid inclusion within the reinforced soil system. The kinematic flexural demand following the triggering of liquefaction and phase transformation associated with cyclic mobility is met through transient increases in axial load, which increases the confinement of the grout comprising the rigid inclusion, and therefore its moment capacity. The complex mechanisms identified in this work should be used to help identify which subsurface conditions may lead to responses, guide design decisions regarding selection of reinforcement and embedment, and provide a basis for assessments of the anticipated kinematic demands in view of the beneficial axial load-moment capacity interaction following soil liquefaction.

Liquefaction potential hazard study at UIN Datokarama, Palu City, Central Sulawesi

In June 2019, the Asian Development Bank approved emergency rehabilitation and reconstruction assistance (EARR) to help Indonesia rebuild better critical infrastructure damaged by the 2018 Palu-Donggala earthquake. One of the EARR sub-projects is the reconstruction of Universitas Islam Negeri (UIN) Datokarama that suffered significant damage from the combined effects of the tsunami and earthquake. The design for the building's reconstruction incorporated better principles of deconstruction, including pile foundations to ensure the facilities are earthquake, tsunami, and liquefaction resistant. This study purpose is to evaluate liquefaction potential and estimate its severity or damage potential to structures in the reconstruction site. Liquefaction potential will be assessed in two ways, first by using soil deposits grain sizes distribution method from Japan technical standards for port and harbour facilities and second by safety factor against liquefaction (FOS) method using the SPT-based liquefaction triggering analysis with the revised magnitude scaling factor (MSF) relationship by Idriss and Boulanger. Liquefaction Potential Index (LPI) from Iwasaki will be used for estimating liquefaction severity. The analysis is performed on dataset taken from 6 boreholes in location dominated by saturated sandy soil and shallow ground water. Based on the result, liquefaction potentially triggered at various depth with consistent LPI index at > 15, The reconstruction site has a very high liquefaction risk.

An insight on the experimental volumetric behaviour of gassy soils

Induced Partial Saturation (IPS) is one of the most innovative and promising countermeasures to mitigate soil liquefaction risk. Mechanical benefits of air/gas bubbles occluded within the pore water have been studied in the last decade through undrained cyclic tests on quasi-saturated (gassy) soils, demonstrating that the increased pore fluid compressibility prevents liquefaction triggering. The greater compressibility of the air bubbles rules the volumetric strains of gassy soils during seismic shaking reducing the build up of the pore water pressure. Mele et al., (2022) verified that, at the laboratory scale, due to lower frequencies of the applied cyclic loads, a non-negligible amount of soil volumetric strains is due to dissolution of air bubbles in the water (εv,diss). The outcomes of some simple compression tests carried out on a two-phase medium made of air/water confirm that such amount cannot be correctly computed with the Henry’s law, which considers the dissolution process of air into water in the hypothesis of continuous air phase. Experimental evidences highlighted that εv,diss is mainly ruled by the continuity of air phase (linked to the chosen experimental procedure), and it exceeds the theoretical previsions when air phase is discontinuous with single bubbles occluded in the fluid phase.

The Over-Prediction of Seismically Induced Soil Liquefaction during the 2016 Kumamoto, Japan Earthquake Sequence

Following the M7.0 strike-slip earthquake near Kumamoto, Japan, in April of 2016, most geotechnical engineering experts believed that there would be significant soil liquefaction and liquefaction-induced infrastructure damage observed in the densely populated city of Kumamoto during the post-event engineering reconnaissance. This belief was driven by several factors including the young geologic environment, alluvially deposited soils, a predominance of loose sandy soils documented in publicly available boring logs throughout the region, and the high intensity ground motions observed from the earthquake. To the surprise of many of the researchers, soil liquefaction occurred both less frequently and less severely than expected. This paper summarizes findings from our field, laboratory, and simplified analytical studies common to engineering practice to assess the lower occurrence of liquefaction. Measured in situ SPT and CPT resistance values were evaluated with current liquefaction triggering procedures. Minimally disturbed samples were subjected to cyclic triaxial testing. Furthermore, an extensive literature review on Kumamoto volcanic soils was performed. Our findings suggest that current liquefaction triggering procedures over-predict liquefaction frequency and effects in alluvially deposited volcanic soils. Volcanic soils were found to possess properties of soil crushability, high fines content, moderate plasticity, and unanticipated organic constituents. Cyclic triaxial tests confirm the high liquefaction resistance of these soils. Moving forward, geotechnical engineers should holistically consider the soil’s mineralogy and geology before relying solely on simplified liquefaction triggering procedures when evaluating volcanic soils for liquefaction.

Improving soil liquefaction prediction through an extensive database and innovative ground motion characterization: A case study of Port Island liquefied site

Liquefaction is a phenomenon in which soils lose their strength and stiffness significantly during earthquake shakings. It is very important to accurately predict the liquefaction triggering and permanent displacement of liquefied sites under different seismic conditions. This study systematically investigates the effect of ground motion characteristics on the evolution of important physical quantities during the liquefaction process, while the relative capacity of various ground motion intensity measures (IMs) in predicting the pore-pressure generation and the permanent deformation in liquefiable soils are studied. An extensive database containing 501 three-component ground motion records is established to improve soil liquefaction prediction under different earthquake scenarios. A significant number of fully nonlinear dynamic analyses are performed for the Port Island liquefied site, where advanced constitutive models are used to realistically characterize the nonlinear soil behaviors. Results from numerical simulations demonstrate that the energy-related IMs such as CAV5 have a superior predictive capacity than the peak ground acceleration in predicting the liquefaction initiation and permanent displacement, but the predictions based on scalar IMs are not sufficient because residuals are strongly depended on earthquake magnitude and rupture distance. On the other hand, vector IMs that incorporate both energy and peak value characteristics of ground motions can improve the predictive capabilities regarding pore pressure generation and permanent deformation in liquefiable soils. The study helps lay down the basis towards an improved procedure for liquefaction hazard evaluation and mitigation.

Recommended b-Value for Computing Number of Equivalent Stress Cycles and Magnitude Scaling Factors for Simplified Liquefaction Triggering Evaluation Procedures

Recommended b-Value for Computing Number of Equivalent Stress Cycles and Magnitude Scaling Factors for Simplified Liquefaction Triggering Evaluation Procedures

Earthquake-Induced Flow-Type Slope Failure in Weathered Volcanic Deposits—A Case Study: The 16 April 2016 Takanodai Landslide, Japan

The aim of this paper is to provide new insight into the catastrophic mobility of the earthquake-induced flow-type Takanodai landslide that occurred on 16 April 2016, which had fatal consequences. A geological and geotechnical interpretation of the site conditions and experimental investigations of the mechanical behavior of weathered Kusasenrigahama (Kpfa) pumice are used to characterize the landslide failure mechanism. The results of large-strain undrained torsional shear tests indicate that Kpfa pumice has the potential to rapidly develop very large shear strains upon mobilization of its cyclic resistance. To evaluate the actual field performance, a series of new liquefaction triggering analyses are carried out. The liquefaction triggering analyses indicate that Kpfa pumice did not liquefy during the Mw6.2 foreshock event, and the hillslope remained stable. Instead, it liquefied during the Mw7.0 mainshock event, when the exceedance of the cyclic resistance of the Kpfa pumice deposit and subsequent flow-failure type of response can be considered the main cause of the landslide. Moreover, the combination of large cyclic stress ratios (CSR = 0.21–0.35)—significantly exceeding the cyclic resistance ratio CRR = 0.09–0.13)—and static shear stress ratios (α = 0.15–0.25) were critical factors responsible for the observed flow-type landslide that traveled more than 0.6 km over a gentle sloping surface (6°–10°).

DPT-based seismic liquefaction triggering assessment in gravelly soils based on expanded case history dataset

The gravelly soil liquefaction caused by earthquake motions has been observed and reported in different regions in the world. However, few studies have been conducted to develop models for its prediction and risk assessment. Furthermore, the single available model was developed merely based on one case history earthquake. Thus, to bridge this gap in research, this study first created a comprehensive database of dynamic penetration test (DPT) using the documentation of eight global earthquakes, which includes a considerable variation of earthquake magnitudes, the frequencies of motions, epi-central distance, geometry type, deposit layering, gravelly soil depth, geometry type, and soil properties. Then, a deterministic model was developed to estimate the cyclic strength ratio (CRR) to estimate the safety factor (SF) against liquefaction triggering. Then, to account for uncertainties in the estimations of parameters and model prediction, Bayesian mapping function and logistic regression were applied to develop probabilistic models to classify liquefied and non-liquefied regions for liquefaction occurrence prediction. The maximizing likelihood function was used to calculate the model's parameters. The effect of the bias sampling factor was surveyed via supposing a range of variation for its value to discover its decent value. To validate the presented models, they were compared to the existed model. The results were studied via two issues, as a capability that shows the accuracy of the model's prediction and a risk issue via a recall index.

Validation of models used to predict the effects of lateral spreading by comparison of experimental and numerical response surfaces

Following the LEAP-UCD-2017 and LEAP-ASIA-2019 exercises, an immense database of dynamic centrifuge data has been established for the purpose of validating numerical models that predict lateral spreading due to liquefaction. Using the experimental database and regression analyses, researchers have mapped a response surface to elucidate the relationship between soil density and shaking intensity to expected residual slope displacement. While it may not be practical to develop a database of experiments for every liquefaction scenario, the LEAP response surface may be conveniently used by others to assess that their numerical simulation procedures produce reasonable predictions for lateral spreading problems. To illustrate the value of response surfaces during the validation of numerical models, we developed a numerical response surface using the PDMY02 model implemented in the OpenSees finite element framework as an example test case. The methodology used to establish five PDMY02 constitutive model calibrations and the procedures to develop the numerical model are presented. One of the most important components of the calibration procedure, the attempted matching of the liquefaction triggering curves, is discussed in detail. Two input motions were considered for this work; one was a clean 1 Hz tapered sine wave, and the other included a 3 Hz component superimposed on the 1 Hz tapered sine wave. A numerical response surface was mapped for each input motion using the calibrations representing three relative density states. The greater transparency allows for comparisons between the numerical and experimental surfaces that illustrate the capabilities and limitations of numerical procedures, and therefore, this exercise should be integrated into future efforts to validate numerical models.