Geo-Congress 2022: Geophysical and Earthquake Engineering and Soil Dynamics

Electrical Resistivity (ER) is a non-destructive geophysical method for geotechnical and geo-environmental investigation. This technique is promising in producing soil moisture map and obtaining subsoil profile information. Additionally, the saturated and unsaturated soil parameters can be evaluated through the electrical resistivity method. The saturated and unsaturated soil properties are critical parameters for earthen infrastructure design, especially the landfill bottom liners and top covers, whereas the soil hydraulic properties play a significant role in the overall performance. On the other hand, Soil water characteristic curve (SWCC) determination is the primary step in the landfill alternative cover design providing values of field capacity (θ_FC) and wilting point (θ_WP), water storage capacity, hydraulic conductivity, etc., However, the existing methods for obtaining SWCC have limitations in efficacy. Consequently, the design parameters for landfill top cap may have certain degrees of inadequacies. Thus, this study attempts to use electrical resistivity method as an alternative to determine the essential unsaturated design parameters (θ_FC and θ_WP) of landfill alternative cover. In this study, the quantitative relationships between resistivity-moisture content and resistivity-suction were constructed using field data followed by the van Genuchten model. These relationships among the resistivity-suction-moisture content were used to estimate the θ_FC and θ_WP. The magnitude of θ_FC and θ_WP was found slightly underestimated than the actual design values. However, the methodology developed in this study to estimate the design parameters of landfill cover proved to be a viable alternative method. An analytical approach was also introduced to compute water storage capacity of alternative cover system using resistivity data.

High real estate prices and prime location make a 270-acre Superfund site underlain by soft and variable compressible mine tailings centrally located in the Salt Lake City urban corridor worth considering for commercial development. Although a series of large test fills and footing load tests were performed to provide a better characterization of the compressibility of the soils at the site and to evaluate the feasibility of developing the site from a settlement perspective, huge uncertainties remained in future building performance as the subsurface explorations showed extreme variability in subsurface conditions. 2D geophysical studies have been used for two primary purposes on the site. First, geophysical investigations have been used to correlate with the large-scale field-testing results and extend these more expensive investigations to the variable site conditions. And second, as the first, pile supported structures are being constructed on the site, geophysics is being used to help understand the risks associated with pile installation. Specifically, orthogonal 2D MASW lines were conducted to image the subsurface for soft and stiff locations potentially indicating rubble or debris in the subsurface. The surveys were used to guide auger probes and observations of obstructions during pile installation. This case history paper presents the results of the geophysics test programs, parallel borings, CPT, and load tests, and shows that 2D geophysical soundings can be used to constrain subsurface uncertainties, drive successful foundation design, and control construction phase obstructions.

This study is an attempt to experimentally validate the presence of a high angle reverse fault at Aharbal Falls of Kashmir Valley. The compressional forces across the south-southwest bounding orogeny has resulted in reverse faulting of Panjal Traps (Early Permian) over the Fluvio-glacial Deposits (Pleistocene). Single-station microtremor horizontal-to-vertical spectral ratio (MHVSR) method and multichannel simulation with one-receiver (MSOR) surface wave tests have been conducted along a profile across the suspected fault zone. HVSR curves exhibit an anomalously high H/V amplitude (~8) at ~4.5 Hz within the fault zone. As the distance from fault zone increases the amplitude decreases gradually to ~2–3 in stable zones. Sub-surface shear wave velocity also reveals a drop from 1,250–1,350 m/s in surrounding host rock to ~860 m/s in the fault zone. The study concludes that MHVSR can be used as an effective tool for rapid detection and validation of reverse faults.

Seismic methods are often used for detection of pre-collapsed sinkholes (voids) under roadway for remediation to minimize the risk to the safety of the traveling public. While the active-source seismic methods can provide accurate subsurface profiles, they require closing the traffic flow for hours during testing and potentially cause sinkhole collapse due to ground perturbation by source excitation. To address these issues, we present a 2D ambient noise tomography (2D ANT) method for imaging voids under roadway. The method requires recording of vehicle-induced traffic noise using a linear array of geophones placed along a roadway. The cross-correlation function (CCF) is then extracted from traffic noise recordings and inverted to obtain velocity structures. Passing-by vehicles are assumed as moving sources along the receiver array for the forward simulation and inversion of the CCF. To demonstrate the method’s capabilities, it was applied to field noise data collected both pre- and post-grouting for assessment of a repaired sinkhole under US 441 highway, Florida, US. The pre-grouting result shows that the method is capable of resolving the subsurface S-wave velocity (Vs) structure and detecting a buried void. The post-grouting result suggests that the grouting operation was successful, and the void was sufficiently filled.

We have constructed a one-meter cubical model made of low-strength concrete that simulates Florida limerock in which to test a new geophysical instrument. In the experiment reported, we used an instrumented hammer to apply a pulse load at one corner of the top surface. The resulting accelerations were recorded using a string of receivers placed along a diagonal line of the top surface and these waveforms were inverted using an ABAQUS-based inversion model to determine the elastic properties of the specimen. To reduce computing time, the three-dimensional cube was represented in ABAQUS using an axisymmetric model and the inversion routine used a regularized Gauss–Newton iteration algorithm. To provide independent corroboration, the modulus results from the inversion were compared with modulus values computed from free-free resonant column test data collected from cylindrical samples of the synthetic limerock used to construct the cube specimen. The modulus properties from both techniques were found very similar to one another.

Robinson Lake Dam is an existing, unregulated, earthen dam that poses multiple dam safety concerns. The City of Franklin, Tennessee, proposed to redevelop the area to include a recreational lake with a rehabilitated dam embankment. The dam site lies within the Carters Limestone formation, which contains limestones prone to development of karstic features. Three existing sinkholes exist in the downstream area of the dam embankment, and water is seeping through the right abutment at an estimated rate of 200 gallons per minute (757 liters per minute). To design rehabilitation measures for the dam, the limestone bedrock was evaluated by performing rock coring, water pressure tests, and three geophysical survey methods. The purpose of this paper is to detail the comprehensive subsurface investigation program consisting of geotechnical test borings and geophysical survey methods for the design of seepage mitigation measures. The mitigation measures include a targeted foundation grouting program, focused in areas of encountered karstic anomalies from the subsurface investigation program to reduce the potential for seepage and sinkhole development.

Highway slopes (HWS) with or partially saturated high-plastic clay soil have typically been a source of frequent shallow slope failures. Rainwater infiltrates the soil, lowering suction, decreasing shear strength, and impacting HWS stability. Thus, it is critical to determine the soil degree of saturation when analyzing the stability and performance of the HWSs. Electrical Resistivity Imaging (ERI) offers subsurface imaging, which can be used to evaluate the stability of HWSs. The objective of the current study was to identify the extent of the failure zone of an HWS constructed by high-plastic Yazoo clay. A failed HWS along the I55S exit toward Sowell road in Canton, MS, is considered a reference slope. During this study, the 2D ERI test was implemented, and the ERI survey lines were considered at the middle and toe of both failed and not-failed zones of the HWS. The Earth-Imager 2D software package was used to analyze the resistivity data. The ERI inversion results indicated the existence of high-moisture content in both failed and non-failed zone of the HWS. However, a higher electrical resistance is detected at the failure zone, which takes place as the soil gets disturbed due to soil movement.

This study investigates the influence of different wavefield transformation techniques on the resolution of derived dispersion data from the multichannel analysis of surface waves (MASW). In this regard, the performance of the four common transformation techniques, including Frequency Domain Beamformer (FDBF), frequency–wavenumber (FK), phase shift (PS), and slant stack (τp), is examined for different subsurface and wavefield conditions. The four transformation techniques resulted in similar dispersion images for sites with a very deep impedance contrast (~>100 m) with an almost homogenous soil profile. On the other hand, for sites with a very shallow impedance contrast (~<20 m), it is observed that the PS method often produces very low-quality dispersion data (lacking a clear trend), whereas the other methods generate high-quality dispersion data. Additionally, the FDBF-cylindrical is observed to be the most advantageous method for mitigating near-field effects. For complex sites where multiple modes of propagation are resolved, the four transformation techniques are observed to have different sensitivities to higher modes. Therefore, a composite dispersion approach from the four transformation techniques is recommended for use at such sites to avoid mode misidentification, increase the reliability of the data, detect multiple modes, and enhance the final shear wave velocity profile from the inversion process.

Large-scale ground motion simulations were carried out in this research to simulate an Mw 4.4 aftershock of the 2007 Niigata-Chuetsu earthquake that was recorded at the Kashiwazaki-Kariwa Nuclear Power Plant (KKNPP) in Japan. Ground motions up to a maximum frequency of 3 Hz at this site were generated using SW4 on the high-performance computing clusters at Los Alamos National Laboratory. Sub-surface soil characterization information was combined from KKNPP, Kyoshin Network (K-NET), and Kiban Kyoshin Network (KiK-net) using a kriging algorithm to produce a high-resolution soil model for incorporation in the large-scale model, and contrasted with other modeling techniques. Simulated ground motion histories are validated qualitatively using a Goodness-of-Fit scoring scheme. In addition, simulations are compared with both horizontal and vertical ground motion prediction equations (GMPEs). Overall, the simulations are considered validated by the recorded data and GMPEs.

Highway Slopes (HWS) with fully and partially saturated high-plastic clay soil have typically been a source of frequent HWS vulnerability. Water infiltrates the slope after rains, lowering suction, decreasing shear, affects slope stability. Thus, it is critical to monitor the degree of saturation inside shallow depth in HWS. Field instrumentation (FI) as well as Electrical Resistivity Imaging (ERI) used to investigate the soil subsurface conditions in terms of soil moisture variation, sinkholes, cracks, and perched water zones. The current study intent to analyze ERI and FI to evaluate the performance of an HWS made of expansive Yazoo clay soil. Moisture content and water potential probes were installed at the crest, middle, and toe of the slope at different depths to monitor the moisture variations. Moreover, the 2D ERI test was conducted in two survey lines at the crest and middle of the slope to image the continuous soil subsurface profile in terms of moisture variation. Based on the FI and ERI data, the shallow depth of the HWS observed to have low resistivity, low-soil matric suction, high-volumetric moisture content, and perched water zone formation.

Seismic geophysical testing and numerical modeling was employed to conduct a slope stability study. The slope of interest faces a rock quarry and supports an existing water storage tank. A second water tank is also planned to be installed on top of the slope. The toe of the slope is immediately adjacent to a haul road on the quarry site. A concern was that the ground vibrations induced by rock blasting in the quarry may create excessive shear stress on the slope and result in its failure. The geophysical investigation consisted of running six seismic refraction and multichannel analysis of surface waves (MASW) acquisition lines at various locations across the site. Using results of the geophysical testing, subsurface velocity models were constructed for two cross sections along the slope of interest. These velocity models were then used as inputs for a finite-element modeling of the slope. The finite-element model of the slopes was calibrated using actual blast vibration records collected at the surface of the slope near the existing tank. The purpose of calibration was to ensure that the stress–strain levels calculated with the finite-element model were consistent with those of the measured ground vibrations. The blast-induced vibration time history at the base of the slope was calculated by solving the inverse frequency response functions of the finite-element model. The calculated base acceleration time history was used as the input for subsequent stability analysis. Finally, for each tank, a frequency-dependent vibration criterion was developed to ensure a minimum factor of safety of two.

The Multichannel Analysis of Surface Waves (MASW) method was used to develop shear-wave velocity profiles in a coastal environment where pile driving was planned to initiate. The produced velocity models were then used to calculate the soil settlement and maximum estimated foundation load/settlement caused by pile driving at an existing nearby structure. Vibration thresholds were proposed based on the pile driving equipment to mitigate the risks of structural damage to the nearest existing structure. Finally, using remote seismographs, construction-induced vibrations were monitored.

Penetration is involved in many geotechnical engineering practices such as site characterization and pile installation. In this study, we investigated the influence of pausing-induced stress relaxation on the penetration process using photoelasticity. A thin cone penetrometer was designed and penetrated a photoelastic granular specimen in two different ways: one is continuous penetration, during which the penetrometer penetrates the specimen continuously for a target travel distance; the other is termed as intermittent penetration, which consists of two short penetration stages separated by a long pausing stage. The penetration rate and overall penetrometer travel distance for the two cases are kept the same. Stress relaxation was observed during the pausing stage and the influence of stress relaxation on the subsequent penetration process was evaluated by comparing the penetration resistance, and force chains, stress field, and displacement field of the granular specimen. Results indicate that pausing-induced stress relaxation is due to particle rearrangement and causes reduction in penetration resistance within a limited travel distance.

The evaluation of unknown foundations continues to be an important issue with the increasing interest in foundation reuse and rehabilitation. Several nondestructive testing (NDT) and geophysical methods have been proposed to characterize unknown foundations. One of the most robust methods is the Parallel Seismic (PS) method, which was purposely developed to determine the unknown or undocumented depth of foundations. The PS method relies on recording the arrival time of waves at a borehole alongside the foundation after the top of the foundation is struck by a hammer. When the arrival times are plotted as a function of depth, the foundation bottom can be located at the break in the slope of the arrival times. This break in the slope occurs once the downward propagating wave moves pass through the foundation into the soil surrounding the toe of the foundation. Several studies have shown the robust capabilities of PS on both metallic and non-metallic foundations. However, there are a number of issues present in the PS method, including complications introduced by foundation flaws. To address this concern, this paper presents the use of full waveform tomography with PS data on a synthetic soil-foundation model. Rather than rely solely on first arrival times, the full waveform tomographic approach attempts to solve an inversion problem that matches the entirety of the measured PS waveforms with waveforms acquired from numerical simulations of wave propagation in a subsurface model. The results of this study demonstrate that the full waveform PS approach provides a more comprehensive evaluation of the unknown foundation geometry, particularly the extent of anomalous conditions.

At construction sites, the use of load distributive compression anchors (LDCAs) is increasing because of their high-bearing capacity and removable steel strands. Multiple anchor bodies installed along the anchor length transmit the loads applied to the steel strands to the grout and ground in an LDCA. Therefore, it is necessary to evaluate the effect of multiple anchor bodies on the load transfer behavior of an LDCA. In this study, a physical model test system is proposed to investigate the load transfer characteristics of an LDCA. An LDCA was physically scaled down, and a calibration chamber designed to apply confining pressure on the ground was used. Furthermore, considering the structural characteristics of an LDCA, the axial strains of the grout at various locations were measured. The pull-out test was conducted using the proposed test method, and the appropriateness of the proposed testing system was validated by the test results.

Available conventional test methodologies to estimate the suitability of compacted soil in various engineering developments are time-consuming, expensive, and destructive. This research aims to assess the practical applicability of electrical resistivity to evaluate compacted soils. To achieve this goal, eagle ford shale samples were collected from the newly constructed bottom liner of the City of Irving landfill, Texas. Using supersting IP resistivity equipment, the electrical resistivity of compacted samples with different void ratios and molding water contents were measured in the laboratory. This study investigated the relationships between the soil resistivity of compacted clay and moisture content, unit weight, and degree of saturation. Experiments also demonstrated that the electrical resistance of the compacted clay correlates with compaction effort. In standard proctor test, the resistivity value at maximum dry density (MDD) decreased 18.03% compared to reduced proctor test, whereas it decreased 6.56% in modified proctor test. Changes in electrical resistivity with the compressive strength were also observed. Soil samples prepared with moisture contents of 17.3%, 21.4%, 25.7%, and 29.3%, resistivity value decreased by 65.5%, 56.5%, 44.8%, and 38.5% of the initial value at failure, respectively. The process of using an electrical resistivity imaging technique to obtain information about the geotechnical parameters of compacted clay enables a means of predicting those parameters more effectively.

Piezometer installations at Little Bear Creek Dam were proposed by the Tennessee Valley Authority (TVA) based on the outcome of a Semi-Quantitative Risk Assessment (SQRA) that identified data gaps in the understanding of site hydrogeological conditions. To provide TVA with a better understanding of the karstic site, a surface geophysical investigation, subsurface exploration, and instrumentation installation program was performed. The surface geophysical investigation was conducted at the site to identify targets for subsurface exploration and piezometer installation. The subsurface exploration and instrumentation installation programs were critical components in enhancing the understanding of pore water pressures and seepage gradients within the earthen embankment, foundation soils, and bedrock. Nine vibrating-wire piezometers were installed in the main earthen embankment dam, seven of which were installed within standpipe piezometers. The results show that the integration of multiple geophysical methods can serve to maximize the value of subsurface explorations.

Characterizing active landslides is a significant challenge for geotechnical engineers and geologists, as issues of access, instability, and soft soils can impact the ability of heavy equipment to reach critical locations. Surface-based geophysical methods can be an important tool in these investigations, as they can be deployed quickly by a small team without the use of heavy equipment. In addition, surface-based geophysics can provide two- or three-dimensional profiles of the subsurface that can provide detailed information on stratigraphy and assist with locating critical layers. When used as part of an integrated site characterization effort, geophysical methods can be used to extrapolate results from limited borings or in situ tests and identify problem areas that may require additional investigation. This paper presents results from both electrical and seismic geophysical surveys at two active landslides in Alabama. Both landslides occurred along active roadways and issues with utilities and topography made investigating the slides challenging. The geophysical results were able to identify the likely failure plane at each site, which was confirmed through comparison with inclinometer and boring data. Identifying this failure zone would have been difficult if not impossible to do from either the resistivity or the seismic results alone, but integrating the results from these two methods allowed the zone to be identified. This integrated characterization approach provides a more reliable ground model for analyses and design of repairs. Challenges, such as irregular terrain and accounting for topography, encountered on these deployments, along with recommendations for future studies are discussed.

The resilient modulus (M_R) value that is selected to represent the subgrade soil layer in a pavement layer profile significantly influences the predicted pavement performance using the new guide for AASHTOWare pavement mechanistic-empirical design (PMED). M_R can be measured through non-destructive field tests [i.e., falling weight deflectometer (FWD)] or laboratory repeated triaxial load tests on remolded or undisturbed samples. In this study, FWD tests were performed on 11 asphalt pavement sections across the state of South Carolina to estimate the M_R of the subgrade soil using the AASHTOWare 2017 back-calculation tool. Undisturbed samples were extracted from the same pavement locations using a thin-walled Shelby tube, and tested in the laboratory using AASHTO T307-99 to obtain the M_R. Index tests (sieve analysis, Atterberg limits, specific gravity, moisture content, and standard Proctor density tests) were performed to obtain PMED Level 1 design input parameters. A correlation was developed between the FWD back-calculated M_R and laboratory-measured M_R to facilitate an estimate of M_R (using a C-factor) for PMED Level 2 design inputs for South Carolina and similar geologic regions. The influence of the subgrade modulus selection methodology was evaluated by comparing the pavement performance results from PMED trial designs using M_R found by four different methods.

One-dimensional site response analyses (1D SRAs) are the most widely used tool to assess site-specific seismic response. However, compared to 2D and 3D SRAs, 1D SRAs are limited in their ability to capture some wave propagation mechanisms. Here, 2D and 1D SRAs are conducted on V_S correlated random fields to evaluate: (1) the discrepancies in the median 2D and 1D seismic responses, (2) the effects of V_S spatial variability features (e.g., correlation length, θ) on the 2D response, and (3) the effect of using 1D SRA-based ground motions to estimate intensity measures (IMs) towards getting insight into the seismic performance of geosystems. Results indicate that (1) median 2D responses are higher than median 1D responses, and the discrepancy increases with V_S variability (σ_lnVs), (2) σ_lnVs has a stronger effect than other V_S variability features on the 2D and 1D seismic responses, and (3) IMs might be underpredicted when estimated using 1D SRA-based ground motions, and thus the expected geosystems’ seismic performance overestimated.

A new, easy-to-implement method for the free vibration analysis of Euler-Bernoulli beam-columns embedded in a two-parameter elastic soil is presented. The non-homogeneity of the soil was accounted for by assuming a linear distribution of the modulus of subgrade reaction. The governing differential equation (GDE) of the proposed structural element is solved using the differential transform method (DTM). This method is implemented since finding an analytical solution by means of other traditional approaches is a complex task and becomes even more challenging when the non-homogeneity of the soil is introduced in the formulation. Examples are presented to validate the proposed formulation. The results show that the introduction of a shear layer and soil homogeneity has a strong influence on the natural frequencies of rigid and semirigid beam-columns. Comparisons are performed to demonstrate the simplicity and accuracy of the proposed method.

A broad spectrum of well-graded, coarse-grained soils are commonly present in natural deposits, though characterization of these materials has been approximated using sand-based engineering methods in liquefaction evaluations. Through combined results of 31 constant stress direct simple shear and drained triaxial compression tests, this study experimentally investigates the effect of mean grain size (D₅₀) and gradation (C_u) on the drained monotonic strength and stress-dilatancy of poorly- to well-graded, coarse-grained soils. Coarse-grained mixtures of varying D₅₀ and gradations were prepared to relative densities of 20%–75% and tested under a range of overburden stresses. Results are analyzed in terms of the frictional resistance and dilative contributions to the shear strength of soils with varying gradations, as compared to clean sands, using different shearing modes. It is shown that (1) increased gradation of soils increases the peak shear strength and frictional resistance due to a greater initial rate of dilation exhibited in well-graded, coarse-grained soils; and (2) current stress-dilatancy relationships underestimate the dilative behavior of well-graded test materials.

Past earthquakes have indicated that bridge superstructure tends to restrain the movements at the top of the abutments (or piers) while lateral spreading tends to push the piles towards the direction of soil movement. This leads to the back-rotation of abutment and piles, which is different to the pile response estimated using traditional fixed or free pile head conditions. Although, the superstructure (deck) resistance is considered in simplified methods such as the Caltrans (2012) approach, the analysis cannot mimic the pile/abutment back-rotation besides several other limitations related to the approach used to account for the deck resistance. This paper introduces a modified approach to overcome these limitations. The revised approach is based on the same basic framework as in Caltrans (2012) but modifications are introduced to properly account for the deck resistance. A user-defined “deck spring” is introduced into the pushover analysis to represent the superstructure resistance instead of applying it to the slope stability model. The differences between these two approaches are highlighted using an example.

This study aims to investigate the liquefaction prediction and sediment manifestation of Palinurus Road site in Christchurch, New Zealand, subjected to September 2010 Darfield and February 2011 Christchurch events. The results of simplified methods including liquefaction vulnerability indexes (LVI) and CPT-based liquefaction triggering analysis supplemented with a complex 2D nonlinear deformation analysis (NDA) were evaluated and compared. The cone penetration data (CPT) underwent an inverse filtering procedure to correct for thin-layer and transition zone effects. Common LVIs were computed using the measured and combination of inverse-filtered CPT data and site-specific fines content calibration. Two-dimensional NDA was carried out with PM4Sand constitutive model for liquefaction modeling in sand-like units. The liquefaction manifestation potential is investigated using the results of NDA. The results achieved from different liquefaction prediction methods were examined to shed light on the liquefaction potential and occurrence of surface manifestation at this site during and after 2010 Darfield and 2011 Christchurch events.

Nonlinear behavior of soil and pile is critical in seismic performance-based design of structures, while it is often neglected in seismic soil-pile-structure interaction (SPSI). To quantify the effects of soil-pile nonlinearity, a new nondimensional parameter called Pile Strength index, is proposed. This index determines the level of influence of soil-pile-structure interaction on the response of systems. The Pile Strength index is defined such that as it increases, piles tend to behave linearly. Whereas, small values of the index imply highly nonlinear piles, in which soil-pile-structure interaction is of paramount importance. As the focus of this paper is on the lateral behavior of pile foundations, a simplified nonlinear sway model is developed to evaluate the seismic response of structures on pile foundations. An extensive parametric study of the model is conducted to reveal the interplay of the proposed Pile Strength index and displacement ratios. For this purpose, a large set of nonlinear seismic time history analyses are carried out. The results are also compared to the displacement ratios proposed by ASCE 41-17. The comparison shows that in highly nonlinear soil-pile systems, inelastic displacement ratios are significantly larger than the recommended displacement ratios by the code.

Nonlinear soil behavior is typically observed in softer soils, and it is triggered by large shear strains induced by earthquake ground motions. Large shear strains are associated with higher material damping ratios and reduced shear modulus of the soil. This behavior poses a serious threat to infrastructure built on soft sedimentary deposits subjected to strong ground shaking. Kappa, 𝜅, is an empirical high-frequency spectral decay parameter that describes attenuation of seismic waves. Contributions from the source, path, and local site conditions influence 𝜅 in various degrees. Most previous studies have used only low-intensity ground motions that induce small shear strains to compute 𝜅. Therefore, the objective of this paper is to investigate whether the site-specific component of kappa (known as 𝜅₀) derived in the linear-elastic regime is an adequate proxy for capturing the attenuation of ground motions that produce larger deformations near the surface, and thus, can trigger nonlinear soil behavior. In this study, values of 𝜅 per record as well as 𝜅₀ per station are estimated at three KiK-net sites for linear ground motions (i.e., weak ground shaking intensities that do not trigger nonlinear soil behavior) and nonlinear ground motions (i.e., stronger ground shaking that induces large shear strains). We find that 𝜅 values corresponding to the linear elastic regime at these three sites are lower than their counterparts corresponding to the onset of nonlinear soil behavior. Equivalent–linear site response analyses are conducted to estimate shear strain profiles. The site response analyses results are then compared to surface recorded motions to investigate the relationship between kappa values, damping ratio, and shear strains at the onset of nonlinearity.

Finite-element analyses are used to model earthquake-induced lateral spread sites and evaluate the effects of site geometry and ground motion intensity measures (IMs) on the computed lateral spread displacements. The analyses were generated with six different geometries, two densities for the liquefiable soils, and 38 different ground motions for a total of 456 analyses. A pore pressure ratio threshold of 0.5 was used to establish a criterion for liquefaction triggering to determine which IMs are best able to predict liquefaction triggering from non-triggering in the numerical models. Cumulative absolute velocity with a minimum acceleration threshold of 50 cm/s, normalized dissipated energy, and Arias Intensity all performed similarly for correctly predicting liquefaction triggering in the models. Cumulative absolute velocity with no minimum acceleration threshold was identified as the most efficient IM for predicting lateral spread displacements by having the smallest σln. The efficiency of the displacement prediction was only reduced by about 2%–3% when using intensity measures computed only from the part of the ground motion after liquefaction is triggered. Comparatively, including information about the geometry (i.e., height of free-face, thickness of liquefiable soils) of the lateral spread site reduces σln by a further 5%–20%.

Two centrifuge modeling tests were performed in this study to evaluate liquefaction behaviors of a gravel-sand mixture comprised of 50% gravel and 50% sand by weight. The tests were conducted under the centrifugal acceleration of 50 g to simulate a prototype soil profile height of 7.6 m. The models were shaken using 1-Hz shaking motions with the amplitude of about 0.19 g and 0.40 g. The paper analyzed the dynamic response and liquefaction behavior of these models based on observations of pore pressure development, stress–strain behaviors, and acceleration response spectra. For the high-amplitude shaking test, liquefaction occurred in most soil layers in the model but for the low-amplitude shaking test, only the surface layer was liquefied. Dilation behavior was observed at different stages of liquefaction depending on the amplitude of shaking and effective stress. Pore water dissipation occurred rapidly during the lower amplitude shaking event caused an increase in the soil stiffness. Liquefaction was also assessed from the amplification of acceleration response compared with the base shaking acceleration. Amplification of the accelerations was found for the non-liquefied soil layers while de-amplification of the accelerations was observed for the liquefied soil layers due to a reduction in soil stiffness.

Geotechnical centrifuge modeling is a common tool that provides insight into the liquefaction phenomena and its associated consequences on buildings. Most prior experiments that aimed to evaluate an isolated structure’s response had one or more model buildings present in the container at a center-to-center spacing ranging from about 2W to 4.6W (where W is the foundation width). This paper presents the results of two centrifuge experiments to evaluate the influence of container boundaries and possible interaction with other building models in a flexible-shear-beam (FSB) container. The first test involved one structure in the center of the container with no other buildings present. The second test included two similar structural models inside the container with a spacing of 3.5W. In parallel, fully-coupled, 3D, nonlinear numerical simulations of the same soil profile and structures were performed in OpenSees with two structures at different spacings and with different domain sizes. The structures represented the key dynamic properties of a prototype 3-story, potentially inelastic, multi-degree-of-freedom (MDOF) building on a mat foundation. The experimental and numerical results indicate that the presence of another structure can have a substantial influence on the building’s permanent settlement and rotation even with a separation distance exceeding 3.5W. In the numerical analyses, a smaller domain size was observed to reduce foundation settlements by up to 18%. The important influence of interaction with container boundaries and other model structures needs to be considered in the design of centrifuge experiments that are used in model validation related to soil liquefaction and its consequences.

The standard penetration test (SPT) has been used to assess the triggering of seismic soil liquefaction since the early 1970s. The currently available liquefaction case history database is updated and extended with the case histories from recent earthquake events. An updated database, which consists of 405 case histories from several recent major earthquake events (e.g., 1999 Chi-Chi, 2008 Achaia-Ilia, 2010 El-Mayor, 2011 Van, 2011 Tohoku, 2011 Christchurch, 2012 Emilia-Romagna, 2016 Kaikōura, 2018 Jia Sian, etc.) was compiled. This new SPT-based field case history database consists of (1) 405 case histories from (2) 33 new earthquake events, (3) with different faulting mechanisms including strike-slip, normal, reverse, and subduction earthquake events, and introduced (4) new event parameters (e.g., R_rup, R_jb, z_tor, etc.), (5) gravelly and silty critical layers with the introduction of new correction terms (e.g., gravel correction), (6) fully digitized borehole information, GPS coordinates, and comparative assessment of new screening criteria with the nearby CPT and V_s data, (7) site response and deconvolution analyses at strong ground motion liquefaction sites to estimate CSR, (8) new parameters related to ground motion and site information (e.g., event type, rupture distance, V_s30m, etc.), (9) a description of geological settings, and (10) new stress (C_N), energy (C_E), and rod length (C_R) correction terms. Within the confines of this manuscript, this database compilation and processing details will be presented. The resulting database is to be used to develop new probability-based liquefaction triggering relationships.

The small-strain shear wave velocity (V_s) is a means to assess the triggering of seismic soil liquefaction since the early 1990s, and the size and quality of these data sets have grown enormously in the past decades. Based on these data, researchers from 1991 to the present have developed V_s-based seismic soil liquefaction triggering relationships. The authors revisited the V_s-based database to update the case histories with the current state of knowledge and include new case histories (e.g., 2011 Tohoku earthquake, 2010–2011 New Zealand-Canterbury earthquakes, etc.). This paper presents the updated V_s-based database, along with the details and statistics of the case history database. The updated database consists of (1) 537 case histories, (2) new earthquake events, (3) multiple inversion method, (4) assessment of nearby standard penetration test (SPT) and cone penetration test (CPT) data, (5) dispersion curves, (6) multiple shear wave velocity profiles, (7) digitized V_s profiles of the literature case histories, (8) implementation of the improved selection of unit weight, (9) new parameters related to site information (e.g., V_s30m, etc.), (10) standard protocol to process data in an unbiased manner, (11) uncertainties of each input parameter, and (12) and geological site classification. Every input parameter was revisited, reanalyzed, and updated. The new database is organized to develop new probabilistic shear wave velocity-based seismic soil liquefaction triggering relationships using Bayesian analysis and system reliability methods.

This paper presents numerical predictions for a dynamic centrifuge test of a submerged cantilevered sheet-pile wall retaining a liquefiable backfill. The numerical analysis was performed using PM4sand model in FLAC2D. The PM4sand model was calibrated for a liquefaction strength based on cyclic torsional shear tests, while the modulus reduction at larger shear strains (γ > 1%) was calibrated based on an empirical G/G_max curve. The wall rotation was driven by shear failure in the backfill due to excess pore pressure buildup. The use of relative density (D_r) estimated from measured cone penetration resistance over D_r from mass and volume measurements resulted in a better prediction of liquefaction triggering and wall rotation. There was a further improvement in the predicted wall rotation when the degradation of elastic shear modulus at large shear strains fitted the empirical curve. However, the post-liquefaction backfill settlement could not be predicted accurately due to limitation of the PM4sand model.

Soils and structures can undergo inelastic demands during an earthquake event; thus soil-structure interaction (SSI) effects are of interest for the seismic analysis and design of tall buildings on shallow foundations. Oversimplifying soil and structural modeling using linear-elastic approaches introduces variability and biases in the computed seismic response of buildings. Engineering demand parameters (EDPs) from coupled SSI systems can only be realistically determined when nonlinearities in the constitutive soil and structural behaviors are accounted for explicitly in the numerical formulation. The objective of this paper is to evaluate numerically the interaction of a nonlinear soil-structure system using a direct fully-coupled approach. Nonlinear-inelastic numerical analyses are conducted on an archetype 30-story building which is supported on a mat foundation modeled using nonlinear link elements to control stiffness and strength. Large discrepancies occur between linear and nonlinear-inelastic tall building modeling approaches mainly in terms of structural demands (i.e., horizontal displacements, accelerations, and drifts), foundation rotation, and soil settlements. The nonlinear-inelastic analyses show a significant decrease of the seismic demands when compared to those computed using linear-elastic SSI models. More realistic computed responses are obtained when nonlinear-degrading building models including SSI effects are used since the energy distribution and tradeoff among both supporting soils and structure vary significantly as a function of the seismic demands.

Seismic protection of buildings using the innovative concept of Geotechnical Seismic Isolation (GSI) has emerged as a sustainable and economical alternative to the conventional base isolation system. The GSI system comprises horizontal layers of high damping, adequate stiffness, energy-absorbing material sandwiched between the natural soil and the building foundation. The GSI layer enables the dissipation of the incoming seismic waves, thereby minimizing the transmission of seismic energy to the building structure. The present study aims to experimentally investigate the performance of a scaled model framed structure placed on a well-designed GSI system comprising of sand-rubber mixture, using laboratory shake table studies. A 5-storey scaled model framed structure is placed on the GSI system in the middle of a sand bed inside a laminar shear box and subjected to seismic excitations. The lateral displacement of the model structure resting on the GSI layer was substantially reduced by 30% at fifth floor level compared to that of pure sand condition without GSI. Overall, the seismic isolation capability of the GSI system was found to be effective for mid-rise framed structures in terms of reduced acceleration and displacement response at different floor levels of the building.

The hazard and increased risk associated with slope failures in the natural habitat are attributed to uncertainty in soil parameters. These soil parameters, that is, cohesion, internal friction angle, and shear modulus, are estimated using the back-analysis method. The method incorporates machine learning algorithms such as particle swarm optimization and support vector machine. However, to capture the uncertainties in the soil parameters, probabilistic analysis is required. This study implements support vector machine for estimating soil parameters as the function of displacement in the soil. The Bayesian method is used to account for uncertainty in soil parameters. The Noto Hanto earthquake in 2007 and the consequent slope failure at Noto Yuryo Road, Japan, is considered as the case study for the proposed model. The finite-element method is used to simulate this slope failure. The soil parameters are treated as random variables to account for uncertainties in these parameters. The predicted displacement is comparable with the measured displacement in the field, which validates the application of the proposed model. The proposed method can efficiently predict experiment soil parameters by capturing uncertainty in soil parameters through a probabilistic approach.

Kappa (κ_r), the high-frequency spectral decay parameter, has been gaining popularity in the engineering seismology field for more than forty years, but it was not until recently that κ_r has been used for geotechnical earthquake engineering applications. For instance, κ_r has been used in site-specific seismic hazard analysis and site response analysis. Values of κ_r capture high-frequency attenuation at short rupture distances. However, the high variability and uncertainty associated with its calculation has hindered its application more broadly in geotechnical engineering analyses. The uncertainties in κ_r may stem from either the poor understanding of the physics behind this parameter or the oversimplified computation procedure. Variability due to the computation procedure can be minimized with the implementation of a standardized and robust calculation process. In this work, we evaluate the variability in κ_r introduced during the calculation procedure by the selection of the frequency band and discuss potential causes for negative κ_r values. We note that the classic κ_r model may be an oversimplification of complex wave propagation phenomena, and the divergence between its assumptions and actual site conditions require further investigation.

This study evaluates the seismically induced displacements of a slope using the Finite-Element Method (FEM) in comparison to the results of twelve empirical predictive approaches. First, a model slope previously studied at the laboratory scale is selected and scaled up to prototype dimensions. Then, the slope is subjected to 88 different input motions, and the seismic displacements obtained from the numerical and empirical approaches are compared statistically. The results show that overall the FEM displacements are generally in agreement with two numerically developed relationships presented by Fotopoulou and Pitilakis (2015), the Newmark-type approach Makdisi and Seed (1978), and the Bray and Travasarou (2007) for rigid slopes. Finally, from correlation analyses between seven ground motion parameters and the FEM numerical results, new predictive equations for seismic slope displacements are proposed as a function of peak ground acceleration (PGA), Arias intensity (I_a), and yield acceleration ratio (A_y/PGA). These functions are expected to be valid for granular slopes built on a rigid base and with low fundamental periods (T_s < 0.2).

A series of Resonant Column (RC) tests in the low-shear-strain amplitude range were performed to investigate the behavior of frictional soils under thermally controlled cyclic torsional loading. An upgraded version of an existing RC apparatus was developed and calibrated to observe the variation of small-strain shear moduli (G_max) and hence resonant frequencies of the test samples under a range of isotropic confinement pressures and various ambient temperatures. The tests were performed under undrained (constant-water content) conditions on statically compacted samples of silt (ML) and clayey sand (SC). Results show that while the silty samples did not experience a significant change in stiffness with increasing temperature, the dynamic behavior of clayey sand samples was largely affected by induced heat ranging between 20°C and 60°C (68°F and 140°F).

Regional-scale liquefaction hazard analyses are necessary for resilience planning and prioritization of seismic upgrades for critical distributed infrastructure such as levees, pipelines, roadways, and electrical transmission facilities. Two approaches are often considered for liquefaction hazard analysis of distributed infrastructure: (1) conventional, site-specific probe or borehole-based analyses, which do not quantify the uncertainty between investigation locations; or (2) surface geology-based analyses, which often neglect localized geotechnical properties and include a great amount of uncertainty. We describe an analytical method to unify the disparate site-specific and deposit-scale approaches using Gaussian processes. We use borehole data to produce spatial fields of random variables for liquefaction triggering analyses, such as groundwater elevation, soil texture classification, penetration resistance, and cyclic resistance ratio that converge to the site-specific uncertainty at sampling locations but also quantify the uncertainty in-between sampling locations. We demonstrate the effectiveness of Gaussian process models for regional-scale liquefaction hazard analyses in two example studies in Washington state and California, US.

Historic earthquake catalogs are, in many regions, insufficient to constrain seismic source locations and magnitude–frequency relations, which are needed for seismic-hazard analyses. As a result, analyses of relic coseismic evidence, such as landslides, rockfall, and liquefaction, must often be used to infer information about the seismic hazard. However, while such studies are performed widely, they have tended to focus more on field identification, dating, and ascription of evidence to a seismic cause, with less effort focused on advancing the techniques for inverse-analyzing field evidence to elucidate the seismic-source model. Accordingly, this paper proposes a general inversion framework by which seismic source parameters are probabilistically constrained from paleoseismic evidence. Analyzing evidence at regional scale leads to (1) a geospatial likelihood surface that constrains the causative rupture location; and (2) a probability distribution of the rupture magnitude, each being direct inputs to probabilistic seismic hazard analyses. Simulated paleoseismic studies are performed on modern earthquakes with known seismic parameters. These simulations demonstrate the utility and efficacy of the proposed framework, which has the potential to provide new insights in enigmatic seismic zones worldwide.

Material damping is attributed to energy loss in a soil mass subject to cyclic loadings, such as that generated by traffic loads, earthquake events, or vibration due to construction activities. It can be calculated based on laboratory testing using, for instance, resonant column and cyclic simple shear devices. Regardless of the measurement and testing method, the damping ratio values are expected to be identical; however, experimentally, it is challenging to obtain a unique damping ratio for a given soil. This work presents the results from thermo-controlled resonant column (RC) tests conducted on statically compacted samples of silt (ML) and clayey sand (SC) to investigate damping properties of frictional soils under controlled moisture (constant-water), confinement, and ambient temperatures, up to 60°C (140°F). Damping ratios were assessed via frequency response curves and logarithmic free-vibration decay curves. The results provide preliminary yet valuable insights into the critical effect that rising temperatures might have on the damping properties of compacted frictional soils as evaluated via resonant column testing.

This study presents a laboratory investigation of the monotonic, cyclic, and post-cyclic responses of a lightly overconsolidated, low plasticity silt deposit conducted to support the geotechnical design of a proposed bridge replacement crossing the Willamette River in Corvallis, OR. The design seismic hazard corresponded to the 975-year return period with the Cascadia Subduction Zone contributing the greatest portion of the hazard. The response of the intact, natural specimens was compared to that of specimens reconstituted from the same material for comparison of the effect of soil fabric. Constant-volume cyclic stress controlled direct simple shear tests (CDSS) conducted on the low plasticity silt deposit showed cyclic mobility type behavior and increases in cyclic resistance with OCR. The exponent of the power relationship between cyclic resistance ratio (CRR) and the number of cycles, N, was shown to be smaller than that commonly assumed within the simplified method for cyclic softening of fine-grained plastic soil. Despite higher density, the reconstituted specimens exhibited approximately 16% lower cyclic resistance than their undisturbed counterparts, indicating the importance of soil fabric on the cyclic resistance of natural silt soils. The post-cyclic volumetric strain of the silt deposit was found to be independent of OCR and increased with the maximum excess pore pressure ratio generated during the cyclic tests.

This paper investigates and presents the numerical modeling and validation of the response of a uniform clean sand using monotonic and cyclic laboratory tests as well as a centrifuge model test comprised of a submerged slope. The dynamic response of the sand is modeled using a critical state compatible, stress ratio-based, bounding surface plasticity constitutive model (PM4Sand), implemented in the commercial finite-difference platform FLAC, and PM4Sand’s performance is evaluated against a comprehensive testing program comprised of laboratory data and a well-instrumented centrifuge model test. Three different calibrations informed by the lab and centrifuge data are performed and the goodness of the predictions is discussed. Conclusions are drawn with regards to the performance of the simulations against the laboratory and centrifuge data, and recommendations about the calibration of the model are provided.

Regional-scale predictions of soil liquefaction are useful, both prior to an event for policy and planning, and immediately after for response and recovery. Such predictions could ideally be made: (1) rapidly, (2) at high resolution, and (3) over the regional scope of cities and transportation networks. Given the growth of community geotechnical data, remote sensing, and algorithmic learning, the existence of such a model is conceivable. Towards that end, interest in “geospatial” models has recently grown. In lieu of directly measuring below-ground traits, as is traditionally done by liquefaction models, geospatial models infer them from above-ground parameters. Field tests of such models have demonstrated both their provocative potential and significant room for improvement. Informed by these tests, this paper develops a geospatial modelling framework driven by algorithmic learning (benefiting from machine- and deep-learning insights, or ML/DL) but pinned to a physical framework (benefiting from mechanics and the knowledge of regression modelers). In effect, subsurface geotechnical test data are predicted remotely and then input to a well-known mechanistic framework for probabilistically predicting ground failure. This has three advantages: (1) a mechanistic underpinning; (2) a significantly larger training set, with the model trained on in situ test data, rather than on ground failures; and (3) insights from ML/DL, with greater potential for geospatial data to be exploited. While liquefaction is a physical phenomenon best predicted by mechanics, subsurface traits lack theoretical links to above-ground parameters, but surely correlate in complex, interconnected ways—a prime problem for ML/DL. To demonstrate, a preliminary model is developed from a modest dataset, is tested on recent earthquakes, and is shown to provide efficient predictions. Ultimately, this approach could be used to develop national and global geospatial models that provide improved regional-scale predictions of liquefaction.

Liquefaction-induced lateral spreading remains a remarkable threat to civil infrastructure in earthquake-prone regions. Despite recent advances, common predictive models of lateral spreading are often associated with large uncertainties. The effects of the depositional setting and age have long been recognized, but not quantified or incorporated into state-of-practice approaches. Specifically, the influence of the relative age of the soil deposits on predicted lateral deformations in riverine environments have not been studied. Thus, this study uses liquefaction-induced lateral spreading observations from the 2010–2011 Canterbury Earthquake Sequence in New Zealand to assess the spatial distribution of the deformations and their relationship with the depositional settings. Observed deformations from active, younger fluvial deposits are compared to those from inactive, older fluvial settings to assess the effect of the relative age of soil deposits and proximity to an active channel. A comparison of the spatial distribution of the observed lateral spreading versus predicted values is presented using the Youd et al. 2002 model. Results from this study suggest that there are quantifiable differences between lateral spreading near active versus abandoned channels, and capturing this difference is important for understanding the influence of depositional environment, sediment age, and for improving predictive models of lateral spreading.

Microbial induced carbonate precipitation (MICP) has gained popularity in the last decade as a biologically based ground improvement technique because it can improve the mechanical behavior of sandy soils. Previous studies of the behavior of MICP-treated sand subjected to cyclic loading have focused on liquefaction mitigation effects, while changes in the improved site’s dynamic response have received rather limited attention. We evaluate MICP treatment approaches for sandy soil considering the need to mitigate liquefaction triggering and the potential for ground motion amplification due to changes in the soil’s engineering behavior. The absence of strain-dependent shear modulus and damping ratio characterization for MICP-treated soils represents a major challenge when investigating potential site effects. We assumed modulus reduction and damping (MRD) curves for MICP-treated soils from the literature based on similarities in initial shear modulus and cyclic stress response. One dimensional, equivalent-linear site response analyses are performed at the Treasure Island site in the San Francisco Bay area, which liquefied in the 1989 Loma Prieta earthquake. Untreated and MICP-treated soils are considered, and their responses compared. The outcropping rock ground motions recorded from the 1989 Loma Prieta earthquake at two nearby stations were selected as input for the numerical analyses. In addition, the effect of MICP on the liquefaction resistance of the profile was considered as a design objective. The evaluation of treatment approaches included the level of cementation and targeted treatment layers as the main parameters. Treatment recommendations that account for the simultaneous mitigation of liquefaction triggering and potential for ground motion amplification at the MICP-treated site are provided.

Dense granular columns (DGC) have become a common soil improvement strategy for embankment structures founded on liquefiable deposits. However, the state-of-practice for the design of DGCs is still limited to simplified methods where the influence of key mitigation mechanisms on the likelihood of triggering is considered in a decoupled manner. Further, the effects of soil-column-embankment interaction, performance, site characteristics, layer-to-layer interaction, and ground motion’s evolutionary characteristics are not included in current engineering design procedures. In this work, we present preliminary results from a numerical parametric study, previously validated against centrifuge tests, to help evaluate the seismic performance of embankments on liquefiable deposits treated with DGCs. We focus on engineering demand parameters that control the embankment design and performance. These analyses are intended to help identify the key predictors of the embankment’s seismic response and the underlying trends. These results set the stage for the development of future design procedures for DGCs near embankment structures.

The primary basis of the empirical methods for estimating post-liquefaction ground settlement is the laboratory data presented in Ishihara and Yoshimine (1992). These data are from one series of cyclic simple shear tests performed on one uniform clean sand reconstituted to three relative densities and tested at one effective confining stress. It is not clear if these data are applicable to other clean sands with other gradations, nonplastic silty sands, and nonplastic silts. A comprehensive database of post-liquefaction volumetric strain test results on nine additional clean sands, two gravels, three silty sands, and five silts is compiled to examine trends over a wider range of soils. The general trends of the larger database of clean sand test data provide the basis for a new relationship between post-liquefaction volumetric strain and the cyclic-induced maximum shear strain for clean sand. Relationships are then extended to nonplastic silty sand and nonplastic silt using relative density to characterize the volumetric strain potential of clean sand and nonplastic silty sand and silt.

Estimation of the seismic performance of bridge embankments is an important application of advanced soil constitutive models to evaluate the potential damage to the bridge systems caused by earthquake induced liquefaction. The study presented in this paper revisits a typical highway bridge embankment using the newly implemented PM4Sand and PM4Silt constitutive models in OpenSees to study the efficiency of various Intensity Measures (IMs). This study follows the Pacific Earthquake Engineering Research Center (PEER)’s probabilistic framework for Performance Based Earthquake Engineering (PBEE) to evaluate the risk associated with earthquake shaking at this PEER testbed. Four different hazard levels of near-fault motions are considered and used in OpenSees simulations. Besides record-to-record uncertainty, spatial variability is also considered. Using OpenSees simulations, the relative efficiency of several IMs, including PGA, PGV, CAV₅, and magnitude corrected PGA, is investigated to shed lights on reducing demand parameter uncertainty. Efficiency of IMs was examined, and the results show CAV₅ is the most efficient IM in predicting liquefaction induced lateral displacements in the studied case.

Liquefaction ejecta were a key mechanism of liquefaction-induced land damage and residential house damage during the 2010–2011 Canterbury earthquake sequence. To gain insight, 244 well-documented liquefaction ejecta case histories of ejecta occurrence, its quantity, and its effects on infrastructure were developed. The authors take advantage of a comprehensive dataset of thousands of CPTs and boreholes, LiDAR surveys, aerial photographs, ground surveys, and liquefaction land damage documentation from insurance claims. The ejecta database includes 61 sites that underwent four major earthquakes that produced varying degrees of liquefaction-induced land damage ranging from no ejecta to extreme ejecta. Liquefaction ejecta coverage and amounts for each of the four primary earthquakes of the Canterbury sequence were extracted using both LiDAR-based and photographs-based approaches because direct measurements of the ejecta-induced settlement were not available. The ground conditions and seismic demand leading to the differing quantities of ejecta-induced settlement during the Canterbury earthquakes were characterized. The database will hopefully lead to the development of methods that estimate the likelihood of liquefaction ejecta and the amount of ejecta-induced ground settlement at a site.

Rayleigh damping is widely used in time-domain seismic site response and soil-structure interaction analyses. The stiffness-proportional part in Rayleigh damping is important to reduce high-frequency noises physically and numerically. The main drawback of Rayleigh damping is that the allowable numerical time step is drastically reduced in time-domain analyses, leading to a significantly higher calculation cost. For example, the calculation time using stiffness-proportional Rayleigh damping can be up to several weeks or even longer and can thus be less practical for routine applications to large models with many elements and/or with materials in high contrast of moduli. Maxwell damping is an alternative scheme that employs multiple Maxwell components in parallel to the constitutive model. With a proper choice of parameters for the Maxwell components, the damping ratio can be made approximately constant over a target frequency range. Maxwell damping is a promising tool for overcoming the two essential shortcomings of Rayleigh damping, namely, numerical inefficiency for large models and over-damping out of the frequency range but under-damping in the range. General guidelines on the application of Maxwell damping in geotechnical earthquake engineering, including parameter calibration, are presented in this paper. Several application examples of Maxwell damping in time domain, including seismic site response and soil-structure interaction analyses are illustrated. Numerical efficiency by Maxwell damping is discussed and compared with that by Rayleigh damping.

The degree of saturation of the soil could affect its shear and compressive strength under static conditions. Under dynamic loading, it is possible to observe changes in behavior as a function of effective stress changes due to water content variations. Normally, the fully-saturated condition is considered as the critical shear strength for the design geotechnical structures; nevertheless, this does not necessarily hold true when the dynamic shear strength of unsaturated soil is considered, because the water content affects the transmission of seismic waves through the porous medium and into a structure. Thus, if the same wave amplitude occurs, the dynamic load that reaches a structure could vary. It is important to better understand this behavior so an adequate assessment of the structure during an earthquake is achieved. A series of cyclic triaxial tests with controlled matric suction was conducted to determine Young’s Modulus, Shear Modulus, and Hysteretic Damping for the different degrees of saturation tested.

Correlations relating laboratory measured fines content (FC) from borehole samples with soil behavior type index (I_C) measurements from cone penetration tests (CPTs) have large uncertainties. Improved estimates of FC can be important for evaluating liquefaction resistance for use in simplified liquefaction vulnerability index (LVI) calculations or nonlinear dynamic analyses (NDAs). Application of regression-based correlations can be especially problematic in thinly interlayered soil deposits, where spatial variability of soil behavior is greater and measurements may be unreliable. This study introduces a user-informed approach to developing site-specific CPT-based correlations for FC estimation using accompanying borehole data, including visual classifications and laboratory test results. It uses a percentile matching framework to honor the cumulative distributions of FC and I_C. This approach has the potential to reduce biases related to spatial variability between adjacent CPT-boring pairs, insufficient or non-representative sampling, and model applicability. The approach is evaluated using data from several sites in Christchurch, New Zealand, and shown to generally improve LVI predictions for liquefaction manifestation during the 2010 Darfield and 2011 Christchurch earthquakes.

Owing to the rising environmental concerns towards using non-renewable resources for heat and power production, renewable sources, such as deep geothermal energy, are steadily gaining popularity. It has been observed that the operation of those plants may cause low magnitude (M_l < 2.5) shallow earthquakes in the area surrounding the geothermal facility. In this paper, a systematic framework is proposed to analyse the seismic response of structures under the geothermally induced micro-seismic events based on a one-dimensional soil-structure interaction model. The results includes the comparison of the free-field ground response and the structure response for deep geothermally induced and natural seismic events in the frequency and time domains. The results show that low-rise buildings are more susceptible to damage caused by deep geothermally induced seismic events in comparison to high-rise buildings.

Two centrifuges are to be installed on the 2nd floor of an existing two-story reinforced concrete building. The structural frame and floor along with its mat foundation and supporting soil are modeled using ABAQUS—a multi-purpose 3D finite-element program to study the vibration levels in the structure. In order to select proper concrete and soil material parameters, dynamic field tests utilizing an impact hammer were performed to measure the responses of the floor as well as the ambient vibration levels. The field testing was simulated in the finite-element model and the dynamic material properties were parametrically adjusted to evaluate the analysis responses. One-half of the gross concrete stiffness EI together with a damping ratio of 2% was found to provide a good match to the field measurements. Using the calibrated material parameters from field testing, the centrifuge loadings are then modeled to reasonably predict operational vibration levels. The impact of the dynamic properties of the foundation soil was also considered by varying the soil’s modulus of elasticity and damping ratio in accordance with available subsurface information. It was found that varying the dynamic soil parameters between reasonable upper and lower bounds would yield up to 29% variations in the amplitude of vibration.

A new statistical framework has been recently proposed to account for shear wave velocity (V_s) variability in seismic ground response analyses (GRA). This new framework operates on the cumulative shear wave travel time (tt_S) instead of directly on, V_s which has been hypothesized to allow for better management of subsurface variability. However, this framework has only been implemented in a few case studies, and more validations are needed. In this study, we perform a systematic analysis to assess the influence of two input parameters on tt_S randomization, and consequently, on GRA predictions. Particularly, we assess the influence of material property variability as quantified using the lognormal standard deviation on tt_S(σ_lntts) and the interlayer correlation (ρ). The assessments are conducted at two downhole array sites so that the GRA predictions can be compared to actual ground motion observations. The results show that the recommended σ_lntts values of 0.01−0.02 might underestimate variability, but nevertheless, using values greater than 0.05 might yield unrealistic V_s profiles with excessively high or even negative, V_s which can be mitigated by using higher ρ.

This study attempts to evaluate the seismic hazard for the Jammu region based on a deterministic approach considering two earthquake scenarios using a logic tree framework. The Peak Ground Acceleration (PGA) values at bedrock level are estimated using already defined GMPEs for the Himalayan region by different researchers. The Main Central Thrust (MCT) and Reasi thrust are found to be the most critical capable of generating PGA > 0.8 g. The findings of the study indicate that the PGA at bedrock level for the region ranged from 0.14 g to 0.67 g. The DSHA in terms of bedrock level PGA for 50th and 84th percentile reveals that the maximum hazard level occurs in the western part of the Jammu region. The DSHA map of bedrock PGA for 50th percentile shows that central part is exposed to severe seismic hazard. The predicted PGA values can be used to assess the seismic stability of existing structures and for the design of earthquake-resistant structures in and around the Jammu region.

A new inversion approach for estimating the shear wave motions in an interior domain surrounded by the domain reduction method (DRM) layer from sparsely measured seismic motion data is presented in this paper. We consider a 2D domain truncated by wave-absorbing boundary conditions (WABC), and the DRM is utilized to inject incident waves into the domain. We attempt to identify an effective seismic force at the DRM layer and reconstruct the ground motions in an interior domain. A gradient-based minimization method minimizes a misfit between measured motions induced by targeted effective forces and their estimated counterparts. The numerical results show that targeted ground motions in an interior domain can be reconstructed. To accurately reconstruct the wave responses, a minimum sensor spacing is required, and it clearly depends on the dominant frequency of incident waves.

San Francisco’s Embarcadero Seawall was constructed between 1879 and 1916 by dredging an approximately 100-foot-wide and 30-foot-deep trench through native Young Bay Mud (YBM), and filling it with rock to create a pyramid-shaped dike up to 40 feet tall. Today the Seawall provides flood and wave protection to Downtown San Francisco and stabilizes hundreds of acres of filled land. Characterization of YBM (a very soft to firm estuarine clay deposited since the end of the last glacial period) is important for evaluating the seismic vulnerability of the Seawall. Monotonic and cyclic loading behaviors are characterized from integration of site-specific in situ and laboratory test data, including cone penetration tests, field vane shear tests, suspension logging, and laboratory direct simple shear tests. The site investigation is described and results from in situ and laboratory tests are presented. These data can be especially useful for reliable assessment of YBM behaviors at the bay margins and evaluation of YBM slope instability.

Many transmission towers in mountainous areas are founded on soil slopes. In these cases, the reliability of towers in supporting electricity conductors under seismic events is affected largely by the response of the slopes and soil-structure interactions in addition to the structural performance of the towers. Probabilistic seismic demand models (PSDMs) of transmission towers to reliably associate key engineering demand parameters (EDPs) to intensity measures (IMs) must capture complexities present in the seismic performance of these systems. The performance of PSDMs also depends to a large degree on the choice IMs. Currently, there are no PSDMs for transmission towers on soil slopes and optimal IMs for such systems have not been identified. The objective of this study is to address these gaps. Toward this goal, a nonlinear finite-element model of a coupled tower-soil-foundation (CTSF) system is developed in the OpenSees platform. To capture the earthquake response and sliding displacement of soil slopes, a two-dimensional soil domain is modeled with pressure sensitive soil materials. Nonlinear soil-structure interactions are captured using nonlinear soil springs implemented at the soil-pile interface. Cloud analysis is performed and the developed CTSF system is subjected to a large set of ground motions. During these analyses, the responses of the system are recorded, and a large spectrum of IMs including structure- and non-structure-specific intensity measures are analyzed in terms of efficiency, practicality, and proficiency. In establishing the PSDMs, conventional regression as well as machine learning models are explored for associating EDPs to IMs. Results of this extensive IM analysis indicate that non-structure-specific acceleration-related IMs are more optimal compared to velocity-, displacement-, and time-related IMs.

This paper focuses on characterizing the cyclic behavior of a heavily loaded rocking footing supporting a bridge pier using centrifuge-model scale shake table tests. The intention of the test presented in this paper is to provide a baseline response for a footing that is expected to fail in the mode of rocking while supported on a uniform loose sand deposit. After presenting the details of the experimental setup and instrumentation plan, the results from a cyclic loading experiment are presented. Similar to the majority of tests in the FoRDy database, the footings investigated in this study were heavily loaded and experienced overturning failure.

A new conditional ground-motion model (CGMM) and a set of scenario-based models for estimating cumulative absolute velocity (CAV) for earthquakes in shallow crustal tectonic settings are derived in this study. Random-effects regressions are performed to develop the CGMM, with random effects across different earthquakes. By combining the CAV CGMM with ground-motion models (GMMs) in shallow crustal earthquake zones for PGA, new scenario-based models are developed for estimating the median CAV and its standard deviation, directly from an earthquake scenario and site conditions. A scenario-based CAV model captures inherently the complex ground-motion scaling effects included in the GMMs for spectral accelerations on which it is based on, such as, sediment-depth effects, soil nonlinearity effects, and regionalization effects. This approach also ensures consistency between the estimated CAV values and a design spectral acceleration response spectrum. Finally, we provide an example for the use of the conditional and scenario-based models to estimate CAV hazard curves, which play an important role in liquefaction engineering.

Engineers often use analytical procedures, which estimate the amount of seismically induced slope displacements (D), to evaluate the seismic performance of earth structures and natural slopes. These procedures often use as inputs slope properties, earthquake parameters, and ground motion intensity measures (IM_s). In this study, we propose a new set of machine learning (ML) based models to estimate D using the NGA-West2 shallow crustal ground motion database. Our findings suggest that the most efficient features to evaluate the seismic performance of slope systems are the slope’s yield coefficient (k_y), its fundamental period (T_s), the earthquake magnitude (M_w), the peak ground velocity (PGV), and the degraded spectral acceleration at 1.3 T_s. We assess the performance of the proposed models by evaluating cross-validation errors, their predictive performance in case histories, and comparisons against existing models. Based on the assessments, we recommend 6 ML-based models to estimate D in engineering practice.

Cumulative absolute velocity (CAV) has recently emerged as a useful intensity measure (IM) for predicting the occurrence of liquefaction and its consequences, including foundation settlement. However, few ground motion models for CAV exist that are applicable in Central and Eastern North America (CENA). The relative paucity of strong motion data for this region and tectonic setting, particularly for large earthquakes and short distances to rupture, is the primary challenge hindering the development of such models. This study applies a Bayesian approach to develop a ground motion model for CAV in CENA. This approach consists of first developing a model using a large database (drawn from the NGA-West2 database), then updating the coefficients in light of observations from a smaller database which is specific to the region of interest (drawn from the NGA-East database). The models developed using the Bayesian approach are compared with using the same functional form in a traditional regression strategy with the NGA-East data, as well as with the model regressed with the NGA-West2 data and with other models in the literature. The Bayesian approach prevents overfitting in the NGA-East data, where few records are available for large magnitude earthquakes at short distances. The use of NGA-West2 data to constrain development of models for CENA follows existing studies that use NGA-West2 models as a baseline and develop adjustments to make the models applicable in a different region and tectonic setting. The Bayesian approach proposed in this study is also applicable for developing other region-specific ground motion models for regions that lack data compared to regions such as California, New Zealand, and Japan that have relatively rich data available.

This study develops site amplification factors for “reference outcrop” site conditions relative to hard rock in the Blue Ridge/Piedmont and Coastal Plain regions of South Carolina. In order to develop the site amplification factors, probabilistic site response analyses were performed considering random (i.e., aleatory) variability and epistemic uncertainty in the subsurface stratigraphy (both material type and thickness of layers), shear-wave velocity profiles, shear-modulus reduction curves, and material damping ratio curves. The results of the probabilistic site response analyses are presented in terms of median site amplification factors and the associated total (i.e., aleatory plus epistemic) standard deviation in natural log units for reference outcrop site conditions for horizontal peak ground acceleration (PGA) and 17 spectral periods. The site amplification factors were used to develop seismic hazard maps for the reference outcrop site conditions. This study is part of an effort to develop statewide seismic ground motion hazard maps for the South Carolina Department of Transportation.

The selection of input motion and modification (spectral matching) technique for generating acceleration-time history for the dynamic analysis of infrastructure systems is a crucial step. In this study, the effects of the type of input motion (synthetic and real) and the spectral matching (time and frequency domain) techniques on the characteristics of modified motion are investigated for selected sites in South Carolina. The site-specific uniform hazard spectra (UHS) were obtained by performing probabilistic seismic hazard analysis for hard rock site conditions using the Central and Eastern United States Seismic Source Characterization (CEUS-SSC) and NGA-East ground motion models. The synthetic motions were generated using the point-source stochastic model of Atkinson and Boore (1995), and real motions were obtained from the PEER database. The study concluded that the modified ground motion characteristics differ significantly between synthetically generated and real ground motions, also time domain and frequency domain matching techniques. Based on the results, it is recommended to use real motions with the time domain matching technique for generating representative ground motions for South Carolina.

Base case, small-strain shear-wave velocity (V_S) profiles, shear-modulus reduction curves, and material damping ratio curves for rock in South Carolina are presented in this paper. The base case V_S profiles are derived from 55 individual profiles compiled from 28 reports by other investigators. Of the 55 profiles, 18 are from predominantly non-foliated crystalline rock, 26 from foliated crystalline rock, and 11 from sedimentary basin rock. The time-averaged, shear-wave velocities in the top 30 m (V_S30) for the base case profiles of these three rock groups are 1,484, 1,183, and 1,518 m/s, respectively. These V_S30 values characterize our base case reference outcrop site conditions in the Blue Ridge and Piedmont provinces. The preliminary shear-modulus reduction and material damping ratio curves presented in this paper are derived by scaling published Tertiary soil curves to fit the data points for Tertiary rock at the Farley Nuclear Plant in Alabama. The results are being used to develop statewide seismic hazard maps for the reference outcrop site conditions for the South Carolina Department of Transportation.

This paper presents the dynamic properties of the Cretaceous and Tertiary sediments in the South Carolina Coastal Plain (SCCP). At many locations in the SCCP, the depth to the top of firm-rock (i.e., small-strain shear-wave velocity, V_S > 760 m/s) is over 150 m, making field exploration to this reference condition often not feasible. Base case V_S profiles are developed using 113 profiles gathered from 65 reports. Of the 113 profiles, 55 extend into the Tertiary above the base of the Santee Limestone, and 70 extend into older, unlithified sediments. The time-averaged V_S in the top 30 m (V_S30) for the base case profiles of the two groups are 354 and 385 m/s, respectively. These V_S30 values characterize our shallower base case reference outcrop conditions in the SCCP. Shear-modulus reduction and material damping curves are based on previous studies, including test results obtained from three recent reports by other investigators. The results are combined with surface contour maps to form a geology-based dynamic property model. The model is being used to develop statewide seismic hazard maps of the reference outcrop conditions for the SC Department of Transportation.

The liquefaction susceptibility of aged soils is an ongoing concern in the Southeastern US due to the recurrence of earthquakes in the South Carolina Coastal Plain (SCCP). This paper presents the results from a laboratory study to assess the cyclic resistance ratio of a Pleistocene-age soil deposit within the SCCP where no evidence of liquefaction or paleo-liquefaction has been observed. The potentially liquefiable deposit studied herein is about 33,000–85,000 years old. Stress-controlled cyclic triaxial tests were performed on three types of specimens from the deposit: specimens that were obtained from fixed piston tube samples and frozen ex situ, specimens that were cored from frozen ground, and specimens that were reconstituted using water pluviation. The range of cyclic stress ratios for the specimens obtained by fixed piston tube sampling and those obtained by coring frozen ground were similar. The reconstituted specimens maintained significantly lower cyclic stress ratios than the cyclic stress ratios of both the in situ and ex situ frozen specimens at initial liquefaction. An aging factor of 1.4 was derived by comparing the cyclic triaxial results from the fixed piston tube specimens and the reconstituted specimens.

This paper presents a study in which five pairs of bedrock ground motion time histories were developed by spectrally matching to a code-compliant target response spectrum determined for a site in Queens, New York City (NYC), within the Stable Continental Region (SCR) of Central and Eastern United States (CEUS). The ground motion time histories were used as input to site response analyses (SRA) performed for the site as part of a companion study. This study was conducted considering the current version of NYC Building Code with a target spectrum defined as the risk-targeted maximum considered earthquake (MCE_R) spectrum per ASCE 7-10 and incorporates suitable approaches for SCRs. The MCE_R spectrum was derived based on a uniform hazard spectrum (UHS) with 2% probability of exceedance in 50 years. This paper addresses the key challenges and suitable approaches for selection and modification of records for bedrock ground motion development in the region.