Earthquake-induced Displacements Research Articles

Directionality of earthquake-induced slope displacements from numerical analysis and sliding block approaches

Earthquake ground shaking intensity differs at different azimuthal orientations (ground motion directionality), which could also result in orientational variations in earthquake-induced slope displacements. Therefore, the range of seismic displacements (e.g., the median and maximum values over all orientations) that may occur by considering the directions of downslope movement and strong shaking is important to evaluate seismic landslide hazard of site-specific slopes. This study performs comprehensive directionality analyses of seismic slope displacement based on two-dimensional numerical and sliding-block approaches. Four slope models with clay and sand soil layers and slope angle of 30° and 40° are analyzed using 75 ground motion records rotated over all orientations. Different sliding-block models are considered, including rigid-block analysis and two coupled flexible-block representations of one-dimensional soil columns with only sliding mass and full site respectively. The results indicate that the orientation variation of slope displacements is much larger than the ground motion parameters. The directionality characteristics of seismic slope displacement from numerical calculation can be well captured by the sliding-block analyses, although significant differences in the computed displacement values are observed. A procedure is proposed to obtain the maximum and median values of seismic slope displacement over all orientations from advanced numerical analysis at low computational cost.

Research on the interaction between trench material and pipeline under fault displacement

With the large-scale construction of oil and gas pipelines, the safety issues of long-distance buried pipelines in the service and construction have become increasingly prominent. The complex geological and topographical conditions of the special zone will put forwards extremely high requirements on pipe trench laying backfill materials and construction technology. For example, pipelines are inevitable to cross the active fault, while the trench backfilled with soil has limitations in protecting them from failure under the active fault displacement caused by the earthquake. Therefore, it is necessary to study the pipe–soil interaction mechanism, determine the stress state of the pipeline and propose a new backfilling material that can protect the pipeline from failure. Foam concrete (FC) provides a new choice to backfill the buried pipeline trench due to its high-homogeneity, lightweight, controllable-strength, and self-compacting. To further determine the applicability of the FC, the pipe-FC interaction mechanism is studied. Then, a FE model of the FC-pipeline-soil interaction system is established by Abaqus to quantitatively analyze the applicability of the FC based on the experimental data of the mechanical performance of the FC. It proves that using FC as trench backfill material has a noticeable protective effect on the pipeline under the earthquake-induced displacement of the normal fault. Furthermore, FC has a better protective effect on the pipeline subjected to compressive than tensile. Therefore, the reference for applying FC in trench backfilling of pipelines crossing normal fault is provided.

An Improved Method for Estimating Earthquake-Induced Permanent Displacement of Bedding Rock Slopes

An Improved Method for Estimating Earthquake-Induced Permanent Displacement of Bedding Rock Slopes

Analysis of Vertical Deformation and Potential Formation of New Faults Cause by Earthquake Using the DInSAR Method (Case Study: 2022 Cianjur Earthquake)

In this study, we focus on the repetitive nature of earthquakes along known fault lines and their potential to create new fault segments. Our primary aim is to enhance our understanding of fault patterns and distribution, facilitating more efficient and accurate earthquake disaster mitigation efforts. Our research specifically targets the vertical deformation resulting from the 2022 Cianjur Earthquake. To achieve this, we employed a sophisticated technique involving data processing from the Sentinel 1A satellites using the Differential Interferometric Synthetic Aperture Radar (DInSAR) method. This method allowed us to derive earthquake-induced displacement values in meters with an impressive level of accuracy, down to the centimeter scale. Our analysis revealed a conspicuous fringe pattern in the interferogram phase data, which did not align with the nearby Cimandiri Fault. This discrepancy led us to suspect the emergence of a new fault or fault segment. By comparing Sentinel 1A satellite images before and after the earthquake, we observed phase differences ranging from -3.112 to 3.117 phases. These recurring phase differences clustered at coordinates 6?48'48" South Latitude and 107?06'05" East Longitude, pinpointing the epicenter of the Cianjur earthquake on November 21, 2022. Furthermore, we calculated line-of-sight (LoS) displacement values ranging from 0 to minus 102 millimeters, indicating vertical subsidence in the vicinity of the 2022 Cianjur earthquake. In conclusion, our research underscores the utility of the DInSAR method for assessing Earth's surface deformation patterns, making it a valuable tool for various earthquake-related analyses.

Numerical seismic analysis of high-piled wharf strengthened with CFRP

High-piled wharves are widely employed in coastal areas, but their vulnerability to earthquake damage necessitates effective strengthening measures. This research focuses on investigating the effectiveness of carbon fiber reinforced polymer (CFRP) laminates in enhancing the seismic resistance of high-piled wharves. Full-scale 3D numerical high-piled wharves, divided into As-built groups and Retrofit groups, were established herein. During modeling, the concrete damage plasticity model (CDP) and the finite-infinite coupling element were contemplated. Two representative ground motions, i.e., the EI Centro wave and the Northridge wave, with peak accelerations of 0.2g and 0.4g, respectively, were utilized to simulate different earthquake scenarios. The responses of the resulting earthquake-induced deck displacement, pile distortion, and pile bending moment profile were explored. The computational analysis revealed significant improvements in the seismic performance of the retrofitted wharves compared to the as-built structures, proving that the externally bonded CFRP method was of great significance in improving overall structural seismic performance. Notably, the retrofitted wharf exhibited reduced deck displacement and remarkable decreases in pile deformation and bending moment. The modeling and analysis techniques can be applied to general wharves or other buildings strengthened with CFRP.

Earthquake-induced fracture displacements and transmissivity changes in a 3D fracture network of crystalline rock for spent nuclear fuel disposal

Earthquake-induced fracture displacements and transmissivity changes in a 3D fracture network of crystalline rock for spent nuclear fuel disposal

Estimation of the Seismically Induced Residual Drift of Structures from Measured Acceleration

ABSTRACT Estimating the story drift directly from acceleration records is challenging. This paper presents a systematic integration scheme involving the empirical mode decomposition of signals to estimate the earthquake-induced displacement of buildings, including their permanent deformation after an earthquake. A three-phase algorithm is proposed. In phase-1, the displacement waveform without residual displacement is estimated, then in phase-2 the residual deformation is calculated. Combining both phase-1 and phase-2, the displacement waveform is estimated. Three types of acceleration data, namely, shaking table test data, seismic response data for a building, and near-fault ground motion data, were used to validate the proposed method.

Seismic displacement prediction methods, procedure, comparison and application

The methodology in the seismic design of slopes has evolved with technological advancement and the development of geotechnical engineering. Since methods with great limitations such as pseudo-static analysis to rigorous methods that require a lot of information for a better understanding of the behavior of the soil such as the dynamic analysis.
 This article develops the procedure, comparison, and application of methods for estimating seismic displacements, which are the Newmark (1965), Sarma (1975), Makdisi & Seed (1978) and Bray, Macedo & Travasarou (2018). Each of these methods considering the criteria of each one to obtain permanent displacements, such as yield acceleration, degraded period, spectral acceleration, magnitude, etc.
 As an applicative case, a rockfill dam and core central 50 m high placed in sandstone strata and moraine deposits interspersed with shale intrusions is shown, as seismic scenarios the Lima 1974 earthquake, the Attic 2001 earthquake and the earthquake were used. of Pisco 2007, considering both NS and EW directions. Likewise, the response spectrum on the base of the failure surface, resulting from a nonlinear seismic response analysis from 3 columns in the dam, is considered as information. The methods of Newmark (1965), Sarma (1975), Makdisi & Seed (1978), and Bray, Macedo & Travasarou (2018) were applied, obtaining deformation results between 1 to 30 cm that according to their order of magnitude represent a stable condition for the dam.

Influence of the Displacement Predictive Relationships on the Probabilistic Seismic Analysis of Slopes

Seismically induced landslides can often cause severe human and economic losses. Therefore, it is worth assessing the seismic performance of slopes through a reliable quantification of the permanent displacements induced by seismic loading. This paper presents a new semiempirical relationship linking the permanent earthquake-induced displacements of slopes to one or two synthetic ground motion parameters developed considering the Italian seismicity, and a comparison with existing simplified displacement models is illustrated. Once combined with a fully probabilistic approach, these relationships provide a useful tool for practicing engineers and national agencies for a preliminary estimate of the seismic performance of a slope. In this perspective, the predictive capability of different semiempirical relationships is analyzed with reference to the permanent displacements evaluated for the Italian seismicity assimilating the slope to a rigid body and adopting the Newmark integration approach. The consequences of the adoption of these relationships on the results of the probabilistic approach are illustrated in terms of displacement hazard curves and hazard maps for different slope scenarios.

Predictive model for seismic displacements of flexible sliding block subjected to near-fault pulse-like ground motions

A post investigation of landslides induced by strong earthquake events in recent years shows that near-fault pulse-like ground motions have a considerable impact on slopes. Accurate evaluation of the stability of slopes under near-fault earthquakes has become a crucial issue in seismic-prone areas. Permanent displacement is widely recognized as an effective index for evaluating the stability of slope. Based on the coupled analysis, an empirical earthquake-induced permanent displacement prediction model was developed. A displacement database of 318 pulse-like ground motions from 50 earthquake events was established. The proposed predictive model is a function of the maximum seismic coefficient-time history (kmax), maximum velocity coefficient of velocity-time history of the k-time history (kv-max), yield acceleration (ky), and period ratio (ratio of the natural period of the slope to the mean period of input motion, Ts/Tm). The dynamic responses (kmax and kv-max) are represented by two different functions. At small period ratios (Ts/Tm≤1.8), it is a function of peak ground acceleration (PGA), peak ground velocity (PGV) and ky. At large period ratios (Ts/Tm > 1.8), it is a function of PGV, Ts and ky. It successfully captured the velocity pulse and long period characteristics of pulse-like ground motions. Compared to the existing model, it is found that the model is more accurate when considering pulse-like ground motions. This prediction model can be used not only for the preliminary evaluation of slope stability but also for probabilistic seismic demand analysis of flexible slopes considering pulse-like ground motion in near-fault regions.

Analytical method for determining displacement and bending moment of embedded cantilever retaining walls subjected to pseudo-static earthquake accelerations

The performance of embedded cantilever retaining (ECR) walls, such as the diaphragm and sheet-pile walls, is measured by the permanent displacement they experience during an earthquake. In the conventional design methods, the embedment depth is derived by checking the wall's stability against a probable collapse mechanism and applying safety factors. Thereby, these methods are incapable of determining the wall displacement. The present study proposes an analytical method based on the pseudo-static approach for calculating the earthquake-induced permanent displacement of ECR walls in cohesionless soils. A displacement-dependent earth pressure mobilization relationship, where the earth pressure mobilization is a function of the wall displacement, is used to derive the passive resistance on the excavated side of the wall. With increasing earthquake acceleration, active soil pressure on the retained side of the wall increases and drives the wall towards the excavated side, which causes further mobilization of passive earth pressure; thus, the wall stability is maintained. In observations from past experimental studies, the required embedment depth is derived by assuming rigid rotation of the wall about a point near the wall base and balancing the forces and moments acting on the wall. Analytical expressions are provided for determining bending moment distribution along the wall height. The proposed results are compared with those of the available experimental and numerical studies, and they exhibit good agreement, which substantiates the validity of the proposed method. Parametric studies were performed to investigate the influence of soil friction angle, wall roughness, the magnitude of the horizontal and vertical earthquake accelerations on the wall displacement and internal forces of the wall.

Regional-scale assessment of earthquake-induced slope displacement considering uncertainties in subsurface soils and hydrogeological condition

Realistic prediction of coseismic landslides is crucial for the design of civil infrastructures and geotechnical systems in seismically active regions. Coseismic landslides are complicated nonlinear and large-deformation processes triggered by ground shaking. To date, many gaps still remain in the scientific understanding of the landslides, particularly in areas lacking information on the subsurface stratigraphy. Analytical methods for estimating coseismic landslides have been based on highly simplified models, where many key influential factors have been overlooked, leading to large uncertainty in using empirical models for landslide prediction. In addition, more evidence recently underscores the necessity of modeling coupled effects between topography and soil amplification, which gives rise to complex wave propagation patterns due to scattering and diffracting of waves within the low-velocity near-surface layers. Neglecting topographic amplification and soil layers could result in significantly underpredicted regional-scale hazards of landslides. In this study, a regional-scale coseismic landslide simulation is carried out using the integral Spectral Element Method (SEM)-Newmark method for Hong Kong Island to quantify the coupled effect of 3D topography, subsurface soil condition as well as hydrogeological conditions. By leveraging extensive geological borehole data, a rigorous statistical model that characterizes uncertainties associated with subsurface soils is established. Influence of key factors that are not well considered in previous coseismic landslide studies, such as variation in irregular rockhead and spatially distributed shear-wave velocity are quantitatively analyzed. Numerical results demonstrate that by rigorously incorporating multiple sources of subsurface soil uncertainties, the total area of landslides in the study region can increase up to 30% compared with benchmark model as evidenced in the physics-based numerical simulation. These case studies will provide a valuable opportunity to revisit key factors that influence coseismic landslides using measured field data.

Seismic design of geosynthetic-reinforced earth retaining walls following a pseudo-static approach

Geosynthetic-reinforced earth (GRE) retaining walls show a better performance than conventionally-designed walls during destructive earthquakes, due to their capability of redistributing seismic-induced deformations within the reinforced zone. In this paper, a recently-proposed method to design GRE walls is first recalled, where the wall is designed to trigger an internal plastic mechanism in the presence of strong earthquakes. Following a pseudo-static approach, the seismic coefficient k is therefore assumed equal to the internal seismic resistance of the wall k c int. The seismic coefficient is then calibrated against given seismic wall performance, expressed in terms of limit values of earthquake-induced displacements. Permanent displacements are evaluated through empirical relationships that were previously developed on the basis of a parametric integration of an updated Italian seismic database. Effectiveness of the proposed procedure is then demonstrated by assessing, through Finite Difference nonlinear dynamic analyses, the seismic performance of two walls, namely a GRE and a conventional gravity wall, characterised by the same seismic resistance but triggering an internal and external plastic mechanism, respectively. They are both subjected to a real strong motion, capable of activating a plastic mechanism. Results showed that lower permanent displacements are accumulated in the GRE wall where internal mechanisms are triggered.

Exceeding Probability of Earthquake-Induced Dynamic Displacement of Rail Based on Incremental Dynamic Analysis

When an earthquake occurs, it can strongly shake high-speed railway bridges. Consequently, the dynamic displacement of the rail on the bridge may exceed the allowable standard. However, few studies have evaluated the probability of rail displacement exceeding the allowable standard, compared to the rich variety of research on the vulnerability of other components of the high-speed railway track-bridge system or other structures. In this paper, incremental dynamic analysis (IDA) is applied to calculate the exceeding probability of rail displacement under different earthquake excitations. A finite element model (FEM) of a high-speed railway track-bridge system is established, which consists of a finite length CRTS II ballastless track laid on a five-span simply supported girder bridge. Records from five stations in the PEER NGA−West2 strong ground motion dataset are selected as seismic excitation. Based on the simulation, the characteristics of the vertical displacement of the rail under different seismic excitations are investigated, and the probability of the vertical displacement of the rail exceeding the allowable standard is calculated using IDA. The results show that: (1) the vertical displacement of the rail above the abutment is significantly smaller than that above other parts of the bridge; (2) the vertical irregularity of the rail caused by earthquakes has a wavelength close to the length of a simply supported girder; (3) under some excitations, two bumps are observed in the Fourier displacement spectrum in the frequency range of 1.3–2.5 Hz and 10–12 Hz, respectively, which may indicate the resonance of the model to the excitation; and (4) the vertical displacement amplitude probability of the rail exceeding 2 mm is 44%, 89%, and 99% when PGA = 0.01 g, 0.20 g, and 0.40 g, respectively. The exceeding probability of the rail above the mid-span is larger than that above other parts of the bridge. Within the mid-span, the exceeding probability of the rail is the largest above the center of the bridge.

Study on the estimate for seismic response of high-speed railway bridge-track system

In recent years, China’s High-speed railways (HSRs) construction has gradually extended to its western regions. Taking A HSR multi-span (5-span) simply-supported beam bridge-track system as the research object, this paper proposed two new indexes: upper bound used to estimate peak seismic response, and characteristic curve used to estimate residual seismic response. The minimum number of ground motions required for reasonably evaluating the two new indexes was determined. According to the findings, the maximum value of peak seismic response of the high-speed railway track-bridge system has significant discreteness, and the mean value of peak seismic response is significantly less than the maximum value. Therefore, it is not advisable to use the maximum value or the mean value of the peak seismic response as the estimate for seismic design. The upper bound for peak seismic response can be used as an effective estimate for seismic design, and the number of ground motion samples can be set to 20. The residual seismic deformation of bearings is the primary source of the residual seismic response of the HSR bridge-track system and that the post-earthquake maintenance of the bridge-track system should primarily focus on the replacement of bearings as well as the resetting of box girders and tracks. The characteristic curves for residual displacement of rail can effectively evaluate the earthquake-induced residual displacement of the HSR bridge-track system, and the number of ground motion samples can be set as 40.

Earthquake-Induced Permanent Displacements of Landslides in Himalaya Using Simplified Methods and Nonlinear FE Dynamic Analysis

Earthquake-Induced Permanent Displacements of Landslides in Himalaya Using Simplified Methods and Nonlinear FE Dynamic Analysis

Near-real-time detection of co-seismic ionospheric disturbances using machine learning

SUMMARY Tsunamis generated by large earthquake-induced displacements of the ocean floor can lead to tragic consequences for coastal communities. Measurements of co-seismic ionospheric disturbances (CIDs) offer a unique solution to characterize an earthquake’s tsunami potential in near-real-time (NRT) since CIDs can be detected within 15 min of a seismic event. However, the detection of CIDs relies on human experts, which currently prevents the deployment of ionospheric methods in NRT. To address this critical lack of automatic procedure, we designed a machine-learning-based framework to (1) classify ionospheric waveforms into CIDs and noise, (2) pick CID arrival times and (3) associate arrivals across a satellite network in NRT. Machine-learning models (random forests) trained over an extensive ionospheric waveform data set show excellent classification and arrival-time picking performances compared to existing detection procedures, which paves the way for the NRT imaging of surface displacements from the ionosphere.

Earthquake-induced permanent displacements of embedded cantilever retaining walls

Stability analysis of retaining walls in seismic areas is generally performed by calculating a safety factor against a possible mechanism of collapse. However, considering that limit conditions usually occur in some time intervals during an earthquake, a more rational approach consists in assessing the performance of the structure in terms of accumulated permanent displacements. In this context, a novel method is proposed in the present study for predicting the earthquake-induced permanent displacements of embedded cantilever retaining walls, such as diaphragm or sheet-pile walls. This method requires solving a simple motion equation of the structure subjected to the soil–structure contact stresses evaluated using a closed-form solution. Specifically, it is assumed that the wall undergoes a rigid rotation around a point located in its embedded portion. Comparisons are presented with both experimental and numerical results documented in published studies. In all cases considered, a satisfactory agreement is found between these results and those provided by the proposed method. In addition, the method accounts for some features of the seismic behaviour of embedded cantilever retaining structures observed during centrifuge tests. Summarising, the method is reliable, simple to use and requires few conventional parameters as input data. Therefore, it is suitable for routine applications.

Generic Predictive Model of Earthquake-Induced Slope Displacements Derived from Finite-Element Analysis

A generic predictive model of earthquake-induced slope displacement subjected to shallow crustal earthquake events is developed using displacements computed from finite-element (FE) analysis. The maximum displacement on the slope surface at the end of shaking was computed by nonlinear FE simulations for 49 slope models each subjected to 1051 earthquake motions. A unified predictive model of seismic displacement is developed that characterizes the slope in terms of its yield acceleration (ky), the depth of the slip surface relative to the height of the slope (Hratio), and the natural period of the full slope height (Tslope). Across five intensity measures and 10 combinations of intensity measures, peak ground velocity (PGV) is found to be the most efficient parameter for the displacement prediction, leading to significantly smaller aleatory variability. The displacement variability is partitioned into two components: between-slope variability, which represents the variability associated with different slope models, and within-slope variability, which represents the variability due to different input ground motions. The developed generic predictive model can be applied to the probabilistic seismic hazard analysis of slope movements and used for deterministic earthquake scenarios in the design/analysis process.

Displacement based seismic assessment of base restrained retaining walls

The present work deals with assessment of earthquake-induced displacement of the base restrained retaining walls (RW’s). A detailed and rigorous finite element (FE) investigation has been carried out following the shaking table experiments on a scaled-down RW model. The FE simulations were performed by conducting several nonlinear time history analyses on a two-dimensional (2D) plane strain FE model of a prototype RW. The hardening and softening of backfill have been simulated by calibrating the Mohr Coulomb material model against the triaxial test results. Role of different backfill into the seismic performance of base restrained RW has also been investigated. It was observed that the cohesionless backfill has a slight influence on the earthquake induced displacement of base restrained RW’s. Amplification of horizontal acceleration in backfill has been observed with no direct correlation with the applied earthquake excitation. The understanding and findings based on shaking table experiment and FE simulations have been used for development of an analytical model for estimation of earthquake induced displacement of base restrained RW. The validity of proposed analytical model has also been examined against the shaking table experiment and FE simulation results.