Permanent Ground Displacement Research Articles

Reducing shallow foundation rotation due to reverse faulting using predefined shear planes

Permanent ground displacement due to faulting during strong earthquakes threatens the stability of civil structures. To protect surface foundations from faulting, several mitigation techniques have been developed. Owing to the limitations of earlier mitigation strategies for unidentified reverse faulting conditions, this research presents a novel mitigation system, including the installation of sliders beneath the wings of a V-shaped concrete element, to reduce footing rotation. To evaluate the effectiveness of the suggested mitigation strategy, concrete strength tests, a physical centrifuge test and a comprehensive numerical study for different fault locations and dip angles were conducted for the first time. Results demonstrated that the placement of the sliders beneath the V-shaped wings had a significant effect on dissipating the fault dislocation. Compared to the previous mitigation techniques, the proposed system decreased the foundation rotation from a high value (11°) to a low value (3·2°) for the worst-case scenarios. Furthermore, the friction coefficients among sliders and concrete, the concrete wing inclination angle, length and thickness were critical parameters to design the optimum proposed system. In contrast, soil layer thickness and relative density did not significantly affect the footing rotation.

Updated Predictive Models for Permanent Seismic Displacement of Slopes for Greece and Their Effect on Probabilistic Landslide Hazard Assessment

Earthquake-triggered landslides have been widely recognized as a catastrophic hazard in mountainous regions. They may lead to direct consequences, such as property losses and casualties, as well as indirect consequences, such as disruption of the operation of lifeline infrastructures and delays in emergency response actions after earthquakes. Regional landslide hazard assessment is a useful tool to identify areas that are vulnerable to earthquake-induced slope instabilities and design prioritization schemes towards more detailed site-specific slope stability analyses. A widely used method to assess the seismic performance of slopes is by calculating the permanent downslope sliding displacement that is expected during ground shaking. Nathan M. Newmark was the first to propose a method to estimate the permanent displacement of a rigid body sliding on an inclined plane in 1965. The expected permanent displacement for a slope using the sliding block method is implemented by either selecting a suite of representative earthquake ground motions and computing the mean and standard deviation of the displacement or by using analytical equations that correlate the permanent displacement with ground motion intensity measures, the slope’s yield acceleration and seismological characteristics. Increased interest has been observed in the development of such empirical models using strong motion databases over the last decades. It has been almost a decade since the development of the latest empirical model for the prediction of permanent ground displacement for Greece. Since then, a significant amount of strong motion data have been collected. In the present study, several nonlinear regression-based empirical models are developed for the prediction of the permanent seismic displacements of slopes, including various ground motion intensity measures. Moreover, single-hidden layer Artificial Neural Network (ANN) models are developed to demonstrate their capability of simplifying the construction of empirical models. Finally, implementation of the produced modes based on Probabilistic Landslide Hazard Assessment is undertaken, and their effect on the resulting hazard curves is demonstrated and discussed.

Seismic performance and damage control of large-span prestressed concrete rigid-frame bridges with high piers crossing strike-slip faults

Post-earthquake surveys show that fault-crossing simply supported beam bridges or continuous beam bridges suffer from severe seismic damage, such as falling beams and even collapse. Currently, there is a lack of understanding of the seismic performance of fault-crossing prestressed concrete rigid-frame bridges (PCRFBs). In this study, a representative PCRFB was used as a case study, and typical strike-slip fault cases were discussed, including fault-crossing angles and permanent displacement. The results revealed that different from other bridge structure types, the mid-span section was prone to yield failure because of the significant plastic deformation demands when the fault crossed the middle span. Positive and negative moment failures of the mid-span girder occurred when the fault-crossing angle was greater than or less than 90°, respectively. The fault-crossing angle is an important factor that affects the seismic performance of PCRFBs. A value of 90° is a favorable fault-crossing angle with minimal damage. The deformation demands of the mid-span were larger than the internal force effects when there was an increase in the permanent ground displacement of the fault. The proposed shock-absorbing hinge system (SAHS) can effectively reduce the vertical displacement of the girder and can significantly avoid the occurrence of plastic hinges, so the main girder is protected.

Seismic Fragility Analysis of Retaining Walls Dependent on Initial Conditions

Fragility curves of retaining walls constitute an efficient tool for the estimation of seismic risk and can be utilized for prevention from potential damage or for immediate decision-making. In this work, fragility curves for cantilever retaining walls of three different heights are proposed, considering cohesionless soil materials. The seismic response of the soil-wall system, in terms of permanent vertical ground displacement of the backfill soil and permanent horizontal displacement of the wall’s base, is estimated by conducting non-linear time history analyses, through the 2D finite element simulation method. Five initial conditions are investigated regarding the value of the global factor of safety (FS) under static conditions. An initial value of FS equal to 1.5 is considered for dry conditions. If the presence of the water table is taken into account, the corresponding FS drops to values ranging from 1.4 to 1.1. Parameters that characterize seismic intensity are evaluated based on criteria, in order to identify the intensity measures that best correlate with the system’s response. Three damage states are adopted, corresponding to minor, moderate, and extensive damage. The approach of combined damage criteria is also investigated. Finally, fragility curves are derived demonstrating the degree of dependency on initial conditions.

Effects of fling step on the seismic response of reinforced concrete arch bridges

Many arch bridges have been built in near-fault regions around the world and may be affected by fling step, which is the permanent ground displacement caused by the long-period pulse within the frequency content of an earthquake. This study investigates the effect of fling step on reinforced concrete deck-type arch bridges with short to medium spans. Three-dimensional non-linear models of three existing reinforced concrete arch bridges in Iran, with span lengths of 23, 35 and 60 m, were developed. The structures were subjected to seven near-fault earthquakes in longitudinal and transverse directions, once with the fling-step pulse included and once with it removed. The results showed that fling step has a noticeable effect on the seismic response indicators investigated, but may increase or decrease the seismic demand. The maximum curvature in the presence of fling step in relation to that without fling step ranged between 0.54 and 2.06. Unseating in the longitudinal direction was most sensitive to the fling step, and showed a more than 200% increase in some cases. Effects of the fling step were correlated with the ratio of the period of the fundamental mode of vibration of the structure to that of the fling-step pulse.

A Methodology to Combine Shaking and Ground Failure Models for Forecasting Seismic Damage to Buried Pipeline Networks

ABSTRACT How does an earthquake affect buried pipeline networks? It is well known that the seismic performance of buried pipelines depends on ground failures (GFs) as well as strong ground shaking (SGS), but it is unclear how the various types of earthquake hazards should be collectively combined, as existing methodologies tend to examine each of the earthquake hazards separately. In this article, we develop a probability-based methodology to consistently combine SGS with three types of GF (surface faulting, liquefaction, and landslide) for forecasting seismic damage in buried pipeline networks from a given earthquake rupture scenario. Using a gas transmission pipeline example, we illustrate how the proposed methodology enables others (e.g., researchers, pipeline operators who manage distribution lines, and consultants) to modularly combine various models such as those for estimating probability of GF, permanent ground displacements, and pipeline fragility. Finally, we compare the proposed methodology against the Hazus methodology to explore implications from considering each hazard one at a time.

Effect of blast induced vibration on coal mine overburden dump slope through discrete element method

Blast induced ground vibration (BIGV) is a serious threat for the coal mine overburden (OB) dump slopes. The problem becomes intricate considering heterogeneity of the OB dump materials. The performance of an OB dump slope under BIGV is investigated considering Voronoi tessellation scheme of universal distinct element code (UDEC) for the heterogeneity of the OB materials. Variations of BIGV, expressed in terms of peak particle acceleration, velocity and displacement, with the density of explosive and the distance of OB dump slope from the blasting source are comprehensively reported considering single-benched as well as double-benched OB dump slopes. Nonlinear dynamic analyses are carried out considering the expected BIGV at the base of the OB dump slope and effects of blasting parameters on the performance of the dumps were investigated considering different monitoring points along the surface of the slope. The effects of heterogeneity on the dynamic response of OB dump slopes are also presented in comparison with the homogeneous condition. A comparative study based on the performance of single-benched and double-benched slopes under BIGV is also presented. Finally, the failure state of the OB dumps were inferred from the permanent ground displacement experienced by the slopes considering BIGV. The methodology and the presented results are supposed to be beneficial for the mining authority in framing the safety guidelines for OB dump slopes in coal mines.

Research on Effect Factors of Mechanical Response of Polyethylene Gas Pipeline in Karst Area Based on Element Birth and Death Technique

Abstract Buried gas pipelines in karst area are inevitably affected by the geotechnical activities, which is difficult to resist the permanent ground displacement caused by soil dislocation and surface damage. In this paper, abaqus finite element software has been used to establish a pipe-soil nonlinear coupling model based on element birth and death technique. The influence rules of various sensitive factors on the stress response of gas pipelines are studied. The work presented in this paper can provide a reference for the design and safety of polyethylene gas pipeline crossing the karst area.

Enhanced predictive method for pipeline strain demand subject to permanent ground displacements with internal pressure & temperature: a finite difference approach

Pipelines subject to ground deformations generated by geohazard loads carry high importance on pipeline analysis, design, and assessment due to risk of structural damage or failure. Additionally, internal pressure and temperature variation within an operating pipe induce additional strains in combination with pipe strains generated by ground displacement. In this study, an enhanced predictive method is proposed founded upon methods employed by Zheng et al. (2022) to assess pipeline behaviour subject to permanent ground displacement, while considering effects of internal operating pressure and temperature variation. The finite difference-based method previously proposed for strain analysis of buried steel pipes subject to ground movement ignores the effects of internal pressure and/or temperature loading, limiting the applicability of this approach to exclude the operating conditions of pipelines. To address this limitation, the proposed enhanced method accounts for the initial thermal strains and biaxial stress state in the pipe due to hoop stress generated by internal pressure. These additional strains are considered within the expressions of internal axial force and bending moment, derived based on the actual stress distribution on the pipe cross-section. The accuracy of the proposed method is validated against the finite element method (FEM) with respect to results of strain and deformation demand using several indicative case studies. This research provides an effective method of incorporating temperature and internal pressure loads of pipelines subject to permanent ground displacements of varying types, magnitudes, and directions.

The Effect of Soil Liquefaction and Lateral Spreading to the Seismic Vulnerability of RC Frame Buildings Considering SSI

ABSTRACT Evidence of past earthquakes highlighted the seismic vulnerability to buildings due to soil liquefaction and lateral spreading phenomena. Damage to buildings on a liquefiable site, especially on a gently sloping site, can be severe. The liquefied soil can undergo permanent lateral ground displacements as large as several meters in some cases, which can be severely disastrous to buildings. Recent physical tests and effective stress analyses of nonlinear dynamic soil-structure interaction (SSI) proved that simplified empirical processes are often improper for evaluating liquefaction-induced building settlements. A better understanding of the SSI effects is also essential in cases where the underlying soil is susceptible to liquefaction. In this respect, the interaction of the earthquake excitation and ground failure (i.e. soil liquefaction and lateral spreading) for buildings considering SSI is investigated herein. Typical low-code reinforced concrete (RC) frame buildings of different heights with shallow spread footings on liquefiable level-ground or sloping soils subjected to ground shaking are considered. The direct SSI approach is implemented. Predictive relationships are established between the maximum normalized differential displacements (horizontal or settlement) and the permanent ground displacement (PGD) vector at the level of foundation for low-code RC frame buildings with shallow spread footings on soils with high liquefaction potential subjected to ground shaking. Finally, vulnerability is expressed in terms of fragility and vulnerability curves as well as in terms of fragility surfaces as a function of two intensity measures.

Stress Calculation Method Designed of Pipeline in Landslide Section Based on SBAS-Insar and Finite Element Method

The permanent ground displacement of geological disasters is the main reason inducing large additional axial stress of pipelines. This paper presents a surface displacement measurement method above the pipeline based on SBAS-InSAR remote sensing technology, which realizes millimeter-level high-precision monitoring of surface displacement of pipeline in kilometer range. Based on the spatial coordinate data of the pipeline center line and the geometric feature data of the pipeline, combined with the cubic spline interpolation algorithm, a reconstruction method of the pipeline three-dimensional space routing is proposed. Considering the real routing of the pipeline and the process load conditions such as temperature and pressure, the finite element model of pipeline stress analysis is established by using the space pipe element and the nonlinear pipe soil element. Taking the remote sensing landslide displacement as the accurate boundary condition, the calculation method of pipeline stress in landslide section is proposed. The practice of a high-risk landslide section in Liangxiang-Xishatun of Shaanxi-Beijing Pipeline from 2021 to 2022 shows that the maximum relative error between the pipeline stress results obtained by this method and the distributed strain gauge monitoring results does not exceed 16%, which can effectively realize the spatial reconstruction and safety evaluation of the pipeline stress state in the landslide section, and provide a technical basis for the establishment of digital twins of pipeline safety state in future geological disaster sections.

ANN-Based Assessment of Soft Surface Soil Layers’ Impact on Fault Rupture Propagation and Kinematic Distress of Gas Pipelines

Large-scale lifelines in seismic-prone regions very frequently cross areas that are characterized by active tectonic faulting, as complete avoidance might be techno-economically unfeasible. The resulting Permanent Ground Displacements (PGDs) constitute a major threat to such critical infrastructure. The current study numerically investigates the crucial impact of soil deposits, which usually cover the ruptured bedrock, on the ground displacement profile and the kinematic distress of natural gas pipelines. For this purpose, a decoupled numerical methodology, based on Finite Element Method (FEM), is adopted and a detailed parametric investigation is performed for various fault and soil properties. Moreover, the advanced capabilities of Artificial Neural Networks (ANNs) are utilized, aiming to facilitate the fast and reliable assessment of soil response and pipeline strains due to seismic faulting, replacing time-consuming FEM computations. An extensive sensitivity analysis is performed to select the optimal architecture and training algorithm of the employed ANNs for both the geotechnical and structural parts of the decoupled approach, with suitable input and target values related to bedrock offset, fault and soil properties, surface PGDs, and pipeline strains. The proposed ANN-based approach can be efficiently applied by practice engineers in seismic design and route optimization of natural gas pipelines.

Response of structures to motions with fling step: Does fling matter?

An essential signature of the near-fault motions is the fling-step, which contains a one-sided velocity pulse and ultimately results in permanent ground displacement. It is well-known that the standard processing of ground motion removes such fling. However, some researchers believe that dynamic action is hardly affected by such removal of permanent static displacement. So, such processed motions can be used to examine the effect of fling-step. In the current investigation, two mathematical analogues, rigid sliding and rigid rocking blocks are extensively studied under near-fault motions with fling-step. The response is computed using the processed motions (without explicit fling) and the processed motions with fling mathematically reintroduced. A comparison in response confirms that using motions without explicit fling is essentially deficient from a structural engineering perspective. The study has also noted the peculiarities in the dynamics of rocking oscillators, which may be of significance for assessing the consequences of the sequence of motions.

A finite difference-based approach for strain demand prediction of inelastic pipes subjected to permanent ground displacements

Permanent ground displacement triggered by geohazards constitutes a major threat to the integrity of long-distance pipelines. In this study, a novel and simple method is proposed to evaluate inelastic pipes’ behavior under ground movements considering soil-pipe interaction based on the finite difference method. The existing finite difference-based method previously proposed by the authors for strain analysis of buried pipelines subjected to ground movements excludes material nonlinearity in pipes, which limits its applicability in engineering practice. To remedy this situation, the method presented herein maintains the well-established concepts of the existing finite-difference-based method but also introduces the scheme to consider the inelastic material behavior of steel pipes. More specifically, the expressions of internal axial force and bending moment, required in the finite difference equations, are explicitly derived based on the actual stress distribution on the pipe cross-section. The proposed method is validated against the finite element method (one-dimensional beam model) in terms of the strain and deformation demands using two indicative case studies, referred to as symmetric and non-symmetric soil resistance conditions, respectively. The comparison between finite element analysis and the proposed method indicates good agreement. Additionally, the proposed method is compared with four existing analytical methods for pipes subjected to strike-slip fault displacement. The proposed method is a simple but general technique to analyze pipes’ response under a wide range of geohazards, and thus can be potentially used as an alternative method for preliminary design, safety prescreening, and reliability-based assessment of pipes against geohazards.

Validation of physics‐based regional‐scale ground‐motion simulations of the 2008 Mw 7.9 Wenchuan earthquake for engineering applications

AbstractThe 2008 Mw 7.9 Wenchuan earthquake, one of the largest continental intraplate events instrumentally recorded, struck the central part of Sichuan Province in southwestern China causing great destruction and loss of life but also providing a wealth of seismological data, geodetic measurements, and tectonic observations. The Wenchuan earthquake ruptured two northwest‐dipping imbricate oblique reverse faults along the middle segment of the Longmenshan fault zone—a northeast‐trending thrust belt located at the boundary between the Tibetan Plateau and the Sichuan Basin. In this study, a hybrid approach that combines deterministic modeling at low frequencies with stochastic modeling at high frequencies is used to simulate broadband ground motions at 52 strong‐motion stations and 506 geodetic sites in the vicinity of the causative fault. The low‐frequency components of the synthetic ground motion are simulated using an extended kinematic source model embedded in a layered medium, whereas the high‐frequency components are generated using a stochastic finite‐fault model. The two independently derived ground‐motion components are then combined using matched filtering at a crossover frequency of 0.8 Hz to generate broadband ground‐motion time histories and response spectra. The temporal and spectral characteristics of the synthetic and recorded ground motions at the 52 strong‐motion stations are compared and the effect of soil nonlinearity on the simulated ground motions is investigated through 1‐D nonlinear site response analysis. Finally, the simulated permanent ground displacements at the 506 geodetic sites are evaluated against geodetic observations and the peak amplitudes of the synthetic ground motions at the same locations are compared with predictions of empirical ground‐motion models.

Numerical studies on the seismic responses of precast segmental columns-supported bridge structures subjected to near-fault ground motions

Precast segmental columns have attracted wide attentions in bridge construction industry recently due to its ability to accelerate construction speed, improve construction quality and reduce environmental impact. It is of great practical importance to study the seismic performances of segmental columns, and many experimental and numerical studies have been performed. However, most previous studies focused on segmental column itself, the research on the seismic performance of a whole bridge structure supported by precast segmental columns is very limited. In particular, no systematic studies have been performed to investigate the seismic performances of segmental columns-supported bridges subjected to near-fault (N-F) ground motions (GMs). To bridge this research gap, the seismic responses of three bridge structures (i.e. a segmental columns-supported bridge, a bridge supported by segmental columns with internal energy dissipation bars, and a conventional bridge supported by monolithic columns) subjected to four types of earthquake ground motions (i.e. a N-F GM with fling-step (F-S) effect, a N-F GM with forward-directivity (F-D) effect, a non-pulse-like N-F GM, and a typical far-field (F-F) GM are investigated and compared in the present study based on the validated numerical models developed in ABAQUS. The influences of permanent ground displacement in the F-S ground motion and pulse period are also systematically investigated. The numerical results demonstrate that the permanent ground displacement in the N-F ground motions has very different effects on the segmental-columns supported bridge and monolithic columns supported bridge.

Modeling of non-ductile RC structure under near-fault ground motions: A nonlinear finite element analysis

The old existing reinforced concrete (RC) structures in Taiwan are susceptible to severe damage under earthquakes because of the soft-story mechanism. Moreover, the effects of near-fault ground motions often contain a long period of velocity pulse and permanent ground displacement. This study is based on the tri-axial shaking table test conducted at the National Center for Research on Earthquake Engineering in Taiwan and a series of seismic performance evaluations of a non-ductile RC structure in Taiwan. Finite element analysis (FEA) will be conducted to simulate the linear and nonlinear behavior of the seven-story building. This accommodates the damage plasticity model for concrete and the elastic-perfectly plastic model for reinforcement. Comparison of the results between the experimental test and numerical model showed that the similarity of the vibration period has a great influence on the simulation results. The findings showed that the data of acceleration and displacement behavior corresponded with the experimental results in a satisfactory margin. Also, the damage mode is very similar to the shaking table test results. The study found that using FEA can satisfactorily simulate the seismic performance of mid-rise buildings under a near-fault earthquake.

Regional liquefaction-induced ground displacement predictions for Canada using 5th Generation NBCC Seismic Hazard Model

Significant regions of Canada are seismically active, and areas underlain by loose, saturated sediments in these regions are expected to experience liquefaction-induced lateral spread permanent ground displacements (PGDs) under earthquake shaking. The empirical predictive equations are commonly used for estimating the PGDs especially when detailed numerical analyses are not undertaken. The key input parameters for these equations comprise earthquake magnitude (M) and source distance (R), along with geotechnical and topographic parameters; however, there is ambiguity over choosing appropriate site-specific values of M and R. The current study predicts PGD probabilistic hazard curves that are applicable for locations in southwestern and southeastern regions of Canada using a probabilistic seismic hazard assessment (PSHA) framework. This was achieved by embedding two relevant empirical models for predicting lateral spread PGDs (replacing the ground motion prediction equations) within the 2015 National Building Code of Canada framework that is currently available in OpenQuake platform. Moreover, deaggregation analyses have been performed to understand the M and R contributions from different seismic sources on the predicted site-specific hazard. The developed PGD curves can be readily adopted for estimating site-specific lateral spread PGD demand as input to performance-based design of structures in seismically active areas of Canada.

Seismic performance of a cable-stayed bridge crossing strike-slip faults

Past earthquakes demonstrated the vulnerability of bridges crossing fault ruptures, and this issue has drawn attentions of researchers and engineers. Previous studies on this topic are limited to girder bridges. In this paper, seismic performance of a three-span cable-stayed bridge subjected to strike-slip faults is investigated. Nonlinear time-history analyses are conducted using actual near-fault ground motion records, which are applied to the bridge in both fault-normal and fault-parallel directions. Seismic responses of fault-crossing and near-fault cable-stayed bridges are compared. Effects of permanent ground displacements and fault crossing angles on the response of the fault-crossing bridge are also evaluated. Results show that seismic responses of the fault-crossing bridge are larger than those of the near-fault bridge, especially the girder and bearing displacements. When the fault strike is perpendicular to the longitudinal axis of the bridge, the permanent ground displacement significantly affects the bearing displacement, but has little impact on the responses of pylons and cables. Comparing with other fault crossing angles, the pylon displacement and longitudinal bearing displacement are smaller in the case of 90°, but the transverse bearing displacement is larger.

Fault Displacement Hazard Analysis Based on Probabilistic Seismic Hazard Analysis for Specific Nuclear Sites

Permanent ground displacements/deformations caused by earthquakes can seriously challenge the safety of the nuclear power plants. The state-of-the-art hazard analysis methods provide a fault displacement hazard curve, i.e., the annual probability of given measure of displacement will be exceeded. The evaluation of ground displacement hazard requires great effort, empirical evidence, and sufficient data for the characterization of the fault activity and capability to cause permanent surface displacement. There are practical cases when the fault at the site area revealed to be active, and, despite this, there are no sufficient data for the evaluation of permanent ground displacements hazard and for judging on the safety significance of permanent ground displacement. For these cases, a methodology is proposed that is based on the seismotectonic modelling and results of the probabilistic seismic hazard analysis. The method provides conservative assessment of the annual probability of fault displacement that allows the decision whether permanent displacement hazard is relevant to nuclear power plant safety. The feasibility and applicability of the method is demonstrated for the Paks site, Hungary.