Geotechnical Earthquake Research Articles

Laboratory study on undrained shear behaviour of overconsolidated sand–silt mixtures: effect of the fines content and stress state

The post-liquefaction stability analysis of silty sand soil deposits that are prone to liquefaction becomes a major challenge in Geotechnical Earthquake Engineering. The objective of this laboratory investigation is to study the combined effect of the confining pressure and the low plastic fines (Ip = 5%) on the liquefaction resistance (undrained shear strength) of medium dense (Dr = 52%) overconsolidated sand–silt mixtures under monotonic loading conditions. In this context, a series of undrained monotonic triaxial tests were carried out on reconstituted saturated silty sand samples with fines content ranging from 0 to 40%. The different samples were prepared with dry funnel pluviation technique and subjected to different overconsolidation ratios (OCR = 1, 2 and 4). The results of this laboratory investigation indicate that the influence of low plastic fines on the undrained shear strength (liquefaction resistance) is clearly observed for the lower overconsolidation ratios (OCR = 1 and 2). This effect becomes insignificant for higher overconsolidation ratio (OCR = 4) for both confining pressures under consideration. The obtained data confirm the existence of a linear relationship between the undrained peak shear strength of overconsolidated Chlef sand samples (qpeak_OC) and undrained shear strength of normally consolidated Chlef sand (qpeak_NC) for the two selected confining pressures ( = 100 and 200 kPa) and initial relative density (Dr = 52%) under consideration.

Post-Earthquake Reconnaissance Using Digital Imagery: A Bird’s-Eye View

Over the last decade, remote sensing has played an increasing role in geotechnical earthquake reconnaissance through the use of satellite imagery, LIDAR, and unmanned aerial vehicles (UAVs). These techniques have been used not only to qualitatively document earthquake effects, but also to acquire quantitative information about damage patterns, digital elevation models of failures, and ground movements. Digital imagery obtained from satellites and UAVs provides a bird's-eye view, and thus offers a holistic perspective of the geotechnical effects of an earthquake at both the regional and site scales. Additionally, digital imagery can be integrated with other data within a geospatial framework, which allows researchers to investigate relationships that could not be evaluated otherwise.

50+ Years of Geotechnical Earthquake Engineering — What Have We Learned?

50+ Years of Geotechnical Earthquake Engineering — What Have We Learned?

Remote sensing for geotechnical earthquake reconnaissance

This paper describes recent efforts that incorporate remote sensing techniques and platforms into geotechnical earthquake reconnaissance to document damage patterns, collect three-dimensional geometries of failures, and measure ground movements. The most-commonly used remote sensing techniques in geotechnical engineering (satellite imagery and LIDAR), as well as unmanned aerial vehicles (UAV), are introduced and recent case histories of the use of these techniques in reconnaissance efforts are provided. These examples demonstrate the potential for remote sensing to improve our understanding of geotechnical effects both at a regional scale and at a local level. The use of remote sensing to measure ground movements is particularly noteworthy and has the potential to provide data sets that will improve our ability to quantitatively predict the consequences of liquefaction and landslides. However, to realize this potential, investments must be made in collecting appropriate pre-earthquake data.

Visible Assessment of Earthquake-induced Geotechnical Hazards by Adopting Integrated Geospatial Database in Coastal Facility Areas

Earthquake event keeps increasing every year, and the recent cases of earthquake hazards invoke the necessity of seismic study in Korea, as geotechnical earthquake hazards, such as strong ground motion, liquefaction and landslides, are a significant threat to structures in industrial hub areas including coastal facilities. In this study, systemized framework of integrated assessment of earthquake-induced geotechnical hazard was established using advanced geospatial database. And a visible simulation of the framework was specifically conducted at two coastal facility areas in Incheon. First, the geospatial-grid information in the 3D domain were constructed with geostatistical interpolation method composed of multiple geospatial coverage mapping and 3D integration of geo-layer construction considering spatial outliers and geotechnical uncertainty. Second, the behavior of site-specific seismic responses were assessed by incorporating the depth to bedrock, mean shear wave velocity of the upper 30 m, and characteristic site period based on the geospatial-grid. Third, the normalized correlations between rock-outcrop accelerations and the maximum accelerations of each grid were determined considering the site-specific seismic response characteristics. Fourth, the potential damage due to liquefaction was estimated by combining the geospatial-grid and accelerations correlation grid based on the simplified liquefaction potential index evaluation method.

Geostatistical assessment for the regional zonation of seismic site effects in a coastal urban area using a GIS framework

Earthquake-induced hazards are profoundly affected by site effects related to the amplification of ground motions, which are strongly influenced by local geologic conditions such as soil thickness, bedrock depth, and soil stiffness. Seismic disasters are often more severe over soft soils than over stiff soils or rocks due to differences in local site effects. In this study, on the basis of a geotechnical information system (GTIS) framework, we developed an advanced geostatistical assessment for the regional zonation of seismic site effects. In particular, to reliably predict spatial geotechnical information, we developed a procedural methodology for building an advanced GTIS within a geographic information system framework and applied it to the Busan area in Korea. The systemized GTIS comprised four functional components: database, geostatistical analysis, geotechnical analysis, and visualization. First, to build the GTIS, we collected pre-existing geotechnical data in and around the study area, and then conducted a walk-over site survey to acquire surface geo-knowledge data. Second, we determined the optimum geostatistical estimation method using a cross-validation-based verification test, considering site conditions. The advanced GTIS was used in a practical application to estimate the site effects in the study area. We created seismic zoning maps of geotechnical earthquake parameters, such as the depth to bedrock and the site period, and present them as part of a regional synthetic strategy for earthquake risk assessment.

Integrated system for site-specific earthquake hazard assessment with geotechnical spatial grid information based on GIS

An integrated earthquake hazard assessment system with geotechnical spatial grid information was developed based on a geographic information system (GIS). The developed system, built, within the frame of GIS, consists of a database (DB) containing all available site information and processed data in the standard formats, and system software that performs various functions to manage and utilize the data in the DB. The system software is divided functionally into an input module, a geostatistical three-dimensional integration module, a real-time earthquake hazard assessment module, and an output or visualization module. A systematic framework for construction of a geotechnical spatial grid was developed to consider local site response characteristics for target areas. According to the framework, three interrelated assessment procedures were incorporated into the DB on a real-time basis: real-time seismic load determination, real-time liquefaction hazard estimation, and real-time structure fragility evaluation. The DB and these sub-modules of the system software were combined and integrated into a single system to provide a familiar and user-friendly working environment with a standard interface. In addition, the integrated system was imbedded into the Korea Integrated Seismic System server to be linked with real-time seismic accelerations, and a simulation of the system was specifically conducted at Incheon Port, Korea, using two actual earthquake events (the 2013 Baengnyeong and 2014 Taean earthquakes) and one virtual earthquake scenario. The simulation results were visualized as a geotechnical earthquake hazard map to verify the computer-aided real-time assessment framework at the times, when the three notable earthquake events occurred at the nearby Incheon Port.

The Influence of Seismic Parameters on Site Response

Geotechnical earthquake engineers have been trying to determine the most appropriate solution techniques for ground response analysis under earthquake loadings. This paper presents the importance of the adequate soil behavior model to simulate earthquake site response analysis. The influence of nonlinearity and linearity of soils on the site response is also investigated. Many methods have been proposed for the analysis of one-dimensional ground response such as nonlinear methods and equivalent linear with reduced modulus. Using 13 well known earthquake records and geotechnical information of sand in the Qeshm Island (Iran) and classification of earthquakes based on seismic parameters, the influence of each parameter on the Response spectra and Fourier Spectrum of surface of ground becomes evident. Analysis was done using two softwares; EERA (equivalent linear analysis) and NERA (nonlinear analysis) and compared. Finally, output of the software is compared with the reference result on site.

Assessment of liquefaction potential of Erzincan Province and its vicinity, Turkey

One of the most important causes of damages after the earthquakes is the soil liquefaction. Liquefaction can be defined as temporary loss in strength of saturated sandy and silty deposits under transient and cyclic loadings due to excess pore water pressure. This study includes determination of liquefaction potential in Erzincan city center and its vicinity. Due to the proximity of the North Anatolian Fault Zone, in a probable earthquake, Erzincan Province is thought to be affected. In this context, the earthquake scenarios were produced using the empirical expressions. Liquefaction potential for different earthquake magnitudes was determined. These earthquake magnitudes were selected as 6.0, 6.5, 7.0, 7.5, respectively. Liquefaction potential was investigated using standard penetration test (SPT) data. The first stage of the study, 63 boreholes in different locations was drilled and SPT was performed. Disturbed and undisturbed soil samples were taken from these boreholes. Laboratory testing was performed to determine physical properties of soil samples, and liquefaction potential analyses were examined using three methods, namely Seed and Idriss (J Soil Mech Found Div ASCE 97(9):1249–1273, 1971), Tokimatsu and Yoshimi (Soil Found 23(4):56–74, 1983), Iwasaki et al. (Soil liquefaction potential evaluation with use of the simplified procedure. International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, St. Louis, pp 209–214, 1981). In order to complete liquefaction analysis within a short time, MATLAB program was prepared. Liquefaction potential analyses were carried out with the MATLAB program. At the final stage of this study, liquefaction potential maps were prepared for different earthquake magnitudes. The expected results will be shared with the local authorities and important engineering remedial measurements will be proposed to prevent further life losses and to mitigate property losses.

New Developments in Geotechnical Earthquake Engineering

Based on the review on the advances of several important problems in geotechnical seismic engineering, the authors propose the initial analysis theory of time-frequency-amplitude (known as TFA for short), in an effort to realize the organic combination of time and frequency information and develop a groundbreaking concept to the traditional idea in the geotechnical seismic engineering area.

Spatial zonations for regional assessment of seismic site effects in the Seoul metropolitan area

Earthquake-induced hazards are profoundly affected by site effects related to the amplification of ground motions, which are strongly influenced by local geologic conditions such as soil thickness or bedrock depth and soil stiffness. In this study, an integrated geographic information system (GIS)-based system for geotechnical data, called the geotechnical information system (GTIS), was developed to establish a regional counterplan against earthquake ground motions in the Seoul metropolitan area. In particular, to reliably predict spatial geotechnical information, a procedural methodology for building the GTIS within a GIS framework was developed and applied to the Seoul area in Korea. To build the GTIS, pre-existing geotechnical data were collected in and around the study area, and then a walk-over site survey was conducted to acquire surface geo-knowledge data. In addition, the representative shear wave velocities for geotechnical layers were derived by statistically analyzing many seismic test data in Korea. The GTIS was used in a practical application to estimate site effects in the study area; seismic zoning maps of geotechnical earthquake parameters, such as the depth to bedrock and the site period, were created and presented as a regional synthetic strategy for earthquake risk assessment. Furthermore, seismic zonation of site classification was also performed to determine the site amplification coefficients for seismic design and seismic performance evaluation at any site and administrative sub-unit in the study area. The methodology and results of the case study of seismic zonations in the Seoul area verified that the GIS-based GTIS can be very useful for the regional estimation of seismic risk and also to support decisions regarding seismic hazard mitigation, particularly in the metropolitan area.

The EUROSEISTEST Strong-Motion Database and Web Portal

EUROSEISTEST is a European, multi‐purpose physical laboratory (test site) established in 1993 in the tectonically active graben of Mygdonia, a few tens of kilometers away from the city of Thessaloniki, in northern Greece (Fig. 1a; http://euroseis.civil.auth.gr; Pitilakis et al. , 2011). It is one of the longest‐running test sites in the world, providing researchers with high‐quality multidisciplinary data and facilities for conducting innovative experimental (e.g., Raptakis et al. , 1998; Jongmans et al. , 1998; Pitilakis et al. , 1999; Raptakis et al. , 2000) and theoretical studies (e.g., Chavez‐Garcia et al. , 2000; Makra et al. , 2001, 2005; Semblat et al. , 2005) on ground motion, site effects, soil, and site characterization (e.g., Raptakis et al. , 2000, 2005; Manakou et al. , 2010), wave propagation and soil‐foundation–structure interaction (e.g., Gueguen et al. , 2000). The establishment and operation of the experimental site has been under the responsibility of the Research Unit of Soil Dynamics and Geotechnical Earthquake Engineering (SDGEE) of the Civil Engineering Department of the Aristotle University of Thessaloniki with the contribution of the Institute of Engineering Seismology and Earthquake Engineering of the Earthquake Planning and Protection Organization of Greece (ITSAK‐EPPO), among other partners. EUROSEISTEST was initially funded by the European Union (EU; Directorate General XII for Research, Science & Technology) through three consecutive research projects: EUROSEIS‐TEST (EV5V‐CT.93‐0281, 1993–1995), EUROSEIS‐MOD (ENV4‐CT.96‐0255, 1996–1999), and EUROSEIS‐RISK (EVG1‐CT‐2001‐00040, 2002–2005). Since 2005, the maintenance and further development of the test site have been funded through resources of the SDGEE, several other EU (e.g., SERIES, http://www.series.upatras.gr/; NERA, http://www.nera-eu.org/) and international projects. In 2013, EUROSEISTEST completes 20 years of operation. During this time, its permanent strong‐motion network has recorded 190 seismic events, mostly from in and around the Mygdonia basin, but also few at regional distances (Fig. 1a). Recorded acceleration time series and …

Book Reviews

# Geotechnical Earthquake Engineering {#article-title-2} (Editors: Wei Wu and Ronaldo I. Borja) Review by: Benjamin R. Black As evidenced by the recent and seemingly more frequent occurrences of damaging earthquakes, the topic of earthquake geotechnical engineering would appear to be taking on a larger role in the efforts to develop earthquake-resistant structures. In this text, Professor Towhata has compiled a rather large volume of research data related to the occurrence, frequency, and distribution of earthquakes, as well as information collected over many years of field investigation, laboratory testing, and analysis of earthquakes. In the preface, Professor Towhata outlines some of the background and basis for his book. Professor Towhata developed the text from a compilation of his notes and handouts from university courses he has taught since 1985. As noted in the preface, one of the major problems with the text is the vast amount of information that it contains. The bulk of the case studies presented in the text and most of the specific examples of procedures and policies relate directly to Japan. This regional focus does not necessarily detract from the topics offered in the book, nor does it minimize the importance of the case studies, but it could limit the text's use in other regions of the world, especially the United States. The text is composed of 27 chapters broken up into three separate parts—Part 1: Knowledge of Soil Mechanics, Part 2: Problems Concerning Shaking of Soft Ground Undergoing Earthquake Loading, and Part 3: Liquefaction—and each chapter is then broken down further into short sections. In order to help guide readers of different backgrounds and levels of understanding Professor Towhata has used a three-category classification system—elementary, advanced, and miscellaneous. I did not find this classification system to be that helpful; however, other readers may. The text also includes both Japanese and English …

Large-Scale Numerical Modeling in Geotechnical Earthquake Engineering

Calibration, on the basis of data from centrifuge and shake table experiments, continues to promote the development of more accurate computational models. Capabilities such as coupled solid–fluid formulations and nonlinear incremental-plasticity approaches allow for more realistic representations of the involved static and dynamic/seismic responses. In addition, contemporary high-performance parallel computing environments are permitting new insights, gained from analyses of entire ground-foundation-structural systems. On this basis, the horizon is expanding for large-scale numerical simulations to further contribute toward the evolution of more accurate analysis and design strategies. The studies presented in this paper address this issue through recently conducted three-dimensional (3D) representative research efforts that simulate the seismic response of (1) a shallow-foundation liquefaction countermeasure, (2) a pile-supported wharf, and (3) a full bridge-ground system. A discussion of enabling tools ...

Application of Geostatistical Models for Estimating Spatial Variability of Rock Depth

Rock depth information of a site is a significant factor for geotechnical engineering and earthquake ground response analysis. In this paper, reduced level of rock at Bangalore is arrived from the 652 boreholes in the area covering 220 km2. Geostatistical modeling based on kriging (simple and ordinary) techniques has been applied for estimating reduced level of hard rock in Bangalore. The models are used to compute variance of estimated reduced level of the rock. A new type of cross-validation analysis proves the robustness of the developed models. The comparison between the simple and ordinary kriging model demonstrates that the ordinary kriging model is superior to simple kriging model in predicting reduced level of rock in the subsurface of Bangalore.

GIS-based soil liquefaction susceptibility map of Mumbai city for earthquake events

Abstract The problem of liquefaction of soil during seismic event is one of the important topics in the field of Geotechnical Earthquake Engineering. Liquefaction of soil is generally occurs in loose cohesionless saturated soil when pore water pressure increases suddenly due to induced ground motion and shear strength of soil decreases to zero and leading the structure situated above to undergo a large settlement, or failure. The failures took place due to liquefaction induced soil movement spread over few square km area continuously. Hence this is a problem where spatial variation involves and to represent this spatial variation Geographic Information System (GIS) is very useful in decision making about the area subjected to liquefaction. In this paper, GIS software GRAM++ is used to prepare soil liquefaction susceptibility map for entire Mumbai city in India by marking three zones viz. critically liquefiable soil, moderately liquefiable soil and non liquefiable soil. Extensive field borehole test data for groundwater depth, standard penetration test (SPT) blow counts, dry density, wet density and specific gravity, etc. have been collected from different parts of Mumbai. Simplified procedure of Youd et al. (2001) is used for calculation of factor of safety against soil liquefaction potential. Mumbai city and suburban area are formed by reclaiming lands around seven islands since 1865 till current date and still it is progressing in the area such as Navi Mumbai and beyond Borivali to Mira road suburban area. The factors of safety against soil liquefaction were determined for earthquake moment magnitude ranging from Mw = 5.0 to 7.5. It is found that the areas like Borivali, Malad, Dahisar, Bhandup may prone to liquefaction for earthquake moment magnitude ranging from Mw = 5.0 to 7.5. The liquefaction susceptibility maps were created by using GRAM++ by showing the areas where the factor of safety against the soil liquefaction is less than one. Proposed liquefaction susceptibility map of Mumbai city can be used by researchers for earthquake hazard analysis, for the preventive measures in disaster management, for urban planning and further development of Mumbai city and suburban area.

Dem Simulations in Geotechnical Earthquake Engineering Education

Behaviour of geotechnical material is very complex. Most of the theoretical frame work to understand the behaviour of geotechnical materials under different loading conditions depends on the strong background of the basic civil engineering subjects and advanced mathematics. However, it is fact that the complete behaviour of geotechnical material cannot be traced within theoretical framework. Recently, computational models based on Finite Element Method (FEM) are used to understand the behaviour of geotechnical problems. FEM models are quite complex and is of little interest to undergraduate students. A simple computational tool developed using Discrete Element Method (DEM) to simulate the laboratory experiments will be cutting edge research for geotechnical earthquake engineering education. This article summarizes the potential of DEM to simulate the cyclic triaxial behaviour of granular materials under complex loading conditions. It is shown that DEM is capable of simulating the cyclic behavior of granular materials (e.g. undrained, liquefaction and post liquefaction) similar to the laboratory experiments.

One-Dimensional Ground Response as a Preliminary Tool For Dynamic Analyses in Geotechnical Earthquake Engineering

This article discusses how to calibrate some parameters of two-dimensional finite element models for numerical analyses in geotechnical earthquake engineering. The calibration was made through the simulation of the one-dimensional vertical propagation of S-waves in elastic layers, whose theoretical solutions are available in literature. The numerical results were compared with those obtained by frequency domain analyses. The influence of several sources of damping arising in the model, including that deriving from boundary conditions and numerical integration, was investigated. The proposed calibration procedure constitutes a useful preliminary step for performing advanced dynamic analyses of any geotechnical system.

Correcting Liquefaction Resistance for Aged Sands Using Measured to Estimated Velocity Ratio

Factors for correcting liquefaction resistance for aged sands using ratios of measured to estimated shear-wave velocity (MEVR) are derived in this paper. Estimated values of shear-wave velocity (VS) are computed for 91 penetration resistance-VS data pairs using previously published relationships. Linear regression is performed on values of MEVR and corresponding average age. Age of the sand layer is taken as the time between VS measurements and initial deposition or last critical disturbance. It is found that MEVR increases by a factor of about 0.08 per log cycle of time, and time equals about 6years on average when MEVR equals 1 for the recommended penetration resistance-VS relationships. The resulting regression equation is combined with the strength gain equation reported by Hayati et al. 2008 in “Proc., Geotechnical Earthquake Engineering and Soil Dynamics IV,” to produce a MEVR versus deposit resistance correction relationship. This new corrective relationship is applied to create liquefaction resistance curves based on VS, standard penetration test blow count, and cone tip resistance for sands of various ages (or MEVRs). Because age of natural soil deposits is usually difficult to accurately determine, MEVR appears to be a promising alternative.

A comparative study on linear and nonlinear site response analysis

Site response analysis is usually the first step of any seismic soil-structure study. Geotechnical earthquake engineers and engineering geologist have been trying to find both practical and most appropriate solution techniques for ground response analysis under earthquake loadings. The paper attempts to give a critical overview of the field of site response analysis. In this paper, the influences of nonlinearity on the site response analysis summarized and were evaluated with a numerical example. Site response of a two layered soil deposit with the assumption of linear and rigid base bedrock (or viscoelastic half-space) was analyzed by using linear and nonlinear approaches. The amplification spectrum of the soil column is computed between the top and the bottom of this soil deposit. Nonlinear analysis was compared with the linear method of analysis. Steps involved in ground response analyses to develop site-specific response spectra at a soil site are briefly summarized. Some of the well-known site response analysis methods are summarized and similarities and differences between linear and nonlinear methods are compared by a numerical example.