Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

Abstract

This chapter presents a summary of the calibration exercises (i.e., element test simulations) submitted by nine numerical simulation teams that participated in the LEAP-ASIA-2019 prediction campaign. The standard sand selected for the campaign is Ottawa F-65, and researchers have developed several efforts to increase the database of laboratory tests to characterize the physical and mechanical properties of this sand (Carey TJ, Stone N, Kutter BL, Grain Size Analysis and Maximum and Minimum Dry Density of Ottawa F-65 Sand for LEAP-UCD-2017. Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-UCD-2017. Springer, 2019; El Ghoraiby MA, Park H, Manzari MT. Physical and mechanical properties of Ottawa F65 sand. In: Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-UCD-2017, Springer, 2019; Ueda K, Vargas RR, Uemura K, LEAP-Asia-2018: Stress-strain response of Ottawa sand in Cyclic Torsional Shear Tests, DesignSafe-CI [publisher], Dataset, https://doi.org/10.17603/DS2D40H, 2018; Vargas RR, Ueda K, Uemura K, Soil Dyn Earthq Eng 133:106111, 2020; Vargas RR, Ueda K, Uemura K, Dynamic torsional shear tests of Ottawa F-65 Sand for LEAP-ASIA-2019. Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-ASIA-2019, Springer, 2023). The objective of this element test simulation exercise is to assess the performance of the constitutive models used by the simulation teams for simulating the experimental results of a series of undrained stress-controlled cyclic torsional shear tests on Ottawa F-65 sand for two different relative densities (Dr = 50% and 60%) (Ueda K, Vargas RR, Uemura K, LEAP-Asia-2018: Stress-strain response of Ottawa sand in Cyclic Torsional Shear Tests, DesignSafe-CI [publisher], Dataset, https://doi.org/10.17603/DS2D40H, 2018; Vargas RR, Ueda K, Uemura K, Soil Dyn Earthq Eng 133:106111, 2020; Vargas RR, Ueda K, Uemura K, Dynamic torsional shear tests of Ottawa F-65 sand for LEAP-ASIA-2019. Model tests and numerical simulations of liquefaction and lateral spreading: LEAP-ASIA-2019, Springer, 2023). The simulated liquefaction strength curves demonstrate that majority of the constitutive models are capable of reasonably capturing the measured liquefaction strength curves both for Dr = 50% and 60%. However, the simulated stress paths and stress-strain relationships show some differences from the corresponding laboratory tests in some cases.

DOI： 10.1007/978-3-031-48821-4_2

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Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

Abstract

This chapter presents a summary of Type-B and Type-C numerical simulations submitted by nine numerical simulation teams that participated in the LEAP-ASIA-2019 prediction campaign, with the results of a selected set of centrifuge model tests on the seismic behavior of a uniform-density, 20-m-long, and 5-degree sandy slope. Time histories of response accelerations, excess pore water pressures, and lateral displacements at the ground surface are compared to the experimental results. A majority of Type-B and Type-C numerical simulations were capable of simulating well the experimental trends observed in the centrifuge tests; in particular, Type-C simulations were found to capture the measured responses more accurately by adjusting the model parameters. Although it is quite challenging to perfectly capture all measured responses (e.g., accelerations, pore pressures, and displacements), the simulation exercises demonstrate that the numerical simulations can be further improved by accumulating high-quality experimental results as a database.

DOI： 10.1007/978-3-031-48821-4_3

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Geotechnical Society  

DOI： 10.3208/jgssp.v10.os-13-02

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Geotechnical Society  

DOI： 10.3208/jgssp.v10.os-40-03

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.soildyn.2023.108110

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Japan Society of Civil Engineers  

DOI： 10.2208/jscejj.22-13014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s11600-023-01158-6

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Other Link： https://link.springer.com/article/10.1007/s11600-023-01158-6/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

This paper presents a study of liquefaction analysis at sand layers of the Izumio site, under ground motion variation during a strong earthquake in Osaka, Japan. Site investigation using standard penetration test and shear wave velocity measurement is conducted. Finite element liquefaction site response analysis integrated with a strain space multiple mechanism model is conducted. Ground motions variation is considered based on the seismic record at surrounding seismic stations. Attenuation analysis is conducted to determine the scaling factor for ground motions. Several results, such as acceleration profiles and cyclic behaviours are presented. The empirical analysis is also conducted to verify the results of the numerical analysis. The results explained that cyclic behaviours of sandy layers in the Izumio site show the liquefaction tendency. The results also showed that sandy layers are indicated as critical layers during the strong earthquake due to the excess pore water pressure reaching the liquefaction threshold. The results of the empirical analysis also present liquefaction indication at sand layers under the variation of ground motion, since the factor of safety against liquefaction is less than 1. The results are generally well-agree with liquefaction evidence and prediction presented in the previous study. The results could bring practical importance in understanding liquefaction potential in the study area.

DOI： 10.1016/j.sandf.2022.101218

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Language：English   Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

DOI： 10.1007/978-3-031-11898-2_33

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Part of collection (book)   Publisher：Springer International Publishing  

DOI： 10.1007/978-3-031-11898-2_118

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Authorship：Lead author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

A round-robin centrifuge model test for an identical saturated sloping deposit with various initial conditions was conducted in the framework of liquefaction experiments and analysis project (LEAP) with 10 international institutes. To pursue two main objectives: (1) the validation of the generalized scaling law (GSL); and, (2) the development of additional experimental data that fill the gaps in the previous LEAP, each institute was assigned two tests, identical in prototype scale: a model following the generalized scaling law and a model following conventional centrifuge scaling law. The test results show a significant match in the dynamic behavior of these models, which validates the applicability of the GSL under given conditions. However, in this study, a deviation is observed when the surface ground deformation becomes larger (i.e., 250 mm). The trend surface that correlates peak amplitude of input acceleration (PGAeff), the relative density of the ground (Dr_qc(2.0 m)), and surface lateral displacement (Ux) is updated and confirmed with new data sets.

DOI： 10.1016/j.soildyn.2022.107237

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Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/13632469.2020.1751346

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Authorship：Lead author   Publishing type：Part of collection (book)  

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Authorship：Lead author  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media Deutschland GmbH  

Several previous investigations have suggested that ground motion as described by various parameters and resonance effects could have contributed to the damage observed during an earthquake. This paper presents a ground motion parameters study and site investigation in Northern Thailand during the Tarlay Earthquake of 2011. Ground motion parameters recorded at the closest seismic station to the earthquake rupture, i.e. Mae Sai Station (MSAA) are studied. Microtremor measurement was performed at the MSAA site. The horizontal to vertical spectral ratio (H/V) from the investigation are interpreted. Spectral acceleration ratios based on data from the MSAA are compared to determine the possibility of resonance during the earthquake. Spectral acceleration data based on recorded ground motion are compared to guideline design spectral acceleration to determine the critical period. Results show that during the Tarlay Earthquake, significant duration was 24 s. Within this duration, resonance was plausible within the frequency range of 1.82 to 2.1 The critical period ranged from 0.4 to 0.6 s, indicating that low-medium story buildings were most vulnerable. Results also show that horizontal ground motion was relatively dominant in the destruction of structural buildings during the earthquake.

DOI： 10.1007/s10706-020-01619-5

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Publishing type：Research paper (scientific journal)  

© 2020 Elsevier Ltd The Liquefaction Experiments and Analysis Project (LEAP) is a joint international project that pursues the verification, validation and uncertainty quantification of numerical liquefaction models. As part of this project, eight centrifuge models were developed at the facilities of Kyoto University, to simulate the dynamic behavior of a submerged, uniform-density, 20 m long, 4 m deep and 5° sloping deposit of Ottawa F-65 sand. The results are intended to compose part of a reliable database in the development of current and future V&V processes of liquefaction models. This paper presents the main characteristics of the model preparation and testing process, and an analysis of: (1) the validity of the “Generalized Scaling Law” for centrifuge modeling (2) the consistency and repeatability of the tests by means of the development of an additional repeatability-test, and numerical modelling, and (3) the importance of the viscosity of the fluid in liquefaction modelling.

DOI： 10.1016/j.soildyn.2020.106472

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Language：Japanese   Publisher：The Japanese Geotechnical Society  

<p>When laying water pipelines, excavated soil is generally disposed and replaced with commercially available sandy material. Reuse of the excavated soil yields reduction of both the environmental loads and the construction costs. Although "The guideline for use of excavated soil" by Ministry of Land, Infrastructure and Transport, specifies reusable soil types, it is not common practice to use the excavated soil for the laying of water pipeline because the specification requires complicated laboratory soil tests for the judgement. In this study, the applicability of the on-site simple method, called the "FK method", is evaluated through a series of laboratory tests and model tests by using soil samples collected from various regions in Japan. As a result, the FK method successfully indicated compaction characteristics and bearing capacity of excavated soil. Hence, the method can be used on-site to judge the availability of excavated soil for water pipe laying works.</p>

DOI： 10.3208/jgs.15.257

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Language：Chinese   Publishing type：Research paper (scientific journal)   Publisher：Academia Sinica  

Desaturation is a mitigation method for sand liquefaction. Reducing saturation has been proposed to improve liquefaction resistance of saturated sandy foundation. Comparison of the centrifuge test numerical simulation was carried out, based on the modified single-phase fluid numerical method with simultaneous updating fluid modulus and the simplified method with fixed fluid modulus. The results show that the modified method is more reasonable because it considers the change of fluid modulus due to pore pressure change. The simplified method will underestimate the accumulation of pore pressure in the desaturated sand. Numerical simulation of liquefaction deformation on gently tilting desaturated sandy ground with different saturations and angles is carried out based on the modified single-phase fluid numerical method. The results show that the increasing velocity and peak value of excess pore pressure increase with the increase of saturation. The peak value of the excess pore pressure decreases by 20%-65%, and the peak value of acceleration response decreases significantly at the same depth with the saturation decreased from 100% to 96.4%. Along the foundation depth from 0.75 m to 9.00 m, lateral deformation decreases by about 20%-50%. It can conclude that the saturation reduction plays a positive role in reducing lateral deformation of liquefiable sandy foundation. The influence of saturation on lateral deformation is increasing evident with decrease of foundation depth.

DOI： 10.16285/j.rsm.2018.1271

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Language：Japanese   Publishing type：Research paper (international conference proceedings)  

A round-robin centrifuge model test for an identical saturated sloping deposit with various initial conditions was conducted in the framework of liquefaction experiments and analysis project (LEAP) with 10 international institutes. To pursue two main objectives: (1) the validation of the generalized scaling law (GSL); and, (2) the development of additional experimental data that fill the gaps in the previous LEAP, each institute was assigned two tests, identical in prototype scale: a model following the generalized scaling law and a model following conventional centrifuge scaling law. The test results show a significant match in the dynamic behavior of these models, which validates the applicability of the GSL under given conditions. However, in this study, a deviation is observed when the surface ground deformation becomes larger (i.e., 250 mm). The trend surface that correlates peak amplitude of input acceleration (PGAeff), the relative density of the ground (Dr_qc(2.0 m)), and surface lateral displacement (Ux) is updated and confirmed with new data sets.

DOI： 10.1016/j.soildyn.2022.107237

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Language：English   Publishing type：Research paper (scientific journal)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Taylor and Francis Ltd.  

This article presents a study of liquefaction resistance behaviour of sand using a cyclic triaxial test. The site investigation was performed, and frozen undisturbed specimens were taken from the Izumio site in Osaka, Japan. According to the evidence in 1995 Kobe Earthquake, the first two sand layers are vulnerable to undergo liquefaction. The effect of deviatoric stress on liquefaction resistance was focused on in this study. The excess pore pressure ratio, hysteresis loop, and effective stress path from the cyclic triaxial tests were reported. A multispring element model was employed to simulate the soil behaviour under cyclic loading. The results showed that applied deviatoric stress could influence the liquefaction resistance of sandy soil samples. The plots of the cyclic stress ratio versus the number of cycles to generate liquefaction known as a liquefaction resistance curve can be then constructed and compared with other sands.

DOI： 10.1080/1064119X.2018.1485793

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Publishing type：Research paper (international conference proceedings)  

© 2019 Associazione Geotecnica Italiana, Rome, Italy. This paper presents the applicability and application limits of predicting liquefaction damage for sheet pile structural model using the strain space multiple mechanism model based on the large deformation theory called “FLIP TULIP”. Specifically, the results of centrifuge model test conducted on the sheet pile structure model and the stress generated in the soil-structure interaction numerical model obtained using FLIP TULIP were compared and examined. As a result, combining the soil and structure with joint elements (Ks = 0), numerical simulations adequately reproduced experimental results of soil deformation and the bending moments of sheet pile. Therefore, it was confirmed that the large deformation analysis provides realistic results.

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Publishing type：Research paper (international conference proceedings)  

© 2019 Associazione Geotecnica Italiana, Rome, Italy. As part of the LEAP Project, three centrifuge tests were carried out in the facilities of DPRI at Kyoto University. The experiment aims to simulate the dynamic response of a uniform-density sloping deposit of clean sand, subjected to a ramped sinusoidal wave; this paper introduces specific details of the model preparation, testing procedures, and the achieved response. Additionally, a brief discussion related to the median values and variability of the relative density (Dr), and the peak ground acceleration (PGA) is presented, because these were identified as the “key parameters” for the estimation of the horizontal surface displacement due to lateral spreading (Ux). As an attempt of the sensitivity analysis, a series of Monte Carlo simulations were developed in order to analyze the sensitivity in the estimation of Ux under the variabil-ityofthekeyparameters.

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Publishing type：Research paper (scientific journal)  

© 2017 Elsevier Ltd The LEAP international collaboratory is introduced and its key objectives and main accomplishments during the planning phase of the US-LEAP (LEAP-2015) are presented. The main theme of LEAP-2015 was lateral spreading of sloping liquefiable soils. A summary of the results of the laboratory element tests performed on the selected soil (Ottawa F-65) is presented. The numerical simulations submitted by several predictors at different stages of the project are compared with the measured responses of sloping deposit specimens tested in a rigid box at six different centrifuge facilities around the world. The comparisons are presented for three rounds of simulations labeled here as types A, B, and C simulations. The type A simulations involved the response of the soil specimen to a prescribed base excitation with a maximum amplitude of 0.15g (Motion #2). Comparisons of the numerical simulations with the experimental results show that a sub-set of type A simulations were in reasonably good agreement with the responses measured in the reference centrifuge experiment. The predictors subsequently assessed the performance of their type A simulations by comparing them to the measured responses, made the necessary adjustments in their models, and conducted a type B simulation of the response of the same soil specimen subjected to an amplified base excitation with a maximum amplitude of 0.25g (Motion #4). In these type B simulations, the achieved base motions were used and the simulations showed an improved correlation with the experimental results. The predictors also conducted a type C simulation of the original test (Motion #2) using the base motions achieved on the six centrifuge facilities. The results showed very good agreement with the experimental results.

DOI： 10.1016/j.soildyn.2017.05.015

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Publishing type：Research paper (scientific journal)  

© 2017 The Liquefaction Experiments and Analysis Projects (LEAP) is an international effort to produce a set of high quality test data and to then use it in a validation exercise of existing computational models and simulation procedures for soil liquefaction analysis. A validation effort (LEAP-GWU 2015) was undertaken using a benchmark centrifuge model of a sloping deposit tested in a rigid-wall container. This article presents and discusses the shear stress-strain responses and effective stress paths of the LEAP-GW 2015 centrifuge tests and numerical predictions (including an assessment of the effects of the rigid boundaries).

DOI： 10.1016/j.soildyn.2017.10.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Chulalongkorn University  

On 24 March 2011, the 6.8 Mw Tarlay Earthquake occurred at the border of Thailand and Myanmar. The earthquake not only resulted in structural building damage but also triggered liquefactions on sandy soils in Northern Thailand. Several site investigations including SPT and shear wave velocity measurements are conducted to study subsoils condition in this area. Ground motions at several seismic stations were recorded during the earthquake. In this study, four soil sites in Chiang Rai and Chiang Mai are selected, including a site at the border of Thailand and Myanmar. Next generation attenuation models are employed to generate the input ground motions for each site. Non-linear finite element analysis is employed to observe soil behaviour under the earthquake. The results showed that liquefaction could happen in the investigated area during an earthquake. The result is confirmed by the liquefaction evidence found in Chiang Rai during the 6.8 Mw Tarlay Earthquake. This research can help raise awareness of the impacts of earthquakes to this region.

DOI： 10.4186/ej.2018.22.3.291

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DOI： 10.1016/j.soildyn.2017.05.018

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER SOC CIVIL ENGINEERS  

Twenty-four centrifuge model tests have been conducted at nine different geotechnical centrifuge facilities around the world as part of the international LEAP effort (liquefaction experiments and analysis projects). All of the centrifuge models represent a 4 m deep 5 degree sloping submerged sand deposit. The mean effective PGA of the input motion for all of the experiments was approximately 0.15 g and the mean relative density was approximately 65%, but the effective PGA's varied between about 0.07 g and 0.3 g, and the relative densities varied between about 40% and 75%. The test matrix was designed to enable experimental quantification of not only the median response but also the trend and sensitivity of the model response to density and shaking intensity. Quantification of the sensitivity of the response to initial conditions is a prerequisite for objective evaluation of the quality of the model test data. In other words, a discrepancy between two experiments should be evaluated after accounting for the uncertainty in the initial conditions and the sensitivity of the response to initial conditions. For the first time, a sufficient number of experiments has been performed on a similar problem to provide meaningful quantitative evaluation of the trend between PGA, density, and displacement. The sensitivity is quantified by the gradient of the trend and the uncertainty of the trend is quantified from the residuals between the fitting data and the trend.

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DOI： 10.2208/jscejseee.74.I_598

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Language：Japanese   Publisher：公益社団法人 土木学会  

熊本地震では，水道施設にも多数の被害が生じたが，河川に囲まれた軟弱な粘土層と飽和砂層で構成された低地にある水道用井戸の水源地周辺においては，想定していなかった顕著な地盤変状に伴う水道施設の被害や，新耐震基準以降に建設された水道施設の建築物に基礎被害が多数確認された．筆者らは，浄水場や下水処理場および上下水道管路網の地震被害軽減対策を研究しており，これらの水道施設の被害と液状化を含む地盤の地震時挙動との関連性や対策に関する知見を得るために各種調査や検証解析を実施した．本報告では，これらの調査結果を報告するとともに，熊本市の水道事業において特に重要な井戸水源地施設の基礎杭及び井戸ケーシングを対象として，地震被害のメカニズムや要因を分析し，今後の耐震設計における留意点などを考察した．

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier Ltd  

This paper presents a description of testing procedure and results of the LEAP-GWU-2015, and an investigation of the effect of the radial gravity field in centrifuge modelling. Dynamic responses of two models are compared. One had a planar surface with a 5° slope relative to the base of the container
the other had a curved surface to maintain a constant slope angle with respect to the radial g-field. For the centrifuge tests employed in this study, the slope and base excitation are in the tangential direction to spinning centrifuge. Results show that spikes in acceleration records due to cyclic mobility associated with lateral displacements appeared on both models. However, for the plane surface model, acceleration spikes in the negative (upslope) direction are more prominent and the residual downslope ground deformation was larger. Larger lateral displacement was observed in the plane model, while surface displacements in the curved model are smaller and uniform along the length of the model. For the plane model, the radial gravity acting near the slope top is almost constant and gradually increases towards the slope toe which causes a net increase in effective slope angle. Curving the model ground surface is recognized as leading to uniform lateral displacements along the length of the model surface.

DOI： 10.1016/j.soildyn.2018.05.005

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DOI： 10.1016/j.soildyn.2018.07.00

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DOI： 10.1080/13632469.2018.1469441

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Language：Japanese   Publisher：関西大学先端科学技術推進機構  

CiNii Books

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Language：Japanese   Publisher：Institute of Social Safety Science  

<p>During a scenario earthquake with <i>M</i>_W9.0 along the Nankai Trough, strong ground motion is expected in the focal area, Wakayama Prefecture, Japan. In order to simulate the seismic damage of railway structures, it is necessary to estimate strong motions at the sites of interest with sufficient accuracy, taking into account local site effects. In this study, seismic waveforms at 54 sites for permanent railway station along JR Kinokuni Line were predicted based on the SMGA models considering the empirical site amplification and phase effects. The predicted seismic waveforms will be useful for rational safety assessment of a railway structure.</p>

DOI： 10.11314/jisss.31.339

CiNii Books

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

&nbsp;Liquefaction was investigated after the 6.8 Mw earthquake on March 24, 2011 (Tarlay earthquake) in Chiang Rai Province, Northern Thailand. Several investigations including soil boring, SPT, and SASW tests were carried out and the results were used to perform one dimensional wave propagation analysis using finite element method. The maximum acceleration of 0.206 g recorded in Chiang Rai was used as the input motion. The input motion was applied at bottom of soil column to observe soil behavior under seismic loading. The result shows that liquefaction could occur at shallow depth (0 to 16.5 m), which is also followed by settlement (1.8 to 4 cm) due to compressibility of soil during earthquake. The analysis result indicates that there is no significant dissipated pore water pressure on liquefied layer. The longer duration of liquefaction is identified on layer (SP-SM), which have the low SPT values. Excess pore water pressure from bottom layer might also concentrate at this layer. The concentration of excess pore water pressure may trigger the duration of liquefaction up to 50 seconds. In addition, the excess pore water pressure ratio linked to impacted depth warns that the soils with excess pore water pressure in range of 0.9 to 1 are possible to get worse impact if a stronger earthquake attacks this area in the future.

DOI： 10.2208/jscejseee.73.I_135

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Publishing type：Research paper (international conference proceedings)  

© 2017 Taylor & Francis Group, London. In this study, a centrifuge model tests and effective stress analyses are performed on a steel frame building with pile-foundation subject to Tsunami such as those seriously damaged during the 2011 off the Pacific coast of Tohoku Earthquake (Magnitude 9.0). The centrifuge model tests at a scale of 1/200 in geometry are performed to simulate the overturning of a building subject to combined effects of soil liquefaction and Tsunami. With the effective stress analyses, this study demonstrates the importance of the combined effects of soil liquefaction at pile foundations in addition to the external force of Tsunami.

DOI： 10.1201/9781315161563-10

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

In this study, centrifuge model tests and effective stress analyses are performed on a tsunami-affected breakwater similar to those that were seriously damaged during the magnitude-9.0 East Japan Earthquake in 2011. The centrifuge model tests are performed at a scale of 1/200 to simulate the failure of the breakwater. This study is a significant improvement on a previous one [1] by the same authors. The centrifuge model tests now allow the seepage flow to be blocked as well as admitted, and the effective stress analyses are now performed based on the finite strain formulation in order to take large deformations into account instead of just the infinitesimal strain formulation that is applicable only to small displacements. Both the centrifuge model tests and the effective stress analyses demonstrate the important part played by the seepage of pore water in the failure of the rubble mound, in addition to the wave force of the tsunami action. In particular, it is shown that the breakwater damage of 2011 could have been prevented or at least mitigated by preventing seepage flow in the rubble mound.

DOI： 10.1016/j.soildyn.2016.09.009

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J-GLOBAL

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

This paper reports the results of a series of centrifuge tests examining dynamic responses of single and 3 x 3 grouped piles embedded in sand and supporting SDOF and 2DOF structures. A total of 7 model tests were conducted with the centrifugal acceleration of 40 g. Each model was subjected to 12 sinusoidal waves with constant acceleration amplitude and varying frequencies. The results of the tests indicate that pile-head motion is dominated by two sequential frequencies: a lower frequency (f(SSI)) where pile head motion is substantially maximized and a higher one (f(pSSI)) where the response is minimized with respect to free field surface motion. These results confirm recent published numerical results on single piles supporting SDOF structures and generalize their findings to grouped piles supporting SDOF and 2DOF structures. The results show also strong mobilized kinematic interaction effect generating significant pile bending when the ground is excited at its resonant frequency. On the other hand, structural vibrations tend to impose large bending moments as the excitation frequency approaches the natural frequency of the coupled soil-pile-structure system. Distribution of pile bending moments in the group is found to be a function of the pile position and the excitation frequency. In contrast to inner piles having the greatest kinematic bending moments, outer piles have a more pronounced inertial ones. (C) 2016 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.soildyn.2016.08.002

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Language：Chinese   Publishing type：Research paper (scientific journal)   Publisher：Academia Sinica  

Lateral spreading due to liquefaction of sandy soils is a significant cause of damage to the important engineering facilities and buildings in earthquakes. FLIP ROSE is a two-dimensional finite element analysis program for seismic liquefaction problems. A strain space multiple mechanism model (cocktail glass model) is implemented in the program for analysis of the granular material. A two dimensional finite element model is proposed to predict and analyze liquefaction-induced lateral spreading in gently sloping ground under the seismic loading. This numerical simulation model is verified using the excess pore water pressure, the lateral acceleration, the arias intensity and the lateral displacement time histories recorded in three sets of free-field lateral spreading centrifuge tests. The computed response shows good agreement with the centrifuge test measurements. The final lateral displacements in the gently sloping ground with the different gradients are predicted by this simulation model after sandy liquefaction. It shows that the gradient of gently sloping ground plays a more and more important role in the liquefaction-induced lateral spreading as the depth increases.

DOI： 10.16285/j.rsm.2016.08.039

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：The Japanese Geotechnical Society  

Demands for the testing of large prototypes in geotechnical engineering are increasing, while restrictions are recognized, such as costs and limited scale of testing facility. To resolve such demands and restrictions, Iai et al. (2005) proposed a scaling law by combining the scaling law for centrifuge testing with the one for 1-g dynamic-model testing. They call it the "generalized scaling law" in dynamic centrifuge modelling. The objective of the present study is to investigate and point out issues on the applicability of the scaling law through the technique of "new" modelling of models for dynamic behavior of pile foundations in both dry and saturated sand ground. Through comparison in the prototype scale, the applicability of the scaling law to bending moments was confirmed on the condition that centrifugal acceleration was more than 4.9 g for dry condition, and 14.4 g for saturated condition of 1/100 scale model.

DOI： 10.3208/jgssp.JPN-026

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (international conference proceedings)  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

Under seismic excitation, a pile undergoes stresses stemming from both the vibration of the surrounding soil (kinematic interaction) and that of the superstructure (inertial interaction). The relative contributions of kinematic and inertial interaction on the magnitude of seismic forces induced in pile foundations are investigated by means of nonlinear two-dimensional (2D) finite element (FE) analyses. The interaction between the pile and the surrounding soil in three-dimensional (3D) type was idealized in the 2D analysis using soil-pile interaction springs with hysteretic nonlinear load displacement relationships. Parametric analyses are carried out, focusing on normalized seismic forces in the piles as affected by typical characteristics of structures and piles as well as ground nonlinearity. The results of the study provide a new interpretation of the interplay between pile kinematic and inertial seismic forces. The numerical results showed that for relatively short/stiff piles or where structure's natural frequency is lower than that of the ground, the kinematic interaction can be the prime contributor to the seismic forces in the pile provided that the excitation frequency is not close to the natural frequency of the coupled soil-pile-struc ture system, f(SSI). In a frequency band approaching f(SSI), the inertial interaction generally prevails imposing large bending moments at or near the pile head. The results showed also that maximum kinematic seismic force does not always occur at the fundamental frequency of the deposit. For certain relative soil-pile stiffness and excitation amplitudes, the largest peak of the lcinematic seismic forces in piles can be occurring at the second mode. (C) 2015 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compgeo.2015.05.011

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

&nbsp;Occurrence of liquefaction in the wide range of Kanto plain has been reported after the great Tohoku earthquake. Tremendous damage associated with the liquefaction includes damage on residential houses, roads, and water and sewage systems. As professional engineers and researchers who design and construct water treatment and sewage plants and pipelines, and study geotechnical site conditions, the authors conducted investigation through interviewing with the responsible personnels in Chiba Prefecture, Urayasu city, Itako city, Wanigawa water treatment plant, and Amagasaki city which suffered severe damage at the 1995 Hyogoken-Nanbu earthquake. Based on the hearing investigation, analyses are made on characteristics of those damages due to liquefaction and local site conditions and some measures for mitigation are introduced.

DOI： 10.2208/jscejseee.71.I_983

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Language：Japanese  

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Language：Japanese  

CiNii Books

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Language：English   Publisher：The Japanese Geotechnical Society  

Large-scale liquefaction was caused by the 2011 off the Pacific coast of Tohoku, Japan, earthquake and many pipes in the liquefied ground suffered serious damages. One of the issues pointed out after the earthquake is the dynamic behavior and the mechanism of pipes near a structure in the liquefied ground. This study focuses on evaluating the dynamic behavior through centrifuge model test. Test results show that the uplift of pipes in the liquefied ground occurred during an earthquake and liquefaction happens at that time. After an earthquake, pipes start to sink with increasing effective stress. The characteristic of damage mechanism depends on the depth of pipes and the state of ground (in liquefiable layer, at ground water level, or in the unsaturated layer). The data also shows that the direction of force interacting pipes during liquefaction was only bending direction. So we should reconsider the design criteria for pipes which is widely used in Japan applying to axial force.

DOI： 10.3208/jgssp.v03.j02

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

When designing buried structures using a performance-based framework, it is important to estimate their uplift displacement. A simplified method is proposed for predicting the uplift displacement of a hollow cylinder structure buried in shallow backfill based on the equilibrium of vertical forces acting on the structure during earthquakes. However, this method only provides the maximum value, which frequently is overestimated in practical applications. To offset this limitation, first, the uplift behavior of buried hollow cylinder structures subjected to strong earthquake motions was simulated. Then, two-dimensional effective stress analyses based on the multiple shear mechanism for soil were conducted, and the results were compared with the centrifuge test data. The soil parameters were evaluated based on laboratory test results. The seismic response data from 20 g centrifuge tests were analyzed, and the results were generally consistent with the results of centrifuge model tests. In particular, the effective stress model showed a reasonable ability to reproduce the varying degrees of uplift displacement depending on the geotechnical conditions of trench soils adjacent to the hollow cylinder structures buried in shallow ground. (C) 2014 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.soildyn.2014.05.006

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Language：Japanese  

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10422448

Language：English   Publishing type：Research paper (international conference proceedings)  

Over the past twenty years after the VELACS project, with major advancement of computer simulation technologies, research works on numerical constitutive modelling of liquefiable sand have been conducted intensively. Contribution of the VELACS project on the development of numerical modeling in this field has never been underrated. However, with the development of new and innovative models, we believe that now is the time to revisit the project and help define direction of research for possibly another twenty years&#039;. As a pilot project for the future international collaborations to examine the capabilities of existing numerical techniques for liquefaction analysis through laboratory experiments and centrifuge tests, a Class A prediction is conducted by numerical modelers of four institutes for a series of centrifuge experiments of flat and inclined saturated sand deposits.A brief description of the experiments, results of the numerical predictions, and general remarks for the next step are presented in this paper. © 2015 Taylor &amp; Francis Group, London.

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Other Link： http://orcid.org/0000-0002-1543-1626

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCI LTD  

The influence of vertical loads on the lateral response of group piles installed in sandy soil and connected together by a concrete cap is studied through finite elements analyses. The analyses focus on the five piles in the middle row of 3 x 5 pile groups. The vertical load is applied by enforcing a vertical displacement equivalent to 2% of the pile diameter through the pile cap prior to the application of the lateral loads. The results have shown that the lateral resistance of the leading pile (pile 1) does not appear to vary considerably with the vertical load. However, the vertical load leads to 23%, 36%, 64%, and 82% increase in the lateral resistance of piles 2-5, respectively. The increase in the lateral pressures in the sand deposit is the major driving factor to contribute the change in the lateral resistance of piles, depending on the position of the pile in the group. The distribution of lateral loads among piles in the group tends to be more uniform when vertical loads were considered leading to a more economical pile foundation design. (C) 2013 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.compgeo.2013.09.022

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

&nbsp;Coastal embankment has been constructed to protect coastal area for earthquake and tsunami. But seismic-resistant shortage is pointed out. To improve the disaster prevention performance, seismic countermeasures should be optimized both performance and cost, and evaluated ductility for Huge earthquake hard to collapse. In this study intended for permeable grouting method and examine effect and ductility by centrifuge model tests. It is proved that under the sea wall remarkable share deformation occurs due to liquefaction, so improvement this area is quite effective and seismic-resistant can be optimized. It is confirmed that permeable grouting method has peculiar ductility which primary factor is cohesion. Deformation characteristic is improved to the cyclic shear loading, seepage of pore water is restricted and with dilatancy of soil an effective stress increased and shear resistance became higher.

DOI： 10.2208/jscejseee.70.I_44

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

&nbsp;The characteristics of a soil layer are not usually uniform, and uneven settlement was often observed in a clay stratum. In case of reclamation above the clay stratum, there is a possibility that the uneven settlement in the clay stratum affect the characteristics of the sand layer. Especially, the stress state of the ground might be affected. In this research, the stress distribution of the ground above the clay layer with a settlement were investigated by a series of centrifuge model test. As a result, the non-uniform stress distribution in the ground due to the settlement is observed. This non-uniform distribution of the stress correspond to the &plusmn;50% level of the variation in observed in-situ SPT N value.

DOI： 10.2208/jscejseee.70.I_751

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

The 2004 earthquake in Niigata-ken Chuetsu, Japan, caused widespread damage to sewer pipelines due to uplift behaviors caused by ground settlement after liquefaction. Sewer pipelines, which are important lifelines, suffer damage when sewerage systems cease to operate over a long period of time. Manholes ejected from the ground's surface can disrupt traffic. To study the failure mechanism after the earthquake, the Nagaoka city government conducted an open-cut survey of the damaged sewerage systems. The main features of the collected data included the locations of damaged sections and the inclination of the sewer pipes before and after the earthquake. In the present study, the cause of damage to the sewerage systems was investigated using the datasets and the standard penetration test (SPT) borehole logs. The relationship between the sewer pipeline damage and the geological settings in the affected area reveals that the groundwater depth and the geotechnical properties of the original subsoils acted as the key parameters influencing the manhole uplift behavior. Also, the uplift mechanism was investigated through centrifuge modeling tests, and these findings agree well with the test results obtained in this study. (C) 2013 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.enggeo.2013.07.011

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The strain space multiple mechanism model idealizes the behavior of granular materials based on a multitude of virtual simple shear mechanisms oriented in arbitrary directions. Within this modeling framework, the virtual simple shear stress is defined as a quantity that depends on the contact distribution function as well as the normal and tangential components of inter-particle contact forces, which evolve independently during the loading process. In other terms, the virtual simple shear stress is an intermediate quantity in the upscaling process from the microscopic level (characterized by the contact distribution and inter-particle contact forces). The stress space fabric (i.e. the orientation distribution of the virtual simple shear stress) produces macroscopic stress through the tensorial average. Thus, the stress space fabric characterizes the fundamental and higher modes of anisotropy induced in granular materials. Comparing an induced fabric associated with the biaxial shear of plane granular assemblies obtained via a simulation using Discrete Element Method to the strain space multiple mechanism model suggests that the strain space multiple mechanism model has the capability to capture the essential features in the evolution of an induced fabric in granular materials. Copyright (c) 2012 John Wiley & Sons, Ltd.

DOI： 10.1002/nag.2087

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This paper presents the finite strain formulation of a strain space multiple mechanism model for granular materials. Because the strain space multiple mechanism model has an appropriate micromechanical background in which the branch and complementary vectors are defined in the material (or referential) coordinate, the finite strain formulation is carried out by following the change in these vectors, in direction and magnitude, associated with deformation in the material. By applying the methodology for compressible materials established in the finite strain continuum mechanics, decoupled formulation that decomposes the kinematic mechanisms into volumetric and isochoric components is adopted for the strain space multiple mechanism model. Lagrangian (material) description of integrated form is given by a relation between the second Piola-Kirchhoff effective stress tensor and the Green-Lagrange strain tensor; Eulerian (spatial) description by a relation between the Cauchy effective stress tensor and the Euler-Almansi strain tensor. In particular, the volumetric strain is defined as a logarithm of Jacobian determinant. Lagrangian (material) description of incremental form is derived through the material time derivative of the integrated form. The counterpart in the spatial description is derived through the Lie time derivative, given as a relation between the Oldroyd stress rate of Kirchhoff stress and the rate of deformation tensor (sometimes called stretching in the literatures). An example is shown to discuss the applicability of the finite strain formulation. © 2012 John Wiley & Sons, Ltd.

DOI： 10.1002/nag.2084

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Language：Japanese   Publisher：京都大学防災研究所技術室  

京都大学防災研究所の遠心力載荷装置は2年前に更新を行った。更新によりアームの剛性を強化し, 振動台駆動時に加振周波数50 Hz付近でアームが共振する問題を解消した。しかし, 更新後の装置について, 実験者からプラットフォームの剛性不足, 新規に導入したプラットフォーム固定方式の欠陥, 振動台から上下動が発生しているとの指摘があった。これらの問題を改善するために, 昨年再度装置の改修を行った。改修によりプラットフォームを再度更新し, 固定方式についても改造を行った。本調査では, 更新したプラットフォームおよび振動台やアームに加速度計を設置し, 振動台の加振試験を行い, 振動特性を調査した。その結果, プラットフォームの剛性不足が改善したことを確認した。また, 振動台で発生していた上下動は, プラットフォームの固定, DITHERと呼ばれる振動台の制御信号, 振動台の機械的構造が主な原因であることがわかった。

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

The strain space multiple mechanism model idealizes the behavior of granular materials on the basis of a multitude of virtual simple shear mechanisms oriented in arbitrary directions. Within this modeling framework, the virtual simple shear stress is defined as a quantity dependent on the contact distribution function as well as the normal and tangential components of interparticle contact forces, which evolve independently during the loading process. In other terms, the virtual simple shear stress is an intermediate quantity in the upscaling process from the microscopic level (characterized by contact distribution and interparticle contact forces) to the macroscopic stress. The stress space fabric produces macroscopic stress through the tensorial average. Thus, the stress space fabric characterizes the fundamental and higher modes of anisotropy induced in granular materials. Herein, the induced fabric is associated with monotonic and cyclic loadings, loading with the rotation of the principal stress, and general loading. Upon loading with the rotation of the principal stress axis, some of the virtual simple shear mechanisms undergo loading whereas others undergo unloading. This process of fabric evolution is the primary cause of noncoaxiality between the axes of principal stresses and strains. Although cyclic behavior and behavior under the rotation of the principal stress axis seem to originate from two distinct mechanisms, the strain space multiple mechanism model demonstrates that these behaviors are closely related through the hysteretic damping factor. Copyright (C) 2011 John Wiley & Sons, Ltd.

DOI： 10.1002/nag.1091

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

&nbsp;In order to verify the applicability of strain space multiple mechanism model based on finite strain (both total Lagrangian (TL) and updated Lagrangian (UL)) formulations, seismic response analyses are performed on Breakwater No.7 in Kobe Port during 1995 Hyogoken-Nanbu earthquake. Both infinitesimal and finite deformation analyses are performed to examine how the effect of geometrical nonlinearity affects the analytical results. As an input dilatancy parameter in the model, two types of undrained shear strength (20 kPa and 40 kPa) are adopted according to the results of undrained triaxial compression tests. The settlements at the top of the caisson in the infinitesimal deformation analyses are 3.62 m and 2.89 m for the undrained shear strength of 20 kPa and 40 kPa, both of which exceed the upper limit of measurements (2.6 m). In contrast, the computed settlements in the TL/UL formulations with the undrained shear strength of 20 kPa and 40 kPa are 2.46/2.46 m and 1.93/1.88 m, respectively, both of which fall inside the measured range (between 1.4 and 2.6 m). The results confirm that the TL and UL formulations are numerically equivalent and the effect of geometrical nonlinearity has to be accurately considered in predicting the seismic response of port structures such as breakwaters.

DOI： 10.2208/jscejseee.69.I_385

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Language：English   Publishing type：Research paper (scientific journal)  

Because low-compacted trench backfill around a manhole is normally liquefiable, the manhole could suffer uplift damage associated with soil liquefaction during a strong earthquake. In this study, 22 dynamic centrifuge models were tested to investigate the response of a buried manhole subjected to a dynamic load. The models were tested under 20g, and a substitute pore fluid was used to avoid the scaling law conflict between the dynamic and diffusion processes. It was found that excess pore water pressure is one of the contributing factors to the magnitude of the manhole uplift. Using this result, new mitigation methods against the uplift in liquefied ground were developed. Their effectiveness was also examined through the tests. A model manhole mitigated with the proposed methods was tested alongside regular model manhole. From the test results, the magnitude of manhole uplifts with the mitigation methods decreased as buildup of the excess pore water pressure was restrained in high-compacted backfill or excess pore water was dissipated into the manhole during strong shaking. © 2013 American Society of Civil Engineers.

DOI： 10.1061/(ASCE)GT.1943-5606.0000769

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Language：Japanese  

The geotechnical centrifuge at the Disaster Prevention Research Institute, Kyoto University was renewed two years ago. Consequently, the rigidity of the main frame of the device had improved. However, some problems emerged by subsequent use. The 1st problem was that the rigidity of the platform part of the device was low. The 2nd one was that the fixed system of the platform part adopted did not function. The 3rd one was that vibration of the up-and-down direction in the shaking table occurs when dynamic centrifuge tests were. In order to solve those problems, the platform part was renewed last year to what has high rigidity, and the fixed system was also changed. In the present study, we investigated the dynamic characteristics of the shaking table and the platform part by measuring the vibration when dynamic centrifuge tests were. As a result, it was found that the causes of vibration of the up-and-down direction were the structure of the shaking table and the control signal called "DITHER". Additionally, it compared with the result when not fixing a platform part. Based on the comparison results, it is suggested that it be used without fixing the platform part.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ASCE-AMER SOC CIVIL ENGINEERS  

A simple method to predict the uplift displacement of a manhole and trench-backfill settlement due to liquefaction is proposed. The conventional equilibrium of vertical forces acting on a manhole is solely a function of such forces acting and is incapable of predicting the uplift displacement. In this paper, the proposed method adds variables including the uplift displacement, Delta f, and settlements of backfill, Delta s, under the condition that the volume of an uplifted portion of a manhole is equal to a settled volume of a trench-backfill. To date, the method is verified through comparison with the results of 1-G and centrifuge model tests. A new safety factor, which takes into account the amount of manhole uplift and backfill settlement, is also derived. DOI: 10.1061/(ASCE)GT.1943-5606.0000615. (C) 2012 American Society of Civil Engineers.

DOI： 10.1061/(ASCE)GT.1943-5606.0000615

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Language：Japanese   Publisher：The Japanese Geotechnical Society  

This paper reports geotechnical damages in the northern area of Miyagi prefecture caused by the 2011 off the Pacific coast of Tohoku Earthquake on March 11, 2011. A joint reconnaissance team organized by Tohoku branch and Kansai branch of the Japanese Geotechnical Society carried out extensive field surveys in the area from April 5 to 10 and from April 29 to 30, 2011. This paper consists of the main results from these surveys and subsequent researches on the damage such as failure of river embankments and coastal levees, coastal erosion caused by tsunami, damage of port and harbor facilities, failure of cut and banked slopes of roads and railroads, and occurrence of liquefaction and subsidence. Although some results have already been reported as news flash to the Journal of the Japanese Geotechnical Society, this paper provides inclusive summaries and more detailed investigations on the damage in the northern area of Miyagi prefecture. In separate sections of this paper, outlines of the damage in each object are briefly summarized, and then several typical damage cases are presented and these mechanisms are discussed in detail.

DOI： 10.3208/jgs.7.37

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Language：Japanese  

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Other Link： http://hdl.handle.net/2433/171985

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ICE PUBLISHING  

To verify and find issues on the generalised scaling law for dynamic centrifuge tests, a series of centrifuge model tests are conducted under the scheme of the modelling of models technique. In a series of dynamic tests on a flat, saturated sand layer, four different centrifugal accelerations from 5 g to 70 g are applied to the scaled models for which the prototype is uniquely given. With the scaling law, the prototype is scaled down to 1/100. The models are exposed to sinusoidal input accelerations with 0.65 Hz and amplitudes of 2.1 m/s(2) and 3.1 m/s(2) in prototype scale. For response during shaking, nearly identical accelerations and excess pore-water pressure build-ups are recorded for all the cases in the prototype scale. Discrepancies are found on surface settlements and duration time for dissipation of excess pore-water pressure. The major cause of the discrepancy may be the small value of the shear modulus induced by the low confining stress in model ground under low centrifugal acceleration.

DOI： 10.1680/ijpmg.2011.11.4.138

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Language：Japanese  

The geotechnical centrifuge at the Disaster Prevention Research Institute, Kyoto University was renewed two years ago. Consequently, the rigidity of the main frame of the device had improved. However, some problems emerged by subsequent use. The 1st problem was that the rigidity of the platform part of the device was low. The 2nd one was that the fixed system of the platform part adopted did not function. The 3rd one was that vibration of the vertical direction in the shaking table occurs when dynamic centrifuge tests were. In order to solve those problems, the platform part was renewed last year to what has high rigidity, and the fixed system was also changed. In the present study, we investigated the dynamic characteristics of the shaking table and the platform part by measuring the vibration when dynamic centrifuge tests were. As a result, it was found that the causes of vibration of the vertical direction were the structure of the shaking table and the control signal called "DITHER". Additionally, it compared with the result when not fixing the platform part. Based on the comparison results, it is suggested that it be used without fixing the platform part.

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Other Link： http://hdl.handle.net/2433/161853

Language：English  

To verify the generalized scaling law, dynamic centrifuge tests under two different centrifugal accelerations of 25 g and 50 g are conducted. The model ground constitutes of a flat dry sand layer. With the scaling law, a prototype ground is scaled down to 1/100. A sinusoidal input acceleration of frequency 1.0 Hz, maximum amplitude 0.5 g, and duration 14 sec in prototype scale is applied to the model ground. Each model is exposed to the identical input motion sequentially 10 times. In total nine accelerometers are installed in the model. Surface settlements are measured by laser displacement transducers. Settlements at three different depths (300, 200 and 50 mm - model scale - from the surface) are measured by settlement gauges. Measured settlements after the initial shake in prototype scale show agreements between the two models when the intensity of shaking is nearly identical.

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Other Link： http://hdl.handle.net/2433/161854

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japanese Geotechnical Society  

The uplift behavior of sewage manholes due to liquefaction in a trench is investigated through a series of dynamic centrifuge model tests. The objectives of a series of tests are to study the mechanism of the uplift and to obtain relationships among uplift displacement and factors affecting the uplift. The factors considered in the experiments are the ground water levels, the magnitude of input accelerations, the duration time of shaking, the relative densities of trench backfill and the native ground, the material of native ground, the volume of a trench, the apparent unit weight of a manhole, and the contact conditions at the bottom of a manhole. Test results show that the primary cause of uplift is the reduction of the effective confining stress near the bottom of a manhole due to strong shaking. The magnitude of uplift is found to be strongly correlated with the ground water depth, the intensity of shaking, the shear deformation of the trench, and the contact conditions at the bottom of the manhole. These findings are believed to be useful for engineering practice in the mitigation of the manhole uplift.<br>

DOI： 10.3208/sandf.51.1091

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Language：English   Publisher：Japan Society of Civil Engineers  

This paper presents the results of a numerical investigation conducted to study the effect of vertical loads on lateral response of a free head and a capped pile group in sand. A coupled soil-pile system is idealized through 2D finite elements with soil models idealized by a hyperbolic type multiple shear mechanism. The analysis focuses on the five piles in the middle row of a 3x5 pile group spaced at 3.92-pile diameters. The interaction between a pile and the surrounding soil in the 3D type is idealized in the 2D analysis using soil-pile interaction springs with a hysteretic non-linear load displacement relationship. The presence of vertical loads on free head piles increases the confining pressures in the sand deposit confined by the piles but the rate of increase in those outside the group is relatively small, resulting in the difference in a balance of lateral soil pressures acting at the back of and in front of individual piles. A vertical load applied to a group pile with a uniform vertical displacement of 0.1 pile diameter decreases the lateral resistance of the leading pile (pile 1) by 10 % and increases the lateral resistance of piles 3 and 5 by 14 and 35 %, respectively. The same trend with higher percentages of increase or decrease is observed in the capped pile group case.

DOI： 10.2208/jscejam.67.I_271

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Language：English   Publisher：Japan Society of Civil Engineers  

The non-linear response of coupled soil-pile-structure systems to seismic loading is parametrically studied in the frequency domain using two-dimensional (2D) finite elements (FE). The soil-pile interaction in three dimensions (3D) is idealized in the 2D type using soil-pile interaction springs with non-linear hysteretic load displacement relationships. The system under investigation comprises of a single degree of freedom structure supported by an end-bearing single pile founded in a homogenous sand layer over rigid rock. Comparisons with established results from the literature suggest that the adopted FE model reasonably captures the essential features of the seismic response of the coupled soil-pile-structure system. Numerical results demonstrate the strong influence on the effective natural period of the foundation properties. The effect of non-linear soil behavior and soil profile as well as the frequency content of excitation on both kinematic and inertial interactions is illustrated. The relative contributions of kinematic and inertial interaction to the development of dynamic pile bending are clarified.

DOI： 10.2208/jscejam.67.I_471

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Language：Japanese  

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：CANADIAN SCIENCE PUBLISHING, NRC RESEARCH PRESS  

La performance d&apos;un groupe de pieux charge lateralement a permis d&apos;etudier l&apos;effet de la separation sol-pieu. Des essais a l&apos;echelle reelle, qui consistaient en une combinaison d&apos;un pieu unique et d&apos;un groupe de 3 5 pieux soumis a des charges laterales statiques et dynamiques, sont une occasion unique et permettent d&apos;effectuer une etude rigoureuse sans avoir recours a un retro-ajustement des parametres de facon arbitraire. Le systeme couple sol-pieu est represente par des elements finis en deux dimensions, et les modeles de sols sont representes par un mecanisme de cisaillement multiple de type hyperbolique. Des elements de ressorts non lineaires sont utilises pour representer l&apos;interaction sol-pieu par une relation de deplacement de charge non lineaire et hysteretique. Des elements de joints, avec un mecanisme de contact-separation, sont utilises pour representer l&apos;effet de separation a l&apos;interface sol-pieu. Le fait d&apos;ignorer la separation sol-pieu lors d&apos;essais statiques surestime la capacite ultime de support de charge laterale par 43% pour un pieu unique, et par 73% pour le dernier pieu dans un groupe de pieux rapproches. De plus, si l&apos;on neglige la separation sol-pieu lors d&apos;essais dynamiques, on surestime la courbe de chargement-deflection totale du groupe, autant pour la phase de chargement que la phase de dechargement.

DOI： 10.1139/T10-026

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SEISMOLOGICAL SOC AMER  

During the 2008 Iwate-Miyagi Nairiku, Japan, earthquake (M(w) 6.9), an unprecedented vertical surface acceleration of nearly four times gravity, was measured at the KiK-net, IWTH25 station located 3 km southwest of the epicenter. The station is equipped with three-component accelerometers, installed at both the free surface and the bottom of a 260-m borehole. The waveform of the vertical acceleration shows a clearly asymmetric form with large amplitude in the upward direction. Aoi et al. (2008) reported and qualitatively explained the mechanism of this phenomenon by the analogy of bouncing a piece of matter on a trampoline; thus, they called it the trampoline effect. To study this recently discovered nonlinear behavior of the surface ground motion, numerical analysis with a two-dimensional finite-element method has been conducted with parameters derived from the borehole data at the station. The analysis successfully simulates the asymmetric vertical motion. Results indicate that the asymmetric motion may be characterized by the existence of a lower bound of negative acceleration, which in most cases corresponds to the acceleration of gravity and high positive pulses caused by the compression stress of the disturbed surface ground material.

DOI： 10.1785/0120090301

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Language：English   Publisher：wiley  

DOI： 10.1002/nag.899

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Language：English  

A series of centrifuge model tests are conducted under the scheme of the modeling of models technique to find issues on the generalized scaling law for dynamic centrifuge tests (Iai et al., 2005). In a series of dynamic tests on a flat, saturated sand layer of 1/100 scale, four different centrifugal accelerations from 5 g to 70 g are employed on the scaled models for which the prototype is uniquely given. The models are exposed to sinusoidal input accelerations with 0.65 Hz and amplitudes of 2.5 m/s2 and 3.1 m/s2 in prototype scale. For response during shaking, nearly identical accelerations and excess pore-water pressure buildups are recorded for all the cases in the prototype scale. Discrepancies are found on surface settlements and duration time for dissipation of excess pore-water pressure. The major causes of the discrepancy may be (1) the duration time for the initial consolidation, (2) small value of the shear modulus due to low confining stress in model ground under low centrifugal acceleration, and (3) reduced permeability due to adsorption of viscous fluids on sand particles.

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Language：Japanese  

The strain space multiple mechanism model idealizes the behavior of granular materials based on a multitude of virtual simple shear mechanisms oriented in arbitrary directions. These mechanisms idealize the internal (or micromechanical) structure of granular materials with induced anisotropy and form a second order fabric tensor, which relates macroscopic strain to macroscopic stress. Within this framework, the strain space fabric is defined as a projection of the macroscopic strain field onto an individual virtual simple shear mechanism oriented in arbitrary directions and represents the measure of mobilization of micromechanical strain due to the relative displacements between the particles. The strain space fabric, which is shaped like a four leaf clover in two dimensions, induces another fabric in stress space through a hyperbolic function, which governs the virtual simple shear mechanisms. Comparison with Discrete Element Method (DEM) simulation suggests that the strain space multiple mechanism model has the potential to capture the essential features in the evolution of an induced fabric in granular materials.

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Other Link： http://hdl.handle.net/2433/151068

Language：English  

A series of systematic centrifuge tests is conducted in order to study the seismic response of end bearing single piles embedded in a dry dense sand layer and supporting single or double degree of freedom structures. The model is excited with and without structures using 12 sinusoidal waves as input base accelerations with constant amplitudes of about 1.5 m/s2 and varying frequencies ranging from 1 to 12 Hz. All the tests are conducted with the centrifugal acceleration of 40G. The obtained results provide a clear insight as to the distinct role of inertial and kinematic interactions as well as the combined effect of these two interactions on the motion of the pile head by identifying the fundamental frequencies that dominate the response not only for single degree of freedom structure but for double degree of freedom as well. The role of the frequency content of the input motion on the development of kinematic and inertial dynamic pile bending is also investigated.

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Other Link： http://hdl.handle.net/2433/151066

Language：Japanese  

Results of site investigation after the 2011 off the Pacific coast of Tohoku Earthquake occurred on March 11 , 2011 are reported. The investigation focused on port faclities, river dykes, andliquefaction-induced damages in the northern Miyagi prefecture and Ibaragi prefecture. Substantial damage caused by liquefaction was found as well as damage caused by the tsunami.

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Other Link： http://hdl.handle.net/2433/149602

Language：English   Publishing type：Research paper (scientific journal)   Publisher：SEISMOLOGICAL SOC AMER  

In this article, data were collected from the Chiba dense array, which consists of 44 accelerometers with interstation spacing in the range of 5-300 m that are employed to estimate the torsional ground motion. The geodetic method was used to estimate torsional motions from the translational records in the Chiba dense array. The translational and computed torsional motions were then applied to the building models with different structural characteristics to evaluate the effectiveness of the accidental eccentricity levels proposed in various design codes. The results of analysis suggest that the 5% accidental eccentricity is on the safe side for most periods of interest in engineering practice. However, in the case of stiff structures (with periods shorter than 0.3 sec), an increase of up to four times in building displacement is observed by including the torsional excitation. Furthermore, we found that the accidental eccentricity coefficient increased up to 0.6 at periods shorter than 0.3 sec, which is 12 times larger than what is proposed by the codes.

DOI： 10.1785/0120080196

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Seismic response of end bearing piles supporting simple structures founded on a homogeneous dense sand layer over rigid rock is studied using a geotechnical centrifuge at DPRI-KU. Experiments are carried out under the centrifugal acceleration of 40G. The pile foundation is excited by a shaking table at the pile tip with and without the superstructure using sinusoidal waves with different amplitudes and different frequencies to investigate the inertial effect of the superstructure on the pile response. Nonlinear dynamic analyses using the 2-D finite element (FE) method are compared to the recorded responses during shaking in the centrifuge. The soil-pile interaction in 3-D is idealized in 2-D type using soil-pile interaction springs with hysteretic nonlinear load displacement relationships. Computed time histories of pile head acceleration and displacement, except for bending moment, were consistent with those obtained from experiments. Numerical analysis tends to under-estimate the maximum value of the bending moment, because of the empirical procedure for the setting of soil-pile interaction springs.

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Other Link： http://hdl.handle.net/2433/129397

Language：Japanese   Publisher：社団法人地盤工学会  

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10419628

Language：Japanese   Publisher：地盤工学会  

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Language：English   Publishing type：Research paper (international conference proceedings)  

Dynamic behavior of a pile group is simulated by a two-dimensional finite element analysis. Results of the full-scale lateral-load tests of a 3 × 5 pile group conducted in the Salt Lake City International Airport site are compared with the simulation. The soil profile at the test site generally consisted of cohesive sandy silt and silty sand. Closed-end steel pipe piles were driven to a depth of 11.6 m. Pile head was rotation free. Dynamic lateral loads were applied to pile head with the statnamic device. To conduct numerical analysis, model parameters for soils are taken from the geotechnical investigation data at the test site. Response of five piles in the middle of the 3 × 5 pile group are simulated. Measured dynamic loads are applied at the pile head. Overall load-deflection behavior of the pile group agrees well with the measured ones. Some discrepancies are found on the bending moment profile. In the full-scale dynamic tests, peak moments for larger target deflections occurred at the same depths for all piles, while in computation, the peak moment occurs with greater depths as target deflection increases. Numerical analysis overestimates the group effects in dynamic tests. This calls up further improvement of a numerical modeling. © 2008 ASCE.

DOI： 10.1061/40975(318)138

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Uplifting of sewage manholes is one of the typical and striking damage pattern observed in the area being hit by large earthquakes. A simplified method to estimate the maximum uplift displacement of a manhole and settlements of backfill soil under liquefaction is derived based on the mechanism of uplift of a manhole under undrained condition of backfill soil. The method is capable of evaluating effectiveness of countermeasures against uplift by considering excess pore water pressure ratio and/or unit weight of backfill soil. In the present study, the applicability for the case without countermeasures is investigated through comparison with experimental results. Results show that measured uplift displacements and settlements are within the range predicted by the proposed method.

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Other Link： http://hdl.handle.net/2433/129311

Language：Japanese   Publisher：沿岸技術研究センター  

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Many types of damage of buried structures occur due to liquefaction during an earthquake, such as flotation, settlement, bending and buckling of buried pipes. Among those, this paper focuses only on uplift of sewerage manholes. Uplift behavior of buried structures with and without a measure for uplift is investigated in model tests which are dynamically tested in a centrifuge modeling. In this study, effectiveness of the new measure for uplift which is to dissipate the excess pore water pressure is investigated to mitigate uplift displacement of the manhole during earthquakes (Konishi et al. 2008). The measure consisted of two configurations which are a filtering net and pipe. The tests showed that the mechanism of the uplift behavior and the effects of the measure for the uplift, but the uplift amount may be still too large (8% of the length of the manhole) when it is applied in practice.

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Other Link： http://hdl.handle.net/2433/129307

Language：English   Publishing type：Research paper (international conference proceedings)  

This paper describes an emerging methodology for seismic evaluation and design of port structures. The methodology is based on minimum life-cycle cost principle through probabilistic evaluation of performance. While conventional seismic design of port structures are based on a particular return period specified for design, the methodology based on life-cycle cost allows for consideration of ground motions with all (or varying) return periods and uncertainty in geotechnical conditions. The methodology based on life-cycle cost also allows the probability of failure being evaluated rather than prescribed by an authority. Since ordinary port structures are for commercial use, the method based on the life-cycle cost has potential advantages over conventional design. An example is presented. In particular, the simplified design charts that are based on a series of parametric studies of effective stress analyses have great benefit for implementing the proposed methodology in practice. Apart from the ordinary port structures, higher priority should be assigned for safety as a performance objective. This issue is especially relevant if port structures are essential parts of post-earthquake emergency strategies for recovery and restoration of urban areas. The paper also discusses the importance of this issue and the future direction of study. © 2008 ASCE.

DOI： 10.1061/40975(318)198

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Uplifting of sewage manholes is one of the typical and striking damage pattern observed in the area being hit by large earthquakes. A simplified method to estimate the maximum uplift displacement of a manhole and settlements of backfill soil under liquefaction is derived based on the mechanism of uplift of a manhole under undrained condition of backfill soil. The method is capable of evaluating effectiveness of countermeasures against uplift by considering excess pore water pressure ratio and/or unit weight of backfill soil. In the present study, the applicability for the case without countermeasures is investigated through comparison with experimental results. Results show that measured uplift displacements and settlements are within the range predicted by the proposed method.

DOI： 10.2208/journalam.11.587

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A large earthquake occurred (Mj 6.8, D=17km) at 10 : 13 AM on July 16, 2007 in Chuetsu region, Niigata, Japan. The epicenter was located offshore of Kariwa village and Kashiwazaki city. Preliminary results of the source inversions indicate a reverse fault with the NE-SW (strike : 34, Dip : 51, Rake : 74 degrees). The instrumental JMA seismic intensity was 6+ (IX in MMI) in Kariwa village, Kashiwazaki city, Nagaoka city in Niigata prefecture, and lizuna-machi in Nagano prefecture. Eleven people were killed, more than 1, 813 were injured, and more than 10, 000 were evacuated (as of 7/23/07, Niigata Prefecture). The number of totally collapsed houses was 961 in Niigata. Major lifelines, gas, water, and electricity, have been damaged and suspended for more than a day. In Kariwa village, one of the world largest nuclear power plants (7 reactor's total 8, 200, 000kW) reportedly suffered damage due to unexpectedly large strong shaking.

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10752269

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A major earthquake (Mj 6.9, 37°13.2'N, 136°41.1'E, Depth 11km) occurred on March, 25, 2007, at 9:42PM (local time) near Noto Peninsula, Ishikawa Prefecture, Japan. The JMA seismic intensity of 6+ was recorded in Wajima city, Nanao city, and Anamizu-Machi. One person was killed, more than 318 were injured. The number of totally collapsed houses were nearly 600, and partially collapsed houses exceeded 1,200 (as of May 9, 2007). Strong shaking triggered damage of lifeline systems, road embankments, settlements and tilting of port facility, and slope failures of cliffs near the sea. This paper mainly reports characteristics of strong shaking, and damage on roads and port facility.

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Other Link： http://hdl.handle.net/2433/171970

Language：Japanese   Publisher：The Japanese Geotechnical Society  

A destructive earthquake (Mw 6.6) occurred on December 26, 2003, at 7:56GMT (5:26AM local time), near the city of Bam located southeastern part of Iran. To investigate local site effects observed in the first reconnaissance, second investigation was conducted with seismic refraction method to study the relationship between surface ground condition and damage distribution. Results show that variation of P wave velocity structure near the ground surface may have some influence on damage distribution in the city.

DOI： 10.3208/jgs.2.51

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Numerical analysis for interaction between soil and pile group is performed using finite element method with 2D modeling. Results of numerical analysis are compared with the full-scale statnamic test of a 3 x 5 pile group conducted in the Salt Lake City International Airport site. In the numerical analysis of the pile group, there are two cases. The first case is that dynamic loads without cycle static loads. The other is that static loads prior to dynamic loads were applied at the group pile. In results, load versus deflection curves and bending moment versus depth are compared with the measured ones. Also, when numerical analysis includes the static loading before the dynamic loading (Case 2), the load-deflection curves were larger than measured ones but agree better than that of Case 1.

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Other Link： http://hdl.handle.net/2433/73396

Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：SPRINGER  

The paper discusses the emerging trends in seismic analysis and design of geotechnical structures. Soil consists of soil particles. The fundamental study on this aspect of soil has come to the stage where the results of the study can be readily incorporated as an essential part of seismic analysis of soil-structure systems. Geotechnical earthquake engineers and researchers are encouraged to look into this fundamental study. By expanding the concept of performance-based design, a paradigm shift can be achieved from construction-oriented to service-oriented approach. The service-oriented approach will open a new horizon for design and promote the holistic approach for providing better designed built-environment. Designing a large urban area against combined hazards, such as those caused by the Sumatra earthquake of 2004, poses a new challenge in seismic design. The approach that is most appropriate for a large urban area may be different from those used for the current practice design used for individual structure and should be newly developed. These emerging trends in seismic design have to be extensively studied and carefully applied in practice, especially for designing new and large geotechnical structures that have to meet the rapidly growing social and economic demands in Asia and those for redevelopment of urban areas around the world.

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The paper proposes a new stress-dilatancy relationship that will be incorporated into a strain space multiple mechanism model for cyclic behavior of sand. The proposed relationship is based on the hypothesis that the dilative component of dilatancy represents the mechanism that consumes no energy, whereas the contractive component of dilatancy is in proportion to the cumulative shear strain. An example of cyclic behavior of sand simulated by the proposed model is given to demonstrate the capability of the model.

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Other Link： http://hdl.handle.net/2433/73402

Language：Japanese   Publisher：土質工学会  

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Language：English   Publisher：Japan Society for Natural Disaster Science  

One of the largest earthquakes in our history occurred at 7:58AM (local time) on December 26 2004, off the west coast of Northern Sumatra Island, Indonesia (M_w 9.3). The earthquake triggered a huge tsunami along the coastlines of the Indian Ocean and caused a huge number of casualties. From March 1 to 6, 2005, reconnaissance was conducted in the region of Banda Aceh and Meulaboh, Indonesia, where strong shaking and tsunamis were observed. The primary objective of reconnaissance was to investigate and record damage mainly due to strong motions and to estimate the seismic intensity in the region. This paper reports on the damage to earth structures, waterfront structures, and roads washed away by tsunamis. Eyewitness evidence of liquefaction in Banda Aceh, about 250 km away from the epicenter, was likely caused by the strong shaking of M_w 9.3. In Kuala Bubon village located about 15 km north of Meulaboh, settlements of embankments attached to bridge abutments collapsed just after the earthquake and before the arrival of the tsunami, so villagers could not use motorcycles or bicycles to evacuate. Lessons must be learned from this devastating earthquake, and disaster mitigation improved.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：THOMAS TELFORD PUBLISHING  

The trend toward physical modelling of larger prototypes triggers a move towards expansion of the current capability of dynamic centrifuge tests. In this paper a method based on the concept of two-stage scaling is proposed that allows expanded use of the currently available facilities. In the first stage a prototype is scaled down into an intermediate virtual model based on the scaling relations in a 1g field with a scaling factor of mu (prototype/virtual model). In the second stage this model is scaled down into a physical model using the conventional scaling relations in the centrifugal field with a scaling factor of eta (virtual model/physical model). In this manner, a large scaling factor lambda = mu eta (prototype/physical model) can be broken down into the smaller scaling factors mu and eta, and thus the centrifuge model tests can be performed with the smaller scaling factor eta. In effect, the limits in the scaling factor for the currently available centrifuge facilities can be expanded by a factor of mu. Validation of the proposed method is provided by algebraic derivations based on the mechanics of model tests.

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A major earthquake (M 6.8, 37.289 N, 138.870E, Depth 13km) occurred on October 23, 2004, at 5 : 56PM (local time) near Ojiya City, Niigata Prefecture, Japan. The JMA seismic intensity of 7 was recorded in Kawaguchi-machi for the first time after seismic intensity meters were installed. Aftershocks with the JMA seismic intensity scale of more than 5 minus had been measured for more than two weeks in the affected area. Forty people were killed, more than 4,500 were injured and more than 100,000 were evacuated for days. The number of totally collapsed houses exceeded 2,800. Strong shaking triggered more than 1,600 landslides, and some of them blocked up river channels in mountain area. The earthquake also caused major damage on civil structures. The Joetsu Shinkansen bullet train was derailed for the first time in its history of 40 years. The number of passengers was 151 and miraculously no one was injured.

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Other Link： http://dl.ndl.go.jp/info:ndljp/pid/10751915

Publisher：Japan Society of Civil Engineers  

Behind the damage due to the devastating tsunami after the 2004 Sumatra-Andaman earthquake, it was not clear how much damage was caused by the strong motion of magnitude 9.3 earthquake. To investigate this reconnaissance was carried out after two months of the event. Damage to the ground including liquefaction, earth structures, and port facility are reported. The investigated areas were Banda Aceh and Meulaboh where the closest city from the epicenter in west coast of the Sumatra Island.

DOI： 10.11532/proee2005.28.211

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Publisher：Japan Society of Civil Engineers  

The paper reports a series of centrifuge model tests on uplift behavior of manhole in liquefiable deposit. A total of six cases of model tests are reported where density of the model deposit and intensity of input accelerations are varied. Measured excess pore water pressures around the manhole model are used for computing safety factor against the threshold level for uplift. The computed safety factor and the degree of measured uplift are not consistent with each other, implying that deformation analysis such as through finite element method may be important to evaluate the degree of uplift of manhole in liquefiable deposit.

DOI： 10.11532/proee2005.28.4

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Dynamic centrifuge tests under 50 G and effective stress analyses (FLIP) were conducted to study the dynamic behavior of an embankment whose prototype height is 3 m. The embankment made of dry sand was constructed on the saturated sand layer whose relative density was adjusted to either 30% or 70%. Sinusoidal input motions with three different levels of peak acceleration amplitude were given. Objective of the study is to investigate the relationship between the magnitude of settlements and the peak amplitude of input acceleration.

DOI： 10.11532/proee2005.28.37

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Language：Japanese   Publisher：Disaster Prevention Research Institute Kyoto University  

Two dimensional model tests are performed on a horizontal cross section of a soil-pile system in a pile foundation. The objective of the model tests is to evaluate local soil displacement field in the vicinity of the piles associated with a global displacement of soil around the pile foundation. Two dimensional effective stress analyses in horizontal plane are also performed to generalize the findings from the model tests. An effective stress model based on multiple shear mechanism is used through a computer code FLIP. In dry condition, displacement vectors are directed away from pile front, and displacement at pile side rapidly decreases with an increasing distance from soil pile interface. In undrained condition, displacement field shows vortexes at pile side associated with push-out/pull-in pattern of displacements in front of and behind the pile. Distribution of local soil displacement between piles shows high strain concentration at soil-pile interface.

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Other Link： http://hdl.handle.net/2433/26627

Language：Japanese  

A destructive earthquake (M_W 6.6) occurred on December 26, 2003, at 7:56 GMT (5:26AM local time), near the city of Bam located southeastern part of Iran. There is the Bam fault just 2 km away from the city, which might be activated for the first time in several thousand years. The focal depth is estimated to be 8 to 10 km and the focal mechanism is reported to be dextral strike-slip with small vertical component. Strong motions were recorded in the city, about 14 km from the epicenter. The maximum peak ground acceleration was 1.0g in vertical, and 0.81g and 0.65g in horizontal components. The number of victims due to the earthquake exceeded 40,000 as of Feb. 26, 2004. A major cause of death could be crashed or hit by the debris while sleeping due to the collapse of housings. The earthquake also destroyed the historical mud brick complex, "Arg-e-Bam" which is more than 1,500 years old.

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Other Link： http://hdl.handle.net/2297/23573

Language：English   Publisher：Disaster Prevention Research Institute Kyoto University  

Effective stress analyses are performed on seismic response of underground structures subjected to strong earthquake motions. The model of sand used for the analysis is based on the multiple shear mechanism. The seismic response data analyzed are based on the 30g centrifuge tests of an underground reinforced concrete (RC) box culvert, 9 m high and 12 m wide, buried at the bottom of saturated and dry model ground 16 m deep in prototype scale. Subject to a strong earthquake motion with a peak acceleration of 0.8 to 0.9g in prototype scale, earth pressures acting on the sidewalls of the RC structure increased after shaking in both saturated and dry model grounds. These earth pressures together with the effect of the lateral displacement due to shaking result in yielding of the side RC walls. The portion of the RC walls that are put into yielding is larger in saturated model ground than in dry model ground. The effective stress analyses are capable of capturing the essential features of the response of underground structures.

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Other Link： http://hdl.handle.net/2433/26518

Language：English  

Results of a series of centrifuge experiments to study the dynamic response of pile foundations under lateral spreading were compared to the results of numerical analysis. Experiments were carried out under the centrifugal acceleration of 40 G. Piles in the model foundation were lined up 3 by 3 pattern with a spacing of three pile diameter, and both pile head and bottom were rotation fixed. Piles were placed in the inclined ground of saturated sands and applied lateral loads due to the ground deformation. The effective stress finite element analysis was conducted to simulate these experiments. Computed time histories of pile head acceleration and displacement were consistent with those obtained from experiments. However, much smaller surface ground deformation in simulation might cause small amplitude of bending moments. Some calibration in the numerical modeling may be required to have more consistent results on bending moments.

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Urban development rapidly expanding from lowland to surrounding hills and mountains poses increasing risks in geo-hazards, including liquefaction during earthquakes, and failure of artificial and natural slopes. Objective of this study is to develop methodologies for assessing vulnerability to these hazards, and technologies for improving the performance of geotechnical works in urban areas. This paper summarizes the results of the study with respect to (1) performance of retaining walls at waste fill in waterfront areas, (2) hazard mapping of natural slope failures through monitoring using laser scanners, and (3) hazard assessment of residential areas in valley fills and hills.

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Other Link： http://hdl.handle.net/2433/129023

Language：Japanese  

Centrifuge experiments of static and dynamic lateral loading of pile group are carried out. Asteel pipe whose diameter is 30 cm and length 10 m is scaled down to 1/20 for static tests, and1/40 for dynamic tests. It is experimentally shown that in the dynamic tests the hysteresis loopof inertial force and displacement at the pile head becomes elliptical due to the phase differencebetween pile and the ground, and/or the nonlinear property of sands. Even in the case ofdynamic tests under saturated condition, group pile behavior may be observed.

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Other Link： http://hdl.handle.net/2433/129251

Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS38.0.1441.0

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Language：Japanese   Book type：Scholarly book

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This paper compares experimental results from every facility for LEAPUCD-2017. The specified experiment consisted of a submerged medium-dense clean sand with a 5-degree slope subjected to 1 Hz ramped sine wave base motion in a rigid container. The ground motions and soil density were intentionally varied from experiment to experiment in hopes of defining the slope of the relational trend between response (e.g., displacement, pore pressure), intensity of shaking, and density or relative density. This paper is also intended to serve as a useful starting point for overview of the experimental results and to help others find specific experiments if they want to select a subset for further analysis. The results of the experiments show significant differences between each other, but the responses show a significant correlation, R2 ~ 0.7-0.8, to the known variation of the input parameters.

DOI： 10.1007/978-3-030-22818-7_4

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Language：Japanese   Publisher：電気評論社  

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Other Link： http://hdl.handle.net/10112/10712

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Kumamoto earthquake occurred in Kyushu Island, which is located at the south part of Japan, at 1:25 am on 16th April in 2016. The magnitude of the biggest earthquake was M7.3 and a lot of buildings and civil structures were damaged and collapsed due to the shaking generated by the sliding active fault overlain across the middle part of Kyushu Island. This paper shows the report of the site investigation performed at Mashiki-machi, Nishihara-mura and Minamiaso-mura in the term of 7th-8th in May.

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Other Link： http://hdl.handle.net/2433/217308

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Language：Japanese   Publisher：総合土木研究所  

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Other Link： http://hdl.handle.net/2433/171967

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Language：English   Publisher：CRC PRESS-TAYLOR & FRANCIS GROUP  

Iai et al. (2005) proposed a procedure of two-stage scaling for dynamic centrifuge tests to study the behavior of large geotechnical structures in the existing research facilities which allows high geometric scaling factors by superposition of scaling laws for centrifuge tests with those for 1 g shaking table tests. A series of tests on saturated sand deposits is conducted to verify the applicability of this approach. Seven different combinations of scaling factors and centrifugal accelerations up to 70 g are applied to scale the same prototype by 1/100. The models are exposed to sinusoidal input accelerations with 0.65 Hz and amplitudes of either 4.7 m/s(2) or 2.1 m/s(2) in prototype scale. The two-stage scaling approach is verified for the buildup of excess pore water pressure. During the dissipation of pore water pressures after shaking, limitations seem to arise concerning ground settlements and when low levels of centrifugal accelerations are applied.

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Centrifuge model tests are conducted to investigate the mechanism of uplifting of buried underground structures, in particular in this study, manholes. Model manholes made of closed-end aluminium cylinders are buried in a trench filled with loose saturated sand. The model is fully equipped with accelerometers, pore pressure transducers, and laser displacement transducers. The experiment is carried out under 20 g. A sinusoidal input motion was employed to investigate the uplifting mechanism under simple conditions. Results show that the amount of uplift is proportional to amplitudes of input acceleration, and the amount depends both on the ground water levels and density of backfill. A simple and quantitative method for estimation of the maximum uplift displacement proposed by the authors is verified with the results of model testing.

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The effect of vertical loads on the lateral response of group pile is studied on the basis of soil-pile interaction nature. Coupled soil-pile system is idealized through two dimensional finite elements with soil models idealized by multiple shear mechanism of hyperbolic type. The developed numerical model has been verified by comparing the results with full scale pile group test results. Through comparative studies, it has been found that for a single pile and at a given lateral load, the lateral deflection decreases with the combination of vertical load. For the group pile, the vertical load effect depends basically on pile position and pile spacing to diameter ratio. © 2009 IOS Press.

DOI： 10.3233/978-1-60750-031-5-1251

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Applicability of the two stage scaling relationship called generalized scaling law for centrifuge tests proposed by Iai et al. (2005) is investigated for dynamic response of flat layered media. In this scaling law, recorded physical model parameters are, firstly, converted to those in the virtual 1G field with scaling factor for centrifuge model tests, η. Then the parameters are further converted to prototype with scaling factor for 1G tests, μ (Iai, 1989). By using this scaling law, model tests with scaling factor (prototype/physical model) of 100 or much higher may be possible without encountering problems, e.g., scaling of granular material. The generalized scaling law in centrifuge modeling is investigated through dynamic response of compacted sand. In the experiments, a prototype is scaled down to 1/100 with 9 combinations of scaling factors of virtual 1 G and centrifugal field. Input motions are also scaled accordingly. Then the generalized scaling relation is applied to examine responses in the prototype scale. Responses compared in the present study are shear wave velocity, displacement, and acceleration. If the generalized scaling law is valid, these responses in the prototype scale are identical regardless of scaling factors. Results confirm the validity of the scaling relation of these physical parameters in a range of 40 G to 70 G of centrifugal accelerations. © 2009 IOS Press.

DOI： 10.3233/978-1-60750-031-5-664

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Applicability of the two stage scaling relationship called generalized scaling law for centrifuge tests proposed by Iai et al. (2005) is investigated for dynamic response of flat layered media. In this scaling law, recorded physical model parameters are, firstly, converted to those in the virtual 1G field with scaling factor for centrifuge model tests, η. Then the parameters are further converted to prototype with scaling factor for 1G tests, μ (Iai, 1989). By using this scaling law, model tests with scaling factor (prototype/physical model) of 100 or much higher may be possible without encountering problems, e.g., scaling of granular material. The generalized scaling law in centrifuge modeling is investigated through dynamic response of compacted sand. In the experiments, a prototype is scaled down to 1/100 with 9 combinations of scaling factors of virtual 1 G and centrifugal field. Input motions are also scaled accordingly. Then the generalized scaling relation is applied to examine responses in the prototype scale. Responses compared in the present study are shear wave velocity, displacement, and acceleration. If the generalized scaling law is valid, these responses in the prototype scale are identical regardless of scaling factors. Results confirm the validity of the scaling relation of these physical parameters in a range of 40 G to 70 G of centrifugal accelerations. © 2009 IOS Press.

DOI： 10.3233/978-1-60750-031-5-664

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The paper describes an emerging methodology for evaluating seismic performance of geotechnical structures that extend over tens of kilometers along a coastal protection line. The challenging aspect in establishing this type of methodology for performance evaluation is in the fact that site-by-site detailed study is not practical. The paper proposed a performance-based approach utilizing simplified design charts that are newly developed based on a parameter study of effective stress analyses of soil-structure systems. The coastal protection lines over a distance of 70km along Osaka Bay Area, Japan, are used as an example to demonstrate the advantages of the proposed approach.

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A new formulation of elastic body is proposed in order to consider the geometric nonlinearity due to large deformation and rotation. The formulation is based on the concept of the multiple shear mechanism and the relationship between the volumetric strain and the isotropic pressure is assumed to be linear and so is the relationship between the virtual simple shear strain and the virtual simple the shear stress. The constitutive model is introduced to a finite element program by the Total/Updated Lagrangian Formulation. Some examples simulated by the program are given to demonstrate the capability of the model.

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Other Link： http://hdl.handle.net/2433/129308

Language：English   Publisher：AMER INST PHYSICS  

A simplified method to estimate the maximum uplift displacement of a manhole and settlements of backfill soil under liquefaction is proposed. The method is derived based on the mechanism of uplifting of a manhole under undrained condition of backfill soil. It also has a capability of estimating effectiveness of countermeasures against uplifting by considering excess pore water pressure ratio and/or unit weight of backfill soil. In the present study, however, estimation for the case of no countermeasure is verified through comparison with experimental results. Results show that measured uplift displacements and settlements are confined within the boundary predicted by the proposed method.

DOI： 10.1063/1.2963871

Web of Science

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Language：English   Publisher：AMER INST PHYSICS  

A simplified method to estimate the maximum uplift displacement of a manhole and settlements of backfill soil under liquefaction is proposed. The method is derived based on the mechanism of uplifting of a manhole under undrained condition of backfill soil. It also has a capability of estimating effectiveness of countermeasures against uplifting by considering excess pore water pressure ratio and/or unit weight of backfill soil. In the present study, however, estimation for the case of no countermeasure is verified through comparison with experimental results. Results show that measured uplift displacements and settlements are confined within the boundary predicted by the proposed method.

DOI： 10.1063/1.2963871

Web of Science

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Language：Japanese  

Finite strain (large deformation) formulation is presented for a multiple mechanism model for idealizing the behavior of sand. The model is capable of representing non-linear behavior of sand under transient and cyclic loading, including the phenomenon of liquefaction. In the finite strain formulation, isotropic and isochoric components will be separated based on the approach adopted for hyper-elastic materials.

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Language：English   Publisher：EARTHQUAKE ENGINEERING RESEARCH INST  

Seismic intensity in the epicentral area of the 2003 Bam, Iran earthquake is estimated using a questionnaire survey conducted two months after the earthquake. The estimated average seismic intensity on the Japan Meteorological Agency (JMA) scale is 6.1 (VIII to IX in the MMI scale). The peak frequency of the horizontal-to-vertical spectral ratio derived from microtremor measurements conducted during reconnaissance is also compared with the seismic intensity. Collapse rates for various structure types, such as adobe, unreinforced/reinforced masonry, steel-frame, and reinforced concrete, are obtained by counting the number of demolished buildings within an area of about 50-m radius around an observation point. Results show large differences in collapse rates between unreinforced and reinforced masonry, and suggest the upper limit of seismic intensity that unreinforced masonry can sustain. This fact can be utilized for an initial damage assessment within affected areas after large earthquakes.

DOI： 10.1193/1.2790490

Web of Science

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Physical model tests under centrifugal acceleration are conducted and results are compared with the one obtained by a finite element analysis. When the lateral movement of the sheet pile head is fixed during the self-weight analysis in simulation, that is the same condition as the model tests, computed bending moments due to consolidation agree with measured ones and also deflections after shaking are generally consistent with each other. While if the pile head is free in the self-weight analysis, computed bending moments and deformations disagree with measured ones. Thus, to simulate an existing sheet pile wall behavior during large earthquakes with accuracy required in practice, it is necessary to obtain in-situ bending moment profiles and input them as an initial condition.

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Other Link： http://hdl.handle.net/2433/73397

Language：English  

To investigate the generalized scaling relation in centrifuge modeling, a prototype is scaled down to 1/100 with 9 combinations of scaling factors of virtual 1 G and centrifugal field. The model ground is flat and made of a homogeneous sand layer. Five accelerometers are employed in various depths. Dynamic input motions are scaled accordingly. In prototype scale, the applicability of the scaling relation is evaluated by examining the identity of dynamic responses obtained from 9 cases. Results show that shear wave velocities are approximately the same value and, therefore, the generalized scaling relation of shear wave velocity is confirmed. For the scaling relation of acceleration, when the ground response is nearly elastic, the scaling law is confirmed for a range of centrifugal acceleration applied in this study.

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J-GLOBAL

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J-GLOBAL

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Scopus

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J-GLOBAL

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Publisher：Disaster Prevention Research Institute Kyoto University  

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Language：English   Publisher：Disaster Prevention Research Institute Kyoto University  

Dynamic behavior of an embankment (3 m height) made of dry sand underlain by saturated sand deposit with 5 m depth are studied. Firstly, centrifuge experiments under 50 G are conducted. The relative density of saturated sand deposit is approximately either 30 % or 70 %. Sinusoidal input motions with various levels of peak acceleration amplitude are employed. Test results show that the maximum settlement was 1.4 m and 0.09 m, respectively, for loose and dense deposit. The amount of settlements for dense deposit are found to be proportional to the peak amplitude of input acceleration, while it may have a plateau for the case of loose deposit with increase of input acceleration amplitude. Following the centrifuge experiments, an effective stress analysis is carried out with the same prototype dimension of the experiments. The numerical analysis simulates well deformations and transient motions of the experimental counterparts. It is found that, in the analysis for loose deposit, when input acceleration increased, non-liquefied area underneath the embankment became large, causing larger non-liquefied wedge pushing liquefied soils aside.

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Other Link： http://hdl.handle.net/2433/26628

J-GLOBAL

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J-GLOBAL

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Language：Japanese   Publisher：自然災害科学会  

CiNii Books

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Other Link： http://id.nii.ac.jp/1141/00113410/

Language：Japanese   Publisher：自然災害科学会  

CiNii Books

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Other Link： http://id.nii.ac.jp/1141/00113530/

Language：Japanese   Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS39.0.1789.0

J-GLOBAL

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Language：Japanese   Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS39.0.1529.0

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Language：Japanese   Publisher：The Japanese Geotechnical Society  

DOI： 10.11512/jiban.JGS38.0.1443.0

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Language：Japanese   Publisher：Japan Society of Civil Engineers  

Shaking table tests and the three dimensional distinct element analyses were carried out to investigate the rotation response of tomb stones, which are excited by seismic motion. It is clarified that rotation response of a rigid body is caused by two reasons, one is the rocking caused by one directional input motion and the other is caused by the rotation of particle motion of input motion. The rotation response of a real tomb stone was simulated using the accerelation record observed during 1994 Sanriku-Haruka-Oki Earthquake. It is concluded that, except for special cases, the direction of rotation of a rigid body represents the reverse rotation direction of particle motion of seismic motion.

DOI： 10.2208/jscej.1998.598_287

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