研究者詳細 - 西村　伸一

論文 - 西村　伸一

分割表示 163 件中 61 - 80 件目／全件表示 >>

Prediction of multidimensional deformation behavior based on observed value 査読

Nishimura, S, Shuku, T, Fujisawa, K

Int. J. of Geomech. 14 ( 3 ) 04014011_1 - 04014011_10 2014年

Observational Design Method for Earth Structures using Particle Filter 査読

Takayuki Shuku, Shin-Ichi Nishimura, Toshifumi Shibata

Vulnerability, Uncertainty, and Risk: Quantification, Mitigation, and Management - Proceedings of the 2nd International Conference on Vulnerability and Risk Analysis and Management, ICVRAM 2014 and the 6th International Symposium on Uncertainty Modeling and Analysis, ISUMA 2014 2449 - 2458 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：American Society of Civil Engineers (ASCE)

This study presents a reliability-based design method for geotechnical structures based on the observational method, which can be used as a methodology for the performance verification of geotechnical structures. In the proposed method, the soil-water coupled finite element analysis is utilized as a performance-verification method, and stochastic uncertainties inherent in the geotechnical parameters are evaluated by a Monte Carlo simulation. The proposed method can select the optimum design/construction method from several design alternatives, from the viewpoint of Life Cycle Cost, and the predictions at the initial design stage are sequentially updated by the particle filter. The proposed method is applied to a numerical example of the construction problem of embankment specified quantitative performance criteria, such as allowable settlements and the probability of their exceedance, and the feasibility of the method is examined in this example.

DOI： 10.1061/9780784413609.246

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Numerical simulation of dyke breach process using MPS method

Takayuki Shuku, Shizuka Hirayama, Shin-Ichi Nishimura, Toshifumi Shibata

Proceedings of the International Offshore and Polar Engineering Conference 693 - 696 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：International Society of Offshore and Polar Engineers

This study describes a numerical simulation method for dyke breach process due to overflow based on Moving Particle Semi-implicit (MPS) method. The MPS method was developed for incompressible flow with free surface. In the MPS, fluids and geomaterials to be analyzed are represented by particles, and the governing equations describing the mechanical behavior are discretized by particle interaction models. Since MPS method does not need grids, it can be applied to large deformation behavior such as dyke breach process. The MPS method was extended by adding a simple erosion model for simulating breach process of dyke due to overflow. The simulation results for breach process of the dyke by the MPS method were compared with the corresponding observation data to verify the applicability of the MPS method presented in this study. Copyright © 2014 by the International Society of Offshore and Polar Engineers (ISOPE).

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An eco-friendly design method for infrastructures based on CVM

Yasuhisa Shimokado, Takayuki Shuku, Shin-Ichi Nishimura, Toshifumi Shibata

Proceedings of the International Offshore and Polar Engineering Conference 754 - 759 2014年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：International Society of Offshore and Polar Engineers

This study presents an eco-friendly design method for infrastructures based on contingent valuation method (CVM). First, a questionnaire survey based on the CVM was conducted to estimate monetary values of stream habitat which can be damaged by river improvement works such as flood prevention works. Second, a design method which can quantitatively evaluate impacts on stream habitat due to flood prevention works was newly proposed by combining non-uniform flow analysis with a method of stream habitat estimation. Finally, monetary value of environmental loss due to flood prevention works was estimated by using results of CVM and the proposed method in a numerical example, and the effectiveness of the eco-friendly design method was discussed. Copyright © 2014 by the International Society of Offshore and Polar Engineers (ISOPE).

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Data assimilation using the particle filter for identifying the elasto-plastic material properties of geomaterials 査読

Akira Murakami, Takayuki Shuku, Shin-Ichi Nishimura, Kazunori Fujisawa, Kazuyuki Nakamura

International Journal for Numerical and Analytical Methods in Geomechanics 37 ( 11 ) 1642 - 1669 2013年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Wiley

A computational method, incorporating the finite element model (FEM) into data assimilation using the particle filter, is presented for identifying elasto-plastic material properties based on sequential measurements under the known changing traction boundary conditions to overcome some difficulties in identifying the parameters for elasto-plastic problems from which the existing inverse analysis strategies have suffered. A soil-water coupled problem, which uses the elasto-plastic constitutive model, is dealt with as the geotechnical application. Measured data on the settlement and the pore pressure are obtained from a synthetic FEM computation as the forward problem under the known parameters to be identified for both the element tests and the ground behavior during the embankment construction sequence. Parameter identification for elasto-plastic problems, such as soil behavior, should be made by considering the measurements of deformation and/or pore pressure step by step from the initial stage of construction and throughout the deformation history under the changing traction boundary conditions because of the embankment or the excavation because the ground behavior is highly dependent on the loading history. Thus, it appears that sequential data assimilation techniques, such as the particle filter, are the preferable tools that can provide estimates of the state variables, that is, deformation, pore pressure, and unknown parameters, for the constitutive model in geotechnical practice. The present paper discusses the priority of the particle filter in its application to initial/boundary value problems for elasto-plastic materials and demonstrates a couple of numerical examples. © 2012 John Wiley &amp
Sons, Ltd.

DOI： 10.1002/nag.2125

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Relation between seepage force and velocity of sand particles during sand boiling 査読

K. Fujisawa, A. Murakami, S. Nishimura, T. Shuku

Geotechnical Engineering Journal of the SEAGS & AGSSEA 43 ( 2 ) 8 - 16 2013年

模型実験結果に基づく長期沈下予測法の検証査読

西村伸一, 珠玖隆行, 山田典弘, 柴田俊文

土木学会応用力学論文集 16 I_29 - I_38 2013年

MPS法によるニューマチックケーソン施工時の地盤変形解析査読

珠玖隆行, 西村伸一, 川﨑元, 尾形恒夫, 柴田俊文

地盤と建設 31 ( 1 ) 37 - 46 2013年

A new sampling algorithm in particle filter for geotechnical analysis 査読

T. Shuku, S. Nishimura, K. Fujisawa, A. Murakami

Geotechnical Engineering 44 ( 3 ) 32 - 39 2013年

Diagnosis of earth-fills and reliability-based design

S. Nishimura, M. Suzuki, T. Shuku

Safety, Reliability, Risk and Life-Cycle Performance of Structures and Infrastructures - Proceedings of the 11th International Conference on Structural Safety and Reliability, ICOSSAR 2013 5403 - 5409 2013年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）

This research deals with the maintenance strategy of geotechnical structures such as earth-fill dams and river embankments. To determine the soil parameters, the standard penetration test (SPT) N-values are frequently used. Firstly, a statistical model for the N-values is determined from sounding test results. In this research, Swedish Weight Sounding (SWS) tests, simpler than SPT, are employed. Secondly, an indicator simulation is conducted to interpolate the spatial distribution of the N-values, and the results are utilized to find degraded areas inside the embankments and to maintain the embankments. Based on the statistical model for the N-values, the shear strength parameter is derived through the empirical relationships, and then a reliability analysis of the embankments is conducted considering the variability of the internal friction angle. Finally, the effect of improving the embankments is discussed, comparing the calculated risks of the original state with the improved and restored state. © 2013 Taylor &amp
Francis Group, London.

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Diaqnosis of earth-fills and reliability-based desiqn

S. Nishimura, T. Shuku, M. Suzuki

18th International Conference on Soil Mechanics and Geotechnical Engineering: Challenges and Innovations in Geotechnics, ICSMGE 2013 1 599 - 602 2013年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IOS Press

This research deals with the maintenance strategy of geotechnical structures such as earth-fill dams and river embankments. To determine the soil parameters, the standard penetration test (SPT) iV-values are frequently used. Firstly, a statistical model for the iV-values is determined from sounding test results. In this research, Swedish Weight Sounding (SWS) tests, simpler than SPT, are employed. Secondly, an indicator simulation is conducted to interpolate the spatial distribution of the N-values, and the results are utilized to find degraded areas inside the embankments and to maintain the embankments. Based on the statistical model for the iV-values, the shear strength parameter is derived through the empirical relationships, and then a reliability analysis of the embankments is conducted considering the variability of the internal friction angle. Finally, the effect of improving the embankments is discussed, comparing the calculated risks of the original state with the improved and restored state.

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Relation between seepage force and velocity of sand particles during sand boiling

K. Fujisawa, A. Murakami, S. Nishimura, T. Shuku

Geotechnical Engineering 44 ( 2 ) 9 - 17 2012年6月

記述言語：英語掲載種別：研究論文（学術雑誌）

Thus far, the focus of studies on seepage failure, known as sand boiling or the piping phenomenon, has been to determine the critical hydraulic gradient or the critical seepage flow velocity. However, the transport of soil after seepage failure also needs to be well investigated in order to estimate the damage to soil structures or the ground. The purpose of this study is to experimentally investigate the relationship between the seepage force and the velocity of the sand particles during sand boiling induced by upward and horizontal seepage flows. In the experiments, silica sand is used as the test material and the migration velocities of the seepage water and the sand particles are calculated from the measured amounts of their discharge. The test results reveal that the equilibrium of the forces exerted on the sand particles, i.e., gravity, buoyancy and fluid-particle interaction, can be successfully used to estimate the velocity of the sand particles subjected to upward seepage flow and that the seepage force needed for the horizontal transport of the sand tends to decrease as the velocity of the sand particles increases.

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Parameter identification for Cam-clay model in partial loading model tests using the particle filter 査読

Takayuki Shuku, Akira Murakami, Shin-ichi Nishimura, Kazunori Fujisawa, Kazuyuki Nakamura

SOILS AND FOUNDATIONS 52 ( 2 ) 279 - 298 2012年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：JAPANESE GEOTECHNICAL SOC

Data assimilation is a versatile methodology, developed in the earth sciences, such as geophysics, meteorology, and oceanography, for estimating the state of a dynamic system of interest by merging sparse observation data into a numerical model for the system. In particular, the data assimilation method referred to as the particle filter (PF) can be applied to nonlinear and non-Gaussian problems, and it holds the greatest potential for application to geotechnical problems. The objective of this study is to demonstrate the theoretical and the practical effectiveness of the PF for a geotechnical problem, i.e., applying the methodology to numerical experiments and actual model tests to identify the parameters of elasto-plastic geomaterials. Since the mechanical behavior of soils depends on both the current stress and the recent stress history of the soil, the sampling method called SIS, which can take into account the stress history experienced by soils, identifies the parameters of elasto-plastic geomaterials remarkably well. The results of the numerical tests have shown that the parameters identified by the PF based on the SIS have converged into their true values, and the approach presented in this study has shown great promise as an accurate parameter identification method for elasto-plastic geomaterials. Moreover, the simulation results using the identified parameters were close to the actual measurement data, and long-term predictions with high accuracy could be achieved, even though short-term measurement data were used. The PF approach produces more information about the parameters of interest than simple estimated values obtained from optimization methods. Namely, the identification comes in the form of probability density functions. (c) 2012 The Japanese Geotechnical Society. Production and hosting by Elsevier B.V. All rights reserved.

DOI： 10.1016/j.sandf.2012.02.006

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Numerical simulation of embankment breaching due to overflow based on erosion rate of soils

K. Fujisawa, A. Murakami, S. Nishimura, T. Shuku

New Frontiers in Computational Geotechnics, Takayama 133 - 138 2012年

ため池の維持管理と改修効果の評価

西村伸一, 藤澤和謙, 森井顕二, 長尾遥奈

地盤工学会誌 60 ( 1 ) 28 - 31 2012年

土の侵食速度を用いた堤体の越流破堤解析査読

藤澤和謙, 村上章, 西村伸一, 珠玖隆行

土木学会応用力学論文集 15 I_317 - I_326 2012年

粒子フィルタを用いた軟弱地盤の残留沈下予測査読

西村伸一, 珠玖隆行, 西村友希, 藤澤和謙, 村上章

土木学会応用力学論文集 15 I_103 - I_114 2012年

データ同化による地盤構造物内の劣化箇所同定に関する基礎的研究査読

珠玖隆行, 西村伸一, 藤澤和謙

土木学会応用力学論文集 50 I_89 - I_101 2012年

上向き浸透流による浸透破壊時の砂粒子の移動速度査読

藤澤和謙, 西村伸一, 中谷亜由美, 村上章

農業農村工学会論文集 281 ( 5 ) 35 - 41 2012年

記述言語：日本語出版者・発行元：The Japanese Society of Irrigation, Drainage and Rural Engineering

水の浸透作用によって砂の骨格が破壊し，噴砂が生じる浸透破壊に関するこれまでの研究では，主に浸透破壊の生じる動水勾配や浸透流速を把握することに焦点が置かれてきた．しかし，浸透破壊後の地盤や土構造物の状況を予測するには，浸透破壊時の土粒子の輸送現象を把握する必要がある．本研究では，鉛直上向きの浸透による浸透破壊の際に，浸透流によって運ばれる砂の挙動を実験的に調査した．実験においては，浸透破壊時の浸透水と砂粒子の流出量を分離して測定し，動水勾配と共に浸透流速と砂粒子の移動速度を計測した．その結果からは，透水係数を用いた砂と浸透水との相互作用モデルを用いれば，材料の違いによらず，鉛直方向の力のつり合いによって良好に砂の移動速度を推定できることが明らかとなった．

DOI： 10.11408/jsidre.80.409

CiNii Article

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その他リンク： https://jlc.jst.go.jp/DN/JALC/10024829952?from=CiNii

Determination of partial factors for the verification of the bearing capacity of shallow foundations under open channels 査読

Akira Murakami, Shin-Ichi Nishimura, Makoto Suzuki, Mitsuhiro Mori, Takashi Kurata, Tatsuya Fujimura

Georisk 5 ( 3-4 ) 186 - 194 2011年9月

記述言語：英語掲載種別：研究論文（学術雑誌）

The limit state design method has been introduced into the design criteria for geotechnical structures.The current paper attempts to apply the reliability-based design method, at Level II, to the bearing capacity of the foundations of open channels from the viewpoint of the limit state design.To examine the applicability of the proposed procedure for practical structures, the reliability index is computed for evaluating the stability of the foundations of existing open channels designed by the conventional method.The conventional design procedure makes excessively safe side design.We applied the first order reliability methods (FORM) to the existing open channels designed by the conventional design procedure, and consequently, large values of reliability index, 3 and 5 were obtained for clayey and sandy soils, respectively.Finally, the partial factors for the soil parameters have been determined, corresponding to the target reliability indices β&lt
inf&gt
t&lt
/inf&gt
=1, 3 and 4. © 2011 Taylor &amp
Francis.

DOI： 10.1080/17499518.2011.558417

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