研究者詳細 - 西山　哲

論文 - 西山　哲

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MEMS型三軸傾斜計による法面崩壊の計測事例査読

中村公一, 島内哲哉, 小野和行, 西山哲

地盤と建設 32 ( 1 ) 131 - 136 2014年12月

Application of MEMS to monitoring system for natural disaster reduction

Nao Minakata, Takao Yano, Satoshi Nishiyama, Meiji Ryu

Proceedings of IEEE Sensors 2014- ( December ) 1443 - 1446 2014年12月

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：Institute of Electrical and Electronics Engineers Inc.

Recently it has become important to develop a new monitoring system for structures. This is because the ageing infrastructure and an increase in abnormal weathers caused by the climate change have resulted in hazard assessments becoming more difficult. Therefore, there is a need to be able to monitor vulnerable structures more carefully and to assess their safety in real time. For this purpose, we require a new monitoring system that can monitor a structure more closely, easily, and efficiently than the existing methods. We developed a new monitoringsystem using a Micro Electro Mechanical System and wireless communication. We applied this system to a retaining wall with a deep-seated slope failure, in order to assess the serviceability of this method in general, and the safety of this retaining wall in particular.

DOI： 10.1109/ICSENS.2014.6985285

Mechanical and hydraulic behavior of a rock fracture under shear deformation 査読

Satoshi Nishiyama, Yuzo Ohnishi, Hisao Ito, Takao Yano

EARTH PLANETS AND SPACE 66 2014年9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：SPRINGER HEIDELBERG

With regard to crystalline rock that constitutes deep geology, attempts have been made to explore its hydraulic characteristics by focusing on the network of numerous fractures within. As the hydraulic characteristics of a rock are the accumulation of hydraulic characteristics of each fracture, it is necessary to develop the hydraulic model of a single fracture to predict the large-scale hydraulic behavior. To this end, a simultaneous permeability and shear test device is developed, and shear-flow coupling tests are conducted on specimens having fractures with varied levels of surface roughness in the constant normal stiffness conditions. The results show that the permeability characteristics in the relation between shear displacement and transmissivity change greatly at the point where the stress path reaches the Mohr-Coulomb failure curve. It is also found that there exists a range in which transmissivity is not proportional to the cube of mechanical aperture width, which seems to be because of the occurrence of channeling phenomenon at small mechanical aperture widths. This channeling flow disappears with increasing shear and is transformed into a uniform flow. We develop a simulation technique to evaluate the macroscopic permeability characteristics by the lattice gas cellular automaton method, considering the microstructure of fracture, namely the fracture surface roughness. With this technique, it is shown that the formation of the Hagen-Poiseuille flow is affected by the fracture microstructure under shear, which as a result determines the relationship between the mechanical aperture width and transmissivity.

DOI： 10.1186/1880-5981-66-108

交通事故低減機能が期待された環境改善舗装の長期機能保持に関する考察査読

西山哲, 和田實, 辻森和美, 有賀公則

交通科学 44 ( 2 ) 4 - 10 2014年3月

斜面モニタリングにおける三次元写真計測法の適用査読

菊地輝行, 秦野輝儀, 西山哲

応用地質 54 ( 6 ) 264 - 271 2014年2月

記述言語：日本語出版者・発行元：一般社団法人日本応用地質学会

本研究は，写真撮影という簡便な計測手法によって三次元的に対象物を復元するデジタル写真測量を応用し，斜面変動による変位分布を高精度で検知する手法を構築した．具体的には，まずターゲットの2点間距離の計測によって変位が発生した箇所を絞り込み，次に変位が発生したと判断した箇所の三次元の変位分布を求める解析手順の理論的構築を試み，広い範囲を対象とした場合でも基準点を設置することなくデジタル写真測量の利点を活かした簡便な手法を用いて高精度な計測が実施できる手法を確立した．実測例として，幅120m，高さ30mの山留擁壁において5mm以上の変位を生じている箇所を抽出し，その変位の挙動を三次元的に捉えることが可能であることを示した．さらに同じ擁壁に設置したクラック変位計および光波・水準測量の変位計測結果と比較することで，本計測手法による計測結果の妥当性を検証した．

DOI： 10.5110/jjseg.54.264

モービルマッピングシステムによる河川堤防の高精度計測査読

東良慶, 西山哲, 石川貴一朗, 吉岡裕嗣, 島村秀樹, 大浪裕之

河川技術論文集 20 485‐490 2014年

間隙流体の挙動と縦波弾性波の分散特性の関係に関する研究査読

西山哲, 佐野修, 伊藤久男, 高橋学

地学雑誌 122 ( 1 ) 170 - 191 2013年2月

Study on application of MEMS sensor network to monitoring method of retaining wall behavior

Nao Minakata, Satoshi Nishiyama, Takao Yano, Hitoshi Tezuka, Koichi Aoki

International Multidisciplinary Scientific GeoConference Surveying Geology and Mining Ecology Management, SGEM 2 443 - 449 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 paper presents some results of studies on application of a monitoring system using Micro Electro Mechanical System (MEMS) sensors in order to measure deformations of a retaining wall. The MEMS sensors have three advantages which are compact, lightweight, and inexpensive. In this paper, the authors propose that using the supports system, the precision of the sensor network system gets higher than before. Using wireless communication between the transmitter and receiver in this system, the data observed by the MEMS sensor is transmitted to the base station directly, and the distance is approximately 500m with good visibility and about 300m with vegetation. The authors applied this system to monitoring an actual retaining wall under construction. It is concluded from the result that the MEMS sensor could measure very small deformations of the retaining wall and the small change of an inclination had been affected by a series of external factors such as rainfalls and an earth pressure from the back of the wall. © SGEM2013 All Rights Reserved by the International Multidisciplinary Scientific GeoConference SGEM.

DOI： 10.5593/SGEM2013/BA1.V2/S02.058

Retraction Note to: Real-time slope water table forecasting by multi-tank model combined with dual ensemble Kalman filter (Landslides, (2011) 8, (81-89), 10.1007/s10346-010-0223-y)

Jun Xiong, Tomofumi Koyama, Satoshi Nisiyama, Yuzo Ohnishi, Kenji Takahashi

Landslides 9 ( 2 ) 303 2012年6月

A Numerical Study on the Effect of Shear Resistance on the Landslide by Discontinuous Deformation Analysis (DDA)

Kei Irie, Tomofumi Koyama, Satoshi Nishiyama, Yuki Yasuda, Yuzo Ohnishi

Geomechanics and Geoengineering 7 ( 1 ) 57 - 68 2012年3月

記述言語：英語掲載種別：研究論文（学術雑誌）

Japan is located in Circum-Pacific earthquake zone, which is one of the most seismologically active areas in the world. As a result, landslides have occurred frequently and often cause serious damage not only to human lives but also to the various important structures such as national roads, railway, electric power plans etc. From the engineering point of view, to investigate the mechanism of landslide due to earthquakes and estimate the damage caused by landslides are important issues. In this study, as the first step, to check the validity of DDA simulation for the seismic problems, a series of shaking table tests were carried out in the laboratory and simulated by DDA. Then, one of the largest landslides occurred in Aratozawa Area, Miyagi, Japan in 2008 caused by Iwate-Miyagi Nairiku Earthquake was simulated using DDA and discussed the mechanisms of the landslide. The 2-D DDA model for one of the survey lines was created based on the geological survey, and physical properties were determined from the laboratory tests using rock/soil samples obtained from the landslide site. In this study, to discuss the mechanism of the landslide, a series of parametric study in terms of shear resistance along the fractures was conducted. © 2012 Copyright Taylor and Francis Group, LLC.

DOI： 10.1080/17486025.2011.578672

飽和－不飽和浸透解析を用いた透水性舗装の洪水抑制機能に関する研究査読

矢野隆夫, 西山哲, 大西有三, 中島伸一郎, 森石一志, 和田實

土木学会論文集E1（舗装工学） 68 ( 1 ) 32 - 44 2012年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人土木学会

透水性舗装は都市環境改善および都市水害防止の対策工法として注目されている．しかし，透水性舗装における雨水の浸透は，非定常かつ不飽和状態であり，なおかつ，路盤などの湿潤状態により異なることから，雨水浸透・流出抑制効果を正確に評価することは難しい．そこで，本研究は透水性舗装のそれらの効果を解明するため，実物大舗装モデルによる散水実験を実施し，降雨強度，溢流量などの計測結果に基づき，著者らが明らかにしたポーラスアスファルト混合物および路盤材，路床材の不飽和浸透特性を用いて飽和－不飽和浸透解析を行った．その結果，透水性舗装の雨水浸透・流出抑制効果は飽和－不飽和浸透解析で評価できることを示した．

DOI： 10.2208/jscejpe.68.32

多孔質媒体中の間隙流体の粘性と縦波弾性波の分散特性に関する研究

西山哲, 矢野隆夫, 大西有三

材料 61 ( 3 ) 222 - 227 2012年

記述言語：日本語掲載種別：研究論文（学術雑誌）出版者・発行元：公益社団法人日本材料学会

Survey methods using elastic wave velocity have been performed in order to estimate the pore fluid properties in rock mass, but the viscosity and density of pore fluid have not been estimated quantitatively by the values of velocity or the velocity changes. We describe in this paper whether pore fluid properties can be estimated by using the dispersion of longitudinal elastic waves. We measured the frequency-dependent velocity data of longitudinal elastic waves in porous specimens and the dependence of the velocity dispersion on the kinematic viscosity of pore fluid. Moreover, we try to explain the velocity dispersion shown by the measurement data using the Biot theory. The Biot theory explains that the dispersion phenomenon is caused by the elastic property change in the media with the interaction between the solid phase and liquid phase, so the dispersion is dependent on the properties of liquid phase. The measurement data showed the phase velocities of longitudinal waves increased with an increase of frequencies and the characteristic frequencies which indicate the points of inflection moved to higher frequencies with an increase of kinematic viscosities of pore fluid. We report that we can estimate the kinematic viscosity of pore fluid in rock mass by using the dispersion curves which graphed the relation between the phase velocities and frequencies.

DOI： 10.2472/jsms.61.222

多孔質媒体中の間隙流体の粘性と縦波弾性波の分散特性に関する研究査読

西山哲, 矢野隆夫, 大西有三

材料 61 ( 3 ) 222 - 227 2012年

記述言語：日本語出版者・発行元：公益社団法人日本材料学会

Survey methods using elastic wave velocity have been performed in order to estimate the pore fluid properties in rock mass, but the viscosity and density of pore fluid have not been estimated quantitatively by the values of velocity or the velocity changes. We describe in this paper whether pore fluid properties can be estimated by using the dispersion of longitudinal elastic waves. We measured the frequency-dependent velocity data of longitudinal elastic waves in porous specimens and the dependence of the velocity dispersion on the kinematic viscosity of pore fluid. Moreover, we try to explain the velocity dispersion shown by the measurement data using the Biot theory. The Biot theory explains that the dispersion phenomenon is caused by the elastic property change in the media with the interaction between the solid phase and liquid phase, so the dispersion is dependent on the properties of liquid phase. The measurement data showed the phase velocities of longitudinal waves increased with an increase of frequencies and the characteristic frequencies which indicate the points of inflection moved to higher frequencies with an increase of kinematic viscosities of pore fluid. We report that we can estimate the kinematic viscosity of pore fluid in rock mass by using the dispersion curves which graphed the relation between the phase velocities and frequencies.

DOI： 10.2472/jsms.61.222

DDA simulations for slope failure/collapse experiment caused by torrential rainfall 査読

T. Koyama, K. Irie, K. Nagano, S. Nishiyama, N. Sakai, Y. Ohnishi

Proceedings of the 10th International Conference on Advances in Discontinuous Numerical Methods and Applications in Geomechanics and Geoengineering, ICADD 10 119 - 126 2012年

掲載種別：研究論文（国際会議プロシーディングス）

In this study, a series of large-scale slope failure experiments with torrential rainfall was carried out and simulated using Discontinuous Deformation Analysis (DDA). Since DDA have not been coupled with flow calculation at present, the rainwater infiltration and rising groundwater level inside the slope was simulated separately using saturated-unsaturated flow analysis by Finite Element Method (FEM). The flow simulation results by FEM were incorporated in the DDA mechanical simulation as reduction of the shear strength and increase of the self weight. In the 2-D DDA model, octagonal blocks of 11.8 cm on average were used and rainfall boundary condition (steady rainfall of 100 mm/hour) was applied to the ground surface. The DDA simulation results were compared with the ones obtained from the rainfall experiments and the applicability of DDA to the slope failure/ collapse caused by torrential rainfall was also discussed. The simulation results also show that groundwater plays important roles for the failure process of soil mass, especially rainwater infiltration mechanism was significantly affected by unsaturated soil properties. © 2012 Taylor & Francis Group, London.

DOI： 10.1201/b11600-15

STABILITY ANALYSES FOR ANCIENT MASONRY STRUCTURES USING DISCONTINUOUS DEFORMATION ANALYSIS AND NUMERICAL MANIFOLD METHOD 査読

Takeshi Sasaki, Ikuo Hagiwara, Kastuji Sasaki, Ryunoshin Yoshinaka, Yuzo Ohnishi, Satishi Nishiyama, Tomofumi Koyama

INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS 8 ( 2 ) 247 - 275 2011年6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：WORLD SCIENTIFIC PUBL CO PTE LTD

In this paper, the stability including stress distribution of two ancient masonry structures, the pyramid of the Pharaoh Khufu, Egypt and the Pont of Gard, were analyzed using discontinuous deformation analysis (DDA) and numerical manifold method (NMM). For the simulation using NMM, the newly developed four-node isoparametric element was used. The stress distributions/concentration were calculated and compared between the two methods. The calculated results show qualitative agreement with observations. DDA and NMM are applicable to simulate the physical phenomena of masonry structures.

DOI： 10.1142/S0219876211002575

Real-time slope water table forecasting by multi-tank model combined with dual ensemble Kalman filter (Retracted article. See vol. 9, pg. 303, 2012) 査読

Jun Xiong, Tomofumi Koyama, Satoshi Nisiyama, Yuzo Ohnishi, Kenji Takahashi

LANDSLIDES 8 ( 1 ) 81 - 89 2011年3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：SPRINGER HEIDELBERG

The multi-tank model is a helpful tool for rainfall-groundwater-runoff analysis since it can represent a nonlinear transport behavior and give predictions very quickly. On one hand, because of its simple and quick calculation, the tank model is useful in water table or stream flow prediction; on the other hand, by reason of its simplicity, its model error is relatively big, the model adjustment through the time variation is necessary. A new data assimilation methodology for online tuning of model parameters and states in the multi-tank model by taking into account new observations was developed, and important model parameters and states are retrieved simultaneously based on dual ensemble Kalman filter. A description of applying multi-tank model to simulate rainfall infiltration process in the slope is presented, and also the implementation of the dual ensemble Kalman filter approach for slope water table forecasting is demonstrated. Based on the observation data, the performance of the new method is studied. Finally, the factor of slope stability could be predicted based on filtered water tables. In this way, an early warning system of slope stability during rainfall could be built, which is helpful for disaster prevention.

DOI： 10.1007/s10346-010-0223-y

Modeling the interaction between fluid flow and particle movement with discontinuous deformation analysis (DDA) method 査読

Tomofumi Koyama, Satoshi Nishiyama, Meng Yang, Yuzo Ohnishi

INTERNATIONAL JOURNAL FOR NUMERICAL AND ANALYTICAL METHODS IN GEOMECHANICS 35 ( 1 ) 1 - 20 2011年1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

Coupled hydro-mechanical processes in granular media represent the interaction between solid particles movement and fluid flow during external and/or internal loading. The processes attract attention in geotechnical engineering since they cause many disasters such as landslide, slope collapse, boiling/quicksand and soil liquefaction, etc. This study presents a numerical method combining discontinuous deformation analysis (DDA) for mechanical calculation and finite element method for fluid flow simulation to model the interaction between solid particles' movement and fluid flow from microscopic point of view. The term of hydraulic pressure was newly formulated and introduced to the original DDA. The simplified examples are given to verify the new method, and the computational results correlate well with the theoretical calculations, further development is also considered. Copyright (C) 2010 John Wiley & Sons, Ltd.

DOI： 10.1002/nag.890

粒状路盤材および路床材の不飽和浸透特性査読

矢野隆夫, 西山哲, 中島伸一郎, 森石一志, 大西有三

土木学会論文集E1（舗装工学） 67 ( 2 ) 120 - 130 2011年

出版者・発行元：公益社団法人土木学会

透水性舗装の貯留・浸透特性を飽和―不飽和浸透解析や気液二相流解析等で評価する場合，舗装を構成する各材料の不飽和浸透特性を精緻に把握しておくことが必要である．そこで透水性舗装の材料としてポーラスアスファルト混合物，路盤材および数種の路床材に対して，水分保持特性試験および飽和―不飽和透水試験を実施し，解析における不飽和パラメータの取得を行った．ポーラスアスファルト混合物に対する試験結果については既に報告しており，本論文では路盤材および路床材の結果について報告する．試験結果を既存のモデル式でフィッティングしたところ，水分保持特性は Van Genuchten 式の適用性が良い事を，路盤材の不飽和透水特性は主に Irmay 型の式で，路床材は Van Genuchten 式でよく表現できることを明らかにした．

DOI： 10.2208/jscejpe.67.120

岩石供試体における弾性波の分散現象に関する研究査読

西山哲, 大西有三, 矢野隆夫, 高橋学, 吉村公孝, 安藤賢一

土木学会論文集C（地圏工学） 67 ( 2 ) 288 - 298 2011年

出版者・発行元：公益社団法人土木学会

弾性波の伝播速度および減衰の周波数依存性を利用して，地盤の透水特性あるいは間隙流体の特性を調査する手法が検討されている．Biot理論によって分散現象は説明できるが，地盤条件によって観測される分散現象がどの程度相違するのか，あるいは地盤の透水特性がどの程度分散現象に反映されるのかが明確にされていないという問題がある．本研究では岩石供試体を用いた室内実験の結果に基づき，堆積岩と花崗岩で観測される縦波の分散現象の違いとBiot理論の適用性を考察し，さらに分散現象から透水特性を推定することの可能性を検討することにより，分散現象を利用して地盤の透水特性を計測する手法の妥当性を，Squirt flowという局所的な間隙流体の挙動を考慮するBISQ理論の適用性と共に示した．

DOI： 10.2208/jscejge.67.288

無線機器を利用した斜面変位計測法の研究査読

西山哲, 大西有三, 矢野隆夫, 里優, 吉崎互

地盤工学ジャーナル 6 ( 4 ) 503 - 511 2011年

記述言語：日本語出版者・発行元：公益社団法人地盤工学会

本論文は，任意の計測点に設置した無線機の電波を受信することで，斜面および法面の変位を計測する手法の研究成果をまとめたものである。具体的には斜面および法面上に設置した特定小電力無線機からの電波を，遠隔に設置した複数の受信機にて受信し，各受信波の等位相差面の交点から当無線機の3次元座標を算出することで変位を計測するものである。本研究では，無線機の座標値を算出する方法を考察するとともに，2.4GHz帯の電波の送受信機を用いた計測実験により，高精度にて変位をリアルタイムに検出できることを実証した。また計測精度に影響を与える要因として，電波の送受信機の幾何学的な配置によって決まるGDOPという指標と計測精度の関係等を明らかにし，実斜面での適用性を検証した。

DOI： 10.3208/jgs.6.503

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