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Nishi-Tokyo-shi, Japan

Iwata N.,Chuden Engineering Consultants Co. | Sasaki T.,Suncoh Consultants Co. | Yoshinaka R.,Saitama University | Kurooka K.,Chugoku Electric Power Co.
International Journal of Rock Mechanics and Mining Sciences | Year: 2012

This paper describes the validity of the multiple yield model (MYM) based on a comparison between predictions by MYM analysis and in-situ measurements of two large-scale vertical excavations, about 30. m in depth and 100. m in width, for nuclear power plants. MYM is a finite element method for modeling the mechanical properties of intact rock and joint systems in rock mass. The method can analyze the non-linearity of deformation under loading and unloading stress paths. The analysis was conducted by determining the geometrical model of rock mass from test adit and borehole observations of discontinuities in conditions such as orientation, spacing, and persistence. The physical parameters of intact rock and discontinuities were determined by laboratory tests using sample specimens, taking the scale effect into account. The deformation mode and displacement value determined by the MYM analysis both corresponded well with in-situ measurements. We have confirmed that MYM can estimate the actual behavior of discontinuous rocks with adequate accuracy for practical application. © 2012 Elsevier Ltd. Source


Takagishi M.,Japan Research Institute of Innovative Technology for the Earth | Hashimoto T.,Japan Research Institute of Innovative Technology for the Earth | Horikawa S.,Suncoh Consultants Co. | Kusunose K.,Japan National Institute of Advanced Industrial Science and Technology | And 2 more authors.
Energy Procedia | Year: 2014

This paper describes passive seismic monitoring at the large-scale CO2 injection site, Cranfield oilfield, Mississippi, U.S.A. We constructed a horizontal near-surface monitoring network and have been monitoring for more than two years to elucidate relationship between large-volume CO2 injection and occurrences of induced seismicities. We have detected no microseismic events that occurred in and around the Cranfield site for now. The detected signals were all identified as cultural noises, natural noises due to weather changes, and distant earthquakes. We also estimated minimum detectable magnitudes of the monitoring network by theoretical calculations and confirmed that the system could enough ability to detect microseismic events. © 2014 The Authors. Published by Elsevier Ltd. Source


Miki S.,Kisojiban Consultants Co. | Sasaki T.,Suncoh Consultants Co. | Koyama T.,Kyoto University | Nishiyama S.,Kyoto University | Ohnishi Y.O.,Kyoto University
International Journal of Computational Methods | Year: 2010

Discontinuous Deformation Analysis (DDA) and Numerical Manifold Method (NMM) have been widely used for the analyses of discontinuous rock masses. Recently, these discontinuum-based numerical methods have been applied to the simulations for slope failure due to earthquakes, where one of the key issues is the estimation of traveling velocities and distances for the collapsed rock blocks. For the dynamic response analysis of rock slopes, it is necessary to consider the local variation of seismic forces, especially when the slope size is large and/or the slope geometry becomes complicated. In DDA, there is difficulty to consider the local displacements and stress condition of the single block for the basement because of mathematical principle (in DDA, the displacement function is defined at the gravity center of the blocks and the strain in the block is uniform). On the other hand, NMM can simulate both continuous and discontinuous deformation of the block systems. However, the rigid body rotation of blocks cannot be treated properly because NMM does not deal with the rigid body rotation in explicit form. According to the above-mentioned features and drawbacks, it is reasonable to combine DDA and NMM from practical point of view. In this paper, the formulation for the coupled NMM and DDA (NMM-DDA) was presented. For the formulation, NMM and DDA can be easily combined by choosing displacements of the DDA blocks and NMM cover nodes as unknowns, because the processes to establish the equilibrium equations (minimizing total potential energy) and kinematics for block system are same between DDA and NMM. In this paper, some applications of the NMM-DDA to both dynamic and static problems were also presented and the validity and applicability of newly developed DDA-MM were discussed. © 2010 World Scientific Publishing Company. Source


Iwata N.,Chuden Engineering Consultants Co. | Yoshinaka R.,Saitama University | Sasaki T.,Suncoh Consultants Co.
International Journal of Rock Mechanics and Mining Sciences | Year: 2013

The stability, deformation behavior, permeability and other properties of discontinuous rocks are greatly influenced by the geometrical distribution of discontinuities in rock mass, and extremely important infrastructures such as nuclear power plants, large-scale underground excavations, long-span bridges, etc. built on or in discontinuous rock mass are also influenced by these same effects. However, a seismic analytical method such as for earthquake response, to correctly evaluate discontinuous conditions of rock mass has not been developed. This paper describes a new seismic response analytical method using the multiple yield model as a kind of FEM. The applicability of this method was verified by making comparisons between the seismographic records obtained with several underground deaths at The 2005 offshore Miyagi Prefecture Earthquake (MW=7.2) and The 2011 offshore the Pacific coast of Tohoku Earthquake (MW=9.0), both of which seismic motions were obtained at the same large and very important nuclear power plant, and the results of the response analyses using the seismic motions recorded at the deepest earth level of seismographs. The geological condition of the foundation ground is one of strongly folded hard sedimentary rocks. From this study, we have confirmed that the multiple yield model is an effective method for seismic response analysis. © 2013 Elsevier Ltd. Source


Iwata N.,Chuden Engineering Consultants Co. | Sasaki T.,Suncoh Consultants Co. | Yoshinaka R.,Saitama University
Harmonising Rock Engineering and the Environment - Proceedings of the 12th ISRM International Congress on Rock Mechanics | Year: 2012

The authors are analyzed two practical examples of large scale vertical excavations 20-30m in depth and two earthquake response analyses of the discontinuous rock slope and rock foundation of large building, and are presented the applicability of MultipleYield Model (MYM). MYM is a kind of finite element method constituted the mechanical properties of intact rock and discontinuity systems in rock mass, and can be analyzed the non-linearity of deformation under loading and unloading stress paths considering the confining pressures of rock joints. For analyzing, the geometrical models of rock mass were determined from site investigations and the physical parameters were determined by laboratory test and also considering scale effect. The results of MYM analysis were well corresponded to the measurement and it is confirmed that MYM is effective for static and dynamic response on jointed rock masses. © 2012 Taylor & Francis Group, London. Source

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