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Journal Articles

Tunnel excavation analysis of siliceous mudstone using a damage model

Mishima, Seiki*; Ogata, Sho*; Inui, Toru*; Yasuhara, Hideaki*; Kishida, Kiyoshi*; Aoyagi, Kazuhei

Dai-15-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), p.215 - 220, 2021/01

When the durability of the geological repository of high-level radioactive waste is evaluated, understanding the cracking behavior within the crystalline/sedimentary rocks during excavation of waste disposal cavities is important. In this study, we performed a numerical analysis that expressed the tunnel excavation carried out 350 m underground at the Horonobe Underground Research Center of the Japan Atomic Energy Agency. Simulated results are agreement with actual trends of fracture propagation, and the measured horizontal convergence of the tunnel was reproduced by the numerical analysis relatively well.

Journal Articles

Coupled THMC analysis for predicting hydro-mechanical evolution in siliceous mudstone

Ogata, Sho*; Yasuhara, Hideaki*; Aoyagi, Kazuhei; Kishida, Kiyoshi*

Proceedings of 53rd US Rock Mechanics/Geomechanics Symposium (USB Flash Drive), 6 Pages, 2019/06

Journal Articles

Segmentation of granite and single fracture through microfocus X-ray CT and its application

Ishikawa, Tomohiro*; Yasuhara, Hideaki*; Sawada, Atsushi; Kishida, Kiyoshi*

Dai-50-Kai Jiban Kogaku Kenkyu Happyokai Rombunshu, p.515 - 516, 2015/06

no abstracts in English

Journal Articles

Measurements of fracture aperture in granite core using microfocus X-ray CT and fluid flow simulation

Kishida, Kiyoshi*; Ishikawa, Tomohiro*; Higo, Yosuke*; Sawada, Atsushi; Yasuhara, Hideaki*

Proceedings of 49th US Rock Mechanics/Geomechanics Symposium (CD-ROM), 6 Pages, 2015/06

In order to estimate the changes in fracture aperture under various long-term confining and thermal conditions, measurements of the fracture aperture are conducted using microfocus X-ray CT. Through the imaging data, the altitude of the fracture surface and the contact points are evaluated, and contact ratios for the fracture, the JRC and the aperture distribution are estimated. On the other hand, measurements are also conducted using a laser scan profile sensor, and some parameters are estimated. In comparing these parameters, the validity of the X-ray CT data and an analysis of the data will be discussed. In addition, a fracture flow simulation will be conducted using the altitude and aperture data obtained by the microfocus X-ray CT.

Journal Articles

Estimation of fracture flow in considering the inhomogeneous structure of single rock fractures

Kishida, Kiyoshi*; Sawada, Atsushi; Yasuhara, Hideaki*; Hosoda, Takashi*

Soils and Foundations, 53(1), p.105 - 116, 2013/02

 Times Cited Count:17 Percentile:65.57(Engineering, Geological)

Considering the safe, long-term sequestration of energy byproducts, such as radioactive waste, one of the important parameters is the groundwater flow velocity through the void of rock masses and/or fractures. In this research work, two-dimensional seepage flow analyses, using the authors' proposed 2D model, with considering the inertia term, are carried out for single fracture permeability tests under conditions which allow for the application of the cubic law. In comparing the results of the experiments with the numerical simulations, the results of the simulation show a good agreement with the experimental results. From these simulation results, the fracture flow of an inhomogeneous structure is discussed, along with the local Reynolds number, and the resistance through the fracture geometry is considered. Consequently, under the condition of a mean Reynolds number of less than 1.0, the inertia terms cannot affect on the fracture flow, but the hydraulic resistance can affect.

Journal Articles

Dependence of fracture geometry and spatial variation in pressure on hydraulic conductivity in rock fractures

Kishida, Kiyoshi*; Hosoda, Takashi*; Sawada, Atsushi; Sato, Hisashi; Nakashima, Shinichiro*; Yasuhara, Hideaki*

Harmonising Rock Engineering and the Environment, p.1327 - 1330, 2011/10

Although it is generally known that a natural rock fracture indicates a complex aperture distribution, the fracture is an ideal representation of the parallel plate model. The cubic law is applied to evaluate the hydraulic properties of fractured rock. From several previous research works, it is known that the cubic law can be applied when the Reynolds number is less than 1.0 and that the advection term can basically be ignored in such fracture flows. In this research work, two-dimensional seepage flow analyses, using the authors' proposed 2D model which is considered with the advection term, are carried out for single fracture hydro-conductivity experiments under conditions which allow for the application of the cubic law. From the numerical results, the validity of the 2D model is discussed along with the local Reynolds number and the application of the cubic law.

JAEA Reports

Geometrical properties of tension-induced fractures in granite

Sato, Hisashi; Yasuhara, Hideaki*; Sawada, Atsushi

JAEA-Research 2010-069, 45 Pages, 2011/03


Considering a safe, long-term sequestration of energy byproducts such as high level radioactive wastes, it is of significant importance to well-constrain the hydraulic and transport behavior of targeted permeants within fractured rocks. Specifically, fluid flow within low-permeability crystalline rock masses (e.g., granite) is often dominated by transport in through-cutting fractures, and thus careful considerations are needed on the behavior. There are three planes along that granites fail most easily under tension, and those may be identified as the rift, grain, and hardway planes. In this research, geometrical properties of tension-induced fractures were evaluated. Results show that rift planes are less rougher than the other planes of grain and hardway, and grain planes are generically rougher than the other planes of rift and hardway.

Journal Articles

Evolution of permeability in diatomaceous rocks mediated by pressure solution

Yasuhara, Hideaki*; Kurikami, Hiroshi; Kinoshita, Naoki*; Kishida, Kiyoshi*

Dai-36-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu, p.283 - 286, 2007/01

no abstracts in English

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