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Kawata, Kento*; Ogata, Sho*; Aoyagi, Kazuhei; Ozaki, Yusuke; Iwai, Hiromasa*; Yasuhara, Hideaki*
Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.113 - 118, 2025/12
In the deep geological disposal of High-Level Waste, it is essential to understand the fracturing behavior of the rock mass surrounding the disposal tunnel due to excavation for assessing the safety of the repository. In this study, 2D tunnel excavation analysis models based on damage theory were developed and were applied to an in-situ tunnel excavation conducted at Horonobe Underground Research Laboratory. The results of the analysis were then compared with in-situ data available on the purpose of validation. As a result, 18 different analysis models were constructed by changing model parameters, and two models that exhibited the best agreement with the measured data were proposed.
Ozaki, Yusuke; Ogata, Sho*; Nakaoka, Kenichi*; Shimizu, Hiroyuki*; Yasuhara, Hideaki*; Akaki, Toshifumi*; Aoyagi, Kazuhei; Fukuda, Daisuke*
Dai-51-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu(Internet), p.125 - 130, 2025/12
The Subcommittee on Research of Coupled Phenomena in Rock, under the Japan Society of Civil Engineers, conducts coupled numerical simulations using various approaches by participating members. The evaluation of the excavation damaged zone (EDZ) in the Horonobe Underground Research Laboratory using hydro-mechanical coupled simulation is one of the tasks of the subcommittee. In this presentation, the problem statement, modeling approaches, and current results from participating organizations are summarized.
Suetake, Koya*; Ogata, Sho*; Yasuhara, Hideaki*; Aoyagi, Kazuhei; Inui, Toru*; Kishida, Kiyoshi*
Dai-16-Kai Iwa No Rikigaku Kokunai Shimpojiumu Koen Rombunshu (Internet), p.304 - 309, 2025/01
It is very important to predict the extent of EDZ (excavation disturbed zone) and the behavior of hydraulic conductivity after excavation of shafts and tunnels for geological disposal of radioactive waste. In this study, we attempted to reproduce the in-situ tunnel excavation test and the subsequent permeability test at the Horonobe Underground Research Laboratory (URL) using a three-dimensional tunnel excavation simulator. As a result, similar results to the in-situ tests were obtained for the extent of EDZ propagation by excavation and the results of permeability tests. The simulator is effective in predicting the mechanical effects of excavation, coupled phenomena such as deformation and seepage, and hydraulic conductivity in deep mudstones in Japan.
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.
Ogata, Sho*; Yasuhara, Hideaki*; Aoyagi, Kazuhei; Kishida, Kiyoshi*
Proceedings of 53rd US Rock Mechanics/Geomechanics Symposium (USB Flash Drive), 6 Pages, 2019/06
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
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.
Kishida, Kiyoshi*; Sawada, Atsushi; Yasuhara, Hideaki*; Hosoda, Takashi*
Soils and Foundations, 53(1), p.105 - 116, 2013/02
Times Cited Count：27 Percentile：61.36(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.
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.
Sato, Hisashi; Yasuhara, Hideaki*; Sawada, Atsushi
JAEA-Research 2010-069, 45 Pages, 2011/03
JAEA-Research-2010-069.pdf:13.04MB
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.
Yasuhara, Hideaki*; Kinoshita, Naoki*; Kurikami, Hiroshi; Nakashima, Shinichiro*; Kishida, Kiyoshi*
Doboku Gakkai Rombunshu, C, 63(4), p.1091 - 1100, 2007/12
A conceptual model is presented to follow the evolution of permeability in diatomaceous rocks mediated by pressure solution. Specifically, the main minerals of diatomaceous rocks that are quartz, cristobalite, and amorphous silica, are focused to examine differences of the permeability evolutions among them at effective pressures of 1, 5, 10 MPa, and temperatures of 20 and 90 degrees. The rates and magnitudes of permeability reduction increase with increases of the pressures and temperatures applied. Ultimate permeabilities reduced by the order of 90 % at the completion of dissolution-mediated compaction at 10 MPa and 90 degrees. Precipitation may augment more degradation of flow transport in time.
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
Kawata, Kento*; Iwai, Hiromasa*; Yasuhara, Hideaki*; Ogata, Sho*; Suetake, Koya*; Ozaki, Yusuke; Aoyagi, Kazuhei
no journal, ,
no abstracts in English
Kawata, Kento*; Yasuhara, Hideaki*; Iwai, Hiromasa*; Ogata, Sho*; Aoyagi, Kazuhei; Ozaki, Yusuke
no journal, ,
This study investigated the excavation of 350m Niche No.3 of the Horonobe Underground Research Laboratory. A two-dimensional numerical analysis, considering hydro-mechanical coupling effect, was performed to evaluate the excavation damaged zone (EDZ) development. Rock failure was represented by integrating a damage model into the simulator, which rock heterogeneity was represented using a Weibull distribution. Comparative analysis across different degrees of heterogeneity demonstrated that the EDZ expands more significantly in a heterogeneous rock medium than in a relatively uniform one.
