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Park, Y.-J.*; Sawada, Atsushi; Ozutsumi, Takenori*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Morita, Yutaka*
Proceedings of 3rd International Conference on Discrete Fracture Network Engineering (DFNE 2022) (Internet), 8 Pages, 2022/00
Safety analysis for underground disposal facilities for high-level radioactive waste requires thorough understanding of long-term groundwater flow and nuclide migration processes in geologic media. In the coastal subsurface systems, groundwater flow is defined by the complex interactions between freshwater of meteoric origin and denser saline water from the sea. In addition, sea levels are expected to fluctuate significantly due to a transgression and regression of the sea over the millions of years for safety analysis. This study presents long-term evolution of groundwater environment such as salinity concentration and flow velocity with focus of the interaction between fractures and matrix blocks in regional and near-field scale analysis framework for groundwater flow and nuclide migration for underground disposal facilities in hypothetical fractured crystalline coastal systems.
Saegusa, Hiromitsu; Onoe, Hironori; Ishibashi, Masayuki; Tanaka, Tatsuya*; Abumi, Kensho*; Hashimoto, Shuji*; Bruines, P.*
JAEA-Research 2015-011, 59 Pages, 2015/10
JAEA-Research-2015-011.pdf:49.44MB
It is important to evaluate groundwater flow characteristics on several spatial scales for assessment of long-term safety on geological disposal of high-level radioactive wastes. An estimation of hydraulic heterogeneity caused by fracture network is significant for evaluation of the groundwater flow characteristics in the region of tens of meters square. Heterogeneity of equivalent hydraulic properties is needed to estimate for evaluation of the groundwater flow characteristics in the region of several km square. In order to develop the methodology for multi-scale hydrogeological modeling taking into account the hydraulic heterogeneity, spatial distribution of fractures and their hydraulic properties have been modeled using discrete fracture network (DFN) model. Then, hydrogeological continuum model taking into account the hydraulic heterogeneity has been estimated based on the DFN model. Through this study, the methodology for multi-scale hydrogeological modeling according to type of investigation data has been proposed.
Bruines, P.*; Tanaka, Tatsuya*; Abumi, Kensho*; Hashimoto, Shuji*; Saegusa, Hiromitsu; Onoe, Hironori; Ishibashi, Masayuki
Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 10 Pages, 2014/10
Bruines, P.*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Kuzuha, Yuji; Onishi, Yuzo*
Proceedings of 7th Asian Rock Mechanics Symposium (ARMS-7) (USB Flash Drive), p.692 - 701, 2012/10
This paper describes the characterization of the rock mass and how data obtained has been used to make a discrete fracture network (DFN) model and to calculate an up-scaled equivalent continuous porous media model for the purpose of numerical simulation of the grout injection process. DFN models have been constructed using mainly the BTV and hydraulic test data from the boreholes drilled in this project. The generated DFN model and the up-scaled model was able to reproduce the measured fracture characteristics as well as the hydraulic behavior observed in the field and has proven to be suitable for modeling grouting behavior. DFN model has been gradually refined step by step with the site characterization stages: the preparative stage in 2009, pre-investigation stage in 2010 and grouting test stage in 2011. Each version of the DFN model shows the understanding of the geological environment and identifies issues to be resolved in the next stage. The DFN models proved to be an essential tool for the site characterization program planning process, such as identifying the best layout of subsequent boreholes and placement of test intervals.
Ando, Kenichi*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Saegusa, Hiromitsu; Onoe, Hironori
JAEA-Research 2012-022, 60 Pages, 2012/08
JAEA-Research-2012-022.pdf:8.51MB
In this study, water conducting features in Toki granite were defined by the interpretation and integration of geological and hydrogeological data obtained from the borehole investigation in the Phase I of the MIU Project and Regional Hydrogeological Study. Then, the hydrogeological model of Block scale was constructed using hydraulic discrete fracture networks, and equivalent hydraulic conductivities in Block scale were calculated. And, adequacy of equivalent hydraulic conductivities in Block scale was confirmed using result of hydraulic packer tests.
Inagaki, Manabu*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Maekawa, Keisuke; Shibata, Masahiro
JAEA-Research 2011-056, 37 Pages, 2012/03
JAEA-Research-2011-056.pdf:8.64MB
In Japan, a step-wise approach is applied in the site selection process for the geologic disposal site. Preliminary surface-based investigations will be followed by detailed investigations. The basic repository concept, including underground design and layout, will be discussed at the end of surface-based investigations. The repository concept will depend on the spatial extent of the candidate rock formation(s) and their barrier performance. However, information obtained from the surface is limited and includes uncertainties. It is thus important to assess host rock performance considering uncertainties. In this study, methodology for evaluation of geological conditions has been developed that focuses on determining the usable volume of host rock with specific performance characteristics. Initially, multiple performance indices have been discussed and defined from the viewpoint of barrier performance. Then the evaluation procedure is illustrated by using the dataset obtained from the Horonobe Underground Research Laboratory Project. Finally the proposed procedure is reviewed and future challenges are extracted.
Tanaka, Tatsuya*; Bruines, P.*; Abumi, Kensho*; Hashimoto, Shuji*; Kuzuha, Yuji; Onishi, Yuzo*
Dai-41-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koenshu (CD-ROM), p.77 - 82, 2012/01
This study aims to establish grouting techniques and evaluation of the effects of grouting in the geological environment of crystalline rock. A hydrogeological model has been generated using discrete fracture networks based on the data obtained by the short-borehole investigation campaign performed at at Grimsel test site in Switzerland to support the design of planned in-situ grouting test. The equivalent porous media with the consideration of hydraulic heterogeneity has been created from the DFN (Discrete Fracture Network) in order to be provided for the simulation of the grout injection process. Uncertainties and remaining issues associated with the assumption in interpreting the data and its modeling were addressed in a systematic way.
Abumi, Kensho*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Nakanishi, Tatsuro; Tsuda, Hidenori
Doboku Gakkai Heisei-23-Nendo Zenkoku Taikai Dai-66-Kai Nenji Gakujutsu Koenkai Koen Gaiyoshu (DVD-ROM), p.73 - 74, 2011/09
no abstracts in English
Kawamura, Hideki*; Ando, Kenichi*; Noda, Masaru*; Tanaka, Tatsuya*; Matsuda, Takeshi*; Fujii, Haruhiko*; Hashimoto, Shuji*; Ueda, Tadashi*; Matsui, Hiroya; Takeuchi, Shinji; et al.
JAEA-Technology 2009-081, 182 Pages, 2010/03
JAEA-Technology-2009-081.pdf:28.89MB
Grouting has practical importance for the reduction of groundwater inflow into excavations during construction of underground facilities. Considering the performance assessment of a radioactive waste repository, the performance of the engineered barrier system could be adversely affected by a high pH plume generated from grout. Therefore, a quantitative estimation of the effectiveness of grouting and grout material is essential. This study has been performed in the Mizunami URL being excavated in crystalline rock as a part of the Project for Grouting Technology Development for the Radioactive Waste Repository funded by METI, Japan. The aims were to evaluate the applicability of existing grouting technology and to develop methodology to determine the distribution of grout and change in hydraulic properties of the grouted rock volume. The target rock is the volume of rock around a planned refuge niche where the pre-excavation grouting was performed at 200-m depth from ground surface. After excavation of the refuge niche, ten boreholes were drilled and different kinds of investigations were carried out during and after drilling. The results were integrated and groundwater flow analysis of pre and post excavation grouting conditions were carried out to estimate quantitatively the effect of pre-excavation grouting. The results suggest that current pre-excavation grouting technology is effective for reduction of groundwater inflow into excavations and that hydraulic conductivity of the surrounding rock can be reduced by more than one order of magnitude.
Tanaka, Tatsuya*; Matsui, Hiroya; Hashimoto, Shuji*; Ando, Kenichi*; Takeuchi, Shinji; Saegusa, Hiromitsu
Dai-38-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.143 - 148, 2009/01
This study aims to establish techniques for grouting, and evaluation of the effects of grouting on the geological environment, to be applied in the field of high level radioactive waste disposal in the deep underground. A block-scale hydrogeological model has been generated using discrete fracture networks based on data obtained from the short-borehole investigation campaign performed at the research tunnel around which grouting has been carried out. The grouting performance in terms of reducing the water inflow rate was evaluated by groundwater flow simulation. Lessons learned applicable to future studies of in-situ testing have been addressed.
Ando, Kenichi*; Takeuchi, Shinji; Matsui, Hiroya; Tanaka, Tatsuya*; Hashimoto, Shuji*; Fujii, Haruhiko*
Dai-38-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.137 - 142, 2009/01
Evaluation of the effect of grouting on the geological environment is important for quality control of the design and management of the construction of underground facilities for high level radioactive waste disposal. Lugeon test has been commonly used to check the hydraulic characteristics around borehole whether or not to inject grout in Japan. The aim of this study is to develop a hydraulic test which can be applied to obtain hydraulic conductivities of low permeable rockmass (e.g. 10
to 10
m/s) during grouting. The proposed hydraulic test with the test sequence of water injection and pressure recovery has been carried out in Mizunami URL excavated in crystalline rock. The developed type curve matching methodologies have been applied to evaluate hydraulic conductivity in-situ in a simple manner. Lessons learned for future application for grouting have been addressed.
Tanaka, Tatsuya*; Ando, Kenichi*; Hashimoto, Shuji*; Saegusa, Hiromitsu; Takeuchi, Shinji; Amano, Kenji
Dai-36-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.267 - 272, 2007/01
no abstracts in English
Hashimoto, Shuji*; Tanaka, Tatsuya*; Ando, Kenichi*; Takeuchi, Shinji; Saegusa, Hiromitsu; Kim, H.*
Dai-36-Kai Gamban Rikigaku Ni Kansuru Shimpojiumu Koen Rombunshu (CD-ROM), p.419 - 424, 2007/01
no abstracts in English
Futakuchi, Katsuhito*; Hashimoto, Shuji*; Sakuramoto, Yuji*; ; Kamei, Gento
JNC TN8400 2001-007, 52 Pages, 2001/04
JNC-TN8400-2001-007.pdf:2.34MB
As a natural analogue, the authors investigted a Tertiary argillaceous bed and a Quarternary hypabyssal rock (porphyrite) which intruded into the argillaceous rock, distributed in the Nishikubiki district of Niigata prefecture in Japan. We examined the variation of clay mineral species in the argillaceous rock surrounding the intrusive rock and carried out thermal analyses for the argillaceous rock based on the coolig history of the intrusive rock. The predominant clay mineral varied from montmorillonite to illite through illite/montmorillonite interlayers with approaching to the intrusive rock. The thermal analyses indicated that the temperature descended from 270 to 15 
C during the 7.5
10
years at alocalty of argillaceous rock containing 75% illite in the interlayers. On the assumption that the alteration from montmorillonite to illite was regarded as a first-order reaction, we evaluated the apparent activation energy based on the thermal condition mentioned above; about 103 kJ/mol was obtained for this illitization. This was within the range of values reported previously by laboratory experiments and/or examinations of natural illitizations.
Futakuchi, Katsuhito*; *; *; *; Hashimoto, Shuji*
JNC TJ8400 99-044, 72 Pages, 1999/02
The alteration characteristics of volcanic glass and bentonite and immobility of iodine in geological medium are investigated as a part of the natural analogue study of geological disposal of high-level radioactive waste. For the study of volcanic glass, volcanic ashes (08) are collected at Kamogawa area in Chiba Prefecture which ejected Pleistocene (ca. 1.0 Ma.) to examine the hydration in underground condition. Optical analysis, espetially reflaction index measurement show that volcanic ashes (08) were wholly hydrated. For the study of bentonite, marine argillaceous rocks in Nishikubiki area, Niigata Prefecture have been studied to determine the thermal history of this area. In order to estimate the temperature on contact of inturusive body and argillaceous rocks, measurement of homoginized temperature of fluid inclusion and observation under the optical microscope. For the study of iodine immobility in geological medium, iodine-bearing groundwater in Mobara Gas field, Chiba Prefecture, were discussed.
Futakuchi, Katsuhito*; Sakuramoto, Yuji*; *; *; *; Hashimoto, Shuji*
PNC TJ1308 98-001, 103 Pages, 1998/02
None
Hashimoto, Shuji*; Saegusa, Hiromitsu; Tanaka, Tatsuya*; Ando, Kenichi*; Bruines, P.*
no journal, ,
It is useful to estimate profiles of the equivalent hydraulic conductivity for groundwater flow modeling based on an equivalent porous medium approach that are used for hydrogeological characterization at over the several kilometers scale. In this study, a combined interpretation of core observations, BTV and fluid logging has been used to identify and classify water-conducting features (WCFs) among observed fractures in deep boreholes around the MIU construction site in Phase I. Transmissivity profiles of WCFs were determined by the interpretation of fluid logging and the results of short interval packer tests. An equivalent hydraulic conductivity for the sub-divided block is calculated using a hydraulic discrete fracture network (hydroDFN) model based on the information, and is confirmed the validity using long interval packer test results. Groundwater flow analyses using developed hydroDFN model are also carried out to assess groundwater flow conditions around galleries.
Yoshimura, Kimitaka*; Wakamatsu, Hisanori*; Ando, Kenichi*; Hashimoto, Shuji*; Yabuuchi, Satoshi; Shigeta, Naotaka
no journal, ,
no abstracts in English
Maekawa, Keisuke; Saegusa, Hiromitsu; Matsuo, Shigeaki*; Hashimoto, Shuji*; Ando, Kenichi*
no journal, ,
no abstracts in English
Maekawa, Keisuke; Inagaki, Manabu*; Tanaka, Tatsuya*; Hashimoto, Shuji*; Matsuo, Shigeaki*
no journal, ,
no abstracts in English