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JAEA Reports

Study for development of the methodology for multi-scale hydrogeological modeling taking into account hydraulic heterogeneity caused by fracture network

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.

Journal Articles

Development and application of the GeoDFN and HydroDFN at the Mizunami Underground Research Laboratory

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

Journal Articles

Development of grouting technologies for HLW disposal in Japan, 3; Development of a hydrogeological model using discrete fracture network

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.

Journal Articles

The JAEA grouting test at the Grimsel test site; Numerical simulation of the grout injection process of silica sol in fractured rock mass

Koyama, Tomofumi*; Onishi, Yuzo*; Bruines, P.*; Tanaka, Tatsuya*; Hasui, Akinori*; Katayama, Tatsuo*; Kishi, Hirokazu; Kuzuha, Yuji

Proceedings of 2012 ISRM International Symposium; Rock Engineering and Technology for Sustainable Underground Construction (EUROCK 2012) (USB Flash Drive), 10 Pages, 2012/05

Grouting, which involves injection of grout material, is commonly used to decrease the hydraulic conductivity of the fractured rock masses and control the groundwater inflow. However, the mechanism of grout injection process has not been clarified sufficiently yet due to complicated chemical and physical processes of grout. In this study, to simulate the grout injection process, the three-dimensional numerical model based on equivalent continuum approach was developed.

Journal Articles

The JAEA grouting test at the Grimsel test site; Site characterization of a fractured rockmass and preparation of DFN model and its equivalent continuous porous media model

Bruines, P.*; Tanaka, Tatsuya*; Koyama, Tomofumi*; Kishi, Hirokazu; Nakanishi, Tatsuro; Onishi, Yuzo*

Proceedings of 2012 ISRM International Symposium; Rock Engineering and Technology for Sustainable Underground Construction (EUROCK 2012) (USB Flash Drive), 15 Pages, 2012/05

To better understand the grouting process and the effect of grouting on the performance of a nuclear waste repository, the Japanese Atomic Energy Agency (JAEA) has initiated a grouting test carried out in the fractured granite of the Grimsel Test Site (GTS) located in the Swiss Alps. This paper describes the characterization of the rock mass, how the data obtained has been used to make a discrete fracture network (DFN) model and how an up-scaled equivalent continuous porous media (ECPM) model for the purpose of numerical simulation of the grout injection process is generated. The generated DFN model and the up-scaled ECPM model was able to reproduce the measured fracture characteristics (e.g. orientation, density) as well as the hydraulic behavior observed in the field (e.g. transmissivity distribution, anisotropy, heterogeneity) and has proven to be suitable for modeling grouting behavior.

Journal Articles

Development of grouting technologies for geological disposal of high level waste in Japan, 2; Hydrogeological descriptive modeling by discrete fracture network in crystalline rock mass test site

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.

Oral presentation

Re-interpretation of the fluid electric conductivity measurements carried out in the MIZ-1 borehole at the Mizunami Underground Research Laboratory project

Bruines, P.*; Ando, Kenichi*; Niibori, Yuichi*; Matsuoka, Kiyoyuki*; Takeuchi, Shinji

no journal, , 

Fluid electric conductivity (FEC) measurements have been carried out in the 1,350 m long MIZ-1 borehole followed by the modeling of FEC curve with newly developed finite difference code and obtaining tranmissivity in each feed point from FEC logging. The obtained results are comparable to those obtained by hydraulic testing. The method can be valuable to help in the selection of locations for more detailed hydraulic tests. Under certain circumstances the method can be used as a low cost alternative to hydraulic testing.

Oral presentation

Estimation of upscaled hydraulic conductivity profiles along a borehole in low permeability crystalline rock using discrete fracture network models

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.

Oral presentation

The Project for grouting development for high level radioactive waste repository, 6; Study of fracture modeling in the crystalline rock site

Tanaka, Tatsuya*; Abumi, Kensho*; Bruines, P.*; Kishi, Hirokazu; Kuzuha, Yuji

no journal, , 

no abstracts in English

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