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Tokiwa, Tetsuya; Ishii, Eiichi; Funaki, Hironori; Tsusaka, Kimikazu; Sanada, Hiroyuki
Proceedings of 3rd International Workshop and Conference on Earth Resources Technology 2009 (CD-ROM), p.159 - 168, 2009/12
Japan Atomic Energy Agency has been constructing underground facilities since 2005 in the Horonobe area. Before the construction, the rock stress was measured by the hydraulic fracturing method using boreholes. In this area, the result showed that the direction of the major horizontal principal stress was in E-W direction. On the other hand, in shaft excavation, the direction of the predominant diameter reduction was observed in NNE-SSW to NE-SW direction. The difference would be attributed to the fact that fault system in the rock affects the deformation of shaft. The authors applied fault-striation analysis with faults identified on drilling cores. The direction of the major principal stress estimated by fault-striation analysis approximately corresponds to the predominant directions of the deformation caused by the shaft excavation. The result shows that fault system affects rock mass behavior in shaft excavation.
Yokota, Hideharu; Tomura, Goji; Maekawa, Keisuke
Proceedings of 3rd International Workshop and Conference on Earth Resources Technology 2009 (CD-ROM), p.169 - 178, 2009/12
Japan Atomic Energy Agency has been carrying out Horonobe Underground Research Laboratory Project for understanding of characteristics of the geological environment as a part of research and development programs on geological disposal of high-level radioactive waste. As developing techniques for long-term monitoring of geological environment, we have been measuring the groundwater pressure using boreholes in order to monitor any influences due to the construction of the underground facilities. The results from examination of relations with the data of the long-term monitoring of groundwater pressure, geological characteristics obtained from the drilling cores, logging data and hydraulic characteristics of the boreholes suggest the existing of the continuative hydrogeological structure at the neighborhood of a feature geological boundary, and that the distribution of continuative hydrogeological structures around the underground facilities depends on the geological characteristics not the depth from ground level.
Sanada, Hiroyuki; Sugita, Yutaka; Fujii, Yoshiaki*
Proceedings of 3rd International Workshop and Conference on Earth Resources Technology 2009 (CD-ROM), p.149 - 158, 2009/05
EDZ is considered to be important issues in repositories since this is relevant to plug design, support design etc. As a part of the research and development on the geological isolation, JAEA has been implementing the Horonobe URL Project. Deformation and failure behavior around a shaft in URL is described in the paper. Tunnel shape are being measured by a laser displacement sensor to clarify dimension and mechanism of breakouts along the shaft wall. Displacement measurement by extensometers are being carried out to understand deformation behavior in the surrounding rock mass. Breakouts of about 50 cm deep in N-S direction are more frequently observed with excavation depth. The breakout direction was consistent with the maximum horizontal stress which was estimated to be approximately in E-W direction by hydrofracturing tests. Compressive deformation of rock mass also increased with excavation depth. Most part of the deformation occurred within 1 m from the shaft wall.