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常盤 哲也*; 青柳 和平; 藤田 朝雄
Rock Mechanics and Rock Engineering; From the Past to the Future (EUROCK 2016), p.901 - 906, 2016/07
Seismic refraction surveys were carried out on the floor of a drift in the Horonobe URL of Japan for understanding of the extent of EDZ. As a result, the extent of the low velocity zone ranges from 1.5 to 3.0 m; the extent on the center line of the drift is the largest. On the other hand, the extent of the EDZ on the drift wall is less than 1.0 m from previous studies. Thus, it is considered that the excavation damage on the drift floor is much larger than that of on the drift wall. Also, the result of the numerical analysis is consistent with that tendency. Furthermore, we also suggest the conceptual model of the EDZ showing the extent, hydraulic and mechanical properties of rock mass, and characteristic of the fracture from the results of this research and previous studies.
青柳 和平; 津坂 仁和*; 野原 慎太郎*; 窪田 健二*; 常盤 哲也*; 近藤 桂二*; 稲垣 大介*
Proceedings of 8th Asian Rock Mechanics Symposium (ARMS-8) (USB Flash Drive), 8 Pages, 2014/10
In a construction of a deep underground facility such as repository for high-level radioactive waste (HLW) disposal, significant changes in hydrogeomechanical properties around a gallery are expected. This zone is called an Excavation Damaged Zone (EDZ). For the safety of HLW disposal, it is necessary to investigate extent and hydrogeomechanical characteristics of an EDZ. In this research, the authors conducted in situ surveys such as seismic refraction survey, geological observation around a gallery, borehole television survey, and hydraulic tests in the Horonobe Underground Research Laboratory. From the results of those surveys, the authors concluded that the extent of the area with high-density of fractures and high hydraulic conductivity was estimated to be about 0.2 to 1.2 m into the gallery wall. The authors also compiled the information of the extent of an EDZ and hydrogeomechanical properties inside and outside of an EDZ as a conceptual model. Since the conceptual models provide the basic idea for determining flow and solute transport in an EDZ, the result of this research provides a useful data for a safety assessment of the HLW disposal.