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青柳 和平; 常盤 哲也*; 藤田 朝雄
Rock Mechanics and Rock Engineering; From the Past to the Future (EUROCK 2016), p.1023 - 1028, 2016/07
In excavation of a repository for high-level radioactive waste, it is important to limit the extent of the excavation damaged zone (EDZ) with efficient excavation rate. The objective of this study is to reveal the relationship among the extent of the EDZ, excavation direction related to in situ stress orientation, and excavation rate in detail. From the result of seismic refraction survey, the extent of the EDZ is estimated within 0.5 m into the gallery wall. The excavation rate of the gallery excavated almost parallel to the maximum principal stress was 1.1 to 1.3 times faster than that of the gallery excavated almost perpendicular to the maximum principal stress. Considering the excavation rate, fracture length, and the extent of the EDZ, excavation of galleries parallel to the maximum principal stress leads to limit the development of the EDZ with efficient excavation.
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.