Excavation damaged zone inferred by geophysical surveys on drift floor of Horonobe URL

幌延深地層研究センターの坑道底盤下の掘削損傷領域に関する物理探査に基づく検討

常盤 哲也*; 青柳 和平  ; 藤田 朝雄 

Tokiwa, Tetsuya*; Aoyagi, Kazuhei; Fujita, Tomoo

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.