A Study of efficient excavation limiting the extent of an excavation damaged zone in Horonobe URL

幌延深地層研究センターにおける掘削効率と掘削損傷領域の定量的関係の検討

青柳 和平  ; 常盤 哲也*; 藤田 朝雄 

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

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.