Prediction analysis of the development of the excavation damaged zone around the gallery excavated at 500 m depth at Horonobe Underground Research Laboratory

Aoyagi, Kazuhei  ; Tamura, Tomonori ; Ozaki, Yusuke  ; Ishii, Eiichi   ; Motoshima, Takayuki*; Sugawara, Kentaro*

In a high-level radioactive waste disposal, it is important to understand the extent of the Excavation Damaged Zone (EDZ) because it can be one of the factors to determine whether disposal galleries or pits can be excavated or not in the design or construction phases. In this study, we performed a hydro-mechanical coupling analysis to simulate the three-dimensional excavation of the twin galleries which were excavated at a depth of 500 m in the Horonobe Underground Research Laboratory. The analysis revealed that the EDZ was developed 1.5-2.0 m from the gallery wall. The stress acting on the shotcrete was within the ultimate limit state. Based on these results, we estimated that the stability of the twin galleries will be maintained, despite the relatively large extent of the EDZ.