Consideration on poroelastic behavior of siliceous rock mass around an opening by stress-seepage coupled analysis

Sanada, Hiroyuki; Matsui, Hiroya ; Yamamoto, Takuya*; Aoki, Tomoyuki*; Ogawa, Toyokazu*; Jo, Mayumi*; Fujii, Yoshiaki*

Japan Atomic Energy Agency has been conducting the Horonobe Underground Reseach Laboratory Project as a part of geological isolation research and development at Horonobe-town in Hokkaido, Japan. The rocks around URL have high porosity and low permeability. Therefore, the excess pore pressure caused by URL excavation is possible to affect to the stability of surrounding rock. In this point of view, the authors carried out a stress-seepage coupled analysis to understand the process of the pore pressure change due to excavation and the influence to the stability of surrounding rock and support system. As a result, the large excess pore pressure causes a part in surrounding rock on excavation in an anisotropic initial stress condition and it dissipates with time. The pore pressure change causes the complex deformation in the surrounding rock as well. However, the phenomena are not significant influence to the stability of the surrounding rock and support system.