Study on crystalline rock aiming at evaluation method of long-term behavior of rock mass; FY2014 (Contract research)

Fukui, Katsunori*; Hashiba, Kimihiro*; Sato, Toshinori  ; Kuwabara, Kazumichi; Takayama, Yusuke  

With respect to high-level radioactive waste disposal, knowledge of the long-term mechanical stability of shafts and galleries excavated in rock is required, not only during construction and operation but also over a period of thousands of years after closure. On the other hand, it is known that rock and the rock mass surrounding the disposal gallery shows time dependent behavior such as creep or the stress-relaxation. It becomes the issue in the stability evaluation of the disposal gallery to grasp the behavior. About this issue, we pushed forward research development. In the fiscal year of 2014, the creep test was continuously conducted and the total testing time exceeded 17 years. The testing equipment and procedure were examined to investigate the deformation, failure and time-dependency of rock under wet conditions and between room temperature and 100C. The long-term strength of rock under triaxial stress state was researched with the aid of laboratory testing results and in situ stress measurement.