Abstract
The excavation of underground openings results in a change in stress distribution which may lead to the development of a plastic zone around the tunnel, termed as excavation disturbed zone. To characterize the behavior of excavation disturbed zone as well as host rock, time influence on the mechanical properties of rock is of great importance. For instance, when considering deep excavations for disposal of high-level radioactive waste in rocks, assessment of the timedependent stability of rock mass under deep geological environment is necessary. With this in mind, creep tests were carried out on Inada granite under confining pressure: 40 and 80 MPa for dry and wet samples. The conclusions are summarized as follows:
1) Shear zone developed just before tertiary creep is similar to the onset of the macroscopic failure under conventional loading condition (short term).
2) Crack evolution decreases with confining pressure increasing. Furthermore, presence of water accelerates the cracks growth.
3) Time to failure depends on the clay mineral content. In other words, in underground spaces, clay content of surrounding rock is considerably influenced the long-time stability of the site.
