Phenomenological study on crystalline rock for evaluating of long-term behavior (Contract research)

Okubo, Seisuke*; Hirano, Toru; Matsui, Hiroya 

On the radioactive waste disposal, the long-term mechanical stability of tunnel was required. Therefore, we have been developing the method evaluating the stability. This report describes the works in the FY2008. Chapter 1 is the overview. Chapter 2 is the result of long-term creep test on Tage tuff. The strain was increasing at very low speed and the strain rate was decreasing following elapsed time to the powers of -0.9. This behavior is likely to short-term creep. In Chapter 3, the control program was extended to conduct the generalized relaxation test along any relaxation pattern. Then, that test of Toki granite was carried out successfully. The parameters in the variable-compliance-type constitutive equation for Toki granite were deduced. In Chapter 4, parameter-obtaining methods for the constitutive equation were reviewed and criticized. In the final part, an idea of new rock characterization where time-dependent behavior of rock is considered as the important factor was proposed.