Experimental Investigation and Semi-Analytical Simulation of Instantaneous and Time-Dependent Damage Behaviors of Beishan Granite

In the context of China’s deep geological disposal program for high-level radioactive waste, the short- and long-term mechanical behaviors of the host rock, Beishan granite, are investigated experimentally and numerically. Conventional triaxial compression tests and multi-stage creep tests with different confining pressures are performed upon cylindrical samples. It is shown that the rock presents typical brittle behaviors with the peak strength affected by the confining pressure and that creep behaviors depend significantly on the level of deviatoric stress. For constitutive modeling, a micromechanical friction-damage coupling model is presented and its suitability for Beishan granite is demonstrated. Salient features of the model include the formulations based on the Mori-Tanaka homogenization method, a back stress-type unified hardening/softening law, an associated flow rule, etc. The test results we obtained are simulated analytically. In addition, creep damage is viewed as the consequence of subcritical cracking and also treated in the damage-friction coupling framework. Originally, semi-analytical simulations of the creep tests are reported with a satisfactory agreement.