Numerical simulation of excavation damaged zone under coupled thermal-mechanical conditions with varying mechanical parameters

Understanding of the formation and subsequent spatial and temporal evolution of excavation damaged zone (EDZ) under coupled thermal-mechanical (TM) conditions is of great importance for evaluating the long-term performance of underground radioactive waste repository. Thermal stress induced damage and temperature-dependent rock parameter change are two main ways that thermal effects influence the mechanical parameters of rock under TM conditions. This paper begins with formulation of a coupled thermal-mechanical (TM) model based on elastic damage principle. Next, the model is numerically implemented and validated against theoretical solution and some existing experimental observations. Finally, damage zone evolution in a granite specimen under a variety of thermal and mechanical conditions is numerically simulated, where the influence of elevated temperature on the rock parameters such as elastic modulus and strength is taken into account. It is noted that the damage zone is dominantly controlled by the lateral pressure coefficients, and the thermal effect may promote the tensile damage and restrain the shear damage. In particular, temperature-induced parameter change is also an important way causing rock damage, and the final damage pattern of rock depends on the combined loading path of elevated temperature and external loading.