Abstract: The high-level radioactive waste geological repository is in a multi-field coupling environment of thermo-hydro-mechanics (THM), and multi-field coupling analysis is required when performing safety assessment on the high-level waste repository. However, the excavation of the high-level radioactive waste repository causes the stress redistribution of the surrounding rock near the wall, consequently generates damage and results in changes in the thermal parameters (T), seepage parameters (H) and mechanical parameters (M) of the surrounding rock. These THM coupling parameters thus show inhomogeneous spatial distributions, which will have a significant impact on the THM coupling evolution process during the operational period of repository. By analyzing the coupling mechanism of thermo-hydro-mechanics of high-level radioactive waste repository, and the distribution and evolution law of surrounding rock damage in repository, the damage variable and damage evolution criterion are defined. The damage variable is related to thermal parameters, seepage parameters, mechanical parameters and multi-field coupling parameters (Biot coefficient, Biot modulus and temperature drainage coefficient) and then the damage of surrounding rock is linked with thermo-hydro-mechanical fields. An elastoplastic damage thermo-hydro-mechanical multi-field coupling numerical model is established. Then, the established model is used to simulate the surrounding rock heating test of the high-level waste geological repository in Mont Terri, Switzerland. The numerical and experimental values are compared, the effect of excavation-induced damage on evolution of temperature field, seepage field and stress field are discussed, and the evolution law of excavation-induced damage under multi-field coupling is also analyzed.

Key words: high-level radioactive waste, barrier system, multiphysics coupling problem, elastoplastic, excavation damage