Investigation of thermal-induced damage in fractured rock mass by coupled FEM-DEM method

In this study, a 3D coupled FEM-DEM method was adopted to study the influence of thermal-induced damage on the mechanical properties of fractured rock mass. In this method, the rock matrix was discretized into bulk elements bridged by cohesive elements, and the preexisting fractures were represented by cohesive elements. The thermal-induced damage process was modeled through two parts, i.e., thermal conduction and thermal-mechanical coupling. For thermal conduction process, a proposed 3D thermal-cohesive coupled model with a fracture aperture-dependent interfacial thermal conductivity was adopted to simulate the thermal conduction across the fractures, which make it possible to more precisely predict the temperature distribution. Then, the thermal stress induced by temperature variation was coupled to perform the mechanical-failure calculation. Validation simulations indicated that the proposed model is capable of dealing with the thermal-induced damage problems. Then, the influences of fracture aperture on thermal-induced damage in highly fractured rock mass were numerically investigated by the Brazilian disc tests with multiple randomly distributed fractures. The results indicated that as the fracture aperture increases, the area of thermal-induced damage zone increases and the Brazilian tensile strength (BTS) decreases nonlinearly.