Thermally induced failure process of brittle rocks based on a thermo-mechanical coupling model

Abstract

The thermal expansion and the extraction characteristics of a rock are observed in a common phenomenon caused by the rock’s exposure to significant temperature differences. A thermally induced rock damage is a complex process full of uncertain physical and mechanical processes. Hence, investigating the mechanism of brittle materials is significant for both scientific and engineering applications. This study proposes a thermo-mechanical coupling model based on a continuous–discontinuous element method to simulate the thermal cracking processes in brittle rocks. In this micro-mechanical model, the rock matrix is simulated as an assembly of blocks bonded to each other. A spring model is employed to model the contacts in the blocks to simulate the mechanical deformation properties, while a thermal model is applied between their bonds to simulate heat conduction. The model validity is verified herein. Furthermore, the cracking process of brittle materials under the thermal stresses caused by the temperature gradient is studied using a thick-wall cylinder model. Consequently, the simulation results show that the microscopic crack initiation and propagation processes can be reasonably simulated at the cooling stage using the thermo-mechanical coupling model. Different geological and operation conditions are also further studied to reveal their effects on the patterns of induced fractures. This study provides a possible method for analyzing the thermal damage process and mechanism of brittle materials.