Improved damage model with thermal-mechanical effects based on modified M-C criterion

During geothermal resource development, the mechanical properties of surrounding rock minerals can be adversely affected by temperature variations. To better understand the deformation and mechanical behaviour of rocks under high temperatures, a modified Mohr–Coulomb (M-C) strength criterion is proposed. This criterion incorporates a parameter for rock deformation damage, and is combined with statistical damage theory to derive a comprehensive damage expression. The resulting model considers high temperature and loading conditions before and after the threshold stress, and takes into account post-peak morphology. To validate the model, adopting a thermo-mechanical coupling rock mechanics apparatus to analyse the mechanical properties of quartz sandstone across a temperature range of 20°C–800°C. Comparative analysis between the model’s calculated values and test data obtained from the experimental setup indicates good agreement, with minimal overall deviation. This suggests that the improved model and its calculation method provide a more accurate representation of the deformation and mechanical behaviour of rocks subjected to high temperatures and loading conditions.