Numerical Simulation of Dynamic Mechanical Behavior and Damage Evolution Mechanisms in Granite Following High‐Temperature Water‐Cooling

ABSTRACT To investigate the influence mechanism of high‐temperature water‐cooling on the dynamic mechanical behavior of granite, a combined approach of impact loading experiments and discrete element simulations was employed. The study systematically analyzed the dynamic fracture behavior and thermo‐mechanical damage mechanisms of granite after high‐temperature water‐cooling treatment. The results indicate that heat‐treatment temperature and impact velocity exert a synergistic influence on the dynamic response of granite. A critical temperature of approximately 450°C was identified for dynamic peak stress: below this threshold, the stress variation remains moderate, while above it, a sharp decrease occurs. Increasing impact velocity significantly enhances the strain‐rate effect; however, this effect is weakened under high‐temperature conditions. An inflection point in the proportion of dissipated energy appears near 600°C, and the failure mode transitions from blocky splitting at low temperatures to pulverized fragmentation at high temperatures. A thermo‐mechanically coupled grain‐based model (GBM) was developed to reproduce the experimental observations, revealing that the rapid increase in transgranular cracks beyond 450°C leads to a sharp reduction in crack initiation stress. By distinguishing the respective contributions of intergranular and transgranular cracking, a thermo‐mechanical damage evolution model was established. The analysis shows that intergranular cracks dominate in the low‐temperature stage, whereas transgranular cracks become predominant at higher temperatures, resulting in intensified damage. This study provides a theoretical foundation for the safety assessment of deep geothermal energy exploitation.