Fracture Characteristics of Granite Specimens after Heating-Cooling treatments: Insights from Experiments and GBM Simulations

The investigation of the fracture mechanical properties of granites after thermal cycling is of great significance for improving the operational stability of Enhanced Geothermal Systems (EGS) and optimizing the exploitation efficiency of hot dry rock (HDR). However, the mechanical responses of granite specimens after heating–cooling treatments have not been fully investigated. In this study, experiments and simulations were employed to analyze the effects of different temperature (200, 400, and 600 ℃) and number of cycles (5, 10, 15, and 20 cycles) on granite specimens. The results show that with the increasing temperature and number of cycles, the peak strength and Mode I fracture toughness degrade, and the mechanical behavior gradually transitions from brittle fracture to ductile yielding. Cyclic thermal treatments lead to the formation and propagation of thermal cracks, which coalesce with the primary cracks, forming a crack network. This process results in the deterioration of the internal structure of the rock, altering the distribution of force chains and making the crack propagation path more complex, with an increase in the roughness of the fracture surfaces. This study helps to better understand the mechanism of fracture mechanics of HDR.