Simulation Study on the Damage and Deterioration Mechanisms of Sandstone under Different High-Temperature Effects

The development and utilization of geothermal resources hold significant strategic importance for alleviating energy pressure in China. Accurately understanding the damage and fracture behavior of sandstone under high-temperature conditions is key for promoting geothermal development. This paper simulates uniaxial compression tests of sandstone after high-temperature treatment by constructing a grain-based model(GBM) within the particle flow code (PFC), investigates the characteristics of the thermal crack distribution in sandstone after-high-temperature exposure, analyses the evolution of its strength and deformation parameters with temperature, and discusses the crack propagation behavior during uniaxial compression. The results indicate that the GBM unit can effectively reflect the variations in sandstone strength and fracture behavior with temperature. As the temperature increases, grain boundary cracks transition from a discrete distribution to eventually coalesce, forming macroscopic cracks. When the temperature reaches 500°C, a significant number of transgranular cracks appear. During uniaxial compression at room temperature, the sample initially generates discretely distributed grain boundary cracks. In contrast, at 500°C, microcrack propagation is more extensive, and intergrain sliding occurs during loading; however, the macroscopic failure of the sample is ultimately dominated by the propagation of transgranular cracks. This study reveals the damage and degradation mechanisms of high-temperature sandstone from a mesoscopic perspective, providing an important theoretical basis for ensuring the safety and efficiency of geothermal extraction.