Experimental study on Brazilian splitting characteristics of heat damaged hot dry granite

In the process of geothermal exploitation in dry-hot granite reservoirs, the heat exchange and cooling of the reservoir can cause thermal damage to high-temperature rocks, directly affecting the mechanical properties of the reservoir rocks. To achieve the co-extraction of deep geothermal resources and minerals, the evolution law of the splitting characteristics of thermally damaged dry-hot granite has been explored. Taking the deep granite in Yantai, Shandong as the research object, thermal shock treatment was conducted, combined with the Brazilian splitting test and digital image processing technology to monitor the initiation, propagation, and penetration of rock surface fractures. The experimental results show that the thermal damage process changes the microstructure of the rock, leading to two types of crack initiation patterns during the splitting process. Temperature has a significant impact on the longitudinal wave velocity and indirect tensile strength of the rock, both of which gradually decrease with increasing temperature. Within the range of 450~600℃, there is a temperature threshold at which the decrease in the longitudinal wave velocity and indirect tensile strength of the rock is most significant, and a linear relationship is observed.