Study on the effect of high-temperature dry-wet cycles on argillaceous sandstone

In the process of geothermal energy development, there is groundwater vapor condensation, and the rock is in an alternating dry and wet environment, so it is of great significance to study the influence of high temperature dry and wet cycle on argillaceous sandstone. In this study, the argillaceous sandstone samples were heated at 200 & DEG;C after saturation with water and subjected to 120 drying-wetting cycles to study the damage characteristics of rock under high-temperature drying-wetting cycles. The changes in the damage characteristics of rock samples were monitored by acoustic emission (AE). The results highlighted that during the heating stage, there was a decrease in the continuity of thermal AE signal and an increase in the signal strength with an increase in the number of cycles. During the constant temperature stage, the intensity of the thermal AE signal was weak through 0-40 cycles and subsequently increased significantly with the increase in the number of cycles. There was a gradual increase in the number, length, and width of fractures on the surface of argillaceous sandstone with the increase in the number of cycles. The surface fracture rate increased linearly, reaching 2.8% after 120 cycles, forming a fracture network. According to the changes observed in the saturated water absorption rate, the process of fracture development can be divided into the initiation stage (0-40 cycles), expansion stage (41-80 cycles), and penetration stage (81-120 cycles). Moreover, there was an increase in the saturated water absorption rate and loss of mass in each stage with the increase in the number of cycles. This study can provide a theoretical basis for the development of geothermal resources.