Study on Kaiser effect of granite under cyclic loading and unloading at different temperatures

During the tunneling process in high-temperature environments, the surrounding rock mass is subjected to periodic pressurization and depressurization, making it prone to instability and failure. To investigate the damage and failure of high-temperature rock under cyclic loading-unloading, uniaxial cyclic loading-unloading tests and ABAQUS numerical simulations were conducted on granite samples at 30 ℃, 40 ℃, 55 ℃, 75 ℃, and 100 ℃. The acoustic emission characteristics and Kaiser effect of the granite were studied, along with the changes in mechanical properties and damage failure characteristics under cyclic loading-unloading. The results indicate that: (1) Under cyclic loading-unloading, the peak strength of granite initially decreases and then increases as temperature rises, Notably the minimum peak strength and maximum area of the hysteresis loop are observed at 75 ℃. (2) Under different temperature conditions, the Felicity ratio of granite increases with the number of loading cycles and eventually converging towards a value of 1. However, the rate of increase gradually diminishes progressively, and the Kaiser effect becomes increasingly pronounced. (3) Further numerical simulation studies were conducted on granite at 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, and 100 ℃. The identification of Kaiser points through the analysis of fractured unit volume is consistent with the cumulative acoustic emission ringing count methodology, Furthermore, the Felicity ratio of granite exhibits a negative correlation with the extent of damage. (4) As the temperature and the number of cycles increase, the damage variable of granite initially increases before subsequently declining, with its maximum observed at 80 ℃. The results indicate potential risks of structural failure in high-temperature granite subjected to cyclic loading-unloading, thereby offering valuable insights for engineering construction.