Thermal-Force Coupled Unloading Failure Characterization in Granite with Different Fracture Inclinations

A large number of different inclinations of tectonic fracture exist for the Sichuan-Tibet Railway along the tunnel peripheral rock, and often in the high ground temperature and high stress coupling environment. In order to study the influence of fracture inclination on the unloading failure characteristics of hard rock under high temperature and high stress coupling, this paper analyzes the unloading rupture characteristics of granite specimens of a tunnel of Sichuan-Tibet Railway under 50℃ real-time temperature field through unloading test by adopting indoor test and numerical simulation method. The results show that: the unloading strength decreases with the increase of fracture inclination angle, when the fracture inclination angle is 0°, the unloading strength of the specimen under the 50℃ real-time temperature field is obviously smaller than the unloading strength at room temperature; the fracture specimen under the unloading condition has strong tensile damage characteristics, and the dilatancy phenomenon of the specimen under the 50℃ real-time temperature field is more obvious when the fracture inclination angle is 30°; When the fracture inclination angle is 0°, a penetrating fracture through the center of the pre-fracture is generated; under the real-time temperature field of 50℃, the larger the fracture inclination angle is, the more dispersed microcracks are developed in the unloading process of the specimen, and the smaller the inclination angle is of the pre-fracture, the earlier the accelerated point of fracture development occurs.