Experimental study on unloading creep of deep granite at 50℃

To study the unloading creep characteristics of deep granite at high temperature, the unloading creep tests of granite were carried out under the confining pressure of 10, 20, 30 MPa at 50℃ by using the rock automatic triaxial rheometer. The unloading creep characteristics, the macroscopic failure modes and the microscopic failure mechanism of granite at high temperature were studied. The experimental results show that the granite produces large creep deformation under high pressure unloading by the effect of the temperature. The creep performance of granite changes exponentially with the unloading at the temperature of 50℃. The higher the initial unloading confining pressure is, the earlier the creep deformation of granite appears. The main unloading creep failure mode of granite is shear failure at 50℃. The creep effect promotes the propagation of internal damage cracks and fracture surfaces are formed, thus leading to failure. The failure strength of unloading creep at high temperature is about 1/3 of that of the triaxial strength. Compared with the traditional indicators, the cohesion and the internal friction angle reduce more than 30%. © 2020, Editorial Department of Journal of Southeast University. All right reserved.