Unloading rheological tests of hard brittle rock and its long-term strength analysis

In order to further understand the rheological mechanics behavior of hard brittle rock under the condition of unloading, a unloading rheological test was made on the hard brittle granite by using rock automatic triaxial servo rheometer to investigate its creep laws and creep properties. Also, the method of determining the long-term strength of hard brittle rock was analyzed according to the test results. The results show that the rheological behavior of hard brittle rock under unloading path is different from that of loading path, and the lateral creep behavior is more likely to happen than the axial creep behavior; the higher the deviatoric stress level, the greater the steady-state creep rate, and they show the relationship of exponential function; the rock enters the stage of accelerated creep when its stress level exceeds the rheological threshold, and fails rapidly with its ductile dilatancy. According to the experimental results, the long-term strength of rock creep should be determined by the point of intersection of creep rate in both axial and lateral at the steady-state creep stage. The long-term strength determined by the method can increase the reliability by 10% than that using the traditional methods. © 2015, China Coal Society. All right reserved.