Effect of Circumferential Stress on Energy Evolution Mechanism of Rockburst under True Triaxial Unilateral Unloading Conditions

In order to study the influence of hoop stress on the energy evolution in the process of rockburst catastrophe, a new true triaxial rockburst test system was used to carry out the rockburst simulation test of single-side rapid unloading, three-five-side force and vertical continuous loading under different circumferential stresses. The rockburst failure modes of granite samples under different hoop stresses were analyzed. Combined with the principle of energy conservation, the evolution law of individual energy in the process of rockburst catastrophe was revealed. The results show that there is an obvious energy competition evolution mechanism between dissipated energy and elastic strain energy under different circumferential stresses. The circumferential stress will significantly affect the damage degree and distribution range of the rock sample. The unloading surface of the rock sample with a circumferential stress of 178.992 MPa has the deepest damage degree. Under the action of high circumferential stress, the elastic strain energy in the rock sample releases faster after the peak point, and the development of rockburst has short-term characteristics. The conversion rate of dissipated energy is proportional to the circumferential stress, and the conversion rate of elastic strain energy is inversely proportional to the circumferential stress. From the absolute value of energy, the increase of circumferential stress will obviously increase the accumulation of elastic strain energy and the release of dissipated energy. The total energy conversion rate of the rock sample is greater than the elastic energy conversion rate, which in turn exceeds the dissipated energy conversion rate. All three parameters exhibit positive correlations with circumferential stress. The increase of the circumferential stress will obviously accelerate the conversion rates of total energy, elastic energy and dissipated energy.