Experimental Study of Influence of Support Failures on Rockbursts under True-Triaxial Condition

Supports can effectively reinforce the surrounding rock after excavation in underground engineering. However, a support failure may cause an extremely intense rockburst. Hence, the influences of support failures, including support forces, support failure timings, and support failure rates, on rockbursts were systematically investigated in the present study. Unloading tests on rock specimens, using a true-triaxial rockburst test system, were performed to simulate rockbursts induced by support failure. The experimental results indicate that increasing support forces increased the prepeak accumulated elastic strain energy, the kinetic energy of the ejection fragment, and the ratio between the kinetic energy and release strain energy, whereas the damage to the rock specimens declined. During the testing process, the longer it took to unload the minimum stresses was, which means that the later the support failed, the greater the prepeak accumulated elastic strain energy was, the kinetic energies of the ejection fragments were, and the ratio of the kinetic energy and release strain energy was. Furthermore, as the support failure rate incremented, the kinetic energies of the ejection fragments of the rockbursts linearly increased, the failure mode of the rock changed from static failure to dynamic rockbursts, and the intensities of the rockbursts increased