Abstract: A series of experimental tests were conducted on grey medium grained granite to investigate the influence of failure support forces, support failure timing and support failure rates on rockburst ejection using the self-developed true-triaxial rockburst test system. The difference of stress paths before and after the support failure of an underground cavern was simulated. The whole rockburst processes were tracked and the ejection kinetic energy was estimated by the high-speed camera system. The results indicate that the greater the support force, the larger ejection kinetic energy once the support fails. With the increase of axial stress, the later the time of removing the minimum principal stress on a single side is (i.e., the later the time of support failure is), the greater the kinetic energy of rockburst ejection is. With the increase of support failure rate, the kinetic energy of rockburst ejection increases, and the failure mode of rock specimen changes from static brittle failure to dynamic rockburst failure.

Key words: rock mechanics, rockburst, true triaxial, support