Experimental Study On The Rockburst Failure Process Of The Hard Rock Mass

Rockburst is due to underground excavation disturbance of rock mass stress concentration occurred, rock mass failure happens and elastic strain energy releases quickly, when the stress concentration exceeds the strength of the rock mass itself can bear, which lead to the phenomenon of mass ejection. Rockburst is a great destructive disaster in underground, which has a great influence on underground engineering stability, the safety of people and equipment. Uniaxial compression experiment and true triaxial compression experiment with one face free were conducted, high-speed cameras was used to record the whole test process. Thought analyzing the characteristics of failing process, energy evolution process, energy conversion and mechanism of rockburst, the following results were obtained:(1) Through the analysis of the failure phenomenon under uniaxial compression rockburst test and static brittle failure test, there are no sign before failure, rock ejection, lots of ejection block, few powder, high fragmentation are the characteristics of failure under uniaxial compression rockburst test, and the failure mode is tension-shear failure. By comparing the failure phenomenon between true triaxial rockburst test with one face and uniaxial compression rockburst test, there are obvious sign before failure, it keep capacity and leaves V-type pit after failure, few ejection block, lots of powder, low fragmentation were the characteristics of failure under true triaxial rockburst test with one face and uniaxial compression rockburst test, and the failure mode is tension-shear failure.(2) Though analyzing the energy evolution of unaxial compression rockburst test and truaxial compression rockburst test with one free face, the characteristic of energy evolution is deprived. The increasing rate of elastic energy is larger than energy dissipation in the compression stage, the increasing rate of elastic energy much larger than energy dissipation in elastic stage. In the crack-developing stage, the increasing rate of elastic energy is much larger than energy dissipation in the unaxial compression rockburst test, and the increasing rate of elastic energy is lower than energy dissipation in the truaxial compression rockbust test with one free face.(3) Through the analysis of the energy conversion characteristics of the uniaxial compression test and true triaxial compression test with one face free, we can draw the conclusion that the elastic energy conversion is much larger than the pre-peak dissipated energy and the post-peak dissipated energy.(4) This paper discusses the mechanism of rockburst based on the uniaxial compression test and true triaxial test with one face free, it was found that the elastic energy and dissipated energy has great influence on rockburst, the higher elastic energy conversion and the lower dissipated energy conversion are, the higher possibility of rockburst happens.