Unloading confining pressure for brittle rock and mechanism of rock burst

Rock burst is often met in excavation unloading of underground engineering in high geo-stress areas. According to the actual stress state on surrounding rock, conventional triaxial and unloading confining stress laboratory tests are conducted for brittle rock during pre-peak strength and post-peak strength. The full-regime of the rock failure is analyzed and the characteristics of acoustic emission in the process of rock failure are studied. The rock deformation-failure characteristics and the mechanical mechanism of the rock burst are discussed. The test results show that the rock samples all exhibit brittle failures in pre-peak and post-peak unloading confining tests and the brittle characteristics in the pre-peak tests are stronger than those in the post-peak tests. The brittle failures of rock are more intensive with high unloading rate, and the probability of rock burst is larger. The characteristics of the rock burst are summarized. These results are helpful to the researches on the mechanical mechanism of rock burst.