Aiming at the formation mechanism of rockburst

the unloading rockburst mode were analyzed by rockburst examples and true triaxial loading and unloading test. The damage evolution equation of splitting failure and shearing failure of surrounding rock unloading rockburst were established. The results show that the fracture evolution of rockburst represent the composite destroying forms of splitting failure and shearing failure

just the difference depends on the size of the respective components；along with the increase of shearing components

blasting pit present the changes from flat bottom to arc so much as triangle or v shape; along with the increase of stress

surrounding rock has a quiet periods (no damage) and damage acceleration is obvious

once damage begin and rock with rockburst tendency has strong critical sensitivity; splitting failure always occurs preferentially; and the containing shearing composition becomes greater as the surrounding rock stress level after unloading becomes higher; and the rockburst intensity also becomes stronger.