The　Mechanism　of　Compression-Shear　Damage　for　Rock Mass　with　Its　Application　to　Rockburst

This　paper　investigates　the　initiation　and　growth　criteria　for　compression-shear　crack　and　provides　theoretical　analysis　for　former　experience　compression-shear　fracture　criterion.　　On　the　basis　of　compression-shear　crack　model,　the　compression-shear　damage　model　for　rock　mass　is　proposed　with　crack　closing　effect　and　crack　interacting.　　From　the　proposed　model,　it　is　found　that　rockburst　results　from　macroscopic　brittle　fracture　of　rock　mass　due　to　frictional　sliding,　interface　propagating,　kinking,　and　linking　of　preexisting　cracks　in　rock　mass　activated　by　stress　redistributing　(tangetial　stress　concentrating　and　radial　stress relieving)　of　surrounding　rock　mass　during　(or　after)　excavating　of　underground　carven.　　Numerical　simulations　indicate　that　the　results　from　proposed　models　can　simulate　available　experimental　results　very　well　and　crack　closing　stress　has　a　significant　influence　on　the　stress-strain　relationship　of　rock　mass.　　It　is　shown　that　the　damage　strains,　especially　the　lateral　strain,　increase　with　the　raise　of　the　crack　closing　stress.