Analysis of dynamic stress intensity factor of rock mass under excavation unloading in underground caverns

Based on linear elastic assumption and ANSYS software, taking the excavation of underground powerhouse of Longtan Project for example, the dynamic stress intensity factor under blasting load and unloading of initial stress is calculated. The results show that the crack propagation and rock mass damage near borehole are due to blasting load in the process of fragmentizing rock by blasting in medium high ground stress region. But the dynamic unloading of initial stress is the key factor which induces the loose of reserved rock in medium long region and the propagation of original crack.