Effect of Excavation Blasting in Underground Water-Sealed Gas Storage Cavern Under In-Situ Stress

When underground caverns are created in deep rock masses by drilling and blasting methods, an undesirable excavation damage zone is induced. However, previous studies on effects of initial in situ stress field on blast-induced damage and safety criterion are few worldwide. In this study, we calculated and analyzed the dynamic response of surrounding rock during blasting excavation by the finite element software ANSYS/LS-DYNA based on field blasting tests of excavation blasting for underground gas storage caverns in Yantai, Shandong province, PR China. The numerical results indicated that tensile failure tended to occur in the middle of the curved wall. Meanwhile, the distribution and the range of surrounding rock damage under coupled static-dynamic load were obviously different with those under dynamic load alone, which showed that the influence of in situ stress on rock blast-induced damage could not be ignored. The relationship of the maximum tensile stress and peak particle velocity in the middle of the curved under in situ stress was analyzed and modeled. According to the maximum tensile strength theory and numerical calculation results, the critical vibration velocity was determined for controlling the rock damage of underground cavern, and the effects of the in situ stress on the safety criterion for rock damage were discussed.