Management of rockburst risks in deep underground engineering through controlled contour blasting

During the development of deep underground engineering projects, the surrounding rock is susceptible to significant deformation, rockburst, and other engineering disasters. The Jinping II Hydropower Station in China experienced several highly intense rockburst during the excavation of auxiliary tunnels and the drainage tunnel. To better understand the rockburst failure process and investigate possible mitigation solutions, the combined finite-discrete element method (FDEM) is adopted to model the development and evolution of the excavation damaged zone (EDZ) also associated to controlled contour blasting. To assess the mechanical effectiveness of this method, numerical simulation analyses employing the failure approaching index, energy release rate, and excess shear stress indices are conducted.  Results suggest that blasting-induced damage significantly influences the energy accumulation patterns in the surrounding rock. Changes in blasting design schemes lead to distinct evolution processes of surrounding rock damage, consequently affecting the energy release processes and the rockburst susceptibility. Recommendations for optimizing contour blasting parameters are also proposed to help reduce the risk of rockburst.