Modeling study of cumulative damage effects and safety criterion of surrounding rock under multiple full-face blasting of a large cross-section tunnel

A blast-induced damage model integrating the tensile damage model with the Drucker-Prager yield condition is established. Based on the excavation of a large cross-section tunnel in China, the damage process of surrounding rock under multiple full-face blasting is simulated by the established rock damage model embedded into the LS-DYNA computer code through its user subroutines and a cumulative damage formulation in the LS-DYNA. The simulation results are well verified against field test data. The results show that the maximum damage depth of surrounding rock is determined by the blasting of the excavated cross-sections closest to the surrounding rock. Both the maximum damage depth and the maximum peak particle velocity (PPV) occur in the middle of the tunnel invert. Based on the defined damage threshold Dcr and the modeled maximum damage depth of surrounding rock, the influence of initiation sequence on the critical PPV for rock damage is studied, and a critical PPV associated with rock damage is proposed for tunnel blasting excavation.