Numerical Studies on the Cumulative Damage Effects and Safety Criterion of a Large Cross-section Tunnel Induced by Single and Multiple Full-Scale Blasting.

The cumulative damage effects of surrounding rock under single full-face blasting and multiple full-face blasting of a large cross-section tunnel are comparatively studied in this paper. The damage processes of the single and multiple full-face blasting of the tunnel are simulated by the established rock damage model embedded into the LS-DYNA computer code through its user subroutines and a cumulative damage simulation technology in the LS-DYNA. The simulation results are verified against field test data. The results demonstrate that the numerically predicted peak particle velocity (PPV) of the surrounding rock under multiple full-face blasting is more consistent with field test data than that under single full-face blasting, which indicates the advantages of multiple full-face blasting in comparison to single full-face blasting in simulating the blasting process of a tunnel. The maximum damage depth in the middle of the tunnel invert is mostly affected by multiple full-face blasting. Both the maximum damage depth and the maximum PPV occur in the middle of the tunnel invert under single and multiple full-face blasting. Based on the defined damage threshold Dcr and the modeled maximum damage depth of the surrounding rock, the influence of initiation sequence on the critical PPV for rock damage is analyzed, and a critical PPV of rock damage is proposed to provide a safety criterion for tunnel blasting excavation. [ABSTRACT FROM AUTHOR]