Optimization of Delay Time of Cutting Hole in High Gas Tunnel based on SPH-FEM Coupled Simulation

Current initiation delay settings in high-gas tunnels typically follow fixed intervals (0 ms, 25 ms, 50 ms, 75 ms, and 100 ms), yet the limited number of delay segments (fewer than the blast hole rows) forces auxiliary holes to share delays. This configuration, combined with inadequate cut-hole delay durations, significantly compromises optimal blasting outcomes. To address this issue, a field-programmable digital electronic detonator was implemented. Theoretical analysis determined the complete rock mass fracturing duration in the cutting area to be 40 ms, which was further validated through numerical simulation of rock mass displacement dynamics, establishing this as the optimal delay interval. The study reveals that rock mass displacement in the cutting area progresses through three distinct phases: fracture propagation, volumetric expansion, and rock material ejection. Based on the optimal cutting area delay time, the ideal initiation sequence for blast hole rows was established as 0 ms, 40 ms, 60 ms, 80 ms, 100 ms, and 120 ms, with subsequent field validation conducted in a high-altitude gas tunnel. Statistical analysis of blasting performance demonstrates that implementing the optimized delay sequence (0 ms, 40 ms, 60 ms, 80 ms, 100 ms, and 120 ms) achieves over 90% half-hole preservation and controls linear overbreak within 20 cm, satisfying construction specifications while validating the delay configuration′s efficacy, with direct applicability to analogous tunnel blasting operations.