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.

The Jiangshuiquan Road Station tunnel construction along Jinan Metro Line 4 is located in a highly urbanized area with building proximity constraints, featuring a critical minimum clearance of 3.58 m between the underground excavation zone and adjacent pier foundations. This study consequently established a controlled test section within the subway tunnel project, characterized by lower blasting risk potential, to conduct systematic comparative analyses of three distinct blast initiation network configurations: S-patterned, co-directional, and bilateral-oriented vaults. Under controlled blasting conditions with 50 ms inter-row and 5ms inter-hole, comprehensive monitoring of pavement vibration velocities and waveform characteristics was carried out to evaluate vibration differentials across distinct initiation networks systematically. Concurrent quantitative analysis of rock fragmentation effects revealed that, while maintaining identical blasting parameters, the S-patterned detonation network generated the highest peak particle velocity of 0.87 cm/s, followed by co-directional detonation (0.55 cm/s), with the lowest on both sides (0.41 cm/s). Comparative analysis reveals that co-directional detonation achieves a 37% reduction in peak vibration velocity compared to S-patterned detonation. In comparison, the bilateral crown-oriented detonation demonstrates optimal vibration attenuation, achieving approximately 52% peak reduction. Post-blast fragmentation analysis further indicates that the bilateral-to-center detonation method yields the lowest oversized fragment rate (< 25%) and concurrently the highest fine particle proportion, thereby exhibiting superior overall fragmentation quality. Finally, the bilateral crown-oriented detonation network was implemented in the highest-risk blasting zone adjacent to pier foundations to validate these findings. This study establishes a methodological framework for optimizing initiation networks and controlling blast-induced vibrations in urban subway tunnel construction within a complex environment.

In order to study the gas diffusion-transport law and the influence of ventilation on the gas concentration of high gas tunnel after blasting, an optimization blasting scheme under gas conditions was carried out, and a gas diffusion-transport characteristic near the working face was investigated under both ventilated and unventilated conditions in a project. The study shows that the residual rate of the blast hole and the utilization rate of the blast hole are above 90%, and the over-excavation control effect is better with an expected blasting footage of 1.2 m and an uncoupling coefficient of 0.76. Under the condition of unventilated condition by numerical simulation, the gas accumulation near the arch top and the arch waist at the tunnel's working face is severe as the gas concentration is close to 30%. Meanwhile, the gas concentration is higher in the area 7 m away from the working surface, and the gas concentration gradient is smaller in the area beyond 7 m after the gas state is stabilized. The gas concentration can be reduced to the safe range around 30 days after ventilation. However, gas accumulation quickly occurs at the arch foot and the arch waist on the other side of the air duct, especially the gas accumulation at the arch foot is more prominent, and the gas concentration is close to 20%. There is a ventilation blind area at the arch foot of the same side of the air duct, and the gas accumulates in a small range as the concentration is about 5%. The monitoring and prevention of the above areas should be strengthened. The field measured gas concentration distribution and gas influence range are consistent with the simulation results, and the research results can provide a reference for similar gas tunnel blasting construction and ventilation optimization.