Blasting Network Optimization and Application for Urban Subway Drift in Complex Environments

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.