Objective For the tunnel construction of large-span metro stations in hard rock, it is necessary to investigate the applicability and vibration effect characteristics of micro-vibration blasting method in order to improve the conventional blasting technique.

Method Based on the underground project of Xietaizi Station on Chongqing Metro Line 18, a three-dimensional tunnel numerical model is established with finite difference software to simulate the blasting excavation process. An optimized micro-vibration blasting method is proposed, the monitoring points are arranged on the ground above the blasting area, and the vibration velocity and vibration frequency at ground measuring points are monitored and measured. Thus, the blasting vibration monitoring data are obtained and then compared with numerical simulation results for verification.

Result & Conclusion The optimized micro-vibration blasting method can reduce the number of blast holes, the single blasting charge mass and charge concentration, and block partial propagation pathways of blasting stress into the surrounding rock, thereby effectively mitigating the blasting vibration. Compared with the original blasting method, the optimized method reduces the vibration velocity at ground measuring points by more than 70% under the same excavation advance. This optimized method presents favorable adaptability for blasting excavation of large-span metro station tunnels in hard rock for urban environments.