Propagation Law of Blast-induced Vibrations during Metro Tunnel Under-passing Existing Old Buildings

Abstract

Objective There is limited research both in China and abroad on the blasting construction of metro tunnels under-crossing existing old buildings. Projects utilizing blasting excavation may pose safety concerns for nearby structures. It is crucial to understand the propagation law of blast-induced vibrations and analyze their impact on surrounding buildings. Method Taking the blasting construction of Nanping Sta.-Nanbin Road Sta. interval on Chongqing Rail Transit Line 10 phase II project as study case, the blast-induced vibrations are monitored during tunnel blasting excavation process. The observed data are obtained using sensors for blast-induced vibration, and regression analysis is performed on the actual blast-induced vibration monitoring data using the Sadowski′s formula, thus the propagation attenuation law of blast-induced vibrations is obtained, the influence of factors such as vibration velocity, maximum charge per delay, and blasthole distance on blast-induced vibrations is discussed. Result & Conclusion In the regression fitting results of blast-induced vibration velocity with blasthole distance and charge per delay in three vibration measurement directions, the correlation coefficients between calculated data and monitored data are all greater than 0.800. The increase in the maximum charge per delay is relatively small when the blasthole distance increases from 0 to 40 m. However, the increase in the maximum charge per delay becomes more significant when the blasthole distance ranges from 40 to 80 m. The variation amplitude is most significant in the direction perpendicular to tunnel bottom plate. Attention should be focused on the maximum allowable charge per delay value when the blast-induced vibration safety control velocity is set at 1.0 cm/s.

Keywords

• metro tunnel
• blast-induced vibration
• propagation law
• existing old building
• regression analysis