The Propagation Characteristics and Prediction of Vibration in Urban Soil–Rock Strata Induced by Underground Tunnel Blasting

This study addresses the need to carefully control vibration effects in the soil–rock strata during tunnel blasting in complex urban environments. Focusing on a typical underground tunnel blasting project, a combination of model testing and finite element simulations was used to investigate how blasting sources and site conditions affect vibration propagation in the soil–rock strata. A predictive model for blasting vibrations was developed using dimensional analysis. Findings show that vibration velocity attenuates more slowly in rock than in soil and that attenuation is even slower near the free surface (FS). High-frequency body waves are predominant near the soil–rock interface (SRI), while both high-frequency body waves and low-frequency Rayleigh waves occur near the FS. Close to the blasting source, vibrations at the SRI exhibit low attenuation, while significant amplification effects are observed near the FS. Tunnel blasting vibrations show directional characteristics, with vibration velocity attenuation at the interface negatively correlated with the blasting source burial depth, rock and soil wave impedance ratio, and SRI dip angle. Conversely, attenuation at the FS positively correlates with the blasting source burial depth, wave impedance ratio, and soil layer thickness. Additionally, increasing the blasting source burial depth and SRI dip angle enhances site vibration amplification. The proposed prediction model effectively predicts blasting vibrations in multi-layered soil–rock strata with high accuracy.