Theoretical study of the vibration characteristic in geological layer under blasting excavation of metro tunnel

The stress waves generated by tunnel blasting in urban rock layers can affect the safety of adjacent buried structures in the overlying geological layers. To ensure the safety of buried structures, it is crucial to understand the blasting vibration characteristics in the geological layers. In this paper, the analytical solution for the vibration velocity response in geological layer subjected to P-wave is derived. Based on a specific tunnel blasting excavation project, the influence of incident wave frequency, layer thickness, and incidence angle on the vibration velocity distribution along the depth direction are investigated. Results show that the vibration velocity in the upper soil layer does not strictly attenuate with increasing distance from the blasting source but rather exhibits a fluctuating trend. As the frequency of the incident wave increases, the normalized vibration velocity on the ground surface exhibits a periodic decreasing trend, and the distance between the initial fluctuation point and the ground surface decreases. The normalized vibration velocity in the soil layer does not exhibit a monotonic decrease as the soil thickness increases. With an increase in the incident angle, a general declining pattern is observed in the normalized vibration velocity along the depth direction.