Propagation characteristics and prediction of blast-induced vibration on closely spaced rock tunnels

•Analysis for blasting vibration propagation on closely spaced rock tunnels.•PPV on closely spaced rock tunnels is predicted by empirical equations.•Diffraction based equations are proposed to predict PPV on tunnels. Excessive blast-induced vibration may cause damage and even the collapse of underground tunnels, and the monitoring and prediction of vibration have an important reference role for the control of these disasters. In this paper, the propagation characteristics and attenuation prediction equation of blast-induced vibration on closely spaced rock tunnels were discussed based on field monitoring and numerical simulation. First, the propagation and attenuation characteristics of blast-induced vibration (e.g. particle peak velocity, PPV) on rock tunnels were analyzed and the applicability of some commonly used empirical equations to predict the PPV on lower bench and sidewall of closely spaced adjacent tunnel was discussed and compared. Then, considering the diffraction characteristics of the wave around tunnels, the scaled distance (SD) of the empirical equations was improved to predict the PPV on the whole space of the rock tunnels. Finally, a new equation was proposed to predict the PPV on adjacent tunnel section in the blasting centre plane considering the diffraction and reflection amplification effects of blast-induced vibration around adjacent tunnel. The research results show that the vibration velocities of surrounding rock around the tunnels are different from those in the free field surrounding rock without the influence of tunnel cavities due to the reflection and diffraction of blasting vibration on the tunnel wall. The improved and proposed empirical equations (5) and (6) are more accurate in predicting the PPV on the closely spaced rock tunnels because the diffraction and reflection amplification effects of blast-induced vibration around tunnels are considered.