Blasting effects of cross-fault deep-buried excavation on adjacent existing tunnel stability

The vibration caused by blasting excavation of rock mass frequently poses a threat to the stability of adjacent tunnels. Previous research is limited by the simplification of a rock mass as a homogeneous elastic medium, without considering the wave attenuation caused by viscoelasticity and wave separation induced by rock discontinuities, as well as plane waves while neglecting geometric attenuation of near-field nonplane blast waves. This paper establishes a theoretical model of cylindrical P-wave propagation across a fault to an adjacent existing tunnel. Based on the time-domain recursive method, vibration equations and peak particle velocity on the adjacent existing tunnel wall caused by a cylindrical wave passing through a fault are derived. The rock mass and fault are assumed to satisfy Kelvin viscoelastic bodies, and contact interfaces between fault and rock mass follow a nonlinear hyperbolic deformation model in the normal direction and a linear model in the tangential direction. The results show that tunnel vibration caused by the blast cylindrical P-wave is primarily induced by transmitted P-waves. With the increase of the fault dip angle, vibration on the upper side of the adjacent existing tunnel gradually decreases, while vibration on the lower side increases. The closer the vibration to the upper and lower sides, the stronger the shear effect on the tunnel wall, and the closer the vibration to the middle, the stronger the pressure effect on the tunnel wall. Larger fault thickness and higher initial blast wave frequency result in weaker vibration of the adjacent tunnel. The deeper the burial depth, the stronger the vibration of the adjacent tunnel wall. Findings of this study provide insight into the dynamic response of rock construction and safety evaluation in engineering service.