Damage evolution mechanisms of rock in deep tunnels induced by cut blasting

Abstract

The method of cut blasting is widely used in tunnelling excavation, which concerns the success in subsequent stop blasting and smooth blasting. Rock masses in deep tunnels are subjected to high in-situ stress, and the mechanisms of damage evolution of rock mass in deep tunnels induced by cut blasting are not well studied. In this paper, a tension and compression-shear damage model is developed, and then is implemented into the commercial software LS-DYNA as a user-defined material model. To validate the newly developed model, the comparison between numerical results and an existing field test is conducted. The effects of free-surface boundary conditions, in-situ stress and the coefficient of lateral pressure on cut blasting are considered in depth. Numerical results indicate that the superstition of stress wave and the reflected tension waves from free surfaces contribute to the damage interconnection near cut holes. The high in-situ stress has the resistance on the radially oriented pressure and the damage extension around cut holes. The coefficients of lateral pressure influence the extending direction of the tensile damage zone.