Spallation damage of underground openings caused by excavation disturbance of adjacent tunnels

Abstract

Spallation damage in underground mines and tunnels is a common phenomenon, especially during blasting excavations, and revealing the mechanism of spallation damage is an urgent issue for the stability of underground tunnel. In this study, the circumferential and radial stress distributions around the circular tunnel under a transient cylindrical P-wave were examined by combining wave function expansion method and Duhamel’s integral technique. Theoretical results revealed that the spallation damage around the tunnel was mainly caused by high radial dynamic stress concentrations face to a short-wavelength incident waves, and the circumferential and radial stresses around the tunnel decrease as the clearance increases. Furthermore, in order to reappear the spallation damage around the tunnel under blast load and obtain the effect of initial stress and bolt support, the CSCM material model was used to simulate the damage of surrounding rock by LS-DYNA. The numerical simulation results indicated that the initial stress reduced the radial cracks, while the presence of the initial stress exacerbated the spallation damage on the incident side. Finally, the stresses in each time stage of the circular tunnel surrounding rock under the action of transient cylindrical P-waves were analysed.