Seismic responses of an underground tunnel in consideration of rock-tunnel interaction

Existing earthquake damage reconnaissance reports indicate that many tunnels have suffered noticeable damage. During seismic excitation, ignoring the rock-concrete interaction may affect the accuracy of research results. In this study, the influence of rock-concrete interaction on the response behavior of a tunnel under seismic excitation was systemically investigated. A finite difference method (FDM) model of the tunnel and the full dynamic time history calculation technique were conducted. The rock-tunnel interface was built by the FDM and the interface element was defined by a linear Coulomb shear-strength criterion. The reliability of the numerical simulation of the interface was verified by comparing the numerical and direct shear test results. Based on a real engineering case, the Xianglushan water conveyance tunnel, two models with different rock-tunnel interaction treatments were established, and their seismic response were discussed. In addition, the mechanical properties of the interface were comparatively discussed. The tunnel seismic response behaviors were discussed in terms of displacements, stresses and lining dynamic internal forces. The results indicate that the presence of the rock-concrete interaction may have a significant effect on the seismic response of the tunnel, and the influence has a certain pattern. Furthermore, the influences of the mechanical parameters of the interface upon the seismic response of tunnels are complex, and the stiffness of the interface plays a significant role.