Seismic responses of an underground tunnel considering rock–tunnel interaction

Abstract

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 of a tunnel under seismic excitation was systemically investigated. A finite-difference method (FDM) model of the tunnel was constructed and full dynamic time history calculations were performed. The rock–tunnel interface was built using the FDM, with interface elements defined by a linear Coulomb shear strength criterion. The reliability of the numerical simulation of the interface was verified by comparisons with direct shear test results. Based on a real engineering case (Xianglushan water conveyance tunnel), two models with different rock–tunnel interactions were established and their seismic responses evaluated. The mechanical properties of the interface were compared. The seismic responses of the tunnel were assessed in terms of displacements, stresses and lining dynamic internal forces. The results indicated that rock–concrete interaction may have a significant effect on a tunnel's seismic response, and that effect has a certain pattern. The influences of the mechanical parameters of the interface on the seismic response of tunnels are complex and the stiffness of the interface plays a significant role.