A multi-scale coupled method for nonlinear dynamic response analysis of mountain tunnels subjected to fault movement

• Multi-scale coupled method is proposed for analysis of near-fault tunnel. • The full-process seismic response of mountain tunnel is efficiently simulated. • The coupled mechanism of fault and mountain on tunnel damage has been revealed. This paper introduces a novel two-step multi-scale coupled method for simulating the nonlinear dynamic behavior of a mountain tunnel subjected to fault movement. In the first step, the broadband seismic responses within a large-scale mountain-fault model can be accurately solved by the indirect boundary element method, converting them into effective input forces around the specified region of interest within the mountain. The second step involves finely simulating the nonlinear dynamic response of the tunnel cross-section in the designated region using the finite element method, with the implementation of a viscoelastic artificial boundary to absorb the reflection of scattered waves at truncated boundaries. Two verification processes are employed to validate the accuracy of the multi-scale coupled method. Furthermore, we illustrate the applicability and efficacy of the new method with an example involving the elastoplastic dynamic analysis of a mountain tunnel under the influence of normal fault movement. The presented example highlights the impact of fault motion parameters, including fault dislocation value and dip angle, on the responses of the mountain tunnel. The results demonstrate that the proposed multi-scale coupled method can achieve full-process seismic simulation, ranging from kilometer-scale fault rupture to centimeter-scale mountain tunnel section damage, with a considerably reduced computational expense.