Continuum-discrete coupling model for mechanical response analysis of tunnels subjected to non-uniform reverse faulting

In recent decades, there have been numerous reports of damage cases involving tunnels crossing active faults. The mechanical response and failure mechanisms of cross-fault tunnels have become a key issue in the field of tunnel engineering. This study established a continuum-discrete coupling model comprising intact rock mass, fault zones, and tunnel. In this model, the tunnel and intact rock are modeled as continuous media, while the fault zone is modeled as a discrete medium. The non-uniform fault displacement is adopted to simulate the mechanical response and damage patterns of tunnels crossing active faults under reverse faulting. The simulation results are validated by comparison with the damage of Longchi tunnel observed from 2008 Wenchuan earthquake in China, as well as the experimental phenomenon from the model test. The results demonstrate that the proposed coupling model effectively reproduces the tunnel failure modes caused by reverse faulting. In addition, the high consistency between the simulation results and experimental data further confirms computational accuracy and reliability of the coupling model. A parametric analysis based on the Xianglushan tunnel in China is carried out to investigate the effects of fault displacements, fault widths, dip angles and fault zone rock mass qualities on damage patterns of crossing-fault tunnels. This study provides a valuable reference for seismic fortification of the tunnel crossing reverse faults.