Numerical Analysis Research on Tunnel Damage Under the Action of Oblique Slip Faults Based on Multiple Slip Surfaces

In the field of tunnel engineering, it is often difficult to avoid crossing active faults. During an earthquake, tunnels across faults are highly vulnerable to damage. Therefore, conducting research on their mechanical responses and failure mechanisms is of great significance. This paper takes Xianglushan Tunnel as a research example and uses finite element software to carry out numerical simulation of the tunnel under the action of the left-lateral normal fault activity. Moreover, the effectiveness of this model is verified using the actual measurement data of the damaged tunnels during the Kumamoto earthquake. By comparing the damage conditions and stress states of the tunnel under the action of left-lateral normal faults and strike-slip faults, and conducting a systematic and refined study on relevant fault parameters, the following research results are obtained: First, compared with oblique-slip faults, strike-slip faults cause more severe damage to the tunnel; second, tunnel damage is mainly concentrated in the area where the fault slip surface is located; third, an increase in fault displacement can significantly exacerbate structural damage and is the main factor leading to tunnel failure; fourth, the dip angle of the fault affects the stress distribution of the tunnel. As the dip angle increases, the damaged area gradually shrinks; fifth, the change in the width of the fault fracture zone will alter the failure mode of the tunnel. Reasonably choosing to cross a wider fault can reduce the structural damage. This research provides theoretical support and practical reference for the seismic design of tunnels across faults.