Seismic response and damage mechanism of lining structures for underground tunnels across fault

According to the dynamic interaction characteristics of lining and surrounding rock, a dynamic contact force method considering the discontinuous deformation between linings and surrounding rock is established. This method is used to calculate the antiseimic stability of an underground tunnel across fault in Lawa Hydropower Station project. Firstly, the influences of fault thickness and dip angle on the stress and displacement of tunnel linings under earthquake are investigated. Then, the influences of contact and fault on the seismic response and damage characteristics of the linings are investigated. The numerical results indicate that the existence of fault aggravates the seismic reaction of the linings, which shows that the stress and displacement of the linings at the fault are greater than those at other positions. The difference of fault thickness and dip angle has a significant influence on the seismic response of the linings at the fault. The seismic response of the linings increases with the decrease of the fault thickness, and the seismic response of the linings is the largest when the dip angle is 45°. The restraint effect of surrounding rock on the linings can effectively reduce their damage. The damage of linings at fault is more serious than that at other parts, and arch shoulders and arch abutments are the weak parts of the tunnel. Three typical damage patterns of the linings at fault are deduced from the simulated results and can be reasonably explicated by the corresponding damage mechanisms.