Earthquake damage investigations in recent years have revealed that fault zone is one of the most dangerous areas of tunnels in earthquakes, leading scholars to investigate the mechanisms of seismic response of fault-crossing tunnels and the aseismic measures. However, due to the complex fault-rock-tunnel interaction, the seismic response mechanism of tunnels crossing inactive faults is not yet complete and the suitability of different aseismic measure has not been evaluated. In this paper, a series of 3D numerical models of fault-crossing tunnels were established to study the seismic response of tunnels crossing inactive faults with different widths. On this basis, the suitability of grouting and flexible joints for fault-crossing tunnels were discussed. Due to the difference of physical property between the fault and the surrounding rock, the differential deformation will be produced at the interface, and resulting in a shear damage of the tunnel. The tunnel crossing wide fault is more vulnerable in earthquake than that crossing narrow fault. For the tunnel crossing inactive faults, especially those with wide widths, grouting reinforcement is a desirable aseismic measure. It can reduce the acceleration response of the tunnel within the fault and significantly reduce the tensile damage, while flexible joints have little effect on the acceleration response and the damage reduction of the tunnel within the fault. The present study can contribute to a better understanding of the seismic response of tunnels crossing inactive faults and provide some guidance to the seismic design.
Driven by the growing demand for infrastructure in mountainous areas, the construction of tunnels in highway and railway networks have been accelerated. Challenges and complex geological conditions are met with in tunnel projects than in the past. Numerous cases of damages of mountain tunnels have been reported in earthquakes[1–4], which have led scholars and engineers into topics researching seismic response and seismic design of tunnels and other underground facilities.
Earthquake damage investigations on mountain tunnels reveal that fault or fracture zone is one of the most dangerous areas of tunnels in earthquake [5–7]. In order to study the seismic response and earthquake damage mechanism of fault-crossing tunnels, scholars have carried out numerous researches including scaled model tests[8–10] and numerical simulations[11–13]. Recent evidence suggests that the tunnel will be severely damaged by the violent shearing action when the fault dislocated[14,15]. Meanwhile, if the fault is not dislocated, the discontinuity of the strata will cause the tunnel to deform unevenly in the longitudinal direction[16], and the fault interface will reflect and refract the incident seismic waves, causing increased tunnel deformation[17,18]. However, due to the complex fault-rock-tunnel interaction, the seismic response mechanism of tunnels crossing inactive faults is not yet complete, leading to a gap between research and engineering practice.
