Subway tunnels with rectangular cross-sections in soil layers are susceptible to damage from fault dislocations, particularly when multiple faults are involved. The interaction between tunnel structures and multiple fault displacements can lead to significant stress and cumulative damage. The focus of this study is to investigate the mechanical behavior of a rectangular subway tunnel under the influence of multiple normal fault dislocations using validated numerical simulations. By analyzing the cumulative damage effects and the impact range from these fault displacements, the study proposes defense strategies and mitigation measures to enhance tunnel safety. The results show that tension damage occurs at the tunnel crown in the footwall and the invert in the hanging wall, and tension-bending-shear damage was observed at the tunnel sidewalls at the fault. Compared to horseshoe-shaped tunnels, rectangular tunnels exhibit a more uneven stress distribution across section, with tensile stress up to 5 times higher. Simultaneous displacements of multiple faults result in high tensile stress, especially at the crown and invert, while sequential fault dislocations cause progressive damage in these areas, shifting the stress to the sidewalls with a 50% reduction. The cumulative plastic strain from sequential displacements is three times greater than that from simultaneous displacements. In areas with closely spaced faults, overlapping damage zones can occur. To mitigate these effects, anti-fault measures such as deformation joints and enlarged tunnel cross-sections are recommended, along with enhanced waterproofing solutions, including waterstop strips and embedded grouting pipes. These findings offer valuable insights into ensuring the safety of tunnels in fault-prone regions and provide practical strategies for mitigating fault-induced damage.
