Deformations and damages of tunnels subjected to strike-slip faulting: Effects of tectonic stress and cross-sectional shape

Deep-buried tunnels are vulnerable to strike-slip faulting, the responses of which are complicated. However, the effects of tectonic stress and cross-sectional shape on behaviors of tunnels in strikeslip faults have not been detailly investigated. This study performs numerical modeling to study the deformations and damages of tunnels subjected to strike-slip faulting, focusing on the effects of tectonic stress and cross-sectional shape. A three-dimensional numerical model is applied, which is validated by the test from the previous study. Different lateral stress coefficients (from 0.5 to 3.0) and cross-sectional shapes of tunnels (circular shape, horseshoe shape, and egg shape) are modeled. The results show that tectonic stress and cross-sectional shape have a great influence on tunnel responses during strike-slip faulting. The failure mode of the tunnel is highly dependent on the tectonic stress. The tensile damage controls in low tectonic stress conditions, while compressive damage domains in high tectonic stress conditions. The tensile damage initials at the arch waist in the vicinities of fault planes, while the compressive damage mainly occurs at the tunnel vault and bottom in the whole fracture zone. Besides, tectonic stress has apparent effects on the transverse displacement of the tunnel axis and the compressive damage range. The Hshaped tunnel behaves the worst, experiencing the largest cross-sectional deformation, the largest compressive damage range, and the smallest required fault deformation for compressive damage.