Structural damage assessment and failure mode analysis for cross-fault submarine tunnels

Abstract

Fault fracture zones represent unfavorable geological conditions that are often encountered in cross-sea tunnels. When such a tunnel crosses a fault, the sliding action of the fault easily results in significant tensile, compressive, and shear failure of the lining, thereby causing local buckling and even fractures. Therefore, in this study, a series of sophisticated 3D discontinuous contact numerical models were established; these models account for the underground rock stratum, hydrostatic pressure, and nonlinear behavior of materials. The developed models realistically reproduced the construction process for earth pressure balance shield tunnels, such as the jack force, grouting pressure, and grout hardening over time. The simulation results suggest that the relative spatial location and morphology of the fault fracture zone strongly influence the failure mode of the tunnel. The tunnel structure exhibits three typical failure modes: face bulge, local sliding failure, and overall sliding collapse. The dip angle and crossing angle of the fault will lead to the readjustment of shear forces and bending moments in the tunnel, leading to uneven displacement and localized torsional deformation of the adjacent lining. Additionally, increasing the ratio of diameter to thickness will decrease the overall rigidity and torsional resistance of the tunnel.