Deformation and failure mechanism of metro shield tunnel subjected to buried fault dislocation

Abstract

Numerous studies have shown that tunnels are vulnerable to damage due to fault dislocation. To investigate the deformation response and structural failure mechanism of the metro shield tunnel subjected to faulting, model tests with a geometric similarity ratio of 1:25 were carried out to analyze the influence of fault dislocation on the tunnel. The deformation of segmental lining and circumferential joints, earth pressure, and strain evolution were investigated. Combined with numerical simulations, the deformation and failure pattern of the shield tunnel after normal and reverse faulting were revealed. The failure criterion of segmental lining was discussed thoroughly. The results show that after faulting, the differential settlement, convergence deformation, strain response, and the soil pressure near the interface between the shield tunnel and the path line of fault increase remarkably. A horizontal duck egg-shaped deformation profile of segments is presented. The longitudinal cracks are distributed inside the tunnel vault and outside the tunnel haunch. The circumferential joint of shield tunnel is damaged severely under normal faulting, and the opening between segment rings exceeds the deformation limit of joint waterproofing. While tensile damage of the circumferential joint under reverse faulting is less evident, and the opening between segment rings is slight. The numerical simulation results have consistency with the consequence of the experiments. In addition, no circumferential crushing or oblique shear failure occurred in the model segment, and the deformation and tensile fracture damage of the circumferential joint should be deemed as the failure criterion of shield tunnels under faulting. Finally, countermeasures and suggestions are proposed for the structural design of metro shield tunnels overcrossing buried faults.