Influence of ground fissures on metro shield tunnels: Large-scale experiment and numerical analysis

The recent upsurge in metro construction emphasizes the necessity of understanding the mechanical performance of metro shield tunnel subjected to the influence of ground fissures. In this study, a large-scale experiment, in combination with numerical simulation, was conducted to investigate the influence of ground fissures on a metro shield tunnel. The results indicate that the lining contact pressure at the vault increases in the hanging wall while decreases in the footwall, resulting in a two-dimensional stress state of vertical shear and axial tension-compression, and simultaneous vertical dislocation and axial tilt for the segments around the ground fissure. In addition, the damage to curved bolts includes tensile yield, flexural yield, and shear twist, leading to obvious concrete lining damage, particularly at the vault, arch bottom, and hance, indicating that the joints in these positions are weak areas. The shield tunnel orthogonal to the ground fissure ultimately experiences shear failure, suggesting that the maximum actual dislocation of ground fissure that the structure can withstand is approximately 20 cm, and five segment rings in the hanging wall and six segment rings in the footwall also need to be reinforced. This study could provide a reference for metro design in ground fissure sites.