Numerical Analysis on the Effect of Geometric Parameters of Reverse Fault on Tunnel Mechanical Response

Permanent displacements caused by active faults can lead to the severe deformation of tunnel liners. To investigate the effect of fault fracture deformation patterns on the deformation of tunnel liners under fault dislocation, this paper categorized three fault-zone fracture deformation patterns and conducted numerical simulations for tunnel’s surrounding rock-liner systems under different fracture deformation patterns. Furthermore, the longitudinal displacement, relative deformation, axial stress, and shear stress of the tunnel liner were measured to characterize the mechanical response of the tunnel, and the effects of fault geometric parameters on the mechanical response of the tunnel liner were explored. The results showed that fracture deformation patterns were broadly categorized into uniform fracture deformation, linear fracture deformation, and nonlinear fracture deformation patterns. The distribution patterns of tunnel liner stress and deformation under these fracture deformation patterns were similar, but the magnitude of the peaks and the intensity of their effects differed. Under reverse fault dislocation, the peak values of tunnel liner deformation and shear stress occurred at the rupture plane. In contrast, the maximum axial stress was observed at the interface between soft and hard rock masses. When the core width of the fault zone decreased and the fault dip direction increased, the intensity of the mechanical response of the tunnel liner increased. With the fault dip decreased, the axial stress in the tunnel liner transitions from tensile-compressive stress to compressive stress, the shear stress decreases, and the intensity of the relative deformation of the tunnel liner increases. These research results can provide significant guidelines for tunnel design crossing the reverse fault.