The fault dislocation produces severe additional deformation on cross-fault tunnels along the axial direction, seriously threatens tunnel safety. To this end, a simplified analytical model for evaluating the mechanical behavior of segmental tunnels subjected to buried fault dislocation was established. The segmental tunnel is treated as a Timoshenko beam acting on the Vlasov elastic foundation. The plastic yield of circumferential joints, the effect of frictional resistance along the axial direction, and the deformation characteristics of overburden soil after faulting were considered. Then, the reasonability of the analytical solution is proved by 3D numerical simulation. The tunnel safety state was evaluated based on the joint deformation of the segmental tunnel. Subsequently, the effects of plastic yield behavior between segmental rings, plastic equivalent bending stiffness ratio, segment dimensions, and longitudinal bolt on the longitudinal response of the segmental tunnel linings were investigated. The results show that the simplified analytical solution proposed is reasonable in predicting the joint deformation between segmental rings when the segmental tunnel is subjected to buried fault dislocation. When the normal faulting is imposed, the segmental tunnel is dominated by tensile deformation along the tunnel axial. Under 20 cm of normal faulting, the joint opening between segmental rings is close to the deformation control value of joint waterproofing. However, the shear deformation has been significantly weakened due to the effect of faulting in the propagation process to the surface. The calculation result is too small when the plastic deformation behavior is ignored. The plastic equivalent bending stiffness ratio eta 2 inversely correlated with the maximum joint opening. Increasing the strength grade or the number of longitudinal bolts has a relatively limited effect on reducing the opening between segment rings, where the joint still has a greater risk of water leakage.

This paper presents an improved longitudinal beam-spring model on the Vlasov foundation for estimating the longitudinal deformation of the shield tunnel when subjected to the ground surface surcharge. This model incorporates an improved subgrade modulus and treats each segmental ring as a Timoshenko short beam, with each circumferential joint modeled by two mechanical springs. It can accurately reflect the discontinuous deformation, and capture the dislocation and opening deformation of shield tunnels. Two-stage analysis methodology is adopted to consider soil and tunnel interaction. The feasibility of this model is verified by comparing it with two well-documented field monitoring cases. The computed results are also compared with those based on other analytical models. The results show that the Timoshenko continuous beam overestimates the dislocation deformation, while underestimates the opening deformation. In addition, the settlement curve exhibits neither smooth nor differentiable features. Finally, this paper also conducted some parameter analysis to examine the impact on tunnel deformation, encompassing dimensions of ground surface surcharge, the dual-area loading, and the joint reinforcement. This approach provides valuable insights into how the deformation characteristics of shield tunnels are influenced by ground surface surcharge.