Deformation Analysis of Nuclear Power Shield Tunnel by Longitudinal Response Displacement Method Considering Fluid–Solid Coupling

The joint of a shield tunnel segment is the weak part of tunnel, and the opening amount of the joint seriously affects the watertightness of the internal structure of the tunnel. In this experiment, a model was created with ANSYS, the fluid–solid coupling effect of the seawater and seabed was considered using the SuperFLUSH/2D 6.0 software, and the local site effect was considered by free-field seismic response analysis. Considering the structure and stress characteristics of the shield tunnel in conjunction with the marine area, earthquake research on shield tunnel culverts was conducted using lateral and longitudinal beam–spring models. The main focus of this article is to study the earthquake resistance of shield tunnel joints under extreme seismic excitation (SL-2) in complex marine environments. The results indicated that in the lateral analysis, under varying soil layer conditions, the diameter deformation rates for sections 1 and 2 using high-strength bolts were 1.752% and 1.334%, respectively, while the joint-opening amounts were 0.515 mm and 0.387 mm, respectively. This suggests that locations with thicker silt layers exhibit larger joint-opening amounts and are more susceptible to deformation. In the longitudinal analysis, when bolt strength varied, the maximum joint-opening ranged from 4.706 mm to 6.507 mm, and the maximum dislocation ranged from 0.625 mm to 1.326 mm. The deformation rule of the joint bolts followed the pattern that higher stiffness led to smaller deformation, whereas poorer geological conditions resulted in larger deformation. Therefore, the interface between soft and hard strata is a weak point in the longitudinal seismic resistance of the shield tunnel structure. The conclusions of this study can supplement the seismic research on shield tunnels in the marine areas of nuclear power plants.