Bending stiffness of segment joint and its effects on segment internal force for underwater shield tunnel with large cross-section

Taking Shiziyang tunnel which is an underwater railway shield tunnel with large cross-section as the research object, the bending stiffness of the circumferential segment joint was studied using the finite element numerical analysis method combined with prototype bending test of segment joint. Then beam-spring model was applied to analyze the effects of joint bending stiffness on the internal force of the whole segment. Results show that the value range of joint bending stiffness is from 50 to 700 MN·m·rad-1. Under the same axial force, the joint bending stiffness will reduce an order of magnitude with the increase of joint bending moment. Under the same joint bending moment, the joint bending stiffness will increase with the increase of axial force. The joint bending stiffness has a weak influence on the axial force distribution of the segment, and has a significant influence on segment bending moment. The bending moment distribution of the whole segment tends to be uniform as the joint bending stiffness increases. In the range of bending stiffness, the maximum difference of the moment extremum reaches about 80%, the maximum reduction of the axial force extremum is about 5%, and the maximum reduction of the deformation is about 20%. The improved beam-spring model considering the nonlinear relationship between joint bending stiffness and moment, axial force can better reflect the influence of the joint on the whole segment structure mechanics. It is more suitable for the calculation of the segment internal force for large cross-section shield tunnel.