Effect of Segment Thickness on Internal Force of Shield Tunnel under Abnormal Loading Conditions

Segment thickness is one of the important parameters of shield tunnel structure design. Segment thickness determines the section stiffness and mechanical performance of shield tunnel structure. Considering the load type of overload and unload, a three-dimensional fine shield tunnel numerical model was established. The full-scale test was used to verify the correctness of the numerical model. In the end, the effect of segment thickness on the internal force of shield tunnel structure under abnormal loading conditions was analyzed. The results show that the internal force of each section of the tunnel structure increases with the increase of the thickness of the segment, and the difference of the internal force between the different segment thickness increases with the increase of the overload and the degree of unloading. Increasing the thickness of segment will delay the breakpoint of the bending moment and axial force (critical instability state). The excessive increase of the segment thickness can lead to a large increase in the internal force of the tunnel structure, resulting in a decrease in the crack resistance of the tunnel structure.