Optimization for Longitudinal Segment Joint of Metro Shield Tunnel with Straight Joint in Soft Soil Area

The longitudinal segment joint of metro shield tunnel in soft soil area is prone to damage because of the overloading of ground surface. Considering the characteristics of soft soil stratum, the longitudinal segment joint is optimized by the proposed concept of “rigid lining” in the design for the transverse rigidity of shield tunnel in soft soil area, which increases the rigidity and strength of tunnel structure. The flexural rigidity of longitudinal segment joint can be increased by increasing segment thickness locally or integrally, thus the deformation of segment ring is obviously reduced. Although the bending moment of segment ring is generally increased, the decrease amplitude for segment ring deformation is much larger than that for its bending moment. The positions of the connecting bolts between externally or internally open longitudinal joints are designed respectively, and the connecting bolt should be close to the open side of the joint. When the segment ring is divided into blocks, the longitudinal segment joint should be designed at the position of smaller bending moment as possible. At the same time, in order to meet construction conditions, the block number of segment ring should be decreased. The edges and corners of longitudinal segment joint are partly strengthened so as to prevent them from being damaged. The waterproof capability of the longitudinal segment joint of metro shield tunnel can be strengthened through reasonably designing the position and cross section form of waterproof gasket. © 2017, Editorial Department of China Railway Science. All right reserved.