Study on the influencing factors for segment dislocation during shield tunnelling

In order to analyze the influences of various factors during the construction period of a shield tunnel on the uplifting dislocation of segments, seven influencing factors are proposed according to the mechanical state, including outer diameter of the tunnel, ground condition, cover depth, coagulation time and density of synchronous grouts, shield tunneling speed and shield tail clearance. Numerical models for tunnel uplifting and segment dislocation are established to investigate the dislocation under different influencing factors. Then the variation laws of the segment dislocation are analyzed under the influences of various factors during the construction period. Moreover, the phenomenon and laws of the segment dislocation during shield tunnelling are verified through the test results of on-site monitoring. The main conclusions are as follows: (1) The segment dislocation will be intensified when the ground stiffness weakens, the density of synchronous grout increases, the coagulation time of synchronous grouts grows, the cover depth decreases, the tunneling speed increases, the shield tail clearance increases, and the grout stiffness after solidification decreases. (2) The increase of the tunnel diameter will lead to the increase of the segment uplifting, but has little correlation with the segment dislocation. (3) When the segment is uplifting, the contact friction between the segment rings and the bolt between the rings will play the role of shear resistance to control the dislocation. (4) Decreasing the uplifting force of the grouts, increasing the connection stiffness between the segments and the rings, strengthening the formation constraint and shortening the length of the fluid segment can reduce the segment uplifting dislocation during construction. (5) The proposed method to calculate the amount of dislocation can be used as a reference for the longitudinal waterproof design of segments.