Simulation method for gas tightness of segment joints of shield tunnels and analysis of influencing factors

When a shield tunnel passes through a gas-bearing stratum, the disturbance of construction to the stratum is easy to cause gas leakage, and gas tends to enter the tunnel through the joint of shield tube, which is easy to cause explosion and other disasters. Based on the Sutong GIL integrated pipe gallery project which crosses the high-pressure gas-bearing strata in the Yangtze River, the main factors affecting gas leakage on the joint surface of shield tunneling tube are studied, and the corresponding improvement measures are proposed. The whole process of the gas leakage in the joint surface under pressure loading is analyzed through the joint model tests, and the main factors affecting the gas tightness of the joint surface at different stages of gas leakage are revealed. A numerical simulation model for joints is established to study the effects of the opening of the joint surface and the roughness of the pipe surface on the gas tightness performance of joints under pressure loading. Based on the PC model for gas flow in seal gap of rough surface, the theoretical method for gas leakage rate at the joint of shield tube is established, and the results are compared with those of model tests, which proves the feasibility and applicability of the theoretical method. Finally, by combining the model tests and the theoretical method, the measures to reduce the gas leakage rate of joints are put forward.