Study on Heat Transfer at Steel-Concrete Interface of Shield Tunnel Composite Segment under Fire

During the actual construction process and operation period of the tunnel project, due to improper construction operation techniques, long-term load effects, concrete shrinkage and creep, etc., it is difficult for the steel plate and concrete to be in close contact, and there is a void between the two. This results in discontinuous heat transfer. In order to seek the real heat transfer state between steel plate and concrete under high temperature of fire, this paper mainly adopts the methods of model test, theoretical analysis and numerical simulation to study the heat transfer of composite segment steel plate and concrete contact interface under high temperature of fire. The heat transfer process between steel plates and concrete with different thicknesses at different void heights is studied, the temperature time history curve is obtained, and the temperature at the interface and the transition heat transfer coefficient are calculated. The results show that within 5 minutes of the fire, the heat is basically absorbed by the steel plate, the temperature of the concrete is basically unchanged, and the transition heat transfer coefficient rapidly decreases from 1.0 to about 0.2–0.3. When the fire continues to develop, the concrete temperature increases rapidly and the transition heat transfer coefficient increases. With the increase of the void height, the temperature difference between the concrete interface and the steel plate interface gradually increases. According to the data fitting, the relationship between the concrete interface temperature T and the time x and the void height t is obtained. It can be used to calculate the temperature of the concrete interface at a certain moment when the composite segments with different clearance heights are on fire, which has important engineering application value for reducing the adverse consequences of shield tunnel fire.