Abstract: The immersed tunnel segments of EastWest Axis Project in Xiangyang are prefabricated by integral fullsection down pouring method, which is characterized by high strength, large crosssection and large volume, and the segment crack is difficult to control. In order to verify the feasibility and reliability of concrete mixing proportion, construction technology and crack control measures, the finite element software Midas FEA is used to conduct numerical simulation and calculation on hydration heat temperature stress of immersed tunnel joints under design conditions, and the internal temperature and stress variation of concrete during the casting of immersed tunnel segment are analyzed. The numerical simulation results show that the anticracking safety factor at the joint is low. Therefore, the chamfering position of the sidewall with the highest theoretical cracking risk and that of the middle separation wall with the highest construction difficulty are selected for model test. In the model test, the construction process of reinforced bars and embedded parts is simulated, the reliability of raw materials, mixing proportion, concrete construction performance, etc. are comprehensively checked, and an intelligent temperature monitoring system is set up. Through the partial block test, the structural types and installation procedures of reinforced bars and embedded parts are rationally optimized, so as to validate the concrete performance and optimize the construction mixing proportion. Meanwhile, the raw material temperature control standards are proposed to analyze the monitoring data for model testing.

Key words: immersed tunnel, immersed tunnel segment prefabrication, numerical simulation, partial block experiment, installation procedures, construction mixing proportion, temperature control measures