| Tunnels are good solutions to transportation problems in large cities separated by large rivers. Immersed Tube Tunnel (ITT) is a principal choice because of its unique advantage in the currently existing construction way. Above-water operation of tunnel elements is a key step of ITT construction, and which is complex and can be divided into element tugging, immersing and so on. The research of movement, resistance property and force of water in the tugging and immersing is very important.The research way of element is model experiment currently which is insufficient. Besides, this paper takes the Guangzhou Zhoutouzui ITT construction as the background. It includes equivalent section element and mutative section element. The mechanical problem in the tugging and immersing of mutative section element is more complicated. So the research needs theory analysis combines with experiment and numerical simulation.First of all, combining with fluid mechanics and theory of ship motions in waves, mechanical behavior of element in tugging and immersing process is analyzed. Moreover, the relevant physical model and mathematical equation are established. The most important point is resistance property and force feature of element including wave and wind.Secondly, the development of CFD, control equation of fluid dynamics and numerical simulation of turbulence are introduced. The Realizable k-e model and SST k-ωmodel are used to simulate the turbulence in this paper.Thirdly, the numerical simulation experiment of tugging and immersing is working with the software of STAR-CCM+ and CFdesign. Firstly, the Zhujiang ITT which is near the Zhoutouzui ITT and has analogous environmental condition is selected. By comparing the calculated results with experimental results, it shows that this paper's method is effective. Then the Biologic Island ITT used as a model for the Zhoutouzui ITT with a scale near 1:1 and the Zhoutouzui ITT is simulated. The condition contains wave and no-wave. The results tell us:1. The SST k-ωmodel is more suitable than Realizable k-e model in the simulation of floating object with free surface. Increasing the turbulence intensity and viscosity ratio will get a better result. 2. When the velocity of water and tube element is low, the pressure distribution likes the one in static water. The resistance coefficient in shallow water is bigger than the one in deep water.3. The distance from top of tube to water surface transforms in the range of 0.05m～0.10m while the influence from 0.6% to 35.9% in an average of 6%. Cx reduces while the velocity of tube element increases in the range of 0.6m/s～1.2m/s. The bottom of "U" curve will be the best velocity.4. Cx increases because of the wave. Cx additional extent increases from 0.79% to 36.75% while the velocity of tube element increases in the range of 0.8m/s～1.2m/s.5. Though the front area of mutative section element is larger than the equivalent section element's, the resistance coefficient is smaller in some situation because the former is more streamlined. A suitable incline angle will reduce the resistance coefficient.6. The mooring force and hanging force transform complicated and dynamicly in the tube element immersing. Both of them become smaller while the tube immerses more deeply. In a certain depth both of them become larger while the velocity of water increases. In this paper 0.45m/min is the best immersing velocity.7. The mooring force of equivalent section element or mutative section element keeps ahead alternately. Their mooring force and hanging force become smaller while the tube immerse more deeply.The above mentioned research work will be a base of making suitable plan for the tugging and immersing of element in Zhoutouzui ITT.
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