Abstract:

To explore the reliability of current force and bitts in floating transportation of variable crosssection of immersed tunnel, fluid dynamics model is established by means of CFD software based on Zhoutouzui immersed tunnel in Guangzhou. The current force to immersed tunnel during floating process is calculated and applicability of current force empirical formula in the present standard code for variable crosssection immersed tunnel is explored. On this basis, the reliability of bitts during the floating process is analyzed by ANSYS. The results show that current force empirical formula in the present standard code has applicability in some extent, but the empirical formula results exist noticeable differences with CFD results when using the resistance coefficient which corresponds to rectangular beams in the code. After amending the resistance coefficient, the empirical formula results agree well with CFD results. What′s more, the bitts are in elastic state without weakness of strength and stiffness and design plan is secure for floating transportation. In addition, the concrete structure around the crosssection of immersed tunnel is at inelastic stage with cracks under steel cable force, and local reinforcement of anchorage zone of bitts embedded parts is necessary to inhibit cracks development according to calculated results.

Key words: immersed tunnel, variable crosssection, current force, bitts, reliability, numerical simulation