沉管隧道变截面管段浮运水流力及系缆桩可靠性分析

为探索沉管隧道变截面管段浮运过程的水流力与系缆桩可靠性，以广州洲头咀沉管隧道为依托，借助CFD软件建立流体动力学模型，计算管段横向浮运所受的水流力并探讨规范水流力公式的适用性；以此为基础，利用ANSYS开展管段浮运系缆桩可靠性分析。研究表明： 1) 规范水流力公式具备一定的适用性，采用结构形式为矩形梁时对应的水流阻力系数会导致与数值计算结果存在不容忽视的差别，通过CFD计算结果修正后两者吻合较好； 2) 系缆桩处于弹性受力状态，刚度与强度均未被削弱，设计方案可满足浮运安全要求； 3) 钢丝绳拉力作用下管段结构混凝土处于带裂缝工作状态，需基于计算结果对系缆桩预埋件锚固区做局部加强以抑制裂缝发展。

Reliability Analysis on Current Force and Bitts in Process of Floating  Variable Cross section of Immersed Tunnel

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.