温州瓯江北口大桥中塔沉井基础设计

温州瓯江北口大桥主桥为主跨2×800m的三塔双层桥面钢桁梁悬索桥。针对该桥在深水、复杂海域环境中,中塔基础所受弯矩大、船撞力大及基岩埋深大的特点,中塔采用防撞能力强、刚度大、经济性更优的倒圆角矩形沉井基础。沉井总高68m,下部为填充混凝土的钢壳结构,高59m;上部为钢筋混凝土结构,高9m。在钢沉井高度方向上每隔1.5m设置1道水平桁架,内、外壁板设置竖向加劲肋。为保证结构耐久性,钢沉井壁板厚度预留腐蚀余量,并对上部钢沉井外表面进行重防腐涂装。建议设置沉井着床定位系统,并进行海床预防护控制沉井着床精度;采用严格控制结构水密性、设置射水管等措施保证沉井下沉的安全性及姿态可控。

Design for Open Caisson Foundation of Middle Tower of Oujiang River North Estuary Bridge in Wenzhou

The main bridge of the Oujiang River North Estuary Bridge in Wenzhou is a steel truss suspension bridge with a structure of three-tower and double-deck, having a main span of 2×800 m. The bridge in deep water and complex marine environment possesses following characteristics, for example, the middle tower foundation is subjected to large bending moment, large ship collision force, and the embedded depth of bedrock is deeply. Consequently, the chamfered rectangular open caisson foundation with strong anti-collision ability, high stiffness and better economy is adopted. The total height of the open caisson is 68 m, the lower part is structured with 59 m steel shell filled with concrete, and the upper part is structured with 9 m reinforced concrete. In the height direction of steel open caisson, a horizontal truss is set at an interval of every 1.5 m, and vertical stiffening ribs are set on the inner and outer panels. In order to ensure the durability of the structure, corrosion allowance is reserved for the thickness of the steel open caisson wall, and heavy corrosion protection coating is applied to the outer surface of the upper steel open caisson. It is suggested that an implantation positioning system of open caisson should be set up, and seabed preventive protection should be carried out to control the implantation accuracy of open caisson. Measures such as strict control of water tightness of structure and set up water-jet pipes are adopted to ensure the safety of open caisson sinking and pose controllable.