武汉鹦鹉洲长江大桥主桥基础工程施工技术

Construction Techniques for Foundation Works of Main Bridge of Yingwuzhou Changjiang River Bridge in Wuhan

武汉鹦鹉洲长江大桥主桥为(200+2×850+200)m三塔悬索桥,该桥北锚碇为"带孔圆环+十字隔墙"重力式沉井基础,沉井外径66m,高43m;1号塔基础为44根φ2.0m钻孔灌注桩,2号塔基础为39根φ2.8m钻孔桩;3号塔基础为20根φ2.8m钻孔桩;南锚碇为"圆形嵌岩地下连续墙+内衬"结构形式,地下连续墙为钢筋混凝土结构,外径68m,壁厚1.5m。根据该桥基础特点,北锚碇沉井采用3轮接高、3次下沉施工;1号塔基础采用筑岛、双排防护桩施工方案;2号塔基础采用先钢围堰后平台的施工方案,钢围堰采用气囊法整体下河;3号塔基础采用先平台后围堰、单排钻孔防护桩施工方案;南锚碇采用液压铣槽机配合冲击钻施工地下连续墙的施工方案。

The main bridge of Yingwuzhou Changjiang River Bridge in Wuhan is a three-tower suspension bridge with span arrangement （200＋2 × 850 ＋200） m. The foundation for the north anchorage of the bridge is the gravity caisson foundation of ＂holed ring＋crisscross partition walls＂. The external diameter of the caisson is 66 m and the height is 43 m. The foundation for the Tower No. 1 is comprised of 44 nos. of φ2.0 m bored piles, for the Tower No. 2 is of 39 nos. of φ2.8 m bored piles and for the Tower No. 3 is of 20 nos. of φ2.8 m bored piles. The foundation for the south anchorage is the kind of the foundation of ＂circular rock-socketed diaphragm wall＋ lining＂. The diaphragm wall is the reinforced concrete structure, the external diameter of the wall is 68 m and the thickness is 1.5 m. In the light of the characteristics of the foundation works of the bridge, the caisson for the north anchorage was constructed by the caisson height extending and caisson sinking in 3 times..The pile foundation for the Tower No. 1 was constructed by the scheme of artificial island and by the double-row protection bored piles. The foundation for the Tower No. 2 was constructed by the scheme of constructing the steel cofferdam first and the working platform late, in which the cofferdam was launched to the river by the air bag method in integrity. The foundation for the Tower No. 3 was constructed by the scheme of constructing the working platform first and the cofferdam late and by the single-row protection bored piles and the diaphragm wall for the south anchorage was constructed by the scheme of hydraulic trench cutter aided by percussion boring.