港珠澳大桥海中桥梁工程埋置式承台施工方案

Construction Scheme for Embedded Pile Caps of Sea-Crossing Bridge Projects of Hongkong-Zhuhai-Macao Bridge

港珠澳大桥海中非通航孔桥承台为埋置式(最大外形尺寸16m×12m),采用预制安装工艺,通过后浇混凝土与桩基连接。为克服桥址复杂的地质情况及自然条件,承台采用3种施工方案施工(大圆筒干法安装、分离式胶囊柔性止水、无内支撑结构双壁锁口钢套箱围堰),分别利用大圆筒、钢围堰和分离式胶囊止水结构(安装在承台和钢管桩结合处)、钢套箱围堰和封底混凝土创造干施工环境,进行墩台整体安装和后浇混凝土施工。大圆筒利用大型浮吊和八锤同步液压振动锤组进行海上打拔;分离式胶囊止水结构主要由环形托盘、内侧止水胶囊、顶面GINA止水带以及张拉收紧装置组成;双壁锁口钢套箱围堰采用分块拼装,整体下沉、整体拆除的工艺。从适用性、施工效果、便捷性及经济性等方面对比分析3种施工方案。实践表明,3种施工方案均能较好地克服恶劣海况的影响,有较好的适应性和施工效益,能在预定时间内完成承台施工。

The non-navigable sea-crossing bridge of Hongkong-Zhuhai-Macao Bridge seats on embedded pile caps that are constructed by prefabricating and assembling technique and connected to the pile foundation by the post concreting.To overcome the complex geological and environmental condition at the bridge site,the piles caps were constructed by combined use of three schemes,including the dry assembly with large cylinder,flexible water stopping by separated capsules and the double-wall interlocked steel box cofferdam with no inner bracing.The large cylinder,steel cofferdam and water stopping structure with separated capsules installed at the connection of the pile cap and the steel pipe pile,steel box cofferdam and base sealing concrete were used,such that dry construction environment can be created for the integrated installation of the pile cap and casting of the post cast concrete.The large cylinder was driven using large-scale floating cranes and the vibration driver with eight synchronized hydraulic hammers.The separated capsule water stopping structure is mainly made up of ring chassis,inner water stopping capsules,top GINA sealing belt and the tensioning and tightening devices.The double-wall interlocked steel box cofferdam adopts the technique of block-by-block assembling,monolithic sinking and demolition.The three schemes were analyzed from aspects of feasibility,construction effect,construction convenience and economy.The engineering practice proves that all the three schemes are able to overcome the influence of the severe sea condition well,have sound applicability and construction efficiency,and can ensure the pile cap construction to be completed in the scheduled period.