平潭海峡公铁两用大桥航道桥基础设计与施工创新技术

平潭海峡公铁两用大桥为国内第一座跨海峡公铁两用大桥,桥址海域风大、浪高、水深、流急、潮汐显著,且岩面倾斜起伏大、裸岩硬岩分布广,气象水文及地质条件均十分复杂,尤其是桥址海域波流力巨大,为桥梁下部结构设计和施工带来前所未有的困难。为解决风浪作用和通航船撞力作用,3座大跨度通航孔斜拉桥在基础设计和施工中采用多项创新技术,首次选用4.5 m的钻孔桩;为解决复杂海域大直径钻孔桩难题,研发了KTY5000型动力头钻机和相关配套的打桩设备;为克服波浪力作用,部分深水裸岩区域采用导管架辅助建立施工平台;为适应桥位独特的海洋环境,3座大跨度通航孔斜拉桥主塔墩承台均采用圆端哑铃形高桩承台,承台顶露出高潮位以上,承台施工采用集主体防撞结构与施工围堰一体的防撞箱围堰结构,永久结构与临时结构相结合,节约材料的同时降低了施工的安全风险性。其大型防撞箱围堰采用工厂整体制造、整体吊装、整体下放,实现模块化、标准化施工,哑铃形承台系梁范围采用无封底混凝土施工创新技术。

Innovative Technology in Channel Bridge Foundation Design and Construction of Pingtan Strait Hi-Rail Bridge

Pingtan Strait combined highway and railway bridge is the first cross-sea hi/rail bridge in China. In the sea area where the bridge is located with strong wind,high waves,deep water,rip current and apparent tides. In addition,the rock surface inclination fluctuates greatly,exposed rock/hard rock spreads extensively,meteorological,hydrological and geological conditions are all very complicated,especially in the sea area where the bridge is located with huge wave-current force,and all these make the design and construction of the bridge substructure unexpectedly difficult. In order to solve the wind/wave action and ship impacting force action when navigation is proceeding,multi-innovative technologies are adopted during foundation design and construction of three large-span navigable cable-stayed bridges,and drilled piles of 4. 5 m diameter are used for the first time. Type KTY 5000 power head drilling machine and relevant pile-driving equipment are studied and developed to solve the problems in drilled piles construction in complicated sea areas. Construction platforms supported by jackets frames are built in some deep water exposed rock areas to overcome the wave force action. In order to adapt to the unique environment in the bridge location,dumb-bell type high pile caps are used on the main tower pier caps of the three large-span cable-stayed bridges to allow the cap top above high tide level. During cap construction, the main body anti-collision structure is integrated with construction cofferdam and the permanent structure is combined with the temporary structure, which not only savematerials,but also reduce construction safety risks. The large scale collision protection box cofferdam is manufactured completely in plant and handled wholly to fulfill modular and standardized construction.Innovative technology of concreting without bottom cover is applied in dumb-bell type cap beam construction.