芜湖长江三桥3号桥塔墩设置沉井基础设计  

Design of Caisson Foundation for Pylon Pier No.3 of Third Wuhu Changjiang River Bridge

作　　者：张州[1] 易伦雄[1] 吴国强[1] ZHANG Zhou;YI Lun-xiong;WU Guo-qiang(China Railway Major Bridge Reconnaissance & Design Institute Co. , Ltd. , Wuhan 430056, China)

机构地区：[1]中铁大桥勘测设计院集团有限公司,湖北武汉430056

出　　处：《桥梁建设》2021年第3期100-107,共8页Bridge Construction

基　　金：京福铁路客运专线安徽有限责任公司科技研究开发计划课题(2015-G-01A)。

摘　　要：芜湖长江三桥为主跨588 m的非对称矮塔斜拉桥,其3号桥塔墩处水深约25 m,水下岩石直接出露,弱风化岩层厚4~9.5 m,其下为单轴抗压强度75 MPa的微风化岩石。从结构受力、施工便捷及经济性等方面,对桩基础和设置沉井基础2种基础型式进行比选,由于设置沉井基础受力明确、施工便捷、工期较短、经济性较优,推荐采用。对设置沉井基础的结构形式、基础底面高程、顶面高程及盖板与井壁的连接方式进行研究,确定3号桥塔墩设置沉井基础选择钢结构形式,基础顶高程-5.5 m、底高程-25.0 m,基底置于微风化闪长玢岩中,沉井盖板与井壁采用PBL剪力键与剪力钉连接,设置沉井基础为圆端形,平面尺寸为65 m×35 m,高19.5 m,平面分为21个井孔。对设置沉井基础施工期、运营期及船撞、地震特殊荷载工况下的结构受力进行检算,结果表明各工况下结构受力均满足要求。设置沉井基础解决了深水裸岩建设条件下常规桩基础施工困难的问题,开拓了新型深水桥梁基础型式。The Third Wuhu Changjiang River Bridge is an asymmetrical extradosed bridge with a main span of 588 m.The pylon pier No.3 is located where the water depth is about 25 m and rocks are exposed.The weakly weathered rock layer is about 4 to 9.5 m thick,and the underneath slightly weathered rocks display uniaxial compressive strength of 75 MPa.Two types of foundations,namely the pile foundation and caisson foundation,were compared from aspects of load bearing behavior,construction efficiency and economy.The caisson foundation was recommended,considering the benefits in load bearing behavior,ease-of-construction,effective construction schedule management and economic performance.Studies were carried out to determine the configuration of caisson foundation,top and base elevation and the connections between caisson cap and walls.As per the results,the steel caisson foundation with top and base located respectively at elevations of-5.5 m and-25.0 m was finally used.The base of the caisson foundation should be set in the weakly weathered diorite porphyrite,and the caisson cap and walls are connected by PBL connectors and shear studs.The caisson foundation is a roundcornered foundation measuring 65 m by 35 m,19.5 m in height and consisting of 21 cells in plan.The load bearing conditions of the caisson foundation in both the construction and operation stages as well as under irregular loads,such as ship collision and seismic actions,were verified.The results show that the load bearing capacity of the caisson structure in various loading conditions can meet the requirements.The caisson foundation of such type avoids the construction issues specific to conventional pile foundation in deep water area with exposed rocks,and is a deep water foundation option for bridge.

关 键 词：公路铁路两用桥 斜拉桥 设置沉井基础 结构检算 特殊荷载 有限元法 基础设计 

分 类 号：U448.27[建筑科学—桥梁与隧道工程] U443.131[交通运输工程—道路与铁道工程]