双龙特大桥新型组合式拱座基础设计与施工  

Design and Construction of Novel Composite Foundations for Skewbacks of Shuanglong Bridge

作　　者：陈新 岳伟勤 邓耀 陈奉民 苏小波 CHEN Xin;YUE Weiqin;DENG Yao;CHEN Fengmin;SU Xiaobo(China Railway Changjiang Traffic Design Group Co.,Ltd.,Chongqing 401121,China)

机构地区：[1]中铁长江交通设计集团有限公司,重庆401121

出　　处：《世界桥梁》2024年第6期28-35,共8页World Bridges

基　　金：重庆市交通科技项目(CQDJT-CZKJ2023-02)。

摘　　要：重庆巫山县双龙特大桥主桥为计算跨径245 m的中承式钢箱拱桥。双龙岸拱座位于溶隙普遍发育、溶蚀作用强烈的角砾状灰岩中,针对拱座处复杂的地质条件及受力要求,提出一种新型“墙式基础+竖桩”组合基础,墙式基础和竖桩分别承担水平推力和竖向压力,受力明确。拱座横桥向宽21.6 m,顺桥向长11 m,为钢筋混凝土重力式实体结构,采用承台群桩基础,拱座后接4 m厚背墙,背墙连接3根地梁,地梁后接墙式基础。计算结果表明:桩顶最大水平位移2.95 mm,单桩轴向受压承载力安全系数2.22,墙式基础最大主拉应力0.35 MPa,拱座基础抗推、抗压、抗裂能力强。拱座基础按地梁、墙式基础和拱座开挖→桩基开挖、浇筑→墙式基础、地梁和拱座浇筑的顺序施工,并采取注浆加固、护壁支护、桩基防水等施工防护措施,确保施工安全。The main bridge of Shuanglong Bridge in Wushan County,Chongqing is a half-through steel box arch bridge spanning 245 m(calculated main span length).The Shuanglong-side skewback stands in breccia limestone featuring dense dissolution gaps and strong dissolution effects.To address the complex geological conditions and build skewbacks with the required load bearing capacity,a composite foundation consisting of a wall foundation and vertical piles is proposed,where the former would accommodate the horizontal thrust and the latter would resist vertical compression.The skewback,measuring 21.6 m along bridge width and 11 m along bridge length,is a solid gravity structure that is supported by a pile cap and multi-pile foundation.The 4 m-thick backwall behind the skewback connects with 3 ground beams which are in turn connected with the wall foundation.The calculations demonstrate that the foundations of skewbacks own large thrust-,compression-and cracking-resistant margins,with a maximum allowable pile-top horizontal displacement of 2.95 mm,a safety coefficient of 2.22(axial compression resistance of a single pile),and a maximum normal tensile stress of 0.35 MPa(wall foundation).The construction of the skewback started from the ground beams,sequentially followed by the excavation of the wall foundation and skewback pits,piling,and the casting of the wall foundation,ground beam and skewbacks.Multiple construction protection measures were employed to ensure the construction safety,including grouting,adding counterfort retaining walls and implementing foundation waterproofing.

关 键 词：中承式拱桥 拱座 “墙式基础+竖桩”组合基础 背墙 地梁 结构设计 受力分析 施工防护 

分 类 号：U443.23[建筑科学—桥梁与隧道工程] U442.5[交通运输工程—道路与铁道工程]