王兴波

中铁昆明投资公司重庆地铁建设指挥部

摘要：四川省宜宾市屏山县岷江大桥主桥为T型刚构连续梁，其4、5号桥墩基础均采用双壁钢围堰施工，为保证围堰的结构设计经济合理，故对该桥4号、5号主墩承台围堰通过MIDAS程序进行三维空间建模，并对各种杆件赋予各自材料特性，结合具体施工流程.通过分析套箱和内支撑的不同施工阶段的最不利工况，找出施工工程中的主要控制工况，根据计算结果对围堰结构进行优化处理。结果表明：在工况3，即围堰封底混凝土浇筑完毕并达到设计强度后，对套箱内进行抽水时，围堰的受力与变形明显增大，可通过增大环板厚度等手段可显著减小围堰受力；此外，不同工况下围堰的应力集中部位比较明显，可以加强该部分构造；封底混凝土的厚度也可以通过MATLAB求得同时满足强度和稳定性的最优解。

关键词：承台；双壁钢围堰；受力分析；设计计算；有限元法

Abstract：The main part of the Minjiang Bridge that locates in Pingshan County Yibin City Sichuan Province，is a continuous girder of T-Shaped steel structure. Its foundation of number 4 &5 bridge pier both adopts the double-wall steel boxed cofferdams construction methods. In order to make sure the structural design of cofferdam is economical and reasonable，the three-dimensional finite element soft-ware MIDAS was used to analyze the cofferdam structures and define various bar their material properties，combined with specific construction process，。Through the analysis of the different construction of box and inside support phase the most unfavorable conditions，we can find the main working condition of control in construction engineering and to optimize the cofferdams structure according to the calculating results. The results show that the stress and deformation of the cofferdam are increased when the base sealing concrete for the cofferdams reaches its designed strength and when water inside the cofferdams is pumped out. We can reduce the force of the cofferdams by increasing of thickness of surrounding plates. Besides，the cofferdams stress focusing parts may obvious and different under vary working conditions，which can strengthen the formation of these parts；the thickness data of the bottom sealing concrete can be also obtained by MATLAB as well as satisfying the intensity and stability of the optimal solution.

Key words：cushion cap；double-wall steel boxed cofferdam；force analysis；design calculation；finite element method

1 概述

屏山岷江大桥位于四川省宜宾市 屏山县新县城旁的岷江之上，南北方向纵跨岷江。大桥桥梁全长816.08m，桥面宽度为16.5m，主桥为T型刚构连续梁，桥跨布置为130.5m（边跨）+235m（主跨）+130.5m（边跨），梁体采用悬臂现浇，共29节段，引桥北岸为3×30m预制简支梁跨，南岸为7×30m预制简支梁跨。

4号、5号主墩基础采用φ2.8m 钻孔灌注桩群桩结构，每个墩布置8 根桩，承台采用倒角矩形形式，承台的平面尺寸为16.8m×16.8m，水中墩承台顶面设计高程为+2.0m，采用水下混凝土封底，封底厚度為250cm。水中墩均采用双壁钢围堰施工，钢围堰沿着护筒周围的导向架下放，单个墩钢围堰外壁尺寸为21m×21m，钢围堰高度分别为18m、20m。……