西安地铁车站深基坑变形规律FLAC模拟研究

Research on the deformation law of deep excavation supporting structure in metro station of Xi'an by FLAC simulation

开展西安地铁深基坑变形规律理论与监测的研究对指导西北地区深基坑信息化施工具有重要价值。本文以西安地铁2号线某车站深基坑工程为背景,完成了车站深基坑施工监测方案设计,对深基坑施工过程进行了FLAC计算模拟,重点研究了桩体变形、钢支撑轴力、基坑周边地表变形规律。结果表明,复杂环境下城市地铁车站站深基坑明挖施工时,现场监测是信息化安全施工的保证,采用钻孔灌注桩和钢支撑的复合围护方案作为车站深基坑的围护结构是合理的,土方分层开挖方式和钢支撑预应力施加是减少空间效应保证安全施工的重要措施。桩身水平位移特别是桩顶水平位移是围护结构变形特性的直接反映,围护桩变形最大的地方为基坑中部到三分之二基坑深度处。基坑围护结构附近的地面隆起量明显小于基坑中部的隆起量,随着开挖深度增大,隆起量逐渐由基坑中部最大转变为两边大中间小的型式。

The study on the theory of deformation laws and monitoring of deep excavation in metro station in Xi＇an has great significance to guide informational construction in deep excavation in northwest.Taking the deep excavation of a metro station of Xi＇an subway 2 line as the engineering background in this paper,the design of the monitoring plan on deformation of deep excavation of a metro station was completed,the simulation calculation on construction process of deep excavation was given by FLAC,and the pile deformation,the axial force of steel support and ground settlement around foundation were mainly studied.The results showed that when open excavation construction was carried out in deep excavation of city subway transfer station under complex environment,in-situ monitoring was a useful measure for safety guarantee to information construction.It was rational that compound maintenance program including bored pile and steel support should be adopted to be as supporting structure of deep excavation of metro station.Stratified excavation method of earthwork and applying prestress to steel support were the important measures of reducing spatial effect and guarantee safe construction.The horizontal displacement of pile body,especially pile top was a direct reflection of deformation of the retaining structure,the maximum deformation of supporting pile was from the middle to two-thirds of foundation depth.The ground heave around supporting structure of foundation was much less than the middle of foundation,and as the excavation depth was increasing,the amount of heave in the central part gradually shift from the pit on both sides of a large middle small type.