兰州地区地铁深基坑监测及变形规律
首发时间:2018-09-18
摘要:以兰州地铁二号线某地铁站深基坑工程为依托,结合基坑施工设计要求与现场地质情况,制定了合理的监测方案。通过对地表沉降、围护桩桩体位移、支撑轴力等系列观测数据对比分析,表明钻孔灌注桩加内支撑的支护体系设计合理;结合地层特点,分析了该车站主要断面处地表沉降、桩体位移、支撑轴力等随基坑开挖深度和时间的变化规律。结果表明,地表沉降随基坑开挖深度的增加而增大,最大沉降位移出现在距坑边4m处,沉降值约13mm;桩体最大水平位移位置随基坑开挖不断下移,最大变形在距坑底6m,最大水平位移值为8mm;基坑开挖初期,轴力随开挖深度的增大而增大,开挖后期轴力变化幅度较小,且轴力的变化与周围土层的性质具有一定的相关关系。
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Monitoring and deformation law of deep foundation pit in Lanzhou area
Abstract:Based on the deep foundation pit project of a subway station of Lanzhou Metro Line 2, combined with the design requirements of the foundation pit construction and the site geological conditions, a reasonable monitoring plan was formulated.Through the comparative analysis of a series of observation data such as surface settlement, displacement of retaining piles and supporting axial force, it is shown that the design of the supporting system of bored pile and internal support is reasonable.Combined with stratum characteristics, the variation of surface subsidence, pile displacement and support axial force at the main section of the station with excavation depth and time is analyzed. The results show that the surface settlement increases with the increase of the excavation depth of the foundation pit.The maximum settlement displacement occurs at 4m from the edge of the pit, and its value is about 13mm. The maximum horizontal displacement position of the pile is continuously moved down with the excavation of the foundation pit, and the maximum deformation is 6m from the bottom of the pit. The maximum horizontal displacement value is 8mm.In the initial stage of foundation pit excavation, the axial force increases with the increase of excavation depth.The axial force variation in the later stage of excavation is less, and the change of axial force has a certain correlation with the properties of the surrounding soil layer.
Keywords: deep foundation pit;Foundation pit monitoring;Law of deformation;Collapsible loess
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