地铁基坑地下连续墙变形监测及数值模拟分析

Deformation monitoring and numerical simulation analysis of diaphragm wall in subway foundation pit

以天津某地铁出入段线深基坑地下连续墙围护结构为研究对象,通过监测现场变形数据,探究基坑开挖深度对墙体水平侧移、地表沉降、支撑轴力的影响;建立平面有限元模型,模拟基坑开挖及墙体水平变形过程。结果表明:墙体水平侧移沿深度呈“倒C形”分布,墙体最大水平侧移值(δ_(hm))的变化范围为基坑开挖深度(H_(e))的0.14%~0.38%,墙体最大侧移点埋深(H_(m))主要集中在(H_(e)–3,H_(e)+4)之间;墙后地表最大沉降(δ_(vm))大多数处于(0.145%~0.280%)H_(e)之间,δ_(vm)与对应δ_(hm)存在δ_(vm)=1.17δ_(hm)的近似关系。模型土体弹性模量取为压缩模量2倍时,模拟值与实测值接近。研究结果为认识天津富水软土地层基坑的变形规律提供参考。

Taking the retaining structure of diaphragm wall in a subway entrance and exit line deep foundation pit in Tianjin as research object,this paper explored the influence of horizontal lateral displacement of wall,surface settlement and supporting axial force along excavation depth through monitoring the deformation data.Plane finite element numerical simulation model was established to simulate the foundation pit excavation process and diaphragm wall horizontal deformation.The results demonstrate that the horizontal displacement of diaphragm wall presents an"inverted C-shape"distribution along depth,and the variation range of maximum horizontal displacement value of diaphragm wall is between (0.14%~0.38%) foundation pit excavation depth (H_(e)),and the buried depth of maximum lateral displacement point (δ_(hm)) is mainly concentrated between (H_(e)–3,H_(e)+4).Maximum ground settlement (δ_(vm)) behind wall is mostly between (0.145%~0.280%) H_(e),and there is an approximate relationship between δ_(vm)and δ_(hm):δ_(vm)=1.17 δ_(hm).When the elastic modulus of soil is twice the compression modulus,the simulation results are close to the measured values.The research results can provide a reference for summarizing the deformation regularity of foundation pit in water-rich soft soil layer in Tianjin.