大尺寸三角形基坑变形特性的现场试验研究

依托上海软黏土地层的某大尺寸三角形深基坑工程，通过开展现场试验，对基坑施工过程中的地下连续墙的侧向变形、地表沉降进行了监测，并对监测数据进行了系统分析。监测结果分析表明:不同于矩形基坑，大尺寸三角形基坑连续墙顶部的水平位移约为其最大水平位移的４０％ ～７０％；深基坑开挖结束后，拆除混凝土支撑产生的附加水平位移约为基坑开挖引起的墙体水平位移的３０％ ～４０％；三角形深基坑开挖引起的最大连续墙水平位移介于０．０５％Ｈ～０．３５％Ｈ（开挖深度）之间，大于矩形和圆形深基坑引起的连续墙变形。这主要是因为三角形基坑的内支撑不能同时垂直于支撑两端的地下连续墙。深基坑的端部约束效应导致地下连续墙呈现出明显的三维变形特性，基坑中部墙体的水平位移明显大于两端位移。

Field Investigation of Deformation Characteristics of Large-scale Triangular Deep Excavation

Based on a large-scale triangular deep basement constructed in Shanghai soft clay, the horizontal displacement at the top of the diaphragm wall and surface settlement during construction are monitored by field tests. Unlike rectangular basements, horizontal displacement at the top of the diaphragm wall of large-scale triangular basement pit is about 40%~70% of its maximum horizontal displacement. After removing concrete props, horizontal displacement of retaining wall increased by 30%~40%. Upon completion of basement excavation, the maximum horizontal wall displacement of the large-scale triangular basement is in a range of 0.05%H^0.35%H(excavation depth), which is obviously larger than that of rectangular and circular basements. This is mainly because horizontal props cannot be installed perpendicular to retaining walls of triangular basement. Due to obvious corner effects, retaining wall presents obvious three-dimensional deformation characteristics(i.e., horizontal displacement in the middle of the wall is obviously larger than that at both ends).