Based on three-dimensional finite difference program FLAC3D,the deformation characteristic of enclosed structure and the heave deformation of the foundation pit in sand and clay are analyzed.By adjusting the excavation diameter of the cylindrical foundation pit,the influence of excavation diameter on the deformation characteristic of the foundation pit is investigated.The numerical results show that the soil type have no effects on the deformation distribution characteristic of the foundation pit,the horizontal displacement distribution characteristic of enclosed structure is "backbends",and the maximum horizontal displacement is increased with the excavation diameter.The insertion ratio of the enclosed structure should be controlled within 0.67 in order to reduce the lateral displacement of the enclosed structure.The heave deformation of the foundation pit is increased with excavation depth,and the maximum horizontal displacement will not increase with the excavation diameter when the excavation diameter reaches 60 m.The maximum heave deformation is occurred at the region about 0.2-0.8 times of the excavation diameter.%基于三维有限差分程序FLAC3D,分析了砂土及黏土中圆形基坑开挖引起的维护结构及坑底隆起变形规律特性,并通过调整圆形基坑的开挖半径,研究了基坑开挖半径对维护结构及坑底隆起变形的影响,数值模拟结果表明:土体类别对基坑变形特性分布没有显著影响;圆形基坑维护结构变形呈“后仰”式分布,且最大水平位移随开挖半径增大而不断增加,当连续墙结构其插入比控制在0.67左右时,其基坑变形大小能满足规范设计要求;随着开挖深度的增加,坑底隆起变形逐渐增大,当开挖半径达到60m后,最大隆起变形不随开挖半径的增大而增加,且最大隆起变形区域基本位于0.2～0.8倍的开挖半径范围内.
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