上下同步逆作法深基坑及邻近地铁车站变形分析

Analysis on deformation of deep foundation pit with synchronous top-down construction method and adjacent subway station

以北京上下同步逆作法基坑工程为背景,运用PLAXIS 3D有限元软件对上下同步逆作法基坑施工的全过程进行模拟,研究上下同步逆作法基坑的受力、变形特性及其对邻近地铁车站的影响。结果表明:上部结构施加的竖向荷载和地下连续墙水平荷载耦合会增大地下连续墙水平位移和弯矩;地下连续墙后有地铁车站存在时,由于其遮蔽作用,地表沉降范围随开挖深度增加基本不变,最大沉降比无地铁车站时大17%;随开挖深度增加,二期立柱的隆起随坑底隆起增大不断增大,而一期立柱则在坑底隆起和上部荷载共同作用下由隆起逐渐转为沉降;地铁结构埋深和距基坑边缘的距离对结构变形量和变形形式影响显著,地铁结构的最大变形与基坑开挖深度近似呈线性正相关。

Based on foundation pit project with synchronous top-down construction method in Beijing,PLAXIS 3D finite element software was used to simulate the whole construction process of the foundation pit project with synchronous top-down construction method,the force and deformation characteristics of the foundation pit with synchronous top-down construction method and the influence of its excavation on the adjacent subway stations were studied.The results show that the vertical load coupling with horizontal load on retaining wall will increase the horizontal displacement and bending moment of the retaining wall.When there is a subway station behind the diaphragm wall,due to its sheltering effect,the surface settlement range remains basically unchanged with the increase of the excavation depth,and the maximum settlement is 17%larger than when there is no subway station.As the excavation depth increases,the uplift of the second-stage column increases with the uplift increase of the pit bottom,while the first-stage column gradually changes from uplift to settlement under the combined action of the pit bottom uplift and the upper load.The buried depth of the subway structure and the distance from the edge of the foundation pit have a significant impact on the amount of structural deformation and the form of deformation.The maximum deformation of the subway structure is approximately linear positively correlated with the excavation depth of the foundation pit.