邻近基坑的北京地铁某暗挖通道变形监测与数值分析

Deformation Monitoring and Numerical Analysis of Subway Tunneling with Mining Method Adjacent to Foundation Excavation in Beijing

地铁暗挖通道与邻近基坑同步开挖是一项具有较大风险源的工程。以北京某邻近基坑的地铁暗挖隧道工程为背景,采用FLAC3D进行三维数值模拟,分析了同步开挖情况下基坑围护桩水平位移、基坑周边地面沉降,及不同开挖顺序对基坑稳定性影响等问题,并结合施工现场监测结果研究暗挖通道开挖对明挖基坑的影响。结果表明:基坑开挖初期,围护桩呈向坑内变形的前倾型曲线,地表沉降迅速发展,在暗挖通道的同步开挖影响下,围护桩中、下部水平位移快速向坑内发展,变形曲线转变为弓形,随着暗挖通道中、下台阶的开挖,位移继续增大,最大水平位移发生在第2,3道钢支撑之间。

The synchronous excavation of subway tunneling with mining method and adjacent foundation excavation is a project with great source of risk. Based on one example ofmined tunnel excavation work close to a foundation excavation in Beijing,the simulation of the whole excavating process with FLAC3 Dwas established,with the focus on the horizontal displacement of pile and ground settlement under synchronous excavation,and stability influence of foundation excavation at different excavation sequence. Meanwhile,combined with monitoring data,the influence of the excavation of subway tunneling withminingmethod on the foundation excavation is researched. The results show that horizontal displacement inclined to the pile,present a procline curve in the initial stage of excavation,and ground settlement development rapidly. With the influence of themined tunnel synchronous excavation,horizontal displacement at middle and bottom section of pile develop to the foundation excavation quickly,deformation curve is converted to a bow. Along with the excavation of middle and bottom bench,horizontal displacement of pile continue to increase,the maximum value occurs between the second and the third steel supports.