为了研究异形坑中坑开挖对基坑受力变形的影响,以广州白云站基坑项目为背景,根据现场监测数据及有限元软件Plaxis 3D还原现场施工模型,分析了非对称坑中坑开挖对基坑变形和稳定性的影响。结果表明:基坑非对称开挖导致两侧支护结构的水平位移不对称,超挖侧地连墙变形随内坑开挖深度增加而逐渐增大,而非超挖侧地连墙随着内坑开挖出现位移推回现象;建议在施工中加强对超挖侧地连墙和中部区域的监测与防护;由于基坑的超大超宽特点,基坑中部的支撑轴力会出现消散,使得中部支撑轴力小于角部轴力,特别是在2区开挖后,角部支撑轴力会突变,故实际工程需特别关注此类变形。
In order to study the influence of shaped pit-in-pit excavation on the mechanical deformation of foundation pit, this paper analyses the influence of asymmetric pit-in-pit excavation on the deformation and stability of foundation pit with the background of Guangzhou Baiyun Station Foundation Pit Project, based on the on-site monitoring data and the restoration of the on-site construction model by the finite element software Plaxis 3D. The results show that: The asymmetric excavation of the foundation pit leads to the asymmetric horizontal displacement of the supporting structures on both sides, the deformation of the ground-connected wall on the over-excavated side increases gradually with the increase of the excavation depth of the inner pit, while the ground-connected wall on the non-over-excavated side shows the phenomenon of displacement push-back with the excavation of the inner pit; it is recommended to strengthen the monitoring and protection of the ground-connected wall on the over-excavated side and the central area during the construction; at the same time, due to the characteristics of the foundation pit of oversize and extra width, the support axial force in the central part of the foundation pit will. At the same time, due to the super large and super wide characteristics of the foundation pit, the support axial force in the middle of the foundation pit will dissipate, making the central support axial force smaller than the corner axial force, especially after the excavation of Zone 2, the corner support axial force will change suddenly, so the actual project needs to pay special attention to this kind of deformation.
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