深基坑倒挂井壁法开挖对地层变形影响研究

Study on the influence of deep foundation pit excavation by the method of inverted shaft wall on ground deformation

为了研究倒挂井壁法基坑施工过程中周围土体和井壁的变形情况,以位于成都市牛市口的我国首个共享单车智能停车库基坑工程为背景,通过施工现场人工测量和自动化监测数据分析了基坑附近地层变形情况,然后采用有限差分法建立井壁土体共同作用的三维计算模型,将模拟结果与监测结果进行对比,研究了基坑周围土体竖向沉降和基坑井壁横向收敛的变化规律。结果表明:倒挂井壁法能保证较小的施工变形,且施工变形以水平向变形为主;采用倒挂井壁法施工,土体在施工初期会出现少量隆起,然后随土体开挖而下沉,当初衬封底之后,基坑周围土体不再发生沉降;基坑井壁横向收敛最大值发生在井壁约0.7倍深度位置。

In order to study the deformation of the surrounding soil and the shaft wall during the construction of the foundation pit by the method of inverted shaft wall,the change rules for the vertical settlement of the soil around the foundation pit and the lateral convergence of the foundation pit wall are studied.The first shared bicycle intelligent parking garage in China is located at Niushikou in Chengdu;this paper,based on the foundation pit project of this bicycle parking garage,uses manual and automatic monitoring data of the construction site to analyze ground deformation near the foundation pit,and uses the finite difference method to establish a three-dimensional calculation model of the interaction between the shaft wall and the soil mass to compare with the monitoring analysis result.The results show that:the method of inverted shaft wall can ensure the smaller construction deformation,and the construction deformation is mainly of horizontal deformation;in the construction of inverted shaft wall method,a small amount of uplift will occur in the initial stage of construction,then the soil sinks as excavation proceeds,and the settlement of the soil around the foundation pit will not occur again after the initial lining is sealed;the maximum lateral convergence of the foundation pit occurrs at about 0.7 times the depth of the pit wall.