地铁车站盖挖逆作法深基坑地连墙变形机理研究

Research on the deformation mechanism of the connecting wall of the deep foundation pit with the reverse method of cover and excavation of the subway station

地铁车站一般位于城市中心,面临着复杂的周边环境,对基坑变形控制要求较高,选择合适的施工方法、地连墙深度、厚度等参数可以限制地连墙变形,以此保证基坑安全。依托天津地铁7号线肿瘤医院站基坑工程,采用有限差分软件FLAC3D建立数值模型,并通过改变开挖方法、地连墙深度与厚度、楼板刚度等模型变量,研究了盖挖逆作法深基坑地连墙受力变形规律。结果表明:数值模拟与监测数据所反映的水平位移变化规律基本一致,楼板对地连墙上部水平位移有明显的约束作用;明挖法地连墙变形量大于盖挖逆作法,地连墙侧移最值发生深度有向下发展的趋势;增加地连墙深度与厚度,墙体水平位移不断减小,但最大位移发生深度却始终在开挖面附近。虽然地连墙深度与厚度可以减小其变形,但存在临界值,超过该值对其变形的影响减弱;提高楼板混凝土等级,地连墙水平位移最值不断减小,对开挖面上部地连墙影响较大,对基坑深部土体影响较小。

Subway stations are generally located in the center of the city, facing complex surrounding environments, and have high requirements for the control of foundation pit deformation. Selecting appropriate construction methods, depth and thickness of ground connecting walls and other parameters can limit the deformation of ground connecting walls, so as to ensure the safety of foundation pits. In this paper, relying on the foundation pit project of Tianjin Metro Line 7Cancer Hospital Station, the finite difference software FLAC3D is used to establish a numerical model. The law of force and deformation of the foundation pit wall. The results show that the variation law of the horizontal displacement reflected by the numerical simulation and the monitoring data is basically the same, and the floor slab has an obvious constraining effect on the horizontal displacement of the upper part of the ground connecting wall;The occurrence depth of the maximum displacement has a downward trend;increasing the depth and thickness of the ground connecting wall,the horizontal displacement of the wall body decreases continuously, but the maximum displacement occurrence depth is always near the excavation surface. Although the depth and thickness of the ground connecting wall can reduce its deformation, there is a critical value, beyond which the influence on its deformation is weakened;when the concrete grade of the floor is increased, the maximum horizontal displacement of the ground connecting wall is continuously reduced, which has a negative impact on the ground on the upper part of the excavation surface. The impact of the connecting wall is greater, and the impact on the deep soil of the foundation pit is less.