Research On The Deformation Law Of The Subway Station Foundation Pit Based On FLAC3D

The open surface method is used for the deep foundation pit excavation construction of Qianshan road station of Hefei rail transit line 2. The deformation caused by the excavation scheme is the key point of construction technology control. Selecting reasonable supporting system is the key to ensure the smooth construction of foundation pit. Therefore, accurately grasping the excavation deformation mechanism of subway station has important guiding significance to the foundation pit retaining structure design and safety construction.In this paper, the monitoring scheme of deep foundation pit in Qianshan Road station are described, and monitoring results about Lateral displacement of retaining structure, the ground settlement and uplift in the bottom of pit caused by excavation of foundation pit are also analyzed. Using FLAC3D for the construction of deep foundation pit excavation of the whole process of Qianshan road station is studied by numerical simulation, compared the calculation results under different conditions with the measured data. With the help of FLAC3D software, a numerical study is conducted on the inherent factors and design factors affecting the deformation of foundation pit. The main results are as following:(1) Monitoring results show that:With the increasing of excavation depth, the horizontal displacement of retaining structure increase gradually, and the maximum horizontal displacement moves down gradually, which has the feature of "parabola" shape distribution:small at both ends, big at the middle. Approximately "groove" distribution of surrounding ground settlement outside the pit. The bottom heaved in the middle and showed a upset pan shape in moving down on both sides.(2) Although the results of numerical simulation and measured results has some deviation in value, But the overall change law is basically the same, which shows that this model used to to simulate the pit excavation is feasible.(3) By FLAC3D finite difference software, this paper discusses the inherent and design factors affecting the deformation of foundation pit excavation. The changes of inherent factors as the elastic modulus of soil, soil cohesive force and angle of internal friction of soil factors will make the lateral deformation curve of the wall and the surface subsidence deformation curve changes in different degrees; In the design factors, increasing the depth of retaining structure, pile diameter and steel support stiffness, within a certain range can obviously control the lateral deformation of retaining structure and the surface subsidence deformation. But when the foundation pit is stable and reaches to a certain extent, the excessive increase has no use to reduce the deformation, it will even cause the waste of resources.