Effect Factor And Control Method On Deformation Of Deep Pit Of The Subway Station In Soft Soil

In construction of the urban subway station in soft soil, if control measure is disadvantage, pit excavation will induce big deformation of foundation pit. It will affect seriously security and function of the surrounding construction. So it is strict with control of the surface settlement and deformation on foundation pit. Not only deep pit excavation must its assure security and stability, but also control of motion of the surrounding surface must be effective. So it is a very valuable research lesson on foundation pit deformation mechanism and control.Deformation of foundation pit is affected by many factors, such as soil character, form of support system, manner of excavation, groundwater and surrounding environment. So control of the deformation of support system and surrounding surface is focus of research. At present method of forecast the deformation of foundation pit have FEM, soil loss theory and empirical estimated calculation. FEM can comprise many factor effects to deformation of pit and forecast exactly deformation of pit. So FEM will be major method of deformation forecast. This paper introduces mostly the character of soft soil foundation pit, deformation mechanism, FEM theory, effect factor of foundation pit deformation and its control method.With the excavation of foundation pit, foundation pit will arises deformation. Deformation of foundation pit includes horizontal movement, Surface Settlement and upheaval in the bottom of the deep foundation. This paper use MARC FEM software simulate excavation step. In the course of numerical simulation, Drucker-Prager elastic-plastic stress-strain relation model is used to simulate character of soil. The model includes interaction between supporting structure and soil, which adopt contact element to simulate their contact character. In the mean time, stage excavation is comprised in the model, so development of forceand displacement are obtained. Shi-Yi subway station in Tientsin is analyzed by FEM. The factor of design, construction and soil is discussed in the numerical simulation. From discuss to the effect factor of foundation pit, effect factor sensitivity to deformation is analysed. So sensitive factor can be found out. Some useful conclusion is gained, such as proper inserting depth of retaining structure, proper thickness of continuous wall, and area of support pole and layer of the support pole. From discussion above, these conclusions are helpful to control deformation of foundation pit and avoid investment addition about account of irrational design. In the mean time, the control methods of deformation of foundation pit are summarized. This paper's conclusion provides reliable reference to design, informational construction and construction monitoring of deep foudation pit.