The Slection Of Foundation Pit Sopport And Its Optimization Design

The foundation pit is a systematic project; the selection of deep excavation support system and optimization of the design is a complex system. The calculation of the internal force and deformation of the complex support system is crital to the safety of an excavation. In this paper, on the basis of relevant literature, the following researches are performed:1,For the large deep excavation in soft soil area, the common types of foundation pit support system are summarized, including the steel sheet pile, deep mixing pile, column piles, diaphragm wall, soil nailing, anchor, reinforced concrete wall and artificial freezing method. Meanwhile, their respective advantages and disadvantages are analyzed. The selection factors of the above type of supporting structure are analyzed, including engineering hydrogeological data, environmental conditions, the relevant construction information etc. For the design of diaphragm wall, additional information abtaining from the experiment should be provided.2,The selection principles of the commonly used deep foundation supporting structure are analyzed. For steel structure, its layout should not be bracing system, and the normal circumstances style should be given priority. When the horizontal distance between adjacent support is large enough, the support at the end of the character should be set; for concrete support, its layout not only be used as the steel support, but the additional style can also be adopted, including:â‘ When the pit plane shape is complex, the diagonal trusses or the composition of the plane support system can be adopted;â‘¡when large flat working space is needed, the composed of trusses and plane symmetric truss support system can be adopted;â‘¢the support system evolved from the above two basic style, such as internal support ring beam form. When the plane shape of a foundation pit is nearly square, circular ring beam can be used; when the pit plane shape is long and narrow, an elliptical beam or ring beam in the form of multi-channel can be used.3,The optimization design principle of the structure of deep excavation is analyzed, wihich including primary selection of support type, analyze, calculation of support structure design and location of support structure.4,The principles of the using of finite element method in foundation pit engineering are analyzed, including the simulation of soil material, supporting structure, the initial stress field, the load caused by excavation.5,Taking a deep foundation pit as an example, the the application process of optimization design method is analyzed.The internal forces and deformation of the support system are calculated by the finite element method. On the basis of the calculation results, the column were piles, bored piles, cement mixing pile are designed.