Study On The Application Of Oversized Prestressed Concrete Square Pile In Soft Soil Foundation Pit

In recent years,with the continuous improvement of production technology,there is an increasing number of the prestressed concrete piles' outputs in China.Amomg these piles,prestressed concrete square piles are widely used in bridge engineering,road engineering,slope engineering,port and waterway engineering and hydraulic engineering because of its high bearing capacity,high efficiency of construction,short construction periods,strong penetration in soil,convinient for transportation and environmental protection.However,oversized prestressed concrete square piles are seldom applied in the foundation pit engineering.Based upon a soft soil foundation pit in Lianyungang City,the reinforcement mechanism of oversized prestressed concrete square piles in soft soil foundation pit is discussed by theoretical study,analysis of field monitoring and numerical simulation.The main research contents are as follows:(1)Prestressed concrete square piles' application at home and abroad are summed up,the structure characteristics of oversized prestressed concrete square piles are systematically analyzed.Besides,the soil pressure theory,the checking computations and the calculation method of prestressed concrete square pile's internal force and deformation as supporting structure are studied.(2)The installation method of the oversized prestressed concrete square pile in the soft soil foundation pit is concluded,the field monitoring data is used to analyze the stability of the foundation pit and the environment surrounded.(3)The finite element software Plaxis 3D is utilized to simulate a part of the deep foundation pit.The changes related to horizontal displacement,bending moment of the oversized prestressed concrete square piles and surface subsidence outside the foundation pit during the excavation are researched;the numerical simulation results are also compared with the field monitoring data.(4)The main factors affecting the oversized prestressed concrete square piles' supporting performance are studied,including surcharge near the foundation pit,pile spacing,the length of piles,the stiffness of piles and the stiffness of steel supports.Finally,the recommended measures for controlling the soft soil foundation's deformation are put forward.The research in this paper provides reference for the design and construction of oversized prestressed concrete square piles in soft soil foundation pit and has certain practical value.