Study On Stability Of Foundation Pit Support In Front Beach

With the development of urban coinstruction in our country,due to the shortage of urban land resources,the foundation pit engineering is characterized by "many,big,near and deep".In view of these characteristics,the design of foundation pit engineering from the strength control to deformation control,and with the excavation of the scale of the expansion,the depth increases,more and more stringent requirements on the foundation pit deformation control.There have been a lot of excavation and supporting the construction of the problem.In the soft soil area,because the strength of the soft soil is not high,the deformation is large,and has certain creep,the foundation pit support is often the difficulty in construction.The combination support system of cement-soil mixing bored pile and water-stopping curtain is a new type of supporting structure,which has the advantages of large lateral stiffness and good overall stability.,The pile internal force is small,the deformation control ability and the construction convenient and so on the characteristic,when this system foundation pit digs,the post-pile soil soil has the horizontal and the vertical movement tendency in the foundation pit,because soil's shear strength and pile soil Soil-cement mixing pile has the effect of restraining the soil in the foundation pit.The combined supporting structure of cement-soil mixed pile and cast-in-place pile will produce double-layer soil arching effect,and the cement soil will strengthen the soil between the piles The soil arching effect of cement-soil is more significant than that of the combined soil-retaining structure.The combined support system has been widely used in deep foundation pit and soft soil area.This paper summarizes the common support structure of foundation pit engineering,and summarizes the design theory of each supporting structure,and discusses the mechanism of the combined use of cement-soil mixing pile and bored pile in soft soil foundation pit engineering.On this basis,taking a large foundation pit in Shanghai as an example,the stability calculation and local deformation mechanism of foundation pit are studied.Combined with the actual project,the design calculation of a large foundation pit and the finite element simulation of the local deformation of the foundation pit are put forward,and the corresponding solution and guarantee measures are put forward for the quality points in the construction.This paper can be a reference for the combined support of the bored pile and cement-soil mixing pile foundation in soft soil area.