Study On The Spatial Effect Of Deep Foundation Pit In Flushing Flood-accumulated Adhesive Land Layer Based On Deformation Control

In order to alleviate the pressure of urban traffic,China’s subway industry has developed rapidly.The deep foundation pit project of subway stations is a high-risk project.Its safety and impact on the surrounding environment are increasingly valued by people.The stress and deformation of the supporting structures of each part of the subway foundation pit affect each other.There are obvious spatial effects in the excavation of the foundation pit.How to effectively use the spatial effects of the foundation pit to control the deformation of the foundation pit requires research on the spatial effect characteristics of the foundation pit.On the basis of summarizing the current research situation at home and abroad,this paper carried out theoretical analysis,engineering measurement and three-dimensional finite element analysis based on the example of Wansheng North Street Station of Jinan City Rail Transit R2 Phase I civil engineering.(1)This paper analyzes the engineering mechanical properties of clay soil,forms and laws of spatial effect of foundation pit are studied,and the calculation formula of non-extreme active soil pressure of clay soil is studied by horizontal strip method.The effect of spatial effect coefficient k on the deformation of retaining structure is analyzed by the basic flexure equation of supporting structure.It is found that the displacement and bending moment of supporting structure are about k times the displacement and bending moment of supporting structure outside the space effect area.(2)The principle of deformation process control in foundation pit construction is analyzed,and the application of process control in deep foundation pit deformation control is discussed.based on the actual engineering background,the deformation control value of foundation pit is determined according to the requirements of surrounding environment,and the total deformation control value is assigned to each construction step sequence.the deformation step control value of foundation pit is set up.the deformation of foundation pit should be monitored and strictly controlled during construction.(3)It is found that with the increase of over-excavation depth,the erection time of the third support has a great influence on the deformation of the retaining structure,so it is morebeneficial to the deformation of the foundation pit to reduce the position of the second support.