Study On The Influence Of Foundation Pit Excavation Deformation On Surrounding Buildings

At present,most of the foundation pit excavation projects are located in the urban areas,which are close to the existing buildings,and the construction site is narrow.The foundation pit project is easy to cause settlement of surrounding soil,thus affecting the safety of surrounding buildings.Therefore,it is very important to ensure the stability and safety of the foundation pit support structure.The factors causing the settlement of surrounding soil in foundation pit engineering are complex and varied,and dewatering in foundation pit excavation is one of the important reasons.In this paper,a foundation pit excavation project in Jinan City(the excavation size of the foundation pit is 50m×50m×17.5m,dewatering to underground-18.5m,20 meters away from the foundation pit,there is a four-storey brick residential building)is taken as the research background,and the influence of dewatering on the settlement of surrounding buildings is studied in depth.The main research contents are as follows:The finite element simulation software GTS NX is used to simulate the dewatering construction process of foundation pit excavation.The monitoring results of actual projects are compared with the settlement calculation values of numerical simulation.The results are in good agreement,which also verifies the feasibility of the dewatering curve obtained in this paper.This paper establishes an integral model of the interaction between dewatering in foundation pit excavation and surrounding building foundations,and studies the influence of dewatering in foundation pit excavation on the settlement of surrounding building foundations under different distances from foundation pit,different floor area,different forms of building foundations(independent foundation under column,raft foundation)and different stiffness of building foundations.The analysis shows that the closer the building foundation is to the foundation pit and the larger the base area is,the larger the settlement of the building foundation is and the more obvious the uneven settlement is;the ability of raft foundation to resist the uneven settlement of foundation is obviously better than that of independent foundation.Under the given conditions in the paper,the uneven settlement of raft foundation is about 50% of that of independent foundation;the larger rigidity of raft foundation is very favorable for adjusting the uneven settlement of foundation.However,when the stiffness of raft foundation increases to a certain value,the effect of increasing the stiffness of raft foundation on resisting uneven settlement is no longer obvious.The whole model of foundation pit dewatering and surrounding four-storey frame structure building is established,and the whole model of foundation pit dewatering and four-storey brick-concrete structure building is established.The influence of foundation pit dewatering on the settlement of surrounding buildings with different structural forms is studied.The whole structure of the frame structure is unevenly settled by "slope type",while the whole structure of the brick-concrete structure is unevenly settled by the "eight-zigzag slope type".The Code for Design of Building Foundation(GB50007-2011)stipulates that the maximum difference of settlement between adjacent columns and foundations is 0.002L(L is the distance between adjacent columns and foundations).Through finite element analysis and calculation,the safety critical curve of dewatering depth(h)of foundation pit and distance(s)between frame structures and foundations is obtained.