Analysis Of The Influence Of Deep Foundation Pit Excavation On Adjacent Shallow Foundation Buildings

With the development of the city,the demand for land is increasing,which leads to the higher cost of urban land.A large number of buildings seek higher or underground space,which puts forward more strict requirements for underground structure.Foundation pit engineering has always been concerned about its complexity and danger.It is of great significance for us to know the impact of foundation pit excavation on relevant structures and surrounding environment in advance to make plans to avoid risks.In this paper,based on the foundation pit of Nanning metro station,the three-dimensional numerical simulation of the excavation of the foundation pit is carried out by using the PLAXIS finite element software.The displacement of retaining structure,ground settlement and building settlement caused by foundation pit excavation are analyzed.The finite element model is verified by monitoring data.The relevant factors affecting deformation and building settlement are analyzed by using the verified finite element model.Based on the existing soil settlement formula,the settlement formula is improved to improve the settlement of shallow foundation buildings around the foundation pit Line forecast.The main conclusions are as follows:(1)In the process of foundation pit excavation,the depth of the maximum displacement of pile gradually moves down with the increase of excavation depth,and gradually stabilizes near 2 / 3H.The maximum ground settlement occurs near 15 m away from the foundation pit rather than the side of the foundation pit.The overall settlement value of the building is less than the settlement value of the soil.(2)The three-dimensional finite element numerical model of foundation pit excavation is established by using the PLAXIS software.The displacement of retaining structure,surface settlement and surrounding building settlement are analyzed,and the displacement change law is obtained.The comparison analysis is made with the actual monitoring data.The results of finite element and field monitoring are consistent,and the results of finite element have certain accuracy.(3)According to the finite element model,the pile length,pile diameter,internal support stiffness,building load and excavation depth are analyzed.Through analysis,it is found that with the increase of excavation depth,the increase of building settlement value is very large.In different excavation stages,the maximum increase of settlement reaches 97.1%.In this model,when the building load increases to 4 floors,the building starts to destroy.It can be seen that the building load and excavation depth have a great influence on the building settlement.(4)Based on the existing settlement prediction formula and deformation law of soil,the settlement of buildings with different load types is calculated,and a simple settlement prediction formula of shallow foundation is given.After verification,the settlement prediction formula has certain accuracy,which can provide reference for future construction.