Study On The Influence Of A Deep Foundation Pit Excavation On The Displacement Characteristics Of Adjacent Buildings In Xi’an

With the continuous development of urban construction,the available land area is decreasing.The disturbance of foundation pit excavation to the surrounding environment will inevitably be encountered in the reconstruction and expansion of new high-rise buildings or old buildings.To ensure the safety and quality of the project and improve the construction efficiency is the main program of the actual project.Based on a pile anchor deep foundation pit project in Xi’an,this paper uses MIDAS/GTS finite element software to establish a three-dimensional model to simulate and analyze the influence of foundation pit excavation process on the deformation and stress characteristics of adjacent buildings.In the process of pile anchored foundation pit excavation,the influence of anchor cable prestress,pile diameter and pile length on the deformation of foundation pit support structure and existing building foundation is analyzed.The stress and deformation law of new foundation pit support structure and existing building foundation are studied when the distance between adjacent buildings and foundation pit,the number of building floors and foundation form change.The main research contents are as follows:(1)The numerical simulation analysis of a deep foundation pit excavation project in Xi’an is carried out,the three-dimensional models of the new foundation pit and different adjacent foundation buildings are established,the deformation and internal force characteristics of the foundation pit support structure in the process of foundation pit excavation are analyzed,the influence of the pit angle effect on the deformation of adjacent buildings is studied,the deformation and internal force distribution characteristics of the superstructure of different foundation buildings are analyzed,and the location of tensile cracking of the building wall is predicted,Combined with the monitoring data of the construction site,the reliability of the numerical results is verified.(2)Taking anchor cable prestress F,support pile diameter D and pile length L as numerical test variables respectively,the stress and deformation law of deep foundation pit excavation on foundation pit support and building foundation is studied when the support parameters change,and the reasonable value range of support parameters is put forward.Considering the difficulties of anchor cable construction,the anchor cable exceeding the land red line and invading into the boundary of other underground structures,The feasibility of replacing pile anchor support with double row pile support is studied.(3)Taking the distance between building and foundation pit and building load as variables,the influence law of deep foundation pit excavation on the displacement and internal force of foundation pit support structure and the settlement of adjacent existing buildings are studied.The deformation law of building foundation and superstructure of frame structure buildings with different foundation forms after being disturbed by deep foundation pit excavation is studied,and the control effect of grouting reinforcement depth on uneven settlement of building foundation is analyzed.(4)According to the analysis results,the design and construction suggestions for similar pile anchor deep foundation pit projects in Xi’an are put forward.