Study On The Influence Of Foundation Pit Excavation On Deformation Of Adjacent Residential Buildings

With the large-scale construction of urban engineering,more and more foundation pit projects are set up near buildings,and being too close can cause safety hazards to buildings.The excavation of a foundation pit will have an impact on adjacent buildings,mainly because the excavation and unloading of soil in deep foundation pit engineering can cause displacement and deformation of the soil,thereby causing deformation of adjacent buildings.Once deformed,it can lead to cracks or tilting of the building,reaching a certain degree and even causing the building to collapse.Therefore,ensuring the safety of adjacent buildings during excavation of foundation pits is of great significance.This article takes a deep foundation pit project of a nearby residential building in Zhengzhou City as an example.Under the combined support method of upper soil nail wall and lower pile anchor support,FLAC3 D is used to numerically simulate the excavation process of the foundation pit.The deformation effect of the foundation pit excavation on adjacent buildings is studied,and the following content is obtained:(1)Summarized the research status of domestic and foreign scholars on foundation pit engineering,and studied the deformation theory of foundation pits and adjacent buildings.(2)Using FLAC3 D software,a model was established for a deep excavation project in Zhengzhou,and numerical simulation was conducted to analyze the internal forces of soil nails and prestressed anchor cables.The internal forces of soil nails showed a trend of being larger in the middle and smaller at both ends under tensile force;The prestressed anchor cable is subjected to tensile force,and the maximum internal force appears at the fixed end,gradually decreasing,and sharply decreasing at the junction of the free end and the anchoring section.(3)We studied the vertical and horizontal displacement of the soil around the foundation pit under 7 working conditions: the uplift value at the bottom of the foundation pit increases with the increase of the excavation depth,with a maximum uplift value of 19.32mm;The settlement value of the outer surface of the foundation pit increases with the depth of the foundation pit,and gradually decreases with the distance from the edge of the foundation pit.The maximum settlement value is 20.54 mm at the edge of the foundation pit;The horizontal displacement of deep soil continuously increases with the increase of excavation depth of the foundation pit,showing a parabolic trend of first increasing and then decreasing.The maximum horizontal displacement is 19.37 mm at a depth of 3m in the soil.The correctness of the established model was verified by comparing the simulated values with the measured values.(4)Under 7 working conditions,the horizontal and vertical displacement of adjacent buildings increase with the deepening of excavation of the foundation pit.The maximum horizontal displacement at the bottom of the building is located at monitoring point 6(closest to the foundation pit),which is 2.785 mm,and the maximum settlement value is located at monitoring point 6,which is 9.184mm;The vertical displacement of adjacent buildings decreases as the distance from the edge of the foundation pit increases.After condition 7 is completed,the maximum settlement value is 9.184 mm at monitoring point 6,and the minimum settlement value is 2.005 mm at monitoring point 9(the farthest distance from the building to the foundation pit).The measured values of horizontal and vertical displacement of the building are both smaller than the simulated values.Under all operating conditions,the maximum tilt values are 0.239 ‰.(5)According to the degree of impact of foundation pit construction on the surrounding environment,the surrounding area of the foundation pit is divided into main impact area,secondary impact area,and possible impact area.This building is located in the secondary impact area of foundation pit excavation,and protective measures are proposed during the construction process.