Study On The Influence Of Foundation Pit Excavation On The Building Safety Status Of Adjacent Shallow Foundation

In the building of intensive areas of conduct of the pit excavation construction,often induces deformation of adjacent building foundation and superstructure by the influence factors of the pit excavation precipitation and deformation of supporting structure.When the deformation value exceeds a certain limit,the safety status of the building will be adversely affected.Therefore,based on the engineering practice and predecessors’ studying results,with the aid of finite element simulation analysis method,this paper studied and analyzed the deformation of the foundation and its adjacent buildings,change of building safety status and the effect of protective measures for three different buildings in the process of foundation pit excavation.(1)Analysis on foundation pit excavation inducing deformation of surrounding soil and building foundation.Based on the actual situation,the finite element simulation model is established.The influence of the horizontal displacement and vertical displacement on surrounding soil and building foundation are simulated by factors of the change of soil property,ground water level change,foundation pit excavation depth,the distance of the construction of foundation pit and foundation pit supporting forms.It is found that the above factors will influence the displacement of the surrounding soil and building foundation.From the factors impact on the deformation of surrounding soil and building foundation,the greatest effect is the construction of foundation pit of distance,the influence of other factors are in turn the excavation depth,length of supporting,supporting stiffness,underground water level and localized parameters.Comparing with the lateral deformation and vertical deformation of the surrounding soil and building foundation,the vertical deformation is significantly larger than the lateral deformation,and it is about two to four times the lateral deformation.(2)Analysis on the impact of basic deformation on building safety.Based on the actual building,the structure simulation analysis model is established.When the deformation of the building’s foundation as a load reaction to the building structure,the response of the slope of building foundation and building inclination,structural stress and crack width are studied.At the same time,these indicators are compared with the safety identification standard,construction tilt are greatly influenced by the excavation,and the underlying structures of crack changes significantly greater than other layers are found in the process of excavation.When the tilting rate of the building foundation is0.0015,the slope of building foundation and building inclination,structural stress andcrack width meet the standard requirements.(3)Analysis of adjacent building protection measures during excavation of foundation pit.Based on the actual situation of the adjacent project,the finite element simulation analysis model of the three kinds of protection measures of the optimized supporting structure system,adding the partition wall and installing the anti-slide pile in the bottom of the pit are respectively established.The protective effects of various protective measures on the deformation of buildings during excavation of foundation pit are systematically analyzed.It is found that all three kinds of protective measures can reduce the effect of excavation on adjacent buildings under suitable working conditions.However,there are some differences in the overall deformation and settlement of the buildings,among which the optimization of the support structure system can minimize the overall deformation of the building.The partition wall helped to reduce the amount of differential settlement basis.When the partition wall is set in the middle position of the building and the foundation pit,and the height ratio of the underground continuous wall and the partition wall is 2 to 2.5,the protective effect is best.The overall settlement and differential settlement of the building can be reduced synchronously with installing the anti-slide pile at the bottom of the pit.