Study On The Influence Of Adjacent Buildings On The Stress And Deformation Of Foundation Pit Pile Anchor Support

With the rapid development of urbanization,the construction land in city is becoming more scarce.It's common to see that a lot of adjacent buildings close to foundation pit slope next to the pit under construction in the project.In the process of foundation pit excavation constantly,adjacent buildings will be affected,leading to building sinking or cracking phenomenon.At the same time,the retaining structure of foundation pit is influenced by the neighboring buildings.On the one hand,semi-infinite soil on the side of foundation pit will become limited soils due to the basement of adjacent buildings,underground parking and pile foundation,which influence the size and distribution of earth pressure,on the other hand,adjacent buildings is a load at the side of foundation pit.which is equivalent to the order of magnitude larger weight are loaded next to the foundation pit.This king of situation will cause hidden trouble to the safety of the foundation pit engineering.Thus,we should attach importance to research in this area.The current research about influence of adjacent buildings on foundation pit supporting structure was less,and the study had practical significance for engineering.Thus,in this paper,the finite element method as a tool was used,foundation pit engineering of 3#,4#high-rise buildings and underground garage in xi 'an university of technology was set.The author studied changes of the supporting system under different working conditions by referring literature about the finite soil earth pressure theory,citing the finite earth pressure theory of Zheng Beibei in Zhejiang University,using finite element software for geotechnical engineering Midas GTS NX to simulate finite element,and collecting some of the actual monitoring data.The main results are as follows:(1)In the working condition,the pile top had the maximum horizontal displacement and pile displacement value along the depth direction was decreasing.In the following three conditions,the displacement curve of pile body first increased and the decreased from pile top.It is that no anchor was set at the initial stage of excavation,the displacement of the pile was occurred under the action of earth pressure,the pile top has been significantly constrained by providing anchor rod in the second condition.(2)In the process of excavation,the axial force of bolt first increased and then decreased gradually from the anchor head,which reduced close to zero on the anchorage section.The maximum value was near the anchor head.We speculated that the axial force of bolt was transferred through the free segment to the anchored section,and then to the mortar,at last to the layer by the bond strength between mortar and surrounding soil.(3)The two finite element models of excavation were established by the finite element software,one was the actual situation(with adjacent buildings)model,the other was a model of non-adjacent buildings.By comparing the differences of supporting structure in the two models during the process of foundation pit excavation,the author found that the value of the first model was bigger than the second.It is indicated that the adjacent building is not conducive to the excavation of foundation pit..(4)It was safe to design retaining structure by using limited soil pressure of soil with reference,by contracting and analyzing the earth pressure value in the actual monitoring,model,limited soils and classic formula,but some waste will be produced.There were security risks if the classical earth pressure theory was still used to design foundation pit support.