| Based on the foundation pit project of F1 District residential project in Guangzhou Asian Games City,this paper analyzed the selection process and monitoring results of the foundation pit project,and used the finite element analysis software Midas GTS to carry out the overall and local three-dimensional numerical simulation.The calculated deformation,internal force and monitoring data were compared to verify the reliability of the numerical simulation method.Then,the influence scope of the junction point of pile-supported pile-anchor structure,the influence of the design parameters of Pile-anchor support structure and the influence of the design parameters of pile-supported structure are emphatically analyzed,which can provide reference for the design of foundation pit support with similar characteristics as this foundation pit project.The main work is as follows:(1)The shape,mechanism and influencing factors of deep foundation pit deformation are analyzed.Influencing factors include surrounding environmental factors,design factors and construction factors,design factors need to be considered in this paper.(2)The selection principle of foundation pit supporting structure is explained,and the characteristics of the foundation pit project are analyzed.The selection idea of the foundation pit project is expounded.According to the site geological conditions,the depth,area and surrounding environment of the foundation pit,the suitable supporting form for the foundation pit project is determined.The monitoring results of the foundation pit project are analyzed,including settlement monitoring,horizontal displacement monitoring of supporting piles,internal force monitoring of anchor cables and water level monitoring.(3)The whole three-dimensional finite element model is established to simulate the excavation process of foundation pit.The displacement of supporting structure,the displacement of single supporting pile,the stress of supporting structure,the bending moment of single supporting pile and the axial force of anchor cable under various working conditions are obtained.Then the deformation and the influence range at the junction of pile-supported pile-anchor composite supporting structure are compared and analyzed with the monitoring data.It is concluded that the arrangement of angle braces will reduce the displacement of Pile-anchor support structure,and the influence range is about 40 m.And the most reduced position is not just at the junction of pile-supported piles and anchors,but about 7.5m away from the junction.(4)According to the scope of influence obtained in the previous chapter,a corner of the foundation pit including pile brace and pile anchor is taken out,and a local three-dimensional finite element model is established to analyze the influence of the angle of anchor cable,the length of anchor cable,the horizontal spacing of anchor cable,the vertical spacing of anchor cable,the horizontal spacing of support and the vertical spacing of support on the displacement and internal force of the supporting structure at the interface of pile brace and pile anchor.Come to conclusion:Increasing the length of anchor cable,reducing the horizontal spacing of anchor cable,reducing the vertical spacing of support and increasing the stiffness of support are beneficial to controlling the displacement of support structure.The angle of anchor cable,the vertical spacing of anchor cable and the vertical spacing of support need to be analyzed in detail. |
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