Research On Deformation Regularity Of The "End-suspended Pile" Support System In Foundation Pit Of CTF Finance Centre

In coastal mountainous and hilly areas,some bedrock outcrop is shallow.When the foundation pit is deep,considering economic and technical factors,the depth of rock-socketed pile body is limited.At this time,a kind of "end-suspended pile" without embedded state can be used for support.Its design and calculation method has not been supported by the corresponding theory,and it is a kind of support method with greater risk,but the existing results have been reported.The example shows that its supporting effect and economic benefit are better.Therefore,the research on the deformation law of this special supporting form becomes particularly important.This paper takes the foundation pit deformation law of the special supporting structure of "end-suspended pile" as the analysis object in the second phase of the foundation pit project of CTF Finance Centre.Firstly,the research status and basic theory of deep foundation pit support technology and deep foundation pit deformation are studied,and the research status and basic calculation theory of the "end-suspended pile" support structure studied in this paper are summarized,and the actual engineering case is analyzed and organized.Relevant data and monitoring data provide the basis for subsequent finite element modeling work.Secondly,MIDAS/GTS NX finite element software is used to simulate the excavation of foundation pit supported by suspended foot piles.Firstly,the sensitivity of three kinds of deformation of foundation pit is analyzed when cohesion,internal friction angle,anchor cableprestress,ground overload,length of supporting pile and diameter of supporting pile are changed by combining single soil finite element model with grey correlation method.The foundation pit excavation model is used to analyze the deformation of the "end-suspended pile" foundation pit under various excavation conditions,summarize its regularity and compare it with the actual monitoring data.Then three main influencing parameters in the design of the "end-suspended pile" support system are analyzed,including rock socketing depth,reserved rock shoulder width and Anchor Cable axial force.Finally,based on the two-dimensional model,the three-dimensional finite element model of the project is established.After the calculation results are obtained,the actual monitoring data is compared with the actual monitoring data.The horizontal displacement of the foundation pit support structure and the surrounding ground settlement are analyzed,and the model is found together.In the monitoring data,the area where the displacement of the foundation pit is excessively large is analyzed,and the cause is analyzed.The concrete reinforcement measures and construction methods are proposed to verify the feasibility of the“end-suspended pile” support system in this project,and verify the constitutive adopted in this paper.The model and parameters can better simulate the deformation trend during the foundation pit excavation process.