Design Calculation And Numerical Simulation Analysis Of Supporting Structure Of Deep Foundation Pit With Pile-anchor And Double-row Piles

This paper summarizes the characteristics and research status of deep foundation pit support and introduces the selection principle of common support structure.The supporting design of the deep Foundation pit is designed with the background of a deep foundation pit support project in Xiangtan.The feasibility of the support scheme is verified by numerical simulation,and the influence of the influencing factors on the supporting performance of the selected retaining structure is analyzed.First,through the investigation and analysis of the foundation pit,combined with the relevant theoretical knowledge,the foundation Pit support scheme was preliminarily determined.It is decided that single row pile,double row pile and pile anchor structure should be chosen as the supporting structure of the deep Foundation pit.The soft soil layer was strengthened and the water-stopping measures were determined.It was decided to strengthen the soft soil layer and determine the water stop measures.The BC segment foundation pit pile anchor support structure and DC segment foundation pit double row pile structure of the deep foundation pit support project are designed in detail by using F-SPW.And verify that the stability of the supporting structure meets the support requirements.Then using FLAC3 D to simulate and analyze the stress and deformation of soil and supporting structures during the excavation and support process of foundation pit.Change the design parameters of pile-anchor structure and double-row pile structure,and analyze its influence on the stress and deformation of the supporting structure.These results will be helpful to the optimization design of deep foundation pit engineering.The main conclusions are as follows:1.Based on the comprehensive analysis,the structure of pile-anchor and double-row piles were selected as the supporting structure of the BC and DC segments.Using F-SPW to design the supporting scheme in detail,and verify the stability of the design support structure conforms to the relevant requirements.2.Analysis of displacement image of soil mass and deformation characteristics of supporting structure,and draw the corresponding internal force and deformation curve.The simulation results verify the rationality of the design scheme and parameters,and show a significant spatial effect.The displacement of the midpoint of the long side of the foundation pit is significantly larger than the displacement of the short side.When excavation to the silt soil layer,the soil layer shows a large horizontal displacement.In the actual project can take the corresponding enhancement measures to prevent local instability.3.There are certain optimization spaces for both support structures.For pile anchor support structure.The change of prestress has a great influence on the pile anchor structure,and the prestress of the bolt can be appropriately increased to obtain better support effect.Reducing pile diameter and pile length within a reasonable range is conducive to optimization of project cost.For double row pile support structure.Increasing the pile diameter can effectively reduce the maximum horizontal displacement of the double-row pile,but the bending moment of the pile body will increase accordingly,which has higher requirements for reinforcement.If the row spacing of double-row piles is too large or too small,the support effect will be affected,it should be set in a reasonable range to exert its best effect.