Effect And Optimization Analysis Of Pile Anchor Support Of A Foundation Pit In Xi’an

In foundation pit engineering,it is an important research content of foundation pit engineering to select an economic and reasonable foundation pit support structure combination and continuously optimize the support structure design.Aiming at the optimization of pile anchor support in foundation pit,this paper adopts the numerical simulation method,calculates and optimizes the typical pile anchor support system of the foundation pit by using FLAC3D finite difference calculation software,analyzes the influence of the changes of pile length,pile diameter,pile spacing and prestressed anchor cable parameters on the stability of foundation pit,and optimizes the more stable and economic support effect.The specific research is as follows:1.Based on the case of a deep foundation pit project in Xi’an,combined with the field investigation report,analyze the soil layer information,and finally select the form of pile anchor support structure according to the characteristics of the foundation pit.Combined with Lizheng deep foundation pit design software,the support structure of section 3-4 in the west of the foundation pit is checked,the deformation of the support structure of section 3-4 is obtained,the field monitoring data are sorted out,and the deformation law is found.2.FLAC3D software is used for modeling and finite element simulation to analyze the soil displacement,surrounding soil settlement,support pile displacement and Anchor Cable axial force in the foundation pit excavation stage.It is found that the horizontal displacement of the supporting pile and the settlement around the ground increase with the excavation.After the excavation and support construction,the maximum displacement of the pile top is 8.47mm,the maximum displacement of the side wall of the foundation pit in the horizontal direction is 9.83mm,and the maximum settlement of the foundation pit is 4.84mm.It is found that the numerical simulation value is slightly lower than the original design value,and the accuracy of the numerical simulation value is slightly lower than that of the original design value.3.Based on the original design scheme,the pile anchor support model of foundation pit is established for single factor analysis.The influence of changing pile length,pile diameter,pile spacing and prestressed anchor cable inclination on the deformation of support structure is studied by controlling variable method.12 groups of parameters are selected for optimization by orthogonal test method,and the final optimization scheme is obtained.The optimization analysis results are as follows:changing pile length and pile spacing has little influence on the deformation of foundation pit;The prestress of anchor cable and pile diameter have great influence on the deformation of foundation pit.The optimal parameters are as follows:the optimal pile length is 18m;The optimum pile diameter is 0.8m;The optimum pile spacing is 1.6m;The optimum prestress size is 170kN.Compared with the original scheme,the maximum deformation of the pile top and the pile body in the optimized scheme are reduced by 2.35mm and 2.57mm,and the surface settlement around the foundation pit in the optimized scheme is reduced by 1.69mm.4.Based on the above analysis results,Compared with the original scheme,the result is more stable and the cost is lower.Finally,the whole foundation pit is optimized to reduce the engineering cost,and provides optimization ways and methods for similar pile anchor support projects.