Analysis Of Force And Deformation Characteristics Of Single Pile In Deep Backfilled Soil

With the rapid development of national construction industry and the rise of infrastructure construction,there are many recent thick fill projects.The most obvious feature of the recent thick fill engineering is that the fill is heavy,and the self compression settlement and foundation settlement of the fill caused by the self weight stress of the fill are large.The pile foundation located in the newly thick fill site will produce considerable negative friction due to the self compression settlement of the filling body,and the deep backfill has a certain time effect.If the design or construction is improper,it will cause significant economic losses and casualties in the future use of the construction pile foundation.Therefore,it is of great significance to study the pile foundation characteristics in the deep backfill.In this paper,combined with the actual monitoring of Juteng international Neijiang base phase I project,the influence of negative friction on pile foundation engineering properties of the newly deep fill site is analyzed by means of theoretical analysis and numerical simulation.The main work is as follows:(1)Combined with the field test and monitoring data of the pile foundation project in the first phase of Ju Teng Nei Jiang base,this paper sums up the change rule of the pile body stress and deformation,neutral point position and negative friction resistance when there is deep backfill in the construction process,and analyzes the characteristics of negative friction resistance of pile foundation and its influence on pile foundation.(2)Combined with the finite element software MIDAS/GTS,the three-dimensional finite element model of pile-soil interaction is established,and the reasonable soil model parameters,material parameters and contact parameters are selected to analyze the changes of single pile behavior in deep backfill.By comparing the calculation results of the benchmark model with the actual monitoring data,the reliability of the calculation results of the benchmark model is verified.(3)On the basis of the above model,the influence of elastic modulus of soil at pile tip,vertical load at pile top and thickness of backfill on the performance of friction,axial force,neutral point position and settlement of single pile is considered respectively.(4)According to the variation law of negative friction of single pile in deep backfill under different conditions,some engineering measures to reduce the negative friction effect of single pile are put forward to guide the design and construction.