Study On Settlement Characteristics And Prediction Methods Of Pipe Pile-supported Composite Foundation Of Passenger Dedicated Line

Pipe pile-supported composite foundation is a new technique for foundation treatment in recent years.It has a variety of advantages in controling total settlement,differential settlement and low cost.Moreover,it is especially suitable for treating the deep soft soil area.So based on the study of pipe pile-supported composite foundation of a passenger dedicated line along the southeast coast,the paper adopted analysis of the measured settlement datas,FLAC3D numerical analysis,settlement calculation and prediction methods to study the settlement regularity,settlement calculation and prediction theory of pipe pile-supported composite foundation in super-vast and deep soft soil area.The main contents and conclusions are as follows:(1)Through analyzing the measured settlement datas of typical section,the regularity of surface settlement and lamination settlement of pipe pile-supported composite foundation is researched.(2)Based on typical section,the paper established three dimensional models of actual foundation treatment condition using FLAC3D,then systemically analyze the regularity of axial force,skin friction,strain of geogrid,position of neutral point,total settlement and lamination settlement as embankment filling.(3)Influence factors for roadbed settlement and lamination settlement including pile spacing,pile cap dimension,elastic modulus of pile and cushion,tensile stiffness of geogrid,and angle of internal friction of embankment fill are systemically analyzed using numerical simulation.(4)According to a series of hypotheses of the distribution of skin friction and the relative displacement between soil and pile,the paper study the settlement calculation method of pipe pile-supported composite foundation considering the co-action of pile,cushion,and the soil.Then apply this settlement calculation method to typical section.The result shows that the synergistic settlement calculation method has higher accuracy than traditional settlement calculation methods.(5)Using the fitting functions come with origin or the user-defined fitting function in origin,various parameters of fitting curve and grey system model are solved quickly.Then apply support vector machine method to settlement prediction of pipe pile-supported composite foundation.Moreover,based on unequal interval GM(1,1)model,some improvements were made.(6)Take typical section as an example,based on the measured settlement datas,the paper apply fitting curve method,grey system theory method and support vector machine method to settlement prediction of pipe pile-supported composite foundation,and contrast the prediction results of various methods.Then compare the prediction results with the numerical simulation result and analytical calculation results,so that the whole theory of settlement of pipe pile-supported composite foundation is systematically analyzed and evaluated.