Analysis Of Pile Foundation In Continuous Medium

In view of the shortcomings of the current study on the interaction between pile and soil under laterally load,this paper studies the load-displacement response of pile foundation in continuous medium by theoretical analysis,formula derivation and numerical simulation methods,focusing on the analytical solution of pile foundation response under laterally load in radial heterogeneous soil and nonlinear soil.The main research is as follows:Firstly,study on analysis of laterally loaded pile foundation in layered soil.The differential governing equation of pile-soil displacement is established based on the variational principle.The soil displacement is obtained by one-dimensional finite difference method,and the pile displacement is obtained by solving boundary condition and continuous condition matrix.Study on the influence of modulus ratio of soil on pile displacement,load distribution and soil displacement.The results show that with the increase of the modulus of the soil layer near the pile top,the displacement of the pile top decreases significantly as well as the maximum bending moment.With the decrease of modulus ratio,the shear stiffness of soil increases,the normal stiffness decreases,the soil resistance provided by shear resistance and compression resistance decreases,and the shear force on pile decreases more slowly with the increase of depth.The radial displacement and tangential displacement of soil attenuate with the increase of radial distance from the pile axis,and the attenuation rate of radial displacement is less than that of tangential displacement.Secondly,analysis of laterally loaded piles in radially multizone soil is studied.The differential equations of pile foundation and soil are established considering that the inner region is divided multizone due to pile installation disturbance.Solutions for disturbed soil and undisturbed soil deflection are obtained by Bessel functions.The displacement of pile is obtained by solving the matrix of pile boundary condition and the continuous of soil layer interface condition.Based on this,the influence of soil softening or hardening and the range of disturbance region on the displacement and load distribution of piles are investigated.The results show that as the disturbance modulus ratio increases,both of the shear stiffness and normal stiffness of soil in the disturbed area increase,conversely,in the undisturbed region they all decrease.When soil around the pile softens,both of the displacement of pile top and the maximum bending moment decrease as the disturbance modulus ratio increases.As the softening area increases,both of the he pile top displacement and the maximum bending moment increase.Then,study on analysis of laterally loaded pile foundation in nonlinear soil.The nonlinear elastic constitutive relation describing the change of shear modulus with strain is adopted.Soil displacement is regarded as the product of separable functions,and the pile-soil displacement differential equation under system equilibrium state is obtained by using the principle of energy.One-dimensional finite difference method can be used to solve the control differential equation of soil displacement,and the analytical solution of pile displacement can be obtained by solving the boundary condition matrix.Through parameter analysis,the influence of pile top stress change on soil joint deviatoric strain and shear modulus and the response of pile displacement,shear force and bending moment in nonlinear soil are obtained.The results show that,as pile top load increases,nonlinear deviatoric strain gradually increases and shear modulus gradually decreases.In addition,the greater the stress on the pile tip,the greater the trend of deviatoric strain increase and the smaller the trend of shear modulus decrease.The displacement and maximum bending moment of pile tip in nonlinear soil are significantly greater than that of homogeneous soil.Finally,analysis of vertical static load and dynamic load on pile in layered soil is studied.By combining the generalized Hamiltonian principle with the variational method,the analytical solution of the vertical dynamic response of a single pile is obtained.The influence of the slenderness ratio,cut-off frequency,pile-soil modulus ratio and dimensionless frequency on the real and imaginary parts of the complex impedance of pile head under vertical dynamic load is analysed.The results show that the real part of the complex impedance decreases and the imaginary part increases with the increase of the ratio of length to width.The cut-off frequency of resonance decreases with the increase of slenderness ratio of the pile.The cutoff frequency is basically constant when the pile-soil modulus ratio changes and the damping ratio increase with the pile-soil modulus ratio.When pile-soil modulus ratio is relatively large,the damping ratio is basically unchanged.