Study On Analytical Model And Approach For Vibration Of Heterogeneous Soil-Pile Coupled System

Pile foundations are widely used in various large-scale engineering construction,such as offshore wind turbines,bridges and high-rise structures,due to their high bearing capacity and convenient construction.However,during the construction process,due to the influence of soil compaction,relaxation and other disturbance factors,there exist a certain inhomogeneity along the radial direction of pile foundation,i.e.,radial heterogeneity effect.In pile foundation dynamic analysis,the accurate description of the coupled interaction between soil and pile has always been a focal point and difficulty in the dynamics research of pile foundations.Despite the significant research efforts made by scholars over the past few decades,there still exist limitations and deficiencies in the theoretical study of heterogeneous soil-pile coupled interaction,owing to the complexity of these problems.In light of this,this paper will systematically and comprehensively study the vibration problem of heterogeneous soil-pile coupled system under different loads by means of analytical method.The main work is as follows:(1)Based on the three-dimensional continuum theory,the Rayleigh-Love rod model is adpoted to consider the transverse inertia effect of pile shaft,and a new analytical model of coupled longitudinal vibration of radial heterogeneous viscous damping soil-large diameter pipe pile is established.The analytical expressions of the frequency domain response of surrounding and inner soil are obtained by using the Laplace transformation method and complex stiffness transfer method,and the new analytical solution of the dynamic impedance of large diameter pipe pile is derived by combining the pile-soil coupled continuous condition.Then,the semi-analytical solution of time domain response of large diameter pipe pile is derived by using the Fourier inverse transform and convolution theorem.On this basis,the derived solution is degenerated and compared with the existing related solutions to verify its rationality and accuracy in many aspects.Furthermore,the influence of pile parameters and construction disturbance effect of surrounding soil on the longitudinal vibration characteristics of of large diameter pipe pile is further discussed by parametric analysis.(2)Based on the proposed radial heterogeneous viscoelastic damping soil-large diameter pipe pile model,a new analytical model of coupled longitudinal vibration of longitudinal and radial heterogeneous soil-large diameter defective pipe pile is established by further considering the longitudinal stratification of surrounding soil and the defects of pile shaft.Then,the new analytical solutions of dynamic impedance and dynamic response of large diameter defective pipe pile are derived by using the variable separation method,impedance transfer function method and Fourier inverse transform.On this basis,the derived solution is degenerated and compared with the existing related solutions to verify its rationality and accuracy in many aspects.Furthermore,the influence of pile defects,longitudinal and radial heterogeneity of surrounding soil on the longitudinal vibration characteristics of large diameter defective pipe pile is discussed by parametric analysis.(3)Based on Biot’s dynamic wave theory,the existing heterogeneous single-phase soil-pile horizontal dynamic interaction model is improved,and an new analytical model of coupled horizontal vibration of radial heterogeneous saturated soil-solid pile is established by further considering the fluid-solid coupling and construction disturbance effect of saturated soil.The analytical expression of the frequency domain response of the saturated surrounding soil is obtained by using the Helmhotz potential function,Laplace transform and variable separation methods.Then,the new analytical solutions of the dynamic response of solid pile is derived by means of the continuous condition on the pile-soil interface.On this basis,the derived solution is degenerated and compared with the existing related solutions to verify its rationality and accuracy in many aspects.Furthermore,the influence of radial heterogeneity of saturated soil on the horizontal vibration characteristics of solid pile is further discussed by parametric analysis.(4)Based on the proposed radial heterogeneous saturated soil-straight cylindrical pile model,a new analytical model of coupled horizontal vibration of radial heterogeneous saturated soil-wedge-shaped pile is established by considering the special-shaped effect of the wedge pile,and the new analytical solutions of horizontal dynamic response of wedge-shaped pile in radial heterogeneous saturated soil is derived by using the potential function method and transfer matrix method.On this basis,the derived solution is degenerated and compared with the existing related solutions to verify its rationality and accuracy in many aspects.Furthermore,the influence of pile parameters and construction disturbance effect on the horizontal vibration characteristics of wedge-shaped pile is further discussed by parametric analysis.(5)Based on the proposed horizontal vibration analytical model of radially heterogeneous saturated soil-solid pile,a new analytical model of surrounding soil-pipe pile-inner soil coupled horizontal vibration is established by further considering the influence of inner soil.The analytical expressions of frequency domain response of surrounding and inner saturated soil are derived by Laplace transform and variable separation method.Then,the new analytical solutions of the dynamic response of the pipe pile are derived by using the boundary continuity condition.On this basis,the derived solution is degenerated and compared with the existing related solutions to verify its rationality and accuracy in many aspects.Furthermore,the influence of pile parameters,surrounding and inner soil on the horizontal vibration characteristics of pipe pile is further discussed by parametric analysis.(6)Based on the existing theoretical model of fully embedded pipe pile group in homogeneous saturated soil,a new analytical model of horizontal vibration of partially embedded pipe pile group in saturated layered soil is established by taking into account the complex working conditions of the heterogeneity of saturated soil and partially embedded pipe pile exposed section.The corresponding pipe pile-pipe pile dynamic interaction factor and the new analytical solutions of dynamic response of partially embedded pipe pile group are derived by applying operator decomposition theory,transfer matrix method and superposition principle.On this basis,the derived solution is degenerated and compared with the existing relevant solutions to verify its rationality and accuracy in many aspects.Further,the influence of pile spacing,embedment ratio,layered soil properties and soil plug effect on the horizontal vibration characteristics of partially embedded pipe pile group is discussed by parametric analysis.The proposed analytical models and the corresponding analytical solutions are developed for the vibration problem of the heterogeneous soil-pile coupled system.This research can systematically and comprehensively reveal the mechanism of pile foundation vibration in complex foundation environments.The relevant results and conclusions of this study can provide a valuable reference and guidance for pile foundation anti-vibration measures,anti-vibration design,and pile dynamic testing technology.