Study On Vertical Vibration Theory Of Floating Pile Considering Three-Dimensional Wave Effect

Studying the vibration characteristic of pile-soil dynamic interaction system which is the theoretical basis for the anti-vibration design of pile and various dynamic testing techniques has attracted wide-ranging attention in the field of civil engineering.Over the past decades,many researchers have made significant improvements for corresponding theory continuously and acquired extensive research achievements.However,there exist many limitations and deficiencies in the studying and application of the basic theory for the floating pile and soil vertical dynamic interaction system.Therefore,this paper presented a visco-elastic supported three-dimensional continuum pile model and a fictitious saturated soil pile model,respectively,to investigate the vertical vibration characteristics of floating pile.The effects of three-dimensional wave propagation for pile,the boundary conditions beneath pile toe,the porous characteristics and wave propagation within the soil beneath pile toe on the dynamic response of floating pile are investigated systematically by applying analytical methods.Then,the semi-analytical solution of pile with defect in vertical heterogeneous saturated soil derived in this paper is applied to establish the knowledge-based framework and develop evaluation executable program for pile integrity evaluation.The principal work is as follows:(1)The mechanical model for a large diameter floating pile is established by taking into account the three-dimensional wave propagation effect of pile and soil,where the boundary condition beneath pile adopts visco-elastic supporting.The analytical solutions of dynamic response at pile head are derived and verified by comparison with existing solutions.Furthermore,numerical examples are performed to investigate the effect of the three-dimensional wave propagation of pile,the boundary conditions beneath pile,the parameters of pile,and soil on the dynamic response of floating pile.It is shown that the proposed three-dimensional continuum model for pile and corresponding analytical solutions have a more wide-ranging application for the vertical vibration problems of large diameter floating pile.(2)The vertical vibration analytical model for large diameter floating pipe pile is proposed and built by considering the three-dimensional wave propagation effect,where the outer soil,pipe pile,and inner soil are considered as a whole.The corresponding analytical solutions of pile dynamic response are achieved by using analytical methods.The rationality and advancement of the proposed model and relevant analytical solutions are stated by comparison with existing solutions.(3)A more rigorous analytical model,named fictitious saturated soil pile model,is proposed to investigate the vibration problems for floating pile in saturated porous media.The dynamic propagation equations for three-dimensional saturated soil are decoupled by introducing potential functions.The solutions for displacement of saturated soil are derived by applying operator decomposition theory.Then,the analytical solutions for dynamic response of pile are achieved by combining the boundary conditions and coupling conditions of pile and soil.On this basis,the influence of porous characteristics and wave propagation effect of saturated soil beneath pile on the dynamic response of pile are investigated.It is indicated that,when the saturation of soil beneath pile is obvious and the drainage is poor,ignoring the effect of pore water within the soil skeleton will underestimate the resonance frequency of dynamic impedance of pile.Furthermore,the velocity response at the pile head achieved by proposed fictitious saturated soil pile model can provide theoretical guidance for the detecting of the thickness of saturated soil beneath pile.(4)By means of the same procedure that presented in fictitious saturated soil pile model within homogeneous saturated soil,the analytical solutions for dynamic response of pile with defect in vertical heterogeneous saturated soil are derived by applying the transfer method of impedance function.The reliability and rationality of the proposed model and relevant solutions are verified by comparisons with both the existing model and practical engineering instance.Furthermore,extensive parametric analyses are further conducted to investigate the effects of heterogeneity and porosity of soil beneath pile toe as well as the defect of pile on the vertical dynamic response of the floating pile.(5)Based on the semi-analytical solution for velocity in the time domain of pile with a defect in heterogeneous saturated soil,the quantitative indicators of pile defect and corresponding parameters within the reflected velocity wave curve are defined.Then,the intrinsic relations between these indicators and parameters are obtained by combining analytical and numerical fitting methods.On this basis,the obtained intrinsic relations are integrated in the framework established by Ontology to realize the sharing of related knowledge in the field of architecture.Furthermore,a quantitative identification program of pile defect is developed by using MATLAB,where the integrity of pile can be evaluated reasonably,accurately,and rapidly based on the specific reflected wave curve.The corresponding work in this paper is of great practical significance for improving the basic theory of longitudinal vibration of floating pile and guiding the integrity evaluation of pile.