Study On The Longitudinal Vibration Of Large Diameter Piles Based On The 3-dimensional Continuous Medium Soil Model

In order to adapt to the rapid development of construction,the request about the pile foundation bearing capacity and deformation capacity of the upper building structure is demanding higher and higher,so the pile foundation presents the trend of the development of large diameter piles.However,due to the particularity of large diameter pile body size,its mechanical calculation is more complicated.Compared with the ordinary pile type,the longitudinal vibration dynamic characteristics study of large diameter piles in the three-dimensional continuous medium soil model are relatively scarce.In the theoretical aspect,in this paper,the model of the large diameter piles body in the three-dimensional continuous medium soil model,relationship between pile side soil and pile body and supporting effect of pile end soil to pile body are simplified.This paper using the analytic method systematically studies the large diameter piles' pile-soil coupling longitudinal vibration of the homogeneous foundation,radial heterogeneous foundation and the change of pile supporting for fictitious soil.In the experimental aspect,this paper has carried out indoor simulated pile test,compared the experimental data with the theoretical model data and analyzed the feasibility of the large diameter longitudinal vibration theory based on the three-dimensional continuous medium soil model.The main content of this paper are as follows:(1)Based on three dimensional wave effect of soil and Rayleigh-love rod model of large diameter pile,regarded the pile side soil as a homogeneous case,assumed the bottom of pile to be elastic support,and established the analytical solution of the pile soil interaction vibration theory combining with the definite conditions.This paper studied the necessity of considering the large diameter piles' transverse inertia effect and the influence of pile parameters(pile diameter and Poisson's ratio of pile body)on the pile top vibration characteristics.(2)Considering the effect of construction of large diameter pile,using the continuity conditions of stress and displacement between the spheres by orthogonal recursive function,established the large diameter pile dynamic response theory under the condition of radial heterogeneous.Study the influence of related trait parameters(the scope of construction disturbance,layer number of radial soil and the change of disturbance degree)on the pile top vibration characteristics under the pile soil hardening or softening conditions(3)Change the pile supporting model for fictitious soil pile model,through integral transform and recursive pile impedance analytical solution in frequency domain and time domain semi analytical solution.According to the theory of solution,study the effects of the fictitious soil pile parameters(the classified accuracy of fictitious soil pile,the length of fictitious soil pile and the shear wave velocity of fictitious soil pile)on the pile top vibration characteristics.(4)Using the low strain dynamic pile wireless measuring instrument test the pile top velocity time curve of pile model,fit the theory and test curve by changing the model pile diameter and model pile material,and to verify the correctness of theoretical model.(5)Finally,the above results of this study are summarized,and puts forward for the proposed follow-up study of the longitudinal coupling vibration of large diameter piles under three dimensional wave effects of soil mass.