Vertical Vibration Of Large Diameter Pile In Saturated Soil

In China's Yangtze River Delta,Pearl River Delta and other coastal areas,has a high population density and accompanied by a large number of large-scale construction projects.In these areas,low elevation,river network vertical and horizontal,soft soil,high water table,large water content,so the large diameter pile in these areas is to be used in large quantities.At present,the study on the vertical vibration of large diameter pile in saturated soil is not enough,therefore,based on theoretical analysis,the coupling vibration model of pile-soil in homogeneous saturated soil and layered saturated soil is established.The correctness of the theoretical model is verified by the pile-soil vibration model test.The main contents of this paper are as follows:(1)Based on the theory of saturated porous medium and the Novak thin layer method,the pile is regarded as a Rayleigh-Love rod,and the pile soil interaction model is established by using the support of the viscoelastic pile foundation,the expression of complex stiffness and expression of velocity response at pile head in frequency domain and time domain is derived.Then the effects of water volume fraction,the transverse inertia effect,pulse width,ratio of length to diameter of pile,pile soil soft(hard)sandwich and soft(hard)defect layer thickness,pile(neck and neck expansion)and the degree of defect length and other factors on the dynamic response at pile head are analyzed.Besides,the dynamic response at pile head in dry soil and saturated soil is compared.(2)Based on saturated porous media theory and Novak thin-layer method,the pile-soil interaction model is established with dispersion fictitious soil pile model and the expression of dynamic response at pile head is obtained.Then the effects of cone angle of fictitious pile,thickness of rock socketed pile bottom sediment,and other factors on the dynamic response at pile head are analyzed.(3)The low-strain pile foundation dynamic experiment of different pile diameter and different material is carried out.The effects of pile diameter,pile material and pile-soil modulus ratio on the velocity response of at pile head is verified from the experimental point of view.Based on the model experiment,the theoretical results are compared with the experimental results,and the rationality of vertical vibration theory of large diameter pile foundation in saturated soil based on fictitious soil pile model is verified.