Study On Coupled Vibration Of Large Diameter Pile With Variable Sections In Saturated Soil And Experimental Analysis

Based on plane strain model,substitute the complex stiffness for the effect of soil on pile,the coupling vibration model of the large diameter pile with variable sections in saturated soil and the coupling vibration model of the expanding head of large diameter pile in saturated soil are established respectively.The theoretical solution of the appeal theory model is verified by numerical simulation and indoor model test,which proves the correctness of the theoretical model.The main work of this paper can be divided into the following aspects:(1)The coupling vibration model of the large diameter pile with variable sections in saturated soil is established.Based on the porous medium theory and Novak thin layer method,the dynamic control equation of saturated soil is established,and the complex stiffness of saturated soil on pile side is obtained.The bottom of pile adopts viscoelastic support,segment the pile according to the section size.Each section is regarded as Rayleigh-Love rod to consider its transversal inertia effect.Impedance and the analytical solutions in frequency domain at pile head are obtained by Laplace transform combined with initial,boundary,continuous conditions and impedance function transfer method.The semi-analytical solution of velocity response at top of pile in time domain is obtained by convolution theorem and Fourier inverse transformation.The influence of soft and hard interlayers in the soil around the pile,large diameter pile with variable sections and the change of the length and position of variable sections on the dynamic response of the top of the large diameter pile with variable sections are analyzed.(2)The coupling vibration model of the large diameter pile with expanding head in saturated soil is established.Based on the porous medium theory and Novak thin layer method,the dynamic control equation of saturated soil is established,and the complex stiffness of saturated soil on pile side is obtained.The bottom of pile adopts viscoelastic support,segment the pile according to the section size.Each section is regarded as Rayleigh-Love rod to consider its transversal inertia effect.Impedance and the analytical solutions in frequency domain at pile head are obtained by Laplace transform combined with initial,boundary,continuous conditions and impedance function transfer method.The semi-analytical solution of velocity response at top of pile in time domain is obtained by convolution theorem and Fourier inverse transformation.Then the effects of volume fraction of soil water at pile side,shear wave velocity of soil at pile side,diffusive angle of enlarged pile head and pile length on dynamic response of large diameter pile top withenlarged pile head are analyzed.(3)Finite element model are carried out by using ANSYS finite element software.The influence of soft and hard interlayers in the soil around the pile,large diameter pile with variable sections and the change of the length and position of variable sections on the dynamic response of the top of the large diameter pile with variable sections are analyzed.Then the effects of volume fraction of soil water at pile side,shear wave velocity of soil at pile side,diffusive angle of enlarged pile head and pile length on dynamic response of large diameter pile top with enlarged pile head are analyzed.(4)Indoor model test is carried out.Three model piles,complete pile,neck-shrinking pile and neck-expanding pile were prepared.Low strain dynamic experiments were carried out on the three piles,and the velocity-time curves of pile top were extracted.By inversion and fitting,the experimental solution is compared with the theoretical solution to verify the correctness of the theoretical solution in this paper further.