饱和土中变截面大直径桩纵向振动理论解和数值解对比分析

基于饱和多孔介质理论,对饱和土中变截面大直径桩的纵向振动特性进行研究。首先根据饱和土动力控制方程,得出大直径桩侧土体复刚度,桩底采用黏弹性支承,再将桩身按变截面分段,采用能考虑横向惯性效应的Rayleigh-Love杆模型建立大直径桩的动力方程。结合初始条件、边界条件和连续条件,利用阻抗递推法求解变截面大直径桩-土动力方程耦合方程得出桩顶频域解析解,通过卷积定理和逆傅里叶变换得出桩顶速度时域半解析解。然后利用ANSYS/LS-DYNA建立有限元模型,将数值解和理论解在桩身存在软硬夹层、变截面以及变截面段桩的长度和位置变化等情况进行了对比分析,利用数值计算解验证了理论计算模型的正确性。

Comparative Analysis of the Theoretical Solution and Numerical Solution on Vertical Vibration of Large Diameter Pile with Variable Sections in Saturated Soils

Based on saturated porous media theory, the vertical vibration of large diameter piles with variable sections in homogeneous saturated soil is studied. Firstly, according to the dynamic control equation of saturated soil, the complex stiffness is obtained. The bottom of pile adopts viscoelastic support, Then, the pile body is divided according to variable sections. The dynamic equation of large diameter piles is established by Rayleigh-Love rod model which can consider the transversal inertia effect.Combining the initial condition, boundary condition and continuous condition, the impedance recurrence method is used to solve the coupling equation of large diameter pile-soil dynamic equation with variable sections. The analytical solution of pile top in frequency domain is obtained. The semi-analytical solution of pile top velocity in time domain is obtained by convolution theorem and inverse Fourier transform. Then, the finite element model is established by ANSYS/LS-DYNA, the numerical and theoretical solutions are compared and analyzed under various working conditions. The correctness of the theoretical calculation model is verified by numerical solutions.