Nonlinear Behavior of Single Piles Vibrating Vertically

A numerical method is presented for analyzing the nonlinear behavior of single piles subjected to harmonic vertical or torsional loading. The method combines the finite element method accounting for nonlinear soil behavior in the near field and a semi-analytical formulation for radiation damping in the far field. Nonlinear stress-strain characteristics of soil are considered with a shear modulus degradation model used in soil dynamics and earthquake engineering. Mohr-Coulomb strength criterion is used to approximate the contact property at the pile-soil interface. The method is simplified but versatile, and the soil parameters required are relatively few being all the standard geotechnical parameters. The comparisons between the predictions and the results from field tests and a boundary element method are made to verify the present method. A parametric study indicates that the linear analysis overestimates both the stiffness of piles and the interaction factor for the pile group effect.