Non-Linear Soil Properties and Impedances for Axially Vibrating Pile Elements

Dynamic soil properties around axially vibrating piles are generally non-uniform even in homogeneous soils. This is a result of the non-linear soil reaction to the radially decreasing stresses and strains induced by the pile, as well as the slippage at the pile-soil interface. To improve the accuracy of analytical computations, this paper focusses upon the nonlinear soil response anticipated in the field and establishes the radial variation of soil properties based on commonly reported experimental data. In addition, solutions are presented for the corresponding impedance of the springs and dashpots used to represent soil in a Winkler-type analysis of axially vibrating piles. Slippage at the pile soil interface is taken into account assuming a rigid-perfectly plastic contact between the pile and the soil. To assess the relative effects of soil nonlinearity in practical applications, analytical results for different pile, load and soil conditions are presented in the form of diagrams and simple approximate relationships.