Impedance Functions of Piles in Inhomogeneous Media

Abstract

A new model is presented for characterizing the response of soils within the boundary zone around piles. The proposed concept provides for a continuous variation of soil properties with smooth transition into the outer zone; these properties alleviate the wave reflections from the interface between the two media. With this model the impedances of composite layers do not show the oscillations that are generally observed with the other boundary zone models that take account of the soil mass. The developed impedance functions are used in the dynamic analysis of a field problem involving vertical vibration of a single pile. Comparison of the theoretical predictions with the experimental data in this case indicates that inclusion of the boundary zone results in a reduction in the stiffness and damping for the pile‐soil system which in turn causes a reduction in the resonant frequencies and an increase in the resonant amplitude of piles. The results show that the proposed boundary zone model improves the agreement between the theoretical predictions and field‐measured data.