Variation of Stiffness at the Tip of Piles Subjected to Load-Unload Cycles: Numerical Modeling

Abstract

AbstractThis study evaluated how the stiffness at the tip of the piles varies when the elements are subjected to load-unload cycles. In this study, a finite element model (FEM) was calibrated with the measurements of stress and deformation recorded in a load test on a 16-inch diameter and 28-inch high pile; the calibrated model was subjected to different confinement values and load-unload cycles to evaluate the incidence of these parameters in the variation of the stiffness at the pile tip. The results showed that the soil’s stiffness at the pile tip decreases as the displacement of the pile increases. It was found that when confinement values are greater than 30 PSI, the increase in the displacements in the pile has a greater incidence in the loss of rigidity; on the other hand, as the magnitudes of the load-unload cycles increase, the stiffness of the soil under the pile tip is decreased until reaching a residual stiffness.