Data Reduction and Dynamic p-y Curves of Helical Piles from Large-Scale Shake Table Tests

Abstract

A helical pile is composed of a steel shaft and single or multiple helical plates welded to its shaft. This study investigated full-scale seismic soil reactions for helical piles embedded in dry sand. Ten helical and driven piles were installed in sand enclosed in a laminar shear box mounted on a large outdoor shake table. The paper discusses interpretation of the seismic loading data and the derived dynamic p-y curves. It examined different curve-fitting formulations utilized for interpretation of pile deformation and soil reactions from measured strains during the tests. An optimum curve-fitting function was selected considering the current test setup and was used to establish soil resistance along the pile shaft and the corresponding p-y curves under simulated earthquake records. The influences of loading frequency, loading intensity, installation method, number of helices, shaft shape, and coupling type on the dynamic p-y curves were evaluated. It was found that the loading frequency and intensity had no effect on the dynamic p-y curves, whereas the installation method, number of helices, and pile shaft shape had minor effects on the obtained dynamic p-y curves.