Single pile under vertical vibrations in cohesionless soil

The vertical response of a fixed-head floating single pile embedded in sand is obtained experimentally under 1g conditions. Specifically, pile head stiffnesses and axial strains generated along the pile length for a range of static and dynamic pile head loadings are measured. To account for the effects of soil non-linearity on the static response of the pile, a range of low- to high-magnitude static displacements is considered. Likewise, for the dynamic response, varying amplitudes of vertical harmonic accelerations for a wide range of frequencies are considered. Results obtained from the experiments under both the static and dynamic loading conditions indicate that the pile head stiffness is dependent on the direction of pile head loading - that is, whether the pile is pushed or pulled. To gain further insight into such direction-dependent pile head stiffness, three-dimensional non-linear finite-element analyses are carried out. Numerical results show very good agreement with the experimentally measured pile head stiffnesses. Axial strains generated along the pile length due to head loadings, on the other hand, depend on the amplitude of both the static and the dynamic loadings.