Numerical study of geometric characteristics of helical piles subjected to uplift

Plenyo Nahen Gonzaga Araújo¹; João Paulo da Silva Costa¹; Yuri Daniel Jatobá Costa¹

¹ Universidade Federal do Rio Grande do Norte

doi:10.20906/CPS/CILAMCE2017-0268

Resumo

This paper presents results of numerical simulations of steel helical screw piles subjected to uplift loading, installed in a sedimentary sand deposit. The models have been validated against results of full-scale field tests. The numerical model was built using a finite element code. Analyses were performed to evaluate the effects caused by variations of spacing between helices, helix diameter and depth of installation. Evaluation of failure mechanisms developed in the soil mass surrounding the pile was made possible. Results showed that the transition from shallow to deep anchor conditions is achieved with an embedment ratio around four. Failure of shallower installations resembles a cylindrical shear failure mode, while failure of deeper installations resembles an individual bearing plate failure mode. Enlarging helix mean diameter results in a linear increase of soil-pile uplift capacity. Increasing inter-helix spacing ratio causes the load to transfer from the top helix to the lower helices and an augment in the uplift capacity. Developing failure mechanisms changes from cylindrical shear to individual plate failure as space ratio is increased. Piles with spacing ratios under 2.8 exhibited shallow anchor behavior.

Palavras-chave: Helical piles; Finite element method; Load tests; Sand