Uplift resistance of belled and multi-belled piles in loose sand

Abstract

In this study, a series of small scale tests are conducted on belled and multi-belled piles in dry loose sand. The installed piles were carefully instrumented with several LVDTs, strain gauges, and a load cell. Results recorded from a laboratory model tests were used to investigate the potential benefits of installing belled and multi-belled piles in increasing the uplift load capacity and also to reduce vertical ground deformation adjacent to the pile. Finite element modeling (FEM) is also performed to assess the soil particle movement, inside the glass box, during pile uplift displacement. The results unveils that increasing the number of wings will not always increase the uplift resistance of piles. For instance, in comparison with the straight pile, the uplift resistance increases up to 60% when the belled installed at the pile base and it decreases about 4% when installed at the depth equal to 33% of the pile length. In addition, for a similar uplift displacement, the pile with installed belled at the base could reduce 75% of the ground surface deformation, comparing to the straight pile.