Centrifuge Modeling for Cyclic Axial Performance of Helix Piles in Sand

ABSTRACT: The article shows the axial load responses of five instrumented model aluminum piles subjected to incremental cycles of pseudo-static loads through centrifuge model testing in dry sand. Average axial cyclic displacements of 1%, 2%, 5%, and 10% of the shaft or helix diameter were adopted in four packages. Later, a post-cyclic monotonic compressive displacement was implemented. All load tests were conducted inflight at 20 g scale units. It was observed that, with increased cycle intensity, the load-bearing capacity of the piles increased. However, a loss of strength occurs due to a possible gap formed at the base and around helices. Moreover, the theoretical equations over predicted the ultimate axial capacity of the piles. The piles with double helices and larger inter-helix spacing generally provided a higher load-bearing capacity. Last, the distribution of the ultimate axial loads, the maximum loads from cyclic sequences, and the ultimate unit post-cyclic shaft resistances are shown.