Cyclic response of axially loaded tapered piles

Instrumented model piles were used to investigate the fundamental behaviour of tapered and cylindrical piles in loose sand due to cyclic loading, using a centrifuge facility. The objectives of this study were to understand and evaluate the cyclic performance of tapered and cylindrical piles and to investigate the degradation in the pile capacity due to cyclic loading. The results of controlled-displacement cyclic loading tests on twelve one tenth-scale model piles with different taper angles in a centrifuge setup were presented and discussed. Six piles were instrumented and six were not. The load-movement curves of tapered and cylindrical piles were measured and compared. The load settlement curves due to axial compressive loading tests before and after cyclic loading tests were compared as well. The comparison showed that cyclic loading led to a change in the load transfer patterns so that a greater portion of the load was carried by toe resistance and a smaller portion by the shaft resistance. The degradation in the axial capacity for both tapered and cylindrical piles was more pronounced for longer piles (1/d = 26, where 1 is the embedded pile length and d is the average pile diameter). The results of this study suggest that the tapered pile response due to cyclic loading is comparable to that of straight-sided piles.