When pile driving is difficult and/or economically not viable, cast-in-place piles are indispensable. Tapered piles, which have top cross-sections larger than the bottom cross-sections, have the potential for substantial advantages over conventional straight-sided piles. This paper investigates the construction and performance of innovative drilled concrete tapered piles. A full-scale pile load-testing program was conducted to evaluate the axial compressive capacity of drilled concrete tapered piles in clayey silt. Four augers (three tapered and one straight) were designed and manufactured to produce required six piles. Six piles that were constructed and tested included four tapered and two straight piles. The testing results showed that tapered piles with a taper angle varying between 0.95º and 1.91º had load carrying capacity up to 50% higher compared with the straight-sided piles with equal volume. It should be noted, however, that the experimental results are site specific and must be used with caution. Moreover, an analytical expression was developed to evaluate the pile taper effect on its shaft capacity in terms of a taper coefficient, Kt. The value of Kt. evaluated from the analytical expression compared well with experimentally measured values. Finally, a 2D non-linear finite element analysis was conducted to simulate the load test conditions, which has proven to successfully predict the load sharing mechanism of the tapered piles. |
