Keywords

Uniform piles, Tapered piles, Static loading test, Dynamic test, Shaft and toe resistances, Force converted from strain, t-z and q-z functions, CPT-sounding

Abstract

Anecdotal observations of axial response of uniform and tapered piles and model-scale tests have suggested that tapered piles provide higher bearing than uniform piles of equivalent dimensions. However, there is minimal reliable full-scale comparative data. Records of three previous full-scale tests comparing the response to load of equivalent uniform and tapered piles in Sweden, Iran, and Italy were analyzed, along with results of recent instrumented full-scale test piles in Mobile, Alabama, USA. The results of all tests showed that tapered piles developed substantially larger shaft resistance, at least doubling that of the uniform piles along the tapered length and, despite the smaller toe size, the bearing of equal-size tapered piles exceeded that of uniform piles by up to 20% at comparable settlements. Back-analysis using UniPile6 software confirmed that the increased shaft resistance due to the taper could be represented as a “donut” effect. Lessons were learnt about how not to arrange details of a test.

DOI