The shaft capacity of CFA piles in sand

This paper presents the results of a series of field experiments performed to study the development of shaft resistance on Continuous Flight Auger piles installed in sand. The test piles were instrumented in order to separate the shaft and base resistance, and to allow the determination of the distribution of shaft resistance along the pile shaft. The tests highlighted the importance of accurate calculation of the shaft resistance for non-displacement piles. At a typical maximum allowable pile head settlement of 25 mm, more than 71 % of the pile resistance was provided by shaft
friction. Conventional methods of estimating shaft resistance were assessed. It was found that methods which incorporated parameters directly interpreted from in-situ test results provided the most consistent estimates. In the final section, differences
between the shaft resistances mobilised on displacement and non-displacement piles
are considered.