An efficient analysis method is presented for assessing the response of single piles and pile groups subjected to negative skin friction (NSF). The method involves two separate steps: (1) estimate of the free-field ground movements in the consolidating soil, and (2) analysis of the piles subjected to the computed free-field ground movements by means of PGROUPN, a computer program based on a 3D non-linear boundary element solution. The impact of various factors which affect the response of piles to NSF is examined, including the number of piles, the pile spacing, the additional presence of pilehead loading, and the influence of soil nonlinearity and pile-soil slip. Results provide insights into the correct understanding of NSF effects on pile behaviour and show the importance of considering such aspects as pile-soil slip and group interaction effects. In particular, it is demonstrated that the usual detrimental effect of group interaction among piles is diminished by the beneficial group effect for piles under NSF, thereby resulting in a lower values of drag force and drag settlement as compared to a single isolated pile.
Subjects: piles, pile groups, BEM, negative skin friction
Author: Francesco Basile, PhD, MEng
Publisher: DFI, EFFC