NEGATIVE SKIN FRICTION ON SINGLE PILES IN A LAYERED HALF-SPACE

Settlement of the surrounding soil due to surcharge placement may give rise to negative skin friction developed in piles. In this paper, a s imple discrete element approach using subgrade reaction method is prop osed to analyse negative skin friction on single piles. The pile is em bedded in a two-layer soil where the upper soil layer undergoes consol idation while the lower soil layer acts as a stiffer bearing stratum. Two different and uncoupled deformation modes, one at the pile shaft a nd the other at the pile toe have been assumed in the determination of the soil stiffness. The effects of a compressible bearing stratum and embedment length of the pile in the bearing stratum are considered in the analysis. This simple approach is verified by comparison with rig orous methods of modelling the soil as an elastic continuum. Three rep orted case histories are analysed and the computed results are shown t o be in reasonable agreement with the field measurements.