NUMERICAL MODELING OF NEGATIVE SKIN FRICTION ON PILE GROUPS

Simplified methods for the analysis of socketed pile groups subject to negative skin friction are reported. In these methods, the piles are modelled using discrete elements with an axial mode of deformation. Th e soil behaviour is modelled using a hybrid approach in which the soil response at the individual piles is modelled using the subgrade react ion method while pile-soil-pile interaction is determined using elasti c theory. The main difference between the methods lies in the manner i n which pile-soil-pile interaction is determined. The accuracy of the methods is assessed by comprehensive comparisons with more rigorous th eoretical solutions available. The study shows that: (a) the solutions obtained by the continuum model using Chan et al.'s solution are in c lose agreement with the rigorous solutions, (b) for practical pile gro ups, the layer model can give reasonable solutions provided the socket ing is not too deep and (c) the continuum model using Mindlin's soluti on predicts reasonable down-drag forces but seriously under predict th e pile head settlements. (C) 1996 Elsevier Science Ltd.