Numerical modelling of negative skin friction on pile groups

Abstract

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. The soil behaviour is modelled using a hybrid approach in which the soil response at the individual piles is modelled using the subgrade reaction method while pile-soil-pile interaction is determined using elastic theory. The main difference between the methods lies in the manner in which pile-soil-pile interaction is determined. The accuracy of the methods is assessed by comprehensive comparisons with more rigorous theoretical solutions available. The study shows that: (a) the solutions obtained by the continuum model using Chan et al.'s solution are in close agreement with the rigorous solutions, (b) for practical pile groups, the layer model can give reasonable solutions provided the socketing is not too deep and (c) the continuum model using Mindlin's solution predicts reasonable downdrag forces but seriously under predict the pile head settlements.