Axial Resistance of Nondisplacement Pile Groups in Sand

Abstract

When subjected to axial loading, the response of a pile in a pile group is different from that of an isolated single pile, all other factors being the same. Three-dimensional finite-element analyses were performed to study the response to vertical loads of nondisplacement pile groups in sand. The analyses were done with an advanced bounding-surface-plasticity constitutive model. The mechanical response of soil elements at various locations between the group piles was thoroughly investigated to reveal the underlying pile–soil–pile interaction mechanisms. Pile group efficiency was found to be a function of the pile head settlement, number of piles in the group, pile-to-pile spacing, and relative density of the sand. The effect of cap–soil contact on the pile group resistance development was also studied. For small pile groups, the group efficiency is close to or greater than 1 at settlement levels likely to be of interest in design.