Abstract:
3D ABAQUS model has been conducted to investigate the effect of negative skin friction
on piles installed through soft clay .Coulomb frictional model built in ABAQUS can be
selected to depict the interaction at the pile-soil interface condition which has frictional
coefficient . NSF is a common problem if a pile is designed in a highly compressible soil.
A grid configuration of 3 x 3, 4 x 4 and 5 x 5 piles was considered for this research. The
effects of pile tip, pile shaft friction, pile socket length, and magnitude of applied load and
load variation on the pile were studied. The pile cap selection was done by considering
formation of constant pile cap settlement and uniform distribution of loads throughout the
pile cap length. In the case of a short pile, the negative skin friction may cover the most
entire length, and accordingly, the down-drag force is transmitted to the pile’s tip in the
form of penetration to the underlying strata, whereas for a long pile, the down-drag force
is mainly taken by the compression of the pile’s material and little or none is transmitted
to the pile’s tip. The maximum mobilized negative shaft resistance developed at the entire
depth of the pile and this value changed to zero at the neutral point. At the working load
level, the drag force may be large enough to reduce the pile capacity or to overstress the
pile’s material, causing fractures or perhaps structural failure of the pile, or possibly
pulling out the pile from the cap when L/D become small. For similar axial load
application into the model with and without pile cap, the negative skin friction distribution
made visible difference.