Technical Notes > Negative Skin Friction

When a pile is driven through a layer of compressible material, before consolidation is complete, the soil will move downwards relative to the pile inducing friction forces between pile and soil that give rise to the phenomenon of so called negative skin friction. The effect of negative skin friction is to raise the axial load on the pile with consequent increase in settlement due to the elastic shortening of the pile under the increased load. The force arising fromthe negative skin friction effect is assessed as the frictional component of lateral resistance ( see Trunk Resistance) along the side surface in contact with the layer in which the phenomenon arises, but of opposite sense to positive friction. The resultant force so determined is not subtracted from limit load but from the operational load.