Question

Consider the following statements regarding negative skin friction in piles:

Which of these statements is/are correct?

• A. 1 alone
• B. 2 alone
• C. 2 and 3
• D. 1 and 3

Answer 1

The correct option is D 1 and 3

Pile installed in freshly placed fills of soft compressible deposits (clays) are subjected to a downward drag, a consequence of the consolidation of the strata after the piles are installed. This downward drag on the pile surface, when the soil moves down relative to the pile, adds to the structural loads and is called negative skin friction. This is in contrast to the usual shaft friction which is mobilized when the pile moves down relative to the soil. Thus negative skin friction has an effect of reducing the allowable load on the pile. Negative skin friction may also develop if the fill material is a loose sand deposit. It can also occur due to the lowering of the ground water table which increases the effective stress, thus causing consolidation of the soil with the result down drag of piles.