Question

The negative skin friction on a pile develops when

• A. the soil surrounding the pile settles more than the pile
• B. pile is driven in sand
• C. the ground water table rises
• D. the soil near the pile tip is clay

Hint:

Negative skin friction is a critical design consideration for piles, as it adds to the axial load, potentially leading to pile failure or excessive settlement if not accounted for. It can be mitigated by measures such as bitumen coating on piles, overboring, or preloading the soil.

Answer 1

The Correct Option is A

Negative skin friction, or downdrag, occurs when the surrounding soil settles more relative to the pile. This results in a downward frictional force acting along the pile’s surface.

Key factors influencing negative skin friction include:

• Settlement of soil: When the soil around the pile settles, particularly due to its self-weight or consolidation, more than the pile, it drags the pile downward, leading to negative skin friction.
• Characteristics of soil: Fine soil types, such as clay, with a higher potential for consolidation, can exacerbate this phenomenon when they undergo settlement.

The correct answer is: the soil surrounding the pile settles more than the pile.