الفهرس 
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Abstract
Piles driven into soft clay are often subjected to Downdrag force. The
downdrag force develops negative skin friction on the pile shaft. Negative skin
friction is the most common problem in the design and construction of pile
foundations in soft soil. Depending on the relative movement of the pile soil
system, positive and negative skin friction developed on pile shaft.
This research investigates the behavior of pile during soil consolidation.
Experimental work was developed to analyze the negative skin friction on a
single pile embedded in clay. The clay layer was allowed to consolidate under
the effect of surcharge loading.
The investigation depicts that monitored strains along the pile length
reflect the consolidation process with time. Strain increases from the pile top
until it reaches a peak value at the location of the neutral plane. Shear stress, as
a function to the axial strain, is initiated from zero value at the surface of the soil
and increases until it reaches a peak negative value at an intermediate depth.
Then, it decreases down to zero at the elevation of the neutral plane, where the
positive skin friction develops. The neutral plane is located toward the end of
the pile as the base layer getting stiffer. Closed form equations of Shong, 2002,
can predict the experimental results in very well agreement. I