An experimental program using large model piles in sand was conducted
to study the shaft resistance behavior of piles subject to uplift load
s. Model single pipe piles of different diameters (45 to 178 mm) were
subjected to static uplift loading to failure. The piles, which had an
embedded length of about 1.7 to 2 m, were installed in a large test p
it (3 by 3 by 3 m) by three different methods (driving, jacking, and a
reference undisturbed method with negligible lateral displacement) to
assess the influence of method of installation on shaft resistance. T
he tests were performed in two initial densities of a sand (loose and
dense). The experimental results were analyzed statistically. The resu
lts show that the initial sand density and the method of pile installa
tion are the most significant factors that affect uplift capacity. Ins
tallation methods that cause less disturbance give higher uplift capac
ity. Unit shaft resistance could be reduced as much as by half dependi
ng on the method of pile installation relative to the undisturbed meth
od. The displacement at the ultimate uplift load is in the range of 5
to 12.5 mm and independent of soil type and pile diameter, but depends
on method of pile installation.