Tension tests on bored piles in residual soil

A series of twelve bored piles were installed in a residual soil profile at the FHWA Turner-Fairbank Highway Research Center in McLean, Virginia. The piles were load tested to failure in axial uplift (tension) to determine the ultimate skin friction available in a residual weathered soil profile. Pile diameters varied from 143 mm to 244 mm and lengths varied from 2.44 m to 6.10 m. The piles were constructed using continuous hollow stem night augers with concrete placement by gravity free-fall. Following the completion of the load tests, ten of the piles were extracted and the "as constructed" pile lengths and diameters were measured. The results of these rests are being used to design larger diameter bored piles that will be used as loading reaction to load test a full-scale bridge superstructure. The load displacement behavior of the piles are presented and it is shown that the test results may be described in nondimensional form.