Setup of Driven Piles in Layered Soil

The load capacity of driven piles has been reported to sometimes increase or decrease with time after pile installation. An increase in pile capacity with time is known as setup, whereas a decrease in capacity is referred to as relaxation. In this paper, we review the current understanding of pile setup and discuss how to account for it in design. A total of forty-three dynamic tests were conducted over a period of five months on four H piles and four closed-ended pipe piles driven into layered soil. Test results show that the amount and rate of pile setup are quite different from those observed in other studies. Empirical formulas for predicting setup proposed by several researchers were compared with observations. Of the empirical formulas considered, the Svinkin (1996) lower-bound method predicted the rate of setup on these piles driven in layered soil relatively well. Additionally, some theoretical methods for prediction of evolution of static pile bearing capacity with time were tested against the dynamic pile test results. The bearing capacity from these theoretical methods was found to correspond to approximately 2 times the capacity measured at the end of initial driving by a dynamic test.