PREDICTION OF PILE SET-UP IN NON-COHESIVE SOILS. IN: CURRENT PRACTICES AND FUTURE TRENDS IN DEEP FOUNDATIONS

The capacity of driven piles in sand often increases with time. This is typically referred to as pile "setup." The current practices of predicting pile setup is based on the assumption that the rate of setup is linearly proportional to the logarithm of time. However, review of case histories indicate a larger scatter of data points when time-dependent pile capacities are plotted against logarithm of time, and the rate of setup per log cycle of time depends on the selected time frame of reference. This paper proposes using hyperbolic functions to predict pile setup. Comparison of pile test data reported in various case histories show excellent agreement with the hyperbolic function empirically determined by Bogard and Matlock (1990), which was developed for piles in clay. This paper also demonstrates that, with high quality pile test data, long-term pile capacity can be predicted using short-term pile test data and the hyperbolic function.