Time Dependent Capacity Increase for Driven Pile in Cohesionless Soil

The increase in driven pile capacity with time is termed set-up. The mechanism contributing to this phenomenon is not yet fully understood. Moreover, a rational approach to account for the increase in driven pile capacity with time in design has not yet been developed. In this study, a database comprising of 55 pile load tests (static and dynamic tests) were collected from the current engineering literature. The piles were driven in cohesionless soils with sand relative density varying from loose to dense. The measured capacities of the database piles with time were correlated to pile characteristics and soil properties. Pile set-up was found to be a phenomenon related to an increase in pile shaft friction with time and increases with decreasing pile diameter. On the other hand, pile setup was found to increase with increasing pile penetration depth and thus with pile slenderness ratio. A new approach for the estimation of pile set-up in cohesionless soils is presented in this study. The new approach considers the effects of pile characteristics and soil properties. Comparison of predicted and measured pile set-up using the developed method in this study indicates reasonable agreement. Also, comparison of prediction using the new approach with those made using previously published methods indicates that the developed method in this study yields better results.