Broad Synthesis of Factors and Mechanisms Contributing to Time-dependent Increase in Axial Capacity of Driven, Jacked, and Vibrated Piles

Abstract Soil/pile set-up is a complex phenomenon that refers to the increase in axial geotechnical capacity of driven, jacked, or vibrated piles with time after installation. The phenomenon is affected by a range of factors and mechanisms related to the ground conditions, pile size and geometry, pile material, installation method, testing protocol, loading history, and environmental conditions. Due to the range of mechanisms that affect set-up response, and the complex pile-soil interactions that occur during installation and which give rise to these mechanisms, understanding the set-up phenomenon and estimating the capacity increase with time in a broadly applicable manner remains an outstanding research question. This paper summarises the factors and mechanisms currently understood to affect set-up based on an extensive body of available research undertaken over the past 80 years to provide a reference for practical use and to facilitate further research. From a practicing engineer’s perspective, this summary is intended to increase awareness of the propensity for set-up on a particular site, which may help limit delays as contractors wait for piles to demonstrate capacity, or allow for more efficient designs where time permits incorporation of set-up over a longer period to optimise pile capacity calculations.