Uplift Capacity of Driven Piles from Static Loading Tests

A pile driving and testing program was undertaken to evaluate installation procedures, assess capacity (particularly in uplift) of 24- and 30-inch square, prestressed concrete piles, and provide foundation design parameters for the New Edison Bridge project in Fort Myers, Florida. The subsurface profile generally consisted of three major soil strata: an upper clayey sand and sandy clay layer to a depth of about 45 to 50 feet below mudline, a medium dense to dense silty sand middle layer about 10 feet thick, and a third layer of dense to very dense silty fine sand. Eleven prestressed concrete test piles of varying length were driven at five test sites and uplift tests were performed to allow an independent evaluation of the different soil layers. All piles were dynamically monitored during installation and restrikes to evaluate pile drivability and bearing capacity including time related capacity increases due to soil set-up. This paper presents descriptions of the pile driving and load testing program along with findings regarding pile uplift capacities from load tests, pile capacities from dynamic testing, soil-pile adhesion values, wave equation factors, soil strength vs time dependency, foundation design and pile driving recommendations