Axial Pile Capacity of Large Diameter Cylinder Piles

This paper reports on the behavior of large diameter cylinder piles under both driving and static conditions. Of special interest is the understanding of the tip resistance and the associated soil column within the pile under static and dynamic conditions. An analysis of driving forces, shows that inertia on the soil plug rapidly exceeds the static skin friction between the pile and soil on the inside of the cylinder. The analysis of the soil column for static conditions was undertaken with an Eulerian finite element viscous analysis, ADINA-F. The static analysis revealed that even when the cylinder "cookie cut" under driving it behaved "plugged" under static conditions for a multitude of soil strengths and wall thicknesses. Next, based on a database of 35 load tests (22 concrete & 13 steel) unit side shear and end bearing for cylinder piles as a function of pile material (i.e., steel and concrete) and insitu SPT N were developed and compared successfully to Schmertmann's original values for small diameter piles. Finally, LRFD resistance factors, φ, for the proposed cylinder pile design were determined.