Testing of Augered Cast-in-Place Piles Installed with Varying Auger Rotations

Augered cast-in-place piles are installed by the excavation of the soil by rotation of a continuously flighted auger into the ground and then placement of a fluid cement grout into the evacuated volume as the auger is extracted. The soil conditions immediately after excavation for augered cast-in-place piles will be related to the in situ soil conditions, the auger specifications, and the rates of penetration and auger rotation. Intuitively, the potential for soil removal will increase proportional to the number of auger rotations; however, the soil transport mechanism involved is complex. To evaluate the effect of augering on the axial behavior of full-scale augered cast-in-place piles, four piles were installed with varying auger rotations and then load tested in axial compression. The soil conditions were primarily sand above the water table. The results of cone penetration testing indicate that the number of auger rotations did not significantly influence the cone resistance in the sand above the water table. Limited data suggest that some loosening occurs in the sand below the water table. The results of the loading tests indicate that the geotechnical resistance - and notably the shaft resistance -is not sensitive to the number of auger rotations for the study conditions.