Improving the capacity predictions of drilled displacement piles through the use of pile installation data-Paper

Paper

Pdf Summary

The study investigates whether measurement-while-drilling (MWD) data can help predict the axial capacity of drilled displacement piles (DDPs). Researchers analyzed installation records and static load tests for 32 piles across 10 sites in the United States and Europe. MWD measurements included penetration speed and drilling pressure, which were combined into an installation-effort measure.<br /><br />A single cumulative installation-effort value was not a reliable predictor of capacity. Piles with similar total effort could have substantially different capacities, while piles with different effort could perform similarly. The authors attribute this variability partly to soil conditions, pile geometry, installation practices, and whether capacity comes mainly from shaft friction or toe resistance. A cumulative total also obscures where along the pile installation effort occurred.<br /><br />To address this limitation, the authors separated effort along the shaft from effort near the pile toe, defining the toe zone as extending four pile diameters above the tip. A regression model developed from three representative piles gave the toe-zone effort greater weight than shaft effort and predicted their measured capacities within 5%. The authors emphasize that this result is preliminary: the model was fitted to only three cases and is not yet suitable for general design use.<br /><br />The findings suggest that MWD records could support real-time capacity estimation, but reliable predictions will require more than a simple sum of installation data. Future models should distinguish shaft and toe contributions and incorporate geotechnical information, site variability, pile and tool characteristics, and installation conditions. The authors plan to expand the database and refine the approach for broader application.

Keywords

measurement-while-drilling

MWD

drilled displacement piles

axial capacity

installation effort

static load tests

toe zone

shaft friction

toe resistance

capacity prediction