A Preliminary Study on the Correlations Between Drilling Parameters and Pile Capacities-Paper

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This preliminary study investigates whether investigative drilling (ID), a measurement-while-drilling method used in Australia, can help estimate pile capacity. Researchers compared drilling data with CAPWAP dynamic-testing results for eight bored piles at a southeast Australian transmission-line project.<br /><br />The analysis considered four original drilling measurements—penetration rate, feed pressure, rotation pressure, and flush pressure—and four derived parameters. Drilling data were averaged either along the pile shaft or within 1.5 pile diameters above and below the base, then compared with shaft resistance, toe resistance, and total bearing capacity per metre of pile length.<br /><br />Correlations with shaft and toe resistance were generally weak. Shaft-averaged parameters showed more promising relationships with total bearing capacity: penetration rate had a moderate negative correlation (r = −0.52), which improved to r = 0.63 when its reciprocal was used. Base-averaged normalized feed pressure (Qt) also showed a moderate correlation with bearing capacity (r = 0.47). By contrast, normalized rotation pressure (Fr) produced counterintuitive results, suggesting that the normalization method may not suit drilling data or that the small dataset affected the findings.<br /><br />The results suggest that continuous drilling measurements from investigation boreholes could support efficient, cost-effective early estimates of pile capacity. However, the study is preliminary: it includes only eight piles, and its correlations do not establish reliable predictive equations. Validation with larger datasets and further study of drilling mechanics, pile load transfer, and CAPWAP capacity estimates are needed.

Keywords

investigative drilling

pile capacity

bored piles

CAPWAP

dynamic testing

shaft resistance

toe resistance

bearing capacity

drilling measurements

correlation analysis