Correlation between Axial Capacity of Driven Pile and Standard Penetration Test Blowcount-Paper

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The study develops correlations between the axial resistance of driven piles and Standard Penetration Test (SPT) blowcounts for Ontario soils, particularly variable glacial deposits. The authors analyzed 23 steel H-piles and concrete-filled pipe piles from the Ontario Ministry of Transportation’s database. Each pile had both compression and extraction load tests: extraction loads were used to estimate side resistance, while the difference between compression and extraction capacities was used to estimate tip resistance. Failure loads were identified using the De Beer criterion.<br /><br />The results indicate approximately linear relationships between average, uncorrected SPT N-values and unit side resistance. The reported trends are about 0.56 kPa per N-value for H-piles and 1.77 kPa per N-value for pipe piles. Unit tip resistance also increases approximately linearly with the SPT N-value at the pile tip, at about 163 kPa per N-value. The tip-resistance correlation was strong in this sample; side-resistance relationships showed greater scatter.<br /><br />Soil conditions affected side resistance: results were most consistent for piles in predominantly coarse-grained soils and least consistent in predominantly fine-grained soils. Tip resistance appeared less affected by soil type, though it may vary with pile geometry.<br /><br />The authors emphasize that these correlations are preliminary and specific to the study data. The SPT values were not corrected for energy and other test variations, and the database had limited or incomplete subsurface information. Estimates may also depend on the failure criterion, assumptions about pile plugging, and the limited measurements of pile deformation. Further work should address these uncertainties and could use more detailed site data and statistical or machine-learning methods to refine the correlations.

Keywords

axial resistance

driven piles

SPT blowcounts

Ontario soils

glacial deposits

side resistance

tip resistance

H-piles

pipe piles

De Beer criterion