American Society of Civil Engineers

Unit Skin Friction from the Standard Penetration Test Supplemented with the Measurement of Torque

by Shawn P. Kelley, A.M.ASCE, (Post Doctoral Res. Assoc., Dept. of Civ. and Envir. Engrg., Univ. of Massachusetts, Amherst, MA 01003. E-mail: and Alan J. Lutenegger, M.ASCE, (Prof. and Head, Dept. of Civ. and Envir. Engrg., Univ. of Massachusetts, Amherst, MA 01003)

Journal of Geotechnical and Geoenvironmental Engineering, Vol. 130, No. 5, May 2004, pp. 540-543, (doi:

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Document type: Technical Note
Abstract: The standard penetration test (SPT) supplemented with the measurement of torque (SPT-T) may be used to obtain a direct measurement of unit skin friction (fs) between the sampler and the surrounding soil. The test is performed after the standard SPT procedure and does not compromise conventional SPT results. In order to perform the SPT-T, the split-barrel sampler is rotated after driving the ASTM specified distance and the maximum torque is measured using a calibrated torque wrench or transducer mounted to the top of the drill string. The measured torque is used along with the known geometry of the split-barrel sampler to determine a value of unit skin friction. SPT-T test results at 12 sites are presented. The results also show that the unit skin friction values obtained from the SPT-T generally correlate well with SPT N60 values. The results may be valuable for making preliminary estimates of unit skin friction for driven piles and provide some rationale for reported correlations between N60 and skin friction from piles.

ASCE Subject Headings:
Penetration tests
Skin friction
Test procedures
Soil strength
Soil tests