An Improved Technique for Evaluating the CPT Friction Ratio by

iABSTRACT This report examines a statistical technique known as the cross-correlation function (CCF) for determining the shift distance associated with the cone penetration test (CPT). When evaluating the friction ratio, FR ( = fs/qc), for soil classification purposes, it is essential that the measured values of qc and fs are shifted relative to one another because of the depth discrepancy between the cone and the friction sleeve. Generally, the shift distance is estimated by means of empirical and subjective methods. Using a series of case studies, this report demonstrates that the CCF is a very useful and objective technique for estimating the shift distance. In addition, a phenomenon, associated with sleeve friction measurements which is related to elastic rebound of clay soils, is discussed. Finally, in iterative technique is proposed for determining the layering of a soil profile based on the CPT. ACKNOWLEDGMENTS The authors wish to acknowledge the Department of Transport, in particular, R. Washyn, R. Herraman and I. Forrester, for the use of the Department’s drilling rigs and technical staff, in carrying out the research at the South Parklands site and The City of Adelaide, and in particular, A. A. Taylor and M. Underhill, for providing access to this site. The authors also acknowledge Australian National, and in particular P. Gaskill, for their assistance and access to the Keswick site. Furthermore, the authors would like to thank the technical staff of th