Calibration of Cone Factor in Cone Penetration Test for Evaluating the Undrained Shear Strength of Silty Clay

Cone penetration test often uses the cone factor to calculate the undrained shear strength of silty clay base on the cone tip resistance data, but the accurate determination of the cone factor is challenging due to its wide range of values. This study conducted a laboratory cone penetration test and vane shear test to investigate and calibrate the cone factor for evaluating the undrained shear strength of silty clay at various depths. The cone factor is first identified based on the laboratory cone penetration test and vane shear test, and it is compared with the cone factor generated from the cavity expansion theory. Cone factor calibration has been performed by integrating laboratory model tests with the cavity expansion method, unlike conventional approaches relying on singular methodologies. The proposed cone factor is validated by the in situ undrained shear strength of Shanghai silty clay based on the in situ cone penetration test data. The results indicate that the cone factor varies significantly, ranging from 3 to 27. The cone factor from laboratory results shows good agreement with that based on the cavity expansion method. The calibrated cone factor predicts reasonable undrained shear strength measured from in situ tests. The refining method enables ±30% accuracy in predicting field-measured undrained shear strength values, establishing region-specific guidelines for East China Sea investigations.