Interpretation of shear strength of cone penetrating in double layered clays considering the scale effect in centrifuge testing

Abstract

Cone penetration test (CPT) has been commonly applied as a site investigation tool and a laboratory measurement method in centrifuge tests to study soil properties. In this research, large deformation finite element (LDFE) analysis is utilized to realize the simulation of continuous cone penetration in two-layered clay deposits in centrifuge testing, with the aim of better interpreting the shear strength of cone penetration testing data. The numerical model is validated against previous published data, where good agreement is obtained. From LDFE results, it is concluded that for stiff-over-soft clay, the measured peak resistance in top layer is underestimated and the resistance curve in bottom layer is overestimated at the transitional depth where the stiff soil is trapped below the conical surface of cone. However, for soft-over-stiff clay, owing to the insufficient thickness for cone to reach its full resistance, the effect of top layer thickness needs to be considered. Finally, based on intensive numerical modeling results empirical formulae are proposed to quantify the prediction errors and to obtain a more accurate prediction for the soil profile using CPT data in centrifuge tests.