Why is there a discrepancy in shear wave velocity – cone tip resistance (Vs–qc) correlations’ trends with respect to grain size?

Abstract

Although many regression equations of cone penetration test tip resistance, qc-CPT, versus shear wave velocity, Vs, are available in the literature resulting from a substantial research effort in this topic area, the outcome of these research efforts with respect to the influence of grain size on the Vs–qc correlations is in fact inconclusive because some of the suggested relationships, in common use today, either utilize irrelevant parameters or they are rather crude approximations of the Vs–qc trend over a wide range of grain sizes. A closer examination of this effect would be important for better assessment of the reliability and limitations of the proposed correlations. This note discusses the plausible reasons for the inconsistency in the existing Vs–qc correlations with respect to grain size through a detailed comparison of two well-known discrepant correlations referring to comparable experimental and field data. This note then goes further in its contribution to the practice of geotechnics by providing some useful recommendations to be considered in the prospective construction of Vs–qc correlations, especially when particle characteristics are taken into account.