Reliability and applicability of the Krumbein-Sloss chart for estimating geomechanical properties in sands

Abstract This paper describes the reliability of the Krumbein-Sloss chart in estimating the particle shape parameter. Despite its simplicity and subjectivity in choosing roundness and sphericity, its applicability has not yet been completely validated. We compare the computed shape parameters of four different sands from 2D microscopic images with estimated values from the chart by a questionnaire study. The survey results show that the roundness and sphericity tend to be overestimated and underestimated, respectively, regardless of the participants' expertise on shape analysis. We validate the reliability of a previous regression in literature for extreme void ratios and newly propose the correlation of critical state void ratio based on roundness and particle gradation. It underscores that the Krumbein-Sloss chart based estimation can be statistically and partially reliable and still applicable in not only estimating shape parameters and but also correlating them with geotechnical properties.