Analysis of an Image-Based Method to Quantify the Size and Shape of Sand Particles

Sand response depends on particle morphology (size and shape). In geotechnical research and practice, size is typically assessed by sieve analysis and particle shapes are qualitatively described. Technological developments mean that digital images of sand particles can easily be obtained, enabling shape to be quantified. The complexity associated with many digital image analysis algorithms seems to have restricted their use to fundamental research studies. This study introduces a pragmatic approach for quantitative shape analysis that has the potential to be broadly adopted in geotechnical engineering research and practice. The approach generates three shape measures (convexity, sphericity, and aspect ratio) that can easily be calculated from digital images. Following an analysis of these shape measures and the imaging method used here, a database of 36 sands, including many of the sands commonly used in geotechnical research, is presented. The subjective nature of qualitative description is clear from the discrepancies that were found in published shape assessments of these sands. Convexity, sphericity, and aspect ratio data for each of the 36 sands are presented. The relevance of these parameters to geotechnical engineering is established by comparing them with widely used qualitative descriptions.