Phenotypic Trait of Particle Geometries

Abstract

People of a race appear different but share a 'phenotypic trait' due to a common genetic origin. Mineral particles are like humans: they appear different despite having a same geological origin. Then, do the particles have some sort of 'phenotypic trait' in the geometries as we do? How can we characterize the phenotypic trait of particle geometries? This paper discusses a new perspective on how the phenotypic trait can be discovered in the particle geometries and how the 'variation' and 'average' of the geometry can be quantified. The key idea is using the power-law between particle surface-area-to-volume ratio ($A/V$) and the particle volume ($V$) that uncovers the phenotypic trait in terms of $α$ and $β^*$: From the log-transformed relation of $V = (A/V)^α {\times} β^*$, the power value $α$ represents the relation between shape and size, while the term $β^*$ (evaluated by fixing $α$ = -3) informs the angularity of the average shape in the granular material. In other words, $α$ represents the 'variation' of the geometry while $β^*$ is concerned with the 'average' geometry of a granular material. Furthermore, this study finds that $A/V$ and $V$ can be also used to characterize individual particle shape in terms of Wadell's true Sphericity ($S$). This paper also revisits the $M = A/V {\times} L/6$ concept originally introduced by Su et al. (2020) and finds the shape index $M$ is an extended form of $S$ providing additional information about the particle elongation. Therefore, the proposed method using $A/V$ and $V$ provides a unified approach that can characterize the particle geometry at multiple scales from granular material to a single particle. Ref.: Su, Y.F., Bhattacharya, S., Lee, S.J., Lee, C.H., Shin, M.: A new interpretation of three-dimensional particle geometry: M-A-V-L. Transp. Geotech. 23, 100328 (2020).