Effects of particle morphology on the minimum and maximum void ratios of granular materials

The minimum and maximum void ratios ( e min and e max , respectively) of soils are intrinsic soil properties related to their particle size distribution (PSD) and particle shape. Different attempts have been made to predict these reference void ratios for cohesionless soils through the involved particle morphology. However, these predictive models do not handle flaky and elongated particles. Besides, these kinds of models just consider the particle shape throughout a two-dimensional analysis. In this current study, experimental work has been carried out on particles with five different geological and morphological properties and nine different gradations. The particle shape effect involves glass beads, rounded, angular, flaky, and elongated particles to expand both the range of particle sphericity and roundness. A wide range of particle sizes, including uniformly distributed, widely distributed, and upward concave graded soils were chosen. Particle sphericity and roundness were measured by micro CT images and image processing. Furthermore, a comprehensive database was gathered based on past experimental results from the literature. This database was used to derive the predictive equations for determining e min , e max , and the void ratio range ( e max - e min ), considering sphericity, roundness, and uniformity coefficient. The developed new formulas show good agreement with the current and past experimental results.