Role of the particle size and shape dispersion on stress transmission and strain energy storage

Discrete element modelling (DEM) analyses are conducted to quantify how the statistical dispersion of the particle morphology influences stress transmission and strain energy storage of granular materials. DEM samples are prepared with both linear and bimodal size distributions and compressed isotropically. In addition, mixtures of particle shapes are used by covering a wide range of aspect ratios. The DEM results indicate that the contact dynamics are influenced significantly by size dispersion, with fine particles in the system tending to not transmit stress. More elongated particles are found to gain more contacts and substantially contribute to stress transmission. To rationalise these phenomenological findings, the results are interpreted in terms of the elastic strain energy characteristics of the DEM samples, by treating the latter as elastic granular continua. The analysis reveals that the fraction of strain energy stored in the particle fractions scales linearly with the particle size only at relatively narrow size dispersion, thus underscoring the need for corrective factors dependent on dispersion metrics (e.g. the coefficient of uniformity). A similar concept is examined also with reference to shape fractions, showing that a scaling relation based on the surface area of the particles provides a satisfactory corrective coefficient to account for non-spherical shapes.