Fractal crushing of granular materials under confined compression at different strain rates

Quasi-static and dynamic compression experiments are conducted on quartz sand, to study the stress-induced gradation evolution of granular materials under confined comminution. The particle size distributions obtained from laser diffractometry show three regimes, and the second regime is found to satisfy a power law or fractal distribution. The fractal dimension increases exponentially/linearly with increasing stress breakage extent, indicating an increasingly sophisticated packing geometry due to increasing fragmentation and fractal arrangement of particles. The fractal dimension, and normalized characteristic size of particles both exhibit generality, the asymptotic values of which are independent of loading rates. Particle size distributions with these three regimes have also been revealed in discrete element modeling. The third regime, mainly for fine particles, is attributed to the existence of a crushing size limit. The transition particle size between the second and third regime decreases significantly when the crushing size limit is reduced. (C) 2017 Published by Elsevier Ltd.