Abstract
By means of 2D Contact Dynamics simulations, we explored the effects of the shape and size span of the grain size distribution (GSD) on the microstructure of a sheared granular packing, in terms of its packing fraction and the connectivity of its contact network. We focused on GSDs that can be represented by a power law, which are widely used in several engineering and industrial contexts. The interest in power law GSDs originates in the works of Fuller and Thompson in 1907 and 1919, in which it was found that a maximum density is obtained for a power law GSD with an exponent of 0.5. This disagrees with recent DEM results where the densest packing is obtained for linear cumulative volume distributions. In order to explore this discrepancy, we performed systematic simulations in which we varied both the size span (the ratio between the largest and the smallest diameter) and the exponent (shape) of the distribution. We find that the exponent equal to 0.5 produces the highest density for all size spans. Furthermore, the proportion of rattlers and coordination were also analyzed, showing that the system’s connectivity is strongly affected by both the size span and the shape of the distribution.
Highlights
It is well known that the grain size distribution plays an important role on the dynamics of granular materials
It is of paramount importance to choose the appropriate grain size distribution (GSD) when the material’s design targets some specific property, as it is done for the granular phase of composite materials such as Portland and asphalt concrete, or in the granular bases in roadways pavements
Large size spans are characterized by a disordered structure and by a higher proportion of rattlers
Summary
It is well known that the grain size distribution (or polydispersity) plays an important role on the dynamics of granular materials. Polydispersity strongly affects the material’s packing fraction, which in turn affects its mechanical response. It is of paramount importance to choose the appropriate grain size distribution (GSD) when the material’s design targets some specific property, as it is done for the granular phase of composite materials such as Portland and asphalt concrete, or in the granular bases in roadways pavements. The first experimental works are probably those of Fuller and Thompson in 1907 [1] and Taylor in 1919 [2]. Fuller and Thompson found that the optimal GSD (i.e., that with the highest density) is the one for which the cumulative volume distribution is described by ρ = (d/dmax)0.5,
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