Packings of irregular polyhedral particles: strength, structure and effects of angularity

E Azéma, F Radjaï and F Dubois

We present a systematic numerical investigation of the shear strength and structure of granular packings composed of irregular polyhedral particles. The angularity of the particles is varied by increasing the number of faces from 8 (octahedron-like shape) to 596. The shear strength increases with angularity up to a maximum value and saturates as the particles become more angular (below 46 faces). This finding extends the results of a previous study of regular polygons in two dimensions to irregular polyhedra in three dimensions. We also find that the packing fraction increases with angularity to a peak value but declines for more angular particles. We analyze the connectivity and anisotropy of the contact network and show that the increase of the shear strength with angularity is due to a net increase of fabric and force anisotropies but at higher particle angularity a rapid fall-off of the fabric anisotropy is compensated by an increase of force anisotropy, leading thus to the saturation of shear strength.


Weak (red) and Strong (Gray) forces chains during tri-axial test

Forces chains supported by face-face (yellow), face-vertex (red), face-edge (blue) and edge-edge (green) contacts

Particle velocity in a portion of sample during tri-axial velocity