# Particle shape dependence in granular media

## CEGEO Group

This study has been done by the CEGEO collaborative group (scale change in geomaterials) see below for information about the authors.Particle shape is a key to the space-filling and strength properties of granular matter. We consider a shape parameter η describing the degree of distortion from a perfectly spherical shape. Encompassing most specific shape characteristics such as elongation, angularity and non- convexity, η is a low-order but generic parameter that we used in a numerical benchmark test for a systematic investigation of shape-dependence in sheared granular packings composed of particles of different shapes. We find that the shear strength is an increasing function of η with nearly the same trend for all shapes, the differences appearing thus to be of second order compared to η. We also observe a nontrivial behavior of packing fraction which, for all our simulated shapes, increases with η from the random close packing fraction for disks, reaches a peak considerably higher than that for disks, and subsequently declines as η is further increased. These findings suggest that a low-order description of particle shape accounts for the principal trends of packing fraction and shear strength. Hence, the effect of second-order shape parameters may be investigated by considering different shapes at the same level of η.

### Reference:

Particle shape dependence in 2D granular media

Baptiste Saint-Cyr; Szarf Krzysztof; Charles Voivret; Emilien Azema; Vincent Richefeu; Jean-Yves Delenne; Gael Combe; Nouguier-Lehon Cécile; Villard Pascal; Sornay Philippe; Chaze Marie; Franck Radjai

EPL, 2012, 98, pp. 4408