The Effect of Particle Elongation on the Strength of Granular Materials

It has long been recognised that the macroscopic mechanical behaviour of a granular material depends on particle shape. However, a systematic investigation into particle shape is lacking. Particle shape is commonly split into the independent categories of form, angularity and roughness. The form of a particle can be quantified using the Longest (L), Intermediate (I) and Shortest (S) dimension of an equivalent scalene ellipsoid; two independent parameters of particle form are defined, termed platyness and elongation. We use DEM simulations with the Potential Particle Method to investigate the effect of particle form on the friction angle of a granular material at critical state. It is found that deviation of particle form from that of a sphere leads to higher angles of friction at critical state. It is argued that, to some extent, the higher critical state strength exhibited by non-spherical particles is due to form suppressing particle rotation and leading to increased interparticle sliding, a mechanism that in comparison requires more energy to be expended.