Résumé
Using three-periodic particle dynamics simulations, we investigate the microstructure of isotropic dense and loose packings of dodecahedral and spherical particles for different values of friction coefficient between particles. We also analyze the evolution of shear strength, packing fraction, particle connectivity, and anisotropy parameters under quasi-static triaxial compression. Our findings reveal that dodecahedral particles exhibit a wider range of packing fractions and a greater proportion of floating particles than spheres, highlighting the influence of interlocking and arching in these assemblies. The stress ratio, defined as the ratio of stress deviator to average stress, is nonzero even at zero friction and reaches higher values in dodecahedral packings compared to spherical ones. It increases with friction coefficient and eventually levels off at large friction coefficients. We show that the evolution of fabric and force anisotropies is strongly affected by friction coefficient and particle shape. Qualitative new features arising from non-spherical particle shape include (1) an enhanced ortho-radial force anisotropy, resulting from the combined effects of friction mobilization and the projection of normal forces on the branch vectors joining particle centers, (2) a negative branch vector length anisotropy, due to the alignment of face-to-face contacts with the compression axis, and (3) the distinct role of triple contacts in amplifying force anisotropy. Our findings suggest that the higher shear strength of packings of dodecahedral particles does not stem from a fundamentally different organization of the contact network, but rather from local force balance mechanisms induced by particle geometry. The stability of face-face contacts and their alignment with strong force chains account for the enhanced force anisotropy and shear strength observed in dodecahedral packings.