“…1,2,4,5,7,8,18,19 Micromechanical investigations have demonstrated that global instabilities in granular materials originate from the rearrangements of grain loops and the collapses of force chains. 1,10,[20][21][22][23][24][25][26][27][28][29] Given these findings, two questions can be raised: What criterion can be used to characterise the instabilities at various scales and how is the extent of global instability related to elementary and microstructural instabilities in granular materials? In current numerical studies based on phenomenological constitutive relations with different methods, it appears that neither the finite element method 18,30,31 nor the second gradient theory 32,33 can consider in a simultaneous manner the instabilities of granular materials at the interparticle level, the laboratory scale, and the engineering scale.…”