International audience ; Grain fragmentation is simulated by means of a three-dimensional discrete element approach calledbonded-cell method (BCM). In this method, grains and potential fragments may have any polyhedral shape andsize, capturing the geometrical complexity of brittle grain failure. As an application of this method, we presentthe uniaxial compaction of samples composed of several grains and we analyse the load-density relations, thegrain size evolution, and the failure mechanism within the grains. This numerical approach permitted us toanalyse the e↵ect of the grains internal strength on the macroscopic compaction behaviour and to study theevolution of the grain size distribution towards a power-law distribution as several experiments have shown inliterature. Finally, we present a brief micro-mechanical analysis on the failure modes within the grains, lettingus know the kind of stresses that prompts grain fragmentation.