This work was carried out in the framework of a larger project devoted
to the micro-mechanical modeling of clayey soils by means of discrete element
simulations. Here, we study the rheology and microstructure of granular media
composed of platy particles. The particles are three-dimensional square plates,
approximated as spheropolyhedra. Several samples composed of particles of
different levels of platyness (related to the ratio of length to thickness) were
numerically prepared and sheared up to large deformations. Specifically, we
revisit and analyze in detail an ordering phenomenon described briefly in a
previous paper [1] and investigate its consequences in terms of the alignment of
particles and cluster formation. We find that particle alignment is strongly
enhanced by the degree of platyness and leads to the formation of face-connected
clusters. Due to dynamics, this spontaneous clustering is a robust characteristic of
granular systems composed of platy particles even in the absence of attraction
forces.