Abstract

Some recent contributions of Discrete Element Modelling (DEM) to the understanding of the micromechanical origins of the quasi-static mechanical behaviour of model granular materials are briefly reviewed, with special attention to initial states resulting from different assembling processes, to pre-peak deformation and to elasticity. It is shown in particular that different assembling procedures can produce very different coordination numbers for the same density. Two types of strains are distinguished according to whether contact networks support load increments without instability and rearrangement. Type I strains directly result from material deformation in intergranular contact regions; they scale with elastic strains, even though they correspond to large stress increments that exceed by far the range of quasi-elastic response. Elastic moduli may be regarded as probing coordination numbers, stress and fabric anisotropy. Type II strains stem from microscopic instabilities in which contact networks break and repair, and their magnitude is controlled by packing geometry. The occurrence and implications of these different micromechanical origins of strains are discussed.