Model methodology for studying crushing of unbound granular materials during compaction

A fracture and abrasion model is used in order to understand and visualize the evolution of crushing resulting from compression and shear in unbound granular materials. Modelling was done using numerical simulation with the discrete element method in two dimensions in which each particle in the granular material is represented by a disc. The particle fragmentation criterion is defined on the bases of grain fracturing under diametric compression, and it is estimated as a function of material properties using an adaptation of Weibull's statistical theory for fracturing of brittle materials. Stresses in discs are measured using numerical modelling in order to evaluate particle crushing in soils subjected to loads, defining the failure criterion on an individual particle subjected to an arbitrary set of contact forces. This procedure approximates the stress levels inside the grain through a simple analysis which take into account the magnitude, location, and number of contact forces on the particle. This model was validated with gyratory compaction tests in the laboratory with granular materials extracted from three locations near Bogotá, Colombia. Good agreement between the results of the model and laboratory tests was achieved.