Particle fracture regimes from impact simulations.

We introduce an approach to particle breakage, wherein the particle is modeled as an aggregate of polyhedral cells with their common surfaces governed by the Griffith criterion of fracture. This model is implemented within a discrete element code to simulate and analyze the breakage behavior of a single particle impacting a rigid plane. We find that fracture dynamics involves three distinct regimes as a function of the normalized impact energy ω.

Emergence of Shear Bands in Confined Granular Systems: Singularity of the -Statistics.

The statistics of grain displacements probability distribution function () during the shear of a granular medium displays an unusual dependence with the shear increment upscaling as recently evinced (see "experimental validation of a nonextensive scaling law in confined granular media"). Basically, the of grain displacements has clear nonextensive (-Gaussian) features at small scales, but approaches to Gaussian characteristics at large shear window scales-the ranulence effect. Here, we extend this analysis studying a larger system (more grains considered in the experimental setup), which exhibits a severe shear band fault during the macroscopic straining.

Experimental Validation of a Nonextensive Scaling Law in Confined Granular Media.

In this Letter, we address the relationship between the statistical fluctuations of grain displacements for a full quasistatic plane shear experiment, and the corresponding anomalous diffusion exponent α. We experimentally validate a particular case of the Tsallis-Bukman scaling law, α=2/(3-q), where q is obtained by fitting the probability density function (PDF) of the displacement fluctuations with a q-Gaussian distribution, and the diffusion exponent is measured independently during the experiment. Applying an original technique, we are able to evince a transition from an anomalous diffusion regime to a Brownian behavior as a function of the length of the strain window used to calculate the displacements of the grains.

Bond anisotropy and cohesion of wet granular materials.

We analyse the Coulomb cohesion of wet granular materials and its relationship with the distribution of capillary bonds between particles. We show that, within a harmonic representation of the bond and force states, the shear strength can be expressed as a state equation in terms of internal anisotropy parameters. This formulation involves a dependence of the shear strength on loading direction and leads to the fragile behaviour of granular materials.

Shear strength properties of wet granular materials.

We investigate shear strength properties of wet granular materials in the pendular state (i.e., the state where the liquid phase is discontinuous) as a function of water content.