Response of granular media near the jamming transition

Ellenbroek, W.G.

Many disordered materials display a so-called jamming transition between solid-like and fluid-like states. In this thesis, we investigate jamming in granular media by studying granular packings at various distances from the transition. In numerical model systems of spherical particles, the jamming transition has many features of a critical transition. Using the linear response of such packings to external perturbations, we shed new light on their critical behavior. We analyze various scaling relations in terms of the non-affine deformations of the packing, and identify a diverging length scale that determines beyond what scale these systems can be treated as a continuum. This length scale and various other properties are determined primarily by the number of contacts between grains in the system. In the second half of the thesis we investigate force networks in granular media using the recently developed Force Network Ensemble. We discuss the analytical properties of the ensemble,...Show moreMany disordered materials display a so-called jamming transition between solid-like and fluid-like states. In this thesis, we investigate jamming in granular media by studying granular packings at various distances from the transition. In numerical model systems of spherical particles, the jamming transition has many features of a critical transition. Using the linear response of such packings to external perturbations, we shed new light on their critical behavior. We analyze various scaling relations in terms of the non-affine deformations of the packing, and identify a diverging length scale that determines beyond what scale these systems can be treated as a continuum. This length scale and various other properties are determined primarily by the number of contacts between grains in the system. In the second half of the thesis we investigate force networks in granular media using the recently developed Force Network Ensemble. We discuss the analytical properties of the ensemble, and apply it to study granular media under shear stress, identifying upper bounds on the shear stress that cohesionless granular media can sustain.Show less

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Response of granular media near the jamming transition

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