Stress Field Equations in Granular Solids - A Shift of Paradigm

Thursday, September 30, 2004 - 1:30pm - 2:20pm
Keller 3-180
Raphael Blumenfeld (University of Cambridge)
A key concept to the understanding of stress transmission in granular materials is the Marginally Rigid State and an experiment is described which establishes the relevance of this state. The MRS can be regarded as a critical point wherein a particular lengthscale diverges. Granular matter at the MRS is statically determinate (isostatic), obviating elasticity theory. A new isostaticity theory is formulated for stress transmission at the MRS. It explains the force chains, frequently observed in experiments, and makes it possible to predict their individual trajectories.

The insight from the static theory makes it possible to formulate a theory for the yield and failuer of granular solids and a new set of equations is presented for the flow of granular matter in this regime.