Self-organization, Localization of Shear Bands and Aging in Loose   Granular Materials
  We introduce a mesoscopic model for the formation and evolution of shear bands in loose granular media. Numerical simulations reveal that the system undergoes a non-trivial self-organization process which is governed by the motion of the shear band and the consequent restructuring of the material along it. High density regions are built up, progressively confining the shear bands in localized regions. This results in an inhomogeneous aging of the material with a very slow increase in the mean density, displaying an unusual glassy like system-size dependence. 
Janos Torok, Supriya Krishnamurthy, Janos Kertesz, Stephane Roux