Regensburg 2010 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 13: Granular Matter/ Contact Dynamics II

DY 13.8: Talk

Wednesday, March 24, 2010, 11:30–11:45, H47

Shear Band Patterns in Biaxial Shear Tests of Granular Materials — •Thomas Stegmann, Janos Török, Lothar Brendel, and Dietrich E. Wolf — Faculty of Physics and CeNIDE, University of Duisburg-Essen, 47048 Duisburg, Germany

The theory of minimal dissipation identifies the position of the optimal shear band in granular materials by minimizing the dissipation rate. The strength of the theory comes forward in non-trivial scenarios as modified Couette cell [1] and granular refraction [2]. In true biaxial shear tests with frictionless walls the theory predicts ever changing shear band configurations that are optimal only for a given sample aspect ratio, with a constant angle equal to the Mohr-Coulomb angle and a constant macroscopic stress ratio [3]. A new quantity was introduced to identify shear bands in simulations which shows only partial agreement with the theory due to fluctuations and high degeneration of the optimum. This degeneracy can be decreased by introducing wall friction since there is only one shear band configuration which does not have any tangential velocity difference with the walls. It is expected that the stress ratio will be minimal at the optimal aspect ratio for this specific configuration. Apart from this point we expect to find shear band angles different from the Mohr-Coulomb angle. All theoretical results match very well with contact dynamics simulations.

[1] T. Unger et al., Phys. Rev. Lett. 92, 214301 (2004).

[2] T. Unger, Phys. Rev. Lett. 97, 018301 (2007).

[3] J. Török et. al. in Powders and Grains 2009, Melville NY, p. 417