2005/06/23 by P. Evesque
Physics and Astronomy · #cond-mat.soft
published as Poudres & Grains 14, 82-95, (2004), ISSN 1257-3957 · 14 pages + 1 page, 3 figures
arxiv created 2005/06/23 · arxiv updated 2009/12/01
The distribution P(F) of contact forces F in a homogeneous isotropic disordered granular sample subject to uniform triaxial stress field is studied using a model where forces propagate and collide. Collisions occur at grain and obey given rules which allow satisfying local static equilibrium. Analogy with Boltzmann's equation of density evolution is drawn and used to derive the parameters that control the distribution Ps(F) of contact forces F in the stationary state in case of a packing of mono-disperse spheres. Using symmetry argument and mean field approximation, it is found that stationarity is achieved when the density Ps(F) of force can be written as the product of exponentials of quantities whose sums are preserved during collisions. This introduces 3 parameters in 2d and 6 in 3d which are the mean force components Fxo, Fyo, Fzo, and the mean torques of the force on a grain Mxo, Myo, Mzo >. Astonishingly, it seems that the theory cannot include distribution of contact orientation implicitly. Extension of the model is possible with some care to case of anisotropic packing. Pacs # : 5.40 ; 45.70 ; 62.20 ; 83.70.Fn