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DY: Fachverband Dynamik und Statistische Physik

DY 31: Granular matter / contact dynamics II

DY 31.5: Talk

Friday, March 30, 2007, 11:15–11:30, H2

Macroscopic stress and strain distributions in sand piles — •Pradip Roul and Klaus Kassner — Institut für Theoretische Physik, Otto-von-Guericke-Universität Magdeburg, Postfach 4120, D-39016 Magdeburg

The stress distribution under a sand pile sometimes exhibits unusual features. Depending on characteristics such as the size distribution of grains but also the construction history of the aggregate, the pressure distribution may display a minimum or a maximum under the tip of the heap, with the former behaviour appearing counterintuitive. We performed numerical simulations generating two-dimensional ``sand piles'' from several thousand convex polygonal particles with varying shapes, sizes and corner numbers, using a discrete element approach based on soft particles. The pressure distribution regularly has a minimum under piles poured from a point source but does not show one, if the grains are poured from a line source. Calculations of the macroscopically averaged stress and strain tensors inside granular aggregates will be presented. Stress distributions are compared with the elasto-plastic theory of Cantelaube et al. It turns out that this theory describes the overall behaviour of the simulated sand piles well, if the relative size of the elastic and plastic regions is considered a free parameter. The prediction of this size itself by the theory is inaccurate.