Combining tomographic imaging and DEM simulations to investigate the structure of experimental sphere packings

We introduce and describe in detail a virtual laboratory'' platform to study granular materials by combining advanced image reconstruction techniques from computed X-ray micro tomography and discrete element method simulations. This platform allows us to directly access quantities such as forces at the grain contacts, which would be otherwise hard to measure experimentally. We apply this technique to the investigation of equal sized bead packings prepared experimentally by means of different methods, and covering a broad range of packing fractions from phi = 0.57 to phi = 0.64. Results concerning the number of contacts, the distribution of forces at contact and the relation of these quantities with local and global packing properties are presented and discussed. This combined approach is found to both offer the ability to improve on previous tomographic measurements of geometric properties of the packings, and to estimate other physical properties that are not available experimentally.