Contact force network evolution in active earth pressure state of granular materials: photo-elastic tests and DEM

The paper deals with a quasi-static behaviour of cohesion-less granular material in active earth pressure state. Photo-elastic model tests on a rigid wall, translating out of the granular material, are analyzed. Grain crushing tests are used to estimate the range of contact forces during the model tests. Substitute granular material (low optical sensitivity glass granules) is employed. The focus is on the evolution of contact force network with deformation of granular material. The model tests are simulated using the discrete element method (DEM) to compare physical and numerical full-field force network structure and the maximum/minimum stress level. The same model geometry, loading scheme and grain size distribution, as in the model tests, are accepted in DEM simulations, although only a single layer of grains is modelled. DEM model correctly predicts the overall structure of the force network and its characteristic features, including localization. It also gives the stress level close to the experimental one and properly identifies the areas of phase transitions.