ABSTRACT
The mechanical behavior of granular materials is complex essentially due to their discrete nature. All the local phenomena (contacts between particles, local strain and sliding at contacts, particle rotations) and variables defined at particle scale depend on the particle array (internal structure) which evolves differently when subjected to different loading paths. One of the main difficulties when modeling the behavior of granular materials lies in the characterization and measurement of the evolution of their internal state for a given loading path. The main objective of this paper is (i) to analyze the evolution of the internal state of granular materials considering a meso-scale defined by a closed loop of particles in contact, and (ii) to analyze on this basis the behavior of the sample. The relevance of the meso-scale has already been studied in previous papers (e.g. Nguyen et al. 2009, Durán et al. 2010). In this paper, the numerical modeling of two loading paths is considered, a biaxial loading up to a given deformation followed by an unloading. These two loadings were performed from very different initial states, such that the influence of this initial state on the evolution of the internal state could be captured more precisely. This influence on the mechanical behavior of the granular material all along the two considered loadings was also analyzed.
