Elastoplastic stress-strain model for granular material based on static hypothesis

A micromechanics approach of elasto-plastic stress-strain model for granular material based on static hypothesis is developed. Perceiving granular material as a collection of particles, the proposed stress-strain model takes into account the discrete nature of granular material. Microstructure of granular material has significant effects on the macro-scale constitutive behavior. To study a heterogeneous granular material with randomly packed particles, a suitable model for characterizing microstructure is essential. The Delaunay cells are investigated and used to characterize the microstructure of granular material in this study. The overall stress-strain relationship of heterogeneous medium is sensitive to the properties of its constituents. Therefore, the distribution of heterogeneous stress and strain fields in granular material is important for predicting the constitutive relationship. In this study, the heterogeneous stress and strain fields of granular material is investigated using a method of Distributive tensor, taking into account the interactions between the constituent elements. The method of Distributive tensor for heterogeneous stress and strain fields is evaluated in detail by finite element method for continuum material and by computer simulation for discrete granular material. In this study, a static hypothesis that delineates the distribution of forces at inter-particle contacts in the system of discrete particles is proposed. Based on static hypothesis, the stress-strain relationship of granular material under elastic condition can be derived in closed-form solution for granular material with anisotropic packing structure. Packing structure can be characterized by a fabric tensor representing the orientation distribution of inter-particle contact. The static hypothesis is implemented to develop stress-strain relationship that covers plastic deformation. The developed elasto-plastic stress-strain model for granular material is evaluated by experimental tests on rod assembly and sand