Modeling Hydraulic and Chemical Processes in Crushable Granular Materials

The paper presents a conceptual approach for capturing the interplay between multi-physical processes and the mechanism of particle breakage in granular geomaterials. The study addresses two specific processes in a separate fashion: (i) the interaction between granular solids and multiple pore fluids and (ii) the effect of mineral dissolution. In both cases, grain crushing is reproduced through the Breakage Mechanics theory. Couplings between mechanical and non-mechanical phenomena are reproduced via particle scale modeling. The role of partially saturated conditions is captured through the capillary theory, while simplified microscopic schemes are used to relate the evolution of the chemical state variables to changes in particle geometry. These consideration define scaling laws for each mechanism. The macroscopic implications of the two considered processes in terms of inelastic mechanical properties are finally derived through statistical homogenization. The analytical results disclose a relation between the hydro-chemical state variables and the yielding threshold under compressive stresses. At variance with prior formulations, such dependencies are obtained as emergent properties by advocating that the main contribution to the energy dissipation derives from the brittle breakage of the mineral compounds. These results stress the importance of identifying the microscopic physical processes that regulate inelastic deformation. For this reason, they can be a conceptual springboard for the development of micromechanically-based multi-physical models for granular media.