Prediction of breakage-induced couplings in unsaturated granular soils

This note addresses the interplay between particle breakage, water-retention curve and deformation processes. For this purpose, a continuum theory for unsaturated granular soils is used to capture the effects of loading and/or wetting in the grain-crushing regime. The theory provides a relation to express the air-entry value of the retention curve as a function of the degree of particle breakage, thus generating a coupled hydro-mechanical formulation. These features are exploited by deriving the incremental relations that govern the hydro-mechanical response. It is then shown that breakagedependent retention curves generate various coupling effects, such as the evolution of the degree of saturation along constant-suction paths and the pressure dependence of the wetting-collapse strains. Since these capabilities are an outcome of coupling terms derived from grain-scale considerations, these results suggest that microstructure-inspired models are important tools to capture the feedbacks between the macro-scale response and the evolution of micro-scale attributes, as well as to minimise the recourse to phenomenological assumptions.