This paper discusses a continuum approach to track the evolution of permeability in granular materials subjected to high-pressure compaction and grain breakage. To cope with a range of loading configurations and account for changes in grain size distribution, the Breakage Mechanics theory is used. In addition, the model predictions are linked to a Kozeny equation to evaluate the drop of hydraulic conductivity resulting from the simultaneous loss of porosity and growth of surface area. Compression/flow experiments available in the literature for different granular media are used, with the goal to validate the selected methodology for solids mimicking poorly consolidated reservoir rocks. A good agreement between model predictions and experiments is found, thus stressing the benefits of adopting microstructure-based constitutive laws for hydro-mechanical analyses of coupled geomechanical problems.