Numerical modeling of permeability evolution based on degradation approach during progressive failure of brittle rocks

The permeability evolution of rock during the progressive failure process is described. In combination with the strength degradation index, the degradation formulas of s and a, which are dependent on the plastic confining strain component, the material constants of Hoek–Brown failure criterion are presented, and a modified elemental scale elastic–brittle–plastic constitutive model of rock is established. The relationship between volumetric strain and permeability through tri-axial compression is investigated. Based on the above, a permeability evolution model is established. The model incorporates confining pressure-dependent degradation of strength, dilatancy and corresponding permeability evolution. The model is implemented in FLAC by the FISH function method. The permeability evolution behavior of rock is investigated during the progressive failure process in a numerical case. The results show that the model is capable of reproducing, and allowing visualization of a range of hydro-mechanical responses of rock. The effects of confining pressure on degradation of strength, dilatancy and permeability evolution are also reflected.