Modelling localised failure in porous reservoir rocks using a continuum model with an embedded localisation band

The localised failure of highly porous rocks usually involves the size-dependent responses governed by the presence of planar bands in the form of compaction bands under high confinements. Deformations inside these bands induced by grain crushing are much higher than the surrounding host rock, making the rock structure inhomogeneous. This post-localisation mechanism is not able to be correctly captured by classical constitutive models for rocks due to the assumption of homogeneous deformation. The inhomogeneous behaviour can be addressed by our mechanism-based constitutive model in this paper, accounting for properties of the mesoscale localisation bands. In this model, the inclination and thickness of compaction bands are taken into account in kinematic enrichments to connect elastic responses outside and inelastic responses based on breakage mechanics theory inside them. The potential of the proposed approach is presented through several numerical examples, using triaxial tests on rocks.