Constitutive modelling of compaction localisation in porous sandstones

• A new approach to modelling compaction localisation in sandstones is proposed.
• The approach possesses links between compaction band behaviour and the macro stress.
• Size effects induced by compaction localisation are properly captured at the constitutive level.

Porous sandstones exhibit localised modes of failure in the form of shear or compaction bands. In particular, shear localisation is associated with brittle behaviour under low confining pressures, while under increasing confining pressures, their failure gradually becomes more ductile with the onset and propagation of compaction bands. The orientation and size of these localisation bands vary with the loading and material properties. As a consequence, a correct description of the behaviour of porous sandstones must take into account all these characteristics of localised failure. As a departure from existing approaches that take into account the orientation of localisation band, we present in this study a new approach to incorporate both size and orientation of localisation zone in constitutive models for geomaterials. Based on this approach, a breakage mechanics constitutive model is enhanced with localised mode of failure and used for the post-localisation analysis of porous sandstones. The concepts together with technical details, and numerical results are presented to show the potentials of the new approach.