Localised failure is the dominant mode of failure of geomaterials. This mode of failure includes tensile cracking, shear banding and compaction banding. In such cases, two regions, the localisation band and its surrounding, undergo two distinct responses that should be considered in the description of the behaviour of a volume element containing a localisation band. Inelastic behaviour of this volume element is dominated by that inside the localisation band, and under the same stress conditions both geometrical and mechanical properties of the localisation band is theoretically invariant with the size of the volume element containing it. As a consequence, it has been well known that the behaviour of a volume element undergoing localised failure is size-dependent, and describing it using a single stress-strain relationship is inadequate, if not totally incorrect. In triaxial tests, the onset of localised failure marks the start of a Boundary Value Problem (BVP), instead of “material” tests for characterisation of material behaviour. Can we obtain these two distinct responses inside and outside the localization band from standard triaxial tests? We will provide an answer to this question in this study, using a framework that allows better descriptions of the behaviour a volume element undergoing localised failure.