How to obtain hydro-mechanical responses inside the localisation zone from triaxial tests on partially saturated soils

Localised failure and the appearance of a localisation band are common in triaxial tests on soils, including partially saturated soils. In a classical analysis, stress–strain and suction–saturation degree in the post-localisation regime are usually considered as volume-averaged quantities of the soil specimen that includes the localisation zone and the bulk outside the zone. They are commonly used to validate classical constitutive models for partially saturated soils. However, this assumption is invalid in the post-localisation stage, where the inelastic response of the specimen is dominated by significant interactions between grain rearrangement and liquid redistribution inside the localisation band. In this paper the underlying localisation mechanisms are used for the correlation between constitutive modelling and experimental data involving coupled hydro-mechanical behaviour. This allows better interpretation of triaxial test data on partially saturated soils to obtain intrinsic hydro-mechanical behaviour inside the localisation zone. The advances of the proposed approach are elucidated through several results showing tight correlations between the interpretation of experimental data, parameter calibration and model validation.