A predictive framework for liquefaction instability

A predictive framework for flow liquefaction instabilities in sands is presented. A general criterion for liquefaction, based purely on the laws of physics, is presented and adapted to the important case of radial loading (e.g. triaxial, simple shear) using the Cambridge p′–q plane. Three important contributions are made in the paper. First, the instability concept is unified, and it is shown that the liquefaction criterion coincides with other instability criteria proposed previously. Second, the mechanics triggering liquefaction instabilities are highlighted using a simple instability criterion—underscoring the role of the material state and the underlying constitutive response. Third, the proposed framework is compared with experimental data from samples of sand under undrained triaxial compression, and it is shown that the proposed criterion correctly predicts the onset of liquefaction instability as a function of the sand state. Contractive samples encounter the so-called Lade's instability line, whereas dilative samples do not liquefy, but rather undergo a phase transformation. The predictive nature of the proposed procedure may open the door to better understanding, modelling, prediction and capture of catastrophic instabilities in saturated granular materials under general loading conditions.