Liquefaction Instability Analysis Using Extended Mohr-Coulomb Model Under Axisymmetric Conditions

The study presents a theoretical analysis of liquefaction instability in sands using Extended Mohr Coulomb model. Experimental observations reported in the literature have indicated a deviation of instability onset from the well-known criteria based on second order work. Hence, in the present study the liquefaction instability analysis has been posed as a bifurcation problem to study the instability onset. The analysis considers liquefaction as a solid-fluid instability. The conditions for instability, perturbed velocity and pore pressure fields for axisymmetric conditions are adopted from previous research. Extended Mohr-Coulomb material model based on nonassociative flow rule is utilized in the analysis as it is capable of predicting typical sand behaviour. The onset of instability predicted from the analysis is compared with the experimental observations. Emergence of instabilities are studied along with the evolution of distortional strains to understand the suitability of the obtained predictions. Bifurcation analysis predicted the onset of instability before the peak of effective stress path. It was consistent with the evolution of plastic component of distortional strains.