Formulation and numerical implementation of a state parameter-based generalized plasticity model for mine tailings

Abstract

Mine tailings are rock flour that is generally deposited in tailings dams. When deposited in a loose and saturated state, the tailings are prone to flow liquefaction. Simulating the onset of liquefaction and the post-liquefaction behavior of tailings has therefore become an essential aspect in geotechnical engineering of tailings dams. Several analysis procedures have been developed to address this problem, most of them employing the state parameter ψ as the key indicator of material behavior. The use of numerical deformation modelling for addressing the onset of flow liquefaction is increasingly practiced. Therefore, constitutive models, which are based on the state parameter and can simulate a wide range of stress paths, are demanded by the industry. This paper presents the formulation of an extension of a generalized plasticity model that is based on the state parameter and that simulates liquefaction within a critical state framework. As such, it is attractive for modelling loose tailings. The model is extended to the general 3D stress space and implemented by using an implicit integration scheme as a user model in Plaxis. This paper describes the set up and calibration of the model based on a set of laboratory tests on tailings and includes a numerical exercise proving the consistency and robustness of the formulation.