Tailings dam failures are one of the most destructive phenomena, both in terms of number of victims and of generated environmental impact. Over the years, different causes have been identified, with flow liquefaction being a prominent factor to consider when assessing the stability of tailings deposits. Due to the complexity of these events, numerical models are crucial for the analysis and design phases, where appropriate advanced soil constitutive models must be selected to reproduce the relevant features of the soil behaviour. In this paper, the Clay And Sand Model (CASM), originally proposed by Yu (1998) and later modified by Arroyo and Gens (2021) and Manica et al. (2021), has been adopted for the simulation of flow liquefaction of tailings deposits. The model incorporates the state parameter concept (Been and Jefferies, 1985) and has been implemented as a User-Defined Soil Model (UDSM) into the finite element code PLAXIS; thereby, it becomes generally applicable to a wide range of geotechnical applications. Due to its versatile yield surface and plastic potential formulations, CASM can be used to model the behaviour of a wide range of soils, from fine-grained (e.g., clays) to coarser-grained soils (e.g., silts and sands). This paper shows the capability of the model, as well as the robustness of the finite element formulation, to reproduce the soil flow liquefaction observed in boundary value problems.