Field Scale Flow Modeling of Thixotropic Mine Tailings Using the Material Point Method

Abstract

Understanding free surface flow of mine tailings is necessary to plan deposition operations in tailings' storage facilities (TSF), and is important to predict the consequences of a dam break. Proper understanding of deposition operations has probably hindered adoption of alternative tailings technologies, wheras recent failures of tailings impoundments have had catastrophic consequences. Flow behavior is crucial to understand for effective risk mitigation. Tailings exhibit thixotropic properties-their behavior is a function of the material's stress history. A thixotropic constitutive model has been implemented into an open-source Material Point Method (MPM) framework. The results were validated with previous experimental data at laboratory scale and compared with Bingham rheology with good agreements. Large-scale simulations were done for 2D and 3D cases. The thixotropic model was able to model self-forming channels seen during field scale deposition, which Bingham rheology is unable to capture. Dam break events also scaled differently from laboratory scale experiments with thixotropy. This can possibly be an element that explains longer runouts then initially predicted with standard rheology.

Simulating 3D Tailings Dam Breach With Thixotropic Bifurcation Rheology using the Material Point Method

“…In such model, the viscosity of fluid varies based on the degree of structuration, and therefore has some capacity to simulate both the initial state of the tailings as well as the fully-sheared state. This work advances initial exploration of applying thixotropic rheology models to tailings flows conducted by Parent (2020).…”

“…This viscosity of the highly viscous form is calculated as the product between the coefficient 𝛼𝛼 and fully sheared viscosity 𝜂𝜂 0 , meanwhile the T parameter and exponent n from Coussot model does not participate in the calculation. The detailed constitutive model for Bingham relationship implemented in the MPM software Uintah is fully described in the appendix A of Parent (2020), the general introduction of the Uintah is included in next section.…”

“…The numerical simulation results using volume of fluid method shows that both rheology relationship is capable to produce results that match the field observation data up to 73% while imposing no-slip boundary condition, and the match can improve to 97% if a high viscosity is imposed on un-yielded region during their simulations. (Parent, 2020).…”

“…(MPM) component with a modified constitutive model file created by Etienne Parent(Parent, 2020). The Uintah software is installed on Carleton University's computation server, a 16 core Intel Xeon based Linux system, accessed through remote connection app that support SSH connections, i.e.…”