The Challenge

To develop breach outflow hydrographs for tailings dam breach analysis, engineers traditionally define breach geometry and related parameters based on empirical equations developed from water dam failures. Tailings dams, however, have a higher concentration of solids, and failure progression is controlled by non-Newtonian flow behavior, meaning this approach can introduce significant uncertainty by misrepresenting outflow dynamics.

To comply with standards and recommendations from the Global Industry Standard on Tailings Management (GISTM), the Canadian Dam Association (CDA), and the International Commission of Large Dams (ICOLD), operators need more defensible approaches that accurately represent geotechnical conditions and failure mechanisms specific to TSFs. This study contributes to this aim through a numerical modeling approach for tailings dam breach analysis based on traceable, physics-based methodology as opposed to the current practice based on empirical methods.

The Solution

Geosyntec Mining developed a three-dimensional numerical model of Dam I of the Brumadinho tailings facility using ITASCA’s MPoint3D software, which combines the Finite Difference Method (FDM) and the Material Point Method (MPM) within a single computational framework.

The model incorporated detailed dam geometry and topography, water table data, and in-situ stress conditions. The Mohr-Coulomb constitutive model was applied for all materials. The goal of this model was to capture post-failure runout dynamics, not failure initiation, so all materials are assumed to have residual liquefied shear strength to represent their post-liquefaction state.

Discharge and mobilized volume emerged from the simulated geomechanical response of the tailings and embankment materials to develop the breach outflow hydrograph.

Why the Material Point Method?

The Material Point Method, which is the foundation of MPoint, is particularly well suited for extreme deformation problems involving material failure, liquefaction, runout analysis, and post-failure material movement: all key elements of tailings dam breach analysis. In fact, the National Academies of Sciences has recognized the application of MPM in dam breach and failure assessments as an advancement to traditional modeling methods (NASEM, 2021).

In MPM, moveable material points carry stress, strain, density, and strength information and are mapped on a temporary background grid each step to compute stresses and strains. This approach enables continuous simulation of large deformation without the mesh distortion issues that often halt simulation in traditional numerical methods.

MPoint can simulate breach initiation, progression of failure, and downstream material release within a single model, providing a streamlined framework for failure analysis of complex systems like tailings storage facilities.

Results

The MPM simulation successfully reproduced key characteristics of the Brumadinho failure, including the rapid loss of stability, progression of large deformation, and flow of the liquefied tailings. The breach hydrograph can then be developed directly from the evolving mechanics of the failure process rather than from assigned breach parameters as in traditional methods, which improves traceability to increase confidence in the analysis.

The base-case model predicted:

• Peak discharge of approximately 133,000 m³/s
• Mobilized mass of approximately 4.37 Mm³
• Failure duration and surge velocities consistent with documented observations

A comparison of the hydrographs developed from this study and a study by Lumbroso et al. (2021), which was based on data calibrated to match the reported characteristics of the failure, highlights the differences in the two modeling approaches. In this study, the estimated peak discharge was 48% higher than in the calibrated hydrograph, followed by a rapid decline, indicating that the bulk of mobilized material quickly exited the TSF, matching the observed timing of failure.

Sensitivity Analysis

Additional simulations evaluated the effect of residual undrained shear strength ratios on breach behavior. Sensitivity studies with values ranging from 0.01 to 0.06 showed that decreasing residual strength significantly affects breach severity through increased peak discharge and mobilized volume. Meanwhile, the timing of peak discharge and initial velocity remained relatively consistent across cases, indicating that the geometry of the facility and gravitational forces are the controlling factors.

The MPM approach used in this study provides results that are based on the large-deformation physics governing the failure that are directly traceable to geotechnical characterization of the site, rather than calibrated data. The methodology improves reliability in tailings dam breach assessments and consequence evaluations, providing valuable information for emergency preparedness.

Benefits of the Material Point Method Approach

By leveraging ITASCA’s MPM software MPoint, Geosyntec Mining developed a workflow that:

• Reduces reliance on empirical breach assumptions
• Links breach predictions directly to geotechnical conditions
• Simulates failure initiation, breach development, and runout in a unified framework
• Provides transparent and defensible inputs for consequence assessments
• Supports alignment with current guidance and risk management frameworks for tailings facilities

Looking Forward

As regulators and operators place greater emphasis on tailings dam safety and risk management, advanced numerical methods are becoming increasingly important tools for understanding breach behavior. The Brumadinho case study demonstrates how Material Point Method software like MPoint can provide a credible, physics-based alternative to conventional breach hydrograph estimation methods while offering deeper insight into the mechanics governing large-scale tailings failures.

MPoint let us simulate breach initiation and runout in a single framework, so the hydrograph comes out of the mechanics of the failure rather than an empirical assumption. For our clients, that means a breach analysis they can trace back to the geotechnical characterisation of their facility.

Nicolas Pereira, Senior Geotechnical Engineer, and Sudheer Prabhu, Geotechnical Engineer, Geosyntec Mining

About Geosyntec Mining

Geosyntec Mining is a specialist tailings and dam engineering consultancy with offices in Australia. The team provides tailings storage facility design, dam breach and consequence assessment, Engineer of Record services, and advanced numerical modelling to mining clients in Australia and internationally. Learn more at https://geosyntec.com.au/.

References

• Lumbroso, D., Davison, M., Body, R., and Petkovsek, G. (2021). Modelling the Brumadinho tailings dam failure, the subsequent loss of life and how it could have been reduced. Natural Hazards and Earth System Sciences, 21(1), 21-37.
• National Academies of Sciences, Engineering, and Medicine (NASEM). (2021). State of the Art and Practice in the Assessment of Earthquake-Induced Soil Liquefaction and Its Consequences. The National Academies Press, Washington, DC.
• Pereira, N., Prabhu, S., Reid, D., Urbina, F, & Fanni, R. (2026). Tailings Dam Breach Hydrograph Modelling: MPM Application to the Brumadinho Failure. In Water, Energy, and Society: The Evolving Role of Dams in a Changing World (Proceedings, 94^th ICOLD Annual Meeting, Guadalajara, Mexico, May 2026). Note: Refers to MPoint as MPAC, an earlier version of the software while under development.