Pereira, N, Prabhu, SS, Purvance, M, Coetzee, C & Loffell, D 2025, 'Dam breach analysis of a closed facility using the Material Point Method', in S Knutsson, AB Fourie & M Tibbett (eds), Mine Closure 2025: Proceedings of the 18th International Conference on Mine Closure, Australian Centre for Geomechanics, Perth, pp. 1-11, https://doi.org/10.36487/ACG_repo/2515_45
(https://papers.acg.uwa.edu.au/p/2515_45_Prabhu/)
Abstract: The Global Industry Standard on Tailings Management (GISTM) has become a critical benchmark for tailings storage facilities (TSFs), driving mining companies to ensure compliance. This push intensified following the Brumadhino TSF failure with GISTM emphasising the need for accurate dam breach analysis (DBA) to assess potential risks, even after closure.
Traditional DBA models use rheological properties to characterise the flowability of tailings. However, due to high solids concentrations in closed TSFs, these models might not be representative. Tailings behave more like solids as saturation decreases after closure. Conventional DBA models may overestimate runout distances and underestimate inundation depth, potentially leading to costly, unnecessary mitigation and misallocation of resources.
The Material Point Method (MPM) is one of the techniques recommended by the Canadian Dam Association (CDA 2021) for conducting DBA. It incorporates geotechnical material properties and can be applied to closed facilities, potentially providing more realistic runout estimates. Additionally, MPM is capable of accounting for flow resistance from the embankment, unlike conventional approaches.
This paper presents a case study of a closed TSF using MPM, integrating credible failure modes from the failure modes and effect analysis and residual strength parameters to trigger runout. Additionally, a probabilistic sensitivity study was carried out to account for material strength variability to capture runout behaviour even under extreme conditions. The findings demonstrate that even with unrealistically low strength values for tailings, embankment, foundation and dam materials, the predicted runout distances are limited.
Insights from these models could optimise closure planning, inform more practical post-closure strategies, and improve understanding of failure impact potential. The results demonstrate that dam breach likelihood and tailings runout are highly sensitive to material strength assumptions, with full breach only occurring under extremely low-probability scenarios. Even in these cases, runout distances remained limited, highlighting the ability of the MPM approach to produce more physically representative outcomes, even under extreme conditions. These findings support a risk-informed framework for emergency preparedness and resource allocation, enhancing compliance with GISTM and promoting safer, more sustainable tailings management practices.

Keywords: Material Point Method, dam breach analysis