A Two-Fluid Simulation of Tailings Dam Breaching
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TECHNICAL ARTICLE
A Two‑Fluid Simulation of Tailings Dam Breaching Gregor Petkovšek1 · Mohamed Ahmed Ali Mohamed Hassan1 · Darren Lumbroso1 · Marta Roca Collell1 Received: 21 January 2020 / Accepted: 17 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract This paper presents the development and application of a dam breach model, EMBREA-MUD, which is suitable for tailings dams. One of the common failure modes for these structures is breaching due to overtopping, which together with the flow of liquefied tailings, is simulated by the proposed model. The model simultaneously computes the outflow of water and tailings from a tailings storage facility and the corresponding growth of the breach opening. Tailings outflows are represented by a separate non-Newtonian viscous layer, which together with a water layer, represent the two fluid components of the model. The third component represents dam material that can be eroded by the shear forces exerted by either water or mud. The water layer also exerts dynamic and erosional forces and can transport solids eroded from either the mud or dam layer. The model was verified against laboratory cases as well as two field cases reported in the literature, the failures of the Mount Polley tailings dam in Canada in 2015 and the Merriespruit dam in South Africa in 1994. The model results agreed well with the recorded narrative of the events, although in the latter case, careful calibration of one of the model parameters was necessary to obtain a good match. Keywords Dam failure · Overtopping · Non-Newtonian fluid · Numerical modelling · Tailings
Introduction The consequences of a tailings dam failure can be catastrophic. A recent reminder of this is the failure of Dam I at the Córrego de Feijão Mine in Brazil in January 2019 (Fig. 1), where approximately 270 people died (VALE 2020). In 2015, the Fundão dam failed, resulting in the worst ever environmental disaster in Brazil, with the release of over 30 million m3 of tailings that polluted 670 km of watercourses on its way to the Atlantic Ocean, where it spread along hundreds of kilometres of the Brazilian coastline (IUCN 2018; Palu and Julien 2019). In 2014, the Mount Polley dam failure in Canada released 25 million m 3 of tailings and supernatant water into the environment (BCMEM 2015). There have been more than 30 tailings dam failures per decade in the period 1960–90 and around 20 per decade since 1990s. Although the number of tailings dam-related accidents has decreased since the 1990s, the number of severe failures (i.e. those that have released more than 100,000 m 3 of tailings * Gregor Petkovšek [email protected] 1
HR Wallingford, Howbery Park, Wallingford, Oxfordshire OX10 8BA, UK
and/or resulted in loss of life) has increased (Bowker and Chambers 2015). An informed risk management strategy can minimize the probability and consequences of tailings dam accidents. An accident presents a considerable economic damage to the mine owner, danger to life and health of staff
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