EM - Escola de Minas

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Content analysis of dam break studies for tailings dams with high damage potential in the Quadrilátero Ferrífero, Minas Gerais : technical weaknesses and proposals for improvements.
(2020) Paiva, Camilla Adriane de; Santiago, Aníbal da Fonseca; Prado Filho, José Francisco do
Tailings dams are civil structures that have an intrinsic potential risk of failure that, if poorly managed or neglected, can lead to severe societal, environmental, and economic damage. Studies of dam breaks make it possible to anticipate these damages and plan appropriate contingency actions for critical situations. In this context, the present work presents the analysis of 86 dam break studies of mining tailings dams in the important Brazilian mineral province called the Quadrilátero Ferrífero, or Iron Quadrilateral, in the state of Minas Gerais, Brazil. The analysis involved verifying whether the studies complied with legal requirements, met international guidelines, and addressed the minimum parameters reported as critical in the literature. We found that all studies analyzed present these components: hydrological studies, the defnition of the failure mode and rupture hydrograph, and propagation of the food wave and mapping of the efects of the rupture in the valley downstream of the dam structure. However, the dam break studies showed defciencies, such as the weakness of the hydrological studies, lack of specifc criteria on the volume of tailings that are supposed to mobilize in a possible rupture, and the failures to consistently model tailings as non-Newtonian fuids. These defciencies found in the dam break studies present in Emergency Action Plan afect the predictive capacity of the rupture models and thus the accuracy of the food maps they generate, negatively infuencing preparation actions in an eventual emergency. In the absence of guidelines and the regulation about the minimal content of the dam breach studies, we suggest that a possibility for solving this defciency in the short run is to have technically trained professionals from inspection and control agencies audit the content of the dam break studies.
Rheology of mine tailings deposits for dam break analyses.
(2021) Chácara, Débora Magalhães; Oliveira Filho, Waldyr Lopes de
This article deals with the rheology of tailings deposits related to dam break analysis. The material used was a fine tailings from iron ore processing. Geotechnical and rheological characterization of these tailings were performed. The rheological characterization consisted of rotational and oscillatory tests. It was observed that the rheological properties depend on material solids content and sample preparation method. Furthermore, the material showed viscous or viscoplastic fluid behavior, depending on the solids content. The results of the rheological tests were used as input in numerical flow simulations using Flow-3D® software. Failure of a hypothetical tailings deposit was simulated, with different scenarios. Relationships between traveled distance (range, spreading), speed, and time of arrival of the flow wave versus rheological properties were determined. It was found that tailings runs are also strongly influenced by the solids content and deposit stress history (formation), resulting in different flow types ranging from mudflood, through mudflow, and even landslide. A major finding was that in the Flow-3D® analyses, the deposit volume mobilized, and the output hydrograph are parts of the solution, and not premises or a model to follow (e.g. design breach).

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