MPM Analysis of Karst Systems as Possible Rupture Inducers of Tailings Dams

  • Toro Rojas, Daniela (Universidade de Brasília)
  • Yerro, Alba (Virginia Tech)
  • Cordão Neto, Manoel Porfírio (Universidade de Brasília)

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Karst regions have been studied worldwide for over a century. It is estimated that karst coverage represents around 20% of the Earth's surface. In Brazil, 19 karst regions were identified throughout its territory, one of them being the main iron ore-producing region worldwide, the Iron Quadrangle. Due to its characteristics, the Iron Quadrangle is also home to many tailings dams. The risk of failure of a tailing dam may increase if there are caverns in its foundation that, over time, may collapse due to the rock dissolution process or the stresses exerted by the structure. Dams built in recent years have been constructed accounting with more accurate geological information on the region; however, this data is non-existent for older structures despite the large probability of karts. The potential consequences of tailing dam failures can be devastating for society and the environment, especially if the liquefaction potential of the stored tailings is high, which can spread over long distances. Therefore, understanding the effects of the karts’ collapse on the stability, failure mechanics, and post-failure kinematics of tailing dam facilities is crucial to ensure the safety of neighboring communities. The study of this problem is numerically very challenging because it requires the evaluation of large deformations that develop during (a) the collapse of the kart and (b) the dam failure. Conventional numerical technics (e.g., finite elements, finite differences) cannot deal with this problem because of the mesh tangling limitations, and the use of particle-based methods is mandatory. In this work, the Material Point Method (MPM) is considered to perform a stability and post-failure analysis influenced by the development and collapse of an endokarst located in the foundation of a hypothetical case. This case exemplifies a real situation in the Brazilian Iron Quadrangle in which a tailings dam sitting on a rocky mass susceptible to the formation of karst systems. The results allow for identifying the behavior of the dam before, during, and after the instability generated by the collapse of the rock. The evaluated scenarios consider situations that have not yet been widely studied but which, considering the characteristics of the region, represent a real and urgent problem for the neighboring communities.