Diagnóstico geofísico para identificação de zonas de fluxo em uma barragem de contenção de rejeitos de mineração de urânio
Arquivos
Data
2020-03-20
Autores
Arcila, Erika Juliana Aldana
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ISSN da Revista
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Editor
Universidade Estadual Paulista (Unesp)
Resumo
Uma barragem de rejeitos é constituída por uma barreira física, cuja função é a acumulação de produtos residuais do processo industrial de beneficiamento mineiro. Os métodos de projeto para barragens de rejeitos diferem das barragens de retenção de água pela construção do barramento em diferentes etapas. Deste modo, os problemas de estabilidade em uma barragem são de grande importância, principalmente quando se trata de barragens construídas para armazenamento destes rejeitos de mineração, uma vez que a possibilidade de falhas não apenas ameaça a segurança das pessoas e da propriedade industrial, mas também pode causar impactos ambientais substanciais. No Estado de Minas Gerais, aproximadamente 30 km a sudoeste do município de Caldas, está localizada a Mina Osamu Utsumi de responsabilidade das Indústrias Nucleares do Brasil (INB), a qual tem um sistema para contenção de rejeitos provenientes da exploração e processamento de urânio, atualmente desativado. O Sistema consiste em uma barragem de rocha e terra a qual apresenta a existência de surgências no maciço rochoso à jusante do barramento, cujo fluxo ocorre em sistema fraturado. O objetivo do trabalho é reconhecer possíveis zonas de fluxo no interior e na base da barragem por meio de um conjunto de ensaios geofísicos de eletrorresistividade adquiridos com a técnica de tomografia elétrica através de modelos de inversão 2D e modelamento 3D. Foram adquiridas 5 linhas de tomografia elétrica com espaçamento entre eletrodos de 6 m e o arranjo utilizado no estudo foi o Schlumberger. Os resultados são apresentados a partir de imagens geofísicas 2D e 3D com valores de resistividade elétrica medida e modelada, onde foi possível identificar uma zona de baixa resistividade cuja continuidade estrutural indica infiltração da água no maciço rochoso abaixo da barragem. Os resultados não mostraram evidências de piping no interior do barramento o qual diminui o risco na estabilidade geotécnica e integridade física da barragem.
A tailings dam is constituted by a barrier, whose function is the accumulation of residual products from the mining beneficiation industrial process. Project methods for tailings dams differ from water retention dams by the construction of the dam in different stages. Thus, the stability problems in a dam are of great importance, especially when it comes to dams built for the storage of these mining waste, since the possibility of failures not only threatens the safety of people and industrial property, but also cause negative and substantial effects to the local environment. The Osamu Utsumi uranium mine, administrated by the state company Industrias Nucleares do Brasil (INB), is located 30 km southwest of Caldas, in the State of Minas Gerais, and its contention system of tailings, generated by the exploration and processing of uranium ore, is currently out of operation. The system is composed of a rock-soil dam, which presents the existence of water upwellings downstream in the bedrock, with water flux confined in fractures. This research aims the recognition of possible flux zones into the base of the dam through geophysical surveys applying DC Resistivity, in addition to Electrical Resistivity Tomography technique in the generation of 2D inversion models and 3D modeling. The acquisition was composed of five lines of electrical resistivity tomography with 6 m of spacing between electrodes, using Schlumberger array. The results are presented by 2D and 3D geophysical models comprising measured and processed resistivity values. According to those models, it was possible to identify a low resistivity zone, whose structural continuity indicates water infiltration in the bedrock, right under the dam. Moreover, the results do not indicate pieces of evidence of piping process in the interior of the dam, reducing the risks related to the geotechnical stability and physical integrity of the construction.
A tailings dam is constituted by a barrier, whose function is the accumulation of residual products from the mining beneficiation industrial process. Project methods for tailings dams differ from water retention dams by the construction of the dam in different stages. Thus, the stability problems in a dam are of great importance, especially when it comes to dams built for the storage of these mining waste, since the possibility of failures not only threatens the safety of people and industrial property, but also cause negative and substantial effects to the local environment. The Osamu Utsumi uranium mine, administrated by the state company Industrias Nucleares do Brasil (INB), is located 30 km southwest of Caldas, in the State of Minas Gerais, and its contention system of tailings, generated by the exploration and processing of uranium ore, is currently out of operation. The system is composed of a rock-soil dam, which presents the existence of water upwellings downstream in the bedrock, with water flux confined in fractures. This research aims the recognition of possible flux zones into the base of the dam through geophysical surveys applying DC Resistivity, in addition to Electrical Resistivity Tomography technique in the generation of 2D inversion models and 3D modeling. The acquisition was composed of five lines of electrical resistivity tomography with 6 m of spacing between electrodes, using Schlumberger array. The results are presented by 2D and 3D geophysical models comprising measured and processed resistivity values. According to those models, it was possible to identify a low resistivity zone, whose structural continuity indicates water infiltration in the bedrock, right under the dam. Moreover, the results do not indicate pieces of evidence of piping process in the interior of the dam, reducing the risks related to the geotechnical stability and physical integrity of the construction.
Descrição
Palavras-chave
Geofisica, Rejeitos, Barragem, Resistividade elétrica, Geophysics, Tailings, Dam, DC resistivity, 3D modeling