EM - Escola de Minas

URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/6

Notícias

A Escola de Minas de Ouro Preto foi fundada pelo cientista Claude Henri Gorceix e inaugurada em 12 de outubro de 1876.

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Filtros

2019 - 201912020 - 20211

Configurações

Autor: search.filters.author.Barbosa, Marcelo Roberto

Resultados da Pesquisa

Agora exibindo 1 - 2 de 2
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    Cave Geomechanical Index (CGI). classification and contribution to the conservation of natural caves in the iron mines.
    (2021) Brandi, Iuri Viana; Barbosa, Marcelo Roberto; Silva, Airton Barata da; Paula, Rafael Guimarães de; Correa, Tomas; Lima, Hernani Mota de; Osborne, Robert Armstrong
    Cave geotechnical studies have been the key to meeting the requirements of Brazilian environmental legislation for the conservation of speleological heritage in mining areas. This paper presents a methodology that classifies iron caves according to their susceptibility to structural instability called the Cave Geomechanical Index (CGI). This index combines four variables: (1) Rock Mass Rating (RMR), Bieniawski’ s geomechanical variable, which classifies the quality of the rock mass hosting the cave; (2) Hydraulic Radius (HR), an engineering variable that allows the dimension of the span to be evaluated; (3) Ceiling Shape (CS), a speleological variable that indicates whether the ceiling geometry of the cave spans is favorable or unfavorable for block formation, and (4) Ceiling Thickness (CT), a geotechnical variable that represents the depth between the ceiling of the cave and the surface of the ground regarding auto-support issues. The CGI was developed, applied and calibrated over four years, by monitoring 63 spans from 27 caves adjacent to active iron ore mines in Carajás, Pará state, Brazil, that had been authorized to be eliminated. This geomechanical classification system proved to be easy to implement and its results showed that 76% of the spans with breakdown occurrences in the caves were classified as high or very high susceptibility to structural instability, while 94% of the spans classified as low susceptibility did not show any signs of physical damage. The CGI is discussed with the focus on improving stability studies, predictability of cave breakdown mechanisms and geotechnical risk analysis of iron caves near mining operations.
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    Instrumented geotechnical monitoring of a natural cave in a near mine operation – towards a sustainable approach to mining and preservation of speleological heritage.
    (2019) Brandi, Iuri Viana; Barbosa, Marcelo Roberto; Paula, Rafael Guimarães de; Araújo, Ramon Nunes; Moura, Rafael Simões Vieira de; Lima, Hernani Mota de
    The iron ore mining in Brazil is currently restricted due to federal laws for natural caves protection. Four classes of cave relevance are formally designated based primarily on geological and biospeleological criteria. According to the law, Maximum Relevance caves must be protected, together with a 250 m buffer zone. This protection zone, on the other hand, blocks substantial iron ore reserves that impacts mining projects feasibility and postpones or discontinues several ones. This 250 m buffer zone has a preliminary status and can be increased or reduced according to the results of specific long-term studies that ensure caves’ physical integrity, as well as the maintenance of its ecological balance. Considering the need to preserve the natural caves and to conduct a sustainable mining operation, this paper presents the geotechnical monitoring methodology used to anticipate instabilities in the cave, as well as to optimize the study time, considering an approach through remote instrumentation. A pilot project with operations within the 250 m protected zone of a natural cave was conducted at the iron ore mine N4EN, in Carajas, Brazil. Strain and convergence measurements were conducted on the weaknesses points/zones within the caves, identified during geostructural-geotechnical mapping. The data collected were continuously transmitted via web in real time to a database server; automatically treated and turned into updated reports and control charts available on the Internet from an expert software. The results demonstrated the applicability of remote geotechnical techniques for monitoring the structural stability of caves near mining operations, even when subjected to seismic waves, generated by regular blasting. This approach has contributed to the sustainability of the operations that reached a distance of 75 m from the studied cave that remained stable and with its speleological balance and functionality.