EM - Escola de Minas

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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.
Levantamento de parâmetros geomecânicos de uma cavidade natural subterrânea utilizando técnologias de laser scanner 3D.
(2016) Araújo, Ramon Nunes; Gomes, Romero César; Gomes, Romero César; Lima, Hernani Mota de; Braga, Marco Antônio da Silva
As cavidades naturais subterrâneas próximas a lavras de minério de ferro são hoje um dos principais desafios da mineração, uma vez que a atual legislação ambiental adota um raio de proteção de 250 metros de cavidades classificadas como máxima relevância, levando a perdas de reservas de minério e aumento dos custos de produção. Alguns estudos apontam que o raio de proteção de 250 metros necessita de revisão, motivando vários trabalhos sobre o tema. Motivado pela linha de pesquisa da ISRM - International Society for Rock Mechanics, o presente trabalho aborda o levantamento de parâmetros geomecânicos através do Laser Scanner 3D e Realidade Virtual, desde a aquisição do dado, seu processamento, bem como a forma de levantamento dos parâmetros geotécnicos em ambiente virtual 3D. O método desenvolvido se mostrou satisfatório em uma cavidade natural subterrânea localizada em Carajás – PA, nas imediações da mina de N4E, fomentando conhecimentos geotécnicos e tecnológicos para uma maior conciliação entre a mineração e o patrimônio espeleológico.

EM - Escola de Minas

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