The elasticity is an important parameter for the evaluation of the mechanical behavior of a rock mass and a fundamental factor in the definition of the resistance characteristics, stability, and blastability in rock blasts, and it is an important parameter for the blastability equations like the Kuz–Ram method. This paper presents a comparison of the Uniaxial Compression Method (UCM) and the Impulse Excitation Technique (IET) in determining Young’s modulus. The IET is a static and nondestructive dynamic method of characterizing mechanical parameters of materials, while the UCM is a quasistatic and destructive method. We determined Young’s modulus of samples from nine basalt and diabase mines used as aggregates in the construction industry. Young’s modulus was determined by the acoustic response due to longitudinal oscillations caused by a mechanical impulse (IET) in the Sonelastic equipment and the stress-strain curve (UCM). Young’s modulus values showed high repeatability and agreed with those reported in the literature for the same material. The work shows that the solnelastic is an innovate equipment and elucidated advantages of IET in comparison to the UCM such as shorter execution time, greater safety, and a lower cost ranging from 11.5% to 22.5% of the UCM.
Electricity is one of the biggest expenses associated with underground mining and ventilation often accounts for 50% of the total electricity use. Ventilation on demand is not widely used in Brazil, but the Ipueira, Cuiaba, and Corrego do Sitio I mines reported savings of 26%, 30%, and 21%, respectively, following its application. Frequency inverters are used to control the rotation of the main fans during shift changes. The Cuiaba mine has a control room and fans are monitored online using wireless scattered sensors. Data from field studies were compared to other foreign mines. The results showed that the application of this technique, even in an experimental way, can reduce electricity consumption significantly. Despite the energy savings that can be achieved by providing air only when/where it is needed, the costs of automation, software, and infrastructure mean that it is not practical to apply this technique at a more advanced level.
In an underground mine, the ventilation is responsible for 25% to 50% of its electrical energy consumption. In countries such as South Africa, United States and Canada researchers have started to achieve a significant reduction in energy consumption without neglecting aspects of the quantity and quality of air required for the best performance of the system, in compliance with safety standards and worker comfort. In Brazil, on demand this ventilation application began in 2013 at the Ipueira mine (Bahia, controlled by Ferbasa company), and was soon after applied by the Cuiabá, Córrego do Sitio I and Lamego mines; all three mines administered by Anglo Gold Ashanti. Each mine adopted frequency inverters for the main ventilation, whereby the fan rotation is adjusted according to demand and speed drivers. This measure resulted in the saving of thousands of reais, since the flow is proportional to the velocity, the pressure is proportional to the square of the velocity, and the power is proportional to the cubed velocity. Therefore, a reduction of 20% in the flow will save about 50% of the energy required. The Cuiabá mine presents the most modern and automated system in the country. The fans are controlled and monitored through a control room. In addition, sensors scattered in the mine, control the required flow rate. The Lamego mine has a similar but simpler system. This article proposes to discuss the application and improvement of the process of ventilation on demand in Brazilian mines where this system is applied.
As the deepening of an underground mine occurs, dynamic events (rockbursts) or high deformation ground conditions can occur. The Cuiabá underground gold mine (AngloGold Ashanti, Minas Gerais, Brazil) which is around 1300 m deep, started to experience some of these issues. High deformation associated with bulking and buckling was experienced in the main decline resulting in many rehabilitation stages. Aiming to better understand and reduce the impact of this behaviour, a damage mapping of the support and reinforcement were carried out in the Serrotinho decline. Field measurements of deformation were also undertaken. It was then possible to correlate the numerical modeling outputs with the observed damage and suggest design changes. Based on the observed mechanisms, as well as the reinforcement and support damage experienced in the decline, laboratory tests were necessary to adjust the rock bolt face plate capacity and redefine the most adequate rock bolt and surface support combination to guarantee the functionality of the whole support system.
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ResumoO desenvolvimento de equipamentos elétricos permitiu a utilização de uma energia mais limpa em minas subterrâneas. A recente aplicação dessa tecnologia em carregadeiras LHD e caminhões viabilizou sua aplicação em minas no Canadá e na Suécia. Além de eliminar as emissões de poluentes, estima-se que a utilização da frota elétrica apresente um potencial de redução de aproximadamente 40% na demanda por ventilação devido a zero emissão de gases e da menor emissão de calor dos veículos elétricos. Entretanto, há poucos estudos técnicos e de aplicação na prática. Apesar dos benefícios ambientais, financeiros e de saúde ocupacional, observa-se a preferência pela tecnologia a diesel dificultando a expansão da frota elétrica em todo mundo. Nesse contexto, este artigo busca analisar para uma mina de ouro, localizada na região central de Minas Gerais, aplicação da tecnologia elétrica atualmente disponível para mineração e quantificar qual o potencial impacto sobre sistemas de ventilação com a substituição de 100% da frota diesel pela elétrica. Outra questão seria avaliar o potencial impacto que a adoção de frota elétrica representaria em uma mina nas condições brasileiras, respeitando as normas regulatórias vigentes. Palavras-chave: Ventilação de mina; Equipamentos elétricos; Diesel; Emissão de calor.
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