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By Rafael Pinto Pretti Assef

Apresentar o Balanço Energético Global da Usiminas em 2016 - Usina de Ipatinga, com os principais indicadores de consumo das áreas produtoras. Além dos indicadores energéticos globais, o balanço apresenta os consumos físicos específicos de cada insumo nas diversas áreas, permitindo a análise de cada setor da Usina, isoladamente.

Jan 26, 2018

By J L. Lett, I Brunton, T Thornhill

Block cave fragmentation has been documented in the literature to have a significant impact on mine design, performance and downstream material handling and comminution processes. Due to this impact, emphasis is placed on the premining prediction and subsequent quantification of primary and secondary fragmentation distribution. This paper discusses the fragmentation prediction and assessment methodology employed at the Ridgeway Deeps (RWD) and Cadia East PC1 (CEPC1) cave operations.Prediction of drawpoint fragmentation was based on an iterative process, which relied on an improved quantitative and qualitative understanding of the rock mass as the mining project developed. In particular, the collection of scanline mapping data provided detailed information in relation to discontinuity trace length, persistence, termination characteristics and large-scale planarity. This allowed an improved estimation of select modelling input parameters, in particular ‘block forming’ discontinuity orientation and strength characteristics.With the start of production, drawpoint fragmentation assessment was undertaken using digital image processing (DIP) techniques for drawpoint extracted tonnes up to 61 000 t. This technique provided a consistent methodology to estimate changes in fragmentation as the block cave matured. It can generally be concluded that the measured mean fragmentation distribution became finer as drawpoint tonnage increased. The incremental change in fragmentation distribution (per 10 000 t) was not uniform, with step changes evident. In addition, for a given geotechnical domain and drawpoint tonnage, the measured fragmentation distribution range was found to vary significantly. A possible explanation for these observations may relate to the disturbed flow behaviour noted from marker experiments at RWD and CEPC1. These experiments indicate that material reporting at the drawpoints (for any given tonnage extracted) may be sourced from highly variable heights within the cave, with finer material preferentially reporting.A comparison between predicted and measured drawpoint fragmentation distribution indicated two general findingsa close match between predicted and measured distributions for material greater than 1.0 m3an under prediction of finer material passing 0.5 m3 relative to measured.The findings would indicate that the fragmentation modelling frameworks utilised at both RWD and CEPC1 were deficient at predicting the percentage of finer material for both primary and secondary fragmentation.The wide range in fragmentation distributions observed in the measured results, and the discrepancy between modelled and measured fines should be considered in the design of mine (material flow, extraction level geometry and draw rate), material handling (crushing and material movement), and downstream milling (comminution and metal recovery) processes for future block cave mines at the Cadia Valley Operations (CVO). With respect to fragmentation distribution range, a sensitivity analysis should be undertaken for these design considerations, with a range in predicted fragmentation distributions investigated (for example, lower quartile, mean and upper quartile). For future mines with similar geotechnical and mining conditions, the calibration of fines should be considered in any fragmentation distribution prediction to match those measured previously.CITATION:Brunton, I, Lett, J L and Thornhill, T, 2016. Fragmentation prediction and assessment at the Ridgeway Deeps and Cadia East cave operations, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 151–160 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By João Francisco Batista Pereira

Nos últimos anos a indústria automotiva tem evoluído de forma significativa em relação à preservação ambiental (redução da emissão de CO2) e com respeito à segurança veicular. A Usiminas, alinhada com esse direcionamento, tem realizado diversos estudos visando obter novos produtos de alta resistência mecânica que possibilitem a redução do peso dos veículos e diminuição do consumo de combustível, além do aumento da segurança. O aço TRIP, desenvolvido e recentemente comercializado pela Usiminas, é um exemplo dessa nova geração de produtos avançados, que conciliam alta resistência mecânica e alta capacidade de conformação. O trabalho apresenta as características do aço TRIP desenvolvido pela Usiminas assim como os resultados de aplicação em peças automotivas da Fiat Chrysler Automobiles.

Aug 16, 2017

By Dong G. Chae

A model for the leaching of oxide ores is developed and II correlated with laboratory tests for percolation leaching of copper oxide are. Using the model, recovery of metal values and lixiviant concentration of the effluent solution at any time may be evaluated. For the copper oxide ore a simplified version of the model is examined for the leaching mechanism consisting of: 1) a surface flush reaction with the highest rate of lixiviant consumption; 2) penetration of lixiviant to react with copper minerals and gangue constituents; and, 3) slow lixiviant consumption, mostly by residual gangue materials. The simplified model is able to explain reasonably the leaching behavior of copper oxide ore by introducing a concept of effective initial size to correct for packing in a bed of fine particles.

Jan 1, 1979

By Derek Ellis

Volume II of this two-part series on Submarine Tailings Disposal (STD) as a tailings management option for coastal and island mines contains descriptions of lesser known case histories. The Misima gold mine (Papua New Guinea) and the Black Angel lead-zinc mine (Greenland) are described in some detail as the best documented cases. Atlas copper mine (The Philippines) is less fully described due to relative lack of documentation. The Misima and Atlas STD systems are working to their design criteria. At Black Angel the system adopted did not prevent contamination for a number of reasons, which are now understood. Two cases are described where STD is being developed. They are the Cayeli Bakir copper mine Turkey), and the Toquepala and Cuajone mines (Peru). There is excellent documentation available for both cases. Three case histories are described where tailings have reached the sea either through beach or river discharge. In one case the STD option has been explored (Marcopper Mine, The Philippines). In the others we explore in hindsight whether STD might have been a viable alternative using the Screening Criteria that this Volume develops - see below. The mines are Bougainville Copper Mine in Papua New Guinea, and Jordan River Mine (Canada). There is potential for STD at all three sites. Finally, the Volume presents Screening Criteria for appraising STD, based on the experience in design, operation and environmental impact reviewed in the case histories.

Jan 1, 1994

By Julián Andrés Ortiz González

Este estudo apresenta novos resultados que comprovam a confiabilidade e a repetibilidade das medições de cargas de abertura de trincas de fadiga obtidas em estudos anteriores [1,2], que foram usadas para questionar a hipótese proposta por Elber em 1970 de que a força motriz das trincas é a gama efetiva do fator de intensidade de tensões (?Kef). Para isto, dois corpos de prova DC(T), um fino com 2 mm e o outro grosso com 30 mm de espessura, foram usados em ensaios de propagação de trincas por fadiga sob ?K e Kmax quase constantes, para simular condições dominadas por tensão ou deformação plana. Medições redundantes de ?Kef foram feitas usando uma série de extensômetros colados ao longo do ligamento residual à frente da ponta da trinca, por outro extensômetro colado na face traseira do DC(T), e por um sistema independente de correlação digital de imagens (DIC), que mede o campo de deslocamentos na face do espécimem. As cargas de abertura medidas pelos três sistemas independentes foram similares, comprovando assim que suas variações significativas observadas durante o crescimento da trinca são metrologicamente confiáveis. Este resultado comprova que a propagação daquelas trincas por fadiga não foi controlada por ?Kef. As consequências desta conclusão são detalhadamente discutidas neste trabalho.

Aug 17, 2017

By Rimas Pakalnis

This paper describes a focus of work presently being conducted at the Rock Mechanics Research Group at the University of British Columbia. The underhand method under consolidated fill ensures a high recovery under an engineered back that is comprised of cemented rock fill and/or cemented paste fill. This method of mining is generally necessary either due to a weak rock mass comprising the immediate back and/or high induced back stresses. A major concern in the design of sill mats is the loading and strengths associated with the overlying sill mat. This paper reviews past practice coupled with present observations and measurements from over ten(10) mines throughout North America. It outlines areas of concern in terms of design requirements.

Apr 1, 2005

By L. R. Stace

Arguably, one of the most significant technological breakthroughs that had been experienced during the period when British Coal was the major coalmine operating company in the UK, the use of rockbolts as principal support in underground roadways brought with it the need to re-assess the technical knowledge, management controls and legislative frameworks associated with the support of mine workings. Following a major roof fall in a roadway supported principally using rockbolts in which fatalities occurred, the process of the design of rockbolted support and the systems and procedures that had been put in place to control its use in the UK were further reviewed. The paper discusses the outcome of these reviews, and how the incident initiated a major new interest in strata control research in the UK against the background of the fragmentation of the ownership of the mines following the sale of the former British Coal assets at the end of 1994, together with the proposed introduction of new strata control legislation in 1996.

Jan 1, 1996

By Ramon Silveira Assis Barros

Este trabalho foi realizado com o objetivo de se investigar o comportamento do aço inoxidável duplex UNS S32304 em meios contendo íons cloreto. Para tanto, foram realizados ensaios CST com carga e deformação constantes usando meios com concentrações distintas de cloreto de magnésio (MgCl2), em ebulição. Foram realizados também análises química, metalográfica e eletroquímica do material. Após os ensaios de CST, foi constatada a suscetibilidade à CST deste material, além da influência da concentração de íons cloreto na solução. Essa constatação foi reforçada após a análise microfractográfica dos corpos de prova ensaiados. A análise eletroquímica do material revelou a evolução de pites em potencial de, aproximadamente, 400mVECS.

Jan 16, 2018

By T. Ito, N. Tokashiki, H. A. Bilgin, Ö. Aydan, T. Akagi

This study is concerned with the electric potential induced by deformation, fracturing and sliding of non-piezoelectric geomaterials. In experiments, the acoustic emissions together with electric potential measurements were also measured in order to see how the so-called seismic electric signals are associated with new fracture occurrence and propagation and sliding in case of existing discontinuities. The outcomes of this experimental study may explain why such electric potential variations may occur during the fracturing and sliding of non-piezoelectric geomaterials. On the basis of these outcomes, their possible implications in geo-engineering and geo-science are discussed. Ce travail concerne 1e potentiel électrique produit par la déformation, 1a fracture ou le glissement du matériel géologique non-piézoélectrique. Aux expérimentations, on a mesuré 1es émissions acoustiques avec le potentiel électrique afin de constater la relation entre les phénomènes de glissement ou de formation et de propagation de nouvelles fractures le long des discontinuités existantes. Les résultats de ce travail expérimental expliquent pourquoi de telles variations de potentiel electrique se produisent durant le glissement ou la fracture du matériel non-piézoélectrique. Sur la base de ces résultats, on a discuté de leurs éventuelles implications dans les domaines de 1a géologie et de 1a géo-ingénierie. Diese Studie befasst sich mit dem elektrischen Potential das durch die Deformation, Bruchbildung und Gleiten von nicht-piezoelektrischen Geomaterialien induziert wird. In Experimenten wurden die akustischen Emissionen zusammen mit elektrischen Potentialmessungen gemessen, um zu sehen, wie die so genannten seismischen elektrischen Signale mit neuer Bruchbildung und Ausbreitung sowie Gleiten im Falle von vorhandenen Diskontinuitäten verbunden sind. Die Ergebnisse dieser experimentellen Untersuchungen könnten erklären warum elektrische Potential Schwankungen während der Bruchbildung und dem Gleiten von nicht-piezoelektrischen Geomaterialien entstehen. Auf der Basis dieser Ergebnisse, wurden ihre möglichen Implikationen in Geoingenieurwissenschaften behandelt.

Jan 1, 2003

By John Popovich

The MICON RokLok binder system including component and consolidation processes and safety and its first aide are described. The implementation procedures and selection of injection parameters are discussed. Finally a case example of recovering a 30-ft. long roof fall in mainline haulage entry is used to illustrate the economic potential of preventive measures by RokLok injection.

Jan 1, 2001

By William H. Schiffbauer, Timothy Lutz, Michael R. Yenchek

The National Institute for Occupational Safety and Health (NIOSH) Pittsburgh Research Laboratory (PRL) participated in an experiment to facilitate the remote control of dozers used on coal stockpiles. The experiment consisted of supplementing the normal sensory cues an operator requires to manipulate the dozer from a remote location. NIOSH provided and tested a vision systems intended to give the operator the ability to operate the dozer safely and efficiently from a remote position. This paper highlights the genesis of the experiment, identifies the contributions of Consol Energy and Caterpillar, and details the NIOSH efforts and successful test results. Keywords-remote-control; vision system; stockpiles; safety

By M. Z. A. Bakar

To investigate the differences in the radial drag pick cutting performance in dry and saturated sandstone, a suite of linear rock cutting test was performed using linear rock cutting machine (LRCM). Experimental results of 50 data passes, incorporating 350 data cuts were used to compute cutting, normal and side forces required for determination of other performance related parameters. Although the forces required to cut the dry and saturated rock were in congruence for most of the spacing and depths of cut combinations; but the overall averaged cutting and normal forces for saturated rock cutting were found to be 9.9% and 9.4% respectively higher than the dry rock cutting. The increase in the overall averaged forces was attributed to strength variability of one of the saturated block affecting the overall forces. The side forces experienced a negligible drop in saturated rock cutting. An increase of 28% and 9% in the actual and nominal specific energy values respectively was also recorded when cutting saturated rock as compared to the dry rock cutting. The increase in saturated rock specific energy is attributed to production of large amount of fines and few large sized chips directly contributing towards increase in specific energy. The optimum s/d ratio for dry rock tests was found to lie between 6 and 8 whereas for saturated rock cuts this value lied between 5 and 9.

Jan 1, 2012

By Charles Hudson Martins de Vasconcelos, Isaque Alan de Brito Moura, Mônica Aline Magalhães Gurgel, Tatiane Santos Ferreira, Andersan dos Santos Paula

Aços bifásicos ou Dual Phase são caracterizados por uma microestrutura ferrítico- martensítica, a qual consiste em uma matriz de ferrita equiaxial com 10 a 20% de martensita dispersa na forma de ilhas. Neste trabalho, utilizaram-se amostras de aço baixo C, micro adição de Nb e Mo, na condição laminada a frio (BFH). As simulações físicas nesse material, em escala laboratorial, foram conduzidas com o objetivo de avaliar a evolução microestrutural após redução de espessura através de laminação a frio e recozimento intercrítico com temperatura de encharque de 800 °C e permanência por 180 segundos na temperatura máxima, seguido de resfriamento sob duas proposições: em água (criticar a fração de austenita formado no encharque em função do potencial para recristalização da ferrita) e ao ar (inferir na formação de ferrita epitaxial e subsequentes transformações bainítica e/ou martensítica no decurso do resfriamento). Utilizando o auxílio da microscopia eletrônica de varredura (MEV), observaram-se que para obtenção da microestrutura característica de um aço DP seria necessário o ajuste dos parâmetros de recozimento em função do percentual de redução na laminação a frio, ou seja, aumentando o percentual de redução do material é necessária a diminuição da temperatura ou do tempo de encharque para que sejam obtidos resultados adequados as características de um aço DP.

Oct 26, 2019

By Claiborne C. Van Zandt

THE heavy postwar demand for Portland Cement has created shortages that are gradually being overcome by increases in plant capacity. In the post-war period, the Lone Star Cement Corp. has expanded several of its existing 15 plants and has built 2 new plants, now in operation, with a third new plant under construction in Brazil, of design somewhat different from that of the two preceding ones. The new domestic plants are located at Lone Star, Va., near Roanoke, and at Maryneal, Tex., near Sweetwater, and went into operation during 1951. Each plant is equipped with two rotary kilns and has an initial capacity of 1,500,000 bbl per year, or 6,000,000 sacks. The total cost of each plant was about $10,500,000, and on this basis $7.00 in 1951 money are required per bbl of annual capacity; at 376 lb per bbl, this corresponds to $37.00 per ton of output. The investment corresponds to approximately $80,000 per hourly-wage earner employed. The purpose of this paper is to describe the most interesting design features of the two new and almost identical Lone Star plants. Why the Dry Process Was Chosen The two new domestic Lone Star mills employ the dry process because: 1-The raw materials at both properties are particularly suitable and can be dried very, readily. 2-The Maryneal, Tex., plant does not have water available for slurry. 3-Very substantial kiln fuel savings can be obtained. 4-Dry raw grinding reduces ball and liner wear and- general maintenance, without any sacrifice in power. Operating costs to date have more than justified the choice of the dry process for these two plants. Raw Materials The chemical composition of Portland Cement raw material after crushing, grinding, and mixing, but before burning, is about as follows: [ ] sometimes tailings from an iron ore concentrating plant. Certain objectionable materials occur in raw mix: magnesia, limited in cement to 5 pct, in excessive amounts; alkalies, as sodium and potassium; phosphorous; and sulphur, generally present in coal and oil. The Roanoke raw, materials are dense limestone and shale. The Maryneal materials are soft limestone and a hard brittle clay that can be handled much like shale. Sand and iron ore are required in small quantities. General Plant Layout and Construction The two plants are so similar that one joint description will cover both, with such exceptions as will be especially indicated. The crushing plant is located in the quarry, and raw material is conveyed by belt to the storage building, where all materials are stored and handled. Fig. 1 identifies the various structures of the Roanoke plant. The large storage building is used for the storing and handling of all materials, including limestone, shale, sand, iron ore, coal, clinker, and gypsum. Directly adjoining the storage building is a structure under a similar arched roof, containing the raw and clinker grinding departments and the electrical substation. The discharge ends of kilns and coolers, and coal or gas burning equipment are also placed at one end of the mill building. The 340ft long kilns extend away from the main buildings to form the long leg of an L, at the end of which is the feeding and kiln dust collecting equipment, and the raw blending silos are conveniently located adjacent to the feed end of the kilns. The machine shop, storeroom, electrical shop, foremen's office, service rooms, and meeting hall are combined in one structure in the center of the plant, and the office and laboratory are close by. The cement silos and packhouse do not have to be tied directly into the manufacturing process and are therefore located at a point convenient to the railroad tracks.

Jan 1, 1952

By D. F. O?Connor

The health & safety of all workers in an underground environment is paramount to the success of our operations. The diesel emission reduction projects are key to improving such an environment. However, care must be taken to reduce the risk to personnel during such tests and prevent exposure to other hazards. VALE Inco works in a close partnership with its unionized employees, manufactures, suppliers, researchers and government officials to ensure projects are done safely and efficiently to successful completion. The Creighton Mine Diesel Particulate Filter (DPF) project is an example of such a project that is currently under way to evaluate new and innovative technology that will further our search for improved environment for our workplace. This paper will discuss the issues and processes that are followed to ensure Diesel Particulate Filter (DPF) field tests are conducted safely and productively.

Jan 1, 2009

By X Qiu

According to the temporal and spatial distribution of regional metallogenesis, thePacific Rim can be divided into four global metallogenetic systems. The Asia-Australia W-Sn metallogenetic belt is the typical representative of intracontinental metallogenetic systems. This belt resulted from Mesozoic and partly pre-Mesozoic tectonic magmatism, mainly related to S-type granite of crustal source that was generated by collisional orogeny combined with oceanic subduction in intracontinental and continental margin settings. Based on the concept of metallogenetic series, there is a group of mineralised ore types showing a definite spatial and temporal distribution from endogenetic to exogenetic. These metallogenetic series are widely distributed in the Asia-Australia W-Sn metallogenetic belt, and are well developed in Southeast China. Five metallogenetic series and two petro-minerogenesis evolution models have been established according to their tectonic settings, various types of granitoids and metallogenetic evolution.

Jan 1, 1995

By J. Priede, G. Gerbeth

"Two different instability mechanisms of electromagnetically levitated bodies are analyzed. The first is due to the virtual coupling between the electric current passing through the magnetic system and the variation of position of the body. This mechanism can result in unstable mass center oscillations of a levitated solid body. Another type of instabilities may occur because of the coupling between the motion and the electric currents induced in the body. This effect can cause a spontaneous rotation of the body setting in as the frequency of the alternating magnetic field exceeds certain critical threshold depending on the configuration of the field. This instability can be suppressed by an axial steady magnetic field of strength comparable to that of the levitating field. 1 IntroductionAn alternating magnetic field interacting with eddy currents induced in a conducting body causes repulsion between the body and the coil generating the field. Besides, the eddy currents provide a contactless heating of the body. In such a way metallic samples can be levitated and melted without a contacting crucible. This technique allows to avoid contamination of the melt with container material and so to achieve a considerable super-cooling of the melt before it solidifies. Nowadays electromagnetic levitation is widely used in material research for measuring of the thermophysical properties of molten metals (2) .It has been observed since early fifties when the first experiments on the electromagnetic levitation were done that under certain circumstances solid levitated samples start to rotate or oscillate [l]. Surface oscillations can appear in addition when the sample is melted. Such phenomena are undesirable because they often result in failure of the levitation. Recently we showed that rotational as well as oscillatory instabilities can have electrodynamic origin related to additional eddy currents induced by motion of the body in an alternating magnetic field [3] , [4].In the first part of the present paper we analyze another possible cause of oscillatory instability due to the coupling between the electric current passing trough the magnetic system with variation of the position of the levitated body. The second part of the paper deals with the origin and suppression of rotational instability in a uniform alternating magnetic field."

Jan 1, 1999

By John Cory, David Lily, Bill Hissem

The Lafarge granite quarry in Cumming, Georgia is using Principal Component Analysis (PCA) and Biplot charting to identify important variables and control air blast and vibration. Every blasting situation is unique and PCA and Biplot charting help to clarify the major variables determining air blast and vibration.

Jan 1, 2010

By David Hanson, Sean Warren, Chaparral Berry

"Coal bumps, also referred to as dynamic failure events or coal bursts (Lawson, Weakley, and Miller, 2016), continue to be a hazard in underground coal mines. While current design methods have significantly reduced the occurrence of coal bumps, they have not been completely eliminated. This paper investigates a correlation between coal compositional components, coal molecular structure, and probability of coal bumps in an effort to deepen understanding of coal behavior in an effort to reduce hazards in underground coal mines.Samples from the Penn State Office of Coal (PSOC) Department of Energy Coal Samples (DECS) were obtained for Fourier Transform Infrared Spectroscopy (FTIR) analysis using the KBr pellet method. Peaks indicative of the coal molecular structures were obtained using spectral integration software. These data, combined with published elemental data, were compared to historic bump occurrence in order to establish a possible correlation. Finally, results based on multivariate analysis of the elemental and FTIR data with bump status as the dependent variable suggest that elemental sulfur and molecular structure can be used as an indicator of bump susceptibility within the sample set considered.INTRODUCTIONThe study of coal requires consideration of multiple variables: percentages of organic and inorganic components, organic component origins, coal age, pore structure, cleat density, elemental composition, etc. Examining coal in situ increases the number of variables, such as coal depth, seam thickness, surrounding stratigraphy, and so forth. This collection of variables influences the subsequent behavior of coal simultaneously, and weighing their relative impact is a challenge for researchers. “A problem never exists in isolation; it is surrounded by other problems in space and time” (Ackoff, 1956). Having a substance such as coal that we know so much about, and yet so little, we have to ask what can be learned.An experimental study using Fourier Transform Infrared Spectroscopy (FTIR) was undertaken to determine if the chemical structure of coal contains information which may lead to a better understanding of triggers or attributes which may, in turn, lead to an increased probability of a dynamic failure event. While a full analysis of the factors driving dynamic failure are beyond the scope of this study, it is possible that a better understanding of the chemical structure of coal will lead to an increased knowledge of its inherent behavior, including its propensity to burst."

Jan 1, 2019