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By Jack G. Croeni

A study was made by the Bureau of Mines to determine the influence of high energy-rate deformation on the structures and properties of low-carbon steel, stainless steel, titanium, titanium-6 percent aluminum-4 percent vanadium, beryllium, molybdenum, and tungsten. The purpose of this study was to determine relative formability, the effect of energy and temperature on metalworking parameters and resulting structures, and the properties of materials formed by this technique. Forming techniques were limited to upset forging and direct extrusion on pneumatic-mechanical forming machines. Results show that considerable grain refinement can be achieved by careful control of deformation and forming temperature by high energy-rate techniques. Significant improvements in strength were observed as a result of this refined structure. Approximate deformation resistance as a function of temperature was determined for a variety of materials.

Jan 1, 1966

By Rafael Fagundes Ferreira

Aços Bake Hardening são aços laminados a frio com envelhecimento controlado. Estes aços caracterizam-se pela boa conformação e por apresentarem aumento de resistência mecânica devido ao envelhecimento, que ocorre por tratamento térmico. Nesse trabalho, corpos de prova de tração do material BH220 foram submetidos à pré-deformações que variam de 0 a 9% por tração uniaxial, posteriormente à tratamento de envelhecimento realizado em temperaturas que variam de 140°C a 210°C em tempos de aquecimento entre 5 minutos a 45 minutos. Foi confirmada que as temperaturas de envelhecimento, na faixa estudada de 140°C a 210°, alteram a variação do limite de escoamento devido ao fenômeno de difusão que é termicamente ativado. Nos resultados encontrados verifica-se que o tempo de aquecimento, dentro do intervalo testado, não é significativo.

Aug 16, 2017

By R. Plassart, F. Laigle

"As a powerhouse, a transformer or a valve chamber, large underground caverns are a major element of hydropower plant. On the contrary to galleries and shafts which are linear and long underground structures, large caverns are designed with often complex geometries and large spans. Moreover, as these caverns are generally located on the foot of the hydraulic scheme, the high overburden is often responsible of a high stress state. Thanks to current experiences in France and around the world, the Hydro Engineering Centre (CIH) of EDF has defined great principles in the design of caverns leading to a more general methodology. The project of Tehri in India is an example of difficult ground, with in the same time a high overburden, a ductile material and an important schistosity. These physical realities are attempted to be approached in numerical modelling thanks to a constitutive law with softening behaviour and an oriented criterion integrated in the continuum model. As a result, a flexible support is advised, based on a high density bolt system and a thin lay of shotcrete. This methodology has been developed in the case of Gilboa in Israel, except the schistosity which has not been observed in situ. At last, the example of Gavet (France) illustrates a discontinuous case of numerical modelling for a good quality but fractured rock mass.PRINCIPES ET METHODES DE CONCEPTION DE GRANDES CAVERNESHYDROELECTRIQUES SOUTERRAINESRESUME Les grandes cavernes souterraines abritant les turbines, les transformateurs et certaines vannes sont des ouvrages majeurs dans les aménagements hydroélectriques. A la différence des galeries et des puits qui présentent de longs linéaires, les grandes cavernes sont des structures à la géométrie souvent complexe et avec des portées conséquentes. De plus, ces cavernes étant généralement situées en pied du circuit hydraulique, la grande couverture rocheuse peut se traduire par un état de contraintes important. Forte de ses expériences récentes en France et dans le monde, le Centre d’Ingénierie Hydraulique d’EDF a identifié de grands principes de conception des cavernes permettant l’élaboration d’une méthodologie plus générale. Le projet de Tehri en Inde est un exemple de terrain difficile, présentant à la fois une forte couverture, un matériau ductile et une schistosité marquée. Ces réalités physiques sont approchées au mieux grâce à la prise en compte dans les modélisations numériques d’une loi de comportement radoucissante avec un critère orienté intégré dans un modèle continu. Les résultats ont conduit à privilégier un soutènement souple basé sur un boulonnage systématique relativement dense associé à une fine couche de béton projeté. Cette méthodologie a ensuite été reprise pour le projet de Gilboa en Israël, exception faite de la schistosité puisque non observée sur site. L’exemple de Gavet (France) enfin permet d’illustrer un cas de modélisation numérique discontinue d’un massif rocheux de bonne qualité mais fracturé."

Jan 1, 2015

By M Foster

The new environmental legislation of 1986 was left incomplete and to date remains so. The 'missing' process by which environmental consideration should be applied was never embodied in law and has predisposition to a wide interpretation. The Resource Statutes which govern land use and development place demands on the environmental process without that definition. The Resource Statutes are themselves under review by Government. There is a new Government Department of Conservation. It is still in its early days and facing a challenge to compose its role as a steward over large tracts of land holding significant marketable resources, animal, vegetable, mineral, and abstract. It has also taken over numerous consent and advocacy roles in legislation beyond its own empowering Act. Enter the mining company, anxious if not able to get an easy passage for consents to prospect and mine, then at least to have a clear path to tread to get there, within a fixed time period. Whichever options appear available to process environmental approvals, public participation is that being favoured most by the regulatory bodies. Where a public notification of consent applications is mandatory, public participation should lead to the fastest track available.

Jan 1, 1988

By Mukesh K. Agarwala

Alloy composite parts were made from powders by Selective Laser Sintering (SLS). SLS is a rapid prototyping process that uses data from CADICAMICAE systems to guide a laser beam and rapidly form 3-D prototype parts from powders without any part specific tooling. In this study, Bronze-Nickel parts made by SLS were studied for their mechanical properties. To make the parts structurally sound, SLS parts were further processed by conventional isothermal sintering, without loss of shape. The resultant densification and mechanical properties were studied and related to microstructures and P/M densification models. These results were then correlated to the SLS processing parameters.

Jan 1, 1994

By C. Stapel, I. C. Tânczos, R. J. De Meijer

"Abstract -In recent years the Environmental Research Group of the KVI has been developing a number of radiometric techniques that may be employed in mineral sand exploration. These techniques involve: radiometric fingerprinting for assessing sand provenances and mineralogical composition; thermoluminescence for dating and provenance determination of sediments; a towed seabed detector to map seafloors for radiogenic heavy minerals and assessing heavy mineral volumes; and simplified transport mechanism models to explain and predict heavy mineral concentrations.All techniques exploit the property that heavy minerals as a group contain concentrations of naturally occurring uranium and thorium that are a hundred to a thousand times higher than in light minerals. In this paper the physics of a number of methods will be described together with a number of results. Based on these results potential applications to mineral exploration and mining are discussed."

Jan 1, 1994

By Muammer Kaya, Sait Kursunoglu

"The aim of this study was to investigate the effectiveness of ascorbic (C6H8O6) / oxalic (C2H2O4) acid as a reductant for the simultaneous recovery of zinc and manganese from a spent and mixed zinc-carbon and alkaline battery powder in sulphuric acid leaching. The effects of sulfuric acid concentration, ascorbic/oxalic acid dosages, reaction temperature and leaching time on the zinc and manganese dissolutions were investigated according to 2k full factorial experimental design; then, a simple optimization study was carried out for the best reductant. The optimum reductive acid leaching conditions were determined at 3 hours leaching time, 70°C leaching temperature, 0.5M sulfuric acid concentration, 13 g/L ascorbic acid dosage, 1/20 g/mL solid/liquid ratio and 200 rpm stirring speed. Under these conditions, the dissolution efficiencies were 99.9% for Zn and 99.3% for Mn. When our results were compared with the previous results, our findings were better than previous studies.In addition, the manganese dissolution kinetics was undertaken, and the activation energy was found to be 7.04 kJ/mol. Selective precipitations of Zn and Mn from acid solutions were carried out using NaOH and KOH. Using 3M NaOH as precipitating agent at room temperature and at pH 8; 95.4% of Zn and at pH 10; 93.7% of Mn were precipitated from the leaching solution. Under the same conditions, using 3 M KOH at pH 8; 91.6% of Zn and at pH 10, 96.4% of Mn were precipitated. Based on the experimental results obtained, an appropriate flow sheet was proposed to recover zinc and manganese."

Jan 1, 2012

By C Katonga

Mindola mine is currently the deepest mine in the Zambian copper belt. Stoping is currently active to 1330 m below surface with long range plans indicating future production from 1590 m level. The orebody is tabular and dips between 55o to vertical. The thickness varies from 8 to 14 m. The vertical crater retreat method of mining was first introduced at Mindola mine in the late-1980s following several trials that helped define the design criteria for its application. Over the last ten years the method has been continually modified to improve safety and maximise ore production. For example, due to the weakness of some rock units within the orebody formation and the instability of the hanging wall, the last VCR slices are usually between 8 - 10 m thick, and efforts are being made to strictly apply shrinkage method in order to reduce dilution. Recent advances in mining technology in the areas of equipment, blasting techniques, rock mechanics and materials handling have been employed to increase the overall productivity of the mine. Large down-the-hole machines capable of drilling 165 mm diameter blast holes, up to 80 m long are used in stoping. Each stope produces up to 20 000 tonnes of ore per month and can last for three months. Heavy systematic ground support of VCR development has significantly enhanced safety for mining crews and equipment. Crater mining has not only improved productivity and enhanced safety, but also overcome various problems associated with conventional sublevel open stoping previously employed at the mine. This paper discusses the technical and operational aspects of vertical crater retreat mining at Mindola mine during the last ten years. The changes in mining method are often accompanied by changes in mine design, blast design, mining equipment, ground support and operating practices.

Jan 1, 2000

By J. A. G. Llerena, J. Sattarvand

Tailings dam failures have been occurring in recent years. They are considered more vulnerable than hydraulic dams due to the lack of regulations on specific design criteria, and stability requirements regarding monitoring during the construction and maintenance process. Thus, monitoring the dam is essential to know the dam's existing state and ensure its safety. One of the reasons tailings storage facilities fail is slope instability caused by moisture content. A relationship does exist between moisture content and surface strength, early detection of seepage would help to assess the physical condition of the dam. Moreover, to cover the tailings dam area in an efficient way Unmanned Aerial Vehicles (UAVs) are suitable because of their versatility and high-resolution data acquisition. Mounted with a high-resolution RGB camera, and thermal, or hyperspectral sensors UAVs can acquire good quality images that combined with image analysis and machine learning algorithms yield a good estimate of soil moisture.

Feb 1, 2023

Jan 1, 1957

By A. Mainza, H. Hill, L. Bbosa

"The main objective of ore breakage characterization is to quantify the relationship between the energy supplied for breakage and the size of the resultant progeny. In this study, the ore breakage characteristics of drill core particles and crushed particles were compared. Single impact breakage tests were conducted on a basalt ore sample using the JK rotary breakage tester. The size-dependent model by Shi and Kojovic was used to fit the breakage data because the effect of initial particle size is accounted for in the model. It was found that crushed particles consistently gave a higher degree of brokenness than drill core particles and the differences were attributed to the internal structure of the particle. Drill core particles contain a lower crack density (paths of weakness) than crushed particles which have been pre-weakened during the crushing process. An increase in crack density is directly related to a decrease in the minimum threshold energy. Upon application of a stressing force above the stress threshold, particles with a higher crack density will fracture more easily because of a higher rate of crack propagation due the numerous paths of weakness available. It was therefore concluded that under the same conditions, drill core particles are more competent than crushed particles. INTRODUCTION Comminution devices have commonly been reported as being the largest energy consumers in mineral processing circuits (Napier-Munn, 2015). Cleary (1998) reported that the inefficiency of comminution devices is a result of less than 5% of the supplied energy being utilized for breakage, with the majority being expended as heat and noise. With steadily declining fossil fuel supplies and a looming global energy crisis, the mineral processing industry has increased its focus on energy reduction measures. Ore breakage characterization plays a critical role in the design and optimization of comminution circuits (Tavares and King, 1998). The main objective of ore breakage characterization is to empirically quantify the relationship between the energy supplied for breakage (specific input energy) and the size of the resultant progeny through laboratory particle breakage tests (Napier-Munn, 1996). Commonly used laboratory breakage devices include the Drop Weight Tester (DWT), Split Hopkinson Pressure Bar (SHPB) and more recently, the JK Rotary Breakage Tester (JKRBT). Typically, a standard single impact breakage test procedure consists of a matrix of experiments on particles in four to five narrow size fractions each tested at low, medium and high energy levels. The resultant progeny of each test is sized to obtain a particle size distribution (PSD) from which the degree of breakage, usually in the form of a t10 value (percentage of the progeny material that passes 1/10 of the feed size) can be obtained for each size fraction and energy level (Napier-Munn, 1996)."

Jan 1, 2018

By P M. Ashley, M T. Costelloe

The Mary Kathleen tailings storage facility (TSF) contains 7.1 Mt of uranium mill tailings. This waste repository was rehabilitated in the mid-1980s using a multibarrier dry cover. At the time of mine closure, it was predicted that acid mine drainage (AMD) generation would not eventuate and that uranium, heavy metals and radionuclides would be adsorbed within the tailings and not seep from the TSF into the environment. This study reports on the environmental status of the TSF. Gamma-ray measurements indicate an intact dry cover of the waste repository. However, seepage (~0.5 L s-1) of acid (pH 5.71), saline (0.31 per cent), high conductivity (8.8 mS cm-1), slightly oxygenated (DO 2.6 mg L-1), radioactive waters occurs from the toe of the tailings dam into the former evaporation ponds and local drainage system. Seepage waters are calcium-magnesium-sulfate rich with elevated Fe, Mn, Ni, U and Zn values. Oxygenation of tailings seepages causes the precipitation of Fe and coprecipitation and adsorption of other metals (Pb, U, Y), metalloids (As), rare earth elements (Ce, La) and radionuclides (U-235, U-238, Th-227). In contrast, Ba, Ni, Sr, Mn, P, S, Ca, Mg, Na and K as well as Ra nuclides (Ra-226 and Ra-228) remain in solution until pH neutralisation and evaporation lead to their precipitation in efflorescences and sulfate-rich evaporative sediments further downstream. Dry capping of Mary Kathleen uranium mill tailings has resulted in physical containment of the wastes. The dry cover shows no signs of erosion and radiation levels are within acceptable limits. However, the flow rate of surface seepage from the TSF occurs at a much higher rate than predicted. Also, the neutralising potential and adsorption capacity of the tailings and underlying aquifer were overestimated at the time of mine closure. AMD has developed mobilising metals, metalloids, rare earth elements, alkalis, radionuclides and sulfate from the waste repository into surface water seepages.

Jan 1, 2003

By Robert W. Freedman, Robert L. Craft, William G. Humphrey

As part of a continuing effort to reduce the weight and bulk of equipment that mining personnel must carry underground, the Bureau of Mines and the Mining Enforcement and Safety Administration (MESA) investigated accurate and convenient gas samplers for use by mine inspectors in sampling mine atmospheres. The samplers are septum-stoppered glass vials commonly used for routine blood sampling. These lightweight, compact samplers yield results comparable with those obtained with conventional bottle samplers of 250-ml nominal capacity.

Jan 1, 1975

By Fred N. Kissell

Air recirculation caused by dust scrubbers at coal mine working faces was examined by the Federal Bureau of Mines with regard to the potential hazards caused by a possible buildup of methane gas. A theoretical analysis indicated that there was no apriori way to predict the effect of scrubber recirculation on methane concentration levels. Experiments conducted in a full-scale model of a working face area indicated that methane levels were dependent to a great extent on the location of the scrubber exhaust, but that the scrubber recirculation did not substantially increase the methane concentration above those levels that would have prevailed were the scrubber not in operation. An analysis of two underground scrubber trials showed that the scrubbers had no significant effect on methane levels, and a review of explosions attributed to recirculation showed that these were characterized by a lack of fresh air as well as recirculation. It was concluded that high methane levels are due more to a lack of fresh air than to recirculation.

Jan 1, 1975

By Jr. Watts, B. K. Cantrell, D. H. Carlson, K. L. Rubow, S. T. Bagley

"Permissible exposure limits (PELs) have been established for gaseous pollutants, carbon monoxide (CO), carbon dioxide (CO), nitric oxide (NO), nitrogen dioxide (NO2), and some gas-phase hydrocarbons emitted in diesel exhaust. There is, as yet, no PEL recommended for diesel exhaust aerosol (DEA), nor is there a standard method for sampling this aerosol.The University of Minnesota and the U.S. Bureau of Mines have collaborated to develop a personal diesel exhaust aerosol sampler (PDEAS) which utilizes size-selective inertial impaction and gravimetric analysis. During the field tests of this sampler, numerous air quality measurements were made in underground coal mines that use diesel equipment.The mine mean DEA concentrations for the five mines surveyed, determined with the PDEAS in the haulageway, was 0.89 mg/m3, with a standard deviation of 0.44 mg/m3. DEA contributed 52 % of the respirable aerosol at this location.In three of the mines filter samples were collected for DEA-associated polynuclear aromatic hydrocarbons (PAHs) and biological activity determinations. Two of the mines were also monitored for the major gaseous constituents found in diesel exhaust. In general, the PAH and biological activity levels were similar for all three mines, and indicate that up to 25 % of the haulageway concentrations may be contributed by outby diesel vehicles. Measured concentrations of CO, CO2. NO, NO2, and SO2, were well below regulated levels.INTRODUCTIONDiesel exhaust contains pollutant gases, such as carbon monoxide, carbon dioxide, nitric oxide, nitrogen dioxide, and gas-phase hydrocarbons, as well as DEA. Much of the health-related concern focuses on DEA and associated organic compounds (Watts, 1992a). A wide variety of these PAHs have been identified and some are known carcinogens and/or mutagens. The U.S. Mine Safety and Health Administration (MSHA) has proposed new PELs for these and other contaminants (MSHA, 1989). MSHA has also published an advance notice of proposed rulemaking to establish a separate PEL for diesel particulate (MSHA, 1992)."

Nov 1, 1995

By Wagner da Silva Lima

Um Sistema Piloto de alimentação de biomassa foi instalado em paralelo ao sistema de alimentação de coque em uma caldeira leito fluidizado circulante movida a coque de petróleo na Unidade Fabril da Votorantim Metais em Niquelandia, GO. Quatro experimentos foram realizados utilizando os alimentadores de coque (limitados a capacidade de mistura da pá-carregadeira) e o sistema piloto instalado que tem capacidade de 30 m3/h de cavaco de eucalipto. A substituição energética chegou a 19%, bem acima dos 10% determinados pelo fabricante utilizando o sistema atual de alimentação de combustível na caldeira. O potencial de redução de custo do vapor varia de 4 a 7%.

Aug 17, 2017

By S. H. Seyedein, Hamed Tavakkoli, Mohammad Reza Aboutalebi, S. N. Asharafizadeh

The liquid–liquid extraction behavior of lutetium from different acidic solutions was investigated using two extractants, D2EHPA and PC88A, in kerosene. Lutetium extraction reactions with D2EHPA and PC88A from HNO3 and H2SO4 solutions were chemically and thermodynamically analyzed. It was found that each Lu cation was complexed with six monomers of the organic extractant and released three protons. Simultaneously, the Lu cation was instituted in the P–O–H group of the extractants. Thermodynamic analysis of reactions between extractants and acidic solutions showed that the D2EHPA-HNO3 system is the most favorable for extracting lutetium. It is noted that the calculated equilibrium constant of the reaction in this system was approximately six times larger than that of the D2EHPA-H2SO4 system. However, the value of the equilibrium constant for the D2EHPA-HNO3 system was evaluated to be approximately 200 times greater than that of the PC88A-HNO3 system. Therefore, one can conclude that the extraction behavior of lutetium is more influenced by the extractant type than the solutionmedium. The synergistic effect of different mixtures of extractants on the solvent extraction of lutetium was also examined, and the highest synergistic factor was obtained for a binary mixture of PC88A:D2EHPA at the ratio of 4:1 for both aqueous solutions.

Mar 15, 2021

By A. E. McIlhinney, I. E. Puddington, C. E. Capes, A. F. Sirianni

"Two main problems are associated with the removal of pyritic sulphur from coals. The first is due to the fine state of dissemination of pyrite, which requires grindin1 to a very fine size to accomplish liberation. The second problem is caused by the similar surface chemical characteristics of coal and pyrite, which complicates separatio11 methods based on this property. In the work described here, the problem of fine particle size was overcome by using the selective oil agglomeratioa method developed at the National Research Council of Canada. Recovery of more than 90% of the combustible values was possible, even with particles only a few microns in diameter. Experiments using conventional chemical depressants for pyrite met with little success. It was found, however, that pyrite may be rejected during coal agglomeration through treatment with the iron.oxidizing bacteria, thiobacillus-ferrooxidans. The conditions for maximum pyrite separation are described and possible mechanisms by which the bacteria act are discussed."

Jan 1, 1973

By V. K. Karra

A mathematical model for the performance of a vibrating screen is developed in terms of an oversize partition curve. This is a normalized curve for any assemblage of particles presented for screening when their size is normalized with respect to the 50 per cent passing size (d50 ) under the prevailing screening conditions. Based on the throughfall aperture (hT) of the wire mesh on the deck, the effects of oversize (% >hT), half-size under (% <0.5 hT), deck location and feed rate were evaluated using the existing screen sizing information. All these variables and also the near-mesh (1.25 hTx 0.75 hT) content (%) of the feed affect the d50. Performance data from different decks of a double-deck screen with various feed rates, size distributions and screen apertures were used to evaluate the near-mesh factor. Effects of wet screening and material bulk density are also incorporated in the model. This generalized model is useful for the simulation of a multiple-deck screen. It furnishes the sieve analysis information of all the deck output streams and therefore has a potential use in the over-all circuit evaluation when used in conjunction with relevant crushing and grinding performance models. An example illustrating the prediction capabilities of the model is given.

Jan 1, 1979

By Charles G. Kemsley

IN January, 1939, Dome Mines, Limited, purchased a few bars of an alloy drill-steel for the purpose of testing its fatigue resisting qualities as compared with those of a straight carbon-steel then in general use at the mine. A steel of the following analysis was selected: Carbon 1.00% Sulphur 0.022 Chromium 1.26 Silicon 0.17% Phosphorus 0.028 Vanadium 0.1 Manganese 0.32% Molybdenum 0.30 This steel has a tensile strength of 180,000 lb. per square inch and a Brinell hardness of 380, as compared with a tensile strength of 114,000 lb. per square inch and a Brinell hardness of 230 for the standard carbon drill steels, in the as rolled&apos; condition. The result of this test showed that about five times as many runs could be obtained from the alloy steel before failure from fatigue. It was therefore decided to replace gradually the one-inch quarter-octagon carbon steel, then in use, with seven-eighths quarter-octagon alloy steel. In January, 1940, six machines was placed on the seven-eighths steel and this was gradually increased until now (March 15th, 1941) fifty per cent of the steel being used is alloy steel. An O&apos;Donovan furnace is used at the Dome for heat-treating their carbon drill-steel. In this furnace, a magnet withdraws the steel when the critical temperature has been reached, and the operator then places the steel in the quenching tank. Not being able to use this furnace for the alloy steel, the management felt that some means should be developed to determine the quenching temperature without depending upon the operator&apos;s judgment of the correct &apos;colour&apos;. With the assistance of the Canadian General Electric Company, a radiation-type vacuum thermocouple pyrometer was adapted to this purpose, with excellent results; in fact, with this instrument no previous experience in hardening is necessary and results are remarkably uniform.

Jan 1, 1941