Search Documents

By Christopher Mark

Area wide pillar failures, or “squeezes,” were once fairly common in underground coal mines. While rare today, they do occur. This paper describes seven case histories that were investigated by MSHA Technical Support. They occurred across the range of US coalfields, in both longwall and room-and-pillar mines, and involved development mining, pillar recovery, longwall panel extraction, and multiple seam interactions. Significant lessons from each are discussed.

Jun 25, 2024

By Francois Barthelat, Sam Goroshin, David Frost, Alexander Cappozi, Atefeh Nabavi

"In this study, a novel chromium–chromium sulfide cermet was produced by self-propagating high-temperature synthesis (SHS). Conventional techniques for manufacturing metal sulfides are complex, environmentally harmful, and not suitable for producing complex-shape articles. To overcome these disadvantages, a new method for the preparation of the metal-sulfur precursor charge is proposed, which can be described as reactive casting. The first cermet samples produced with the SHS process were found to be very porous, brittle, and have low mechanical strength. The possible sources for the generation of porosity were identified and analyzed and the process for manufacturing the cermet was modified. By improving the manufacturing process, the porosity inside the produced cermets was reduced from 70% to 12%.IntroductionMetal sulfide composites are in high demand in the chemical, metallurgical, and electrical industries because of their valuable characteristics such as hardness, semi-conductivity, electroluminescence, infrared transparency and catalytic properties. Current manufacturing methods for metal sulfides usually involve one of two different principal methods, including a complex multistage wet chemical process involving the precipitation of the corresponding salts from an aqueous solution with hydrogen sulfide, or hot sintering of the respective elemental reactant powders in a resistive furnace in a high-pressure inert or hydrogen-sulfide atmosphere [1, 2]. These conventional methods for synthesizing ceramic metal composites are complex, extremely time and energy consuming, environmentally harmful, and rarely able to manufacture articles with complex shapes. Therefore, in order to overcome these disadvantages, self-propagating high-temperature synthesis (SHS) was considered as an alternative method that offers significant improvements over the traditional cermet manufacturing methods [3]. SHS, which is a relatively new and attractive method for producing a wide range of advanced materials, is based on the self-sustaining feature of the highly exothermic reactions of the reactants. The SHS process results in high product purity, since the high temperatures generatedin the reaction cause any impurities to volatilize [4, 5]. SHS has low energy consumption and doesn’t require an external energy source and complex equipment, and it is self-contained [1, 5]. Since combustion synthesis has low power requirements, it is one of the few methods of materials synthesis that is feasible in outer space. Also, the process has a low cost and is capable of directly synthesizing articles with the desired shape, size and structure [5, 6]. The chemical reactions associated with SHS are typically completed in a few seconds leading to the formation of the condensed product. The high reaction rates and relatively rapid cooling in SHS reactions can avoid undesirable grain growth in products which often occurs with the conventional sintering method [3, 5, 7]. The traditional method for sample preparation in the SHS technique is to compact the reactant mixture powders in a steel die by a press to a typical density of about 80% of the theoretical maximum value, before igniting the mixture [8]. This method requires a large compression force to increase the green density and to minimize any pores in the green compact. To overcome these disadvantages, a new method for the preparation of the precursor charge in metal-sulfur by SHS is proposed which can be described as melt casting of a reactive mixture, or reactive casting in short."

Jan 1, 2012

By J. B. Neale

FRom the beginning of its activities, the members of the National Production Committee have felt that the following points were essential to the success of its work: The operators must feel that their operations were not 100 per cent. efficient; that they should be courteous and fair in their treatment of their employees; and that they should set an example of hard work and patriotic interest in increased production. Every move made must appeal to the sense of fairness of all parties concerned. The men must feel that in working more faithfully, and consequently producing more coal, they are rendering a distinct service to their Government in the time of its great need. As the workers feel that greater efficiency on their part results only in greater profits to the operators, the advantage to the operator should be lost sight of, as far as possible, and the advantage to the Government in fighting the war emphasized. Both operators and workers should know that the Government considered increased production an obligation, and opportunity for service, resting on both parties and not on the operators or the workers alone, and that both parties could very much better the efficiency of the pre-war period. Had the committee intimated that it thought the coal shortage was due entirely to the idleness and inefficiency of the workers, its campaign would have failed, for the men would have resented the charge because only too frequently their efforts to produce more coal were thwarted by bad management; besides, the operators would have lacked stimulus to better effort. On the other hand, had the impression been given that the committee thought that the coal shortage was due entirely to bad management, the operators would have resented the charge because only too frequently their efforts to produce more coal were thwarted by the idleness and inefficiency of the workers; and the workers, having been thus indirectly pronounced 100 per cent. efficient and patriotic, would have lacked stimulus to better effort.

Jan 1, 1920

By D. E. Salman, R. R. Maclachlan, R. J. Barclay

"There is a considerable resource of data for spherical charge cratering, both as single charges and in row-of-charge geometr(1). The data are. however, based on cratering performance to a single free planar surface.In practice. the more common circumstance involves an angular surf ace geometry. such as occurs at the toe of a bench or the wall of a stope. It is for the purpose of investigating this circumstance that the described test work was conducted.The test objectives were: (1) to observe the change in single-charge cratering performance between planesurface and angle geometry; (2) to identify the optimum performance of single charges cratering to a plane surface. cratering from a bench sub-grade position and cratering from a condition of zero sub-grade or stope wall geometry; and (3) to observe the performance of row-of-charges cratering to an angular surface at various row burials and spacing. The row charge burial and spacing dimensions were to be expressed in simple numerical multiples of single-charge depth-of-burial data."

Jan 1, 1981

By Jürgen. F. Brune, CLAIRE STREBINGER, ADITYA JUGANDA, Gregory E. Bogin Jr

The abstract highlights the risk of methane gas explosions in underground coal mines and the potential of computational fluid dynamics (CFD) modeling to simulate such events and assess their impact on mine ventilation. The study focuses on developing CFD models for large-scale explosions in longwall mines, specifically simulating methane gas explosions resulting from face ignition during coal cutting. The research demonstrates the integration of a combustion model into a longwall mine ventilation model and shows how the availability of explosive gas mixtures significantly affects flame propagation and explosion pressure.

Mar 27, 2022

By N. Erarslan, M. Serati

"This paper attempts to provide a simple analytical solution for the calculation of the stress tensor induced in a two-dimensional elastic ring of a brittle material subjected to general loading on either its internal or external curved surfaces. Airy stress functions and Michell’s expression in polar coordinates are used, and parametric studies are performed to investigate the influence of loading angle and the geometrical aspect ratio of the ring on the maximum induced tensile stress. INTRODUCTIONA proper and accurate estimation of the tensile strength of a given material is a crucial step in many engineering projects; in particular in rock cutting, since rocks are much weaker in tension than in compression or shear. Both direct and indirect laboratory techniques such as the direct uniaxial pulling test, the Brazilian indirect tensile test (also known as the split cylinder test), and the ring test have been proposed and developed to estimate rock tensile strength. Among these, the ring test, initially suggested by Ripperger and Davids (1946), has become particularly appealing for its ease of sample preparation and its unique breakage mechanism in almost a pure tensile mode. Unlike the Brazilian test in which high shear stresses developed in the vicinity of the contact could interfere with the tensile breakage of the disc specimen, a tensile failure starts away from the loading platens in a ring test (Hobbs, 1964)."

Jan 1, 2015

By N. K. Bohidar

Evaluation of the stability of a structure under given boundary conditions requires accurate knowledge of the state of stress as well as the mechanism of failure at the critical state of stress. This paper represents a part of the research done by N. K. Bohidar during 1965-1968 for his Ph. D. research in Mining Engineering at the University of Utah. It summarizes the determination of internal stress and failure phenomena around cylindrical openings in viscoelastic media subjected to lateral restraint and vertical uniaxial load. The conditions of lateral restraint and viscoelastic nature of the media represent conditions associated with subsurface openings in rocks. The financial assistance provided to the project from the University of Utah Research (Uniform School Fund), W. C. Browning Scholarship Fund, Earth Science Research Fund, and D. C. Jackling Loan and Scholarship Fund is gratefully acknowledged. The authors also acknowledge the assistance of S. Siugh, W. Jones, and K. McCarter during the project.

Jan 1, 1970

By Arthur La Motte

I NDUSTRIAL explosives, as distinguished from military explosives, include high explosives and blasting powder. The high explosives which are best known are straight dynamite, gelatin dynamite, ammonia dynamite and permissibles. There are two kinds of blasting powder, saltpetre blasting powder and nitrate of soda blasting powder. Blasting powders are mechanical mixtures of nitrate of potash or nitrate of soda with sulfur and charcoal, highly compressed, granulated and glazed. They ignite from a spark and burn with relative slowness, the rate of burning and hence the rate of conversion into gases depending upon the size of the granulation and upon the degree of. confinement under which the powder is placed. High explosives, on the other hand, are chemical compounds which detonate; that is, when the explosive is subjected to a violent shock, provided in practice by a blasting cap or an electric blasting cap, the molecule of the essential ingredient, usually nitroglycerin, is disrupted and the energy and heat released cause any other explosive ingredients which may be present, such as ammoniuin nitrate or T.N.T., to decompose with a resultant evolution of gases at an extremely rapid rate varying from 6000 to 20,000 ft. per second.

Jan 1, 1924

By André Luiz Vasconcellos da Costa e Silva

Aços inoxidáveis são empregados em várias indústrias. A resistência à corrosão é um fator crítico na sua seleção. A degradação da resistência à corrosão destes aços é influenciada pela precipitação de Cr23C6, que causa a sensitização e favorece outros mecanismos de corrosão. Muitos autores procuram modelar esta precipitação associando a precipitação às medidas de sensitização. Tais modelos dependem de uma premissa ligada ao nível de precipitação, ou de depleção do cromo na matriz, que resulta na sensitização em testes tecnológicos. Assim, são de difícil validação. Este trabalho apresenta resultados da cinética de precipitação de Cr23C6 através da teoria clássica de nucleação e crescimento (software PRISMA) e modelos de difusão (software DICTRA). Curvas TTT simuladas para M23C6 com PRISMA são comparadas com curvas experimentais. Mostra-se que a energia interfacial tem forte efeito na cinética de precipitação do M23C6. O crescimento foi também modelado com DICTRA e supôs que o carboneto cresce no centro de uma esfera. Em certas condições, o inverso do volume desta esfera estima a densidade de núcleos. Os resultados indicam que o valor da energia interfacial é crítico para a simulação e, portanto, para modelar a sensitização nestes aços.

Aug 7, 2018

By John Stewart

The market at present supplied by shipments from the phosphate districts of Quebec, Ontario, and New York State requires high-grade ore, carrying from 75 per cent. to 90 per cent. of phosphate of lime. In sorting out such material by hand, much valuable phosphate is necessarily left in the "culls" or refuse, besides which, much phosphate-rock of low-grade is not now mined at all, because it cannot be made available by the crude method of cobbing and hand-sorting. The utilization of such material, which would, of course, greatly benefit this industry, requires either a mechanical separation or a chemical process which would concentrate the phosphate in a form suitable for agriculture. Considering the rich phosphate now shipped as the first class, we may arrange the lower grades in three classes, as follows: Second Class.—Cull-ore from the first class, and the mass of deposits having, as gangue, pyroxene or hornblende. The following table gives the hardness and specific gravity of the minerals concerned: Hardness Spec. gravity. Apatite,....... . 5 3.1 to 3.25 Crystalline limestone (pink calcite),. 3 to 4 2.5 to 2.9 Pyroxene,..5 to 6 3.23 to 3.5 Hornblende,.5 to 6 2.9 to 3.4 Feldspar (orthoclase),. .. . 6 to 6.5 2.5 to 2.6 It is evident that when pyroxene and hornblende are present in large proportions, this ore cannot be successfully concentrated by crushing and jigging. It may be reduced to fine powder by successive treatment in a rock-breaker and a Sturtevant or Frisbee-Lucop mill, or other suitable apparatus, and in this condition it could be largely used by applying it freely upon exhausted clay soils, such as occur in Quebec and Ontario. The occupants of these once fertile river-lands are, however, hard to move in the direction of such improvements. When water-power is at hand, the cost of crushing

Jan 1, 1893

By Courtney E. Cleveland

THE gold deposits of the Pioneer and Bralorne mines, in the Bridge River district of British Columbia, are closely associated with a long, narrow intrusive body of extremely variable composition, outcropping on the northeast side of Cadwallader creek and lying almost entirely within the property boundaries of the two companies. Other masses of the same type of intrusive rock are found in the district, more or less along the line of the main axis of the Pioneer-Bralorne in trusive, and have associated with them variable amounts of gold-quartz mineralization (Figure 1). The ore deposits of the district have been the subject of investigation by officers of the Geological Survey of Canada at various times during the past 25 years, and articles on the geology and mines of the district have been published by various individuals in technical journals. A list of the more important re-ports follows: SELECTED BIBLIOGRAPHY

Jan 1, 1938

By AIME AIME

AN unusually interesting meeting devoted to the discussion of the ways and means of improving coal mining practice, through the larger use of machinery underground, was held in the Auditorium of the Engineering Societies Building on March 11. The meeting was organized by the Materials Handling Division of the A. S. M. E. and held under the auspices of the Metropolitan Section of that Society and the National Coal Association. The New York Section of the A. I. M. E., which had been invited to participate, found itself unable to do so formally because of a conflicting date for its March meeting but informally did its part to aasure the success of the meeting. As a result of the discussion at and preceding the meeting, the National Coal Association, through Walter Barnum, chairman of its research committee, has asked the A. S. M. E. and A. I. M. E. to join the Association in a study of the present problems of the bituminous coal industry. Messrs. Harry L. Gandy, Calvin W. Rice and H. Foster Bain have been selected to act as a committee which shall develop plans for a joint program.

Jan 1, 1926

By P. D. Waters

"Mineral deposits are where you find them; they have no allegiance to territorial boundaries. Over the past decade much of the new investment in mining has been outside of continental North America, let alone Canada. The larger Canadian Banks have pursued this offshore business through their multi-national organizations; this reflects both the increasingly international orientation of today's business environment, and to a degree, the competitive advantage of these offshore developments.The current oversupply situation in mineral markets and the increasing maturity of the Developed World Economy reduces the need for new mining projects relative to growth' in GNP. Those that are brought on stream in the future due to their competitive advantage, will continue to be pursued by lenders and equity investors alike. IntroductionProspects facing those who search for mineral wealth were described rather well more than 200 years ago by a Scottish professor of moral philosophy, who also happens to be the father of modern economics.In search for new mines, Adam Smith wrote in The Wealth of Nations, ""there seems to be no certain limits either to the possible success or to the possible disappointment of human industry"".How true that statement remains today, where we are seeing economic cyclical problems compounded by basic fundamental structural change within the mining industry.Despite the enormous advances in earth sciences during the past two centuries, the rewards of mineral exploration still remain uncertain. Even though a promising orebody is found, ultimate profitability may still depend on the vagaries of the marketplace, where large and unanticipated changes in supply, demand and prices can play havoc with the best of calculations.The Canadian mining industry has had its share of disappointment during the past few years, with savage competition, shrinking demand, declining prices, and disappearing profits. But it has also had some share of success, such as at Hernlo, which now seems certain to provide some of the lowest cost gold production in the world"

Jan 1, 1986

By David K. Ingram

Research performed by the U.S. insurance industry has determined that mine subsidence is uninsurable. Consequently, the insurance industry has decided not to voluntarily offer mine subsidence insurance. The U.S. Department of the Interior has long been investigating the effects of mine subsidence. These investigations have resulted in Federal regulations and controls of mine subsidence. This U.S. Bureau of Mines report generally describes mine subsidence, the development of mine subsidence insurance programs, and the eight current mine subsidence insurance programs in the United States. The States that have these subsidence programs include Colorado, Illinois, Indiana, Kentucky, Ohio, Pennsylvania, West Virginia, and Wyoming. Major aspects of the programs include history, administrative and operational procedures, insurable structures, recognition of mine subsidence, major exclusions, claims, insurance premiums, and the economic health of each program. Addresses of agencies involved with mine subsidence insurance are also given. Information within this report can be useful for residential and commercial property owners and mine operators. States that are considering starting or have an existing mine subsidence insurance program can also use this report as a model for initiating or modifying their programs.

Jan 1, 1993

By Shoobridge PH, Firkin GR

The Imperial Smelting Process blast furnace (ISF) of the Sulphide Corporation Pty Limited zinc/lead smelter at Cockle Creek, New South wales, has in recent years greatly increased its consumption of low grade feed materials, and as a consequence has experienced periods of unstable furnace operation. Routine examination of production sinter, including softening characteristics and micro- examination, showed that the problems had been caused by an increasing silica content in sinter. The silica entered a low melting point glass phase containing calcium and lead oxides. The relative volume of this phase increased until it formed a continuous matrix in the sinter structure and this made the sinter more likely to soften at lower temperatures. Premature softening caused loss of operating stability in both the shaft and hearth of the ISr. The required sinter structure for ISF smelting was found to consist of a network of intermeshing, refractory crystals which provided skeletal strength for sinter lumps even after the glass phases had begun to soften and melt. With an understanding of the importance of microstructure and softening temperature of zinc/lead sinter and the progressive identification of those factors in sinter production which affect the microstructure, a significant improvement in stability of operations has been possible.

Jan 1, 1980

By Shoobridge PH

Operating difficulties during 1977 with the Imperial Smelting Furnace operated by Sulphide Corporation Pty. Limited at their Cockle Creek zinc-lead smelter were found to be caused by premature softening of sinter in the upper shaft of the furnace. This soft- ening was shown to be a consequence of raw materials and operating policies which led to unusually high levels of both lead and silica in a sinter of low basicity. A programme of softening tests and micro-examination of a range of sinters established that premature softening occurred when lead and silica increased to the point where a lead-calcium silicate with a low lime content became the major continuous phase in the sinter. This information was used to define a range of compositions which kept the softening temperature acceptably high for furnace operations.

Jan 1, 1978

By G. W. Elger

The Bureau of Mines conducted laboratory and larger scale studies on samples of domestic perovskite and ilmenite ore concentrates to devise a procedure for recovering TiC from these ores. From the concentrates, mixtures of titanium and calcium carbides were produced. The carbides were then ground and reacted with water. This reaction decomposed the CaC2 to acetylene and hydrated lime and simultaneously liberated the TiC. Using a combination of elutriation and gravity-separation techniques to separate the hydrated lime, approximately 93 pct of the titanium was subsequently recovered as purified carbide containing 54 to 70 pct titanium with CaO content as low as 0,6 pct. This combination of techniques can be used to separate more than 90 pct of the CaO from the TiC. Therefore, this carbiding procedure is a viable method for treating titaniferous materials, including perovskite, that contain more than 20 pct CaO. Tests made in a static-bed reactor showed that for the reaction of TiC with elemental chlorine to produce titanium tetrachloride (TiCI4), a temperature of at least 940° F is desirable to achieve a suitable extraction of titanium in a laboratory chlorination reactor. In fluidized-bed tests at 840° F, 98 pct of the titanium contained in TiC was extracted.

Jan 1, 1980

The SART (sulfidisation, acidification, recycle, and thickening) process is an effective way to separate copper and cyanide from each other in the waste stream of gold processing plants using cyanidation. Factorial experimentation has been conducted to create models of copper recovery, cyanide recovery, acid addition, and oxidation I reduction potential during SART. Economic analysis of the resultant models showed that SART is best operated with a sulfide to copper molar ratio of around 0.56, a pH of 4, and a minimised cyanide to copper molar ratio. The experiments also showed that thickening time may have drastic impacts on SART performance.

Jan 1, 2011

The Gold Ridge Mine is an open-cut gold mine in the Solomon Islands. The mine is owned and operated by Gold Ridge Mining Limited, a wholly owned subsidiary of Ross Mining NL. At the invitation of the Solomon Island Government, project construction commenced in July 1997 and gold production commenced in August 1998. The mine is the countryÆs first, and represents a major milestone in the development of the Solomon Islands. At the time of project approval and construction, there was a growing awareness in the country of the potential impacts of mining in the tropics, partly due to unfavourable publicity surrounding a number of other mining operations in the Pacific region. The management of environmental impacts was therefore an important consideration in the approval of the project, and continues to receive a high level of attention from the Government and community. Ross Mining did not commit to the Gold Ridge Project until it had satisfied itself that all waste rock and tailings could be safely contained on-site, and that the standards normally expected of a mine in Australia could be met. Ross Mining approached the approval, construction, and operation of the Gold Ridge Mine with a set of operating principles that met Government and community concerns. These were:best practice environmental management; operation of the mine in accordance with standards expected of mining operations in Australia; independent peer review of key technical aspects; on-going consultation with Government and community; and equitable transfer of wealth to landowners and the local community. As a consequence, the Gold Ridge Mine has developed into a successful mining operation with a high level of support from local landowners, the general community and the Central and Provincial Governments of the Solomon Islands.

Jan 1, 1999

By John Wellington Finch

WHAT is an engineering opportunity? To the mining .engineer the natural assumption is that the first requisite 'is a mineral deposit, but, of course, it is not so simple as that. There are at various points on the earth really very great mineral deposits which, on account of geographic location, backwardness of the country, or hostility of its natives, are now, and for a long time to come will be, quite valueless. The mining engineer, and for that matter the civil engineer, is more dependent upon the decisions of capital than upon any other factor in his profession. Ordinarily it is to be assumed that money will go to any place where it is clear that an adequate return upon its investment can be secured, but for many years it has not been safe to depend upon this. ' As already stated, there are many places where local conditions are such that mining is not safe to engage in and there are still other places in which conditions have been so aggravated by the Great War and by the social unrest which has upset the Asiatic region that capital is naturally most reluctant to venture, even when engineering data makes the undertaking appear attractive. It will be evident, I. believe, that there are many factors vital to the success of a mining enterprise in some of the remote countries which we do not have to consider in the United States and which do not, in fact, exist here.

Jan 1, 1924