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By Alex Matheson, Nick W. D. Massey, Peter T. Bobrowsky

Crowing pressures on aggregate resources include diminishing reserves, high transportation costs, sterilization and land use conflicts. In the absence of detailed resource knowledge for a particular region, aggregate resource potential maps provide the best "first approximation" regarding the surficial distribution of sand and gravel. The 1:50 000 scale Level Ill aggregate potential map integrates several important factors which influence the management of sand and gravel. Data used to generate this type of thematic map is readily available in most areas, fieldwork required is minimal, there is a logical quantitative evaluation of the data layers and integration is easily accomplished on a desktop PC-based platform. Also the aggregate potential map, with its focus on identifying areas of potential future aggregate exploitation as well as present inventory, provides a useful tool for the aggregate explorationist.

Jan 1, 2001

By Jianglan Duan, Steve L. Cockcroft, Andre B. Phillion, Carl Reilly, Daan M. Maijer

"In the aluminum alloy wheel casting process, careful design of the cooling system in the die and its operation (cooling channel timing) are critical to achieve quality and productivity goals. The problem is challenging owing to the cyclic nature of the process and the relatively large thermal mass of the die in comparison to the wheel. For a given die geometry, a set of constraints have been defined to ensure directional solidification and an objective function, based on cooling rate during solidification, has been defined to reach a target secondary dendrite arm spacing. The methodology presented in this study employs the commercial finite element package, ABAQUSTM, and an optimization module based on the open source library, Scipy. The developed methodology has been applied to a series of geometries and cooling system configurations, including a 2-D axisymmetric wheel and die assembly generated from a prototype die. Preliminary testing has shown that careful selection of the objective and constraint functions have made it possible to reach desired solidification pattern.TM- Dassault Systèmes Corp."

Jan 1, 2014

One of the most common critical areas of longwall mining in terms of ground stability are the gateroad and bleeder entries. These critical entries provide much-needed safe access for miners and allow for adequate ventilation required for dilution of hazardous airborne contaminants and must remain open during mining of a multi-panel district. This paper focuses on the stability of the longwall entries subjected to a single abutment load such as bleeders, first tailgate, and last headgate. First tailgate and last headgate are also referred to as blind headgates and tailgates. A study of a longwall district through conditions mapping, support evaluations, and numerical modeling was conducted and evaluated by researchers from the National Institute for Occupational Safety and Health (NIOSH). The condition mapping and support evaluations were performed on entries that spanned the previous five years of mining and relied on a diverse selection of supports to maintain the functionality of the entry. Numerical modeling was also conducted to evaluate various support types with further investigation and comparison to the condition mapping. The study demonstrated the importance of the abutment load decay versus distance from the gob edge, the potential for a reduction in material handling related injuries, as well as optimal usage of secondary and standing support.

Jan 7, 2020

By D. W. Taylor, I. W. Farmer, N. Mojtabai

Rittinger's and Bond's descriptions of rock crushing relate the energy input required to fracture rock and the surface energy required to form new fractures to the change in specific surface area of feed and product during comminution. The potential applicability of this approach to blasting is illustrated, using the results of data from bench blasting tests on Pinal schists and production blasting of Carboniferous limestones. The approach contributes to understanding of the mechanisms involved in blasting and to the design of test blasts. A modified form is presented of the relationship between blasting energy, specific surface area of the muckpile and a rock energy constant related to the discontinuity structure of the rock. The modified equation fits observed data and offers a simple basis for further experiments

Jun 19, 1905

By J. Kern, M. Cain, T. Torries

Until recently, the generation of electricity was regulated in all states and the value of generation assets in a regulatory environment for ad valorem taxation were based largely on the book value of the plant plus the rate of return on capital allowed by the state regulatory agency. This method of appraising utility generation assets is inappropriate in a competitive environment because past capital expenditures are not relevant in a competitive environment. However, it is not clear what valuation methods are appropriate after restructuring. This paper identifies key problems and advantages of other appraisal methodologies and makes comments on various valuation and taxation methods.

Jan 1, 2001

By Jaime Tumialán

El presente texto describe el diseño y ejecución del sistema con winchas de fricción" Koepe" del pique central de Casapalca, dado que será uno de los más modernos del Perú y su aplicación se realizará en minas con características semejantes. Existen dos sistemas básicos de izaje: el de izaje con wincbas de tambora, donde el cable es enrrollado o desenrrollado en la tambora durante el izaje, y el de izaje con wincbas de fricción ("Koepe"), en el cual el cable pasa sobre la polea o tambora de fricción durante el izaje. Cada sistema tiene sus ventajas y desventajas y solo debe usarse en una correcta aplicación. Las principales ventajas de las winchas de fricción sobre las de tambora son: menor consumo de energía para igual capacidad, menores dimensiones de las partes mecánicas, menor costo de capital y operación, mayor seguridad debido a que se usan varios cables y una mayor capacidad a grandes profundidades.

Jan 1, 1983

IN a mine with any considerable output the economical handling and transport of ore underground is a matter of prime importance, and in the design or lay-out of a trucking system the question of what form the points and crossings are to take should be one of the first considered. Trucks may be moved from one line of rails to another by the following means: by flat sheets, with which may be coupled turn-tables, or by points and crossings. The latter class may be further divided into fixed and movable points.Flat sheets and turn-tables, owing to the time and skill needed by the trucker in using them, are seldom of great value with large tonnages, unless for purely temporary work, and the choice narrows down to one between fixed and movable points andcrossings. Both systems have their disadvantages - movable points being liable to jamb with dirt and get out of order, whilst with fixed points trucks may sometimes run over the points and capsize, or go on to the wrong line, though this is not of frequent occurrence. On the other hand. the fixed points are simple, easily laid, and strong, and there is no necessity for the trucker to work any levers, the truck being guided on to its new direction by screwing.Cast-iron points and crossings were first introduced into the North mine during the opening-up of the 950-ft. level, and the first arrangement was designed for a double turn-out in the main crosscut. Since then both the points and crossings have beenmodified several times, and it may be interesting to briefly outline the various forms through which they have passed, showing the reasons for the retention of some features and the rejection of others.

Jan 1, 1915

A large lab apparatus was designed using a scale-down methodology based on the design legacy of the current FLSmidth commercial forced air flotation machines. This new apparatus, along with a new test methodology, was used to evaluate new rapid prototype concepts. The apparatus was designed to monitor bubble size, power, pumping capacity, Jg, velocity profiles, froth character, and tip speed. The methodology developed follows a sequence that goes from hydrodynamic tests and solids suspension tests to a flotation kinetic test. This methodology has been demonstrated to be a good tool to determine the effect of machine design changes on flotation.

Jan 1, 2012

By André Luíz Moreira de Souza

O objetivo do trabalho é demonstrar a otimização de recursos com a implantação de grades de agendamento e gestão logística via SAP do processo de abastecimento da Vallourec Tubos do Brasil, com carvão vegetal produzindo em fazendas da Vallourec unidade Florestal, distribuídas em quatro regionais no estado de Minas Gerais. O novo formato da operação permitiu a redução da frota utilizada e o aumento da taxa de ocupação dos equipamentos. Atualmente movimenta-se aproximadamente 400.000 ton./ano de carvão vegetal. A frota é composta por equipamentos novos, rastreados, transportadores dedicados, os quais são considerados parceiros no desenvolvimento da operação. Avalia-se o desempenho de cada equipe envolvida em frequentes reuniões, nas quais são definidas ações de melhoria sempre que necessárias. Temos um atendimento maior que 98 % a grade programada para recebimento do carvão vegetal, considerando os tempos de carga e descarga.

Jul 29, 2018

By Vinícius Cardoso da Rocha

Frente ao cenário industrial competitivo, o emprego de fluxantes em lingotamento contínuo de aços permitiu o aumento da produtividade e a redução das perdas metálicas por defeitos superficiais. Neste estudo, avaliou-se a aplicabilidade de dois tipos de fluxantes para produção do aço SAE 1046 Mod. Os fluxantes foram testados quanto ao desgaste da válvula submersa, frenagem (atrito) na interface metal/molde e rejeição dos produtos de lingotamento devido à presença de defeitos superficiais. O fluxante teste apresentou taxa de desgaste de válvula submersa de 2,2 mm/corrida, frente ao fluxante padrão com 0,8 mm/corrida. Entretanto, o fluxante teste demonstrou bons resultados quanto à lubrificação do molde, reduzindo a frenagem (atrito) entre o metal e molde e, consequentemente, melhorando a qualidade superficial do produto de lingotamento. A rejeição dos produtos por defeitos superficiais reduziu 47% com o fluxante teste.

Aug 16, 2017

By Breno Carvalho de Oliveira

Neste trabalho é apresentado uma ferramenta de otimização multiobjetivo para planejamento da manutenção de ativos ferroviários. A aplicação foi modelada com base no problema do Caixeiro Viajante Multiobjetivo, considerando como objetivos a minimização da postergação da manutenção dos equipamentos e do deslocamento da equipe de manutenção. Foi utilizada uma instância real de 17 cidades que são atendidas por uma única equipe de manutenção. A ferramenta de otimização consiste na combinação do algoritmo SPEA2 (Strength Pareto Evolutionary Algorithm), da methaheurística GRASP (Greedy Randomized Adaptive e Search Procedure) e de uma heurística de busca local em vizinhança, cada uma com seu papel específico dentro da otimização. O algoritmo foi capaz de mapear soluções melhores que a atualmente adotada pela empresa, proporcionando uma economia significativa no valor total a ser gasto em um ciclo de manutenção dos ativos ferroviários.

Oct 30, 2017

By Quésia de Freitas Silva Fonseca Rodriguesr

Os diamantes obtidos no sistema Ni-Mn-C com adição de teores de ferro de 0% a 5% foram submetidos ao teste de friabilidade para avaliação da resistência mecânica ao impacto. A resistência dos cristais pode ser influenciada por vários fatores como o dispositivo de alta pressão, sistema catalisador/solvente, tempo de síntese, tipo de grafite. No presente estudo os diamantes foram obtidos sob pressão de 4,5GPa e temperatura 1250ºC de, com período de processo de 10 minutos, utilizando o dispositivoi do tipo bigorna concavidade central. Os teste de friabilidade foram realizados no friatester, onde é determinado o índice de quebra em função do teor de ferro adicionado foi avaliada o índice de quebra e os fragmentos ou cristais que resistiram ou não ao impacto. Foi constatada uma significativa influência do teor de ferro sobre a friabilidade dos cristais

Aug 16, 2017

By R. G. Gürtunca, J. A. Breslin

This paper briefly describes the progress in mine safety in the United States, with emphasis on recent events that have followed since the explosion at the Sago Mine in January 2006. Legislation following the mine accidents last year and areas of work carried out by the National Institute for Occupational Safety and Health (NIOSH) related to the accidents are discussed. American coal production in 2006 was 1,150 million short tons. Most of this coal is consumed domestically, with annual exports of coal about 50 million tons. One third of annual production is produced at surface mines and the rest from underground. This coal is produced by about 82,000 miners working at 1,400 coal mines. Major improvements in coal mine safety have been made in the US since the Federal Mine Safety and Health Act of 1977. The fatal injury rate in underground coal mines between 1977 and 2004 was reduced by 47.8% to 0.036. The annual number of fatalities dropped from 112 to 14 during that period. Likewise, the non-fatal days-lost injury rate was reduced by 42.6% from 10.87 to 6.24. The improvements in mine safety during this period can be seen in the graph of underground coal mine explosion fatalities and injuries from 1980 to present, which is shown in Figure 1. Between 1984 and 1993 (9 year period) there were 5 explosions and one major mine fire, for a total of 55 fatalities. Over the seven year period from 1993 to 1999 there were no fatalities from coal mine fires and explosions. However, in the six years since 2000 there have been 5 explosions and one fire, which have caused 37 fatalities. [ ]

By S. G. Ozkan

An investigation was carried out into the effect of physical parameters, such as particle size of the sample, residence time, solid/liquid ratio and impeller speed in the flotation cell, on the solubility in soft tap-water of colemanite (calcium-bearing borate) from Emet, in Turkey. Solubility increased steadily with residence time from 5 to 20 min but only minimally thereafter. There was a similar increase with impeller speed from 500 to 1 500 rev/min, beyond which a solubility of around 1.05 g/l was again established. There was a slight decline in solubility as the solid/liquid ratio was increased from 1 to 30%, with stable values around 1.05 g/l at a 20% ratio, while a sharp decrease was observed with decrease in size down to the -20 micrometre fraction. The effect of solubility should be taken into account if the application of a wet-processing method is being considered for the ore, while it can also result in losses of material during handling and storage

Jun 21, 1905

To improve the air quality in large-opening stone mines by developing better ventilation techniques, including appropriate fan selection in conjunction with air-coursing methods. Background Stone mines are the most common underground large-entry mines in the United States. Data from the Mine Safety and Health Administration (MSHA) for the year 2000 indicate that there were 162 active nonmetal underground mines in the United States, of which 117 were stone mines. Many underground stone mines are drift mines developed from previous quarry operations. Typically, these room-and-pillar mines have entries that are 20 ft or higher and at least 40 ft wide. These large dimensions lead to a very small ventilating pressure loss, even when significant air quantities move through the mine. This is especially true of drift mine operations where ventilating pressure losses of <0.25 in w.g. are common. Underground stone mines with shafts that are<200 ft deep typically have ventilating pressure losses that are <2 in w.g. The pressure losses through these mines are much lower than those of a typical coal mine or deep metal/nonmetal mine. Therefore, the ventilation techniques and principles are quite different. In addition, because of new MSHA regulations that limit the concentration of diesel particulate matter, these mines may need to greatly increase their ventilation airflow. Therefore, large-opening mines need a fan that can move large air quantities and operate at low static pressures. There are three fan types for mine ventilation: centrifugal, axial vane, and propeller. Centrifugal fans are uncommon in underground stone mines as they are often associated with mines requiring the highest of ventilation pressures. Axial vane fans are widely used in all types of mining operations. They are the most common fan type currently found in underground large-opening stone mines. However, they typically do not operate at low static pressures with high efficiency. Propeller fans are currently uncommon in underground stone mines. They are designed for low static pressures and large air quantities at higher efficiency. This fan type best suits the ventilation needs in large-opening stone mines?they produce large air quantities at low pressure losses. Mines with air shafts<100 ft long and at least 12 ft in diameter have fairly low mine static pressures and may also benefit from propeller fans.

Dec 1, 2002

By J Folwell, G Phillips, F Gassner

Geomembranes selected for various applications often start with considering target properties developed by industry organisations such as Geosynthetic Research Institute (GRI), and test methods developed by ASTM and other Standards organisations The geomembrane types are typically, initially selected based on manufacturers recommendations and chemical resistance data from the manufacturer or industry knowledge. Geomembranes considered for this project included materials with material properties that exceeded the minimum target values of various test methods. The difficulty is in selecting which parameters are most important for a particular application and also what service life can be expected for the geomembrane under various chemical and environmental exposure conditions. Accelerated aging testing of candidate geomembranes in simulated exposure conditions can be useful to select the preferred geomembrane and predict the service life of the geomembrane under different exposure conditions. The exposure conditions of immersion in acidic tailings liquor, splash zone and freeboard zone were considered for evaporation ponds on a site with significant heat and UV radiation. Candidate geomembranes considered a range of different types of polyethylene liners. The results of the accelerated aging testing have allowed the selection of the geomembrane for the range of exposure conditions and evaluation of the expected service life of the geomembrane.

Jul 1, 2021

By F. S. Wartman

The presence of magnetite, either dissolved or suspended as solid crystals, in slags from the copper reverberatory furnace is a frequently mentioned cause of an abnormally high copper content in those slags. The presence of this oxide in the slag is to be expected, since it is present in appreciable amounts in both converter slag and roaster calcine which comprise a considerable proportion of the furnace feed. Magnetite is also a product of some of the furnace reactions. These abnormal losses result in several ways. Magnetite is supposed to favor the formation and retention of copper ferrite, in the slag. Crystals of solid magnetite suspended in the slag are objectionable-because they make the slag less fluid and often entrap globules of matte. Frequently these crystals settle into a layer at the slab-matte interface which may have such mechanical strength as to create a false bottom and interfere with furnace operation by preventing separation of matte from slag. Magnetite may, by crystallizing on the furnace bottom, build the bottom to such a level that the furnace can no longer be operated.

Jan 1, 1928

By Hans-Åke Häggblad, Bertil I. Pålsson, Jan Stener, Kent Tano, Andreas Berggren, Pär Jonsén

Numerical modelling of grinding in tumbling mills is traditionally done with the discrete element method (DEM). The grinding balls are then represented by DEM particles and the mill structure is considered rigid. To include more physical phenomena several numerical methods can be combined. One important improvement is to include the mill structure response, using the finite element method (FEM). The interaction between charge and lining can then be studied in detail. The pulp can also be included using a particle-based continuum method e.g. smoothed particle method (SPH). The strength of SPH lies in modelling of free surface flows and very large deformations and it is suited to model simultaneous fluid and granular flow. Still, the coarse particles (grinding balls) in the charge are suitable to be model using DEM. Each of these methods has their strength and weaknesses, but combined they can successfully mimic the main features of the charge movement. With these numerical tools the complex interaction between the different components of the grinding process; pulp, charge, lining and the mechanical behaviour of the mill, can be studied together. This work will present novel numerical approaches to model, simulate and validate charge behaviour in tumbling mills. These numerical models give possibilities to better understand the physical and mechanical behaviour of particulate material systems during grinding in a tumbling mill. This is important in order to develop and optimise future high-capacity grinding circuits and save energy.

Jan 1, 2014

By Forrest T. Moyer

To keep the mineral and allied industries informed of trends in the causes of accidents and to point out the need for corrective measures, the Bureau of Mines collects, analyzes, and periodically published health and safety statistics. This report includes data for 1964 on injury experience, with related employment statistics, at coal mines in the United States. These data are presented in tabular form under the following headings: General Injury Experience Tables 1 to 6: Current data on number of injuries, degree of injury, frequency and severity rates, average severity, and related employment and production data by work location.

Jan 1, 1967

By Charles H. Foreman

IN JUNE 1921, the Sullivan &lining Co., owned jointly by the Bunker Hill and Sullivan Mining & Concentrating Co. and the Hecla Mining Co, started work on the development of the Star Mine. The development work contemplated called for a crosscut from the Hecla workings on the 2000 level to the Star ledge. The length of crosscut necessary to encounter the Star ledge was approximately 8900 ft. from the Hecla shaft. By using workings formerly made by the Hecla Mining Co., only about 8100 ft. of actual crosscutting was necessary. This crosscut has a direction of S 20° W and would have a tendency to crosscut any ledges in the intervening ground.

Jan 1, 1924