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By Amanda Thicyane de Miranda Duarte de Souza

A crescente demanda de energia elétrica em nosso país sobrecarrega o Sistema de Transmissão [Tx] e Distribuição [Dx], e gera a necessidade de constantes ampliações para não prejudicar o desenvolvimento do Brasil. Neste contexto foram realizados estudos visando avaliar o efeito da adição de três teores de Ni em uma liga Al-0,05%Cu-[0,24-0,28]%Fe-0,7%Si destinada à produção de cabos elétricos. O estudo parte da verificação e posterior comparação das características estruturais, mecânicas e elétricas da liga com a adição do elemento citado. Para a realização do mesmo, os perfis estudados foram obtidos por solidificação estática direta em lingoteira metálica e as amostras foram obtidas a partir de perfis solidificados, usinados e deformados a frio para diferentes diâmetros. Nestas circunstâncias, o diâmetro de 3,0 mm foi aquele que apresentou as melhores respostas elétricas, mecânicas e estruturais, sendo, portanto, adotado como fonte de estudo.

Aug 7, 2018

Using Positron Emission Particle Tracking (PEPT) to Investigate Industrial Systems

Sep 13, 2010

By George C. Heikes

ALTHOUGH the application of light metals in war materiel increased during the year, based on the number of uses, the trend in aluminum and magnesium production in 1944 was characterized by a sharp decline in the production of both metals accompanied by a further accumulation of large Government reserve stocks. Several primary reduction plants were curtailed to prevent building excessive inventories. By the end of the year, however, a lively revival of war production took place when resistance stiffened on the western front in Europe. Production of primary aluminum ingot was reduced from over 90,000 tons per month at the start of the year to 45.000 tons per month by the end of the year.

Jan 1, 1945

By Tell Ertl, Ernest E. Burgh, John R. Wagner

The principal goal of the Oil-Shale Mining Division is to develop the most economical methods and practices for mining oil shale. Experimental work in the mine has not progressed far enough to conduct full-scale breaking tests; therefore, mining season - to October 31, 1945, has been confined largely to problems connected with drilling cost oil shale. Calculations have indicated that commercial production will result in breaking the oil shale; the largest individual turn will be for drilling. This paper is a report on the progress of phase two of drilling research to date; it outlines the development of a successful hard-surfaced rock bit for drilling oil shale.

Dec 1, 1948

By Selwyn G. Blaylock

I.-THE HISTORY OF THE SYSTEM TO trace the history of the development of the Co-operative Committee System in The Consolidated Mining and Smelting Company of Canada, Limited, one must look backward about twenty years. In 1915 and 1916, the first years of the W ar to really affect Canadian life, there were sixteen hundred men working in the Trail plant. These men were, on the whole, a splendid body of men and pa trio tic to the core. They were almost one hundred percent organized, ninety-five percent of them be-longing to the Union of the Western Federation of Miners. Most of the tradesmen belonged to their craft unions as well. For example, there were ? local machinist, steel workers', electrician, boiler maker, bricklayer, and carpenter unions. The Company had always maintained an open-shop policy and refused to enforce membership in any union, but recognized the right of every man to belong to unions. The only exceptions have been the I.W.W. and the One Big Union. Both of these organizations have always been fought by the Company. By 1916, membership in the Western Federation being practically 100 per cent, the Company recognized this organization's authority to make agreements, and a wage and hour agreement was drawn up and signed by the Company and the local officials of the Union, and ratified and signed by the Head Office of the Union in Denver, Colorado. This agreement was for the duration of the war.

Jan 1, 1936

Review of the mining legislation in New Zealand has coincided with a number of radical changes. These include a redirection of economic management towards a more open and competitive economy; major reform of the state sector aimed at greater efficiency, transparency and accountability; a new environmental administration; and a fundamental review of policy for management of natural and physical resources. These changes provide an opportunity to develop a consistent and coherent approach in the minerals and related statutes that will achieve objectives of economic efficiency, equity, practicability and good environmental management.

Jan 1, 1987

By Faruk Oksuz, Cary Hirner, William A. Rochford

Grouting is a frequently utilized remedy in the planning and implementation of ground improvement and tunnel rehabilitation practice. The state-of-art grouting application used for Chicago’s McCook Reservoir project offers a unique alternative to the tunneling industry for pre-excavation grouting as well as tunnel rehabilitation, rescue and post-excavation ground improvements. The McCook Reservoir project included a computerized grouting control and data collection system for a precise and highly effective groundwater cutoff in fractured dolomites. By using balanced and stabilized grout mixes, the effective permeability of the rock mass was reduced over two orders of magnitude to less than 0.1 Lugeon by installing a double line grout curtain. The stable grout mix designs allowed high pressure and effective grouting at depths up to 125 m (410 ft).

Jan 1, 2005

By Letícia dos Reis Gonçales

A liga AZ91D apresenta 9%pAl e 1%pZn e pode ser submetida a tratamento térmico de solubilização seguido de envelhecimento para melhoria de propriedades mecânicas por meio de precipitação da fase beta-Mg17Al12. Esta fase, porém, pode ter efeitos distintos sobre o comportamento de corrosão da liga. Buscando estudar a influência do tamanho de grão da matriz alfa e a presença de precipitados beta sobre a resistência à corrosão da liga AZ91D, este trabalho utilizou lingotes com estrutura bruta de fusão na obtenção de amostras solubilizadas, laminadas a frio e então envelhecidas, para subsequente análise microestrutural e do comportamento de corrosão. A solubilização ocorreu a 445ºC por 24h e foi efetiva em dissolver quase completamente a fase beta. A laminação levou a uma redução de 20% da espessura das amostras e de 400 para 130 µm o tamanho de grão médio, após envelhecimento. O envelhecimento feito a 200ºC em 2 e 24h permitiu a precipitação de fase beta em maior quantidade e melhor distribuição por contornos de grão em relação às amostras fundidas ou solubilizadas. Ensaios de imersão foram realizados, apontando uma leve queda na taxa média de corrosão quando se lamina a amostra, enquanto as amostras solubilizadas (sem fase beta) mostraram maior susceptibilidade à corrosão. Assim, é possível indicar que o refinamento de grãos é benéfico ao formar uma rede de proteção em ligas de magnésio AZ91D, apesar de introduzir defeitos gerados pela laminação.

Aug 17, 2017

By X. H. Zhang, J. G. Cai

This paper discusses the behaviour of large-span tunnels and caverns in hard rock in a major underground storage project. In-situ stresses were measured using hydraulic fracturing during site investigation and 3-D overcoring during construction, with both showing a horizontal stress ratio of 2-3 times the vertical stress. Rock reinforcement design was based on the Q-system combined with numerical modelling for special design cases. Tunnel design and performance were checked and monitored by in-situ instrumentation during rock excavation, including measurements of deformation, convergence, and load on rock bolts. Deformation measurements using borehole extensometers included one borehole drilled into the virgin rock before rock excavation, which provided a direct and very insightful comparison with the various deformation measurements made during rock excavation. These measurements coupled with numerical calculations have proven that the high horizontal stresses to be very favourable to the stability of the large openings.

Jan 1, 2003

By T Trott, M Lewis, G Lumley

The analysis of equipment trends in The AusIMMÆs revision of Monograph 19 - Australasian Mining and Metallurgical Operating Practices (AMMOP) (in prep) in the paper by Graham Lumley raised some interesting, and in parts disturbing, trends in the Australian open cut mining industry. According to the Australian Bureau of Statistics (2011) the productivity of the whole mining industry is down by 34 per cent since 2001. In terms of open cut equipment, median output for draglines is down by 15 per cent since 2003, electric rope shovels are down by 41 per cent since 2003, hydraulic excavators are down by 39 per cent since 2008, front-end loaders are down by 39 per cent since 2007 and trucks are down by 41 per cent since 2006. Clearly e boom has not been good for the efficiency of the mines. During this same time, best practice (defined as the average of the top ten per cent by annual output per unit of input) has declined, but not by as much as the median (eg shovels down by eight per cent, excavators down by 19 per cent and FELs down by five per cent). This paper will build on the analysis of AMMOP to understand the differences occurring between median and best practice and identify the factors contributing to the decline in performance. As the industry enters a period of potentially lower prices for commodities and reduced margins, pressure will be brought to bear on mine sites to start moving more with the equipment they have. An understanding of where efficiency has been lost will be a key component in that. The information contained in AMMOP, and the subsequent analysis of that information in papers such as this one, will be crucial to reversing the decline in open cut equipment performance.CITATION:Lumley, G, Trott, T and Lewis, M, 2012. Reversing the trend in open pit mining equipment output, in Proceedings Eighth Open Pit OperatorsÆ Conference , pp 75-82 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 18, 2012

By Desiree Willis

Disc cutters have determined excavation rates of rock tunneling projects for more than 50 years. First developed in 1956 by James S. Robbins, disc cutters (then 279 mm or 11 in. in diameter) were used to bore limestone of 190 MPa (27,500 psi) unconfined compressive strength (UCS) and were loaded with 7.12 t (15,700 lbs) each. Modern cutters have reached up to 508 mm (20 in.) in diameter and are typically loaded with up to 31.7 t (70,000 lb) to economically bore through the hardest of rock up to plus 400 MPa (60,000 psi) UCS. New developments, such as larger cutter diameters, are geared to increasing the bearing capacity and wear life of the cutting structure. This, in turn, increases cutter life, cutter load and cutter penetration. Disc cutters have also been re-designed on a small scale for use in hard-rock utility installations. Additional variables also affect the three factors, including cutter spacing on the cutterhead, cutterhead diameter and cutter materials.

Jan 1, 2007

By H. F. MILLE, Charles A. Kumke

This paper describes mining operations at the Iron King mine of the Shattuck -Denn Mining Corp. in Yavapai County , Ariz . It is one of a series being prepared by the Mining Division of the Bureau of Mines on mining practices and methods in various mining districts of the United States . The mine and surface plant of the Iron King mine are situated in secs . 15 and 21 , T. 13 N. , R. 1 E. , about 20 miles by State highway 69 east by southeast from the city of Prescott and 1 mile southwest of the mining town of Humboldt on the Prescott -Mayer branch of the Atchison , Topeka & Santa Fe Railroad (fig . 1 ) . A l-mile truck haul brings the mill concentrates (lead and zinc ) to bins on a siding of this line at Humboldt ; the silver -gold bullion is handled separately . Some of the oldest residents in the vicinity of Prescott claim that the original location for the Iron King mine was made in 1880. The earliest recorded production was in 1906-1907 . During the first World War the mine produced fluxing ore for the Humboldt smelter . In 1936 the property was purchased under tax sale , and a mill (140-ton capacity ) was erected in 1938. The capacity of this mill was increased to 225 tons the following year , and a cyanide plant was added in 1940 to treat mill tailings . In 1942 the Shattuck -Denn Mining Corp. purchased the property . A new working shaft was sunk , mine development was speeded , and mill capacity was again increased . The predominating locally formation of this district is a pre -Cambrian schist known as Yavapai schist . The Iron King deposit , which carries gold, silver , lead , zinc , and copper , occurs as a series of lenses in a sheared zone of the pre -Cambrian schist . Down to the 600 -foot level the ore was mined and drawn by the shrinkage method . The cut -and -fill method was adopted for the lower levels . Waste rock for stope fill was provided by block-caving an area on the 600 level . Main haulage drifts were driven in the firm footwall , and crosscuts were driven across the mineralized zone at 100 -foot intervals . Grab samples taken from each car of every working place and channel samples cut every 5 feet in development work are considered sufficient for estimating ore reserves .

Jan 1, 1950

By G. Stecklein

This report summarizes the results of research into the areas of the fragmentation and entrainment of Airborne Respirable Dust (ARD). The objectives of this program were four-fold: first, to review the present state of knowledge regarding ARD; second, to expand this state of knowledge through the identification of hypothetical microscopic mechanisms by which the coal is fragmented and the dust becomes entrained; third, to specify the informational requirements to verify or nullify these hypotheses; and fourth, to relate experimental techniques that will produce that required information. Additionally, insights are provided regarding potential methods of extraction and/or treatment which may reduce the concentration of ARD.

Jan 1, 1982

By G. L. Smith

The fundamental challenge facing mineral and metal companies is how to create sustainable value while operating within mandated strategic bounds, identified constraints, and variable market and economic conditions. This can be achieved by allowing the fixed physical nature of the mineral asset to drive definition of the optimal technical solution to mining and processing activities, and developing and resourcing a strategically aligned portfolio of production entities that creates flexibility to near- and longer-term business environment shifts, i.e. a production mix that allows variation of output to respond to short term market variation, within a long term context. The practical achievement of this outcome is enabled by the concept of strategic long term planning. The core elements of strategic long term planning in the metals and minerals industry, and the relationship between them, are expanded. The strategic long term planning framework is a logic construct that enables delivery of an optimized, strategically-aligned business plan from the mineral asset portfolio using a set of tools and techniques with a common language, standards, systems and processes to align decisions and actions on a cyclical basis.

Jan 1, 2012

By Gustavo Henrique Bolognesi Donato

Este trabalho apresenta o desenvolvimento de critérios objetivos para a garantia de validade da mecânica da fratura elasto-plástica monoparamétrica, utilizando o parâmetro integral J como descritor dos campos de tensões, deformações e deslocamentos à frente de um defeito do tipo trinca. O mais importante na vertente monoparamétrica da mecânica da fratura é garantir que os campos de tensões no corpo de prova laboratorial sejam comparáveis com os existentes em uma estrutura real para cujo projeto as propriedades retiradas do corpo de prova serão utilizadas (conceito este denominado similitude). Para estabelecer critérios objetivos para a existência de similitude, esse trabalho comparou os campos de tensões obtidos de estruturas de referência sob alta triaxialidade de tensões (MBL) com aqueles obtidos de corpos de provas de mecânica da fratura em escala de laboratório. A matriz de análise permitiu a determinação dos limites de deformação M para geometrias C(T), SE(B) e SE(T) de diversas configurações e para uma faixa de propriedades de material característica de aços estruturais aplicáveis a vasos de pressão e dutos. Os resultados demonstram a baixa restrição à plasticidade de corpos de prova SE(B) e SE(T) com trincas rasas e os efeitos de profundidade de trinca e espessura nos resultados de M. Ainda, alguns comportamentos inesperados foram evidenciados, como no caso em que (para condições particulares de profundidade de trincas) corpos de prova mais finos apresentaram maior restrição a plasticidade do que amostras mais espessas. Sendo assim, o trabalho oferece uma base objetiva para que a similitude seja garantida nas avaliações de integridade estrutural baseadas na mecânica da fratura elasto-plástica suportada pela integral J, seja com seus valores críticos (Jc) ou curvas J-R.

Aug 17, 2017

By C. D. Elifrits, N. B. Aughenbaugh

Introduction Federal and state laws enacted to regulate coal mining and the accompanying public concern about the adverse effects that mining might have on land use have focused much attention on the subsidence of the land surfaces over underground mines. Some questions asked are: • Will abandoned mines subside in the future even though they have exhibited no surface adjustment to date? • If so, when will subsidence take place? • Can a specific surface area be affected by subsidence more than once? • What surface form will the subsidence feature take? • Is there any way to predict when subsidence will occur and end? An attempt is made here to address these questions insofar as it is possible with available data and experience of evaluation of subcritical extraction conditions. Mining that results in subsidence features can be classified as supercritical, subcritical, and critical with respect to the minimum span lengths of the worked-out rooms (Fig. 1). A complete basin will not develop fully immediately over subcritical conditions because the span lengths of the entries are less than the critical dimension (Wardell, 1983). Passageways, entries, and room-and-pillar panels are all included in the subcritical category. Because of the short span lengths, subcritical mining conditions tend to be stable over the life of the mine unless adverse geologic conditions exist (Gray et al., 1974; Dunrud, 1976). Various roof control and support procedures are employed to maintain entry stability during mining. Little information exists concerning the time factor of subsidence over areas of subcritical extraction. Data that have been collected relate to longwall mines, whereby the cavity sizes are designed large enough to induce caving behind the working faces so that complete subsidence at the surface occurs within a short period of time. The UK's National Coal Board (1975) has reduced the enormous amount of data it has collected to empirical correlations and has published these correlations in its Subsidence Engineers Handbook. The handbook states that "None of the foregoing remarks applies to pillar and stall working," with respect to the section discussing the time factor of subsidence caused by longwall mining (National Coal Board, 1975, p. 40). To understand and evaluate how time relates to subsidence above room-and-pillar mines, one must first recognize how mine cavities deteriorate and fail. The propagation of failure to the surface must then be studied, and, finally, the failures that are manifest at the surface in the form of depressions accompanied by both compressional and tensional movements must be investigated. Failure of mine cavities Any cavity beneath the earth's surface represents a condition of nonequilibrium and tends to close with time. Failure of cavities in a subcritical mine can be classified as failure of the roof, failure of the floor, failure of the supports (pillars, cribs), and elastic rebound of the rock. One mode of failure may dominate, but generally combinations of the four will occur. Also, initial instability of geologic materials and structural features and in situ stress may be unknown factors that can contribute to cavity failure. Roof failure is the most obvious opening stability problem in most operating mines. The bridging capabilities of the roof rock are dependent on the rock's material strength, geologic discontinuities, and reaction to humidity changes in the air of the mine. This type of failure may vary in magnitude from gradual flaking to massive roof falls. Mine floor instability can be manifest in the form of a general heave over a broad area or of individual pillar punching. The weaker and thicker the immediate floor material, the more prone a mine is to experience floor problems. Water seeping into an area can soften the underclay, reduce its bearing capacity, and precipitate failure of support for the overburden.

Jan 8, 1986

By Howard N. Eavenson

AN analysis of the bituminous coal situation by an authority who traces the production, mining, safety, markets and labor trends in comparison with other fuels. BEFORE 1918 the production of coal experienced a steady growth, with slight recessions in ouput in only twelve years (1837, 1841, 1852, 1855, 1861, 1874, 1876, 1889, 1894, 1905, 1909, 1914), and in each of these cases the loss was recovered in the following year and the increase continued. In each decade the output was doubled. Prices, while not high, allowed some profit. In 1918 during World War I, an output of 580 million tons was reached and with the exception of 1923 this total was not again reached until 1942, in World War 11. Losses of output in this period were much greater than ever before; in 1932 the total was 270 million tons less than in 1918 or 1923, and the loss after 1923 was not recovered until 1942. The greatest output was 631 million tons in 1947.

Jan 1, 1950

By Elard Rodríguez Véliz

El objetivo del presente texto es mejorar el rendimiento de las brocas a través de una serie de análisis realizados durante el programa de perforación comprendidos entre los años 1974-1977. Para ello, se utilizó una metodología que implemente un código que elimine ciertas brocas utilizadas desde 1974 al 31 de diciembre de 1977, dado que el anterior no se adecuaba a las características. Posteriormente se realiza un cuadro comparativo del motivo del deshuso del anterior código, se señalan sugerencias y resultados del análisis de brocas, así como los factores de las fallas de las mismas.

Nov 20, 1978

By N. A. Warner, R. K. Manna

Physical modelling of liquid-phase oxygen mass transfer in a water model of part of a proposed new polymetallic smelter has been achieved. A study of solute mass transfer caused by multiple, subsonic air jets contacting superoxygenated water flowing in a channel model of the smelter converting hearth has been carried out. For a wide range of channel flow rates the rate of mass transfer was found to be independent of water velocity. The water model has been used to compare mass transfer for both open-packed and close-packed multiple-lance arrays with circular nozzles of diameters 2.26, 4.95, 10.95 and 24.40 mm. It was found that with fewer of the larger-diameter nozzles a reduction of up to 58% in liquid-phase mass transfer occurred, especially for the close-packed lance configurations. This restriction of liquid-phase mass transfer would result in reduced metal losses in the analogous smelting situation. The larger nozzles, however, exhibited more jet-jet and jet-channel wall interference effects than their smaller counterparts, resulting in an effective reduction in the momentum fluxes of the impinging jets

Jul 1, 1991

By Nan Hua

As a high production and high efficient mining method, top coal caving method is now widely used in China. However, as more extra-thick coal seams are mined, it becomes more and more difficult to make the top coal fully broken up, resulting in more and more top coals flowing into the gob, rather than onto the rear AFC at the working face as designed. This research is aimed to investigate the failure mechanisms of the extra-thick top coal caving mining method.

Jan 1, 2009