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By S. Govender, J. J. L. du Plessis, R. C. W. Webber-Youngman

Spontaneous combustion (SC) is a cold oxidation reaction that generates heat, causing a temperature rise of the reactant and leading, with limited heat dissipation, to self-ignition of the reactant, which occurs without an external heat source. Although not limited to coal, the most significant hazard of SC are the fires that occur in coal mining operations around the world. These fires pose a serious risk to the safety of workers in the mines as well as adverse effects on the environment, and can affect the quality of life for current and future generations. We investigated the occurrence of SC in raw coal storage bunkers with the purpose of compiling a decision analyser for engineers designing or working with coal storage bunkers. Specific experts were interviewed from different backgrounds and companies, followed by field research at a coal mine. The important factors affecting the possibility of SC occurring were the type of coal supplied to the bunker, the mining practice, and physical conditions around the bunker. The information presented here will assist in reducing the SC risk in raw coal storage bunkers. These findings, together with the systematic decision analyser developed, will assist design engineers and mine personnel to take early preventative steps in managing SC. The decision analyser was tested for many different scenarios and gave good guidance on how to minimize and prevent SC in bunkers

May 1, 2021

By David A. Hall

We present an analysis of the propagation in a uniform tunnel of semi -circular cross section that contains two axial conductors. In particular, we show that, even if one of these conductors has high ohmic loss, one of the two propagating modes has relatively low attenuation. This corresponds to the situation where an unloaded dedicated wire is used to improve radio frequency communication in a mine tunnel that contains a heavily loaded trolley wire.

Jan 1, 1978

By Robert Mensah-Biney

The loading characteristics of gold-tetrabromide species onto a weak-base resin, PAZ-4, were evaluated using a completely mixed batch reaction system. The time. to attain equilibrium loading was substantial, on the order of several days. However, abnormally high loading capacity values of 15 to 20 meq Au/g dry resin (1000 to 1300 kgAu/tonne) were attainable in 24 hours. The loading of gold-bromo species by P AZ-4 was visualized as consisting of two processes: (i) the rapid adsorption of [AuBr4r species by simple ion exchange mechanisms and (ii) reduction of [AuBr4r to metallic gold by an electron exchange mechanism. Elution of gold from loaded resin was feasible provided the resin had not been loaded to high capacity values. If loading is carried to high levels, complete elution becomes impractical and the gold may be recovered by ashing the loaded resin. For the high loading capacities observed this option would appear to be cost effective.

Jan 1, 1991

By G. B. J. Leon, M. Karmis, C. Newman

"The prediction of surface deformations due to underground mining operations has been a long recognized practice with case studies documented as far back as 1556 in Georgius Agricola's De Re Metallica (Latin for On the Nature of Minerals). There is currently increased public awareness and regulatory scrutiny on the potential impacts of underground longwall and second mining operations, but this time the focus is placed on environmental impacts to overlaying bodies of water such as streams, rivers, wetlands, lakes, etc. (Karmis and Agioutantis, 2015). Community residents and environmental groups, as well as federal and state regulatory agencies, have often cited adverse stream impacts and demanded stronger measures and scrutiny in issuing mining and reclamation permits (Booth, 2006). Mining companies are required to focus on the protection of sensitive bodies of water through the monitoring of stream flow and water quality, management and rehabilitation techniques, as well as the adoption of ""no mining zones,"" which potentially sterilize large portions of minable coal reserves. This paper examines the use of an empirical modeling approach for the protection of surface streams based on evaluation of ground strain magnitudes. Utilizing enhanced features of the Surface Deformation Prediction Software (SDPS), ground movements can be predicted accurately in the vicinity of surface bodies of water. The modeling of ground movements can aid in establishing optimum extraction sequences, while the magnitudes of anticipated subsidence can be used in the evaluation of mitigation plans when undermining surface bodies of water. INTRODUCTION When utilizing high recovery underground mining methods, such as longwall or room-and-pillar mining, the movement and deformation of the overburden propagates toward the surface and may affect the integrity of overlying surface streams (Peng et al, 1996). Published studies cite three major mechanisms of subsidence as most likely to impact streams: displacement, slope, and strain. While subsidence-induced vertical displacement cause little structural damage to the stream bed, it may create adverse drainage and stream flow issues as the subsidence trough allows for ponding (Dawkins, 2003). Subsidence initiated changes to the slope, or tilt, of a stream may have adverse effects on water flow. As the stream enters the subsidence trough, the gradient increases providing potential erosion control problems. When exiting the subsidence trough, a reduction of the gradient may inhibit stream flow, causing localized ponding (Peng, 2008). While vertical displacement and tilt both may have detrimental effects to surface streams, subsidence induced strains have been documented as being the most damaging to surface streams and structures causing distortion, fractures, or failure (Singh, 1992). When stream beds are subjected to high tensile strain, tensile cracks may form at the surface level allowing for the direct loss of stream flow through fissures. When stream beds are located in areas of high compressive strain, rock layers forming the stream bed can fail as the stream bed, ""ruptures,"" upward blocking stream flow or having the stream diverted into the facture zone at the base (Iannacchione, et. al., 2010)"

Jan 1, 2016

By W. Blum

Progress made in improving the creep resistance of Mg alloys is reviewed with the emphasis on microstructural interpretation. Experimental results on the increase of creep strain with time at constant stress a measured for limited times and strains are displayed in a transparent form as creep rate-strain diagrams from which the minimum creep rate stress is safely derived. In addition, data on the thermal stress component a derived from high-precision a-reduction tests are reported. Within a simple statistical dislocation model these data allow one to quantify the relation between dislocation velocity v and a . In combination with structure evolution laws this relation serves as a basis for modeling the creep rate. New alloys have distinctly higher creep resistance than AZ91 where precipitation hardening plays a minor role. This is due to hardening by intermetallic phases which may form a continuous skeleton along the grain boundaries (e.g. Ca-alloyed AZ91) and/or submicron-sized precipitates within the grains (MRI230D, Mg-Zn-Ca alloys).

Jan 1, 2006

By George A. Miller

ALTHOUGH the Andean mountain belt, which contains almost all the metal deposits of the other South American nations, does not enter Brazil, this country is rich in mineral resources, for in area it accounts for half the continent and geologically it contains almost all of the Brazilian Shield. This great mass of ancient rocks has been relatively stable for a long time and forms a great area of plateaus and highlands interrupted only by the syncline which carries the Amazon River across it to the sea. Lowland Brazil - the great flood plains of the Amazon. Tocantins, Paraguay, and Parana Rivers-is of no interest to the miner, and in fact supports but a small proportion of the country's population. The highland area is divided into unequal parts by the Amazon River; the north half is underlain by the north lobe of the Brazilian Shield which extends into Venezuela as far as the Orinoco, and into the Guianas, and is known as the Guiana Highlands. Mineralization appears to have been weak in the Brazilian portion of these hills. In fact most of the ore deposits are to be found in the States of Minas Gerais and Bahia, although the neighboring states of Sao Paulo, Pernambuco, and Piauhy can also boast of some deposits. Goias and Matto Grosso are as yet incompletely prospected but are considered to contain reserves for the future.

Jan 1, 1945

By A Golsby

Although much talked about, social licence to operate (SLTO) is a relatively new concept that has been deemed as one of the four biggest business risks to a mining project over the life-of-mine. There is no accepted single definition of SLTO and this author understands SLTO to be stakeholder perception of the legitimacy of a project, a company or an industry. At a specific site, and across different sites within the same organisation, SLTO ranges through different levels according to stakeholders’ degrees of acceptance in time and space. Management of SLTO is vital for the mining sector but is difficult as it is informal and intangible. Although there are no key performance indicators, there are certain indicators that enable relative measurement of the ‘level’ of the SLTO. Because of the importance of the SLTO, information management during the entire life-of-mine, from exploration to rehabilitation, becomes crucial for the continued operation of a project. This paper identifies ten basic principles for the management of information to support the SLTO.CITATION:Golsby, A, 2014. Managing information to support a social licence to operate, in Proceedings Life-of-Mine 2014 , pp 389–398 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 16, 2014

By A Manzoori, M T. Shadloo

This paper describes a CFD modelling study which was carried out to investigate possible improvements in the design of an alumina precipitator tank at the Jajarm plant of Iran Alumina Company. In particular, the tank has an impeller located very close to the tank bottom, such that it quickly becomes covered with settled solids after a shut-down of the agitator, making it difficult to restart. A CFD model was firstly set up in which the existing design was evaluated in terms of flow pattern, off-bottom suspension and distribution of solids, and power consumption. Further simulations were then carried out to test alternative designs, leading to a recommended design, which maintains good mixing, with the same power consumption and without the use of a low-clearance impeller.

Jan 1, 2006

By L Zhang

The Chinese coal industry is the largest coal producer in the world. The total production in I995 was 1.28 bnt. On the way towards introducing a market economic system, this mature industry is facing major challenges. The main problems are a large surplus of manpower, shortage of current assets and capital, low productivity, high casualties and a huge deficit. This paper discusses the present situation and the future developments in the Chinese coal industry. The current policy can be stated as ‘rapidly developing the state collieries and improving the village and private mines; integrated development to achieve an economic operating scale and encouraging a diversified economy; rapidly exploiting and developing in the North west and South west; promoting productivity and efficiency; welcoming multi-sources and types of investment; setting up coal exchange markets; and the careful control of resources and the environment'.

Jan 11, 1996

By C. M. Campbell

THE dire effects of rapidly vanishing natural resources, widespread unemployment, and increased debt and taxation in recent years have challenged Canadians to produce a practical solution to these national economic problems. In more recent months, wars and rumours of war have indicated, among other things, the need for better control of our mineral wealth. The erection of a smelter on the lower mainland coast of British Columbia, treating all Western ores, and such ores as it will be found advisable to import, will make an important contribution toward a solution of these problems. It is believed that the ores tributary justify a smelter of major proportions. A stock-taking to confirm this can be made with reason-able accuracy in a short time, and this should be undertaken without delay. Enough general information is, however, available .in this paper to justify the technicians of the Department of Mines at Ottawa and of interested smelting companies making a preliminary study of the matter. THE DEFENCE ARGUMENT As a factor in rearmament, metals play a vital part. That rearmament is to continue on an increasing scale is indicated in Premier Chamberlain's address of October 3rd last, when he said: ?'For a long period now we have been engaged in this country in a great programme of rearmament which is daily increasing in pace and volume. let no one think because we have signed 'this agreement between the four powers at Munich we can afford to relax our efforts or call a halt in our armaments at this moment'. As matters stand, the facilities in British Columbia are entirely out of line with the strategic importance of this Province as the Western Front of Canada and the Empire. All our copper ores, and an appreciable part of our lead and zinc ores, are sent for treatment to Japan, United States, and Europe, while we import our iron and alloys. A treatment plant on this Coast would not only give us control of war metals and chemicals but it would provide an increased industrial and research population, badly needed in this area and of the greatest value in the case of war. This is where the mining industry can do its bit.

Jan 1, 1939

By L. M. Pero

The paper summarizes aspects of the recent literature on mineral development in the Third World. The emphasis is on publications covering agreements between host governments and mining companies.

Jan 1, 1985

Currently an Australian Standard for tunnel fire safety is being developed for road and rail tunnels. Other local guidance relating to tunnel fire safety that has recently become available includes publications by both the Roads and Traffic Authority and RailCorp of New South Wales. Internationally, the World Road Congress has completed its 2004 - 2007 cycle, which has resulted in a number of publications. International developments in rail guidance include a new European Standard regarding fire safety in railway tunnels that will come into effect in July 2008. In addition, the National Fire Protection Association committee NFPA 130 are in the process of revising their standard for fixed guideway transit and passenger rail systems, which is due for publication in late 2009. This paper outlines the status of these and other recently published relevant local and international fire safety guidelines and their implications for tunnel projects in Australia.

Jan 1, 2008

By M. H. Dunn, T. P. Danehy, C. F. Denholm, S. L. Busler

The problems associated with abandoned minelands are so extensive that neither federal, state, or local governments nor the mining industry nor watershed groups can adequately address these problems individually. By combining talents and resources, however, these problems are being solved efficiently, effectively, and economically. Utilizing existing water monitoring data, local public-private partnerships have successfully designed and built passive systems within five weeks to six months which treat discharges up to hundreds of gallons per minute that vary in quality from net alkaline to highly acidic, containing as much as 200 mg/L dissolved iron and 70 mg/L dissolved aluminum.

Jan 1, 2002

By Y. Mitani, F. Vallier, T. Esaki

Shear-flow coupling tests are conducted using an original apparatus, and a shear-flow coupling model using Geographic Information System (GIS) is developed in order to evaluate shear-flow coupling properties of a rock joint. Shear-flow coupling tests indicate that the hydraulic conductivity of joint once decreases, and then rapidly increases at the shear displacement near the peak shear stress. The proposed model simulates the test results relatively well. However it indicates that it is difficult to apply the local ‘cubic law’ model in the initial shear stage, in which the change of selective flow path is remarkable. Scher-Fliess-Kopplungsversuche werden mit einem neuartigen Versuchsgerät durchgeführt und mithilfe von Geo-Informationssystemen (GIS) gedeutet, um so ein Modell für die Scher-Fliess-Kopplung in Gebirgstrennflächen zu entwickeln. Die Versuche zeigen, dass die hydraulische Leitfähigkeit zuerst abnimmt, dann aber schnell wieder zunimmt sobald die maximale Scherfestigkeit erreicht ist. Das vorgestellte Modell bildet die Testergebnisse relativ gut nach. Es zeigt auch, dass es schwierig ist, das lokale Cubic Law im Initialstadium der Scherbeanspruchung anzuwenden, in dem die Variationen selektiver Fliesswege gross ist. Les essaies hydro-mécaniques couplés en cisaillement sont réalisés grâce à un appareil éxperimental prototype et un modèle de couplage hydro-mécanique utilisant le S.I.G (systeme d'information géographique) développé dans le but d'évaluer les propriétés hydro-mécaniques des joint rocheux. Les résultats indiquent que la conductivité hydraulique des joints décroit puis augmente rapidement en se rapprochant du pic de cisaillement. Le modèle proposé simule relativement bien les résultats expérimentaux ; mais indique également qu’il est difficile d’appliquer localement la loi cubique au début du cisaillement où, les changements d’orientation dans le réseau d'écoulement sont considerables.

Jan 1, 2003

Numerical simulation of the fluid flow and heat transfer has been carried out for a waste-heat boiler in an Outokumpu type copper flash smelter. In this boiler, SO2-containing off-gas flows into the waste-heat boiler radiation section at about 1350°C. A fraction of cooler off-gas from the electrostatic precipitator at about 200°C was recirculated into the radiation section, and a small amount of ambient air was leaked into the boiler from the bottom. The computational results show that the flow is strongly recirculating and distinctly three dimensional in most of the boiler, particularly in the radiation section. The hot off-gas cooled down rapidly after entering the radiation section due to radiation. The predicted flow pattern and temperature distribution were in a good agreement with laboratory models and industrial measurements.

Jan 1, 1995

By A. I. Kogut

Impurity minerals in fluorspar ores and concentrates from a deposit in Southern Africa have been studied by reflected light, transmitted light, and cathodoluminescence microscopy. The principal impurities are quartz, calcite, aegirine, apatite, ankerite, magnetite, goethite, and synchysite [Ca(La,Ce,Nd)(CO3)2F]. Cathodoluminescence microscopy was found to be very useful in studying the character of the fluorite and especially for recognizing the presence of apatite and calcite impurities. Fluorite exhibits blue, calcite shows yellow, and apatite has white, light purple, and pink cathodoluminescence. The cathodoluminescent character of apatite varies with its geological environment and position in the orebody. The results of this microscopic study show that phosphorus present in fluorite concentrates occurs principally in binary locked apatite-fluorite particles. Successive fluorite cleaner concentrates contain progressively smaller amounts of locked apatite-fluorite particles. Free apatite has been effectively partitioned to the final tailings.

Jan 1, 1995

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 J. A. Morgan, W. A. Barclay, J. C. Pedersen, I. C. Campbell, D. S. Bubar, R. P. Taylor

"Abstract - The Lilypad Lakes property is host to a group of Ta-mineralized dikes that occur over an area of at least 10 km2. Field relationships are consistent with a syn- to late syn-tectonic timing for their emplacement (with respect to the major regional D1 episode of deformation), with several of the dikes exhibiting a steeply dipping, open, S- to M- to Z-shaped fold geometry. Individual dikes range up to 30 m wide (Rubellite Dyke, Pollucite Dyke), have strike lengths of up to 750 m (e.g., JJ Dyke), and are continuous to depths of greater than 250 m (e.g., Rubellite Dyke, Pollucite Dyke). Typically, they display sharp intrusive contacts characterized by the development of thin, holmquistite-rich haloes. The Tamineralized dikes are comprised of silica- and alumina-rich, sodic, granitic pegmatites that display extreme levels of geochemical fractionation (K/Rb typically < 10.0, as low as 2.2; Nb/Ta typically < 0.20, as low as 0.03), and enrichments in an economically important group of lithophile elements, most notably Li, Rb, Cs, and Ta. Geochemical assays of individual surface grab and drill core samples have yielded values as high as 1.51 wt.% Li2O, 1.25 wt.% Rb2O, 6.21 wt.% Cs2O, and 0.108 wt.% Ta2O5. Diamond drilling has established the presence of wide (~20 m), potentially ore-grade intersections of Ta mineralization (>0.045 wt.% Ta2O5) in both the Rubellite and the Pollucite Dykes.Three Ta-oxide minerals (microlite, wodginite, manganotantalite) of primary origin predominate in the Ta-mineralized dikes, where they occur as fine, disseminated grains in the albite-rich pegmatite matrix. The sequence of crystallization is typically manganotantalite wodginite microlite, which conforms to a well-established paragenetic sequence for rare-element granitic pegmatites in general. All three of the primary Ta oxides are characterized by a high degree of chemical purity (e.g., average Ta concentrations in microlite from 77-79 wt.% Ta2O5), a compositional feature consistent with the extreme levels of geochemical fractionation characteristic of the host granitic pegmatites, and one that indicates that the Lilypad Lakes pegmatites are likely to produce Ta mineral concentrates of the very highest quality.Locally, a second generation of Ta minerals is present, restricted to small vugs in the pegmatite matrix that are surrounded by fine aggregates of K-rich mica or clay. The secondary Ta minerals are dominated by microlite, which is typically intergrown with fluorite and Fe-sulphides, and is distinguished from its primary counterpart by its lower Ta content (around 70 wt.% Ta2O5) and much higher concentration of uranium (up to 9 wt.% UO2). Also, secondary microlite consistently yields low analytical totals from electron microprobe analysis, suggesting that it is H2O-rich. The presence of this second, vug-related generation of microlite, together with the occurrence of localized networks of crosscutting fractures that host high concentrations of Cs and Rb (in the minerals pollucite and Rb-Kfeldspar), suggests that a late-stage, fluid-dominated metasomatic/hydrothermal event may have been important in certain sections of the dikes, and has effected a redistribution of the economically important elements Ta and Cs."

Jan 1, 2005

By Richard A. Allwes

The Bureau of Mines conducted an in-mine case study on two consecutive three-entry gate road systems designed in accordance with the stiff-yield pillar design concept. This Bureau study was conducted in order to further develop technology that will improve the health and safety aspects of longwall mining. Support loading and strata activity were monitored to determine the effects of retreat longwall mining on the gate road ground control system. Analyses of pillar stress and roof bolt loading histories revealed that headgate roof support elements ex-perienced cumulative loading throughout the life of the longwall panel. Tailgate pillar loadings had significantly different histories from the loading histories of the headgate pillars. Stress relief occurred in the tailgate pillars following the passage of the longwall face. More-over, the stiff-yield pillar design, with the abutment pillar placed adjacent to the working panel when part of the headgate system, provided effective ground control in that no major roof falls or roof problems were experienced in the headgate or tailgate systems during longwall mining.

Jan 1, 1985

By Edward L. Wilson

A general computer program is given for the linear elastic static analysis of complex structural systems. These elements have special advantages for the analysis of massive underground structures such as mine structures and above ground structures such as arch dams. New finite elements are developed which are useful in the analysis of two and three dimensional solids. Examples are given which illustrate the accuracy of the elements. A description on the use of the program and a FORTRAN IV listing are given in the Appendices.

Jan 1, 1971