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By D. A. Paice

Direct current electrical systems are used in most coal mines primarily to power the main haulage trains and secondarily to feed other equipment and passageway lighting. Electrical power is supplied from rotary machines or static rectifier equipment and is distributed through the mine by open trolley wires and feeder cables. The rails of the haulageway are used as a current return path. This exposed power distribution system is very vulnerable to conditions which lead to undesired leakage currents and short circuits and, consequently, the possibility of fires or other hazards to personnel. Present techniques and equipment have been utilized in so far as practical to improve the safety of the dc electrical system; however, there still appears a need for further improvement. Because of this need, this program was sponsored by the Bureau of Mines to investigate two specific technical areas related to improvement of dc electrical system safety. One area included the determination of the characteristics of mine electrical systems and their protection requirements and the verification of the adequacy of available protective devices for mine service. Despite the widespread application of industrial protective equipment in mines, there was little detailed technical information available related specifically to the performance of this equipment in service. Our task was not only to develop useful information regarding mine system protection, but also to define and verify the adequacy of the protective devices available. The second area of investigation called for development of a practical technique for detecting low level electrical fault or leakage currents. Conventional protective devices

Jan 1, 2012

By J. W. Wilson, P. C. Graham

SUMMARY The Witwatersrand quartzites in which South African gold mining operations are moat exclusively conducted, are notoriously difficult and costly to drill. Despite this situation, however, with the high cost of developing new mines and extending existing mines, together with the rising cost of labour and mining problems resulting from the ever-increasing depths of workings, the demand for raise-boring in these formations is increasing rapidly. Not only is the demand for raises and shafts increasing, but also the length and size of these excavations. Raise-boring studies carried out in South African gold mines have indicated that increased penetration rates and possibly reduced costs could be obtained if higher thrusts were available at the reaming head. Until fairly recently there has been no raise-boring machine suitable for underground use that possessed the thrust and torque characteristics necessary to achieve high penetration rates in hard abrasive quartzite formations and the cutters available were not really developed for high loading. In response to these requirements a raise-borer, the Robbins 83R was designed and built in Seattle, U.S.A. for the Anglo American Corporation. This machine is operating in South African gold mines and is currently being used at a depth of 12 000 ft below surface in one of the. Group's mines. The initial raises bored have substantiated that increased penetration is attainable at high thrust and it is now apparent that the machine is sufficiently versatile to drill raises of up to 12 ft in diameter in quartzite formation over a length of 2 000 ft.

Jan 1, 1974

By Eric S. Lindquist, Charles A. Luxford

The State of Texas recently adopted a master plan to expand the existing Capitol Complex in Austin. Phase 1 of this expansion will add two new State office buildings and five levels of underground parking to the existing Complex. Additionally, a landscaped pedestrian mall will be built atop a portion of the underground parking to enhance the area as a cultural destination. Capitol Complex website: https://www.tfc-ccp.org/ Brierley Associates was selected to provide detailed design of the entire Phase 1 earth retention system for an approximately 40-65 ft (12-20 m) deep, 500,000+ yd3 (380,000+ m3) excavation through overburden soils and limestone bedrock. To facilitate overall project coordination, all design packages were required to develop Revit models, including the retention system package. With the project located in an urban setting, this 3D model also facilitated coordination of the retention system with adjacent major structures and utilities. The retention system is a combination of soil nails, soldier piling with tiebacks and rock anchors with a shotcrete facing as a substrate for the below-grade blindside waterproofing system. Due to the substantial scope of excavation, a significant number of utilities had to be routed on a temporary span over the excavation. Brierley Associates designed this utility support structure, which required extensive coordination with the excavation support and existing utilities located directly underneath the structure’s foundations. Preconstruction geotechnical work identified a fault zone that might be encountered within the excavation; however, the fault feature was found to have a more adverse location and orientation than originally anticipated. This observation required that a portion of the temporary anchors be converted to higher-capacity, corrosion-protected permanent anchors.

By B. DANIEL MARJAVAARA, I. A. SOFIA LARSSON, ANNA-LENA LJUNG

One way to upgrade iron ore is to process it into pellets. The pelletizing process is multifaceted, involving complex fluid dynamics with highly turbulent, high-temperature flow in intricate geometries. This makes it hard to perform measurements during operation, so a useful tool for better process understanding is computational fluid dynamics (CFD), where the challenge is to perform efficient and trustful simulations of complicated problems. A validated simulation model can be valuable for increased process control and development. In this paper, the flow field and coal combustion process in a pilot-scale iron-ore pelletizing kiln is simulated using a CFD model. The objective of this work is to apply a coal combustion model to enable an investigation of thermal effects from the flame on the surrounding flow field.

By Ting Lu, Gerard Laman

"This document compares the systems of coal classification described under ASTM standards used in Canada to GB standards used in China. A preliminary connection of metallurgical coal classes was set up between the two classifications. In GB classification system, there are nine metallurgical coal groups, namely PS, SM, JM, FM, ½ ZN, RN, 1/3 JM, and QM used in coal blending for coke production. PS coal is almost equivalent to the Low Volatile Bituminous coal; SM, JM, and FM coal groups fall into Low to Medium Volatile Bituminous range; ½ ZN, RN, 1/3 JM, and QM are equivalent to bituminous coal with medium to high volatile matters; QF contains higher volatile bituminous coal compared with High Volatile Bituminous coal. The caking properties commonly used in respective country are also compared in this document. These properties include free swelling index (FSI) and maximum fluidity used in Canada, as well as caking index (GR.I.), and the maximum plastic layer thickness (Y) mainly employed in China. It has been observed that the log of the maximum fluidity has a stronger correlation with the caking index than the Y values. Metallurgical coal processing strategy and typical coking coal product qualities are briefly discussed in the last section of this paper. Currently there is a trend to use heavy medium cyclone in both countries. In Canada the conventional two-product cyclone technology is the preferred practice; whereas in China the three-product heavy medium cyclone arrangement is widely used.INTRODUCTION Coal can be simply classified by applications into two categories: i) thermal coal used to provide heat energy in combustion, and ii) metallurgical coal which is converted to coke, in a carbonization process, and used mainly in the iron and steel industry. Metallurgical coal contains even higher heating values than thermal coal. In addition, it presents unique plastic properties during carbonization which in turn produces a porous solid, high in carbon referred to as coke. Coke is one of the most important raw materials in the iron and steel industry."

Jan 1, 2012

By Sergio N. Monteiro

Jute fiber reinforced polymer composites are among the most investigated and applied natural composites. In this past decade the mechanical properties of these composites has been assessed for various types of test conditions. However, the reported results correspond mainly to short-cut jute fiber composites, which do not present the highest mechanical strength as compared to continuous fibers of the same kind. In order to complement these results, the present work evaluated the mechanical behavior, by means of flexural tests, of polyester matrix composites reinforced with continuous jute fibers. Bend tests were conducted in standard specimens with up to 40% of jute. Fracture analysis by SEM displayed the rupture mechanisms. The results showed an improvement in some flexural properties with incorporation of jute fiber. However, a low fiber/matrix interfacial stress was responsible for limitation in the values attained by some properties.

Jan 1, 2010

These proceedings consist of papers presented at two Bureau of Mines Technology Transfer Seminars for the purpose of disseminating recent advances in mining technology related to coal mine fire and explosion prevention. Primary, although not exclusive, emphasis is placed on underground coal mining. The papers address research accomplishments ranging from methods for detecting mine fires to remote sealing systems for extinguishing coal mine fires. Each paper represents the current state-of-the-art in the respective research categories. Presentations include research occurring from both Bureau in-house and contract efforts.

Jan 1, 1978

By S Jephcott

The McArthur lead-zinc-silver deposit is of the stratiform type. It consists of a mineralised bituminous shale sequence containing some tuffites, numerous graded beds and isolated slump breccia horizons. The principal sulfides; pyrite, sphalerite and galena, are essentially restricted to the shales and the genetically unrelated turbidites contain only minor mineralisation. The geochemistry of the deposit has been investigated with respect to the stratigraphic column and mineralogy of the sediments. A sedimentary origin is advocated for the deposit. Volcanism, thermal spring activity and high salinities, perhaps related to the Emu Fault, are considered as contributing factors to ore genesis. The metallurgy of this deposit is discussed in relation to its geologic history.

Jan 1, 1971

By D. E. Pollock, T. W. Beck, J. A. Organiscak

This work presents the findings from a number of NIOSH studies evaluating the impacts of emerging technologies that may reduce dust exposures for continuous mining and roof bolting personnel. These technologies include use of a wet head cutting drum on a continuous mining machine that places water sprays on the cutting drum instead of placing them on a manifold outby the drum. Evaluations at two separate operations showed that the use of the wet head sprays reduced dust levels at the miner operator in the return air, although these reductions were quite variable. NIOSH also assessed the effectiveness of a canopy air curtain for protecting roof bolting personnel. The data showed that dust levels were lower beneath the air curtain than outside the air curtain. This study also suggested several future modifications to the air curtain to in-crease its effectiveness. Finally, NIOSH evaluated mist drilling technology for its effectiveness in controlling respirable dust exposures of bolting personnel. A recent study showed that higher dust levels existed around a machine using the mist system compared to a machine using a conventional vacuum system for dust control. Unfortunately, the true impact of mist drilling was confounded by this machine operating downwind of the continuous miner for much of the study.

By Giorgio De Tomi, Ricardo Tichauer

Mineral exploration is a critical step for success in mining. However, small-scale mining often ignores exploration best practices. This paper introduces the Tichauer-DeTomi Matrix, a tool for assessment of geological uncertainty in small-scale mining. This matrix, which measures the level of compliance of exploration programs in small deposits with industry best practices, has been applied to three small mining projects in Brazil: an artisanal gold mine in the Amazon, a small-scale manganese mining venture in the Northeast, and a small manganese deposit in the Southeast. The application of the matrix resulted in indexes that reflect the actual level of maturity of the mineral exploration program in each project. Therefore, the matrix has shown potential to be an effective tool for assessment of the geological uncertainty remaining in small-scale mineral projects, as well as to identify priority exploration activities for reduction of risks associated with the geological uncertainty. As a risk assessment tool, the TichauerDeTomi Matrix may be helpful in promoting investment and sustained development in and around small mines.

The sphere of operations of dry crushing has been so much enlarged of late years that the following notes with reference to its advantages and limitations, and also some practical results in connection with the crushing of gold ores will probably be of service to the members of the Institute. Until recently, with one notable exception that of the Mt. Morgan Gold Mine, dry crushing has only been practiced to a very limited extent in Australasia, and elsewhere it might be said to belong to industries other than mining Its sphere of usefulness depends on the fact that the' product is delivered in a dry state without the separation of the finer particles from the coarser to any appreciable extent, thus enabling the following advantages to be achieved with different ores.

By L. Russell Van Wert

DURING an investigation in which the solubility relations of the phases in Muntz metal (60 per cent. copper, 40 per cent. zinc) were under study, certain phenomena that had no immediate connection with the main problem were observed, which were thought sufficiently interesting to study further. Because of lack of time, only a preliminary survey was made of two of these; namely, the cleavage structure developed under certain conditions in a 60:40 brass and abnormal grain growth in this alloy. CLEAVAGE STRUCTURE IN HEAT-TREATED MUNTZ METAL Carpenter noted many years ago that cold-working a brass of the Muntz metal type, which had been quenched previously from within the beta field, results in a partial breakdown of the supersaturated beta solution and the precipitation of the solute (the alpha solution) in the cleavage planes of the beta grains. This manner of rejection of a solute from a metastable solid solution is not peculiar to this particular alloy, for among others, it occurs in the cold-working of certain austenitic steels; for example, the austenitic nickel steels. In these ferrous alloys, cold deformation produces a partial decomposition of the austenite, with the formation of martensitic "needles" and zigzags in the austenitic poly-hedra. It is interesting to note that while the two solid solutions-austenite and quenched Muntz metal- are metastable and in their mode of decomposition behave quite alike when deformed in the cold, the metastability of each results from a different cause; viz., that of the austenite from the fact that it is a supercooled solution (its solvent, gamma iron, at ordinary temperatures is below its normal stable range) whereas the metastability of the quenched Muntz metal is the result of supersaturation.

Jan 1, 1929

By M. Carrales

This Bureau of Mines report presents information on the sulfur content of crude oil in the United States and in some foreign countries. Data are presented for oil produced in 1971 from fields in 26 States that accounted for about 76 percent of total U.S. oil production; the foreign data cover fields in 24 foreign countries that accounted for about 64 percent of the total oil produced from these countries in 1971. Most of the data are presented in tabular form.

Jan 1, 1975

By Mike Cammack, Logan Huppert, Gustavo Azpilcueta

During the summer of 2015, Unisea Inc. sought proposals for the G1 Dock Replacement Project in Dutch Harbor, Alaska. It would be a one year project and construction was scheduled to begin in the spring of 2016. One aspect of the project was the requirement for a layer of armor stone to protect part of the dock. An estimated 30,500 tonnes (37,670 t) of armor stone were needed for the project. The source of rock was the Unisea Quarry due to its proximity to the project and the quality of the stone meeting all the required technical standards.

Jan 1, 2018

By Richard A. Winters

In 1985, at the request of the U.S. Bureau of Land Management, the U.S. Bureau of Mines studied 34,000 acres of the 58,040-acre Little Jacks Creek Wilderness Study Area (ID-111-6) in order to evaluate the mineralized resources. The study area is located in Owyhee County, 10, about 21 miles southwest from Bruneau. No mining districts are in the study area, nor were any mines or claims recorded or found. The northern half of the area was covered by oil and gas lease applications; all were cancelled prior to 1985. No economic concentrations of minerals were found in the study area. INTRODUCTION This report describes the USBM (U.S. Bureau of Mines) portion of a cooperative study with the USGS (U.S. Geological Survey) to evaluate mineral resources and potential of the Little Jacks Creek study area at the request of the BLM (U.S. Bureau of Land Management). The USBM examines individual mines, prospects, claims, and mineralized zones, and evaluates identified mineral and energy resources. The USGS evaluates potential for undiscovered resources based on areal geological, geochemical, and geophysical surveys. Results of the investigations will be used to help determine the suitability of the study area for inclusion into the National Wilderness Preservation System. Although the immediate goal of this and other USBM mineral surveys is to provide data for the President, Congress, government agencies, and the public for land-use decisions, the long-term objective is to ensure the Nation has an adequate and dependable supply of minerals at a reasonable cost.

Jan 1, 1986

By R. Horn

The financial performance of the mining industry, measured by return on equity and capital employed, has been inadequate for many years. Consequently, mining companies are not valued highly by stock markets. Among the more important causes for the decline in the sector are the conservative working practices and reluctance to adapt to change or to develop new technology, although some relatively recent developments such as SX-EW copper and heap leach gold have made a significant impact on the cost base of these metals. The subsidiary business of metals exploration suffers from the same problems as the rest of the industry. The rate of discovery of ore deposits has been falling over many years and since the late 1990s, there has been a sharp reduction in global exploration activity that, if it continues, will further reduce the global supply of new ore reserves. New technological developments, particularly in geophysics and different operational practices may help reverse this trend. Statistical methods for evaluating the risk of ore reserve estimates will also improve the economic return on new mining ventures. The science of ore geology has potential to reduce exploration risk, but modern ore genetic theory has not contributed greatly to recent discoveries. The junior exploration market has almost ceased, but a new style of technically specialized efficient small exploration company has emerged which, in alliances with major companies, may be the vehicle for future global exploration. Exploration in virgin terrains has a higher risk discounted potential for the discovery of very large orebodies than that in known mining districts but mining companies have little financial incentive for this high risk exploration because of the very long lead time to production. Alliances of two or more companies reduce the risk in both the exploration for and development of major new mining projects. If new orebodies are not found, then metal prices will inevitably rise in the long term. Governments of industrial countries, particularly those with a significant mining industry such as Canada, should therefore provide assistance to exploration in order to maintain their existing industry and prevent a metals shortage from developing in the future with its consequent impact on the world economy and increased environmental damage as large lowgrade orebodies are developed to supply an expanding market.

Jan 1, 2002

Ore sorting is a high capacity, low cost method of pre concentrating ores and in some cases of producing a marketable concentrate. In most cases it is applied to run of mine material, immediately after primary crushing and screening in sizes ranging from 10 mm to 150 mm. Recent developments in bulk sorting of friable uranium deposits have resulted in machines capable of handling fine materials with sensing and separation being achieved on a zone by zone basis. Modern ore sorting machines rely on the synchronous operation of four internal subsystems, feed presentation, sensing, data processing and separation. A variety of different sub systems is available which can be combined in various forms to produce sorters capable of handling a wide variety of mineral types. The benefits in using ore sorting cover a wide range of situations and are applicable to both established mines as well as new mining ventures. Reduced operating costs, increased productivity, capital savings, energy and resource conservation and environmental issues are all part of the reason why ore sorting is finding rapid acceptance in today's mining industry. The suitability of different ore types for pre-concentration using anyone of the variety of ore sorting systems can be quickly established using computer based techniques which require only small samples of the materials under investigation.

Jan 1, 1980

By John Zeni

In Australia during the 1990s, Zeni Drilling took on several demanding shaft boring contracts. This paper describes the safety, operational, technical and environmental advantages derived through the implementation of mechanized boring methods for two of these projects. The paper first describes a 3-meter (10 ft) diameter access shaft blind bored from an underground location to 440 meters (1,444 ft) deep for a gold mine in Tasmania. The construction of a 5.8-meter (19 ft) diameter, 515-meter (1,690 ft)deep ventilation shaft for a longwall coal mine in New South Wales is also described.

Jan 1, 2001

By Edmund J. Cardoza

WELCOME TO THE DEEP FOUNDATIONS INSTITUTE 26TH ANNUAL CONFERENCE AND WELCOME ESPECIALLY TO THIS SEMINAR ON NON-DESTRUCTIVE TESTING OF DRILLED SHAFTS, PRESENTED BY MEMBERS OF THE DFI DRILLED SHAFT COMMITTEE. MY NAME IS ED CARDOZA; I AM A VICE PRESIDENT WITH THE MILLGARD CORPORATION, A DRILLED SHAFT CONSTRUCTOR FOCUSING PRIMARLY IN THE EASTERN HALF OF THE UNITED STATES.

Jan 1, 2001

By J. D. Findlay

The demands on development in London in recent years has led to the increasing use of top down construction methods in which there is a requirement to place steel columns to high tolerances into large diameter bored piles with deep cut-offs. A number of different proposals for the sequence of construction are being suggested. The tolerances requires for the steel columns are becoming increasingly stringent. This review examines a number of basic construction proposals and comments on the problems and solutions used by foundation contractors to provide the required foundations.

Jan 1, 1989