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By B. H. Bergstrom, C. L. Stevenson

In any process wherein materials must be pelletized, a crucial period exists during the interval between the manufacture of the green pellets and their subsequent heat treatment. The pellets must possess sufficient strength and plasticity to withstand conveying and sizing. Also, they must be neither excessively brittle nor excessively plastic when placed in a bed on a traveling grate for heat treatment. An acceptable pellet, in the event sufficient forces are applied to cause its fracture, will merely split into two or three large fragments which would not drastically alter the permeability of the pellet bed. However, when brittle pellets are broken, they shatter so that the resultant fine particles either decrease the perimeability of the bed or become entrained in the gas stream and thereby cause dust problems. On the other hand, excessively plastic pellets may not break at all but may merely flatten. This would seriously hamper bed permeability. In the past, pellet evaluation has usually been left to the creative and artistic talents of the balling operators. A multitude of techniques have evolved, of which the most common is the simple compression test. For this test a hand-operated device loads single pellets to fracture, but reliability is strictly operator- dependent. Probably the next most common test is the drop test, which is conducted according to several different procedures. This is an important quantitative test for estimating the amount of handling a pellet will withstand. There are many other tests, such as pinching a pellet between the thumb and index finger, but none are capable of producing reproducible results.

Jan 4, 1962

By Joe E. Bryan, John P. McDonnell

"Underground mine rib stability is an ongoing safety issue in all mining applications. Rib-related accidents present at least as many problems as roof-related ground control. Underground coal mine rib safety is continually emphasized as a primary safety concern at every mining operation. The application of rib support materials is increasing as more difficult mining conditions are experienced due to deeper cover, more variable depositional environments, thicker seam heights, and multi-seam mining effects. As the coal seams become thicker, the need for rib control increases. A variety of rib control methodologies has been documented and research continues on mine design methods and support techniques to reduce or eliminate rib-related accidents.This paper presents an alternative rib bolting technology using proven conventional rib support systems that allows mine personnel to more efficiently install rib support during development operations. This alternative rib bolting method allows for additional rib support with a single support installation.INTRODUCTIONRib control continues to garner the watchful eye of both concerned operators and government officials due to many factors: inherent safety within entries and crosscuts, actual rib stability history, safety improvement, cost control, improved mining methods, and maintaining production goals. As demonstrated through many years of actual practice, desired outcomes can be achieved by scrutiny, innovation, and combining improved practice methodologies.Rib surface control continues to be a necessary part of the production process. However, production and safety issues persist at the point of installation using current control apparatuses and methods to install rib controls. Among others, current issues of rib control are quantity of bolts required, overall time required for installation, ease of apparatus installation, flexibility of the system for appendage installation and operator exposure. A need exists to decrease the time miners spend installing rib control apparatuses, while increasing the safety of such installation processes. At present, installing rib control devices (primary rib bolts, plates, mesh, and, in most cases, secondary rib bolts and plates) is performed in a very congested area and is time-consuming process at the primary coal-winning area: the face. The MatLok system addresses these problems."

Jan 1, 2015

By A. G. Starliper

The Bureau of Mines made laboratory investigations to determine the feasibility of utilizing fine tungsten wires to reinforce a number of nonferrous metals and alloys and a superalloy, S-8l6. The composites of tungsten filament and metals were chosen to attain elevated temperature strength and corrosion resistance. Oriented clean or precoated tungsten wires were incorporated with the other metals by extrusion, swaging, and infiltration casting. Although widely varying characteristics were found in the composites, none were considered satisfactory for high-temperature use, chiefly because of reactions between the matrix metal-tungsten surface. Diffusion, solution, and chemical reactions between matrix and tungsten wires were sufficiently slow for some combinations, such as 15 v/o 8-816, to exhibit increased high-temperature strength for a limited time. A few metals failed to wet or bond to the tungsten surfaces, while a few responded after precoating with a third metal.

Jan 1, 1968

By Mark Newton Lowry

In the garden of national problems recognized by the American public, imports of mineral products is a hardy perennial. Concern for the security of mineral supplies has preoccupied nations since the industrial revolution and the mechanization of warfare. Since 1973, Americans have also been sensitized to the potential economic costs of overseas mineral supply disruptions and the cartelization of foreign production. Though oil prices have plunged since 1981, the import dependency issue remains topical. Political turmoil in Southern Africa reminds us that mineral supply disruptions will occur in the future as they have in the past. Producers of iron and steel, copper, and refined petroleum products seek protection from imports on national security grounds. The Reagan administration is proposing sweeping changes in the management of the federal mineral stockpiles. s an enduring need to take stock of the mineral trade position of the United States. This article considers the changing role that the U.S. has played in the twentieth century in non-fuel minerals trade. We begin by enunciating some principles that are useful in analyzing this trade. The changing pattern of trade in the 1900-1969 period is then reviewed. There follows a more detailed analysis of mineral trade trends in the 1970-84 period. Some consideration is given in the final section to the significance of non-fuel mineral trade for the U.S. economy. THE ECONOMICS OF U.S. MINERAL TRADE The allocation of non-fuel mineral products in the United States has in this century been accomplished primarily through the market mechanism. Except where trade barriers have distorted price signals, this means that mineral supplies have been obtained from the least cost source, with little regard for their country of origin. Mineral prices facing U.S. firms are sensitive to shifts in the domestic supply and demand, but are also sensitive to economic conditions overseas. The balance of trade in each mineral product has depended on the amount that is profitably produced and consumed domestically at the world price. The nation has produced exactly as much as it has consumed only by chance. U.S. demand for non-fuel minerals is derived from the demand for manufactures, farm commodities, and other goods whose production requires mineral products as inputs. The demand for such goods can be quite volatile, and in most industries moves cyclically due to its sensitivity to the level of aggregate economic activity. The supply of mineral products depends on the cost of extracting and processing mineral raw materials. These costs do not vary greatly in the short run. Because of these attributes of mineral markets, U. S. trade in mineral products fluctuates considerably from year to year. Most of this volatility results from shifts in domestic and overseas demand and from changes in exchange rates and trade barriers. Longer run changes in the mineral trade pattern can also be discerned. These depend on secular trends in demand and in the cost of mineral extraction and processing at home and overseas. The United States was originally endowed with extensive reserves of an array of mineral-rich ores and fossil fuels. It is also a nation with an entrepreneurial climate and technological capability conducive to extracting and processing those reserves. Not surprisingly, it has at one time or another ranked among the world's leading producers of a great many mineral products. With a population that is large and an economy that is technologically advanced by world standards, the U.S. has also been a leading consumer of mineral products. Because of its voracious appetite, the bulk of mineral products produced domestically has traditionally been consumed domestically as well. Net exports have been sizable only in those industries in which the nation has enjoyed an extraordinary cost advantage. Depletion has gradually reduced the cost advantage that the U.S. mining industry once enjoyed. The economic conditions that encouraged early development of U.S. mineral resources have

Jan 1, 1986

A wide range of materials are used in hydraulic backfilling operations and the pipeline flow behaviour of these mixtures varies considerably. It is shown that despite the large differences in constituent materials and flow behaviour, a common approach can be applied to analysing the flow of all hydraulic backfills. This is extended to include a rational design approach for backfill distribution systems. The use and limitations of pipe loop tests as a design aid is discussed. Backfill quality control is identified as a key area where improvement needs to be made to enhance the reliability of backfill system operation.

Jan 1, 2001

By Scott A. Shapkoff

High strength cable strand supports are predominately used as a supplemental means of ground control in longwall and development operations in the U.S. The advantages of cable strand supports have been documented and include flexibility, strength, and ease of installation. Since the majority of cable supports installed in the U.S. today are partially grouted, and this same segment of supports has no inherent installed tension, the supports are considered currently arbitrarily strictly supplemental and therefore, cannot currently be deemed primary support (in most mining districts). This paper details and discusses two distinctly different configurations and the technical advantages of active partially grouted cable supports for certain primary support applications. The evolution of the designs for both systems is highlighted. Field data illustrates the amount of active load in relationship to installed torque and the affects that component variables have on this load measurement. Roof control patterns using active cable supports are examined as alternatives for combination patterns using primary and supplemental systems. The importance of maintaining consistent installation procedures plays an important role in the level of performance of the system. Economics comparing the installation of active cables with other primary/supplemental patterns is also included.

Jan 1, 2006

By Michael J. Rinker, P. A. Tibble, M. Wiseman, R. V. Nicholson

Tailings, from an active copper-zinc operation, containing about 10% sulphur were investigated to assess the onset of acid production and potential lime requirements for treatment of drainage. Oxygen consumption rates were measured over two years to verify spatial and seasonal variations in sulphide oxidation rates. Shallow cores were collected to assess the quality of tailings porewater and to characterize solids that had been subjected to oxidation and depletion of neutralization potential (NP) for several years. Oxygen consumption data were used to quantify rates of NP depletion and onset of acid drainage from the near- surface tailings. Based on measured oxygen consumption rates and identification of NP remaining in the tailings, future lime use in the treatment plant was expected to rise significantly without mitigation. Geochemical modeling calculations were calibrated with observed oxygen consumption rates and the model results agreed well with actual lime use in the waste water treatment plant during operations. The modeling also demonstrated the benefits of lower lime demands and treatment costs after closure as a result of construction a soil cover on the acid generating tailings.

Jan 1, 2000

By Huey-Lin Luo, T. R. Anantharaman, William Klement

Two new metastable phases have been obtained in Au-Ge alloys by rapid cooling from the melt. One is of the hep structure with near-ideal axial ratio and may be considered a Hume-Rothery phase. The other has a complex tetragonal structure (a = 11.627Å and c = 22.191Å for the Au60Ge40 alloy) and may be looked upon as a superlattice made up of forty-four fee unit cells. Alloys with the tetragonal phase are charactevized by marked preferred orientation. The metastable constitution of the Au-Ge alloys is discussed with reference to the rate of cooling from the melt. THE Au-Ge equilibrium diagram features a rather deep eutectic near 27 at. pet Ge with a maximum solid solubility of 3.2 at. pet Ge in gold and is similar to the Ag-Ge, Ag-Si, and Au-Si diagrams.' The present study of the effects of rapid cooling from the melt on the structure of Au-Ge alloys constitutes an extension of similar investigations2-8 in this laboratory on alloys of noble metals with germanium and silicon. Nonequilibrium hep structures have so far been obtained by quenching Ag-Ge2, 3 and Ag-Si4, 5 alloys from the melt; an Au-Si alloy of approximately eutectic composition has been found6 to solidify in a noncrystalline state. EXPERIMENTAL PROCEDURES Twenty-nine alloys prepared from gold of 99.9+ pet and germaium of 99.999 + pet purity were investigated. The method of alloy preparation, the technique of rapid quenching from the melt, and the X-ray diffraction procedures were similar to those described previously.3, 4 Essentially, small sections (-20 mg) of thin alloy rods (-1 mm diam) were rapidly heated up to 1200°C in a graphite crucible under argon and the liquid alloy ejected by a helium blast onto a polished copper strip held on the inner periphery of a rotating wheel. The resulting thin foils were examined with or without the copper substrate in a G.E. X-ray Diffractometer or in a 114.6-cm-diam Debye-Scherrer camera. RESULTS Table I gives the constitution of liquid-quenched Au-Ge alloys, as estimated from intensities of X-ray reflections from the corresponding phases, viz., a (fee solid solution), ß (hep phase), ? (tetragonal phase), and diamond-cubic (dc) germanium. Despite unavoidable variations in the quenching rates, the proportions of the phases in different alloys were generally reproducible and stable at room temperature. There was no evidence of quenching strain, since the a doublets were well-resolved in high-angle Debye-Scherrer reflections in all cases except where stacking faults in the a fee and ß hep structures contributed to X-ray line broadening. The ß and ? metastable phases showed signs of decomposition to the equilibrium a phase and germanium only after a few hours annealing above 100°C. A few alloys around the eutectic composi-

Jan 1, 1965

By J. D. Forrester

In striving to develop this discussion about "Manpower for Industrial Mineral Industries" two fundamental classes of manpower are encountered. These are: 1) The Labor Force, comprised of unskilled and semi-skilled, nonprofessional personnel who participate in conducting economic, mineral deposit operations and; 2) The Professional People involved in the science, engineering, and management of such industrial enterprises. The commentary given here will be directed primarily to a review of the characteristics of the second or latter class. To pursue successfully a career as a scientist or engineer in today's industrial and social complex, it is necessary that technical knowledge must have been acquired by training and study in an institution of higher learning. Also, to act effectively, the individual must have achieved some degree of specialzation, although this element often is developed to most notable degree by post-graduate exposure and experience. In addition, and especially in the case of "management," it is desirable, indeed it is even necessary, that an individual recognize and appreciate the fundamental humanistic-sociological controls, and their nuances, as these elements exist to shape his total environment.

Jan 1, 1969

By Jacques Moraille

The public is asking for more aesthetic designs if they can be proven cost-effective at providing an appealing element to new dams. Lake Lenexa was designed and built around the idea of providing for basic dam functions such as flood control, enhanced water quality, recreation but also to provide an inviting community focal point for the residents to visit and enjoy; truly interact with the dam. The architecturally unique dam and ?one of a kind? spillway were designed to symbolize the water cycle as water moves from nature into the urban environment and the back to nature. A pedestrian bridge that spans the spillway offers visitors a good view of cascading pools and a fountain. The original Lake Lenexa dam layout incorporated relatively high, cast-in-place concrete retaining walls to form the spillway structure. The Black & Veatch project team performed a Value Engineering (VE) study to determine cost-effective means for implementing architectural features within the spillway, which resulted in innovative uses of construction materials not typically used in dam and reservoir construction. The VE study concluded that mechanically stabilized earth (MSE) retaining walls that are normally used for transportation projects would be a cost-effective alternative to the originally planned cast-in-place wall systems for the main spillway and stilling basins. The Black & Veatch study added value by mixing cement-kiln dust (CKD) with on-site clay soils to produce a stabilized material for use under the spillway. The CKD stabilized material properties include low compressibility, high strength and low permeability, which reduced seepage and uplift pressures under the spillway slabs. The cost savings provided by the VE alternatives reduced total costs and enabled architectural elements. The award winning dam design also used drilled caissons, expanded polystyrene (EPS) block forms, customized steel forms and external concrete vibrators to build the pedestrian bridge and upper spillway structures.

Jan 1, 2009

By Dennis R. Dolinar

Screen material in the form of welded wire mesh and geogrids are used in underground coal mines to prevent the fall of small pieces of rock from the roof between roof bolts. Further, if the screen is installed during the production cycle, roof fall injuries can be reduced significantly. Therefore, the National Institute for Occupational Safety and Health (NIOSH), because of the safety implications, conducted an evaluation of screen materials commonly used in U.S. coal mines to determine their support characteristics and identify the parameters that could affect their performance with respect to controlling the fall of rock from the roof surface. To evaluate the load and stiffness characteristics of the screen, a test frame was designed and installed in the Mine Roof Simulator (MRS) at the NIOSH Pittsburgh Research Laboratory (PRL). With this test set up, the screen is bolted at four corners of the frame and a center load is applied. The test set up allows for up to 20 in of screen deflection while the load and screen defection are continuously recorded. A series of tests were conducted to evaluate the effects of various parameters such as bolt tension, the type of load bearing surface and the size of bearing plates on welded screen performance. The most common screen material used in U. S. coal mines is an 8-gauge wire welded in a 4-by-4-in spacing or aperture. The peak screen load was normally limited by wire breakage. The conditions at the bearing plate influence the nature of the wire breakage. However, the screen stiffness was controlled by slippage at the bearing plates, and by weld and wire failure. The size of the bearing plate had a significant effect on the performance of the welded screen. Therefore, the design capacity of the 8-gauge screen is evaluated based on plate size. For a 6-by-6-in bearing plate the average peak load is 2,900 lb with a stiffness of 250 lb/in. For an 8-by-8-in bearing plate, the average peak load is 4,500 lb with a stiffness of 430 lb/in. These test results are based on a 4-by-4-ft bolt spacing. A geogrid mesh was also tested.

By Joseph W. Murray

Prior to 1950 Magma's ore production came from two parallel, steeply dipping, east-west striking mineralized faults, one called the Main or Magma vein, and the other the Koerner vein, which lay about 1100 feet to the south, This vein system has been explored and mined over 9000 feet horizontally and 4800 vertically. In 1950 continued exploration led to the discovery and subsequent development of replacement ore bodies in the Devonian limestone zones adjacent to the veins. These replacement deposits occur in the eastern part of the Magma Mine, and follow the strike and the 30" east dip of the host limestone. Strike length of the ore bodies varies from 250 to 500 ft., and thickness from 15 to 125 ft. The ore bodies are large tabular masses with chalcopyrite and bornite being the dominant ore minerals. Hematite and pyrite are the most abundant gangue minerals. Incompetent limestone, shale, or a porphyry sill hanging wall is charactertistic of substantial portions of the replacement beds. In many instances the ore itself is blocky, badly fractured, and intermixed with layers of limestone gouge, pyrite and hematite.

Jan 1, 1973

Fine coal is defined as material with a maximum size of 1/2 in. Various methods for separate washing of such coal are discussed briefly because separate treatment can lead to a higher overall recovery of coal or to a product having a lower ash content.A felspar jig is discussed in detail because it is the method most recently adopted in Australia, and because it has the advantages of compactness, flexibility and automatic Gontrol, with minimum operator attention. This jig has a variety of adjustable controls to enable the desired results to be obtained from a wide range of coals and the general application of each control is discussed.The only separate treatment of fine coal in the Illawarra district is by felspar jigs on Bulli seam coal.INTRODUCTIONAll reasonably large Australian collieries now win coal by mechanical methods. but while mechanization leads to more economic production of high tonnages, it also changes the characteristics of the coal won. In particular there is an increased proportion of fines, and an increased ash and moisture content. However, specifications of coal for sale have become more stringent, and consumers now require coals in a definite size range with a lower and more uniform ash content, as well as with a low and uniform moisturecontent.These factors have led to the need to wash and grade run-of-mine coal at the pithead. In' plants where the whole of the run-of-mine coal is treated in a jig, some of the fine coal in the feed is beneficiated; the extent depending on factors such as the type of coal and the feed rate. However, for dense medium treatment, fine coal must first be screened out, and there may then be no washing of fine coal at all.

Jan 1, 1961

By Masao Suzuki

Over 5 million cars are scrapped yearly in Japan. After dismantling. scrapped automobiles, they are put into a shredder for differential recovery of ferrous and nonferrous metals. The residue, which is called shredder dust, runs over 1.2 million tons per year. This paper reports a entire sequence of scrapping. cars. in Japan with the following sections: (1) production and scrapped car management, (2) material composition, (3) dismantling, (4) shredder plant, (5) differential recovery of metals including specific gravity separation and newly developed color separation.

Jan 1, 1995

The paper re-visits an old and proven concept of winzing, a method widely used in the past to gather exploration data for accurate definition of the orebody. It is proposed to use a mobile Supersucker (a giant vacuum cleaner also known as vacuum lift), to carry out winzing activities underground. A brief description of conventional underground winzing used in the past is provided, together with a discussion on other underground bulk exploration methods used in Australia to date. Historical background, principles of the proposed system, Supersucker construction details and productivities, and benefits and advantages of the proposed system in comparison with other exploration methods, are outlined. Other relevant applications of the mobile Supersucker, including surface winzing, are also briefly discussed in the paper. With a view of using the mobile Supersucker to recover all broken ore stocks underground, included are also results of floor sampling conducted recently in the in-stope decline excavated in a coarse gold type, high-grade orebody.

Jan 1, 2002

By T. M. Broderick

INVESTIGATIONS into the possibilities of economically mining and concentrating low-grade iron ores of the Lake Superior region are attract-ing increasing attention. Among the organizations that are carrying on the work are the United States Bureau of Mines, the State of Minne-sota (which spends about $80,000 annually on problems of the 'iron and ferroalloy ores of Minnesota), and the State of Michigan (which spends about $10,000 annually of its iron-ore research). Several of the mining companies are also financing research. Of the states in the Lake Superior district, Minnesota has done most in iron-ore concentration. In 1930, thirty-seven concentrating plants were in operation on the Mesabi Range, beneficiating about one-third of the total ore shipped. About one-half of these plants reduced silica; the others reduced moisture or improved the structure of the ore.1 Research into the possibilities of magnetic concentration of the Eastern Mesabi magnetite ores indicates that vast tonnages of that ore may be utilized at a profit in the not distant future. Magnetic concentration has also been tried at Sellwood, Ontario, on the Moose Mountain deposit, and at the Berkshire mine in Wisconsin on the magnetic ores of the Western Gogebic Range. There have been few attempts to concentrate Michigan iron ores. In order to determine the possibilities of such concentration, iron-ore research has been carried on at the Michigan College of Mining and Technology for the past few years. After a general survey of the iron ores of the state, a program of more detailed experimentation was out-lined, starting with work on the Ironwood formation of the Gogebic Range. The results of this research led to the belief that gravity methods will produce fairly satisfactory concentrates from the parts of the iron formation that are made up of comparatively thick alternating beds of rather high-grade ore and lean chert.

Jan 1, 1933

By S. Ersayin, I. Iwasaki

The application of a magnetic field was shown to be effective in controlling iron losses in a pilot-scale cationic silica fIotation in the processing of magnetic taconite concentrates. The design of a magnetic field distribution device and batch flotation test results using a 1.42-m3 (50 cu ft) WEMCO flotation cell are reported. Major losses of iron units in froth products were in the -25-µm (-500-mesh) fraction, and the application of a magnetic field decreased the flotation of fine magnetite, thereby improving the selectivity of separation. The "as-received" sample was sufficiently magnetized, and no further benefit was gained by the magnetizing treatment. The selectivity was somewhat adversely affected by demagnetizing the sample, though its effect was minimal due to the magnetic field. The device is simple in construction, low cost and may be readily installed in existing equipment. Key words: Iron ore, Flotation, Taconite concentrates, Cationic silica flotation, Magnetic field, Flexible magnetic sheet, Magnetizing, Demagnetizing

Jan 1, 2003

Amid some of the worst economic conditions that the mining industry has been faced with in more than a decade, the mood among the large crowd at the 114th Annual Northwest Mining Association?s annual meeting was surprisingly upbeat. More than 2,200 attendees showed up at John Asuaga?s Golden Nugget Casino in Reno, NV for the conference held Dec. 1-5. And more than 200 companies exhibited in 240 spaces, including SME and the Minerals Information Institute. The number of attendees and exhibitors were the most for the conference in more than 10 years. The conference was held in Reno/Sparks for just the second time in its illustrious history but began under the cloud of global financial turmoil. Prior to, and during the conference, the industry news headlines were grim, to say the least. An alarming number of mine plans and expansions had been put on hold; hundreds of miners across the United States had been or were in the process of being laid off; commodity prices were falling and some of the biggest mergers in the industry fell through while miners around the world put the brakes on to take a wait-and-see approach. It was a painful time for many, but the downsizing actions taken by many mining companies was exactly what needed to happen, according to Industry Outlook Luncheon featured speaker Frederick Sturm. He is the executive vice president and chief investment strategist and member of Mackenzie?s Investment team. He has earned a reputation as one of Canada?s leading investors in natural-based companies and he also manages the Ivy Global Natural Resource Fund in the United States Sturm said that the mining industry has fallen hard and that he expects it to bounce back quickly, before falling hard again. In these tough times, he said, the companies that have pulled back on production early are doing the right thing in the long run.

Jan 1, 2009

By James A. Schneider

Selection of resistance factors within Load and Resistance Factor Design (LRFD) requires accurate assessment of uncertainty and bias in load and resistance. To date, many studies have focused predominantly on the assessment of uncertainty, while the potential for bias appears to be the dominant factor in design for consistent levels of reliability under a variety of situations. Bias comes from factors which have been ignored in design method development but significantly influence resistance when extrapolating from conditions typical of databases to those at a given site. Uncertainty and bias can be quantified as the coefficient of variation and mean (or median) of a data set, respectively, for statistical assessment of load and resistance factors. This paper first presents an overview of statistical assessment of resistance factors, and then discusses factors that influence uncertainty and bias when extrapolating to situations outside of conventional databases of driven pile axial capacity.

Jan 1, 2009

Jan 1, 1895