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By Fred N. Kissell, Jerry C. J. Tien, Edward D. Thimons

At coal mine working faces, simultaneous application of three basic elements reduces the methane explosion hazard: (1) adequate ventilation, (2) regular monitoring of gas concentrations, and (3) the elimination of ignition sources. This paper reviews the application of these elements in a manner relevant to Chinese coal mines. Adequate ventilation is provided by using the mine entries to convey air for the long distances between the mine portal and the working sections (main ventilation systems) and then using line brattice or ventilation duct (face ventilation systems) to convey air the last hundred meters to the working face where coal is broken and removed. The air quantity provided is enough to safely dilute methane and the air velocity is enough to prevent layering. Gas concentrations are regularly monitored in accordance with regulations using knowledge of the circumstances under which the highest concentrations are likely to be found. Ignition sources are eliminated by ensuring that electrical equipment does not ignite methane, that sparking from cutter picks is minimized, and that smoking by workers is strictly forbidden. Risk-reduction studies using fault-tree analysis have shown that large reductions in explosion risk only result from multiple preventive actions. For example, a ventilation upgrade or a methane monitor upgrade by itself offers risk reductions under 50 pct. A risk reduction of 90 pct. or more would typically require much more. Other studies have shown that the everyday vigilance of those working underground is as important as engineering design.

By T. Bajpayee, L. Prosser, A. Iannacchione

Reducing the number of roof fall injuries is a goal of the NIOSH mine safety research program. Central to this effort is the development of assessment techniques that will help to identify the nature of the risks associated with working under potentially hazardous roof conditions. This paper discusses a method to determine the roof fall risk using a qualitative risk analysis technique. The ability to determine roof fall risk has been a long-standing goal of safety professionals and can provide the kind of information, needed by on-site personnel responsible for worker safety, to mitigate roof fall injuries.

Jan 1, 2007

Methods for Improving the Flotation Recovery of the Coarse Fraction of a Nickel Ore

Sep 13, 2010

By N. Cruickshank

Gas outbursts occur as sudden eruptions of gas and minerals from the face of a mine heading as the heading approaches potentially burst-prone (or anomalous) zones of rock. Such outbursts have resulted in considerable damage to equipment and in some cases lives have been lost. Characterizing these anomalous zones and detecting their presence is therefore vital to safe mining. Certain significant characteristics associated with the outburst-prone zones are: (1) the presence of fluid inclusions, (2) unstable stress conditions, (3) characteristic geologic structures, (4) certain physical properties of the rock, and (5) micro-seismic activity. Geophysical and engineering methods for detecting these characterisitcs are discussed and are considered with respect to their past success and future potential for predicting gas outbursts.

Jan 1, 1985

By J. Janin, J. F. Bougard

Development of improved transportation networks in major urban centers has led more and more to underground construction, the only reasonable solution for decreasing surface traffic congestion. Excavations required by these projects usually cause decompression of the surrounding soil mass which results in subsidence of several centimeters. While these magnitudes of subsidence have no consequences in undeveloped areas, they are often unacceptable in urban areas where existing buildings, structures and utilities are endangered. Recent tunneling projects for the extension of the Paris Metropolitan Transit System (R.A.T.P.) underground network were carried out with this in view and gave rise to the development of a number of innovative techniques for minimizing ground decompression and subsidence. As shown in Figure 1, the recent R.A.T.P. expansion program includes a new express metro, 46 km long, crossing Paris from East to West, and the extension of many existing metro lines in the suburbs. From the start, R.A.T.P. was faced with many unique technical problems for which there was little precedent experience. The structures to be built have large dimensions, with cross-sections typically ranging from 40 to 300 m2, and exceptionally to 600 m2. The new lines are often very deep because the shallow profile is already congested by the existing metro, interceptors, sewers and a very large number of utilities. As a result, new construction is often below ground water level by as much as 20 m. Moreover, the geology varies widely from hard limestone with compressive strength over 1500 kg/cm2 to inconsistent water bearing sand. Finally, curves in the East-West line must have a minimum radius of 500 m which frequently forces the alignment to pass below existing structures, buildings and monuments.

Jan 1, 1974

By L. R. Moore

Arsenic is among the list of major contaminants in mining aqueous waste streams. Though the elemental form is toxic, the aqueous oxyanions are more so. The most common forms of arsenic released during mining processes are arsenate and arsenite. The common treatment technologies to date can be summed up in these major categories: oxidation, coagulation, absorption, and media filtration. These methods can often involve many expensive processing steps that may also be limited by variables, such as total dissolved solids, other cations and anions, and the oxidation state of the arsenic. An innovative technology, falling in the absorption category, was developed that can successfully reduce such aqueous forms to a level below the EPA recommendations. This new technology offers a unique and viable solution which is transparent to the above mentioned limitations.

Jan 1, 2012

By R. Strydom, J. H. Selby

Published information is available on the radiological impacts of disposing of zircon sand in a landfill. Zircon flour by virtue of its finer particle size presents a different set of issues during disposal. This paper describes two options for disposal of such fine grained materials – namely incorporation into concrete aggregates and agglomeration by addition of cement. The study considers the radiological exposure of the public from such disposal methods and concludes that these options are viable alternatives for the safe disposal of waste zircon flour. The disposal of zircon into concrete aggregates at a rate of 10 per cent produces a sufficiently low effect to allow such aggregates to be used in building foundations or other such mass concrete applications. The use of cement agglomeration methods will also provide a safe method of landfill disposal provided at least 20 cm of soil cover is included.

Jan 1, 2003

THIS bulletin presents all analytical and lest methods regularly used by Bureau of Mines laboratories for characterizing coal and coke. To provide better service to coal producers and consumers, the scope of this bulletin has been expanded to include important test methods used to evaluate coal properties for commercial processing. The methods described will prove valuable to all persons interested in analyzing and testing coal and coke.

Jan 1, 1967

By A. C. Fieldner

THE Bureau of Mines has received many requests for Information concerning the methods its laboratories use for analyzing coal and coke and determining their heating value. The fuel investigations now conducted by the Bureau of Mines are an outgrowth of the work undertaken at the Government coal-testing plant erected in 1904 at the Louisiana Purchase Exposition in St. Louis, and the methods for proximate and ultimate analysis of coal used by the Bureau of Mines are based on those originally adopted by the chemists of the coal-testing plant and followed in the subsequent chemical work of the Government fuel-testing plants at St. Louis, Mo., Norfolk, Va., and Pittsburgh, Pa. The many valuable suggestions and criticisms received from N. W. Lord, director of the School of Mines, and from E. E. Somermeier, professor of metallurgy, of Ohio State University, at that time, are greatly appreciated; development of many of the methods for the proximate and ultimate analysis of coal now used by the Bureau of Mines is chiefly clue to these men.

Jan 1, 1951

By John S. Johnson

THE purpose of this article is to describe several types of borehole lining in common use, and especially to offer a relatively new means of reducing the expense of maintaining boreholes where they are subjected to corrosive action of water flowing either inside or outside of their casing. In the Anthracite region of Pennsylvania, boreholes are used for many purposes, the principal ones being: openings between the surface and underground workings through which are passed steam, water and compressed-air lines, ropeways from surface hoists to underground rope haulages, conduits for electric power and signal lines, water-discharge lines from underground pumping stations, and inlets to mine workings for flushing material. LININGS FOR BOREHOLES The inadequacy of steel pipe for use in boreholes has long been recognized. Various substitute materials have been tried, including screw-joint cast-iron pipe (Fig. I). Cast-iron pipe, while very effective as a discharge line for acid water (mine water) being pumped to the surface, is not so effective when serving as a conduit for silt and crushed rock being flushed underground for filling mine voids. Terra cotta pipe (Fig. 2) has been used in boreholes, and lasts a long time if the glazed inner surface of the pipe remains intact. Its installation in a borehole is very difficult and is recommended only where it is certain that there will be no subsidence of the surrounding territory. Accessibility in order properly to join each section of the pipe is essential to a satisfactory job. In large water holes, where it is possible to lower a man into the hole for sealing the joints of the pipe, glazed terra cotta pipe has been used successfully for delivering mine water from pumps in the mines. For large holes used for flushing refuse into mine workings where the surface wash is shallow, standard paving brick have been used to form a tube through the wash to the bedrock. These brick are laid radially, backed by common brick and cobbles laid in cement. It is obvious that the shaft through the wash must be large enough to permit a man to work in it. The flushing material is carried through bare rock from the juncture at bedrock to the openings underground. This plan has been used, particularly where a cast-iron surface line is laid upon the surface to carry the flushing material from the breaker to the hole, and down the hole continuously, with no opening to the air at the top of the hole, thereby eliminating the necessity of an attendant at this point (Fig. 3). Another similar type of borehole lining is constructed of hexagonal pieces of vitrified brick (Fig. 4). This type requires a steel drive pipe through the surface wash large enough to provide a finished tube of the desired size surrounded by a brick wall about 4 in. thick. The special bricks are laid in cement, six to a circle, around a lubricated pipe used as a form, and lowered in sections inside the large drive pipe; the bottom section is seated in a socket drilled in the solid rock, having the same inside

Jan 1, 1941

By N. C. Matheson

The West's Shell Pile has been used on sites with very soft ground conditions for over 60 years. Fibre reinforced precast concrete shells 900mm long are threadled onto an internal mandrel which can be extended according to the depth driven to attain the load bearing resistance. On completion of driving the mandrel is removed leaving the precast shells to form a permanent lining to the cast insitu concrete core. To give resistance to high contamination, a tar based epoxy coat is sprayed on the outside of the shells or a flexible PVC liner is installed inside the shells to protect the core. Fundamental to the resistance to contamination is the quality of the precast fibre reinforced concrete shell, the mix design and method of manufacture. A series of detailed laboratory experiments were carried out using samples immersed in concentrated acid and sulphate solution. The long term effects of exposure to contamination is recorded in the case studies of existing piles at two gasworks sites.

Jan 1, 1989

By Claude Cunningham

The primary reason for blasting is to fragment rock. In production blasting, the fragment sizes produced are known to exercise an overwhelming influence over working costs: handling costs and tonnage throughput are directly affected by secondary breaking, loading and crushing, all functions of fragmentation. In addition, particular size fractions are frequently of intense interest in terms of market or process requirements.

Jan 1, 1995

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 Johannes Moeljono, Werner Wenzel, Heinrich Wilhelm Gudenhau

As an important mechanism for increasing production of the suction-draft-sinter process, it has been shown that gas permeability through the sinter layer plays an important role. Methods to increase production rates have been indicated and suggestions for carrying out the process have been made to improve the rate of production, reduce the fuel consumption, and at the same time obtain a uniform sinter. Laboratory experiments were conducted at the Institute for Ferrous Metallurgy of the Technical University at Aachen to illustrate these methods. Methods of Increasing Gas Penetration Through Sinter Layers The following are of fundamental importance in determining the process cycle during the sintering of iron ores: 1) Generation of maximum temperature, since its form and range determine sinter quality. 2) Propagation velocity of the temperature maximum which controls the attainable output. 3) The convective heat transfer which influences the velocity of travel of the temperature maximum.

Jan 1, 1974

By Thomas CG, Armstrong GJ, Lynch KS

A small glass walled pot grate has been used to simulate drying of iron ore pellets in a travelling grate plant. This equipment has enabled the effect of decreasing grind and de- creasing pellet bulk density on plant production to be quantitatively predicted. These predic- tions are compared with plant experience. The use of the laboratory simulator in comparing the effect of various additives on plant production is also described and substantial improvements in both the goethite and free-water drying periods are predicted.

Jan 1, 1972

By T. H. Aldrich

THE Aldrich Mining Co. holds under lease from the Illinois Central R. R. Co. about 14,000 acres, in the East half of Township 12, Range 12 `V., in Marion county, Alabama, and owns other lands, of which about 1,000 acres adjoin this leased tract, making a total area of about 15,000 acres, all of which is underlain by the coal-seam upon which the company is operating. This seam is nearly horizontal ; and a ravine, diagonally crossing the tract, exposes the outcrop on either side for about 2 miles. The territory has been so divided that nearly the whole of it can be worked out by two collieries. The mines at Brilliant were opened in the Fall of 1898, and shipments began in the following spring. The original plan was to furnish steam-coal for locomotives to the Illinois Central R. R. Co.; and upon this expectation the investment of capital was made. The field was entirely new; and the softness of the coal at the outcrop induced the belief that it could be very cheaply mined. A contract for the delivery of a large quantity of coal to the railroad was accordingly executed. But with the advance of the entries to increasing distances from the outcrop, the coal proved so hard that it could no longer be drilled with a breast-auger; and the expense of mining became so great that the contract for cheap steam-coal had to be cancelled. It became evident that the work must be done with machinery and explosives, if it could be profitably done at all. On the other hand, the excellent quality of this coal opened, at the same time, a possible market not specially contemplated at the outset-namely, that of a first-rate coal for domestic and general uses. Since no other deposit of such coal was known to exist on the line of the Illinois Central, or any other railroad

Jul 1, 1906

By D. Y. Geng, Syd S. Peng

This paper analyzes the effects of geology and mining methods on surface subsidence factor, angle of draw and angle of critical deformation based on the results of 40 longwall subsidence profiles in the Northern Appalachian coalfield. Several equations were derived to show the relationships between those parameters. Furthermore, the equations were transferred and plotted in the form of several monographs for convenience of applications.

Jan 1, 1982

By C Ross

This paper uses the results of research trials by Landcare Research and Forest Research Institute and assessments of reclamation plantings at mines and other drastically disturbed sites to describe methods of enhancing restoration of native forests. The characteristics of mine and forest environments are compared to highlight the difficulties facing restoration and techniques which result in successful restoration are described. Selection of the most appropriate technique is illustrated by describing restoration of lowland beech-podocarp forest at a West Coast coal mine. The key to successful reclamation is to understand the factors controlling and limiting plant establishment and growth, then to design rooting media, surfaces and management regimes to create a favourable environment. This paper concludes with a summary of the planning and technical factors which are critical for successful restoration of native forest.

Jan 1, 1995

By George H. C. Norman

A NUMBER of methods have been developed for the determination of the dust concentration in air, some of which have been reported as very efficient and for research may be more satisfactory than the method about to be described. In practical mine use, however, the accurate research equipment is unwieldy and requires a high degree of technical skill to manipulate it. Also, it gives less general practical information to the operator in the same length of time than the method described here. Moreover, it is doubtful whether at the present stage of affairs the results obtained from the precise methods have any more practical significance than those obtained with simpler and more portable apparatus, which can rapidly give a sufficiently reliable indication of the relative dust hazard. HISTORY OF DUST DETERMINATION IN ONTARIO The first record of mine-dust determination in Ontario is given in an article by Dr. J. H. Elliott,' in which he records a few dust counts made with the Palmer spray apparatus. There were insufficient data from which to draw any definite conclusions or reasonably compare with present-day counts using the konimeter. The first konimeter dust sampling was started in the Porcupine district in 1926, using light-field counting without adhesive and with no sample treatment before counting. A method of semidark-field counting was used from about 1928 to 1931 and dark-field illumination was adopted permanently about December 1931. The konimeter has been continued as the principal means of dust sampling in the mines of Ontario, where South African practice has been adopted because in South Africa most careful study has been given the problem of silicosis, and very complete records of work done there are

Jan 1, 1937

Various steps, and complete sequences, for the recovery of lead and zinc from a mixed sulphide concentrate, high in silica and pyrite, have been tested.Oxidation steps of roasting in air or in a sulphating atmosphere and use of aqueous acidic, ammoniacal, and near neutral oxidation media were compared. Oxidation roasting or use of acidic media appeared most useful. Procedures for dissolution of zinc from calcines using sulphuric and sulphurous acid to avoid silica gelation problems are compared and a direct leaching procedure with sulphuric 'acid at controlled pH shown to be the most useful.Methods for the removal of germanium, nickel, and magnesium from zinc sulphate solutions prior to zinc electrodeposition were tested. The recoveries of zinc from ammoniacal solutions by electrolysis and distillation are compared.The dissolution of lead compounds from the residue of zinc extraction by amine and ammoniacal ammonium sulphate (AAS) solutions Was tested. Lead, sulphide was precipitated in filtera'ble form from AAS solutions. The reduction of lead sulphate to lead sulphide with sulphur was difficult, but possible. The various steps were used to deveiop five complete processing sequences, of which two were shown to be technically feasible and have potential economic viability.

Jan 1, 1975