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The following methods should be used to protect miners from the adverse health effects of exposure to respirable coal mine dust and respirable crystalline silica: ? Informing workers about hazards ? Establishing written emergency procedures ? Using engineering controls, work practices, and personal protective equipment (including respiratory protection when dust control equipment is being installed, maintained, or repaired) ? Monitoring exposures ? Conducting medical screening and surveillance ? Encouraging smoking cessation ? Maintaining medical records

Jan 1, 1997

By Fred N. Kissell

Tracer gas decay curves were experimentally obtained in a full-scale model coal mine working face area. The concentration of tracer gas was found to decay in exponential fashion but with a change in slope. This change in slope is attributed to eddy zones in the face area. A simple theory was developed that allows one to calculate the approximate amount of gas in the eddy zones and thus estimate the size of the eddy zones.

Jan 1, 1974

By Jami M. Girard, Ed Mchugh

Slope stability accidents are one of the leading causes of fatalities at U.S. surface mining operations. The Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is currently conducting research to reduce the fatalities associated with slope failures. The purpose of this paper to discuss some of this research and to present potential new technologies for slope monitoring and design. The paper also briefly discusses various warning signs of slope instability, introduces the most common slope monitoring methods, describes the limitations of various slope monitoring systems, and presents some field results using some of this new technology.

By Robert King

Splicing portable trailing cables used in underground coal mines is usually less expensive in terms of capital outlay and production time lost than replacing them. However, handling trailing cables may result in electrical arcs, shocks , and burns. Also, destructive forces encountered during a mining operation may shorten the effective life of a cable splice. This report gives the results of an analysis of cable splice defects in an effort to establish cable splice performance criteria, determine testing standards for cable splices, establish guidelines for training programs in cable splicing, and indicate areas for improvement.

Jan 1, 1975

By L. C. Headley

Surface areas of two synthetic and three natural consolidated porous samples were obtained by the Orr low-pressure permeametry technique. The results suggest that the Orr technique is a useful substitute for the low-temperature gas adsorption (BET) method for determining the surface area of rock samples. It was more rapid than the BET method, and the surface-area values obtained were larger but agreed better with BET values than values calculated from the Kozeny-Carman equation. Efforts were unsuccessful to demonstrate the influence of channel-size distribution on pressure-flow rate curves by means of experimental data and a parallel channel model.

Jan 1, 1971

By C. L. Karr

The U.S. Bureau of Mines is currently investigating the use of genetic algorithms (GA's) for solving optimization problems. This computer search technique, based on the mechanics of natural genetics, was used to perform simple least squares curve fitting. Three examples are presented in which a GA manipulates binary coded strings to produce near-optimal solutions to least squares curve-fitting problems after having viewed only a small portion of the search space. The examples include fitting data to the equation of a line, the equation of a parabola, and the Ree-Eyring equation.

Jan 1, 1991

By A. L. Engel

This report describes laboratory-scale experimental treatment of six base-metal ore samples taken by engineers of the Bureau of Mines, Region II, while investigating ore deposits in California and Nevada. The information is of interest in developing the mining districts represented or when similar ores from other sources are being studied. Simple treatment methods were employed as far as possible. More complex treatments also were tried when necessary. The possibilities and limitations of the methods applied to the several ores are shown by the data herein reported.

Jan 1, 1960

By Thomas E. Marshall, Patrick A. Kinek, Gerald L. Finfinger

The purpose of this investigation was to evaluate the integrity of the existing shutoff valves and actuators used under high-temperature conditions in the Bureau of Mines' horizontal borehole methane drainage pipe- line system and to determine the potential for improvement in the system. In the field tests, both fire-safe ball valves and standard brass ball valves were initially subjected to a 30-min pan fire without thermal protection. Neither valve could maintain line pressure beyond 11 min in a fire that reached temperatures between 500° and 700° C. Based on the test results, it was concluded that the brass ball valve used in the Bureau's methane drainage pipeline system can be retrofitted with an inexpensive "fire bag" to substantially increase its integrity under mine fire conditions.

Jan 1, 1986

A survey of roof and pillar conditions in underground limestone mines in the United States has revealed that bench mining of the floor between pillars can cause instability in the pillars at the perimeter of the benched area. Increased loading of these pillars was observed at several mines. Large inclined geological structures that are exposed in pillar ribs were observed to contribute to pillar instability. The paper describes a study that was carried out using numerical models to assess the effects of bench mining on pillar load and stability. It was found that the benched pillars shed load onto the surrounding pillars owing to their reduced stiffness. The pillars at the perimeter of the benching area will start shedding load as soon as benching increases the height of one side of the pillar. A case study is described which shows the effects of bench mining on limestone mine pillars.

Jan 1, 2007

By J. E. Meacham

The U.S. Bureau of Mines investigated recovery of manganese from basic oxygen furnace (BOF) steelmaking slags because the slags represent a large potential resource of a metal for which there is no domestic production. BOF slags were leached using fluosilicic acid, a byproduct of the fertilizer industry. Manganese and iron were extracted as soluble manganous and ferrous fluosilicates while the calcium and magnesium remained in the tailings as insoluble fluorides. Treating the pregnant liquor with sodium chloride, precipitated sodium fluosilicate (Na2Sif6) which was recovered as a byproduct. Manganese and iron were precipitated as hydroxide-carbonate salts with the addition of sodium carbonate to the treated liquor. Recoveries for manganese and iron were 73 to 83 and 67 to 70 pet, respectively.

Jan 1, 1991

By Lloyd A. Morley

To reduce safety and production problems, it is essential that the electrical operating characteristics of coal mining equipment and their electrical subsystems be clearly understood. The Bureau of Mines and the Pennsylvania State University have developed techniques to monitor and analyze several of the critical parameters. A unique system for measuring traction locomotive consumption at the machine has been assembled and utilized. Conclusions from 27 continuous miners show that voltage levels are directly tied to machine efficiency. The Bureau of Mines and Pennsylvania State University, along with West Virginia University, are currently monitoring and accessing mine power transients. Results exhibit that voltage transients of three to five times the line -to-line value are common on underground distribution systems.

Jan 1, 1975

By E. K. Stanek, P. Kantabutra, R. A. Wolf

This paper summarizes the cause and effect of induced voltages in multiple conductor cables supplying alternating current power to equipment in under- ground coal mines. The investigation of this phenomenon revealed that the electrical energy produced by the resultant electric arcing between the frames of mobile electric face equipment was of a sufficient magnitude to ignite explosive methane-air mixtures. The results of laboratory tests and field tests made between equipment frames during actual operation in numerous coal mines are discussed. Several methods of eliminating or suppressing the induced voltages to nonincendive levels are also described. It is the purpose of this paper to convey to the mining industry a knowledge of this problem and to recommend methods of eliminating or reducing these induced voltages or arcing currents to safe levels.

Jan 1, 1975

By R. V. Ramani, P. M. T. White, D. Sutton

3.1 Criteria for Selection A coal deposit has the following major characteristics: i) wide distribution as a flat-lying, thin, bedded deposit ii) stable nature of its major components and ranking characteristics such as carbon, heat content, volatile components, specific gravity, etc. iii) number of constituents and characteristics which under present regulations limit usage, such as content of ash, sulphur, sodium, etc. iv) effect of characteristics of over- and under- lying host rocks including porosity and permeability, lithology and general geology v) low value, high bulk nature. Because of the relative stability of its major components and its low unit price, coal does not require the same attention to detail as do the metal deposits. However, new regulations combined with social pressures make it imperative that more accurate information be made available concerning factors which affect the quality of coal and which may have an adverse effect on the environment when the coal is mined or burnt. The method selected for the evaluation of a coal deposit must, therefore, be flexible and sensitive enough to be used to interpolate stable parameters whose general distribution character-

Jan 1, 1974

By J. K. Whyatt, B. G. White

Various methods of monitoring slip movements on bedding planes, as well as examination of rock burst damage in stopes, suggest that many rock bursts in the Lucky Friday Mine are closely associated with these movements. Slip displacements along bedding simultaneously reduce the physical dimensions of stopes and increase compressive stress along stope margins. Such changes, in turn, contribute directly to sudden failures of rock and cemented sandfill surrounding stopes. We believe that the reduction of rock burst hazards must be based on a clear understanding of the basic mechanisms involved. The current work emphasizes the mechanical role of wall rock movement and seismicity in generating conditions that promote rock burst damage. Based on our interpretations of these mechanisms, we briefly address several hypothetical practices that could influence rock burst hazards in similar mining situations. The overall goal of this research is to advance the NIOSH mission of improving the health and safety of the nation’s workers.

By Donald P. Tuchman, Robert P. Vinson, Linda J. McWilliams, Steven E. Mischler, Jon C. Volkwein

A personal dust monitor (PDM) was developed to measure respirable coal mine dust mass to provide accurate exposure data at the end of a work shift. Additionally, the new monitor continuously displays near-real-time dust exposure data during the shift. The PDM uses a tapered-element oscillating microbalance to measure the mass of dust deposited on a filter and continually displays the cumulative exposure concentration data. The accuracy and precision of the instrument was determined by comparison to gravimetric filter samplers in the laboratory and in four mines. Laboratory results with different coal types and size distributions showed that there is a 95% confidence that the individual PDM measurements were within ±25% of the reference measurements. Mine test results indicate that data taken with adjacent PDM and reference samplers are indistinguishable. The technology proved durable enough to successfully measure 108 shifts of data out of 115 attempts in the mines. Under these specific test conditions, the PDM demonstrated that it was convenient to wear, robust, provided accurate data, provided timely data that could be used to prevent overexposure, and was easy to use.

Jan 1, 2004

By Jack C. White

Studies were made to determine the character and distribution of the copper lost in copper mill tailings. Acid soluble (oxide) and acid insoluble (sulfide) copper were determined for heavy-liquid sink and float products of screen-sized fractions from 12 copper mill tailings. In most of the tailings studied, the coarse-size fractions are higher in copper grade than the respective bulk tailings, high in sulfide copper, and low in oxide copper. Oxide copper occurs predominantly in the minus 325-mesh "slimes." Microscopic examination of heavy-liquid sink products indicated that recovery of liberated copper sulfide minerals is complete in most mills, and that copper minerals not being recovered are locked with gangue particles. Additional copper could probably be recovered from most tailings by size classification, scavenger froth flotation of the coarse fraction, and regrinding of the concentrate to achieve liberation of the locked sulfides.

Jan 1, 1971

By A. W. Effinger

The Bureau of Mines used regression analysis and applied statistical methods in an effort to rationalize the results of an experiment examining the effects of certain variables on carbon deposition in a reservoir for thermal recovery of petroleum. Although none of the 15 trials of the original experiment resulted in the response of weight-percent of carbon regarded by the experimenter as adequate, values calculated using canonical analysis in two trials yielded responses 33 and 54 percent higher than the minimum acceptable figure. The actual responses differed by less than 3 and 6 percent, respectively, from the predicted responses. Methods are described for defining a path of increasing response based on the minimum point and the response surfaces and for defining a set of values for the parameters in question, which result in increased response, A detailed explanation of the mathematical process used in this analysis is presented in the appendix for ease in computer programing the technique.

Jan 1, 1970

By C. M. McCulloch

Examination of several coalbeds in Walker County, Ala., Cambria, Greene, and Fayette Counties, Pa., and Raleigh and Wyoming Counties, W. Va., indicates that cleat orientations are similar throughout a vertical sequence of strata. Studies of cleat orientation were carried out in underground mines that are operating in separate coalbeds vertically above one another. The data show that over a vertical separation of 100 to 400 feet, the average difference in coal cleat orientation between mines is 04° for the face and 08° for the butt cleat. Variations of coal cleat direction between coalbeds examined in strip-mined areas show similar values. Cleat orientations measured at outcrops agree well with the directions measured underground, suggesting that the amount of vertical separation between coalbeds has little effect on the resulting differences in cleat directions. The largest variation of cleat directions between adjacent coalbeds occurs where a large horizontal distance separates two sample locations. Cleat orientations for deeper coalbeds are most reliable where the data are taken from directly above.

Jan 1, 1976

By L. W. Brandt

As part of its objective to expand the body of mineral information as a basis for new technology, the Bureau of Mines conducted research on the fundamental behavior exhibited by phosphate clay waste in settling ponds. A semiempirical equation used to describe the compaction of ceramic powders in a single-acting die was applied to aqueous phosphatic clay waste and attapulgite slurries. This equation, [*V = a1 e ?k1/P + a2e ? k2/P] was found to describe the compaction of an attapulgite gel and a phosphate slime gel by a moving screen. [*V] is the ratio of the compaction achieved at a given pressure, P, to the compaction achieved at a pres-sure sufficient to remove all space between particles. The constant al represents the fraction of compaction achieved at low pressure by rearrangement of floes to higher packing density, and a2 represents the fraction of compaction achieved at higher pressure resulting from removal of voids within floes. K1 and K2 are constants determined from the experimental data. Both the low-pressure and high-pressure compaction mechanisms were observed in the compaction of the clays. These two compaction mechanisms offer an explanation for the observation that impounded slimes initially dewater rapidly and then dewater at a much slower rate.

Jan 1, 1982

By Robert F. Chaiken

A novel approach to eliminating environmental and public safety hazards that are associated with fires in abandoned coal mines and waste banks involves the use of in situ combustion technology developed by the Federal Bureau of Mines to accelerate the burning of the wasted coals in place. This technology would be used under exhaust ventilation control conditions that would allow for total management of the hot gases produced. Combustion stoichiometries would be optimized to minimize unburnt combustibles and to maximize the heat content of the gas products, which will be exhausted at one or more fan locations. When necessary, scrubber systems would be employed to remove air pollutants, such as sulfur dioxide; heat utilization systems (process heat, steam, and electricity) would also be employed to offset operational costs. Ultimately, complete burnout would solve the fire and acid water formation problems of the abandoned coal mine or waste bank. Pertinent technical data for burnout control are derived and discussed in terms of the important material and operational parameters. In general, it is believed feasible to operate a burnout system in an existing abandoned mine or waste bank fire at thermal power levels in the range of 10 to 100 Mw, and at exhaust gas temperatures of 1,000° C (1,830° F).

Jan 1, 1980