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By Peter Swanson

One of the primary methods for analyzing roof stability in underground mines is the age-old method of “roof sounding” where a miner taps on the roof and listens for the hollow sound of loose blocks of rock. This paper looks at the feasibility of using noncontact laser-based vibration measurements to detect roof fall hazards with the ultimate vision of improving, expanding and automating procedures for mine roof inspection. Vibration measurements made on loose blocks of rock in underground mines are summarized and compared to estimates of fundamental resonance frequencies for rock slabs of the size responsible for highly hazardous “skin failures.” Both laser Doppler vibrometry and full-field interferometric methods are examined and are considered to be feasible methods for detecting anomalous vibrations in loose roof rocks. Results from simple laboratory experiments using laser vibrometry demonstrate some of the proposed application concepts. While considered a challenge to move these techniques from the laboratory to heavy industrial or outdoor environments, the potential for success in the current application is enhanced by the reduced requirements of qualitative analyses.

By H. E. Powell

The magnetic susceptibilities of 57 minerals containing titanium, zirconium, vanadium, columbium, tantalum, chromium, molybdenum, and tungsten were determined. The source and petrographic analysis of each sample are given. Included are values for isomorphous series of minerals showing wide ranges of composition and for a few high-purity synthetic minerals.

Jan 1, 1968

An examination of the Census of Fatal Occupational Injuries (CFOI) data for the period 1992-1995 shows that 659 fatalities occurred in the mining industry as defined by the SIC. Oil and gas accounted for slightly more than one-half of all fatalities (figure 1-1). The coal industry had the highest fatality rate for the 4-year period, with 35.6 deaths per 100,000 full-time workers, followed by metal (23.1 per 100,000), oil and gas (23.1 per 100,000), and nonmetal (20.1 per 100,000). The fatality rate for all U. S. industries during this same period was 5.1 per 100,000 full-time workers. Figure 1-2 compares the fatal injury rates by year for the four major industry sectors of mining to the fatality rate for all industries combined. Figure 1-3 compares age-specific fatality rates in the mining industry to those seen for U. S. industry as a whole. Fatality rates for all industries combined were lowest for young workers and steadily increased in relation to workers' ages. In the mining industry, fatality rates by age group show a U-shaped curve. Young workers under 20 years of age had the highest injury rate (54.6 per 100,000), followed by workers aged 20-24 (50.8 per 100,000) and workers over age 65 (37.7 per 100,000). Table 1-1 shows the distribution of injuries by type of injury event. The mining industry, in comparison with all industries, had a considerably larger proportion of fatalities classified as caught in or crushed by collapsing materials (9.1% and 1.9%, respectively) and fires and explosions (10.0% and 3.1%, respectively). Transportation events comprised the largest proportion of fatal injuries in both the mining industry and all industries. Within the mining industry only, transportation accounted for the largest proportion of fatalities in all mining sectors except coal. A more detailed examination of the transportation events within the mining industry showed that highway incidents (50.5%) were the most common, followed by nonhighway incidents (22.2%), pedestrian incidents (10.6%), and those incurred during rail, water, and air transport (15.7%). Incidents involving caught in or crushed by collapsing materials comprised a higher percentage of injuries in the coal and metal sectors, while fall-from-height incidents were more frequent in the oil and gas sector. The classification system used in CFOI for type of injury event is not compatible with any variables contained in the MSHA data; therefore, direct comparisons are not attempted. [ ]

Jan 5, 2000

By E. D. Gardner

"Trolley lines used in connection with electric haulage in mines are a source of danger and many lives have been lost by men accidentally coming in contact with the wires. Usually the wires in metal mines are sufficiently guarded to prevent men from touching them with their person or by pieces of steel which they may be carrying or their shoulders, while walking along the level. However, it is difficult to guard effectively the wires at loading chutes along the haulage ways and in spite of safe guards, chute tappers have been electrocuted through loading bars accidentally touching the trolley line.To overcome this danger the Calumet & Arizona Mining Co., at Lowell, Arizona formely used a hinged V-shaped trough made of 1-inch by 6-inch lumber, that was dropped over the wire in front of the chute, when the cars were being loaded. This arrangement interfered with the easy operation of the chute, and a cut-out device for the trolley line was devised by W. R. Gibson, chief electrician for the company. This cut-out is efficient easily constructed and roes not interfere with the operations at the chutes or with the motors operating on the same level.When the cut-out is open the electric current is carried past the gap by an insulated wire on the opposite side of the drift. A hinged board drops down over the ends of the trolley guard when the slide is open and Prevents anything touching the live wires. About ninety of these cut-outs are now in use in the mine,The levels under the scopes are timbered with drift sets placed 5 feet apart, and the loading chutes take up the space between two sets. All trolley wires in. the company's mines are carried 6 feet above the rails and guarded by two 1/2 by 6-inch boards placed on either side of the wire."

May 1, 1921

By S. J. Pearce

The need for a simple, very sensitive, and accurate method for the determination of benzene in blood and urine was evident throughout a recent study of chronic benzene (C6H6) poisoning conducted cooperatively by the United States Bureau of Mines, The Barrett Company, and the producers of benzene. A combustion method which will be described in a later publication, end a previously described5/ adaptation of Smyth's method were developed and used during that investigation. The adaptation of Smyth's method gave satisfactory results when dealing with exposure conditions that produced chronic poisoning in a comparatively few days, but it was time-consuming and lacked the accuracy necessary for a study of the absorption, distribution, and fate of benzene in the body during exposure to threshold concentrations of benzene vapor in air. The combustion procedure was satisfactory from the standpoint of sensitivity but was cumbersome, intricate, time-consuming, and required the use of special and somewhat expensive physical and. chemical apparatus. Following the termination of this study of chronic poisoning, possibilities for developing better methods occurred, and these have been investigated by the Bureau of Mines with the aid of Relief Works Division personnel. A microcolorimetric method for the determination of benzene in air has been described recently.6/ The present report deals with the adaptation of this new colorimetric method to the determination

Jan 1, 1936

By J. E. Chilton, T. Mal

Methane monitoring at the mine face is essential to assure a safe work environment in underground coal mines. Machine-mounted methane monitors must be used to continuously monitor methane levels during mining. Monitors used on mining machines must be approved by MSHA and properly maintained to provide protection for workers (30 CFR 75.342). To provide protection the instrument must give accurate readings of current methane levels. Accuracy is maintained by calibrating the instrument with a standard gas at least once every 31 days. Instrument “response time” determines how quickly measurements will change to reflect current concentrations. At present there are no criteria for measuring the response time for a ma-chine-mounted methane monitor while underground. This study examined a procedure for measuring the response time of a machine-mounted methane monitor. Response times were measured using methanometers obtained from three different manufacturers. The effects of the measurement technique and methanometer sensor head design on response time measurements are investigated. Techniques for reducing variation in response time measurements are discussed.

By G. R. Strimbeck

This is a report on experimental work on development of a gasification process operating at near atmospheric pressures and using finely pulverized coal entrained in oxygen and steam. The gasifier was designed by The Babcock and Wilcox Co. in cooperation with engineers of the Bureau of Mines Morgantown station. The test work discussed in this report covers the first 34 tests made in the pilot plant in which a strongly coking Sewickley-bed coal, ground to either 70 or 90 percent through a 200-mesh screen, was used.

Jan 1, 1954

By Phillip R. Moyle

A mineral survey of 19,350 acres of the Gooding City of Rocks Wilderness Study Areas (WSAs) in the north-central Snake River Plain was conducted by the U.S. Bureau of Mines in 1984. No formal mining districts are known in or near the study area. Forty-two placer claims within and adjacent to the study areas cover the Clover Creek diatomite deposit. Minor production from four pits was reported by the owners. The diatomaceous sediments are underlain by dacitic welded tuff and capped with basalt. Five exposures or blocks totaling 416 million tons of the diatomaceous material comprise the Clover Creek deposit; four of the blocks are in the study areas, out are predominantly covered by basalt. The North Clover block, just west of the areas, is only partially capped, and could be mined by open pit methods on the western flank of the exposure. The minable wedge contains an inferred marginal reserve of 35 million tons of diatomite possibly suitable for filter aid, filler, insulation, and other applications. At a production rate of 150,000 tons/year, total mining and milling costs for high-grade filter aid diatomite would be about $100/ton. The deposit is classed as marginal because products from this deposit may be inferior to currently marketed diatomite products. The market is well supplied by developed sources.

Jan 1, 1985

By G. L. Neumann

Owing to the need for additional sources of supply of both zinc and lead following World War II, the Bureau of Mines investigated many abandoned lead-zinc mines in the eastern United States. A series of shallow veins in south-western St. Lawrence County has long been a subject of speculation. These veins, which average about 4 feet in width and cut across the bedding of the country rock at right angles, are filled with calcite-carrying galena and sphalerite. The deposits have been worked sporadically during the last 115 years. From 1837 to 1852 the Coal Hill, the North, and the Victoria mines near the village of Rossie were at their peak of activity. Other calcite veins were prospected and a small production was realized. The Bureau of Mines began diamond drilling May 1, 1950, under the general supervision of McHenry Mosier, chief, Mining Branch, Bureau of Mines, Region VIII, and under the immediate supervision of the author) who was project engineer, following the preliminary examination by Robert S. Sanford. A total of 3,870.2 feet was drilled in 18 holes on four of the numerous deposits scattered over Macomb and Rossie townships. Drilling was completed September 21, 1950.

Jan 1, 1952

By Charles L. Harnes

A mineral pigment is a colored substance dug from the ground, which after treatment can be mixed with a drying oil to form a paint. Not all colored earths, however, can be made into satisfactory pigment. Much depends upon the attractiveness and uniformity of the color and the ease of purification. Mineral pigments are distinguished from chemical pigments by a difference in origin and treatment. Chemical pigments are not found ready-made in the earth but must be synthesized or otherwise obtained from other compounds or elements; for example, cadmium yellow, a chemical pigment, is precipitated from a solution of cadmium chloride, hydrochloric acid, and sodium sulfide.

Jan 1, 1942

By J. Grumer

The Bureau of Mines, under the sponsorship of the Space Nuclear Propulsion Office, conducted a laboratory-scale hydrogen safety study which determined several combustion characteristics of hydrogen diffusion flames. Experiments show that ambient air may enter the top of a hydrogen flare stack when the hydrogen flow is low. A new concept, supported by photographic evidence, predicts that diffusion flames burning in air on a wide, upright pipe (stack) and fed with slow, upward flows of buoyant gas will induce a downward flow of air along the walls of the pipe that can support combustion within the pipe. Predicted flamedip limits agree roughly with experimental values determined on 6-, 12-, and 18-inch-diameter stacks and increase with increasing stack diameter. Measurements were made of the limiting flow at which a hydrogen diffusion flame blows out in still air. By means of an empirical application of the critical boundary 8 velocity gradient concept, these data lead to a blowout limit of about 10 reciprocal seconds for a hydrogen diffusion flame. Burning rates of large hydrogen diffusion flames ranging from about 0.03 to 1 ft/sec were used to predict approximate flame heights on flare stacks. Temperatures of larger hydrogen diffusion flames up to about 3,600° F were observed, but the most representative value appears to be about 2,600° F. It was found that crosswinds do not strip significant amounts of unburned hydrogen from its diffusion flame and that water-cooled flare stacks are not likely to be damaged when flame is blown back into them by opposing winds.

Jan 1, 1970

By Gregory P. Cole, Peter G. Kovalchika, Rudy J. Matetic, Adam K. Smith

Previous studies conducted by the National Institute for Occupational Safety and Health (NIOSH) have shown that approximately 90% of coal miners and 49% of metal/nonmetal miners had a hearing impairment by age 501. Mine workers are exposed to additional noise levels underground due to the reflection of machine generated noise that would otherwise dissipate in an above ground setting. Determining the sound absorption coefficients is essential in modeling the sound field in an underground mining environment. Sound absorption is a measure of the amount of acoustic energy that strikes a surface and is absorbed, rather than reflected. The acoustic environment that mining machines operate in is a critical factor affecting the sound pressure level exposure for mining machine operators. Impedance tube testing is an inappropriate method for determining underground absorption coefficients due to the brittle composition of some of the materials such as coal and slate. Classic absorption coefficient estimation using T60 measurements will not work well in an underground environment because the theory assumes: a finite room, a diffuse field, and relatively uniform absorption. None of these assumptions are true in an open-ended mine entry. This paper will present a method using a ray-tracing technique to determine absorption coefficients for underground mines. Absorption coefficients are determined and presented for octave bands from 63 Hz to 8 kHz. The absorption coefficients will be essential for determining and predicting potential overexposure to machine operators in different mine environments.

By A. H. Cronk

This paper is one of a series being prepared by the United States Bureau of Mines on mining methods and costs in the different mining districts. The mining methods described in this paper are employed by one of the large mines in the Illinois fluorspar district. The mine is located at Rosiclare, Ill., and shipments are made over the Illinois Central Railroad: and by barge on the Ohio River.

Jan 1, 1930

By D. Harrington

"Coal—mine explosions are accidents that can and should be prevented. In former years hundreds of lives were lost each year in the United States as a result of such explosions, but after 1932 the numerous precautionary measures adopted had reduced their frequency and severity 75 percent or more until in 1940 several very disastrous explosions marred the good record. Unfortunately, both the number and severity of explosions seem to be tending to increase compared with the relatively good achievement from 1933 to 1940. The requisites for an explosion are ever present in all soft-coal and many hard-coal mines. A certain combination of circumstances, such as a flame or an arc in a cloud of dust or in a body of gas or both may start an explosion at any time. The fact that the frequency and severity of explosions were lowered for 6 or 7 years is no guarantee that such freedom from explosions will continue, as the bad record of 1940 has shown, and underground workers should feel honor bound to exercise the utmost care so that they will not help to bring about the circumstances that will cause an explosion.Although mine operators bear the main responsibility for preventing explosions, miners can do many things to help. As about 9 out of 10 explosions begin at a working face, it is largely within the power of workers to prevent them. All miners should do their part willingly and should not defend a fellow workman from punishment, even from discharge, for disobeying necessary rules, whose disregard may cause the death not only of the safety-rule breaker but also of many of his coworkers.When a miner is careless and is injured some other way than by an explosion he may be the only one to suffer, but if his carelessness causes an explosion he not only endangers his own life but also that of every other man in the mine and possibly the lives of persons outside the mine.Experiments have shown that ignition of as small a quantity as 150 cubic feet of an explosive mixture of methane and air under certain circumstances can start an explosion that will traverse an entire mine. Thus, ignition of an explosive mixture of gas 1 foot down from the roof and 13 feet back from the face of a 12-foot entry might cause a widespread explosion if the right quantity and kind of dust were present. Many persons have ignited much larger quantities of gas without being killed, but they survived only because dust, confinement, and other conditions were not exactly ""right."""

Nov 1, 1940

By Jr. Sillers

This is the third report of investigations dealing with the application of electrolytic manganese to steel-foundry practice and the seventh in a series of reports dealing with tests to establish the technological acceptability of electrolytic manganese in the iron and steel industries. The work was carried out by Metallurgical Division of the Bureau of Mines as part of an extensive program for the development and utilization of domestic ores. The electrolytic manganese used in the tests was produced by the Bureau at its Boulder, City, Nev., pilot plant by the process developed by the Bureau of Mines.

Jan 1, 1949

By Pakalnis Rimas, Lyndon Clark, Tom Brady

A major focus of ground control research presently being conducted by the Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is to incorporate data on weak rock masses into existing design relationships, with an emphasis on updating the span design curve for manned entries and the overbreak curve for longhole entries. Both curves were originally developed at the University of British Columbia, Vancouver, BC. The original database has been augmented by information from mines throughout the United States, Canada, Australia, and Europe. The common factor in all these mines is the presence of a weak back and/or walls. In most cases, the ore zone is the weakest rock unit and must be stabilized so that the mineral-bearing rock can be extracted safety. The current NIOSH research attempts to provide rock mechanics tools to assist a mine operator in making economic decisions that will also ensure a safe working environment. This paper documents the Nevada database with a special emphasis on Nevada underground gold mines.

By Ricardo Burdisso, Rahul Kadam, Kyle Schwartz, Marty Johnson

Occupational exposure to hand transmitted vibration (HTV) arises from the hand held powered tools extensively used in the mining and construction industry such as rock drills, chipping hammers, chain saws etc. Regular exposure to HTV is the major cause of a range of permanent injuries to human hands and arms which are commonly referred to as hand-arm vibration syndrome (HAVS). In addition to this, the percussive tools generate overall sound power levels in excess of 110dBA in most cases. Such a high sound power level greatly exceeds the maximum permissible exposure limit (PEL) of organizations such as National Institute for Occupational Safety and Health (NIOSH) and the Occupational Safety and Health Administration (OSHA). Long term occupational exposure to this noise has been diagnosed as the main reason for permanent hearing loss in the operators. It is therefore important to develop an understanding of the mechanisms which lead to these high vibration and sound levels and in order to do this a detailed computational model of a pneumatic chipping hammer has been made. This paper presents a nonlinear computational model of a pneumatic chipping hammer. In order to better understand the dynamics of the chipping hammer, the hammer was subdivided into components that are shown in figure 1 (a) (based on a chipping hammer manufactured by Atlas-Copco). The hammer mainly consisted of a center body, a moving piston and a chisel. Compressed air is used to drive the piston inside of a cylinder and on the downward stroke this piston impacts the chisel to create the hammer effect. The machine has one pneumatic valve and this valve regulates the air supply either to the upper chamber or to the lower chamber. The valve changes according to the relative pressures in the two chambers and the supply pressure. There are also twelve different exhaust ports at two positions along the cylinder labeled upper ports and lower ports. As the piston moves the ports can be closed or open (allowing exhaust). Fundamentally, the computational model was made up of two different sub-models, a fluid model and a structural dynamic model as shown in Figure 3 (a) and (b) respectively. The first sub-model takes into consideration the fluid dynamics of the machine since the hammer is driven by compressed air. Equations for the mass flow rate though bleed orifices (assuming an isentropic process) 1 is used to determine the mass flow into and out of the upper and lower chambers. From this the pressures in the two chambers and consequently the forcing on the piston can be calculated. The second sub-model deals with modeling the structural [ ]

Jan 6, 2006

By T. M. Ruff

A prototype mucking machine designed to operate in narrow-vein stopes was developed by Foster- Miller, Inc., Waltham, MA, under contract with the U.S. Bureau of Mines. The machine, called a compact loader-trammer, or minimucker, was designed to replace slusher muckers in narrow-vein underground mines. The minimucker is a six-wheel-drive, skid-steered, load-haul-dump (LHD) machine that loads muck at the front with a novel slide-bucket system and ejects it out the rear so that the machine does not have to be turned around. To correct deficiencies of the tether-remote-control system, a computer-based, radio-remote-control system was retrofitted to the minimucker. Initial tests indicated a need to assist the operator in guiding the machine in narrow stopes. An automatic guidance system that used ultrasonic ranging sensors and a wall-following algorithm was installed. Additional tests in a simulated test stope showed that these changes improved the operation of the minimucker. The design and functions of the minimucker and its computer-based, remote-control system are reviewed, and an ultrasonic-sensor-based guidance system is described.

Jan 1, 1992

By F. E. Diebold

The methodology for describing the geochemistry of elements in a coal seam have been developed. This has been applied to the Rosebud Coal Seam, which is an economically important member of the subbituminous coals of the Fort Union Formation in Eastern Montana. The method development has involved a detailed study of two popular techniques for determining the metal geochemistry of coal, namely, whole coal analyses and coal physical fractionation. The mathematically contrived element associations (whole coal analyses technique) and the element concentration trends in the float and sink fractions (physical fractionation technique) are considered to lead to only qualitative conclusions concerning the chemical associations of the elements in coals. Additionally, the processes taking place with the coal during low temperature ashing in an oxygen plasma are experimentally investigated and shown to be of sufficeint extent that the use of such low temperature ash for deciphering element geochemistry is questionable. The method developed in this study is a chemical fractionation that involves the sequential leaching of coal with water, 0.5 N HC1, 3 N HC1, 2 N HNO3, and 48% HF. These leach solutions are shown to selectively dissolve the predominate inorganic phases, sulfates, Ca and Mg carbonates, Fe sulfides and K alumino-silicates and quartz, respectively. These phases were identified with the use of XRD, SEM, EM and leaches (water and 0.3 N HC1) of whole coal and low temperature ash. The incorporation of the anion-exchange step in the leaching scheme was investigated and was observed to warrant further study of such intensity to be, at the time, unuseable. The use of this sequential leaching technique on several coal samples from the same seam generates element concentration trends that can be quantitatively interpreted with respect to the chemical associations of the minor and trace metals in the coal seam. The properties of the various seams of economic importance in the Fort Union Formation in Eastern Montana are compiled and presented. The subsequent conclusion is that there is not a large variation in the properties of these coal seams and that the variations within the Rosebud are within one order of magnitude. The chemical fractionation technique, investigated in this study, was applied to composite tipple samples of the Rosebud seam. Each composite sample represented 76,800 tons of coal. A minimum of 32% of the Ca and Mg are present as separate water soluble sulfates. An excess of the sulfate ion in the water extracts shows the predominating influence of the ion exchange capacity of the organic compounds in the coal. Based upon the CO content of the coal and the HC1 leachate data, 25 to 30% of the alkaline earth elements exist as separate carbonates and the remainder are associated with the organic compounds. The small fraction of the illite that dissolves in the HC1 and HNO3 leachates accounts for the K and Al. Slight dissolution of the pyrite in the HCl solvent occurs, the small amounts of Li and As do not relate to any known phase and Mn is present as a separate carbonate phase. Fe and a significant amount of the As exist in the pyrite that is dissolved in the HNO. Se is equally partitioned between the pyrite and the organic compound~. Most of the trace elements are found in the HF solutions. Li, V, and Cr were interpreted to be associated with the clay minerals (kaolinite and illite). Ni and Pb appear to be present as separate phases and 50% of the Hg is HF soluble but is not chemically related to any known inorganic phase.

Jan 1, 1983

By E. R. Spencer, E. Reeves

National Institute for Occupational Safety and Health (NIOSH) researchers conducted an investigation to quantify sound levels and to determine the amount of sound reduction provided by engineering noise controls installed in a talc processing plant. Baseline sound level and sound intensity measurements were performed at the plant and the measurement locations were recorded for comparison to post-control measurements. Follow-up measurements were then made at the same locations after the initial noise controls were installed. The plant subsequently decided to implement additional noise controls and the researchers returned to conduct measurements for a final analysis of all noise controls. The most significant results showed a sound level reduction in the main mill area from a range of 93-104 dB(A) down to 90-94 dB(A), and a total sound power level reduction of 21 dB(A) for air classifying mill 3.