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By H. -F. Krausse

Roof failures in underground coal mines are related to the lithology and geologic structure of the roof. There are two distinct suites of roof rock above the Herrin (No. 6) Coal in Illinois, and each has distinctive patterns of structure and roof failure. In black shale-limestone roof areas, roof instability is correlated with thinning of limestone beds and presence of faults and clay dikes. In gray shale roof regions, the prime roof hazards are posed by rolls, shear bodies, and presence of coal or carbonaceous partings in the roof. Most structural features examined are believed to have formed during early stages of sediment diagenesis and compaction. Structural trends and lithologic patterns are strongly interdependent for this reason. In many cases geologic patterns are so complex and locally variable that prediction of roof stability far in advance of mining is difficult. The need for greater flexibility in roof control planning is apparent.

Jan 1, 1979

By Lewis M. McNay

The Bureau of Mines located and examined 292 burning coal refuse banks throughout the Nation's coal-producing regions in 1968. These coal waste fires, extending over 3,200 acres, produce poisonous, acrid gases and particulate matter that pose a threat to health and safety in the surrounding areas, damage vegetation, and cause the deterioration of nearby structures and buildings. Methods of extinguishing coal refuse fires are discussed, and an approach to eliminating future occurrences of these fires is presented.

Jan 1, 1971

By J. E. Hamak

This publication contains analyses and related source data for 920 natural gas samples from 26 States and 2 foreign countries. All samples were obtained and analyzed as part of U.S. Bureau of Mines investigations of the occurrences of helium in natural gases of countries with free market economies. This survey has been conducted since 1917. The analyses published herein were made by mass spectrometer and chromatograph.

Jan 1, 1991

The Florida phosphate industry, which supplies about three-quarters of the domestic phosphate fertilizer, produces tremendous volumes of phosphatic clay wastes (slimes). These clays retain a high percentage of water for extended periods of time. The clays also pose an environmental hazard because the disposal technique involves aboveground storage behind earthen dams. Although much research has been undertaken by numerous organizations to dewater slime, no completely satisfactory solution has been developed. In June 1972, a cooperative effort by the Federal Bureau of Mines and the Florida phosphate mining industry was initiated to develop a solution for dewatering the Florida phosphatic slimes. This report discusses various aspects of the slimes problem, reviews past research, makes recommendations for future research, and includes a bibliography of references and patents dealing with the subject.

Jan 1, 1975

By L. Nahai

Overall mineral industry productive activity in Europe increased in 1965, following general upward trends in gross national product and total industrial production4 recorded. The gross national product of non-Communist Europe in market prices in 1965 was estimated at $572 billion and that of Communist Europe at $409 billion. However, the extractive sectors of the mineral industries generally did not fare as well as the processing sectors. In fact, a number of countries recorded lower production levels in this sector in 1965 than in 1964 and most countries had a lower growth rate in extractive industry output than in overall industrial output. Among the non-Communist nations of Europe, a general decline in coal production and lower levels of iron ore output in France, West Germany, and Luxembourg contributed significantly to the smaller growth rates or declines in extractive indexes. Where higher indexes were registered, this generally resulted from the performance of the petroleum and natural gas industry; exceptions were Greece, Norway, and Sweden. The decline recorded for Czechoslovakia was attributable entirely to poorer performance by that nation's coal industry.

Jan 1, 1967

By Winton Gale, David Oyler, Jinsheng Chen, Christopher Mark

The National Institute for Occupational Safety and Health’s (NIOSH) Pittsburgh Research Laboratory (PRL), RAG Pennsylvania and Strata Control Technologies of Australia have collaborated to conduct an extensive study of roof bolt strata interaction at the Emerald mine in Southwestern Pennsylvania. The primary goal of the project was to obtain detailed data on the interaction between the mine roof and the support elements for use in modeling studies. The study site was a longwall tailgate subjected to high horizontal stress. Three arrays of instruments were installed at the site, one in the tailgate entry and two in an adjacent crosscut. Pumpable concrete cribs were present in the tailgate array, and cable bolts were installed in one of the crosscut arrays. The instruments included mechanical and sonic extensometers for measuring roof movement, instrumented roof bolts, and three-dimensional roof stress cells. The study was ultimately successful in determining the magnitude of the horizontal stress concentration, the height of roof failure and the roof failure sequence, and the loading history of the primary roof supports.

By Juel H. Stears

The bureau of Mines analyzed data from 47 coal mine roof-fall resupport accidents that occurred from 1966 through 1974 to identify critical hazards .and problems. These accidents resulted in 62 injuries or fatalities. It was concluded that the majority of the accidents might have been prevented by observance of recommended practices and use of available technology such as setting temporary supports, adequate roof testing, etc. Additional work is needed in the following problem areas where present technology is inadequate: (1) warning of impending roof falls shortly before they occur, (2) better methods of detecting unsafe roof and ribs, (3) providing access to and temporary support of high roofs for testing and bolting, (4) reducing the noise level of stopers, (7) developing temporary roof support; that have greater stability and can be remotely installed, and (6) reducing the number of roof falls through better permanent support.

Jan 1, 1976

By Donald E. Redmon

This Bureau of Mines report reviews injury experience in the metallic mineral industries for 1966-67. For each of the years, 27 tables summarize disabling work injuries by department, source of injury, extent of disability, part of body injured, and nature of injury. Correlative information on employment, worktime, and operating activity is also presented.

Jan 1, 1973

By E. A. Rowe, G. H. Keith, B. D. Jones

An evaluation of electrowon tungsten powder was made by comparing its characteristics with conventional hydrogen - reduced tungsten powder . Electrowon tungsten powder was investigated with respect to particle size and shape , apparent density , flow rate , compressibility , green strength , and sintering characteristics . In addition , its chemical purity , absolute density , and purification by melting were determined . Significant findings were higher flow rates and better compressibility than hydrogen - reduced tungsten powder . However , the large particle size peculiar to the electrowinning process effectively prevented conventional sintering to a high- density material . The possibility of producing high - density material , using a new technique of hot swaging sheathed sintered - tungsten compacts , was demonstrated by the achievement of densities of 92 percent of theoretical .

Jan 1, 1965

By L. C. IlsLey

"During the last eight years there has been a noticeable increase in the use of permissible equipment in gassy and dusty coal mines. This trend has undoubtedly been toward greater safety in mining, but in spite of this all is not well ""along the front.""In many mines those in charge, either through ignorance or supposed economy, have neglected to install sufficient copper and maintain good bonding on the rails used for return circuits to have a safe working voltage for the permissible equipment which is intended to afford them safety.Low voltage, when properly analyzed, is not economy but frequently is an expensive oversight. Burned-out armatures, controllers, rheostats, and switches are costly in themselves to repair or replace, but the greatest cost in many instances is the loss of production resulting from idle and broken-down equipment.From a safety standpoint, excessive low voltage where permissible equipment is necessary is almost criminal negligence. A burn-out of any kind is liable to cause an arc that may burn its way through a casing wall and bring about a hazardous condition if gas or dust in explosive proportions should be present. Again, all wiring, both interior and exterior to the apparatus, is subject to the extra heating consequent upon low voltage. It should be remembered that if the voltage drops the current must increase a corresponding amount in order that the same work may be accomplished; and as the heating effect is as the square of the current, an enormous overheating of the electrical parts and wiring often takes place. This heating effect is especially detrimental to trailing cables used on portable equipment, because under the most favorable conditions the size of cable selected is only barely sufficient to do its work properly at a safe working temperature; therefore, when the extra current load is added because of poor voltage, overheating is sure to result, with consequent deterioration of the insulation, This effect greatly increases the liability of cable failures in service, and in turn adds to the hazards incident to the use of portable equipment of the permissible type involving the use of trailing cables.Some manufacturers have tried -to protect their equipment from low voltage, especially below a certain point, by -installing low-voltage relays which will trip when the voltage falls to a predetermined value. It is understood that some operators have hesitated or refused to install such low-voltage protection because they were aware that the voltage conditions were so poor that the equipment could not operate under the safe limits set. It is difficult to understand how any progressive company that is willing to go to the ex-pense of installing permissible equipment could be so shortsighted in this phase of common sense, safety, and economy."

Dec 1, 1929

By Arthur L. Crawford, R. E. Head, Fred E. Thackwell, A. Lee Christensen

"The data in this report are the result of a detailed, microscopic study of composite samples of mill products collected over a 14 day period. The samples were collected and assembled under the direction of W. R. Lindsay, superintendent of the Anyox plant, and are fairly representative of the heads, middlings, tailings, and products peculiar to the scheme of concentration practiced at Anyox in 1930.The work was done in the Cooperative Microscopic Laboratory at Salt Lake City, Utah. This laboratory was equipped by the mine and mill operators of the Salt Lake Valley and functioned under a cooperative agreement between the United States Bureau of Mines the University of Utah. This is the fourth of a series of papers 6/ dealing with a microscopic study of mill products."

Oct 1, 1935

By Ren G. Dong, Thomas W. McDowell, John Z. Wu, Chris Warren, Dan E. Welcome, Chun L. Dong

Hand forces are important factors for risk assessment of hand-arm vibration syndrome (HAVS).1 Grip force is one of the most important force components in the operation of powered hand tools. A considerable number of studies on grip force have been reported. It is well known that the grip force applied on a cylindrical handle is not uniformly distributed on each axis across the center of the handle cross-section.2 Therefore, maximum and minimum orientations of grip force exist around the handle. Such orientations have not been clearly identified. In a recently proposed international standard (ISO/CD 15230, 2005),3 it is stated that “the direction of the main gripping force is generally parallel to the z-axis defined in ISO 8727.” 4 This assertion is questionable, and further examinations are required. The objective of this study was to establish a fundamental theory on the distribution of the grip force around cylindrical handles. Methods As shown in Fig. 1, the grip force is defined as a vector composed of normal and shear components (FN & FT) in this study. Fig. 2 shows the hand coordinate system defined in this study, together with the ISO systems.1,4 Based on this novel grip force definition, we derived four fundamental properties and a theorem. More significantly, we formulated a novel hypothesis: similar to Mohr’s circle of stress, the normal and shear components can be represented approximately using an ellipse on the plane of the two force coordinates, as shown in Fig. 3. The maximum and minimum grip normal forces are termed as the first principal grip force (F1) and the second principal grip normal force (F2), respectively. Their corresponding orientations are termed as the first principal grip angle (a1) and the second principal grip angle (a2). A series of experiments were conducted to test this hypothesis. Twelve

Jan 6, 2006

In 1990, the Bureau of Mines (BOM) conducted a mineral investigation of the mines and prospects in the East Mojave National Scenic Area (EMNSA), San Bernardino County, California During field work, BOM identified 701 mines and prospects in EMNSA for which the geology, mineral resources, and mining history were compiled and summarized. Analytical results for 1,188 rock samples collected are tabulated. Total value of identified resources in EMNSA is $5.0 billion. Twenty-four mines and prospects were deemed profitable under current economic conditions. Development could generate considerable economic benefits to San Bernardino County. Potential economic benefits from mining the deposits were evaluated under the following access restrictions for EMNSA: 1) full access, 2) HR 3460, and 3) S 11/HR 780. Under the full access scenario, cumulative mine revenues are $3.0 billion, cumulative personal earnings at mines and supporting industries are $0.94 billion, and annual jobs at mines and supporting industries are 2,379. Under HR 3460, mine revenues, personal earnings, and annual jobs are $2.9 billion, $0.88 billion, and 2,165, respectively. Under S 11/HR 780, mine revenues, personal earnings, and annual jobs are $1.0 billion, $0.32 billion, and 936, respectively.

Jan 1, 1990

The United States Bureau of Mines frequently receives requests for information regarding the details of its organization and the nature of its activities. In response to such an inquiry a series of articles outlining the work of the bureau as a whole and of its different divisions was prepared and published in the United States Daily, Washington, D. C., during November, 1929. These articles are reprinted here in the hone that they may assist in giving the public a more complete understanding of the aims and purposes of the bureau and the methods by which it is laboring for the attainment of safer conditions and more efficient methods in American mineral industries. An index of these articles, with the dates of 'their publication in the United States Daily, is given below.

Jan 1, 1930

By Robert F. Randolph

Real-world levels of attenuation from hearing protection devices are usually much lower than the rated values obtained under near-ideal circumstances. The shortfall is even more extreme for earplugs than it is for earmuffs, primarily because of the complicated process of fitting the plugs within the ear canal. This study examines the use of a commercially-available lubricant for hearing aids to determine whether it would facilitate improved fit and attenuation for earplugs. In this experiment, ten participants inserted earplugs with and without using the lubricant. Average attenuation was assessed with the Real-Ear-Attenuation-at-Threshold (REAT) technique, and showed over 5 dB improvement when the lubricant was used. Participants obtained an 85% mastery rate using the lubricant versus a 50% mastery rate without. These results indicate several possible applications for improved earplug performance in real-world settings where hazardous noise is unavoidable and effective hearing protection is necessary.

Jan 1, 2008

By Richard L. Sanford

This report summarizes the results of the development of a Directory of Computer Programs Applicable to U.S. Mining Practices and Problems. The Directory includes a sampling of computer usage in operating and manufacturing companies, consulting firms, computer companies, research organizations, universities, and various U.S. government agencies. References to computer applications throughout the mining industry are presented as well as comments on the availability of programs to interested organizations or individuals.

Jan 1, 1977

By J. J. Jakosky, D. H. Zellers

"IntroductionThe Bureau of Mines has been conducting experiments in underground communication during a period of several years, and a brief summary of what has been done is as follows:During 1919-1920, investigations were conducted with the geophone. This instrument was used extensively during the World War for detecting enemy digging and mining operations, by means of the vibrations transmitted through the earth strata.A preliminary investigation using short wave-length (200 to 300 meters) radio equipment carried out jointly with engineers of the Westinghouse Electric & Mfg, Co. during 1922.The step was to investigate ground conduction signaling, (called T.P.S. in Signal Corps parlance)."

Nov 1, 1924

By R. August Heindl

A process for recovering manganese from open-hearth steel-plant slags was investigated. The proposed method of accomplishing this is indicated by the flow diagram in figure 1. Mixtures of open-hearth, steel-plant flush slags and limestone, so proportioned as to have molar [CaO -3P205] ratios of approximately 2, were fired at approximately 2,400° F. in an oxidizing atmosphere and then cooled slowly. This treatment produced a clinker consisting principally of two solid phases comprised of (1) various combinations of the oxides of manganese, iron, aluminum, and magnesium, probably in spinel complexes, and (2) a dicalcium silicate phase, which contains the phosphorus. Reduction of these clinkers with hydrogen or with gaseous mixtures containing CO, CH4, and other hydrocarbons at about 1,300° F. formed manganous oxide as well as varying amounts of ferrous oxide and iron. Carbon monoxide and mixtures of hydrogen and carbon monoxide effectively reduced the clinkers but also gave higher proportions of soluble iron when the manganese was extracted from the reduced clinkers by leaching at about 80° F. with ammonium carbonate solutions containing 26 to 28 percent ammonia and 15 to 26 percent carbon dioxide. It is believed that the manganese is in solution as an ammonia-manganese complex. Concentrations of about 90 grams of manganese per liter were obtained by batch countercurrent procedures. By distilling 50 percent of the ammonia, the ammonia-manganese complex was decomposed, and approximately 90 percent of the manganese was precipitated as the carbonate with the simultaneous precipitation of 15 to 30 percent of the iron, the larger amounts of iron precipitating in the continuous tests. The manganese-iron ratio in the product could be increased either by recycling more manganese from the distillation to the extraction or by aerating the liquor to purge it of iron before, rather than after, the distillation step. Calcination of the pelletized manganese carbonate in an oxidizing stmosphere at 2,000° F. or above gave a final product, Mn304, resistant to crushing and apparently possessing the other physical properties essential in a ferromanganese blast-furnace feed.

Jan 1, 1955

Bag stackers who use semi-automated palletizing machines and air slides may be exposed to high concentrations of dust. To reduce dust exposure, use an exhaust ventilation system in conjunction with an envelope of clean air over the bagstacker provided by an overhead air supply. Description of Hazard Mineral processing plants in the United States and throughout the world process material that is finely ground and placed into bags for shipping to the consumer. These bags normally range from 50 to 100 pounds in weight. Once the material is placed in these bags, a bag stacker loads the bags onto pallets. A bag stacker is exposed to a lot of dust that is mainly released by the force from loading the bag onto the pallet. The two main sources are the dust on the outside of the bag and the dust that escapes from inside the bag as it is loaded. The Mine Safety and Health Administration's (MSHA) records indicate the bag stacker's dust exposure is one of the highest of all workers at mineral processing operations. Ways to reduce the dust exposure and strain to the bag stacker are in constant development. Recently, automated systems have been built. These systems range from fully automated, which totally remove the worker from the bag-stacking process, to semiautomated systems, in which the bag stacker still performs some of the functions. This Hazard Control deals with controlling the bag stacker's dust exposure during use of a semi-automated palletizing machine. The worker slides the bags into position on the palletizing machine. Once an entire layer of bags is positioned, the bag stacker operates the controls on the palletizing machine to lower the layer of bags onto the pallet. An air slide is built into the semi-automated palletizing machine so the bags are easier to move. This slide uses a metal table with air jets that exit through small holes at high velocities, similar to an air hockey game. The dust problem occurs because the air slide causes dust to blow up onto the bag stacker, significantly increasing the dust exposure.

Jan 7, 2001

By Max L. Glenn

As part of its goal to minimize requirements for mineral commodities through conservation and substitution, the Bureau of Mines conducted research to develop molybdenum as a potential substitute for superalloys containing the strategic and critical materials, nickel, chromium, and cobalt. Since molybdenum requires protection from oxidation at high temperatures, several complex oxides of the spinel and perovskite structure were investigated to determine which possessed the greatest potential for use as oxidation-barrier coatings. Two spinels (MgCr204 and MgA1204) and five perovskites (BaHfO3, YCrO3, NdCrO3, BaZrO3, and LaCrO3) were selected for testing. Various high-temperature prop¬erties that are important for oxidation-resistant coatings were examined, including diffusion rates of oxygen and molybdenum, recession (vaporization) rates, hardness, erosion resistance, sinterability, reactivity with molybdenum, and ease of application. From the evaluation of high-temperature properties, two spinels (MgCr204 and MgA1204) stand above the other oxides as possible coatings for molybdenum. However, laboratory coatings of MgCr204 at 1,360° C (2,480° F) are equivalent or inferior to currently available MoSi2 coatings; laboratory coatings of MgA1204 may be comparable under limited conditions to currently available MoSi2 coatings at the same temperature.

Jan 1, 1979