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By C. P. Mangelsdorf

When the finely bedded shale frequently encountered over coal seams experiences a separation, the material below the separation must behave like a beam or plate in that it must resist both bending and shear. Be-cause of the weakness in interlaminar shear inherent in such strata, shear deflections that are usually ignored in isotropic beam theory may account for a significant part of the total roof sag. Similarly, when a roof truss is installed in such a roof the upward displacement reducing the sag will have components due to shear as well as bending. Questions asked by mine operators about the installation of roof trusses frequently deal with optimum position, slope, and initial tension of the inclined chords. This Bureau of Mines report examines the effects of those chord parameters on the strain energy of both shear and bending and offers optimum values that will minimize the total strain energy of the immediate roof. Design charts are provided, several design examples are included, and the results are compared with current practice. The effects of in situ stresses are investigated and are shown to be equivalent to an additional load on the beam.

Jan 1, 1988

In 2004, data obtained from the Mine Safety and Health Administration (MSHA) indicated a total of 891 underground (6.2%) and 13,587 surface (93.8%) mining operations.

Sep 1, 2007

By CDC CDC

In 2004, a total of 251 metal mining operations reported employment to the Mine Safety and Health Administration (MSHA). Metal mines were the smallest mining commodity sector, comprising 1.7% of all mining operations. • Gold mines

Sep 1, 2007

By E. J. Lintner

This paper is one of a series being prepared by the United States Bureau of Mines describing gypsum mining and crushing methods and costs at various operations throughout the United States. These papers are designed to disseminate technical information regarding methods used. The cost tabulations represent local operating expenditures only and not total production costs. It is recognized that publication of total production costs may in many instances cause embarrassment to individual operators as well as to the industry as a whole. On the other hand, operating costs are essential to a technical discussion and study of the methods employed. The attention of the reader is called specifically to this differentiation so that there may be no misunderstanding of the scope of the cost tabulation. This paper deals specifically with the mining and crushing methods employed by Victor Plaster, Inc., Victor, Ontario County, N. Y. The maximum annual production capacity of this company is 150,000 tons of crushed gypsum. The methods and practices employed arc typical of those followed in the gypsum mines in western New York State. The shaft is, perhaps, the deepest and the thickness of the gypsum mined is above the average for the section.

Jan 1, 1937

By V. F. Parry

Under the present emergency every consumer should store as much coal as he can. Although there is no shortage of coal, there is likely to be a shortage of labor to mine excessive quantities in the fall, and railroads cannot be expected to deliver coal promptly on account of the need for transporting war materials. Some miners must join the armed forces, and those who are left may be unable to mine coal as rapidly as you will need it when winter comes. When the first cold days arrive, there may be a shortage of trucks to deliver coal. Deliveries may be planned in advance, and your turn might not come until it is too late.

Jan 1, 1942

The STATE MINERAL SUMMARIES publication provides estimated data and summaries of mineral activities at the State level for 1993. Most of the estimates are based on nine months data. Individual State summaries are published separately as State Mineral Industry Surveys and copies can be obtained from the appropriate State mineral officer. In an effort to facilitate the rapid dissemination of information and publications produced by the U.S. Bureau of Mine, an electronic document dissemination system is now available for use. MINES FaxBack is a simple-to-operate automated fax response system that operates 24 hours a day, seven days a week. All a user needs is access to a fax machine with a touch-tone telephone. MINES FaxBack can be accessed by calling (412) 892-4088, using the touch-tone telephone attached to the user's fax machine. After calling MINES FaxBack, the requester is guided by a series of voice messages to assist in ordering the desired documents.

Jan 1, 1994

By J. E. Murphy

The Bureau of Mines developed a hydrometallurgical method for recovering mercury metal from mercury sulfide concentrates. Sulfide flotation concentrate from the McDermitt Mine was leached in a cupric chloride solution at 80° C. The redox potential of the solution was maintained at 850 mV during leaching by chlorine sparging. Mercury extractions exceeded 99 pct in 3 h of leaching. After leaching, the pH of the solu-tion was increased from 1 to 4.5 to precipitate copper as atacamite. The pregnant solution typically containing 100 giL Hg was sent to elec-trolysis to produce high-purity mercury metal and chlorine for recycle. In a 200-A electrolytic cell operated for 24 h, current efficiency was 99 pct and the energy requirement was 0.9 kW·h/lb of mercury produced. Mercury removal from the waste stream was also investigated. Iron or zinc cementation, sulfide precipitation with H2S, and activated carbon adsorption all decreased the mercury concentration from 10 giL to 0.01 mglL, which is less than the Environmental Protection Agency limit on wastewater of 0.02 mg/L.

Jan 1, 1987

By Robert D. Thomson

Sheet mica is an important material in the manufacture of electronic and electrical equipment. Large quantities are consumed each year as an essential component in generators, transformers, radios, television sets, radar, electric lighting equipment, and electrical appliances. The nature, structural imperfections, and impurities determine to a great degree the usefulness of sheet mica. Proper processing and classification add greatly to its market value. This report is designed to assist producers in understanding the complexities of marketing muscovite sheet mica. ACKNOWLEDGMENTS Special acknowledgment is due S. A. Montague, of Spruce Pine Mica Co. and G. A. Purcell, mica consultant, General Services Administration, for their critical review and many helpful suggestions in the preparation of thin report. Assistance from other industry and Government representatives is acknowledged with thanks.

Jan 1, 1955

By Gregory P. Cole, Jeffrey Shawn Peterson

The Pittsburgh Research center3 conducted research to study and improve electrical fault detection on coal mine direct-current (dc) trolley systems. A suspended trolley line delivers power at voltages of 300 or 600 V dc to the haulage equipment and other loads. Roof falls or other accidents may force the trolley line down so that an electrical fault current may flow between the trolley line and rail. This fault current could result in localized heating, arcing, and perhaps fire. Such faults are not always preventable by the existing circuit protection because the current magnitude is well below typical operating levels of the trolley system. The research discussed in this report studies the applicability of computerized signal analysis techniques to solve this problem. Tests were conducted at cooperating coal mines. Measurements were taken during normal loading of the trolley system (light, intermediate, and heavy traffic), during induced fault conditions (arcing and bolted faults), and during transitions between the two. These data were then used to train and test a microprocessor-based fault detection algorithm. Later, field tests of the detection algorithm found that it correctly classified the state of the trolley system greater than 95% of the time.

Jan 1, 1997

By D. Harrington

The occurrence of dust in mines has always been a source of trouble, but for any years, and virtually up to the beginning of the present century, relatively little of a definite nature was known as to the numerous ill effects of dust in mining operations. Even today, with the west amount of time given and attention paid (for at least 40 years in various, countries) to research and observation en dust in mining, and in spite of the experience with it, much information remains to be obtained, before definite, well-authenticated statements can be made as to numerous features connected with the occurrence of dust in Dines an of its effect upon the health and safety of the worker. One statement that can be made with relatively good assurance of being uncontradicted in that dust is a real menace to the well-being of mine workers, and this includes both health and safety. In addition, dust in and around mines and mining plants is one cause of large financial losses to mine owners and operators. FORMATION OF DUST IN COAL MINES IN THE UNITED STATES One definition of mining is "the processes by which useful materials are obtained from the earth's crust; " since virtually all of the useful materials of or in the earth's crust either are solids or must be reached by penetrating through solids, the materials that are moved in mining must necessarily be broken or disrupted, so that almost every phase of the work of loosening the material and transporting it is likely to produce dust.

Jan 1, 1939

By E. G. King

Strontium sulfide and barium sulfide occur as intermediates in commercial treatments of the impure natural sulfates to produce pure strontium and barium chemicals. Thermodynamic considerations involving these sulfides have been hampered by lack of basic data, such as the entropies at 298.15°K. This paper reports the results of heat capacity measurements of strontium sulfide and barium sulfide in the temperature range 50°-298°K. The entropies at 298.15°K. were derived from the heat capacity values. Free energies of formation at 298.15°k. were computed from the entropies and literature values of the heats of formation. Strontium sulfide and barium sulfide are thermo-dynamically less stable than calcium sulfide, but more stable than magnesium sulfide.

Jan 1, 1960

By John D. Bardill

This report covers the magnetic surveying done in the Plattsburg area , which was part of a general survey, of magnetite deposits in New York State . Other areas being surveyed are the Star Lake district , St. Lawrence County ; Brewster district , Putnam County; and the Sterling district , Orange County. Reconnaissance indicated an area about 3 miles long and 1,200 feet wide , but detailed surveys have been completed on only a portion of that area . In several districts , surveys of this type have served as a basis in the selection of areas for exploration by diamond drilling by the Bureau of Mines .

Jan 1, 1947

By Albert L. Toenges, Henry E. Dekay, James N. Scudder

Support of the immediate roof in coal mines is essential for their safe operation, and timbers are the most common means of support. Their effectiveness depends upon their resistance to decay. The theory has been advanced by some mine operators that rock dust, which is applied to ccal-mine workings to prevent propagation of explosions, accelerates the decay of mine timbers. As the results of part 1 of this study were inconclusive, the study was continued. Its principal objectives are: 1. To determine the effect of rock dusting upon decay of mine timber. 2. To compare the extent of decay of timbers in two mines in which underground conditions are similar. 3. To determine the loss in strength of the timbers after exposure to mine atmosphere. The studies were carried on in the Crucible mine of the Crucible Fuel Co. where the first part of this study was made, and in the Isabella mine of the Weirton Coal Co. The mines are on the Monongehela River and are adjacent.

May 1, 1943

By B. J. Dalton

The Bureau of Mines Helium Research Center has developed a computer program for solving two-phase equilibria data for binary mixtures and for evaluating thermodynamic functions of interest, including all critical points. This computer program was used to calculate equilibrium points on the PVTu surface for the helium-nitrogen system as predicted by the Van der Waals equation of state. Numerical values are tabulated and illustrations are presented for 1,279 equilibrium points and for quantities needed to construct Ponchon diagrams. Equilibrium ratios as a function of pressure at constant temperature and of temperature at constant pressure-are also shown graphically. In addition, saturated partial molal volume and partial molal enthalpy data are given. It is shown that the Van der Waals helium-nitrogen system exhibits retro-grade condensation of the second type for liquid helium concentrations of about 0.07 mole fraction or less and pressures below about 45 atm. It is also shown that the critical point is at a -maximum value of pressure (at constant temperature) and of temperature (at constant pressure).

Jan 1, 1971

By S. A. N. Sheya

Many gold-bearing ores in the Western United States also contain small amounts of mercury. The presence of mercury creates potential pollution and health hazards during several steps in gold processing. An investigation was undertaken by the Bureau of Mines to develop techniques for removing mercury from cyanide mill solutions by selective electrowinning to reduce the potential hazards. Sixty-five percent of the mercury was selectively electrowon from synthetic carbon strip solution at applied potentials of 1.00 to 1.50 V when using a mercury-coated platinum or copper plate cathode. Increasing the active surface area by using mercury-coated copper wool resulted in up to % pct of the mercury being electrowon from mill carbon strip solutions that contained 1.9 to 20 ppm Hg, 20 to 345 ppm Au, and 0.35 to 39.5 ppm Ag. About 98 pct of the silver was electrowon with the mercury onto the mercury cathode. Gold extraction ranged between 0 and 20 pet. Results of the investigation showed that choice of cathode material was critical to the success of the process. Selectivity was not achieved using uncoated steel wool cathodes.

Jan 1, 1988

By Roswell W. Prouty

As part of a general plan for control and economic utilization of the waters of the Missouri River Basin as well as development of its inherent power resources, the Corps of Engineers of the United States Army has under construction a rolled earth dam near the site of old Fort Randall in South Dakota. The dam is in Charles Mix and Gregory Counties on the Missouri River at a point about 922 miles above its mouth. It is approximately 125 air-line miles southeast of Pierre and 55 miles southwest of Mitchell, S. Dak. The storage reservoir to be formed by the dam will extend upstream for 150 miles and, at maximum operating pool level, will cover an area of some 107,000 acres. It will have a storage capacity of 6.2 million acre feat.

Jun 1, 1949

By C. H. Herty, J. K. Gaines

"Nearly every piece of electrical equipment used in mines ""breathes."" In other words, motors, controllers, rheostats, switches, and other similar equipment, even though encased in seemingly tight compartments, breathe in the atmosphere that surrounds them.As the apparatus is used, the temperature of metallic parts is changed generally in positive direction through the heat by friction and the heat due to the electric current. When the apparatus is idle it gradually cools down to the temperature of the surrounding atmosphere.This increase of temperature during operation and return to normal temperature when operation stops alternately raises and lowers the temperature of the atmosphere within the compartments which, in strict accordance with Charles' law -T = VT1 V'will expand or contract in proportion to any given temperature change.As compartments are not gas-tight, such expansion and contraction will force the atmosphere out of the compartment =on expansion and suck the surround¬ing atmosphere into the compartment during contraction, hence the term ""breathing.""Investigators of explosion-proof equipment have recognized that such an interchange would take place and have designed their equipment to safeguard possible explosions within the compartments."

Jul 1, 1927

By D. A. Reynolds, C. R. Holmes

The Bureau of Mines - American Gas Association ( EM - AGA) carbonization test has been used to determine the carbonizing properties of 66 American coals and a larger number of coal blends . A summary of the results obtained for the first 30 coals , including 6 blends , has been published ,4/ and results for individual coals have been reported as the investigations were completed . A bibliography of all publications pertaining to this work has been issued recently . Many of the coals were carbonized at 800 ° and 900° C. in two sizes of retorts ( 13- and 18 - inch diameters ) ; and , because the quality of coke is affected by changing the size of the retort , this report has been prepared to show the average physical properties of coke from the two sizes . This report also purposes to extend the correlation of the physical properties of coke with the rank of coal made by Fieldner and Davis in their summary of the EM-AGA tests on the first 30 coals .

Jun 1, 1942

By Jeanne A. Zimmer, Brad Smith, Steve Viles, Andrew B. Cecala

A recent report evaluating silica exposure levels in the metal/nonmetal mining industry noted that bag packaging and loading are some of the occupations at the greatest risk. In addition to dust problems, the bag-stacking process is labor intensive, making lost-time injuries common due to back fatigue and strains. During the bag-stacking process, a significant amount of dust can be generated, mainly from product on the outside of the bags and from dust escaping the bag valve upon impact of the bag on the pallet. In an effort to address dust-exposure and back-fatigue issues, Malvern Minerals Co., Hot Springs, Ark., made two major improvements to its ground silica stacking facility. First, the company purchased a semi-automated bag palletizing system (Figure 1). With this system, the bag stacker does not lift the bags, but slides them across a metal table. Small jets of air exit through perforations in the table top (similar to an air hockey game), allowing workers to more easily slide each bag into the proper position. After each layer of bags is completed, the table slides open, and the entire layer of bags is loaded onto an underlying pallet. The table then closes, readying it for another layer of bags. After the entire pallet is loaded, the unit delivers the pallet to a shrink wrap and forklift pick-up area. In addition to this semi-automated palletizing unit, Malvern Minerals purchased an Overhead Air Supply Island System (OASIS) to lower the bag stacker's dust exposure. The OASIS takes outside air, directs it through MEASURING RESPIRABLE DUST The bag stacker's respirable dust exposure was monitored using a RAM-1 instantaneous dust monitor to evaluate the impact of the various changes on the palletizing process and dust-control equipment. The bag stacker wore a vest that held the 10-mm Dorr-Oliver cyclone, which classifies the respirable portion of dust. Flexible tygon tubing was used to connect the cyclone to the RAM-1 dust unit, allowing the bag stacker to perform the palletizing process with minimal interference. The RAM-1 measures respirable dust concentrations by light scattering with a sensing chamber. This device closely simulates gravimetric measurements when calibrated for a specific dust. This instrument is ideal for comparative evaluations, as was the case in this study. Since the RAM-1 is not an MSHA-approved instru¬ment for dust compliance sampling, the dust concen¬trations listed in this article should be used as a com¬parative value of respirable dust concentration and not to determine actual dust concentrations from a com¬pliance standpoint.

By William A. Beck

This paper is one of a series, describing current practice in diamond drilling for production at various mines throughout the United States. It describes the drilling and blasting methods, used at the Tennessee Copper Co., which started using deep-hole drilling for blasting in 1927, employing inde- pendent, rotation percussion drills with sectional drill steel. Since 1942 the company has employed diamond drills for deep-hole drilling. This method has now passed the experimental stage and promises to become permanent. The elimination of rock dust and safer working conditions for the drill crews are listed as the main advantages. The higher initial cost of equip- ment is the principal disadvantage.

May 1, 1948