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By R. V. Ramani, J. Qin

"During the mining process, the insitu material is broken into different size ranges, from very, large pieces to very fine particles. Some of the fine particles become airborne. In underground coal mining, airborne respirable. dust is associated with health and safety of the miners: The amount and size distributions of airborne dust are important parameters to effective dust control measures. The design of underground mine experiments, including sampling procedures and sample analyses methods to determine these parameters are presented in this paper.. A total of fifteen continuous miner cuts were sampled. The amount of dust generated during the cutting process and the relationship between total and respirable airborne dust concentrations and amounts are examined.The amount of respirable dust airborne is on the average only. 0.016% of the respirable dust generated. On the average, 61% of the total .airborne dust measured is in the respirable size range. The amount of respirable airborne' is on the average 36% of the respirable size fraction in the total airborne dust. For equal proportion of rock and coal material cut, rock contributes about twice as much fines (<0.22 mm) as coal. Additional fundamental research is necessary to further the understanding of 'the airborne propensity of respirable dusts in mine atmospheres.INTRODUCTIONMining is a sequential process of breaking, gathering, loading, and transporting the in-situ .materials.' In underground coal mines, duet in both the non-respirable and respirable size ranges is generated and entrained in every phase of the process. Even though large amounts of dust particles' adhere to run-of-mine coals, part of the dust generated becomes airborne (Cheng and Zukovich, 1973). Studies have shown that bit type affects the amount of dust generated'(Evans and Pomeroy, 1966; Kurth et al., 1975; Roepke et al., 1976; Stecklein et al., 1982; and Khair and 'Reddy, 1986). Deep cutting can reduce airborne dust generation (Black and Schmidt, 1977 arid, Black et 1978). Mechanical properties of. coal seams are also important factors in dust generation. Laboratory studies have shown that Hardgrove Grindability Index (HGI) of the coal has a relationship with the amount of respirable. dust generated (Beafi and Ramani, 1979; Moore and Bise, 1984; and Moore, 1986). However, these relationships have not yet been validated with' data from the mines. The amount of dust airborne depends on a number of factors. Suppression of the airborne propensity of dust by water sprays is'widely practiced and is very effective. Water flow rate; pressure and configuration of water sprays have been identified as major factors affecting dust capture by sprays (Courtney and Cheng, 1977; Courtney et al., 1978; and Kissell et al., 1979). Ventilation is a very important means of controlling the dust level at the coal face (Jayaraman, 1977). According to a National Academy of Sciences study (1980), the mechanism of dust generation and the process by which the generated dust becomes airborne are complex and not yet completely understood coal seams are also important factors in dust generation. Laboratory studies have shown that Hardgrove Grindability Index (HGI) of the coal has a relationship with the amount of respirable dust generated (Beafi and Ramani, 1979; Moore and Bise, 1984; and Moore, 1986). However, these relationships have not yet been validated with data from the mines. The amount of dust airborne depends on a number of factors. Suppression of the airborne propensity of dust by water sprays is widely practiced and is very effective. Water flow rate; pressure and configuration of water sprays have been identified as major factors affecting dust capture by sprays (Courtney and Cheng, 1977; Courtney et al., 1978; and Kissell et al., 1979). Ventilation is a very important means of controlling the dust level at the coal face (Jayaraman, 1977). According to a National Academy of Sciences study (1980), the mechanism"

Jan 1, 1989

By S. R. Borrowman

Mill tailings from conventional uranium extraction processes contain nearly all of the radium originally in the ore. Such tailings require controlled storage in perpetuity to safeguard the surrounding environment from radioactive contamination. Alternatives to controlled storage of the tailings are (1) removal of the radium from the tailings for separate storage or use or (2) removal of the radium when processing the uranium ore. In laboratory tests conducted by the Federal Bureau of Mines, radium was leached from tailings using either hydrochloric acid or ethylenediamine tetraacetic acid. A hydrochloric acid leaching method was used to extract both radium and uranium from the ore to yield tailings containing less radium than those produced by either conventional sulfuric acid or alkaline leaching processes. From 77 to 94 percent of the radium in mill tailings was concentrated by sedimentation in slime fractions representing nearly 25 weight-percent of the original sample.

Jan 1, 1975

By D. Harrington

"In order to stimulate general interest in mine safety among their employees the mining companies of Butte, Mont., instituted in 1918 a Miners' Field Day, and this field day has since been held annually about the end of July, the last one being on July 25, 1921. The mining companies of the Butte district finance this meet in proportion to the number of men employed at the time of the meet, the contributing companies with number of working force, end proportional contributions for the opening field day in 1918 being given below:COMPANY NUMBER EMPLOYED AMOUNT CONTRIBUTEDAnaconda Copper Mining Co.,12,500,$ 1,078.53Butte & Superior Mining Co.,1,800,155.32North Butte Mining Co.,,1,294,111.67East Butte Copper Co.,,850,73.36W. A. Clark Interests,,600,51.78Davis-Daly Mining Co.,,340,29.35,,,,17,384,$ 1,500.00*Note: In many mining districts it is now the custom to hold an annual Miners' Field Day. The field day, as a rule, is financed principally by the mine operators, and was instituted primarily to promote interest among miners in the ""Safety First"" movement. Usually demonstrations or contests in first aid and mine rescue are the leading feature of the day's events, which include games, races, dancing, and all the other amusements usual to a gala holiday. Thus the field (ley serves the double purpose of stimulating interest in mine safety and promoting cordial relations and community fellowship. This paper is an interesting account of the way in which the Miners' Field Day in the Butte district is organized, with data on costs, plan of organization, method of conducting, and the practical benefits derived from it. - Ed"

Oct 1, 1921

By F. N. Kissell

The applicability of the "direct method" for determining the methane content of virgin coalbeds was tested. Preliminary results indicate that the direct method, when applied to exploration cores, can be successfully used to estimate coalbed gas content and also approximately predict the total gas emission from a prospective mine located in the coalbed at the exploration site.

Jan 1, 1973

By Lloyd A. Morley

This Bureau of Mines publication presents a comprehensive review of mine electrical power-system theory and practice. It discusses fundamental theory and the vital aspects to be considered in planning and designing mine electrical power systems. The report is divided into three major sections. The first presents the history of electricity in mining and the fundamentals of electrical phenomena and components. The second focuses on power-system components: motors, grounding systems, cables, and protective equipment and devices. The final section includes mine power-center equipment, switchhouses and substations, batteries, and mine maintenance.

Jan 1, 2003

Provide a means of recovering precious metal values from finely ground tailing materials. Approach Determine the procedures needed for agglomerating the finely ground material for subsequent heap-leach cyanidation of the precious-metal-bearing tailings. Applying Agglomeration/Heap-Leaching to Fine Tailings Agglomeration technology was developed by the Bureau of Mines to provide cost-effective recovery of precious metal values though better heap leaching of clayey or low-grade ores. While many precious metal producers have adopted this technology to reclaim precious metals from crushed ores and wastes, other operations have experienced problems in using the heap leaching technique effectively on piles of fine tailings. In contrast to the coarser ore and waste material, most tailings piles contain more than 50 percent minus 200 mesh materials with no coarse material. Fine particles and clays present in the pile can impede 8 uniform flow of the leaching solution through the heap, thus preventing efficient and cost-effective precious metals recovery.

Jan 1, 1986

By D. S. Kingery, F. F. Kopsch

The practice of using two or more main ventilating fans is common at large coal mines throughout the coal-mining industry. To assure adequate and efficient ventilation at may mines, such multiple-fan systems are necessary. The hazards associated with interrelated ventilating currents if a fan fails are controversial, and to date little effort has been made to study this specific problem and to determine corrective measures. The obvious questions are: 1. Is there a hazard? 2. Under what circumtances does it exist? 3. How serious is it? 4. What are corrective measures? Most members of the mining fraternity agree that reduced quantities of air and changed airflow patterns introduce potential hazards, especially where gaseous conditions exist when mechanized methods are used in concentrated mining 0 The seriousness of the hazard depends on the ease with which methane accumlates in face areas or haulage roads, the quantity of methane in workedout areas, and the extent to which reversed air currents interfere with escape and recovery operations after mine fires or explosions. These studies cover three mines and give the distribution of air for the specific conditions show. Each mine probably has somewhat different airflowpressure relationships between fans. This depends on the number of fans, the

Jun 1, 1959

By W. P. Yant, G. W. Jones

During the testing of porcelain insulators with a " 60 - cycle flash - over apparatus " , gases are liberated having an odor greatly resembling that of ozone . Since the two main constituents of normal air are nitrogen and oxygen , and high voltages (approximately 90,000 volts ) are used during the tests , the conditions are favorable for the production of ozone or oxides of nitrogen , and perhaps both simultaneously . The presence of these gases is only noticeable during the testing period . They soon disappear after the test is over . No fatalities have ever resulted from these gases at the plant visited nor are there any records of any of the men who worked on the tests being confined to their homes from this cause . New employees sometimes complain of a depressed feeling and shortness of breath , which is most noticeable after leaving work and getting into fresh air , but they som become accustomed to it and no ill effects are noticed . In view of previous work*** which the Bureau of Mines has done on oxides of nitrogen in connection with mine gases and problems in gas analysis , tests were made at the plant of the Westinghouse High Voltage Insulator Company at Derry , Pa . to determine the kind and amount of gases liberated .

Jun 1, 1923

By J. Koster

During the past several years, alunite from the Marysvale (Utah) region has been the subject of investigation by the Electrometallurgical Section of the Bureau of Mines. The nature and occurrence of this mineral, with considerable data on the Utah deposits, together with a number of results of preliminary experiments, have been given in a previous report.6/ The geology of the Marysvale region has been reviewed recently.7/ The present paper reports the results obtained by a method involving the sintering of alunite with boric acid and subsequent treatment of the sinter to produce alumina and potassium sulphate.

Jan 1, 1939

By J. Koster

During the past several years, alunite from the Marysvale (Utah) region has been the subject of investigation by the Electrometallurgical Section of the Bureau of Mines. The nature and occurrence of this mineral, with considerable data on the Utah deposits, together with a number of results of preliminary experiments, have been given in a previous report.6/ The geology of the Marysvale region has been reviewed recently.7/ The present paper reports the results obtained by a method involving the sintering of alunite with boric acid and subsequent treatment of the sinter to produce alumina and potassium sulphate.

Jan 1, 1939

By D. B. McGilvra

This paper, describing the mining practices and methods at the Black Rock mine, is one of a series of similar papers on mining methods in the various mines of the United States being prepared by the Bureau of Mines. The Black Rock mine is located in the northeast corner of the Butte district, about 3 miles from the center of the town of Butte, and is owned and operated by the Butte & Superior Mining Co.

Jan 1, 1930

By Fred N. Kissell

A parachute-type stopping intended for changing the course of mine ventilation air during mine emergencies has been designed and tested. Some production uses are also visualized for metal mines. Preliminary tests in the laboratory and underground indicate that the parachute stopping is a workable concept, but further developmental research is required.

Jan 1, 1975

By S. E. Khalafalla

The Bureau of Mines investigated variations in the activation energy for the carbon monoxide reduction of magnetite and ferrous oxide with respect to the state of aggregation of the oxide material. Reduction phenomena can only be satisfactorily explained by including an adsorption step in the reduction process. Summation of the values of the exothermic heat of chemisorption and the variable apparent activation energy for reduction yields a nearly constant value of about 50 kcal for either ferrous oxide or magnetite regardless of whether they are aggregated in pelletized form or coarsely crystalline particles.

Jan 1, 1965

By Donald R. Corson

The Bureau of Mines is conducting research on the effects of various established and potential soil-stabilization additives to hydraulic backfill. This initial phase is an evaluation of the effect of inclusion of varying amounts of Portland cement and combinations of cement and a dispersant on the bearing strength of backfill. Results of unconfined compression tests are given for over 200 sample cylinders incorporating a fill material with cement or cement and dispersant. Inclusion of a minor amount of dispersant (0.2 percent by weight) is found to yield a significant increase in strength for 20-to-1 and leaner sand-cement mixes. An apparent optimum concentration of dispersant exists beyond which no further increase in strength is achieved. A dispersant-cement ratio of l.8- to-1 yielded a strength increase of 515 percent over the strength of untreated 40-to-l sand-cement mixes.

Jan 1, 1966

By W. P. Yant

A previous report of the Bureau of Mines dealt with the toxicity of dichlorodifluoromethane, a new refrigerant that has a remarkably low toxicity. Continued research by the Frigidaire Corporation and toxicological experiments performed in the Laboratory of Applied Physiology of the University of Cincinnati revealed another organic fluoride, dichlorotetrafluoroethane, whose toxicity also appeared to be of a very low order and whose physical and chemical properties make it suitable for refrigeration purposes. In addition to low toxicity, safety in its use is further enhanced by its physical properties, which permit the design of equipment that operates at comparatively low pressures and hence mitigates the dangers and problems of leakage. The investigation described in this report was performed by the Bureau of Mines at the request and with the cooperation of the Frigidaire Corporation.

Jan 1, 1932

Maps To Accompany Bulletin 494

Jan 1, 1950

By R. D. Van Zant

The method for smelting zinc in horizontal retorts developed several centuries ago is still in use. This process consists essentially of the reduction of zinc oxide by carbon at 1,200° to 1,400° C. in a fire-clay retort. The reaction is highly endothermic, and a high radiation loss occurs in transferring the heat of reaction through the fire-clay walls. In recent years, silicon carbide retorts with much better heat-transfer characteristics than fire clay have been supplanting the old retorts. The practical impossibility of recovering the carbon monoxide formed in the reduction causes a large loss of fuel. Intermittent smelting is done in small retorts that are manually charged and discharged, and the furnace crews must be specially trained if efficient results are to be obtained. During the past 20 years several processes have been introduced that have substantially improved the horizontal-retort process. One of these, developed by the New Jersey Zinc Co., consists of a continuous process in which a briquetted mixture of zinc sinter, reducing agent, and binder is coked at 750° to 900° C. and charged into a vertical silicon carbide retort. A supply of displacement air or exhaust combustion gas is introduced at the base of the retort at an appropriate pressure in order to keep the zinc vapor from condensing on the cooled residue in the lower part of the retort. Any .oxidizing constituents in the displacement gas are converted to carbon monoxide by reaction with the carbon in the charge. The spent residue is continuously removed at the bottom of tl1e retort. The chief advantages of this process are said to be increased output per man-day, improved working conditions, high recovery of zinc, increased thermal efficiency, and long retort life.

Jan 1, 1950

By Frank K. McIntosh

The Hamme tungsten district is in Vance County, N. C., and Mecklenburg County, Va. Principal development has been in Vance County. The district is approximately 8 miles long by 1 mile wide and extends northeast-southwest. Its center is about 3 miles N. 65° W. of Townsville, N. C. The occurrence of tungsten in the district was first reported in 1901, but it was not until the Hamme brothers revived interest in the deposits in 1942 that commercial development began. The Bureau of Mines, as part of the war minerals program, began exploration and development of the district in June 1943 and completed it in December 1943. The Federal Geological Survey cooperated by mapping the topography and geology and logging the drill cores. The program included mapping, trenching, sampling, diamond drilling, and analyses and beneficiation of ore samples, The principal ore mineral is hubnerite, which occurs in quartz veins within the schist and granite. The veins are generally lenticular along the strike and dip. About 50 quartz veins have been noted in the area, but many are barren or slightly mineralized.

Jan 1, 1948

By J. J. Drost

This Bureau of Mines investigation studied the effect of thermal treatments upon concentratability of a western Mesabi Range nonmagnetic taconite ore and is a sequel to Bureau of Mines RI 7567. Magnetic tube tests were used to develop the data needed to calculate separation efficiency, the primary measure of concentratability. A horizontal tube furnace was employed to heat treat and reduce the hematitic ore samples. The two variables studied were roasting temperature and cooling method. The manner of cooling, either by slow cooling or quenching in water, produced no significant difference in concentratability. Roasting temperatures employed ranged from 500° to 1,000° C, and a temperature of 650° C effected the best concentratability. The temperature of 650° C correlated with the most effective roasting temperature for grindability.

Jan 1, 1973

By R. Karl Zipf, Christopher Mark

Highwall mining continues to grow in importance as a coal production method from U.S. surface mines. It may account for as much as 4% of the total U.S. coal production, according to one recent estimate. Analysis of Mine Safety and Health Administration (MSHA) accident and injury statistics shows that, overall, highwall mining has maintained an admirable safety record. Its fatality and injury rates are comparable to those for other surface mining methods, and are significantly lower than those for underground mining. No mining method is risk free, however. Highwall mining injuries have been associated with handling materials, slips and falls, machinery, powered haulage, and other types of incidents. But perhaps the greatest risk, to both personnel and equipment, is from ground control. The two most significant ground control hazards are rock falls from the highwall and equipment entrapment underground. Highwall Stability Ensuring highwall stability through proper ground control engineering is of paramount importance to safe highwall mining operations. The only fatality to occur during the last five years at a highwall mining operation was due to highwall collapse. There have also been numerous near-misses, several of which have involved extensive damage to equipment. In the central Appalachians, where the majority of highwall mining occurs in the U.S., hillseams are the most prominent geologic structures that affect highwall stability. Hillseams (or mountain cracks) are near vertical fractures in the rock that are formed in response to natural weathering and erosion of hillsides. They extend hundreds of feet down from the surface. They typically run parallel to the hillside, but they can also extend across narrow points or ridge lines. The hazard arises when rock slabs that form along the hillseams detach and fall away from the highwall face (See Figure 1). [ ] Unfortunately, it is impossible to control the location of hillseams or reliably detect their presence within a highwall. There are, however, a number of measures that can be taken to minimize the risk of failure associated with hillseams: Planning-Most operators choose to skip those areas of the highwall where a prominent hillseam daylights (See Figure 2). Existence of such areas is known for several weeks in advance of highwall mining; therefore, planning engineers can adjust the layout of highwall mining panels to locate barrier pillars within areas of questionable highwall stability. [ ] Inspection and monitoring-Daily inspection of the benches above the active highwall mining area is a prudent precautionary measure. A crack in a bench immediately above a highwall miner is shown in Figure 3. Simple displacement monitors may be useful for detecting movement along cracks that may precede a significant life-threatening failure. New tools, such as slope monitoring radar, may also prove useful in detecting motion of the rock slopes above active highwall mining operations. Good blasting practice-Most surface coal miners in the central Appalachians use pre-splitting and the familiar halfbarrels are routinely seen throughout the pits. Shorter delays along the face and longer delays between rows can direct more of the blast force parallel to the face, potentially doing less damage to the wall rock. In addition to pre-splitting, decreasing the burden, spacing and charge weight in drill holes close to the highwall will also decrease damage to the wall rock. Decreasing the highwall slope angle-Decreasing the highwall slope angle from 90° (vertical) to 70°-80°, especially in areas of known hillseam concentration, could eliminate the hillseam hazard (See Figure 4). Angled highwalls are routinely employed in many Midwestern surface mines and in some