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By M. E. Tyrrell

Magnesia spinel (MgO.Al203) recovered from dusting slags in the system MgO.Al203-2Ca0.SiO2 is in the form of single crystals most of which will pass 35-mash. This investigation was undertaken by the Bureau of Mines to evaluate the concentrates as a refractory raw material. Three specific types of refractory bricks were studied: (1) dense, (2) lightweight bubble, and (3) insulating. Test specimens ware fabricated 1 by dry pressing, fired to 1,675° C., and tested by procedures common to the industry. The concentrates produced a refractor, having satisfactory density and mechanical strength; however, spinal is sensitive to thermal shock and the possibility of producing a spall-resistant brick using aggregate of such small grain-size must be considered remote. Lightweight refractorias fabricated of spinel bubbles were the most promising of the types tested. They were 30 percent lighter in sight than the dense refractory, their mechanical strength was good, and definite superiority in thermal shock resistance was indicated.

Jan 1, 1962

By John A. Davis, John Gross

This paper is one of a series giving the results of metallurgical tests conducted by: the Alaska station of the Federal Bureau of Iſines, on the recovery of gold from the black sands of placer clean-ups. The data given in this report were obtained from tests on a lot of black sand from a property located on St. Patrick Creek, Fairbanks mining district, Territory of Alaska. This property comprises the Sagan Fraction and adjoining bench claims, and is being operated by J. A. Lillie. The sand ad already been treated at the mine by amalgamation. A sample taken by Mr. Lillie and assayed at the station showed that the gold still remain ing amounted to ll cents per pound. As this gold content was sufficiently high to justify further treatment of the same, 770 pounds were shipped to the station for testing. The reader will note that the gold content is given in cents per pouni, rather than per ton. This is in conformity with practice in the district in valuing black sands, as the quantity obtained at any one time is small, much less than one ton. . The sand consisted principally of schist and quartz, with very little ilmenite and garnet; and no magnetite or sulphides. Most of the gold present as contaminated with quartz, as the free particles of gold had been removed by amalgamation at the mine.

Sep 1, 1920

By E. D. Gardner

This paper is one of a series on mining methods and costs being published by the United States Bureau of Mines. In April 19.74 the St. Joseph Lead Co., at Atlanta, Elmore County, Idaho, was mining and milling about 225 tons of gold ore daily with a total force of 150 men. The mine, which comprises the old Boise-Rochester and Monarch properties, is at an elevation of about 6,000 feet. Snow lies on the ground about 5 months each year but does net interfere greatly with local operations. However, the road to Mountain Home, the shipping point 80 miles distant, passes over a high range and usually is closed by snow from about November 15 to June 15. Heavy supplies are brought in and concentrates trucked out during the summer. In winter the district is served by a biweekly mail plane and a passenger and express plane making 4 to 6 trips weekly. Mine timber is cut locally. A plentiful supply of water is obtained from a stream brought to the property through 7,500 feet of plume.

Jan 1, 1935

This Information Circular from the National Institute for Occupational Safety and Health (NIOSH) documents and supplements the information presented in a series of workshops held during 2002 and 2003. The primary intended audience consists of all who are involved in developing and conducting miners' training. According to the Mine Safety and Health Administration (MSHA), mine operators reported 240,000 full-time equivalent workers and independent contractors reported 42,000 full-time equivalent workers working on mine property during the year 2000. Unfortunately, these workers have a relatively high risk of suffering serious work-related injuries and illnesses. The mining industry has the highest rate of occupational fatalities among all U.S. industries. The fatality rate is 30 deaths per 100,000 workers compared to 4.6 for all private industry (Morbidity and Mortality Week Report, 2001; NIOSH, 2002). Compared to workers in other industries, miners also have a relatively high rate of nonfatal lost-time injuries, and their injuries tend to be more severe (Bureau of Labor Statistics, 1999). Many miners are also exposed to significant health hazards, including coal and silica dust, diesel exhaust, and noise. More than 1000 U.S. miners die of lung disease each year (NIOSH, 1999). Mine safety and health professionals have long recognized training as a critical element of an effective safety and health program. Federal regulations (30 CFR, Parts 46 and 48) require mine operators to provide initial safety and health training to all new miners, as well as a minimum of 8 hours of refresher training each year. The time and money being spent to train U.S. miners is substantial, and so there is a strong and steady demand for new and better mine training materials and methods. A growing concern among mine safety professionals regards the training of new workers. A major change in the mining workforce is anticipated within the next decade. In major segments of mining, especially coal, relatively few workers have been hired since the 1970's. Thus, as an entire cohort of miners in the current workforce nears retirement, the replacement of these employees will require an influx of new workers. New miners may be young people who lack the ability to recognize and respond to mining hazards in an appropriate manner. They may also have had different educational experiences than their older counterparts. Many safety professionals believe that these two cohorts require different approaches to training. The papers in this report should help prepare mine trainers for the changes about to occur in the workforce and acquaint them with strategies they can use to enhance the effectiveness of their training. The first three papers present basic principles for teaching adults. The five remaining papers are intended to illustrate how these principles can be applied to the development and imple¬mentation of effective training for miners. Below is an overview of these papers. 1. Kowalski and Vaught review the process and principles of adult learning. The learning model they present includes a discussion of goals, content, delivery, assessment, and remediation. Adults are viewed as active learners, experienced-based, expert in their own right in specific areas, independent, real-life centered, task-centered, problem-centered, solution-driven, skill-seeking, self-directing, and internally and externally motivated. Basic aspects of curriculum development are briefly reviewed. For further information about adult learning, see Camm and Cullen's paper. 2. Mallett and Reinke's first paper discusses issues related to training new miners who have recently or will soon be entering the mining workforce. These new generations of miners have different learning style preferences and training needs than Baby Boomers and other older miners. Even trainers who have been highly effective in the past should reassess their training styles and their classroom materials to determine if they are prepared to meet the needs of these young new workers. This paper provides information that will help mine trainers communicate across the generation gap. 3. Mallett and Reinke's second paper provide an overview of training evaluation. Trainers and decision-makers are given a framework for planning and assessing training evaluation strategies. The authors present Kirkpatrick's (2001) model of evaluation categories and discuss how to start an evaluation plan and various ways to collect data. They do not provide detailed instruction in evaluation methodologies, but give trainers a review of the things they need to consider when developing an evaluation plan. A good evaluation plan can inform revisions to a training course, assess trainee learning, and/or answer managers' questions about program effectiveness. 4. Brnich, Derick, Mallett, and Vaught discuss a technique for incorporating worker participation into fire prevention and safe equipment operation training. This technique involves development of short (5 to 7 minutes) videotapes coupled with toolbox talks that ground the content of the videos within the context of a miner's workplace. An example of one of these training modules is presented, along with the results of an evaluation performed on its effectiveness at improving miners' understanding of what types of information they should be sure to communicate during a mine emergency. 5. Wiehagen, Conrad, Friend, and Rethi discuss on-the-job training (OJT) as a method for teaching miners safety and production skills. Much of the training is done by experienced workers. This paper describes how small investments can help improve the effectiveness of on-the-job training. Effective on-the-job training involves some structure and planning in the transfer of responsibility for task performance from the trainer to the novice. Assisting the trainer could involve helping develop up-to-date job analyses and offering strategies for teaching and evaluating job skills. This paper addresses organizational considerations supporting structured on-the-job

Jan 1, 2002

By McHenry Mosier

A skull breaker has demonstrated its advantages for secondary breaking in a limestone quarry by entirely displacing secondary blasting . It has reduced safety hazards to workmen, increased the number of quarry operating days , and has lowered mining costs by 2.7 cents a ton. It is believed that the application of the skull breaker can be made economically advantageous in the surface mining of other commoditics .

Aug 1, 1948

Predict the spontaneous combustion potential of a mining operation using an expert system computer program.

Jan 1, 1994

By A. W. Fahrenwald, W. W. Staley

"In flotation concentration, various machines are employed for agitation and aeration of the ore pulp in the operation of frothing. The power required in the operation of these machines varies considerably with the type and make of machine used. The object of this investigation was to determine the effect of certain physical properties of the pulp particularly viscosity, density, and temperature - upon the power required by certain forms of pulp agitators.The viscosity factor is most involved because it is affected by temperature and by density. Viscosity of liquids and suspensions has been extensively studied and the physics and mathematics of the subject are much enlarged upon in books and in the literature. It is not, however, the intention of this study to become involved in the intricacies of these phases of the subject.The agitation of the various mediums in the experimental work did not last long enough to cause a measurable rise in temperature from the ""beating"" of the medium, hence no cognizance is taken of this factor.No attempt has been made to correlate the data obtained with the impeller with any information regarding centrifugal pumps. The object sought here is quite foreign to the problems of pumping. The impellers used are ""open"" and air is involved.The experiments performed and the data obtained are presented. Only that amount of discussion necessary to make the results understandable is given.Tap water was used in all experiments. A comparison of distilled water and tap water showed no measurable difference. In the experiment in which sodium chloride was needed, the commercial salt as used in fire assaying was taken. The quartz was of the ""bull quartz"" variety, thoroughly washed free of iron oxide."

Jun 1, 1930

By ROBERT R. ROUGH, FRANK L. BACON, John Dasher

(being shipped as bailast in ocean freighters). Within the last 10 years it has become more economical to use local sands, and there has been a general shift from the Belgian sand. Deposits of purer sand were treated and used for 'some time: but the suprly became limited, and means were sought to beneficiate the more bountiful subpay-f impure beach sands. These sands are composed of, 50 percent feldspar and 50 percent quartz, with small amounts of iron- bearing minerals, The most objectionable impurities in these West coast sands are the oxides of iron and aluminum. The Del Monte (Calif.) beach sand contains about 0.13 percent FeqQg and about 11.0 percent Aig03 (the latter being furnished by the large amount of feldspar present.) For the manufacture of feldspar present.) For the manufacture of flint-glass containers the maximuni quantities of these two impurities permitted in the sand are 0.05 percent F20 and 6 to 8 percent A1203.. The Fe0g occurs in the sand as follows: Traces of iron-bearing minerais resistant to weathering, ferruginous clay stains on the sand grains, and iron minerais not visible and possibly in solid solution or as colloidal incisions in the grains of feidspar or quartz. A good part of the iron in the sand is present in the traces of iron-bearing minerals, biotite, ilmenite, garnet, monazite; and hornblende. Biotite is present in larger quantities than the others. Samples of quartz, were freed of iron-bearing minerais by the use of heavy liquid (sp.gr. 2.70), leached with boiling HCI and SnCl2. Under a microscope a few apparently clean quartz grains were selected, and Fe203 was determined spectrographically to be 0.03 percent. The technique is similar to that described by Gabriel and Slavin. 4/

Dec 1, 1943

By C. A. Alien

The increasing activity in oil shale has had a tendency to direct the attention of the industry to any substance from which gasoline or other oils can be secured . Cannel coal for many years has been known, as a source of oil and formerly it was the only substance from which kerosene was obtained . The name of coal oil was given to kerosene because it was derived from cannel coal before any flowing wells were brought in in the United States . In an isolated region in Southern Utah there is an unusually thick and clean bed of cannel coal which laboratory experiments indicate can be made to yield about seventy gallons of oil to the ton . This coal was first described in Bulletin 341 of the United States Geological Survey under the title of Colob coal field . This field lies at the western and southern base of the Colcb plateau and extends from the town of Cedar City southward to Kanarra and then southeastward to the town of Mount Carmel . Cedar City is 35 miles south of east from Lund on the Los Angeles and Salt Lake Railroad which is the nearest railroad point . Mount Carmel is about 90 miles south of Marysvale , on the Denver and Rio Grande Railroad , which is the nearest railroad point from the eastern end of the field . The Colob coal occurs in Lower Cretaceous rocks and a number of wagon mines have been opened on the seam in the vicinity of Cedar City , Kanarra , and Mt. Carmel , but between these places the field has been very little prospected . The cannel coal , so far as known at present , is limited to a small area on the head waters of the north fork of the Virgin River in Township 39 and 40 South , Range 9 East . In this region it occurs as a bed 5-1 /2 feet thick over which lies a layer of bituminous coal 2 feet and 5 inches thick .

Feb 1, 1921

By N. S. Dalal, X. Shi

"It has been recently suggested that the exceptionally high antitumor and antibacterial activity of natural fredericamycin A (FMA) is related to its ability to spontaneously generate the superoxide anion (02-) and hydroxyl (""OH) radicals in aerobic solutions [Hilton, B. D., Misra, R., & Zweier, J. L. (1986) Biochemistry 25, 5533]. With a view to understand the mechanistic details, attempts were made to reproduce earlier electron spin resonance (ESR) evidence for the oxygenated free radical formation in well-aerated solutions of natural FMA in dimethyl sulfoxide and dilute H 20 2• Little or no evidence was obtained for the formation of the 0 2- and methoxy (""OCH3) radicals, while the detected formation of the 'OH and methyl ('CH3) radicals was attributable largely to mechanisms not involving FMA. These results thus reopen the T question regarding the mechanism of its exceptionally high tumoricidal-bacteriocidal activity. This paper reports on an electron spin resonance (ESR) investigation of the formation of oxygenated free radicals in solutions of natural fredericamycin A (abbreviated as FMA) which has recently been reported to be a highly potent anti¬tumor antibiotic (Pandey et al., 1981; Warnick-Pickle et al., 1981). The impetus for this undertaking was provided by recent reports (Hilton et al., 1986; Stinson, 1986) suggesting that the strong tumoricidal activity with high therapeutic—toxic index of FMA was related to its ability for the spontaneous generation of superoxide anion (02-) and hydroxyl (OH) radicals. For example, the suggested mechanism for the formation of 02- by FMA was (Hilton et al., 1986)FMA-OH + O2 FMA-O + H+ + 02-Here FMA—OH is simply the FMA molecule emphasizing the —OH moiety which becomes FMA-O, the free radical rep¬resenting the oxidized form of the drug. While some other highly effective anticancer drugs in current clinical application, such as bleomycin, are also thought to exert their antitumor effects via the formation of reactive drug-based or oxygenated free radicals (Carmichael et al., 1985; Gianni et al., 1983), FMA was considered unique in that only in this case the free radical formation was thought to be spontaneous, rather than through a metal- or an enzyme-activated process (Hilton et al., 1986; Stinson, 1986). Thus it was suggested (Hilton et al., 1986; Stinson, 1986) that FMA could be the forerunner of a new class of anticancer drugs. However, we noted that while the hypothesis seemed plausible, the reported ESR spectral evidence appeared to be ambiguous. Because of the high significance of the earlier conclusions (Stinson, 1986), we undertook a systematic ESR study of the radical formation in FMA solutions, and as discussed below, our conclusions disagree with those reported earlier."

Jan 1, 1989

By H. E. Perlee

The concentration limits of flammability and autoignition temperatures of trichloroethylene in atmospheres of air, oxygen, and nitrogen tetroxide have been determined in a spherical vessel. The autoignition temperatures of TCE in atmospheres of air, oxygen, and nitrogen tetroxide were found to be 419°, 396°, and 221° C, respectively. The flammability zones of TCE-air, TCE-oxygen and TCE-nitrogen tetroxide mixtures at 100° C were found to be 10.5 to 41, 7.5 to 91, and 13.5 to 69 volume percent TCE, respectively. In addition, maxi-mum combustion pressures of 50 ps and 140 were recorded for constant volume combustion of the lower limit mixtures of trichloroethylene in air and oxygen, respectively.

Jan 1, 1966

By B. K. Cantrell, K. L. Rubow

"Two source apportionment techniques have been applied by the Bureau of Mines to aerosol measurements in diesel equipped underground noncoal mines. The first technique is based on size selective sampling and the premise that the diesel exhaust fraction of the aerosol is predominately sub-micron in size while the mineral dust fraction of the aerosol is mostly super-micron in size. The second technique, Chemical Mass Balance (CMB) modeling, was used to referee the analysis of diesel and mineral dust aerosol concentrations with the size selective method.The size distribution data were modeled using a log-normal regression to parameterize the sub- and super-micron fractions of the sampled aerosol and to estimate the mineral and diesel contributions to each. For the mines visited, analysis of the size selective: samples yielded an average value for the fraction of the fine aerosol attributable.to mineral dust of 3 pct.'The CMB analysis, applied to both fractions of the respirable mine aerosol, yielded the amount contributed to each by the diesel· and dust aerosol sources. Less than 5 pct of the sub-microm fraction was mineral dust, however, as much as 20 pct of the diesel aerosol was found: ""in the super-micron fraction requiring a correction of the sub-micron fraction to account for the missing diesel mass. More accurate measurement will require a carbon specific analysis of the aerosol."

Jan 1, 1988

By J. W. Paul

Withdrawing timber in coal mines is done for the purpose of inducing the roof to cave in the mined-out areas and thereby relieve stresses in the immediate roof material over the working places adjacent to the breakline of the roof, thus preventing the crushing of the ends of pillars and adding to the safety of those engaged in pillar extraction. A secondary purpose is the recovery of timber for further use either as prop-, crossbars, lagging, sprags or cap pieces. At some mines timber is withdrawn as a precaution against fire which may he of spontaneous origin, because wood always aids a fire of any origin. With some of the power-driven types of machines now in use a greater proportion of mine timber may be recovered, and in mines where pillars are left too narrow for their removal some of the timber in rooms might be salvaged for further use.

Jan 1, 1933

By Howard E. Parkinson, John N. Murphy

Abstract-Underground mines are typically extensive labyrinths that employ many people working over an area of many square miles; exten¬sive analysis of mine-communications systems has identified specific problem areas, in particular the excessive times required to locate key personnel underground, the inadequacy of existing phone systems in terms of capacity and privacy, and the inability to communicate with men on the move with wireless communications, as is taken for granted on the surface. A review is presented of the existing systems, the prob¬lem definition, and the various approaches that have been or are being investigated to solve these problems. Manuscript received June 8, 1977; revised August 28, 1977. The authors are with the Industrial Hazards and Communications group, Pittsburgh Mining and Safety Research Center, Bureau of Mines, U.S. Department of the Interior, Pittsburgh, PA 15213.

Aug 28, 1977

By Robert P. Vinson

The Bureau of Mines investigated the presence and extent of methane accumulations in mine roof cavities using a full-scale mine model. Methane was released at a constant rate into the roof of a cavity built onto a 700-ft wind tunnel. Two box-shaped roof cavities were used in the study: one had a volume of 114.7 cu ft; and the other had a volume of 57.3 cu ft. Methane concentration was measured at 28 sampling points in the cavities using 21 different combinations of gas emission rates and air velocities. Brattice hung in the cavity helped reduce methane concentrations without auxiliary ventilation. It was also found that the effective ventilation rate increased by a factor of 40 in the large cavity and by a factor of 20 in the small cavity when air velocity was increased from 100 to 600 fpm.

Jan 1, 1978

By John W. Finch

The present epoch in human history has been variously described as the age of coal, of oil, of iron and steel, and of power. All agree, however, that it is a great industrial period. Power is of course the vital force in the industrial organism; but power is derived chiefly from mineral fuels or from harnessed and controlled water - also a mineral substance although usually not so classified by industry. However, the latent energy of fuels cannot work for men until it is changed to active energy by combustion and until this active energy is converted into motion. This motion is just as indispensible as the energy itself. Likewise, the latent energy of water cannot be utilized until it, too, is converted into motion; out the mechanisms and devices for converting latent energy into motion, as well as the structures in which they are operated, would not be possible without metals and other minerals. Consequently, minerals are fundamental in industrial civilization.

Jan 1, 1938

By E. P. Youngman

The mining laws of Russia (Collection of Laws, vol. 7, 1912) are still in force in Latvia. The Free State of Latvia (declared independent on November 8, 1918) is composed chiefly of the Baltic Provinces of the former Russian Empire, which are ethnographically Lettish: The Province of Courland, four districts of the Province of Livonia, and three districts of the Province of Vitebsk. Since the establishment of its independence, Latvia has not felt the need of a special mining law, inasmuch as mining so far has not been found profitable in that country. A supplement to this paper, entitled "Mineral Resources," is a brief summary of the minerals found and utilized in latvia. RIGHTS OF FOREIGNERS A foreign individual is permitted to explore for minerals and to own and operate mines in Latvia on equal terms with Latvians. A foreign corporation is required to establish a branch in Latvia, which shall be subject to the corporation laws of the country. A certain number of the partners or incorporators must be citizens of Latvia.

Nov 1, 1931

By O. C. Ralston

The Bureau of Mines has under development on a technical scale an electrolytic process for treating oxidized ores of zinc , using caustic soda as an electrolyte . Whereas the Bureau process can alternately make either solid zinc or zinc dust , the following paper , from the Ludwigshafen research laboratory of the well -known I. G. Farbenindustrie , A. G. , of Germany, deals only with production of zinc dust from sodium zincate solutions and may well serve as introduction to the subject for American metallurgists . The Bureau of Mines pioneered in the idea ; a study on laboratory scale by H. J. Morgan and 0. C. Ralston was made early in the First World War, and published in Transactions of the American Electrochemical Society . The Eckardt paper , translation of which follows , goes more thoroughly into the preparation of electrolytic zinc dust , and later publications of the Bureau of Mines will deal with broader details and application of the idea to treatment of lowgrade ores and metallurgical intermediates , which is the point where Eckardt left off . 4 The Eckardt report became available through operations of Field Information Agency , Technical ( FIAT ) of the Office of Military Government for Germany (US ) , which made bibliofilm copies of the files of internal technical reports of many of the German industrial establishments , Eckardt's report is dated April 1939 and was taken on FIAT Microfilm Reel MM 106 , frames 82-101 , which is on file as Publication Board Document 41411 in Office of Technical Services of the U. S. Department of Commerce , Washington , D, C , Eckardt points out that the normal source of zinc dust is the blue powder of the zinc retorts , which decreases in volume every year owing to technologic improvements in zinc smelting. I. G. saw the importance of making a

May 1, 1948

By George S. Rice, W. L. EGY, H. P. Greenwald, L. M. JONES

CHAPTER I. INTRODUCTION AND SUMMARY. BY GEORGE S. RICE. PREFATORY STATEMENT. This bulletin describes the second series of coal-dust explosion tests conducted by the Bureau of Mines in the experimental mine near Bruceton, Pa. It covers a period from 1913 to 1918, inclusive, of more or less consecutive testing, during which many important conclusions were drawn regarding the way a coal-dust explosion may originate, the mechanism of an explosion, and the methods of pre- venting explosions and of limiting incipient explosions. The manuscript was prepared in 1918, but its publication had to be put aside during the World War for more pressing publications and it was not until this fiscal year 1922 that funds could be allotted for its printing. Meantime the general facts concerning methods of preventing explosions have been made known to the mining industry, with great advantage, it is believed, as explosions of coal dust in mines in the United States have become infrequent. This fact, however, must not lull the consciousness of mining men to the terrible potential danger that lurks in untreated coal dust. The experiments described in this volume should be of aid to them in planning to keep the ever present coal dust in an innocuous condition. The first series-reported in Bulletin 56, "First Series of Coal-Dust Explosion Tests in the Experimental Mine"-included only pre- liminary tests of the ability to start explosions of coal dust under the conditions in the experimental mine. After this fact had been determined and several violent dust explosions had been demon- strated before large audiences of mining men, the work had to be suspended in order that necessary repairs and extensions might be made in the fall and winter of 1911-12. Although the question of the possibility of coal dust causing explo- sions had been considered for more than a century, and much testing in laboratory apparatus and in small surface galleries had been done, coal-mining men generally did not believe that coal dust was explo- sive and considered that fire damp or gases of unknown composition were responsible for the mine explosions that had cost thousands of lives in the various coal-mining countries during the last century. As coal mines increased in number, size, and depth, explosions became alarming in their frequency. Finally came the Courriéres disaster in northern France, 1906, by which 1,100 lives were lost, and the following year in this country, the Monongah mine explosion, in West Virginia, which killed 361 men, and the Darr explosion, in Pennsylvania, which killed 239 men. These two disasters, both in December, 1907, led Congress to make an appropriation for an in- vestigation of the causes of mine explosions. The funds became available July 1, 1908, and the work was placed under the United States Geological Survey's technologic branch, with the late Dr. Joseph A. Holmes in charge. Before undertaking the investigations Dr. Holmes visited Europe, accompanied by the senior author of this bulletin, to study the methods foreign countries used to prevent mine explosions, to obtain details regarding tests being made in several countries, to procure safer explosives and better safety lamps for use in gaseous and dusty mines, and to study the methods used in coal-dust explo- sion tests in the recently completed galleries at Altofts, England, and Liévin, France, and in the older galleries at Gelsenkirchen, Germany, and Frameries, Belgium. At all of these stations the explosions tests were made in surface galleries. The Austrian gallery at Segengottes, near Brünn, Moravia, visited by the writer in 1911, is an underground gallery, but the testing done in it was limited, dealing with ignition of coal dust rather than with propagation. Although the results obtained in the foreign galleries had indicated that coal dust was explosive, mining men in the respective countries were of the opinion that the dust would not explode under mine con- ditions. This situation led Dr. Holmes to the conclusion that testing must be done in a real mine, to make certain that the conclusion would be reliable and would be accepted by the mining public as decisive.

Jan 1, 1922

By Robert P. Vinson, Kissell. Fred N., Edward D. Thimons

"The Bureau of Mines investigated the presence and extent of methane accumulations in mine roof cavities using a full-scale mine model. Methane was released at a constant rate into the roof of a cavity built onto a 700-ft wind tunnel. Two box-shaped roof cavities were used in the study: one had a volume of 114.7 cu ft; and the other had a volume of 57.3 cu ft. Methane concentration was measured at 28 sampling points in the cavities using 21 different combinations of gas emission rates and air velocities. Brattice hung in the cavity helped reduce methane concentrations without auxiliary ventilation. It was also found that the effective ventilation rate increased by a factor of 40 in the large cavity and by a factor of 20 in the small cavity when air velocity was increased from 100 to 600 fpm.INTRODUCTIONAny location in a coal mine where 5 pct or more of methane is present constitutes a potential site for an explosion and roof cavities are likely locations. Unfortunately, little is known about the buildup of methane in roof cavities. Some research has been done using scale models where no air flows past the cavity so that methane disperses only by diffusion (5) 4 a rare situation in mines.No known cavity-model investigations have been made that simulate air and methane flow conditions normally encountered underground. These Bureau of Mines studies were undertaken to determine the extent and manner of methane buildups in coal mine roof cavities with air velocities in the range normally found in coal mines and with various methane emission rates."

Jan 1, 1978