Search Documents

By T. J. Ballard

The Tallapoosa Copper mine in Haralson County, Ga., has been operated, or under development at various times since before the Civil War. The geology of the deposit is similar to that of many of the pyrite deposits occurring in the belt of ancient crystalline and metamorphic rocks that extends diagonally northeast-southwest across the State. The Bureau of Mines, in its program of investigation of, strategic mineral deposits, diamond-drilled four holes totaling 1,570.3 feet at the deposit during the period June to September 1947 to verify the old drill records and the continuation of the deposit at depth.

Jan 1, 1948

By William H. Pomroy, Shail J. Butani

"This Bureau of Mines publication presents a statistical analysis of official U.S. Mine Safety and Health Administration (MSHA) metal and nonmetal mine fire reports from 1950 through 1984, plus accounts of selected nonreportable fires (less than 30 min and no injury) and opinion data on fire hazards from mine safety directors. Fires were analyzed by time trends, ore type, ignition source, burning substance, location in mine, equipment involved, means of detection, duration, number of injuries and fatalities, mining method, and successful extinguishing agent. The leading ignition sources were electricity in underground fires and engine heat in reported surface fires. The most frequent burning substance was combustible liquids for all nonreportable fires, reported surface fires, and reported underground fires from 1978 to 1984. For underground fires reported prior to 1978, timber was the leading burning substance. Mobile equipment was the type most frequently involved in both underground and surface fires. Underground fires occurred most often in haulageway or drift areas, and reported surface fires occurred most often in plant and mill buildings, while most nonreportable surface fires occurred in other areas. The most common methods of extinguishment were water hose lines for reported fires and dry chemical handportable extinguishers for nonreportable fires. INTRODUCTIONIn support of the Bureau of Mines research on mine fire protection, two separate baseline studies on mine fire incidents have been prepared. The first study addressed coal mine fires. The results of that study are summarized in the Bureau's Information Circular 8830, ""A Statistical Analysis of Coal Mine Fire Incidents in the United States From 1950 to 1977."" This second report, addressing metal and nonmetal mine fires, is the companion to IC 8830. Together, these two reports provide a comprehensive, factual summary of the mining industry's fire experience.This report, like IC 8830, covers (1) MSHA fire incident reports, (2) records of nonreportable fires (less than 30 min and no injury), and (3) mine safety directors' opinions on fire hazards. The MSHA fire reports provide the most reliable, objective, and accurate historcial record of the major noncoal mine fires that occurred during the study period (1950 through 1984). However, MSHA fire reports alone understate the true magnitude of the fire problem because metal and nonmetal mines have been legally required to report fires to MSHA only since 1968. Although some fires were reported prior to 1968, doubtless a great many were not. Also, the reporting regulations that took effect in 1968 specify that only fires lasting 30 min or longer or involving an injury need to be reported. MSHA fire reports are thus limited in scope by MSHA's legal authority. In order to provide a more comprehensive data base, it was also necessary to gather and analyze mine company records of nonreportable fires."

Jan 1, 1986

By D. S. Kingery

The data obtained from this study cover test areas that are gassy to ultragassy and pillared areas of different sizes and degrees of tightness. The methods of controlling ventilation, applying bleeders, and supporting bleeder entries varied in the different test areas. It was not possible to study all conditions likely to be encountered in coal mines. Undoubtedly, there are areas where bleeder entries, even though properly planned and maintained, might prove unsatisfactory. However, on the basis of this study, the following observations were made: 1. Tests showed that each bleeder system studied provided some movement of air through the pillared area; the quantities of air delivered to the pillar line, ranged from 23 to 82 percent, depending mainly on the extent to which bleeder re-turns were used as main returns from the section. 2. Pressure measurements taken across pillared areas showed maximum pressure drops ranging from 0.05 inch of water for a shallow gob to 2.69 inches for a very deep gob. The pressure differentials varied with the size and tightness of the gob but proved adequate to induce airflow across worked-out areas or through fringes of the gob to the bleeder return system.

Jan 1, 1957

By Robert D. Schmidt

This Bureau of Mines report describes the development and application of a computer model for simulating the hydrological activity associated with in situ leaching. The model is intended to provide uranium resource developers with a description of the flow behavior of leachants and ground water during the development, production, and restoration phases of a leaching operation involving an arbitrary pattern of injection and recovery wells. Different aquifer environments are modeled, using a closed-form solution to the partial differential equation that describes three-dimensional changes in piezometric head as a result of pumping from leachant injection and recovery wells. The computer program can model a maximum of, 50 arbitarily located wells. Numerical techniques involving difference quotients and Taylor expansions about time points are used to derive time, velocity, areal sweep, and fluid volume parameters associated with leaching hydraulics. These parameters are output by the program in graphic and tabular formats. Other numeric methods insure that the program running time is minimized without significantly affect-ing the accuracy of results.

Jan 1, 1980

By G. W. Reimers

Metastable pyrophoric wüstite (FexO, with x between 0.89 and 0.95) was found to be much easier to grind to colloidal state than were its stable disproportion products magnetite or iron. The grinding of polycrystalline magnetite appears to be complicated by the magnetic flocculation arising from interparticle attraction. This is superimposed on the attraction of a fluctuating electric dipole for a neighboring induced dipole. More than 85 pct of the tumbling time was saved by grinding antiferromagnetic wüstite instead of the ferrimagnetic oxide of iron (Fe304). Disproportionation of colloidal wüstite to the stable ferromagnetic and ferrimagnetic colloidal particles of alpha-iron and magnetite, respectively, was accomplished rapidly at temperatures above 250° C but below 570° C, the eutectoidal stability point of the wüstite phase.

Jan 1, 1972

By Thomas M. Barczak

he stiffness characteristics of longwall shields were investigated in this Bureau of Mines study. Since longwall strata activity is characterized by roof-to-floor and face-to-waste displacements, a model with two degrees of freedom was used to describe the load-displacement relationship of the shield structure. The model considers the support as an elastic body and relates horizontal and vertical resultant forces acting on the support to associated displacements as a function of the stiffness of the support structure. Stiffness coefficients under full canopy and base contact configurations were determined by controlled displacement loading of longwall shields in the Bureau's Mine Roof Simulator (MRS). Three two-legged longwall shields of different manufacture were investigated. The stiffness characteristics of these shields were evaluated relative to two parameters, namely, shield height and setting pressure. The test results indicate a reduction in shield stiffness for increasing height. Setting pressure was found to have less of an effect on shield stiffness, producing only a slight increase in stiffness as setting pressure increased. Similar trends were observed for all three shields, indicating a similarity in stiffness characteristics for shields of the same basic configuration.

Jan 1, 1988

By J. F. Barkley

As part of the work of serving as Chairman of Subcommittee 3, Health and Industrial Requirements, of the American Society of Mechanical Engineers' Committee on Air-Pollution Controls, the author assembled the following information on accepted maximum permissible concentrations of air pollutants from the standpoints of health, damage to vegetation, damage to property, and requirements of industrial processes. A search in technical literature was made followed by direct inquiry to all State governments as to their regulations. The subcommittee membership - G. D. Clayton, senior sanitary engineer, Public Health Service, United States Department of Health, Education, and Welfare, Detroit, Mich., Dr. L. Greenburg, commissioner; Department of Air Pollution Control, New York, N.Y., Dr. M. Katz, Defence Research Chemical Laboratories, Ottawa, Ontario, Canada, and Dr. H. H. Schrenk, research director, Industrial Hygiene Foundation of America, Inc., Mellon Institute, Pittsburgh, Pa. - reviewed the information and made very helpful comments and corrections.

Jan 1, 1954

By Edmond Chin

Mineral production was of minor importance to the country's economy, and Bangladesh was not a ranking world producer of any mineral commodity in 1980. Natural gas was the most important mineral exploited, and reserves were sufficient to allow a significant increase in its use. A greater proportion of the domestic heat and electrical energy needs could be filled by increased production and distribution of natural gas. Also, the export of natural gas was feasible either by pipeline to India or in the form of liquefied natural gas (LNG). Some nonmetallic minerals could be developed, as well as coal and peat, given sufficient capital investment. Bangladesh's strongly agricultural economy made fair progress in 1979.80.1 The major harvest of November-December 1979 turned out to be better than had been anticipated after an early drought left poor planting conditions. Secondary crops (harvested in February-March 1980 and June- July 1980) were excellent. There were prospects for a record harvest in fiscal year

Jan 1, 1982

By L. C. IlsLey

From time to time the Bureau of Mines has issued publications dealing with the various classes of explosion-proof mining machinery that have been tested and approved as permissible for use in mines having atmospheres that may become inflammable by reason of the inadvertent presence of gas or dust. These publications are confined almost entirely to description of the features contributing directly or indirectly to the prevention of explosion or shock hazards, and are intended to give inspectors, safety engineers, and others already familiar with the general safety requirements more detailed information on the safety features of the design of a particular machine. As a background for papers describing permissible machines and to avoid the necessity of duplicating descriptions of methods of conducting investigations and tests of such machinery, Bureau of Mines Bulletin 305, Inspection and Testing of Mine-Type Electrical Equipment for Permissibility, was published in 1929. Three bulletins giving detailed descriptions of the three most numerous types of machines have been issued, viz., Bulletin 313, Permissible Storage-Battery Locomotive and power Trucks. Bulletin 343, Permissible Coal-Handling Equipment. Bulletin 382, Permissible Coal-Cutting Equipment.

Jan 1, 1937

By Carla A. Kertis, Alan A. Campoli, Claude A. Goode

This Bureau of Mines study was conducted to obtain a better understanding of the coal mine bump problem and its effect on underground coal mining in the Eastern United States. To accomplish this, information was collected on the geologic conditions, mining techniques, and engineering parameters at five bump-prone mines. Two geologic conditions have been found to cause the occurrence of bumps in the Eastern United States: (1) relatively thick overburden and (2) extremely rigid strata occurring immediately above and below the mine coalbed. Additionally, the probability of bump occurrence is increased by certain mining practices that concentrate stresses during retreat mining, in areas where geologic conditions are conducive to bumps. Mining plans that permit the development of pillar line points or long roof spans that project over gob areas should be avoided because these features may contribute to the occurrence of bumps.

Jan 1, 1987

By Edward F. Courtney

Loss of life, loss of sight, crippling injuries, and property damage nearly always result from accidents involving explosives. The severity of such accidents has prompted lawmaking bodies to pass laws concerning the transportation, handling, and use of explosives; manufacturers of explosives publish manuals 'describing explosives and practical methods of handling then; and mining companies and others who use large quantities of explosives publish rules based on actual experience for the guidance of their employees. Careless storage of explosives by thoughtless or incompetent persons, particularly if they are left where children or saboteurs have access 'to them, has led to many serious accidents. Many contractors and mining operators who use explosives are extremely careless about storing them. It is the purpose of this paper to discuss the explosive-handling practices of a large western mining company, which are considered better than most.

Jan 1, 1946

By C. W. Owings

When explosions have occurred in mines where rock dust has been used to some extent, generally to a very limited extent, the press has immediately characterized those mines as "rock-dusted." To persons familiar with the method of rock-dusting, it is apparent that if rock-dusting is done properly, if all mine surfaces are rock-dusted to within at least 40 feet of the faces of rooms and entries, and if the incombustible content of the dust is more than 65 per cent, there is little likelihood that an explosion of coal-dust will occur. The report that an explosion has occurred in a "rock-dusted" mine immediately conveys to the mind of the alert safety advocate the information that the mine is inadequately rock-dusted or that either dust sampling of the rock-dusted surfaces has not been done or, if done, the mine has not been redusted with sufficient promptness. Rules for Collection of Samples Collection of dust samples is by no means intricate, but a few simple rules must be kept in mind if the results are to be dependable. A sample must represent the true average conditions of the dust in the section or zone in which it is taken, and therefore 'the point at which the sample is to be collected must be selected with care. During an explosion much if not all of the dust on the ribs, roof, timber, and road in the affected region is blown into the air; the sample, therefore, should contain all loose dust and material on: the surfaces to a depth of about 1 inch, if that amount is present. If there is considerable sand locally along the track, care must be taken not to include enough of this material to vitiate the sale and distort the results; however, if the sand is distributed throughout the region being sampled it should be included. Dust should not be collected from recesses in the ribs, such as hitches cut for timber, as the character of the dust in such places is often different from that on the ribs proper. Samples should not be collected at points where the dusting machine has been loaded or at a point where the machine has stopped and discharged for a longer period than at other points on the entry or in the rooms. In short, the sample must represent AVERAGE CONDITIONS, and if there is any doubt as to the character of the dust it is far better to have too much combustible matter than too much incombustible matter in the sample, as it is best to err on the side of safety if it is necessary to err.

Jan 1, 1929

By E. D. Wilson

This is the second of a series of progress reports describing work undertaken at the San Manuel copper mine to study the geologic factors influencing block caving of the deposit. The first report described the work done from April 1954 to March 1956.3/ This report describes the progress from March 1956 through March 1958 and presents additional maps, factural data, inferences, and conclusions resulting from a continuation of the underground geological work. As outlined in these reports, the study thus far has shown that the principal geologic factors affecting block caving are structure, rock types, alteration, mineralization, oxidation, and presence of water. Structure is fundamentally the most important. Systematic fracturing governed the extent and grade of primary ore mineralization and tangibly affects the subsidence or ground movement, which extends from the mine workings to the surface because of the block caving.

Jan 1, 1960

By Noel N. Moebs

The Bureau of Mines conducted five reconnaissance magnetometer traverses across a small abandoned chromite mine in the State Line district of Pennsylvania and Maryland to determine the geophysical response of the area. The results indicate that more extensive geophysical surveys of the region might establish some worthwhile guidelines for chromite exploration. While chromite only rarely can be detected directly by magnetic methods, there is a possibility that geophysical signatures in the adjacent host rock could provide some guidelines for further exploration. Prior to 1875, all the chromite produced in the United States came from the State Line district, and the potential for discovering additional podiform deposits could be significant. Virtually no state-of-the-art geuphysical or geochemical studies have been conducted in this district since World War II and sizable areas remain undeveloped and suitable for exploration. While the results reported in this paper are not supported by drilling, it may encourage others to investigate the area more fully for improved methods of detecting subsurface podiform chromite deposits. New theories on the emplacement of ophiolites also could contribute to an assessment of the chromite potential of the serpentinite belt.

Jan 1, 1991

By Donald P. Schlick

This report presents a representative cross section of methods successfully used to ventilate continuous-miner places as well as various factors that should be considered when selecting auxiliary ventilating equipment. Line brattice can direct fresh air to the active face reasonably well, provided that adequate area for installation is available. Continuous mining equipment, however, often restricts clearances to such an extent that proper installation of line brattice is impossible. Consequently, in many instances face ventilation is inadequate; therefore, many methods of auxiliary ventilation for continuous-mining equipment have been developed and have been discussed in this study.

Jan 1, 1963

By Michael D. Fenton

Social and political movements that had been gathering momentum over several years continued in 1993 to dramatically affect and inspire uncertainty on the global mineral industry. Privatization of government-controlled mineral industries continued throughout the world, especially in Africa, Asia, Central Eurasia, Eastern Europe, Latin America, and Western Europe. The reasons for privatization varied among regions and countries, but the trend was universal and was not expected to end soon. Regional trade blocks were being developed and expanded. The European Union (EU), the North American Free Trade Area (NAFTA), the Association of Southeast Asian Nations (ASEAN) , the Asia Pacific Economic Cooperation (APEC) , and the Latin American Southern Cone Common Market (MERCOSUR) were expected to contribute to reduced internal tariffs and increased minerals trade. Minerals consumption within the politically unstable former Soviet Union (FSU) decreased significantly without a simultaneous cutback in production, while its exports flooded the world's mineral markets. These exports into Western Europe and Japan, still in economic recession, depressed minerals and metals prices worldwide, especially for aluminum, magnesium, nickel, and potash. Increasingly restrictive environmental laws and land-access limitations in Australia, Canada, Western Europe, and the United States tended to discourage mineral resource development. However, the number of undeveloped countries in Latin America and Asia that encouraged exploration and development by revising mining and tax laws and regulations increased, thereby increasing investment opportunities for foreigners.

Jan 1, 1995

By John C. Edwards

The Bureau of Mines has developed a time-dependent mathematical model of radiative heating of bulkheads in mines. The model includes both reradiation from the duct (cylindrical) walls and direct radiation from the fire zone. Thermal loss into the wall of the duct and into the bulkhead is included. Both brick and wood bulkheads are considered. It is found that the heating rate of the system scales as the duct length-to-diameter ratio and the flame temperature. In particular, the time required for the irradiated surface of the bulkhead to reach a specified temperature decreases with increasing flame temperature for a fixed length-to-diameter ratio and increases with increasing length-to-diameter ratio for a specified flame temperature. It is also deter-mined that the time, T, for the bulkhead surface temperature to reach a specific value, Tb, for a fixed length-to-diameter ratio less than 4 and for a flame temperature of 1,200 K is approximately linearly dependent on Tb for 500 K < Tb < 700 K, and is nearly exponentially dependent on the length-to-diameter ratio for Tb = 600 and 700 K.

Jan 1, 1979

By Aarne Visnapuu

Experimental modifications have been made by the Bureau of Mines on standard pneumatic rock drills to reduce the noise of the air exhaust, drill steel resonance noise, and noise radiated by the drill body. A close-fitting case and muffler around the drill body, consisting of a metallic honeycomb skeleton filled with viscoelastic absorber on the inside and a durable outer shell, provide both exhaust and drill body noise muffling and absorption. Drill steel resonance noise is reduced by a constrained-layer treatment consisting of a tubular metal cover bonded to the ouside of the rod by a viscoelastic filler. Damping alloy components have been developed to reduce metallic resonance noise. Combined, these modifications have reduced the drilling noise level in granite from 115 dbA to 97 dbA. Data are presented on the individual and combined effects of these modifications on drilling noise and performance.

Jan 1, 1975

By J. N. Geyer

In coal mining it is essential to maintain the roof over working places and roadways in the safest condition possible. To this end every effort should be made to win the coal with the least injury to the immediate roof strata, as broken strata certainly present a greater hazard than a sound roof. The chief causes of injury to the roof in mining are inherent in the method of development and recovery and the blasting practices followed. The first, which may produce severe stresses in the roof, weakening it over comparatively large areas has been discussed in previous papers3 and will not be treated here. The second cause is local in effect, but with the same general method of blasting being employed throughout a mine having uniform roof conditions, similar effects on the roof may be expected. In the Bureau&apos;s investigation of accidents caused by falls of roof and coal it has been necessary to make a careful study of blasting practices and their effect on the immediate roof. The purpose of this paper is to show the effect of the observed methods of blasting on different types of roof and to point out methods that have been proved to be least harmful to the roof strata. The data used in preparing this paper have been compiled from reports made by Bureau engineers engaged in the study of falls of roof and coal, and embrace mines opened in the Pittsburgh coal in Ohio and Pennsylvania and the Pittsburgh and Sewickley coals in West Virginia.

Jan 1, 1933

By R. A. Beall

A series of 45 zirconium ingots has been cast by the consumable electrode arc melting process with the object of analyzing the effects of power input from 50 to 230 kilowatts and reduced pressure furnace atmosphere to improve the quality of regular 8-inch-diameter production ingots made thereby. Electrode consumption rate, molten pool volume, melting efficiency, sidewall quality, arc stability, and yield efficiency are considered. The use of direct current and alternating current is studied. In conclusion, reduced pressure furnace operation is shown to promote electrical efficiency, ingot homogeneity, high metal yield, and are stability. INTRODUCTION Zirconium is a particularly difficult metal to melt because of its affinity for atmospheric gases and its solvent properties when molten. In addition, zirconium sponge as produced by the boll process contains minor amounts of magnesium chloride, which cause severe spattering luring melting, because of these difficulties with zirconium, and its sister metal titanium, near techniques have been developed to permit production of commercial size ingots. Among the more promising is the consumable electrode arc melting method.

Jan 1, 1955