Search Documents

By L. J. Prosser, G. Esterhuizen, A. T. Iannacchione

The potential for roof fails in underground mines remains a clear and present danger for mine workers An investigation of ground conditions in nearly 50 percent of the nation’s underground stone mines fold that the slate of roof stability is primarily determined in a limited and subjective manner. These large-opening mines with roof heights typically 7 m (23 ft) or more, make physical observation difficult. Although some mines use monitoring techniques to gain additional information an roof stability, this practice is usually short term and localized to address ground conditions in a particular section or part of the mine. A roof-fall hazard-assessment techniques was development based on engineering judgment acquired from extensive underground stone mine experience and on exanimation of the related literature. This technique utilizes observational processes to determine roof fall likelihood Case-study scenarios offer a realistic picture of model implementation. Providing the mine level decision-maker with an accurate assessment tool to ascertain the level of ground fall hazards is expected to reduce mint worker injuries and fatalities Moreover; the presences of danger can be overcome with a clear picture of quantified ground conditions.

By C. D. Litton

Submicrometer particle concentrations and average particle sizes were monitored for four full-scale sealed coal fires in the multiple-entry section of the Bruceton Experimental Mine. The data from these tests indicate that there exists a very good correlation between the submicrometer particle concentrations and the maximum temperatures measured within the coalbed. As the maximum coalbed temperature decreases with time after sealing, the submicrometer particle concentrations show a corresponding reduction. This particle-temperature correlation is in sharp contrast to the gas concentration data obtained, for which essentially no correlation exists with the measured coal-bed temperatures. The results of these full-scale tests indicate that the measurement of submicrometer particle concentrations may be a more realistic approach to determining the status of underground sealed fire areas.

Jan 1, 1981

By J. M. Singer

Approximate equations were used to compute the radiant heating of float coal dust by approaching flames for various combinations of particle size, dust path length (flame travel distance), flame temperature, dust concentration, flame speed, and flame length. The computed values of degree of radiant heating and flame travel distance for preheating the coal dust should be useful for estimating the increased fire hazard of different coal dust-flame parameters. Some findings relating to coal mine disaster control are-- 1. Coal dust clouds cannot be preheated to ignition temperatures by flame radiation alone when deflagration speeds are greater than about 10 m/sec. Thus it appears unlikely that radiation alone will cause flames propagating in dust clouds to accelerate to detonation velocities. 2. Small particles in the radiation flame zone caused by burnout and soot formation increase the degree of preheat significantly. 3. The concentration of float coal dust (radii = 3 to 40 microns) for maximum radiant heating usually peaks in the range 50 to 200 mg/liter of air.

Jan 1, 1970

By Dennis Dolinar, Christopher Mark, Gregory M. Molinda

In 1999, 2,087 unplanned roof falls were reported from 841 mines. Nearly 55% of all mines reported at least one roof fall, and nearly 17% of the mines reported five or more falls. In order to investigate the variables that contribute to roof falls, the National Institute for Occupational Safety and Health (NIOSH) compiled a national database of roof performance from 37 coal mines. Geotechnical factors and their effect on roof fall rates were compiled from over 1,500 miles of drivage. The factor that is the best predictor of roof fall rate is the Coal Mine Roof Rating (CMRR). For a low CMRR (#30), almost all cases have high roof fall rates. Conversely, high roof fall rates are rare for strong roof rocks (CMRR $ 60). Roof fall rates were also higher in deeper mines, probably because of greater stresses. Intersections were much more likely to fall than roadways, and four-way intersections were more prone to fall than three-way intersections. In a controlled comparison of the effect of increasing bolt length on roof fall rates, it was found that longer bolts reduced the roof fall rates in 11 of 13 cases. A relationship between the roof fall rate, the intersection span, and the CMRR was also found. Finally, a systematic method for tracking roof performance and geotechnical variables was demonstrated.

Jan 10, 2000

By D. Cummins

This Information Circular presents a brief history of the lead-acid battery and describes ways to prevent serious injury from battery explosions when servicing and charging lead-acid batteries, particularly in the surface mining industry. The Mining Safety and Health Administration (MSHA), U.S. Consumer Product Safety Commission, battery manufacturers, and the mining industry have all contributed information as well as recommendations for injury-free handling for this report.

Jan 1, 1980

By C. A. Wilson

The Bureau of Mines started a continuing program to investigate and evaluate analytical techniques to assist governmental agencies to select simple, rapid, reliable methods for crude oil spill identification. Six crude oil samples were analyzed to evaluate gas-liquid chromatography, atomic absorption spectrophotometry, infrared spectoscopy, sulfur and nitrogren determinations, mass spectrometry, nuclear magnetic resonance spectroscopy, and ultraviolet spectrophotometry. Samples were studied from the following selected fields: El Morgan, Egypt; Duri, Indonesia; Minagish, Kuwait; Bachaquero, Venezuela; Gach Saran, Iran; and Prudhoe Bay, Alaska. These samples were chosen to represent high-production fields that are likely to be involved in oceanic transport. Over 50 years of Bureau of Mines analytical research on petroleum served as the basis for evaluation of the experimental results to determine which of the methods are effective techniques to identify crude oil spills. Gas-liquid chromatographic analysis, atomic absorption spectrophotometric analysis, and sulfur-nitrogen determinations are recommended as the most useful of the techniques investigated.

Jan 1, 1975

By Kevin Connor

During 1984, minerals exploited in Burundi included gold, kaolin, lime, and peat. Over 1,100 troy ounces of gold was extracted and traded during the year as a result of the lifting of the Government ban on gold mining in mid-1983 and the establishment of an artisan mining program and licensed trading counters. Almost 2,000 tons of kaolin was mined for the manufacture of insecticides. Lime production was for domestic fertilizer applications. Amoco International and the Government signed an accord late in the year for a petroleum exploration program covering 600,000 acres of Burundi's onshore Ruzizi Plain and part of northeastern Lake Tanganyika. Amoco was expected to begin the exploration program by mid-1985. Anticipated program costs could run as high as $200 million.2 The Finnish company Ekono Oy completed its peat industrial energy development studies for the Buyongwe peat deposits of northern Burundi by the end of the year. The project assessed the quantity and fuel quality of 13,000 hectares of peatland and was part of a larger study for developing the Musangati lateritic nickel deposits of Burundi, estimated at 3% of the world's reserves of nickel. The Buyongwe peat would fuel dryers and an electrical generating plant for supplying power to nickel ore processing facilities. Briquetted peat would also be used as a substitute for wood and charcoal, presently the main sources of rural energy in the country and rapidly depleting because of deforestation. The study also evaluated the most economical methods to harvest the peat bogs. The study was financed by the International Development Association (IDA), United Nations Development Program (UNDP), Finnish Aid-Finnida, and the Burundi Government.

Jan 1, 1986

By William R. Sharp

This Bureau of Mines report details a technique for aiding the engineer with the long-range design of an underground mine. The method is based upon the assumption that sufficient data are available to assign numeric values to some finite number of mineralized blocks; assignment of numerical values is problem dependent. By assigning appropriate weighting schemes, the algorithm developed in this report may be used to solve the optimal end-of-life underground mine layout, design least-cost electrical layout networks and efficient material handling networks, find least risk escape routes in the event of an accident, etc. The method is based upon the assumption that sufficient cost and geologic data is available to build a detailed mineral block inventory of the mineral deposit. It is further assumed that the cost assigned to any minable unit is independent of the neighboring blocks. The basic approach relies upon concepts and ideas from the theory of networks. To make the approach user oriented, a computer program is included and discussed. The computer code is written for an orthogonal, three-dimensional set of blocks. Computational costs and experience indicate that the program could be of great benefit in evaluating large complex mineral properties from the viewpoint of predesigning an underground mine layout.

Jan 1, 1974

By Harry Dobroski, Larry G. Stolarczyk

A medium-frequency (MF) communication system has been built and has been tested in underground mines. It provides radio coverage to vehicles and personnel anywhere in the mine via parasitic coupling into existing mine conductors. The system consists of base stations, repeaters, and vehicular and personnel transceivers. Air-core antennas for vehicles and clamp-on antennas for base stations and repeaters were designed for maximum coupling efficiency using existing mine wiring. Personnel transceivers are of a unique vest design that features a low physical profile, good user comfort, and efficient antenna design. In-mine tests show impressive results. Range between rubber-tired vehicles and base stations is often measured in miles. With repeaters, greater range is possible.

By Paul T. Allsman

This paper gives the cost and describes the mining of 55 tons of nickel-bearing rock by hand methods from a prospect in southern Nevada, June 15, 1937, by the Mining Division of the Bureau of Mines. The geology, mineralogy, and problems related to future development also are discussed briefly. The main object was to obtain a 55-ton sample within the limited period during which funds were available; little time was available to make a first-hand detailed study of the possibility of commercial ore deposits being found. The sample was desired by the Metallurgical Division of the Bureau for experimental purposes at the Electro-Metallurgical Station at Boulder City, Nev. The term "ore" is used loosely in the following discussion to designate dike material containing nickel and copper, without consideration of its commercial value. ACKNOLEDGMENTS Material concerning the geology and mineralogy of the prospect and district as obtained from Geological Survey publications by Bancroft3/and Longwell4/.

Jan 1, 1938

By Larry G. Stolarczyk

This report deals with the creation of an efficient method to determine if command, control, communication and monitoring (3cm) equipment in coal, metal and non-metal mines is susceptible to Radio Frequency Interference (RFI) from the Medium Frequency (MF) radio communications system. A qualitative and quantitative RFT test plan was developed for in-mine and laboratory evaluation of the equipment. The laboratory testing was accomplished using the TEM Test Chamber. Detailed information on the Test Plan and the TEM Test Chamber is included. During in-mine testing of the MF System some underground equipment malfunctioned when the transmitter's radiating antenna was in close proximity. Electromagnetic Compatibility (EMC) testing was done on three levels; Component (circuit or box), subsystems and system. Nine tables are included which show the results of testing various equipment for RFI.

Jan 5, 1986

By Garrett R. Hyde

Sintered yttria and sintered dysprosia can be used to make single-component thermistors having typical thermistor geometries and operable in the temperature range 500° to 1,200° C. However, at these temperatures, instability of platinum electrodes can contribute a slight aging effect if the thermistor is kept near 1,200° C for long periods. Typical characteristics at 500° C for an yttria disk thermistor 12 mm in diameter and 2 mm thick are a resistance of 12.4 megohms and a temperature coefficient of resistance of -3.8 percent per degree C. Typical characteristics at 500° C for a dysprosia thermistor of the same dimensions are a resistance of 1.84 kohms and a temperature coefficient of resistance of -1.6 percent per degree C.

Jan 1, 1970

The Bahamas Oil Refining Co. (BORCO) refinery in Freeport continued to operate at less than half its full 500,000-barrel-per-day capacity. Although owned through subsidiaries by the Carey Energy Corp (65%) and Standard Oil Co. of California (35%), BORCO is ineligible for participation in the Crude Oil Entitlements Program granted to companies operating within the United States proper or its territories. Like some other Caribbean refineries, BORCO has suffered a loss of normal market outlet due to the wt advantage afforded U.S. refineries by the Entitlements Program. Saudi Arabia, Nigeria, and Libya are the major suppliers of crude for the refinery. Its principal products, motor spirits, aviation fuel, distillate fuels, and residual fuel oils, were marketed in the United States and Puerto Rim. The Government-owned Bahamas Development Corp. and Burmah Oil Co. Ltd., held discussions pertaining to a renegotiation of Burmah Oil's management contract for the Grand Bahama Oil Transshipment terminal. The desired contract modifications were not made public but financial problems have plagued the terminal and its operation since construction started in 1972.

Jan 1, 1981

In the interest of safety in metal mining, the Bureau of Mines recommends: That underground metal mines be equipped with a main fan in a fireproof housing, located preferably on the surface. The fan installation should be designed to ventilate the mine adequately throughout and to permit prompt reversal of direction of air flow. Many metal mines depend for ventilation upon natural flow of air, assisted by the exhaust from pneumatic drills and by compressed air blown into the workings. Others also ventilate separate headings or sections with fans and blowers. Relatively few have o mechanical ventilating system that controls the coursing of air throughout the mine.

Jan 1, 1939

By David Hoadley, Kenneth R. Maser, Ashok B. Boghani, James E. Billar, D. Randolph Berry, Mackenzie Burnett, Robert H. Trent

8. Refuge Chambers 8.1 Refuge Chambers - Technical Discussion 8.1.1 Introduction As a part of the overall escape system, refuge chambers can provide a last resort when existing escapeways are blocked. These chambers are intended to provide both protection from toxic gases and a life supporting environment for a period of time before external rescue or further escape efforts can be carried out Escapeways may be blocked physically (due to cave-ins, etc), by fire, or by the presence of a toxic or oxygen deficient atmosphere. In the first two cases, the trapped miners would most likely await external rescue efforts, and hence the design of the chamber will have to consider the time durations that such efforts may take, It is also possible, in the second case, for fire fighting and fire protective equipment to be stored in the chamber so that miners may attempt their own escape. In the third case, it should be recognized that a compact, beltmounted 1-hour self-contained breathing apparatus has been developed(9), and that other, less compact equipment is available for up to 4 hours of self-contained breathing supply. If such equipment were stored in the chambers, then miners could escape by travelling from chamber to chamber, taking temporary refuge in each before proceeding to the next. 8.1.2 Background The concept of "barricading" has long been recommended for those emergencies where miners are trapped inby a fire. Barricading, which is the construction of a makeshift shelter in a crosscut or deadend, protects the entrapped miners from toxic gases and enables them to conserve a supply of air. In this manner, they can survive two or three days--hopefully enough time for them to be reached by rescue teams. In the past, many lives have been saved with this technique.

Jan 1, 1976

By Suzann C. Ambrosio

Crude petroleum, the only commercially exploited mineral resource in Cameroon, continued to dominate developments in the mineral industry sector. International mining concerns have expressed interest in developing Cameroon's bauxite and iron and steel potentials. Domestically, the mineral industry focused on production of fertilisers for agricultural development, infrastructure construction, and hydrocarbon development, through the nearly self-sufficient production of fertilizer materials, cement, and crude oil. The mineral sector contributed 5.6% to the estimated 1981 gross domestic product (GDP) of $6.5 billion.2 Petroleum exports accounted for approximately 4.5% of the 1981 GDP and exceeded coffee and cocoa exports for the second consecutive year. The trade gap widened during the fiscal year ending on July 80, 1981, owing to a 21% increase in exports and a 25% increase in imports. Offsetting these balance-of-payments difficulties, typical of developing countries' early economic stages, were increases in foreign exchange reserves to $71 trillion by May 1983.

Jan 1, 1983

By Robert E. Johnson

THE MILDEST recession of the postwar period ended in the first months of 1961, and the economy climbed steadily during the remainder of the year. The Federal Reserve Board (FRB) Index of Industrial Production climbed from a low point of 102 (1957=100) in February to 115 in December, a rise of 12.5 percent. But economic activity for the year as a whole was only 1.5 percent higher than the 1960 level, as measured by real gross national product (GNP). Although activity increased throughout 1961, much of it was merely regaining ground lost in the decline during the second half of 1960 and the first months of 1961. The FRB index did not re ain the July 1960 high of 110 until June of 1961. Mineral fuels did not fully share in the economic recovery. The (FRB) crude oil and natural gas index rose only 5 percent between February and December. Although the index of monthly coal production increased 11.5 percent during the year, the February level was so low that total production for the year was the lowest since 1954. Total production of energy measured in Btu's was up slightly (1 percent) during the ear. Coal production was down; production of crude oil and natural gas was up. Calculated consumption paralleled production-total up slightly, coal lower, and crude oil and natural gas higher. The most interesting product developments were in coke and residual fuel oil. Sales of coke showed a sharper drop than steel

Jan 1, 1962

By James R. Coldwell

Mining and processing cost analyses were conducted by the U.S. Bureau of Mines on stratiform zinc-lead-silver, coal, and stratiform barite deposit types that are found in the Colville Mining District. Reserves and gross revenues which would allow these deposits to be minable were modeled. A 15% Discounted cash-flow rate-of-return economic threshold was selected as the minimum acceptable return on investment for the three deposit types. The economic modeling indicated combinations of grades and tonnages for stratiform sulfide deposits that could be economically viable for orebodies ranging in size from 25 to 130 million metric tons. The gross revenues for a surface mine range from $200/mt for a 5,000 mtpd operation using the proposed South corridor to $140/mt for a 17,000 mtpd mine using the proposed North corridor. The economic modeling indicated underground coal mining was subeconomic for deposits ranging in size from 42 to 250 million metric tons. The required gross revenues ranged from $300/mt for a 2,200 mtpd mine to $21 D/mt for a 13,000 mtpd mine. The economic modeling indicated supplying projected in-state barite demand was subeconomic for the three seasonal surface mines modeled. The required gross revenues ranged from $600/mt for a 90,000 mtpy mine to $840/mt for a 6,000 mtpy mine.

Jan 1, 1995

By E. D. Gardner

"The Bureau of Mines has studied blasting practices in metal mines of the Southwest. The investigation of blasting drift rounds showed among other results, that cut-holes in ground difficult to break could be chambered to advantage under some conditions.In open--cut mines, chambering nearly all holes before blasting is the common practice. Two or more free faces are generally maintained in this type of work, and the amount of explosive necessary to break any bench or bank can usually be estimated from the yardage to be moved. However, in blasting drift or tunnel rounds only one free face is available before the cut-holes are shot, and the quantity of explosive required is generally ascertained best by trial.In addition to being the most difficult to break, the cut-holes are the most important of a drift round. When the cut-holes ""break bottom"" less work is required of the other holes, and a full break of the round is generally obtained. In ground difficult to blast, extra care and expense are justified to insure that the cut-holes ""break bottom.""At many mines the work is so organized that all blasting is done at the end of the shift, and a decided advantage would have to be gained to make chambering of the cut-holes economical. Also, in many mines blasting during the shift would not be practical. One or two holes could probably be drilled during the time necessary to do the chambering. However, under certain special conditions, such as in small operations or those where ""leasers"" or contractors are working, drill holes could be chambered should there be an advantage in doing so. Moreover, in some mines it might be practical to chamber the cut-holes at the lunch hour. In ordinary rounds the cut-holes are generally drilled by noon. It would not be necessary to tear down the drill or remove tools from the face to do this work of chambering."

Feb 1, 1928

By E. K. Kleespies

The Bureau of Mines determined the kinetics of the reaction of titanium-iron alloys with titanium trichloride dissolved in sodium chloride to provide a basis for understanding the reactions occurring in metallurgical processes involving reduction of the metal halides or alloy refining in fused salts. The rate of the heterogeneous reaction was determined between titanium-iron alloys and titanium trichloride to elucidate the effects of alloy composition on the rate. Measurements were made in an inert atmosphere with a high-temperature thermobalance using high-purity reactants. The rates of the reactions were about 1 x 10-5 g Ti/cm2-sec, and the reaction was phase-boundary controlled. Titanium alloys of the body-centered cubic beta structure reacted faster than those with the hexagonal close-packed alpha structure. The inter-metallic compound, TiFe, reacted very slowly, whereas TiFe2 was inert. Alloys containing above 89 atomic percent iron gained weight by reacting with titanium species in the salt solution and depositing titanium in the alloy. The effect of TiCl3 concentration on the reaction rate was determined from 2 to 12 weight-percent TiC13 and at various alloy compositions. At high iron contents, above 50 atomic percent, the TiC13 concentration effect was small. At lower iron contents, the TiC13 concentration effect was greater for beta-crystalline alloys than for alpha-crystalline alloys. The temperature dependence of the reaction between titanium alloy containing 8.7 atomic percent iron and titanium trichloride was measured over the temperature range 1,062° to 1,220° K, and the energy of activation was 7.7 kilocalories for the reaction.

Jan 1, 1967