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By A. J. Barry

[This is the third report related to fundamental retail roof-bolting research in underground mines (1, 2)3/ and describes an investigation of the torque-load relationship for 3/ -inch, expansion-type mine roof bolts. In a previous investigation the relationship between torque and bolt load was established for 1-inch slotted-type bolts (1). The two types of bolts differ in diameter and method of tightening and consequently may exhibit different torque-load behavior. The 1-inch bolt is tightened by turning the nut, the 3/4-inch bolt by rotating the beaded bolt itself. Experience indicates that roof bolts should be tightened to moors satisfactory anchorage sand to minimise nag of tie roof over the mine opening. The generally accepted means for determining the bolt load is to see a torque wrench to measure he torque applied in tightening the bolt and, from a predetermined relationship between torque and molt load, to, determine the corresponding bolt load. Because frictional effects may vary between one type of shell assembly or bolt and others, 7 types of expansion shell units and 3 types of 3/4-inch-diameter, mild steel bolts were tested.]

Jan 1, 1954

By James P. Ulery, Jon C. Volkwein

The U.S. Bureau of Mines investigated a method of using inert gas to prevent the formation of explosive gas mixtures in auger highwall mining of coal. A combination of gasoline and diesel engine exhaust gases was introduced into the auger drill hole using a short section of pipe located at the collar. Gas samples were taken and analyzed on-site with infrared detectors for oxygen, carbon dioxide, methane, and carbon monoxide. Evacuated bottle samples were also taken and analyzed by gas chromatography in the laboratory. These gas results were analyzed for explosibility. Coal samples from various depths were used to obtain the gas content of the coal using the modified direct method. Personal expo- sure to carbon monoxide was also monitored. The highest methane level observed was 9.55%. The levels of inert gas (carbon dioxide and nitrogen) were sufficiently high to prevent any ignition of the methane. Results showed that for all conditions during mining, gas concentrations were nonexplosive. The gas content of the coal was about 0.30 cm3/g. The maximum personal time-weighted average sample for carbon monoxide was 20 ppm. This system provides a safe, inexpensive, simple method for pre- venting explosions during auger mining.

Jan 1, 1993

By Basil Dimitriades

The association of automotive fuel composition with exhaust reactivity was studied in an experimental program that involved testing with different automotive engines and with gasolines of varied composition. Results showed clearly the exhaust reactivity to increase with increasing levels of polyalkylbenzenes in the fuel. No other systematic patterns of high significance were detected in the association of exhaust reactivity with several broadly defined groups of fuel components. For the purposes of this study, had it been possible, fuel composition should have been defined and expressed in terms of component groups such that the potential for exhaust reactivity would be the same within each group and different from group to group. Classification of fuel components in terms of the paraffins-olefins-aromatics groups does not meet the latter requirements. For appropriate classification of fuel components more information is needed on the combustion .of hydrocarbons in the multicylinder internal combustion engine. Statistical analysis of the mass emissions data showed significant car and fuel effects on hydrocarbon, carbon monoxide, nitric oxide, total aldehydes, and formaldehyde emission levels and on total photochemical reactivity. Car-fuel interactions were not significant at the 90-pct level. Correlations were found between mass emission parameters and fuel composition.

Jan 1, 1973

By Thomas C. Miller, Charles E. Mongan

"This publication is a progress report on Bureau of Mines studies in applying sonar techniques to roof-control problems in coal mines. Preliminary tests in the laboratory were made on layers of roof rock. To apply the experience thus obtained, a unit was designed and constructed and was used underground.The term ""sonar technique"" refers to the system of generating a beam of sound waves, shaping and directing the beam, introducing the beam into a medium to be studied, and examining any returning waves with a view of inferring the nature of the material traversed by the waves and the presence of interfaces or obstacles in the medium.The theory and actual underground experiments indicate that the sonic method is feasible. Information from physical tests made in the Bureau's Experimental mine confirmed the validity and potential usefulness of the sonar method. Lighter and more compact apparatus is desirable, and permissible equipment suitable for use in gassy or dusty mines must be developed. However, no particular difficulties are anticipated; consequently, this scientific approach to the exploration of roof strata shows definite promise. INTRODUCTIONThe problem of roof control in the coal-mining industry is of major importance. More than 50 percent of all coal-mine fatalities and 25 percent of all nonfatal serious injuries are caused by falls of roof, face, or ribs. The Bureau estimates that more than $128 million was spent by the coal-mining industry in 1958 for supporting roof."

Feb 1, 1960

By A. C. Fieldner

The Bureau of Mines has recently conducted a study of results obtained in analyzing similar samples of coal and coke by 25 laboratories throughout then country, in comparison with results obtained in the Bureau's coal laboratory at Pittsburgh. The purpose of this work was primarily to obtain a comparison of the methods of coal analysis used by the laboratories of the American Gas Association. Therefore, four standard samples of coal end one of coke ware prepared in the Bureau of Mines coal laboratory at Pittsburgh, and portions sent to each laboratory. At the same time, a like number of standard samples were submitted to 12 commercial laboratories rot affiliated with the Association, for the purpose of comparing their analyses with the results is obtained by the U. S. Bureau of Mines and the American Gas Association. Tire comparison is based on the average of 24 analyses by the Bureau of Mines on each kind of coal, and the accompanying curves show the deviation from this average analysis, together with deviations from the check limits of the American Society for Testing Materials.

Jan 1, 1923

By R. D. Currie

The practicability and dependability of two permissible methane-indicat- in detectors recently developed were proved conclusively by extensive tests in the return airways of all mines operating in the anthracite region in most of which samples and readings were taken with one or the other of the two in- dicating detectors. These detectors roved dependable and accurate within practical limits, and their general use should be encouraged as an aid to bet ter ventilation, more accurate control of air currents, and greater safety in mines.

Feb 1, 1936

By Walter W. Fisher

Cement copper was flash roasted in a vertical tube furnace to convert the copper to acid-soluble oxides as part of a postulated process for refining cement copper by oxidation roasting, acid leaching, and electrowinning. The results of the study showed that the oxidation was a linear function of oxygen concentration between 0 and 20 percent, but above 20 percent oxygen there was no further increase in oxidation. Therefore, air was the optimum oxidizing atmosphere in this flash roasting system. The oxidation followed a parabolic rate law as the roasting temperature was increased from 400° to 800° C. Extrapolation of the data, based on the parabolic law, indicated that at 400°, 500°,600°,700°, and 800° C, the roasting times required for complete conversion to soluble oxides were 75, 37, 21, 7.7, and 4.6 seconds, respectively. Cyclic-roasting test results did not substantiate the predictions obtained through data extrapolation.

Jan 1, 1973

By D. W. Frommer

Processing of nonmagnetic taconites by selective flocculation-des liming and anionic flotation of calcium-activated silica has been investigated using innovative procedures as a means of improving operating costs. Areas chosen for cost-cutting evaluation were grinding, fine screening, and water conservation and reclamation. The investigation was performed on Marquette range nonmagnetic taconites in the Bureau of Mines Twin Cities Metallurgy Research Center flotation pilot plant, at feed rates ranging between 900 and 1,100 lb/hr. With fully integrated water reclamation, flotation concentrates containing 65.8 percent Fe and 3.4 percent Si02 were made in the best operating period, with accompanying weight and iron recoveries of 40 and 74 percent, respectively. During this same period, the estimated cost of both flotation and water reclamation reagents was only $0.80 per ton of concentrate (1968 pricing basis). This cost is about 15 percent lower than obtained previously at this Center for flotation reagents only. The investigation demonstrated additional potential savings in operating costs of approximately $0.96 per ton of concentrate through autogenous grinding as a substitute for ballmilling. Fine screening of intermediate concentrates was employed advantageously, but the frequency of blinding may be a factor militating against use of the screen in this flotation system.

Jan 1, 1973

By Robert L. Lagace, N. Albert Moussa

The objective of this project was to perform a preliminary study to determine the desirability/practicality of burying the communication cables in underground mines in order to protect then from the effects of fires and explosions We conducted discussions with Government and industry specialists on the physics of mine fires and explosions, mine disaster fighting, rescue, and investigation activities, and on nine operations. In addition we examined published experimental work and selected detailed NSHA accident reports on fires and explosions in underground mines. We found the overall desirability /practicality of cable burial must be regarded at this time as highly questionable, because of its benefit limitations to special sceneries, its practical operational shortcomings, and the availability of alternative cable protection options.

Jan 2, 1982

By Isaac A. Zlochower, Michael J. Sapko, Ronald S. Conti

This paper describes a U.S. Bureau of Mines investigation of large-scale coal dust explosions in an experimental mine using a high speed electro pneumatic mechanism for the rapid grab-sampling of gases and dusts. This technique enables the monitoring of pyrolysis and charring in fuel dust particles, and the collection of gaseous combustion products, in both large and small-scale explosions. Data obtained from full-scale dust explosion tests at the Bureau of Mines Lake Lynn Test facility show the following: Rapid sampling appears to "freeze" the burned gas compositions at the flame temperature values. Gas samples taken entirely in the flame zone consist of pyrolysis and combustion products with very low residual oxygen. The particles collected in the flame zone show signs of extensive pyrolysis and charring. Measurements of gas concentrations and particle flame temperatures suggest that char burning may have occurred in the flame zone.

By Paul W. Johnson

An evaluation is made of a lime-soda sinter process for extracting alumina from anorthosite. In this process, alumina is extracted by sintering anorthosite with soda ash and limestone, and then leaching the sinter with a dilute sodium carbonate solution. The sodium aluminate solution formed during leaching is separated from the residue and treated with lime in autoclaves to remove dissolved silica before alumina trihydrate is precipitated with carbon dioxide. The trihydrate is then calcined to a-alumina. Two options, dry grinding and wet grinding, are used in the sintering step. For plants producing 1,000 tons of alumina per day for the dry grinding and wet grinding options respectively, the estimated operating costs are $75.40 and $74.36 per ton of alumina when charging $2.50 per ton for anorthosite and $1.00 per ton for limestone. The fixed capital costs based on a Marshall and Stevens chemical equipment index of 240.0 are $76 million and $70 million respectively. This process, when treating anorthosite, using either option, is not competitive under current economic conditions with the Bayer process treating bauxite to produce alumina.

Jan 1, 1968

By L. Cheng

This Bureau of Mines report summarizes an investigation of the amount of respirable dust adhering to the surfaces of seven run-of-face broken bituminous coals. The number of respirable-size (0.9 to 10 micrometers) particles adhering to the run-of-face coal ranged from 1011 to 1012 particles per pound of coal and was approximately inversely proportional to the mean lump size of the coal sample, otherwise it did not vary significantly with the coal seam, mining method, or winning machine. Based on these results, about 16 lb of ordinary run-of-face broken coal would have enough respirable-size adhering dust to contaminate 1,000,000 ft3 of air up to the 2 mg/m3 level, if this adhering dust should become airborne. Although brief studies here suggest that a negligible amount of new respirable dust is formed due to fracture of the broken coal during dropping, dislodging of old adhering particles during secondary handling operations is a potentially dangerous source of airborne respirable dust.

Jan 1, 1973

By P. L. Woolf

Oil was successfully injected into the tuyeres of the Bureau of Mines experimental blast furnace. Determinations were made for the minimum oil addition necessary to permit the maximum available blast temperature of 2,250° F. and the maximum oil rates at blast temperatures of 1,900°, 2,000°, and 2,100° F. From these tests, the upper and lower levels of high-temperature heat input, which limit the smoothly operating furnace, were established. Substantial coke saving was realized with maximum oil injection. Oil-to-coke replacement ratios have been calculated for various conditions, and oil is compared with natural gas and moisture in somewhat general terms. A study of the effect of variations in slag volume and basicity on the sulfur content of the metal at high sulfur loads was made.

Jan 1, 1963

By Michael G. Pojar, John K. Ahlness

"The copper industry has had a long and interesting history associated with leaching, involving vat, dump, heap, and in situ methods. The Bureau of Mines has also had an interest in copper leaching and has researched the techniques of solution recovery, particularly concentrating on in situ methods. In situ mining is a relatively low cost method and has been proven commercially successful by nine operations. It has been most commonly used for final recovery in old workings at the conclusion of conventional mining operations.This report brings together information about 10 commercial in situ operations as well as 14 experimental projects. These 24 sites comprise most of the in situ copper mining activities that have taken place in the United States. Background information, geology, ore preparation, solution application, and recovery and processing are provided for each operation. Production data and tables summarizing the engineering statistics for each operation and an extensive in situ mining bibliography are included. INTRODUCTIONThe purpose of this Bureau of Mines report is to summarize the documented in situ copper leach mining activities that have taken place in the United States. It was prepared to provide a source of engineering and operating data upon which future in situ copper mining activities can be based. Twenty-four different sites are discussed. These are all of the sites that are known to the authors from the extensive in situ copper leach mining bibliography developed at the Bureau's Twin Cities (MN) Research Center (Appendix B).In situ copper leach mining activities fall into the following categories:1. Commercial operations with ore body preparation.2. Commercial operations in old mine workings.3. Experimental programs.Ore body preparation includes such activities as blasting, block caving, and hydraulic fracturing (hydrofracing) specifically to fragment the ore body. Operations in old mine workings include those done in open pits, worked out block caved areas, and backfilled stopes where leaching is done as an afterthought to conventional mining. Experimental programs are small-scale tests of the feasibility of a commercial operation. Some of these programs did not progress to the point where leach solutions were applied to the ore.Each operation (locations shown in figure 1) will be discussed in terms of background information, geology, ore preparation, solution application, recovery and processing, and engineering and production data. Information was collected from published reports, communications with company personnel, and site visits."

Jan 1, 1982

By Joseph S. Coffman

The Bureau of Mines investigated the availability of barite (BaSO4) from 35 U.S. and 41 non-U.S. mines and deposits in 17 market economy countries (MEC's). This evaluation assesses the availability of mud-grade barite, and concentrates consumed by the chemicals and fillers industries. The demonstrated resources defined in this analysis totaled 130 million metric tons (Mmt) of barite (contained BaSO4), yielding a potential 115 Mmt of recoverable barite concentrates. At the 1984 MEC production rate, the evaluated resources would last about 30 yr; however, this would include production costs of up to $100/mt concentrate. An average price needed to cover all costs of production over the life of each operation was determined for both mud-grade and chemical- and filler-grade barite products. Including a 0-pct discounted-cash-flow rate of return (DCFROR), regional weighted- average total production cost ranged from $38/mt for barite concentrates in Asia to $71/mt for U.S. operations. Transportation costs have the greatest impact, contributing up to 60 pct of the total cost of production. Rail transportation costs from the mines to U.S. markets are generally significantly higher than ocean shipping rates on imports.

Jan 1, 1986

By J. S. Hansen

The U.S. Bureau of Mines developed a system for casting unique, slotted steel armor by modifying the conventional expendable pattern casting (EPC) process that is normally used for making aluminum castings. Three innovations were added to the EPC process to make the successful adaptation: (1) Vacuum was applied to sand molds, (2) continuous narrow-necked feeding systems were used to permit the casting of thin walls, and (3) fixtures were designed to prevent pattern damage and to hold critical casting tolerances, Potential problems and defects are described.

Jan 1, 2010

By W. D. Bryson

This paper is one of a series being prepared by the United States Bureau of Mines on tunnel-driving methods. The practices described are those used at No. 11 mine of the Colony Coal Co., Denver, Colo. No. 11 Mine is situated at Dines, some 14 miles north of Rook Springs, in Sweetwater County, Wyo. It is served by a spur off the Winton branch of the Union Pacific Railroad. The Colony Coal Co.'s mines were opened in 1918, and since that time have been among the largest producers of coal for the railroad and domestic markets in the Rock Springs coal district.

Jan 1, 1932

By J. C. White

A research study was conducted to devise a method for producing phosphoric acid directly from unbeneficiated Florida phosphate matrix. This research was performed as part of the Bureau of Mines, U.S. Department of the Interior, goals of improving minerals and metals recovery from domestic resources and of minimizing the environmental impact associated with mineral recovery operations. This report describes research in which unbeneficiated, dry, south-central Florida phosphate matrix was digested with sulfuric acid in a continuous-circuit, five-tank reactor to yield phosphoric acid and gypsum residue. Feed capacity of the reactor was 100 pounds (45 kg) of dry matrix per 24-hour day. When digestion was carried out at 185° F (85° C), acid filtration rates of up to 420 pounds of P20S per square foot per day were attained. Combined iron and aluminum impurities in the product filter acid were about 60 percent greater than values reported in commercially produced acid derived from concentrate. phosphate recovery was 87 to 90 percent of the phosphate contained in the as-mined matrix.

Jan 1, 1978

By Everett A. Sondreal

Material and energy balances for stockpiled lignite were calculated by computer simulation techniques to determine the occurrence of spontaneous heating. Data on properties of lignite which affect spontaneous heating were required. In some cases, best values from reported data were utilized; in other cases, new data were developed. These include specific studies on the rate and conditions that influence oxidation, heat of oxidation, heat of wetting, specific heat, thermal conductivity, and permeability of stockpiles to air. These data are presented and discussed in detail for possible application to other studies. Results of computer simulations confirm past field experience on the storage of lignite containing as-mined moisture, and predict a greater risk of heat occurrence in stockpiles of dried lignite where experience is lacking. Successful storage was predicted for dried lignite of 20 pct moisture content, if it were cooled after drying and compacted to an interparticle void fraction of 9 pct (bulk density of 67 lb/cu ft) compared to 10 pet void fraction (72 lb/cu ft) for as-mined lignite.

Jan 1, 1974

By Samuel P. Harteis, Eric S. Weiss

The National Mining Association and the Mine Safety and Health Administration requested that the National Institute for Occupational Safety and Health (NIOSH) conduct full-scale evaluations of a recently developed carbon fiber-reinforced polymer (CFRP) reinforcement technique for upgrading existing mine ventilation seals to withstand an explosion pressure of 50 psi or greater. The evaluation was conducted in the NIOSH Pittsburgh Research Laboratory’s Lake Lynn Experimental Mine (LLEM) near Fairchance, PA. The purpose of the evaluation was to determine the blast resistance of the CFRP reinforcement technique, designed to increase the strength of two types of existing 20-psi-rated in situ mine ventilation seals. Two candidate ventilation seals were selected to represent the 20-psi alternative seal designs typical of those used in mines prior to July 2006. Installed within the LLEM were (1) a 4-ft-thick pumpable cementitious foam seal using material with a designed 150- to 200-psi average compressive strength at 28 days and (2) a 24-in-thick, low-density cementitious block seal with a center pilaster and keyed to the floor and ribs. The materials necessary for the CFRP reinforcement technique were then installed on the outby (active) side of each seal, and the seals were subjected to explosion overpressures. Both seals with the CFRP reinforcement retrofit successfully withstood explosion pressures of 60 psi or greater during the full-scale evaluations in the LLEM.

Jan 1, 2008