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By David C. Peters, Robert S. Crosson

A method of error analysis has been applied to the location technique of non-linear least squares iterative inversion in order to evaluate the resolving power of several seismic array configurations with various assumed earth models and errors and inaccuracies in arrival times. The results obtained demonstrate that lateral accuracies of location are improved significantly when the depth of the miner is known. Lateral location to within 100 feet appears achievable in many instances. If it is possible to refine earth models significantly beyond what has normally been assumed in this work by the use of on-site data, or if the mine is shallow (300 feet or less), accuracies of-about 30 feet or so may be attainable. Inaccuracies in earth models of about 5% are found to contribute much more heavily to these location inaccuracies than errors of a few milliseconds in picking arrival times; however, arrival time errors of 15-20 ms or above will dominate these model inaccuracies. The expected accuracy of location is found to fall off very rapidly as the miner moves outside the array. The strength of this effect depends markedly upon the geometry of the array configuration and can be reduced by careful design. Also, as the size of the array is increased, expected location errors within the array are not altered much, but continue to match the error associated with the smaller array over a larger area (assuming that all stations can still pick up the miner's signals). Better location accuracy, especially with respect to depth control is achievable in an earth where the velocity is depth-dependent (increasing with depth) than in one which is homogeneous. This is an advantage since the

Jan 1, 1974

By K. E. Tame

The Bureau of Mines is studying possible modifications in conventional uranium ore-processing steps to confine and permit controlled disposal of radioactive wastes. Surveys of Ra226 contamination of liquid wastes from uranium mills indicated that the Vanadium Corporation of America plant at Durango, Colo., had one of the more urgent problems. A possible procedure for minimizing the waste disposal problem was to reuse the waste solution in the mill--in effect, erasing the need for disposal of liquid waste. In examining this possibility, interlocked bench-scale leaching and solvent extraction tests simulating the Durango flowsheet were made. The simulated reuse of barren raffinate for leaching and washing was carried through three separate campaigns of 9, 12, and 35 cycles each.

Jan 1, 1961

By Edward L. McHugh

Mineral resources in the Silver Creek study area of the Nez Perce National Forest. Idaho, were investigated during the summer Of 1989. The study area includes the 36,100-acre Silver Creek-Pilot Knob RARE II area (No. 1-849) on the north side of the South Fork Clearwater River, about 11 miles west of Elk City, 10. Mines in and near the study area in the Tenmile and Newsome mining districts produced about 100.000 02 of gold, mostly from placers. Gold production had an historic value estimated at 52 million, equivalent to nearly $40 million at today's prices. Lode mines produced about 19,000 oz of gold, along with smaller amounts of silver, copper, lead, and zinc. Of 34 mines and prospects examined, ten lode properties are considered to be significant by virtue of their past development or production and the presence of possibly ore-grade mineralization. There are no identified mineral resources in the study area; however, samples that contained gold and anomalous arsenic delineate a three-mile-long area from the Sentinel mine, north to the Blue Quartz prospect where exploration might disclose resources. One mining company is conducting geophysical studies and drilling within the delineated area. In addition, six placer sites may contain enough gold to be of possible interest for future exploration and development.

Jan 1, 1991

By A. W. Henderson

The growing importance of halide metallurgy for preparing high-purity metals has stimulated research to extend halogenation reactions to the direct extraction of metals from low-grade sources. This Bureau of Mines investigation involves a pioneering study of chlorination reactions in the presence of a fluorine donor. Tin slags containing tantalum and columbium and a zircon concentrate containing a relatively high ratio of hafnium to zirconium were studied. Direct chlorination of these materials at 500° C. yields only a 5-percent conversion of tantalum and columbium or zirconium and hafnium to anhydrous chlorides. This investigation showed that small additions of calcium fluoride to the reaction increased the recovery of tantalum and columbium to 95 percent and the recovery of zirconium and hafnium to 27 percent. These results were achieved with ratios of calcium fluoride to mineral or slag of only 0.2. Silica, the major impurity in the materials studied, was found to be converted to silicon tetrafluoride during chlorination in direct proportion to the quantity calcium fluoride added to the charge. However, large additions of calcium fluoride decreased the volatility of the resulting halides of tantalum, zirconium, and hafnium. Smaller amounts of calcium fluoride also favored recovering minor metal constituents in the zircon concentrate (uranium, thorium, and rare earths).

Jan 1, 1962

By J. S. Dunning

The Bureau of Mines investigated a series of Fe-Al-Mo alloys strengthened by ZrC (zirconium carbide) precipitates as chromium-free substitutes for stainless steels. Melting and fabrication methods were devised, and the effects of minor additions of columbium (niobium) and cerium on the mechanical properties and oxidation resistance were determined. Zirconium carbides could not be con-trolled reliably to produce fine precipitate dispersions. A more reliable carbide strengthening mechanism is required if the high-temperature strengths of types 304 and 316 stainless steels are to be duplicated. Workability and oxidation resistance of the alloy series were excellent.

Jan 1, 1982

Various aspects of judgment and decision-making are key themes in this book. The model presented here serves as a loose structure for the chapters that follow this one. The notion of a model is introduced because growing research interest in the subjective aspects of group and individual behavior has led to a debate over whether judgment is a skill that can be understood scientifically. A related point of contention is whether such an understanding could lead to the development of methods for estimating people's ability to make good decisions during an emergency. There is some literature that supports the potential usefulness of this approach. However, little agreement seems to have been reached on how to define and operationalize even those basic concepts necessary to assess the soundness of decisions from within their environmental and group contexts [Jensen and Benel 1977; Godden and Baddeley 1979; Baumann and Bourbonnais 1982; Brecke 1982; Stone et al. 1985]. A look at the real-world process is clearly needed. The need to attempt a better understanding of judgment and decision-making properties stems from those occasions in the existence of an organization when there is a lot at stake. The process of decision-making (which is part of the exercise of judgment) has been analyzed in situations such as corporate takeovers [Janis and Mann1977], military combat [Begland1979], clinical emergencies [Baumann and Bourbonnais 1982], and aviation events [Billings and Reynard1984]. The fundamental assumption of these analyses is that, while there are untold successes, there are also notable numbers of failures resulting from decisions that can be ascribed to one or more errors in judgment. From a cognitive perspective, any person engaged in decision-making (either alone or in a group) is actively involved in a process characterized by certain elements. These were mentioned in chapter 1, but are reiterated briefly at this point: (1) detection of a problem, (2) definition or diagnosis, (3) consideration of available options, (4) choice of what is perceived as the best option given recognized needs, and (5) execution of the choice based on what has transpired [Flathers et al. 1982; Baumann and Bourbonnais 1982]. At any moment in this process, there are factors at play that have a large impact on one's ability to solve complex problems in a limited time: (1) an internal state [Hedge and Lawson 1979] is the sum of a person's psychomotor skills, knowledge, attitudes, etc.; (2) uncertainty [Brecke 1982] is caused by faulty or incomplete information received from the external environment; (3) stress [Biggs 1968; Jensen and Benel 1977] is generated both by the problem at hand and any background problem that may exist; and (4) complexity, as it is used here, refers to the number of elements involved that must be attended to. These variables are depicted in figure 5.1, and their relationship to each other and to an outcome is indicated. This schema is designed to suggest interaction, because while the judgment and decision-making process may be conceptualized as discrete stages, experience tells us that this is not the way people function in real-world situations.

Jan 1, 2000

By A. B. Needham

This report describes the exploration work done in 1941 in connection with the search for strategic minerals as authorized by the Strategic Materials Act approved by the President on June 7, 1939. It deals with the various manganese deposits and showings in the Tombstone mining district of Cochise County, Ariz. The exploration project comprised a study of the geology, mapping of the areas, and exploration of various mines and deposits by sampling old drifts, crosscuts, and scopes, supplemented by diamond drilling from underground stations. The Federal Government's manganese-purchasing programs have revived interest in occurrences such as the scattered deposits near Tombstone. Because of this, the Bureau of Mines project report on the Tombstone district, prepared originally in 1941 but not published, has been revised and now is being made public.

Jan 1, 1956

By M. R. Geer

The cleaning of fine coal, particularly for metallurgical use, is receiving greater attention. An increase in the proportion of fine coal in the run-of-mine product has been created by changes in mining practice, and a concur-rent deterioration in the quality of the fines has occurred because of more widespread full-seam mining. These two factors, augmented by the depletion of premium beds of metallurgical coal in some areas and the resulting shift to "dirtier" beds, are providing the impetus for adoption of improved cleaning techniques. For example, froth flotation, which has been used for years in a few preparation plants, now is gaining more rapidly in acceptance. Similarly, the dense-medium cyclone, which is used widely in Europe for making difficult separations, recently has been introduced to the United States. Regardless of the cleaning process employed, the finer sizes of coal can be treated with maximum effectiveness only when they are removed from the run-of-mine product and treated separately. No present process can treat the full range of sizes together with complete effectiveness. Flotation is applicable only to the coal finer than a top size ranging between 14-and 48-mesh, and cyclones require removal of all material finer than 0.5 to 0.3 mm. from the feed. Thus, the trend toward more-effective cleaning of the fine coal imposes the attendant problem of fine screening. Whereas in the past there was little need to screen finer than about l/4-in., present developments indicate that fine screening will become increasingly prevalent.

Jan 1, 1960

By John S. Berber

Tar produced as a byproduct from low-temperature carbonization of coal contains only small amounts of valuable lower boiling tar acids but relatively high percentages of high-boiling tar acids. These high-boiling tar acids are characterized by a high degree of alkylation and can be converted into the lower boiling homologs by catalytic treatment to remove the alkyl groups or decrease their chain lengths.

Jan 1, 1965

By Kenneth H. Johnston

Information and data necessary for research on improving methods of oil recovery from low-permeability reservoirs and for comparison and evaluation of performance of such reservoirs with those producing from more permeable sands were obtained. Core analyses, well logs, production tests, well stimulation techniques, primary and secondary production records, and data on two water-flood projects were examined for wells producing from the Bartlesville sand, West Avant field, Osage County, Okla. Overall recovery from the study area was generally poor with only 9.0 percent of the pore volume recovered to January 1, 1968. Larger fracture treatments (8,000 to 12,000 gal) could have resulted in an increase in primary oil recovery. Secondary recovery by water-flooding accounted for only 1.9 percent of the pore volume because of the inability to control the large volume of injection fluid that escaped from the flood patterns and the excessive volumes of water produced with the oil. Future waterflood development in other low-permeability reservoirs should include the drilling of new input wells, use of injectivity surveys to locate possible natural fracture systems, or zones of high permeability, and control of injection fluids by altering flood patterns and/or plugging of the more permeable zones.

Jan 1, 1968

By Albert W. Deurbrouck

This report describes the preparation characteristics of the Pittsburgh and Upper Freeport coalbeds in Hancock , Brooke , Ohio , and Marshall Counties , W. Va . Over 4.5 million tons of coal was produced in these four counties in 1962. Most of this production came from the Pittsburgh coalbed . Twelve coal samples were collected for this study , 11 from the Pittsburgh bed and 1 from the Lower Freeport bed . Two of these samples could be upgraded to produce metallurgical - grade coal . The sulfur content of the Pittsburgh- bed coals was generally excessive --as high as 4.9 percent in the raw coal and 3.19 percent in the float 1.30 specific gravity fraction . The rank of the coals in this area ranges from high-volatile A to high-volatile B bituminous .

Jan 1, 1964

By Jack C. White

As part of an investigation of the production of alumina by the nitric acid leaching of kaolinitic clay, the Bureau of Mines designed, built, and tested a fluidized-bed system for the calcination of aluminum nitrate nonahydrate to alumina, while recovering nitric acid. The calciner consisted of an 8-in-square by 36-in-tall vessel containing 18 in of fluidized solids. Molten aluminum nitrate, sprayed directly into the fluidized solids, formed sandy, granular alumina by growth of successive layers on fluidized particles. Solids were fluidized in a dense bed at temperatures of 250° to 500° C with steam, air, or mixtures thereof. Decomposition of nitrate ranged from 4 to 10 pet during single-pass steam or air fluidization, respectively. Alumina dust losses and low throughput are significant unsolved problem areas.

Jan 1, 1982

By Joseph Cervik, Gerald L. Finfinger

This Bureau of Mines publication reviews underground methane drainage pro- grams being conducted in various coalbeds. Equipment used in drainage programs such as drills, underground pipelines, and methane monitoring systems is described.

Jan 1, 1980

By David F. Smith

The American Society for Testing Materials4 has recommended that the melting temperature of potassium chromate be used-for indicating the temperature to which a coal sample should be heated in the standard method of analysis to determine its volatile matter content. The specified temperature is 950± 20° C., the melting point of potassium chromate being noted as 940° C. Le Chatelier5 originally found the melting point to be 975°; later6 he found 9400. According to Shemtschushny7 the melting point is 984°; he also found a transition at 679°. Groschuff8 found the melting point to be 971° and the transition temperature 679°. Amadori9 reports a melting point of 9.78° and a transition point of 666°. The International Critical Tables10 take the melting point as 975°, which is estimated to be correct to two significant figures. In view of the apparent uncertainty existing, it has been though worthwhile to make a careful redetermination of this datum. It is of interest not only to determine the melting point of the pure salt, but also of the commercial product, in order to test its suitability for use as a temperature indicator. The work was suggested by A. C. Fieldner, chief engineer, experiment stations division, U. S. Bureau of Mines.

Jan 1, 1929

By T. E. Gray

This report describes the preparation characteristics of the significant coalbeds in Boone County, W. Va., as determined by the Bureau of Mines. It is one of a series describing the coals suitable for producing metallurgical coke, either as mined or after beneficiation. Over 6.3 million tons of coal was produced in Boone County, W. Va., in 1959, of which almost 5.5 million tons was mechanically cleaned in eight preparation plants. On December 31, 1959, it was estimated that almost 8 billion tons of coal remained in the county in beds 24 inches or more in thickness. Thirteen samples were collected from nine coalbeds and washability tests were made on these samples.

Jan 1, 1961

By J. M. Stuve

Thermodynamic properties were determined by the Bureau of Mines for the intermetallic compound, TiA13. Heat capacities were obtained from 5 to 303 K by adiabatic calorimetry. The derived value of S2 1s is 22.08±0.07 cal/deg¬mole. Enthalpies relative to 298 K were obtained from 298 to 1,413 K by copper-block drop calorimetry. No anomalous thermal behavior was noted in the temperature ranges investigated. Low- and high-temperature data were combined with a known enthalpy of formation at 298 K to give values of enthalpy of formation and Gibbs energy formation, 0 to 1,400 K.

Jan 1, 1974

By J. W. Adams

Measurements of surface magnetic field noise were made at various locations over the Geneva Coal Mine near Price, Utah, on June 12, 1973. The locations selected were on the surface over emergency locator beacons underground at depths between 3S0 meters (1150 ft.) and 488 meters (1600 ft.). The surface terrain where these measurements were made was mountainous, and access was difficult. There were no power lines within several miles, and the weather was clear; therefore, the magnetic noise levels were about as low as will normally occur. Results of measurements of distant sferics indicate rather sharp cutoff frequencies below which broadband, impulsive noise is attenuated. The mechanism of propagation for this noise above the daytime cutoff frequency of 3500 Hz and the nighttime cutoff frequency of 1700 Hz is deduced to be a waveguide formed by the D or F layers of ionosphere as an upper plane and the earth as a lower plane.

Jan 1, 1974

By Juel H. Stears

Research was done to determine if a hydraulically operated penetrometer developed by the Bureau of Mines could be used to estimate the roof-bolt anchorage capacity of mine roof rock. Tests were conducted both in the laboratory using cement cylinders and underground in shale rock. Hardness readings were measured by the penetrometer around the periphery of the bolt holes at the anchorage horizon. Roof bolts Nere then installed and subjected to an anchorage test. The results showed that the penetrometer readings could be used to determine the optimum stratum for roof-bolt anchorage but could not be used to make an accurate estimate of the anchorage capacity.

Jan 1, 1965

By Neal M. Muir

The increasing demand for iron ores prompted the Bureau of Mines to investigate the sources of past production in Kentucky to determine whether reserves of usable ore still exist. Preliminary investigation showed that the holdings of the Rose Run Co. were the most promising, inasmuch as the deposit had not been exhausted by past mining and the property was near railroad facilities and but 80 miles from the blast furnaces at Ashland, Ky. The Bureau conducted a churn-drilling and sampling program to investigate the depth, thickness, and iron content of the ore beds so that they might be evaluated as a possible reserve of low-grade iron ores. The Rose Run area in Bath County, Ky., was explored by 74 churn-drill holes totaling 2,059.4 feet of drilling and 4 cuts and test pits. Fifty-seven drill holes and the four test pits penetrated the ore bed at an average depth of 22 feet. The bed had an average thickness of 2.54 feet. Analyses show that the calcium and magnesium carbonate content is more than sufficient to flux the silica and provides an excess that needs an admixture with other siliceous iron ores.

Jan 1, 1950

By M. J. Ankeny

The expression "firing open, unconfined shots," as used in this circular, means the firing of explosive charges not confined in boreholes. Examples are the so-called mudcap shots, adobe or dobe shots, or bulldozing shots consisting of explosive charges placed on, under, or between rocks for the purpose of breaking them. The practice of firing open, unconfined shots is not uncommon in coal mines, despite the fact that numerous mine explosions and dust ignitions have resulted from this practice. The usual method of preparing such shots is to place the explosive with its detonator on top of a piece of rock or coal and cover it with clay, loam, sand, or road dust; frequently no covering of any kind is used. In some mines, an open charge of explosive is placed on timbers to dislodge them or in crevices in the roof to break down loose rock that cannot be dislodged with a bar or pick. The explosive charges may be made and fired singly, although sometimes several charges are placed on one large piece of rock with a detonator in each charge, and all charges are fired simultaneously. Although it is general practice to use permissible shot-firing devices, which will not ignite gas or dust to fire these charges, electric power from the regular mine circuits is sometimes used. When the shot is fired, any coal dust that may be present is thrown into suspension by the blast and may be ignited by the intense hot flame of the explosive or by an arc or spark at the leg wires or the end of the firing leads if power from the regular mine circuit is used to fire the shot. Even if there is not enough coal dust present to form a dust cloud, open, unconfined shots can readily ignite methane.

Jan 1, 1952