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By Francis R. Redfern

Newton's method of solving a nonlinear equation is employed to develop a least-squares acoustic emission source location method in which the spatial residuals of the location equations are minimized. These residuals, related to the distances from the least-squares source location perpendicular to the surfaces described by the location equations, permit location error to be estimated to first order along the spatial axes. The solutions obtained by this method are the best spatial solutions to the location equations in the least-squares sense. Also presented is a procedure by which the geometrical control of a transducer array can be evaluated using the rate of change of source location with fractional velocity change.

Jan 1, 1982

Pillars with width-to-height ratios of less than 1.0 are frequently created in underground hard rock mines. The strength of slender pillars can be estimated using empirically developed equations. However, the equations can provide variable results when the width-to-height ratios approach 0.5. This paper investigates some of the issues affecting pillar strength at low width-to-height ratios in hard brittle rock. The investigation includes an evaluation of empirical pillar strength data presented in the literature and observations of pillar performance in underground limestone mines in the eastern United States, supplemented by numerical modeling in which failure processes and sensitivity of slender pillars to variations in rock mass properties are evaluated. The results showed that the strength of slender pillars is more variable than that of wider pillars. The numerical model results demonstrated the increasing role of brittle rock failure in slender pillar strength. The absence of confinement in slender pillars can result in a fully brittle failure process, while wider pillars, fail in a combined brittle and shearing mode. The onset of spalling in slender pillars occurs at or near the ultimate strength, while this is not the case for wider pillars. Slender pillars are shown to be more sensitive to the presence of discontinuities than wider pillars, which can partly explain the increased variability of slender pillar strength. Two examples are presented that illustrate failure initiation by brittle spalling and the sensitivity of slender pillars to the presence of discontinuities.

By C. B. Manula, R. L. Sanford, R. A. Rivell

This report was prepared by The Pennsylvania State University under USBM Contract No. 60111808. The contract was initiated under the coal Mine Health and Safety Program. It was administered under the technical direction of DMSE, with M. G. R. Schottler acting as the technical project officer. Mr. J. A. Herickes was the contract administrator for the Bureau of Mines.

Jan 1, 1974

By Michael D. Fenton

Detailed comprehensive assessment of the performance of Afghanistan's mineral industry during 1987 is virtually impossible, owing to the paucity of reliable published information. It was evident, however, that the level of civil disorder, now in its eighth year since the arrival of significant numbers of Soviet troops, was in actuality little removed from open civil war. Insurgents controlled substantial areas of the country and imperiled any industrial activity in many places. Assistance programs by the U.S.S.R. and other Eastern European nations were directed at developing the country's meager mineral industry, but the economy was generally viewed as chaotic. The inflation rate was somewhere between 20% and 30%; major food shortages contributed to the discontent of the population, and numerous villages were devastated by Soviet and Afghan Government campaigns to destroy the insurgents and cut their supply routes. Moreover, proposals by the Soviets and the Kabul Government aimed at reducing tensions with the rebels and scaling down the warfare seemingly were taken by the opposition as signs of weakening by the Soviet-backed Government, and rather than reducing aggressions, seemed to heighten insurrectionist activities. Efforts to entice the substantial number of Afghans who have fled to nearby areas of Pakistan and Iran to return to their country seemingly were failures, and indications near yearend that the Soviet Union might soon begin withdrawal of its occupation force of nearly 120,000 did little if any to reduce disorder.

Jan 1, 1989

By Alan R. Buehler

The Bureau of Mines conducted a mineral investigation of the 32,270-hectare Cache Peak study area in 1992; the area had been proposed as wilderness. Bureau personnel examined and sampled prospect workings; 50 rock and placer samples were taken during the investigation. The study area is centered about 25 km southeast of Challis, Idaho, in the Challis National Forest. According to May, 1993, Bureau of Land Management mining claim records there were no current mining claims located inside the study area. Up to 100 claims may have been located in the study area in the past. Gold, silver, copper, lead, zinc: Significant analyses, poor exposure precludes resource estimate. Limestone: More than I billion tonnes may be chemically suitable for a variety of uses, markets too distant to favor mining. Dolomite: More than 1 billion tonnes may be chemically suitable for producing magnesium metal, markets too distant to favor mining. Sand and Gravel: Several million m3, but markets and transportation costs do not favor mining. Chalcedonic nodules: Two localities in the study area may be of interest to hobbyists who cut and polish stone. There is no reported past production from the study area.

Jan 1, 1993

By Michael J. Brnich

Since 1991, Pittsburgh Research Center (PRC-formerly part of the Bureau of Mines) researchers have recorded extensive interviews with 30 individuals who are experts in the area of mine emergency response. These individuals, who have an average of 35 years of mining experience and 29 years of mine emergency response experience, related stories and observations from events that they experienced during their combined 850 plus years in mine emergency response. The purpose of this effort was to gather information that could be passed on to both today?s and tomorrow?s mine emergency responders to train and guide them in handling future events. This is the first of two articles which report the responses that these experts gave when asked how they think people who may have to respond to a future mine emergency should be trained. During the interviews they discussed how training should be conducted, who should be trained, and what topics should be included. This article will cover the first two areas: what training methodologies would be most effective and who needs to participate.

Jan 1, 1997

To evaluate the potential for dust reduction, during blasthole drilling, of water or foam applied directly into the drill hole. Approach The Bureau of Mines tested a through-the-drill-steel water and foam injection technique in two noncoal mines to evaluate the method's potential for greater dust reduction. The tests were performed by drilling a series of blastholes for an entire face (a 90 minute time-period). For the first 45 minutes of drilling, foam or water was applied through the drill steel. Blowing ventilation was supplied to the entry about 50 feet from the face. The dust concentration measurements were made by a Real-Time Aerosol Monitor (RAM-I), and the data were read out on a strip chart recorder. The evaluation test results showed that the water or foam injection technique, when used on localized dust sources, can be an extremely effective dust control method. Small amounts of water used in this method have also allowed it flexibility to be used in water-soluble ores such as salt, gypsum, anhydrite, and trona. How The System Works Water or foam is mixed with compressed air (approximately 100-120 psi) with suitable metering systems and forced through the drill steel into the blast hole at the point of dust generation. Because the water or foam is applied at the source, minimal quantities of liquid are needed (0.2 to 0.6 gpm). These low flowrates are sufficient to just moisten the dust emerging from the blast hole, thus eliminating a major source of airborne dust. The wet drilling procedure also eliminates a second source of dust. With dry drilling, the dust from the blast hole falls to the floor. Since this can be a 15-ft drop or more, the impact can send the dust billowing up from the floor, adding to the airborne dust. With wet drilling, the moistened dust merely dribbles down the face.

Jan 1, 1982

Reduce well construction and operation costs associated with in situ leach mining while increasing mineral recovery. Approach To accommodate the size of centrifugal pumps presently in use, in situ leaching production wells are typically drilled to 6 inches in diameter, while monitor wells are drilled to measure 4 inches in diameter. However, in order to reduce the cost of drilling these larger diameter wells and to increase recovery, the Bureau has developed jet pumps which have smaller diameters than centrifugal pumps of the same capacity. This allows both production and monitor wells to be drilled smaller. Bureau estimates indicate that the cost of drilling a 3-inch-diameter production well at in situ leaching operations would be about 35 percent less than the cost of a 6-inch well. Similarly, the cost of drilling a 2-inch-diameter monitor well would be about 26 percent less than the cost of a 4-inch well. Such significant savings in the cost of drilling these wells would effect a substantial reduction in total capital cost. Use of the new jet pumps can also increase the percentage of recovery because less costly wells allow closer well spacings, improving the distribution of the leach solution. How the System Works After the borehole is cased, the new small-diameter jet pump, along with piping and accessories, is installed and connected to a centrifugal pumping unit on the surface. High-pressure water from the surface pump is forced through a nozzle into the venturi of the jet type pump injector. This jet action lifts the leach and mineral-bearing solution to the surface.

Jan 1, 1984

By Rose L. Ballard

This chapter summarizes data on crude nonfuel mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are the tables that show the principal nonfuel mineral commodities exported from and imported into the United States and that compare world and U.S. mineral production. The detailed data from which these tables were derived are contained in the individual commodity chapters of Volume I and in the State chapters of Volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at any of several stages of extraction and processing, the stage of measurement used in this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the output from auxiliary processing at or near the mines.

Jan 1, 1985

By Kenneth L. Cashddollar, Terry G. Montgomery, Eric S. Weiss, John E. Going

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) and the Mine Safety and Health Administration (MSHA) conducted joint research on dust explosions by studying post-explosion dust samples. The samples were collected after full-scale explosions at the PRI, Lake Lynn Experimental Mine and after laboratory explosions in the PRL 20-L chamber and the Fike 1-m3 chamber. The dusts studied included both high and low volatile bituminous coals. Low temperature ashing for 24 hr at 515°C was used to measure the incombustible content of the dust before and after the explosions. The data showed that the post-explosion incombustible content was always as high as or higher than the initial incombustible content. The MSHA alcohol coking test -was used to determine the amount of coked dust in the post-explosion samples. The results showed that almost all coal dust that was suspended within the explosion flame produced significant amounts of coke. Measurements of floor dust concentrations after LLEM explosions were compared to the initial dust loadings to determine the transport distance of dust during an explosion. All of these data will be useful in future forensic investigations of accidental dust explosions in coal mines or elsewhere.

By R. C. Gabler

Laboratory tests on a combined nitrogen roast--two-stage leach--electro-winning approach show promise as a possible process for recovering copper, sulfur, iron oxide, and valuable minor metals (gold, silver, and molybdenum) with a minimum impact on the environment. During the nitrogen roast at 800° C, 15 to 20 percent of the sulfur together with a significant fraction of the volatile elements, such as arsenic, bismuth, lead, and zinc, are removed from the chalcopyrite concentrate. The resulting calcine, consisting of 8-chalcopyrite, troilite, and a bornitelike structure, is leached with hydro-chloric acid to remove 70 to 85 percent of the iron. The digenite in the leach residue is dissolved in an oxygen-saturated, spent sulfate electrolyte. Using a graphite 'anode plus sulfur dioxide to reduce interference from ferric iron, copper of 99.99+ purity is electrowon at current efficiencies of 88 to 92 percent and a cell voltage of 0.4 to 0.5 volt. Copper recovery for the overall process is 98 to 99 percent. Sulfur is obtained in the elemental form from the roasting and leaching steps. Iron can be recovered from the hydro-chloric acid leach solution. Gold, silver, and molybdenum are concentrated in the silica residue from the spent electrolyte leach.

Jan 1, 1975

By William G. Gruzenaky

The separation of yttrium and the individual rare-earth elements (lanthanons) from mixtures in which they occur has been a difficult problem through-out the years. Because of the increased interest in the various uses of these metals, the economy of their production may become of great importance. Studies relative to this problem, undertaken at the Federal Bureau of Mines Albany Metallurgy Research Center, resulted in the development of a solvent extraction method by which yttrium can be separated from the rare-earth metals. A separation factor of 10.93 was obtained between yttrium and cerium from a single-stage extraction, and a factor of 1.78 was obtained between yttrium and erbium from a multistage system. The valuable metals were extracted from euxenite by caustic soda fusion or by chlorination, and several separation methods were investigated. Partial separation of the yttrium and rare-earth element fraction was made by chemical methods and by solvent extraction. Thermal decomposition of aqueous rare-earth nitrates or selective ignition of yttrium and rare-earth oxalates yielded a fraction enriched in cerium. A fraction enriched in the light rare-earth elements resulted from a double sulfate precipitation, whereas a potassium ferrocyanide pr cipitation yielded a fraction enriched in yttrium. Precipitation with dimethyl phosphate yielded a fraction enriched in yttrium and heavy rare-earth elements. Enriched fractions were obtained with several solvent extraction systems. A system consisting of rare-earth nitrates, nitric acid, and tri-n-butylamine-3 methyl-2-butanone favored the separation of yttrium from the heavy as well as from the light rare-earth elements.

Jan 1, 1961

Maps To Accompany Bulletin 507

Jan 1, 1952

By M. L. Whisman

The Bureau of Mines developed a radiotracer method for detecting the contribution of selected components and additives to thermally induce deposits of turbine aircraft fuels. Fuels were examined before and after 52 weeks of storage at 130° F. Of particular concern was the influence of aromatic hydrocarbon fuel constituents on thermal-stability quality of jet fuels during storage. A microfuel coker test apparatus was used to thermally stress the test fuels and blends, and the resultant contribution to deposits of selected fuel components, labeled with carbon-14, was determined by radioactive-counting techniques. Ninety-one blends of five test fuels with carbon-14-labeled fuel additives or components were prepared, tested, stored for 52 weeks at 130° F, and reanalyzed for deposit-forming tendency. These additives included two anti-oxidants, a metal deactivator, and a corrosion inhibitor. Of the labeled hydrocarbon fuel systems studied, the greatest reaction was observed in blends containing methyl-and ethyl-substituted indenes. Other aromatic types also showed some contribution to the deposits. Three of the additives showed a marked tendency to degrade and react during storage and thermal stress. A cresol antioxidant, however, barely contributed to deposit formation. Oleic acid interacted with cadmium present in aircraft fuel systems and produced deleterious effects upon the thermal-stability quality of the fuel.

Jan 1, 1971

By R. P. Beyer

[The Bureau of Mines has measured the low-temperature heat capacities and high-temperature enthalpies of crystalline K2Si2O5 as part of a program for advancing mineral resources technology with energy economy. High-temperature enthalpies of glassy and liquid K2Si2O5 and crystalline K2SiO3 were also mea¬sured. An adiabatic calorimeter operating over the range 5 to 308 K was used for the heat capacity measurements for K2Si2O5 from which the standard entropy at 298.15 K, S°298 = 45.55 ±0.05 cal/deg-mole, was calculated. Tabulated values of Cp°, S°, -(G° -HO°)/T, and H°-HO° from 5 to 300 K are given for K2Si2O5. A copper-block drop calorimeter was used in the enthalpy measurements, operating from 298.15 to 1,198 K for K2SiO3 and from 298.15 to 1,453.8 K for K2Si2O5. No transitions were found for K2SiO3. The KI2Si2O5 showed two reversible first order transitions, one at 510 K with a heat of transition of 0.29 kcal/mole and one at 867 K with a heat of transition of 0.38 kcal/mole. The heat of fusion for K2Si2O5 20 5 was calculated to be 8.42 kcal/mole. Relative enthalpies are given in equation form, and high-temperature values are tabulated for Cp°, S°, - (G°-H°298 )/T, and H°-H°298 . Also tabulated are ?H°, ?G°, and log K for formation of K2SiO3 and K2Si2O5 from both the elements and the oxides.]

Jan 1, 1979

By Jalna R. Zatko

The Bureau of Mines, U.S. Department of the Interior, has developed a novel method of flocculation dewatering of phosphatic clay wastes using polyethylene oxide as the flocculant. Research was conducted to determine whether ethylene oxide gas was present in the air in the vicinity of disposed waste materials which had been flocculated with polyethylene oxide. Samples of clay waste materials containing polyethylene oxide were prepared in stoppered glass bottles in simulated disposal environments. Gaseous samples, removed over a 75-day period using an airtight syringe, were injected into a gas chromatograph that was capable of separating ethylene oxide from air. The presence of ethylene oxide gas was not detected in any sample. To determine possible degradation products of polyethylene oxide, the properties and reactions of ethylene oxide and its polymers were reviewed. Based upon the literature survey and experimental study, it was concluded that adverse environmental effects were not likely to result from the use of polyethylene oxide for flocculating phosphatic clay waste products.

Jan 1, 1980

By Paul Sands

Single- and two-stage tests were made with 6-inch, coal-cleaning hydrocyclones to determine the effect of hydrocyclone geometry, operating conditions, and feed composition on performance. Most of the testing was conducted in an open-circuit pilot plant that had a maximum capacity of about 9 tons per hour. The coals used in the investigation had top sizes of 1/4 inch and 28 mesh. Considerable latitude was found in the range of geometry variables that could be used without affecting performance adversely, although a certain minimum ratio of overflow to underflow openings had to be maintained for best operation. Two-stage cleaning proved distinctly better than operation with a single hydrocyclone, because clean coal lost in the refuse product of the primary unit can be partly recovered in the secondary. There is an unusually great difference in the specific gravities at which the individual sizes of the feed are separated in the hydrocyclone. This militates against high efficiency because maximum yield occurs when all sizes are cleaned at the same specific gravity. The size composition of the feed and, more particularly, the size composition of the impurity have a greater influence on the efficiency attainable in the hydrocyclone than in most other types of fine-coal cleaners.

Jan 1, 1968

By Ryron O. Pickard

"The Berkeley safety station of the U. S. Bureau of Mines was recently informed that a geologist was killed through entering an abandoned 90-foot exploratory shaft without making a preliminary test of the shaft atmosphere. He was one of a geological party which was investigating coal lands in California. The only light that he carried into the shaft was an electric flash light. After he had descended a short distance, one of his associates on the surface heard him exclaim, ""This place is full of gas, I am coming up"", He had no more than finished the remark when he was seen to lose his grip on the ladder and fall down the shaft. He was apparently weakened from impure air in the shaft, and could no longer suppers himself on the ladder. When his body was recovered, it was found that his neck had been broken by the fall.This is the ;second recent accident that has been called to the writer's attention where a life has been lost in abandoned exploratory workings; the other fatality being in Minnesota where a mining engineer was overcome while sampling a shallow pit in iron-ore formations. This engineer was on the bottom of the shallow pit and died before help could reach him. It was generally supposed that each of these deaths were due to poisonous gases, but the writer believes, after reviewing the information available, that death in both instances may have been directly caused by deficiency in oxygen.Frequently in the daily press there are items relative to lives being lost through cleaning out old wells, and as a general rule such accidents are also caused by impure atmospheres.In every abandoned shaft or pit, or in fact, any old working where the air has been stagnant for a considerable time, there is always danger of oxygen deficiency, as the oxygen which originally comprised one-fifth of the atmosphere may be appreciably replaced by gases that do not support life, usually by carbon dioxide (black damp) or methane (fire damp). Much valuable information on the subject of mine atmospheres, mine gases, and the effect of oxygen deficiency onthe human system is contained in Miners' Circular 14, ""Gases Found in Coal Mines"" by G.F. Burrell and F. M. Seibert; Technical Paper 122, ""Effects of Oxygen Deficincy on Small Animals and Men"", by G. A. Burrell and G. G. Oberfell; and ''Chit of Properties of Mine Gees"" by G. A. Burrell. These publications of the Bureau of Mines should be rent by all who are interested in the subject of this paper."

Nov 1, 1921

By James P. Ulery, Stephen J. Kravits, William P. Diamond

This report presents results of a cooperative research project between the U.S. Bureau of Mines and Beth Energy Mines, Inc. Four coreholes (two before mining and two after mining) were drilled at a longwall mine operating in the Lower Kittanning Coalbed to obtain coal and rock samples from overlying strata to determine their gas content at various times in the mining cycle. The results of those tests indicate that 91 pct of the gas removed from the overlying strata came from coalbeds. Material balance calculations were made to compare the volume of gas produced both from gob gas vent holes drilled on the panel and gas removed by the mine's ventilation system with the volume of gas removed from strata directly overlying the panel to a height of 275 ft. This analysis indicates that only 40 pct of the total gas produced from the panel actually came from the strata directly overlying the panel. The remaining volume of gas production probably migrated to the Iongwall gob from overlying, and perhaps underlying, strata immediately adjacent to the panel and perhaps from greater distances downdip because of the establishment of a long-term pressure gradient in the study area.

Jan 1, 1992

By J. D. Dixon

The Bureau of Mines has developed structural design data for unreinforced concrete tunnel linings in the form of stress and deflection coefficients from which bending, axial, shear, and boundary stresses, moments, thrusts, and shear forces, and structural deflections can be determined at any point on the lining. Results were obtained by structural analyses of nine concrete-lined tunnel configurations subjected to 22 biaxial load conditions. The tunnel configurations include three basic shapes, circular, rectangular, and horse-shoe, with dimensions based on designs evolved by the mining industry. These analyses were made by the direct stiffness matrix method, a computer-oriented procedure. Numerical results agree closely with those obtained experimentally.

Jan 1, 1969