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By Robert W. Ageton

Optimal planning for mining the deep, lead-zinc-silver deposits of the Coeur d'Alene mining district, Shoshone County, Idaho, could be facilitated by a knowledge of the magnitude and direction of the pressure acting in the virgin rock. The distribution of primary stresses should be considered in order to prevent possibly destructive mining-induced stress concentrations. This particular investigation was concerned with determining stress in a zone 4,000 feet below the surface and known to be ender stress concentrations due to mining operations. Disking of the stress-relief cores obtained in a vertical down hole permitted qualitative evaluation from visual observations; the results indicate that a high lateral stress existed at the time the measurements were made. Stress-ellipsoid determinations gave a compressive principal stress of -13,000 psi oriented about N 45° W and nearly horizontal, a compressive principal stress of -11,000 psi oriented about S 45° W and abut 60° off the vertical pointing away from the vein, and a compressive principal stress -5 -7,000 psi oriented N 45° E and about 60° off the vertical, pointing toward the vein. Subsequent to the overcoring stress-relief drilling, a rock burst occurred about 100 feet northwest of the test site.

Jan 1, 1967

By W. R. Crane

Recent papers on support of roof and top rock in mines representing present practice in so far as it hits been described by engineers in all of the principal mining countries, cover a relatively aide range of topics. The papers abstracted herein include such subjects as the testing of materials of support, failure and movement of rock above workings, effect of excessive pressures on rock masses, axed the application in mines of timber, metal, concrete, packing, and filling support. It is not within the scope of this paper to present a logical and orderly discussion of the elements of support and their application to conditions influenced by the material worked or the method of mining. Only the essential facts of a paper appear in the abstracts, the idea being to give a fairly clear picture of the behavior of various types of support under brows conditions and to put into concise form important information concerning present practice, modifications of practice, and the trend toward new practice. With such valuable facts from others experience made readily available, it Is hoped that the engineer with particular and often trying problems may obtain suggestions that will be immediately helpful.

Jan 1, 1932

By V. L. Burdick

A literature review of current uses of Mn02 in ceramic applications with suggestions for future research. Historical background, oceanographic distribution, geology, exploitation, law and politics. Uses of Mn02 in ferrites, semiconductors, catalytic processes, thermo-luminescence and photochromic materials. Select bibliography of 33 items, plus 129 references.

Jan 1, 1980

By B. C. Parks

This paper is a report on the relationships between petrographic composition, chemical composition, physical properties, and thermal behavior of banded bituminous coal. It describes the relationships between petrographic composition, behavior in various laboratory tests, and carbonizing properties of different petrographic types of coal that occur in relatively thick benches in a single bed of high-volatile A bituminous coal - the Hernshaw bed of Boone County, W. Va. Thin-section microscopic analysis and free-swelling index determinations of the thin-section samples were made of a standard column sample. A standard face sample, a representative channel sample, and representative samples of two prominent petrographic benches of bright and dull coal were subjected to chemical analyses and free-swelling-index, plasticity, dilation, agglutinating, low-temperature carbonization, and BM-AGA retort tests. A float-and-sink separation was also made of part of the standard face sample. The fractions from this gravity separation were subjected to petrographic and chemical analysis and free-swelling-index, plasticity, and dilatation tests.

Jan 1, 1959

By A. E. Raddatz

In an attempt to develop technology to use domestic resources in place of imported bauxita, the Bureau of Mines investigated sulfurous acid leaching to extract alumina from kaolin. The process consists of leaching the calcined kaolin with a 30 wt-pct S02 solution at 60° C and 160 psig for 17 hours, fil¬tering the leach slurry, precipitating monobasic aluminum sulfite from the filtrate at 110° C and 60 psig, a& decomposing the sulfite in the spent liq¬uor at 150° C and 55 psig to produce crude alumina. Purification of the crude alumina was accomplished using a modified Bayer process. Results from closed-circuit tests employing the sulfurous acid process showed that overall extraction of alumina from kaolin was 67 pct. Production of 1 ton of alumina would require 3.6 tons of calcined kaolin, 0.7 ton of sul¬fur dioxide, and 8.4 tons of water. After purification by a modified Bayer process, the alumina product contained the following; impurities, expressed in weight-percent: Fa203, 0.009; S, 3.6; Si02, 0.07; Ti02, 0.002; K20, 0.017; and P205, 0.03.

Jan 1, 1981

To predict the spontaneous combustion potential of bituminous coals using a simple expression based on an easily acquired coal property. Background Approximately 20% of underground coal mine fires in the United States since 1978 have been attributed to spontaneous combustion. Spontaneous combustion fires in underground mines are most likely to occur in gob area; and are difficult to detect and to extinguish by direct fire fighting methods. Often, sections of the mine or the entire mine must be sealed for long periods, at a great economic loss to the mine operator, mine employees, and the surrounding community. It is conservatively estimated that the cost of scaling a large mine is about $50 million.

Jan 1, 1989

By W. A. Selvig

[THE BUREAU OF MINES receives many requests for information regarding the low-temperature carbonization properties of American coals. This report presents in collected form the results of Fischer-Schrader bench-scale, low-temperature carbonization assays at 500° C. made by the Chemistry and Physics Section at the Pittsburgh station of the Bureau of Mines. Most of the assays were made of coals tested in connection with a survey of gas and coke-making properties of American coals,4 which was started in 1928 by the Bureau in cooperation with the American Gas Association. Other coals were assayed in connection with miscellaneous investigations. Since 1930 about 400 samples of coal were assayed from nearly every coal-producing State, Alaska, and British Columbia, Canada. The results of the tests on about two-thirds of the coals are scattered through more than 50 separate publications. This paper summarizes the data in the published reports as well as all unpublished data obtained to January 1, 1956. The report also includes a detailed description of the procedure used in making the assay.]

Jan 1, 1957

By R. C. Gabler

Effective recycling or disposal of flue dusts is a continuing problem, particularly for secondary smelters treating low-grade Cu scrap. The Bureau of Mines investigated a variety of flue dust treatment approaches and demonstrated the technical feasibility of a bench-scale alkaline method that includes leaching, cementation, precipitation, and roasting. Flue dust was leached at room temperature with an alkaline solution of (NH4)2C03 and NHpH to solubilize ZnO and Zn metal. Some copper, lead, tin, and most of the zinc were dissolved in the leach step. Copper, lead, and tin were recovered in the cement product. The Zn in the flltrate was precipitated by pH adjustment to neutral using CO2 injection. The Zn salt was flltered from solution and roasted to give high-purity ZnO. The leach residue, enriched from 4.3 to lOA pct Sn, could find a ready market; the metallic cement product can be recycled back to the copper converter; and the high-purity ZnO product can be sold in several markets, leaving no material for disposal. The possibility for recycling of reagents, lower energy demand, and low environmental impact make this method economically and environmentally attractive for recycling secondary copper smelter flue dusts.

Jan 1, 1988

By Ellis S. Hertzog

The material published in this report is part of a special study of some of the chemical and physical properties of Alabama coals. The complete study included friability and grindability determinations, high and low temperature assay distillation tests, and ash fusion-temperature determinations. Proximate and ultimate analyses and. calorific values of the coal samples also were obtained. This paper is concerned only with grindabilities, although proximate analyses have been included to give a better picture of the problem as a whole. The growing interest in grindabilities of coals is a result of the increase in use of pulverized fuel in rescent years. The tenative ball-mill grindability method D408-35T4/ was used in making all the determinations. The method of sampling and the technic of the testing procedure is described in Considerable detail in this report because the procedure was established quite recently. The ball-mill grindability index is a measure of the ease with which coal may be ground, which may be an important factor in estimating pulverizing costs. Up to the present time few data on the grindability of Alabama coals have been published. The data in this paper show that the Warrior and Cahaba fields exhibit a wide range of grindability in their coals. The mines tested are well distributed throughout the productive areas of these fields, and it is possible to make rough estimates of the grindabilities of coals not listed in this report from the data given for mines situated in the same vicinity.

Jan 1, 1938

By Dwight L. Sawyer, Roy T. Sorensen

The Bureau of Mines has investigated the recovery of alumina by hydrochloric acid leaching of calcined kaolinitic clay . Bench- scale studies indicated that horizontal belt filtration was a pprraaccttiiccaall method for separating the siliceous residue from aluminum chloride liquor generated in the leaching step . Miniplant -scale continuous testing was performed to evaluate the filter circuits and to compare filtration response of different calcined kaolin feed materials and of different agitatorbaffle designs in the leaching reactors . Soluble alumina recovery with a single filter ranged from 94 pct with minus 10 -mesh feed more than 96 pct with minus 35-mesh or misted feed . Process advantages were confirmed for the calcined misted kaolin feed material prepared by a Bureau-developed misting process . With two filters in series , an overall filtration rate of 100 lb solids /hr.ft - 2 of filter area was attained with a soluble alumina recovery of more than 99 pct . More than 99.5 pct alumina recovery was obtained with a thickener and a two - filter circuit for either the minus 35-mesh or the misted feed . Modifications in leaching reactor design made to decrease particle- toparticle attrition were successful and significantly increased filtration rates and decreased flocculant requirements .

Jan 1, 1965

By Wallace W. Roepke

The Bureau of Mines studied the cutting characteristics of point-attack bits to reduce airborne respirable dust and energy during cutting. Linear cutting of two coal types using four bit types at three depths of cut with three space-depth ratios was performed with a modified horizontal milling machine using an optical particle-size monitor for respirable dust sampling. The cutting action of one bit on a rotary hardhead mining machine was mathematically analyzed and compared with the results of the linear cutting test. Airborne respirable dust per unit mass cut (specific dust) was found to be a monotonically increasing function of specific energy. Specific dust and energy decrease with increasing depth of cut. The amount of nonairborne respirable dust was 100 to 1,000 times greater than the airborne dust. The plumb-bob bit produced the most airborne respirable dust and the highest specific energy of the four bits tested. Rotary cutting was a greater dust producer and energy consumer than linear cutting because of the constantly changing depth of cut, space-depth ratio, and attack angle of the bit relative to the horizontal bedding planes. A new cutting technique is proposed to minimize the existing problems of the rotary cutting machines by providing greater production, reduced dust, and minimized methane ignition potential at the face.

Jan 1, 1976

By F. E. Walker

The Bureau of Mines determined total sulfur and sulfur forms for coal in 283 counties in 29 States and 2 fields of the State of Alaska. Specifically, organic, pyritic, and sulfate sulfur were measured of approximately 2,900 samples, and they include most of the coalbeds in the United States.

Jan 1, 1966

By A. Landsberg

Chlorination of sulfide minerals and several prepared metal sulfides was studied. The resulting data were analyzed with respect to kinetics of the reactions and application to nonpolluting methods of winning metals from sulfide ores. Sulfides of iron, copper-iron, nickel, lead, zinc, silver, bismuth, arsenic, rhenium, molybdenum, and tungsten were investigated at temperatures up to 600° C. Copper-iron, lead, and zinc sulfides showed at least some product-controlled (parabolic) kinetics at the lower temperatures within the temperature ranges studied, but only nickel and silver sulfides had chlorination rates controlled by parabolic reaction kinetics in the commercially important temperature range of 450° to 600° C.

Jan 1, 1975

By Steven J. Schatzel

Prior research has suggested that the source of respirable silica dust in underground coal mines is typically the immediate top or bottom lithology adjacent to the mined seam, not mineral matter bound within the mined coal bed. Geochemical analyses were applied in an effort to identify the specific source rock of respirable quartz dust in coal mines. The analyses also demonstrate the compositional changes that take place in the generation of the respirable dust fraction from parent rock material. All six mine sites were mining coal with relatively low mineral matter content, although two mines were operating in the Fire Clay coal bed which contains a persistent tonstein. Interpretations of Ca, Mg, Mn, Na, and K concentrations strongly suggest that the top strata above the mined seam is the primary source of mineral dust produced during mining. One site indicates a mixed or bottom source, possibly due to site specific conditions. Respirable dust compositional analyses suggest a direct relationship between the quantity of mineral Si and the quantity of quartz Si. A similar relationship was not found in either the top or bottom rocks adjacent to the mined seam. An apparent loss of elemental Al was noted in the respirable dust fraction when compared to potential parent rock sources. Elemental Al is present in top and bottom rock strata within illite, kaolinite, feldspar, and chlorite. A possible explanation for loss of Al in the respirable dust samples is the removal of clays and possibly chlorite minerals. It is expected that removal of this portion of the Al bearing mineral matter occurs during rock abrasion and dust transport prior to dust capture on the samplers.

Jan 1, 2009

By Robert E. Manning

At present, a need exists for more effective noise control in the coal-mining industry. In particular, new muffler designs with the required acoustic performance are needed for percussive pneumatic drills. Accordingly, the U. S. Bureau of Mines issued a contract to USS Engineers and Consultants to design a muffler capable of attenuating the noise from the air exhaust of a pneumatic drill. The specific objective of the contract was to design and deliver a prototype muffler that would attenuate the air-exhaust noise to 90 decibels on the A scale (90 dbA). The test drill used in this investigation was one used for roof-bolting purposes in coal mines. Using the combined approach of analysis by digital-computer program and experiment by simulated-noise tests, three prototype mufflers were designed and constructed at U. S. Steel Research. The mufflers consisted of a variety of resonator chambers and expansion-contraction chambers, and were of the following sizes: A muffler with a 3- by 5-inch elliptical cross section and about 8 inches in length. A muffler 5 inches in diameter and about 5-1/2 inches in length. A muffler 5 inches in diameter and about 10-1/2 inches in length. These mufflers were subjected to laboratory tests to determine their effectiveness in attenuating exhaust noise, mechanical noise, total drill noise, and simulated noise. All mufflers reduced the exhaust-noise level by about 25 dbA - from about 115 dbA without a muffler to below 90 dbA with a muffler - and thus were successful in meeting the contract objective. Field tests were conducted with the three prototype mufflers at U. S. Steel's Robena No. 4 Mine, and no icing problem was encountered. A fourth prototype muffler was designed to fit around the leg of the pneumatic drill. Tests showed that this kidney-shaped muffler also reduced the air-exhaust noise to below 90 dbA.

Jan 1, 1973

By Steven G. Grannes

This U.S. Bureau of Mines report summarizes Federal mandatory belt conveyor automatic fire suppression system installation requirements and inspection procedures, identifies system failure modes observed during in-mine investigations, and suggests system design and maintenance upgrades which, if implemented, would result in an improvement in overall system reliability. This report is a compilation of recommendations based on discussions with Mine Safety and Health Administration (MSHA) inspectors, review of manufacturer's literature, discussions with mine personnel, and research investigations of automatic fire suppression system performance in the laboratory and in mines. The Code of Federal Regulations (CFR) requirements for installation, inspection, and maintenance of fire suppression systems should be regarded as minimum standards.

Jan 1, 1990

By F. E. Walker

The Bureau of Mines determined total sulfur and sulfur forms for coal in 283 counties in 29 States and 2 fields of the State of Alaska. Specifically, organic, pyritic, and sulfate sulfur were measured of approximately 2,900 samples, and they include most of the coalbeds in the United States.

Jan 1, 1966

By Lloyd H. Banning

ELECTRIC smelting tests were conducted at the Northwest Electro-development Experiment Station, Albany, Oreg., to develop a feasible process for producing silicomanganese from siliceous manganiferous material. The Jackson County, Oreg., material used was massive and contained rhodonite as the most abundant mineral. Both raw and beneficiated materials were tested; various proportions and types of fluxes and reductants were used to make up the furnace charges. The silicomanganese product was used successfully in manufacturing various steels at industrial plants. The manganese content of the samples ranged from 23 to 28 percent; silica plus alumina content was as high as 55 percent-about four times the maximum specification for Metallurgical-grade ore. Sink-float laboratory tests indicated that the manganiferous material was amenable to beneficiation. Over 2 tons of rhodonite concentrate was prepared for smelting tests in a sink-float operation. Only the minus-3/4-inch, plus-8-mesh fraction was fed to a heavy-medium cone; over 97 percent of the manganese was recovered in the sink product, which contained 32.4 percent manganese and 44 percent silica plus alumina. About 25 percent of the silica was removed in the float product.

Jan 1, 1959

By W. D. Dietzman

This Bureau of Mines report presents a continuation of statistics pertaining to distribution of petroleum reservoirs (or fields), wells, and production by depth and producing rate classification in the United States. These statistics show the change that has occurred since results of a similar study were published by the Bureau of Mines in 1967. Data are presented in tabular form by State for the 18 principal oil-producing States and by subdivision for the two largest oil-producing States, Texas and Louisiana. Tabular summations and graphical illustrations are presented for the Nation. The data are classified by 4-barrel-of-oil-per-day rate increments up to 36 barrels and one increment of greater than 36 barrels of oil per day and by 2,000-foot depth increments up to 8,000 feet and one depth increment of greater than 8,000 feet. The overall average producing rates for States and the Nation have been published for many years, and although such rates are useful, they are very general descriptions of producibility. A breakdown of production, wells, and reservoirs by various depths and rates and by State or by State subdivision provides a more detailed description of producibility.

Jan 1, 1975

By M. J. Beus

Researchers at the U.S. Bureau of Mines have developed personal-computer-based data acquisition, instrumentation, and mine visualization and modeling techniques to evaluate a mine accessway in a deep hard-rock mine in northern Idaho. These techniques were applied to a mine shaft in a large silver mine that has been in operation for many years. A very deep, rectangular, timber-supported shaft extending to depths exceeding 2.3 km (7,500 ft) had been deforming continuously as a result of nearby mining, resulting in operational problems. Preliminary visual observations and rock and support monitoring confirmed that severe diagonal distortion was occurring. Extensive field measurements and data analysis confirmed initial observations, provided insights into the cause of deformation, and defined a general approach to structural modeling. Computer analysis of the problem was initiated by developing a three-dimensional model of the terrain. This represented a volume of rock approximately 80 km3 (40 x 1010 ft3) and an area on the surface surrounding the mine 9 km2 (3 square miles). Based on this model, a three-dimensional, finite- element analysis was conducted to establish boundary conditions for sequentially more detailed two- and three-dimensional submodels of the shaft area. Results from the computer study are being used to develop new approaches to mine design and to provide design guidelines for deep mine accessways subject to severe rock-mass loading conditions.

Jan 1, 2010