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By Clarence O. Babcock

Model pillars of limestone, marble, sandstone, and granite with length-to-diameter (L/D) ratios of 3, 2, 1, 0.5, and 0.25 (0.286 for granite) were tested to failure in axial compression to determine to what extent an increase in end constraint increased compressive strength. Adjustable steel rings, mechanically tightened about the ends of test specimens to create a radial prestress of 3,000 or 5,000 psi prior to the application of axial load, increased end constraint more than was possible in previous tests using solid steel rings. (Solid rings, epoxy-bonded to the ends of dogbone specimens, increased compressive strength compared with that of straight specimens without ring constraint.) During the loading cycle, additional end constraint was produced by lateral expansion of the specimens against the rings. The effect of the end constraint was to increase the compressive strength 55 to 58 percent for the shorter pillars of dogbone shape compared with the compressive strength of straight pillars with the same L/D ratios without ring constraint. Most pillars with L/D ratios of less than 2 were made stronger by end constraint. Pillars with an L/D ratio of 3 did not benefit significantly from end constraint. When the results from compression testing of straight specimens of rock in the laboratory are used to design mine pillars in situ, the pillars will be larger than necessary if the horizontal compressive stress is several thousand pounds per square inch greater than that resulting from the weight of the overlying rock alone. The L/D ratio can be increased by a factor of 1.76 for ratios in the range 0.25 to 3 and still provide the same compressive strength. The safety factor applied with straight specimen test results should also be acceptable for use with constrained pillar test results.

Jan 1, 1969

By S. M. Shelton

The widespread occurrence of domestic manganese deposits and the shortage of ferromanganese-grade ore have been sources of much speculation and investigative effort for many years. The present emergency has intensified the search by the Bureau of Mines for methods of producing ferromanganese-grade concentrates4/ from low-grade ores.

Jan 1, 1941

By E. R. Maize

[he scconG rcport of :his st?rI.org 8cdt with o3servatioi:s of conver- gence of roof an4 floor at t!x*re: ?.cc.-.tioris iri til~ ClVucible mine of kke Cru- cib1.o Fuel Co. Data on sl:'ociacnce ?.rd Lztcrcl mwe:~cnt cf the surface were .:lven for two of these areas, a-12 it was mentioned that ~lr~~ilar data were being obtained on a ?art of Pe:sc:rlvtzr.ia Fii~l?trr.y FE:, ~i!lic;l pcser: over the third area. 'I'hie hichw~ :LEO FasseE over t!lc ITenncoli::. :.line of the Bnckeye Coal Co. 9 milcs to ';he so-lth, cnd at P. l~tcr C'..att: ~.nr?r.,cc?r:cntS *.rere mnd.e to make similar observati on3 there. This y: pr mrnmri:.c n Czto obtnino? at those two locetionn,]

Jan 1, 1941

By L. C. IlsLey

Many accidents rightly classifiable as electrically caused are not so classified for the reason that in numerous accidents the part that electricity played in causing the fatality is only suspected. For instance, a workman might receive a shock that would cause him to lose his balance and fall beneath a trip of cars; if no one saw the first part of the accident, the cause undoubtedly would be charged to "haulage." This paper covers a brief study of fatal and nonfatal electrical accidents. The first usually result from direct contact with the electrical circuit or electrical apparatus; the second more often are the result of arcing or flashing due to handling defective apparatus or making repairs on "live" equipment or circuits. It is hoped that helpful suggestions may be offered for minimizing accidents of these two classes.

Jan 1, 1938

By W. R. Crane

Subsidence and ground movement are phenomena common to and attendant upon practically all large-scale mining operations, and under certain conditions may occur in all workings, large and small. The interpretation of the cause of failure in rock masses involves a study of the nature of plants of weakness common to all rocks. The dominating planes of weakness can readily be determined by observation in any given locality, and in order of importance in the study of subsidence are (1) faulting planes, (2) bedding planes, (3) joint planes, and (4) other prominent planes of weakness such as thrust and shear planes and contacts. This report has mainly to do with the third item, joint planes, and is a preliminary statement which t to be followed by a more complete report in bulletin form.

Jan 1, 1931

By D. L. Boreck

Thick coal seams are common in the Western United States, Many seams are over 50 it thick (some are over 200 ft thick) and are too deep to extract using surface methods. Currently, such deposits are developed using standard "eastern" mining methods which only extract a few feet of total seam thickness, often rendering the remaining coal unminable with current technology. Novel methods that increase thick-seam recovery have been developed and are currently being used in Europe. These methods--high-face single-pass and multislice longwall, longwall caving, and hydraulic mining--have great potential for use in the United States. Successful use of these methods is an objective of the Bureau of Mines. Their use requires, among other things, a full evaluation of geologic features common to thick coals. The objective of this report is to present and summarize those features that will affect the introduction of the methods into thick-seam mines in the Western United States. The geologic elements delineated are three-dimensional configuration of the seam, cleat development, joints and fractures, roof and floor lithology, and faulting.

Jan 1, 1986

By John K. Owens, Wayne L. Howie

Mobile roof support (MRS) machines are used as roof support during pillar recovery in retreat operations in lieu of wooden posts, cribs, or hydraulic props. A Mine Safety and Health Administration-permissible load rate monitoring system was developed for the MRS by researchers at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health. The system uses a dedicated embedded processor to monitor changes in pressure inside the hydraulic cylinders of the MRS through multiplexed data acquisition channels and converts these pressure changes to load rates that sequentially activate three load-rate-indicator lights mounted on the machine. Each light represents a different loading rate to alert mine personnel to dangerous conditions during pillar extraction.

By N. S. Dalal, X. Shi

"Electron spin resonance (ESR) measurements on solutions and isolated powders provide direct evidence for the involvement of Cr(V) species in the reduction of Cr(VI) by NAD(P)H. ESR analysis of an isolated Cr(V)NAD( P)H solid yields 6 11 = 1.9831 and 6.i. = 1.9772, indicating that the unpaired electron occupies the d22 orbital of the Cr(V) ion, with square-pyramidal geometry. Addition of hydrogen peroxide (H2 0 2 ) to the N AD(P)HCr( VI) reaction mixtures suppresses the Cr(V) species and generates hydroxyl (""OH) radicals. The ""OH radicals were detected via ESR spin trapping, employing 5,5-dimethyl-1-pyrroline-N-oxide and a-(4-pyridyl-1- oxide)-N-tert-butylnitrone as spin traps. The dependence of Cr(V) and ""OH radical formation on the H20 2 and Cr(VI) concentrations indicates that the Cr(V) species react with H20 2 to generate the ""OH radicals. Similar results were obtained by using various diols (arabinose, cellobiose, FAD, fructose, glyceraldehyde, ribose, and tartaric acid), a-hydroxycarboxylic acids, and glutathione. Investigations with superoxide dismutase showed no significant participation of 02 in the generation of OH radicals. These results thus indicate that the Cr(V) complexes, produced in the reduction of Cr(VI) by cellular reductants, react with H20 2 to generate ""OH radicals, which might be the initiators of the primary events in the Cr(VI) cytotoxicity.In this paper we report an electron spin resonance (ESR)3 spectroscopic detection of Cr(V) species in the reduction of potassium dichromate, henceforth called Cr(VI), by NAD(P)H and other diols. Also reported here is the detection of the hydroxyl (""OH) radical in the reaction between hydrogen peroxide (H2O 2) and a variety of Cr(V) complexes. This work was undertaken because while the reduction of Cr(VI) to lower oxidation states has been suggested as a key step m the mechanism of Cr(VI) toxicity, mutagenicity, and DNA alteration, the details are not yet clear (1-5).Earlier studies on the mechanism of Cr(VI) reduction in cellular systems include those on the reduction of chromate by microsomes (6-8), rat liver DT-diaphorase (9), and aldehyde oxidase (10). All these studies imply that Cr(VI) can be reduced to Cr(Ill) by cellular constituents. Regarding the mechanism of Cr(Vl) carcinogenicity, Jennette postulated that Cr(V) is the ultimate carcinogenic form of chromium compounds (8). This conclusion has led to many further investigations of the formation of Cr(V) in the reduction of Cr(VI) under biologically relevant conditions (11-33). More recently, however, Kawanishi and co-workers (34) have investigated the mechanism of DNA cleavage induced by Cr(VI) in the presence of H20 2 and have argued that it is not Cr(V) itself that is carcinogenic, but it is the reactive oxygenated species (02, 10 2 , ""OH) (produced by the decomposition of the Crv(02) ¾ - ion) that cause the DNA alteration."

Jan 1, 1990

By D. D. Southworth

In 1981, 1982, and 1983, the Bureau of Mines examined the potential for lode deposits of platinum-group metals (PGM) in the Goodnews Bay ultramafic complex, Alaska. The complex consists of the Red Mountain, Suzie Mountain, and Smalls River ultramafic bodies and displays concentric zoning of rock types similar to complexes in southeast Alaska, British Columbia, and the Ural Mountains in the U.S.S.R. Results of the study indicate that platinum is preferentially associated with chromite and magnetite in the dunite core of the complex, and palladium is preferentidlly associated with sulfide minerals in the outer clinopyroxene-rich zones. the most promising targets for PGM lode deposits are the chromite-rich dunite at the heads of Fox Gulch and Squirrel Creek and iron-nickel and iron copper sulfide-bearing magnetite clinopyroxenite and hornblende-rich rocks outward of the dunite core, also in the Fox Gulch-Squirrel Creek area. Significant placer reserves are present in the unmined, deeply buried placer ground in the lower Salmon River Valley, and also in tailings from previous dredging.

Jan 1, 2011

By Steven J. Page, William A. Heitbrink, Andrew B. Cecala, Edward D. Thimons, John A. Organiscak

Miners at noncoal surface mining operations are often exposed to high levels of respirable dust. In an effort to lower the respirable dust exposure of these surface miners, the National Institute for Occupational Safety and Health (NIOSH) has been conducting research to address this problem in a practical and economically viable manner. One successful effort deals with lowering the dust exposure of equipment operators in enclosed cabs. Many types of surface mining equipment utilize enclosed cabs to protect equipment operators from dust exposure. Normally when the equipment is new, the cabs are fairly airtight. These tightly sealed cabs, combined with good filtration systems, generally provide the operator with good dust protection. However, most mining equipment is older, and as aging occurs, many components of the enclosure deteriorate. The structural integrity of the cab diminishes and the effectiveness of the air filtration system fails. NIOSH has been successfully researching costs-effective methods to improve both filtration effectiveness and cab integrity of these older cabs in order to provide a healthier work environment for equipment operators. Dust sampling records indicate that drill operators and helpers have the highest dust exposure of all workers at surface mining operations. Since much of the overburden contains a high percentage of silica, the health hazard associated with this dust can be even more serious. NIOSH research is addressing techniques to lower respirable dust levels at surface drilling operations. INTRODUCTION NIOSH's mission is to assure a safe and healthy work environment for the working men and women of this nation. The primary emphasis of NIOSH's Pittsburgh Research Laboratory (PRL) is mining health and safety research. This report focuses on two areas of research

By M. John Brodie

This report reviews the regulatory environment as it pertains to tailings management and disposal from mining operations, excluding coal and placer gold operations, in the state of Alaska. It is based on the EPA's staff position on an effective program to regulate mining wastes as presented in the May, 1990 Strawman II document, The unique conditions which occur in parts of the state, including a fragile environment, high seismicity and permafrost, are identified. The special waste management practices which are necessitated by these conditions are delineated. The report provides a detailed outline of the current technologies that are suitable for designing, constructing, operating and closing a railings disposal facility to meet environmental protection objectives. Cost implications to the mining industry of potential regulatory actions, such as the degree of groundwater protection are examined.

Jan 1, 1992

By C. A. Taylor, C. E. Munroe

"In blasting the explosion of the high explosives charge is initiated by means of a detonator. Consequently the successful operation of the whole system is, ab initio dependent upon the suitability and efficiency of the detonator used. A considerable number of methods for testing the efficiency of detonators have been devised. In a previous publication*** of the Bureau of Mines many of these were discussed after having been classified as direct and indirect methods.In 1910, W. O, Snelling, then explosives chemist of the Bureau, devised a direct method which depends on the extent to which a hard brittle material of uniform granulation, such as quartz sand, is pulverized by the explosion of the detonator when imbedded in it, and, as a container in which to carry out the tests, he devised the vessel known as the Bureau of Mines sand-test bomb No. 1. A brief mention of his work was made in a paper presented to the Engineers' Society of Western Pennsylvania.****Later Storm and Cope made a very extended investigation of this method using sand-test bomb No, 1. Their paper***** contains a detailed, illustrated, description of sand-test bomb No. 1, with precise specifications of the sand and a minute account of the technique followed, together with a discussion of the data they obtained from the tests in this bomb of 112 detonators representing each of the grades from We, 3 to No. 10, inclusive. The average of results obtained by them are set forth in the following table."

Dec 1, 1923

By Andrew W. Berg

The Bureau of Mines Mineral Industry Location System (MILS) is part of the computerized Minerals Availability System (MAS), a comprehensive data base of known mineral deposits. MILS, the location subsystem of MAS, has become widely used by the minerals industry and organizations with land-use planning and land management responsibilities. Information on more than 135,000 mineral locations and processing plants in the United States is contained in the data base. This information includes the name, location, mineral commodity, type of operation, bibliography, and cross-references for each property or prospect. Computer-drawn map overlays at various scales showing clustered MILS locations and computer printouts keyed to those overlays are available for inspection and reproduction at the Bureau's Field Operations Centers at Juneau, Alaska, Denver, Colo., Pittsburgh, Pa., and Spokane, Wash.

Jan 1, 1979

By Andrew M. Leszcykowski

In 1984, personnel from the U.S. Bureau of Mines examined 41,550 acres of the North Fork Owyhee River Wilderness Study Area for mineral resources. This study area, in southwestern Idaho, is underlain by tuffs and basalt of Tertiary age. There are no known mines, claims, or prospects in or near the area. The northeast and southwest corners of the area are covered by oil and gas leases or lease applications, but no known exploration has been conducted. On Nickel Creek and Pleasant Valley Tables, in the southern part of the area, thin flows of vesicular, moss-covered basalt occur that are suitable for use as decorative building stone. The stone available for exploitation crops out over several square miles. However, more suitable material, outside the study area, is closer to potential markets.

Jan 1, 1986

Provide means for rapidly re-establishing ventilation control in metal mines after blasting, for emergency applications, and for routine temporary use. Approach Two quickly-installed, parachute-like stoppings have been developed and tested by the Bureau's Pittsburgh Mining and Safety Research Center. How the Parachute Stopping Works The parachute stopping can be fastened to an existing anchor point, opened, and effectively block the air flow, in less than two minutes. Because the parachute stopping tends to be self-scaling, its performance is generally better than that of conventional fabric stopping. However, the periphery of the parachute stopping must be longer than the periphery of the mine opening, Figure 1 shows the parachute stopping deployed in a mine entry. To reduce leakage during routine use, the cloth at the periphery of the parachute stopping can be adjusted and then anchored at several points as necessary. This extra adjustment can also be done after the initial installation during mine rescue or mine recovery.

Jan 1, 1977

By Gary J. Cwick

Mineral resources of the Rice Valley Wilderness Study Area (WSA), in the Mojave Desert of southeastern California, were investigated by the U.S. Bureau of Mines and U.S. Geological Survey during 1980. The study consisted of an examination of mines, prospects, and mineralized areas by the Bureau: of Mines and geological, geochemical, and geophysical investigations by the Geological Survey. Little indicated potential for the presence of mineral resources exists in the valley floor segment of the study area. The Big Maria Mountains section of the study area has some potential for mineral resource development. Decorative building stone from both bedded quartzite deposits and weathered limestone surface rubble (driftwood stone) has been produced from the Big Maria Mountains segment of the study area. Total production is unrecorded but probably small. A 700,000 ton (640,000 t) quartzite resource was inferred and 4,500 tons (4,100 t) of driftwood stone within the study area was estimated. A relatively pure limestone deposit inside the study area contains an inferred resource of 14 million tons (13 million t). One prospect suggests a potential for the presence of manganese resources although none were estimated. The likelihood of discovering oil, gas, coal, uranium or geothermal energy is low; potential sources are not known to exist.

Jan 1, 1982

Improve surface mine haul-age truck safety and efficiency by providing a means for sensing the weight and distribution of the truck's load. Approach The safety hazards and the economic implications of overloading mine-haulage trucks were analyzed to determine the net effect of that practice on mine operations. The analysis indicated that: Ten to 25 pct overloading is typical; Higher haulage, tire, and maintenance costs occur due to overloading (a 20 pct overload was estimated to increase operating costs 7 pct per ton); Ten to 15 pct of haulage? truck injuries and fatalities are attributable to overload conditions, at a cost over one million dollars per year to the mining industry. Vehicle-weighing technology that conformed to the performance specification for an off-highway haulage truck overload detection system was selected for in-mine testing. How It Works Normally, volumetric estimates are made during the loading sequence which do not account for the varying ore density. Hence, the actual weight of a load is never precisely known. By providing a precise measurement, an overload detection system will not only indicate vehicle overloading, but will also show under-utilization of the truck. One system tested by the Bureau of Mines was the ?Load Analyzer" manufactured by Pactronics Corporation in California. This system consists of a meter-type analog readout for the cab console and three "Electrosensors" (linear variable differential transformers) attached to the main frame. Using conventional welding and brazing techniques, two sensors are attached between the front members of the engine sub-frame and the top of the left and right trailing arms (one sensor per arm). The same techniques are used to attach the third sensor to the rear centerline of the truck. between the main frame cross member and the A-frame. The readout unit on the cab console indicates by color-coding whether each sensor loading is under (green), at (yellow), or over (red) the pre-set rated load. The three-sensor configuration with in-dependent readouts also detects uneven distribution of the load.

Jan 1, 1984

By Edward L. McHugh

Twelve properties in the Riverside Mountains have moderate to high potential, for silver, gold, copper, and molybdenum. Six properties in the Big Maria Mountains have moderate potential for zinc, lead, copper, silver, iron ore, and limestone. The Big Maria Mountains also have occurrences of building stone. Four properties in or near the study area have low-grade gold-silver-copper resources totalling more than 300 thousand tons (270,000 t). An estimated 29 million tons (26 million t) of limestone and dolomite, and 620,000 long tons (630,000 t) of iron ore are in the Big Maria Mountains section of the study area. INTRODUCTION The Big Maria Mountains Wilderness Study Area covers about 50,538 acres (20,453 ha) near the Colorado River in eastern Riverside County, California (fig. 1). The study includes portions of both the Big Maria and Riverside Mountains. It lies north of Blythe, California and south of California Highway 62 in the Mojave Desert province of the California Desert Conservation Area. The study area consists of two mountain ranges surrounded mostly by broad alluvial slopes or bajadas. It extends for 25 mi (40 km) from the Riverside Mountains on the north, to the south end of the elongate Big Maria Mountains.

Jan 1, 1982

By D. F. Smith

The thermodynamic data presented in the literature for zirconium compounds are incomplete. Among the compounds for which adequate data are Zacking are zirconium fluoride and sulfate. This paper reports experimental heat-content values determined by the Bureau of Mines for these two zirconium salts throughout the temperature range of 273° to 1,200° K. No crystalline transformations were found in the two compounds investigated, and neither of the compounds melted over the temperature range studied. MATERIALS TESTED The Oak Ridge National Laboratories, Oak Ridge, Tenn., supplied the two zirconium salts used in this investigation. The zirconium fluoride was high- purity reactor grade material. The zirconium sulfate contained between 0.01 and 0.10 percent hafnium and calcium, and other elements in concentrations below 0.01 percent, A spectrographic analysis of the two compounds is given in table 1. Before use the compounds were dried at 400° C. for several hours to removed adsorbed moisture.

Jan 1, 1962

By W. H. Ode

Low-temperature distillation tests at 200°, 350°, and 500° C. were made on a subbituminous coal from Boulder County, Colo., and a subbituminous coal from Weld County, Colo., in connection with a survey of carbonizing properties of American coals and investigations of their chemical and physical properties. The coal represented by the sample from Weld County was reported to give off combustible volatile matter at unusually low temperatures When placed on a fuel bed. The yields of tar and oil and the composition of the gas from this coal, as obtained in the distillation tests, did not confirm this report. These yields and the gas composition of the Weld. County coal differed but little from those obtained from the coal from Boulder County. Both coals yielded tar and gas in amounts considered to be normal for coals of their rank.

Jan 1, 1937