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By M. K. Larson, B. G. White

Researchers at the National Institute for Occupational Safety and Health (NIOSH) are investigating the causes and mechanisms of roof failure in underground mines. It is expected that a better understanding of these causes and mechanisms will lead to better layout and support designs that will help prevent accidents and fatalities associated with fall of ground. Two numerical experiments were conducted by NIOSH researchers using the Fast Lagrangian Analysis of Continua (FLAC) computer modeling program with a strain-softening continuum to simulate fracture zones. Two models, one of a round hole in a plate and one of a rectangular opening, were constructed and boundary conditions were applied to simulate far-field shear. The Particle Flow Code in Two Dimensions (PFC2D) computer program was used to look at the effects of far-field shear in generating fractures around an underground opening, but these models are preliminary until boundary conditions, strengths, and stiffnesses are matched to the FLAC models. Results showed that shear zones propagated from the opposite corners of openings in directions that appeared to be determined by opening shape and far-field stress. Tensile failures also formed and extended away from these shear zones. The consistent direction of shear deformation with respect to far-field shear provides a plausible explanation for preferred directions of shear as seen in geologic environments.

By Raymond M. Kacmar

This report presents the Bureau of Mines research on the hardware reliability prediction for two Bureau monitoring projects. The basic concepts of reliability predictions are introduced along with the reliability models and assumptions used for this particular evaluation. The results of the reliability predictions are for ground-fixed and naval-sheltered environments.

Jan 1, 1986

By Iam Pou Ng

Combustion aerosols consist mainly of elemental and organic carbon (EC and OC). Since EC strongly absorbs light and thus affects atmospheric visibility and radiation balance, there is great interest in its measurement. To this end, the National Institute for Occupational Safety and Health (NIOSH) published a standard method to determine the mass of EC and OC on filter samples. Another common method of measuring carbon in aerosols is the aethalometer, which uses light extinction to measure "black carbon" or BC, which is considered to approximate EC. A third method sometimes used for estimating carbon in submicron combustion aerosols, is to measure particle size distributions using a scanning mobility particle sizer (SMPS) and calculate mass using the assumptions that the particles are spherical, carbonaceous and of known density. With an eye toward evaluating the use of these methods for measuring carbon in freshly emitted diesel aerosols, the objective of this paper is to compare the results among these methods and to investigate the role of OC when measuring the mass concentration of elemental carbon (or black carbon) in aerosols emitted by a medium-duty Diesel engine. Results indicate that the aethalometer response correlates well with the data from filter samples (R2 = 0.99), with a very slight positive interference at high levels of OC.

Jan 1, 2008

By Thomas Varley

Data on the consumption of reagents used in .flotation during the year 1925, in metallurgical plants in the United States, are presented in this paper. Previous reports have covered the same subject for the years 1916, 1919, 1923 and 1924. The data contained herein show departures most radical from even the 1924 practice. Flotation has developed rapidly and on a more scientific basis than ever before. Perhaps more fundamental and useful data have been uncovered during the past two years than in all the years the art has been practiced.

Jan 1, 1926

By D. G. Kuehn

Studies were conducted by the Bureau of Mines to determine the positive ions and neutral species produced in glow discharges of gas streams containing 1.0 percent NO in helium, 29 percent dry air in helium, and 1.06 percent NO in N2, Mass spectrographic measurements were conducted for gas pressures from 2.3 to 10.0 torr and dc currents from 10 to 20 mAo Ion species observed included NO+, N2 +, O2 +, N+, and 0+ with lesser amounts of He+, He2+, and N02+. Variations in various ionic and neutral species with discharge duration were interpreted to be consistent with an electrically induced dissociation of NO to produce N2 and O2. No nitrogen oxides were observed to form in glow discharges of the helium-air mixture.

Jan 1, 1975

By S. H. Katz

"At the annual meeting of the International Association of Fire Engineers at Kansas City, Mo., in June, 1919, the Bureau of Mines offered to cooperate with municipal fire departments for the purpose of obtaining information regarding composition of the air in burning buildings. (Katz, S. H., Statement made at Convention of International Assoc. of Fire Engineers: Fire and Water Eng., vol. 66, July 16, 1919, pp. 129-30, also Fireman's Herald, vol. 78, July 12, 1919, pp. 48.) The gas-mask laboratory of the Bureau's experiment station at Pittsburgh sent vacuum bottles for taking samples to fire chiefs in twenty-five cities, who had signified their intention to aid in this work. It was hoped to obtain one hundred or more samples, because statistics in quantity are necessary for drawing reliable conclusions concern-in the likelihoods of encountering irrespirable as in burning buildings. This far, eleven samples have been received by the laboratory. Results of analyses and pertinent data regarding these samples are given in the accompanyingEight of the eleven samples contained, no carbon monoxide; seven of the eight were taken above the ground level and one below ground. One sample taken above ground contained 0.03 per cent carbon monoxide, and this quantity is not dangerous to breathe for a limited time. Of the three samples taken below ground, one contained no carbon monoxide; the other two contained 0.10 and, 0.35 per cent, respectively. This indicates that in a burning building, the hazard from carbon monoxide is much greater below the ground level. The cause undoubtedly lies in the poorer ventilation that is usually found in cellars or basements. Abundance of ventilation provides the necessary air for complete combustion, or if incomplete combustion does occur, the carbon monoxide generated by the fire is greatly diluted with fresh air and swept away by the current. It may be noted that the highest proportion of carbon monoxide was found in a cellar where a fire as burning among piled cases. The difficult access of air to the burning parts facilitated the formation and lib ration of carbon monoxide. The smoke here was very light and no difficulty was experienced in breathing. Some of the air containing dense smoke showed little change from normal air by analysis. Thus the density of smoke or the irritation and difficulty it causes in breathing are no indication of the presence of poisonous gas. None of the samples shows important oxygen."

Nov 1, 1920

By E. J. Kloos

The Bureau of Mines devised a new machine-test method for measuring carbon dioxide inspired by a wearer of self-contained breathing apparatus. The new method compares favorably in speed and precision with standard man-tests in which the apparatus is tested while actually worn, and is scheduled for use in future approval tests for facepiece carbon dioxide 'measurements. However, man-tests will still be used to measure the efficiency of the carbon dioxide sorbent materials in closed-circuit breathing apparatus.

Jan 1, 1966

By Charles L. Kimbell

In broadest overview, a substantial part of the world's mineral industry in 1990 registered small gains over its 1989 performance, but traditional statistical measures of mineral industry performance, namely global production, trade, and consumption levels, failed to mirror these gains. This was because of the sharp downturns in the mineral industry activity in the U.S.S.R. and the former centrally planned economy nations of eastern Europe. These downturns in this one geographic area had influences on almost all traditional statistical series, in some cases simply significantly reducing growth, in other cases providing for a global downturn, in almost all cases despite considerably brighter outlooks based on activities in other world areas. To be sure, the U.S.S.R. and eastern Europe were not the only places on the planet suffering problems of one type or another in 1990 that impacted on minerals industry activity, but with the acquisition of information presently available, it seemed almost assured that the difficulties of these economies in transition will be the most difficult of problems to resolve in the long run. It certainly appeared that the legacy of the half century or more of economic central planning will be a decade or more of very difficult adjustments, and a number of these will greatly affect not only the minerals industry of these transition countries, but also the rest of the globe's mineral industry as well.

Jan 1, 1993

By P. C. Good

The work reported here was undertaken by the Federal Bureau of Mines to investigate new methods of preparing high-purity metal. Tungsten hexachloride was prepared by direct chlorination of scrap tungsten metal and by treating tungstic oxide with carbon and chlorine. The resulting tungsten hexachloride was purified by distillation and reduced win: sodium, magnesium, or hydrogen. The metal prepared by these techniques was at very high purity after arc melting but of variable quality prior to arc meIting. Metal recovery ranged from about 40 to 90 percent of theoretical values, It was found possible to deposit a smooth, dense coating of high-purity tungsten on the inside of a heated tube by vapor-phase reduction of tungsten hexachloride at reduced pressure.

Jan 1, 1961

By Martin Hertzberg

The Bureau of Mines 8-liter flammability system was used to study the effectiveness of a variety of powdered inhibitors in preventing the propagation of explosions of coal dust or methane in air. Over 35 different chemical additives were evaluated against Pittsburgh seam pulverized coal. The least effective inhibitors were the carbonates, which required mass additions in the range of two to three parts inhibitor to one part of coal dust in order to prevent propagation. The most effective inhibitors were the derivatives of ammonium phosphate, which were effective quenching agents at additions of only one part inhibitor to four parts of coal dust. Alkali halide powders were of intermediate effectiveness. These laboratory-scale results are in good agreement with full-scale mine experiments in all cases where detailed comparisons have been made. Data were also obtained for the effectiveness of several of the same powdered inhibitors against methane-air explosions. Their relative order of effectiveness and the concentration ranges required for quenching the gas explosion are comparable to those measured for coal dust explosions. Data are also presented for the effectiveness of N2 and CF3Br addition. Some preliminary data are also presented for powder addition to methane burner flames. Those data are compared with other burner data and evaluated in terms of their relevance to explosion tests.

Jan 1, 1982

By Nicholas P. Kripakov

The U.S. Bureau of Mines examined the applicability of existing material models to solve practical geotechnical mining-related problems by solving a yielding pillar stability problem considering confining effects on strength. Numerical difficulties normally encountered with modeling strain softening behavior were eased with a simplified computational procedure using a quasi-elastic approach to account for residual strength after initial failure. Although in agreement with a confined-core pillar design method using actual mine conditions that include mine layout geometry, overburden geology, and rock properties of the deposit and surrounding structure, the results cannot be verified because measured field data are not available at this writing.

Jan 1, 1981

By F. A. Rutledge

The Rainy Creek deposits lie at the western base of the Kilbuck Mountains, about So miles southeast of Bethel, in southwestern Alaska. The deposits were brought to the attention of the Bureau of Mines by placer miners on Rainy Creek after cinnabar concentrates were recovered by their gold-mining operations. In August 1947 the Bureau excavated 1,500 feet of dozer trenches totaling 2,547 cubic yards. Further hand trenching in the bottoms of the dozer trenches on the surface totaled 1,440 linear feet, or 40 cubic yards. Nineteen samples were taken for analyses.

Jan 1, 1948

By N. F. Le Jeuns

For a number of years the Bureau of Mines has conducted semi-annual surveys to determine the changes in motor gasoline being sold in the United States. It was pointed out in the previous survey that there was an apparent tendency toward greater uniformity in the character of gasoline marketed in the United States. This practically uniform tendency which continued from April, 1917 to January, 1923, has been interrupted in the, present survey, as shown by an examination of the column marked "Difference," as given in Table 1. The figures in this table were obtained by averaging the end points of the least volatile and most volatile samples of gasoline. For example, of 850 samples analyzed in 1919, the 10% ,(85 samples) having the highest end points and the 10% having the lowest end points mere grouped, and the end points of each group averaged. These averages are represented in the table as the "Maximum 10%" and the ?Minimum 10%? respectively. The same process was used on the other surveys.

Jan 1, 1923

By J. C. Nigro

Hematite-to-magnetite reduction kinetics were investigated mainly in CO-CO2 atmospheres at temperatures ranging from 500° to 1,000° C. Reduction rates were measured with a thermobalance, which recorded the weight loss as the specimen was reduced. Reduction data on both synthetic and natural hematite spheres showed good linearity of ro [1-(1-R)1/3] with time, t, up to over 85 pct conversion to magnetite; the rate coefficient (k[L], cm/min) obtained from the linear portion of the plot was used to characterize the penetration rate of the hematite-magnetite interface. Gas composition, porosity, and silica content were major factors affecting the rate. Temperature dependency of the reaction rate was small, yielding a mean activation energy of about 3 kcal/mole. Silica additions increased the reaction rate, probably through an increase in the effective surface area and diffusion; however, above 900° C, silica can react to form fayalite. Experimental data showed that the linear thickening rate of the magnetite layer, normally evidence of a chemically controlled reaction, can also be indicative of a reaction controlled by both mass transfer and diffusion. Evidence from this study indicates that the dominant rate-controlling factor in the reduction of hematite to magnetite at high temperatures is transport in the gas phase.

Jan 1, 1973

By Paul T. Allsman

SCIENTIFIC inquiries concerning phenomena that may influence mining technology were widely publicized during the year. The deep-hole drilling project "Moho," 3 the use of nuclear explosives underground, and the recovery of minerals from the depths of the sea became subjects of scientific and general discussion. The mining industry continued to watch these developments with keen interest: but its more immediate concern was the increasing tempo of competition between mineral commodities, the domestic producers of these commodities, and foreign sources of supply. The competitive situation has intensified the industry's efforts to develop more efficient new mining methods, as well as to improve the efficiency of present practices. The attitude of the industry was well illustrated by rapidly expended use of low-cost ammonium nitrate explosives, the establishment of rigid schedules for equipment maintenance, and close attention to the detailed costs of production. The complexity of planning a new coal mine is aptly illustrated by the editors of Mechanization in the April 1959 Issue, in which they outline the cost of developing a mine and the various problems, factors, and decisions involved.4

Jan 1, 1960

By R. L. Anderson

Mechanical cleaning of bituminous coal in the United States was begun about 1875, with plants in western Pennsylvania and Illinois. The United States Geological Survey began to record the quantity of washed bituminous coal in 1906; and the series was carried forward to 1923, except that no data were collected, for 1922. This statistical work was transferred to the Bureau of Mines in 1925, and the collection of data on mechanical cleaning was resumed in 1927. Data collected before 1927 include only the coal that was washed at the mines and do not include that cleaned by pneumatic methods at the mines and that cleaned at central washeries operated by consumers.2/ The total bituminous coal washed in 1906 was less than 10 million net tons. In 1927, the first year for which complete figures are available for all types of mechanical cleaning, 28 million net tons of bituminous coal were cleaned in the United States.

Jan 1, 1951

By Harold R. Newman

The performance of Ecuador's mineral industry continued to be affected not only by depressed oil prices in recent years but also by natural disasters. In March 1987, Ecuador canceled foreign debt payments for the rest of the year and appealed for international aid because of a series of earth-quakes that destroyed villages and crippled the nation's oil industry. The earthquake destroyed a key section of the country's main oil pipeline and forced a halt to production and shipment of Ecuador's most important export product. Ecuador produces 240,000 barrels of oil per day and exports 144,000 barrels daily. Oil accounts for 60% of the nation's hard currency earnings. The Government of Ecuador asked the Organization of Petroleum Exporting Countries and other oil-producing countries to assume Ecuador's oil sales commitments. Ecuador agreed to pay the countries back in an equivalent amount of oil when it was able to resume exports.

Jan 1, 1989

By Maust. E. J., W. R. Crane

"IntroductionIn the study of mine drainage in the red iron ore mines of the Birmingham district of Alabama, an extensive series of measurements were made in order to determine the drainage from the area overlying and adjacent to the mines. Gaging rods were generally used in measuring streams, and weirs in ditches and sometimes as a check on rod work. These tests in turn were checked by current meter tests. In all, 725 separate stream gagings and 97 weir measurements were made. Certain relationships were worked out, particularly between rod and weir tests, which permitted obtaining results that are much more accurate 'under the existing conditions, than any available formula would give. The large number of weir measurements and the period covered by the tests made it impracticable to construct a weir for each observation so portable, adjustable weirs were built. The methods used are described here for the benefit of those interested in measurement of streams in connection with a study of mine drainage or otherwise. The Drainage AreaThe area draining the mining district lies between the crest of Red Mountain and Little Shades Creek, and for convenience was divided into sub-districts adjacent to certain groups of mines. Gaging stations were established on Little Shades Creek at the upper and lower boundaries of each sub-district, also at points on the tributaries near their junction with the creek. The difference between the volumes of water flowing in Little Shades Creek as it entered and left the sub-districts represents the flow from the tributaries on both sides of the creek. Since the flow coming from the sub-districts was measured direct, the inflow from the tributaries on the opposite side of the creek can be computed from the three volumes determined."

Oct 1, 1926

By Gregory P. Cole, Jeffrey Shawn Peterson

The Pittsburgh Research center3 conducted research to study and improve electrical fault detection on coal mine direct-current (dc) trolley systems. A suspended trolley line delivers power at voltages of 300 or 600 V dc to the haulage equipment and other loads. Roof falls or other accidents may force the trolley line down so that an electrical fault current may flow between the trolley line and rail. This fault current could result in localized heating, arcing, and perhaps fire. Such faults are not always preventable by the existing circuit protection because the current magnitude is well below typical operating levels of the trolley system. The research discussed in this report studies the applicability of computerized signal analysis techniques to solve this problem. Tests were conducted at cooperating coal mines. Measurements were taken during normal loading of the trolley system (light, intermediate, and heavy traffic), during induced fault conditions (arcing and bolted faults), and during transitions between the two. These data were then used to train and test a microprocessor-based fault detection algorithm. Later, field tests of the detection algorithm found that it correctly classified the state of the trolley system greater than 95% of the time.

Jan 1, 1997

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