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It is now widely accepted that horizontal stress is present nearly everywhere underground. Often it is more severe than the vertical stress. It is a major cause of roof control problems in underground mines. The AHSEM computer program contains two modules to improve mine layouts for control of horizontal stress. For development, the user specifies the orientations of the maximum horizontal stress, the entries, and the crosscuts. Angled crosscuts may be used, and the angles may be different for the right- and left-hand crosscuts. AHSEM then shows the user how the stress condition would vary as the entry and crosscut orientations are changed. The second module is for longwall mining. Severe stress concentrations can make headgate conditions hazardous when the entries are improperly oriented. AHSEM shows whether a particular longwall orientation and extraction sequence places the headgate corner in a stress concentration or in stress relief. It also estimates the magnitude of the stress concentration.

Apr 1, 2003

By J. J. Drost

This Bureau of Mines investigation studied the effect of thermal treatments upon concentratability of a western Mesabi Range nonmagnetic taconite ore and is a sequel to Bureau of Mines RI 7567. Magnetic tube tests were used to develop the data needed to calculate separation efficiency, the primary measure of concentratability. A horizontal tube furnace was employed to heat treat and reduce the hematitic ore samples. The two variables studied were roasting temperature and cooling method. The manner of cooling, either by slow cooling or quenching in water, produced no significant difference in concentratability. Roasting temperatures employed ranged from 500° to 1,000° C, and a temperature of 650° C effected the best concentratability. The temperature of 650° C correlated with the most effective roasting temperature for grindability.

Jan 1, 1973

By Jon C. Volkwein

Advances in mining technology have enabled deeper seams of coal to be mined from the surface. Highwall mining is frequently used to mine areas at the perimeters of a surface mine when removal of the overburden becomes uneconomical or threatens environmentally sensitive surface features. At the same time, advances in materials and technology have enabled highwall mining of coal that create blind headings over 300 meters in length. Deeper surface mining and deeper highwall penetration depths have lead to more frequent encounters with methane gas. While this coal is remotely mined from the surface, underground ignitions of methane have propagated to the surface and injured miners. Methods described in this paper show how this hazard can be correctly monitored and controlled for auger type highwall mining machines. Research indicates that small quantities of gas liberated during mining migrate to the face, creating higher gas concentrations than would otherwise be expected. Using the same principles that cause the gas to migrate to the face, researchers have shown that inert gas introduced at the collar of the hole can inert the entire hole, thus ensuring safe conditions for mining.

By Robert T. Beckman

The results of a preliminary investigation of compressive strength versus length-diameter (L/D) ratios of potash specimens and the statistical treatment of the data are summarized in this report. The purpose of the study was to evaluate a laboratory method for obtaining estimates of the strength of potash pillars during robbing operations. The specific objectives of this preliminary investigation were to test the method and the reliability (confidence limits) of the data, and to determine the number of additional specimens necessary for given confidence limits. The specimens were taken from three sites at two mines in New Mexico. The statistical analyses included the determination of the confidence limits for the data and the number of additional specimens necessary to obtain confidence limits of ±500 and 100 psi. The testing method was found acceptable, and estimates of the comprehensive strength, within 1500 psi, could be obtained by testing about 110 additional specimens from the three sites. The compressive strength of the specimens tested fits an empirical equation of the type

Dec 1, 1963

By James A. Morgan

FIELD MEASUREMENTS OF NOISE WERE MADE ON THE PERIPHERY OF ENCLOSURES DESIGNED, MANUFACTURED AND INSTALLED BY INDUSTRIAL ACOUSTICS COMPANY, INC. ON THE SECONDARY TACONITE CRUSHER AT THE JACKSON COUNTY IRON COMPANY PLANT IN BLACK RIVER FALLS, WISCONSIN. NOISE REDUCTION ACHIEVED BY THE ENCLOSURES WAS SUFPICIENT TO PERMIT REDUCTION OF CRUSHER ROOM NOISE TO 90 DBA, PROVIDED THAT OTHER SOURCES ARE APPROPRIATELY TREATED AND ACOUSTICAL ABSORPTION IS PROVIDED IN THE CRUSHER ROOM. SECONDARY CRUSHER NOISE WAS REDUCED 10 TO 15 DBA BY THE ENCLOSURES.

Jan 1, 1980

By T. A. Henrie, E. K. Kleespies

Electrolytic studies were conducted to determine the transfer rates of the alloying constituents from molten titanium anodes to solid titanium cathodes in molten salt systems . The metals , nickel , tin , copper , bismuth , and manganese , were selected on the basis of thermodynamic data and the melting point of the alloy system . The transfer of nickel , tin , and bismuth was very low . The content of these elements in the cathode was in the range of less than 0.01 to 0.001 percent . The copper transfer was 0.6 to 0.8 weight - percent in electrolytes containing titanium chlorides and 0.12 weight - percent in titanium fluoride salt systems . The manganese transferred at rates comparable to that of titanium . Highpurity titanium and titanium- manganese alloys of uniform composition were produced by electrorefining molten titanium alloys in chloride electrolytes . Comparisons are made between the calculated and the actual quantities of metal transfer .

Jan 1, 1964

By R. J. Fantel

To determine the availability of phosphate rock from domestic re- sources, the Bureau of Mines evaluated the potential production of phosphate rock from the demonstrated resources of 130 mines and deposits. The evaluation included an estimation of resources, engineering methods, and capital and operating costs, and an economic analysis to determine each operation's average total cost of production over the life of the mine, including a 15-pct discounted-cash-flow rate of return on all investments. Quantified but not evaluated in this report are substantial phosphate resources at the inferred and hypothetical resource levels. The 130 mines and deposits contain 6.4 billion tons of recoverable phosphate rock product, about 20 pct from producing mines. At total production costs of under $30 per ton in January 1981 dollars, about 1.3 billion tons of phosphate rock product is potentially available, over 90 pct from producing mines. This study suggests that production from low- cost, high-grade phosphate mines now in operation will decline during the next decade, and new higher cost, Lower grade mines will have to be developed to satisfy demand into the next century, In addition to the demonstrated resources evaluated in this study, 7 billion tons of inferred-level and 24 billion tans of hypothetical- level phosphate rock are potentially recoverable, which, in part, includes material containing high amounts of magnesium, Much of this material could likely become available in the near future.

Jan 1, 1983

By John M. Gomes

The Bureau of Mines investigated two techniques for removing CaO from scheelite (CaW04) prior to electrolysis. In the first technique, a crude tungstic oxide (WO3) containing 0.15-percent lime (CaO) was prepared by digesting scheelite concentrates in hot hydrochloric acid. This oxide was used as cell feed to produce tungsten of 99.9-percent purity. The second technique used a high-temperature, two-phase separation, resulting in extraction of 99 percent of the WO3 in the halide-tungstate phase, while 90 percent of the CaO was retained in the silicate phase. Tungsten of 99.9-percent purity was deposited from the halide-tungstate melt after B203 and NaPO3 were added to form an electrolyte. The two methods were compared with a previously developed technique of depositing tungsten from scheelite concentrate fed directly to the electrolytic cell.

Jan 1, 1971

By A. L. Johnson

In this Bureau of Mines report, time-resolved infrared emission spectra and corresponding pressure and temperature histories are reported for large-scale propagations of CH4-air, CH4-air-N2, and CH4-air-CF3Br ignitions in a 12-ft-diam sphere. Absolute spectral radiances were obtained throughout combustion over the 1.6- to 4.8-gym range, and the radiance growth patterns for the H20 (2.5-µm) bands are presented as a function of methane stoichiometry and diluent concentration. Flame temperatures were determined from the C02-band emissions, which approximated unit emissivity shortly after ignition. Burning velocities are also given for some of the test-mixture compositions. Measured flame temperatures were in excellent to fair agreement with theoretical adiabatic values for the CH.-air and CH4-air-N2 mixtures; the best agreement was for the stoichiometric CH4-air mixture. The CH4-air-CF3Br mixtures with =2 pct CF3Br gave poor agreement with theory. The measured temperatures were significantly lower during the early stage of combustion; furthermore, the later stage of combustion was uninhibited and yielded unexpectedly high pressures. Supplemental data from a 2-ft-diam sphere at various initial pressures confirmed that the CF3Br inhibition effectiveness decreases with increased pressure. The possible effects of buoyancy, turbulence, and changing kinetics are discussed.

Jan 1, 1977

By Thomas V. Falkie, R. Venkataramani

1. Summary This investigation is concerned with description of the loading function at the underground coal face, and the identification of varia¬bles - geological, geometric, mechanical, and operational - that affect the loading function. The immediate objective of this work was to provide information for operations-research studies as applied to underground coal mining, and the broad objective was to provide guide¬lines for planning and equipment selection in underground coal mining. The loading function was expressed as -a statistically-developed linear mathematical model. Originally, fifteen independent variables were considered which potentially could have influenced the loading function. These variables were constructed on the basis of measurable or estima¬ble geometric and geological properties at the working face, mechanical characteristics of the mining machine, and certain operational proce¬dures of mining. The original model explained 64.0 percent of the experimental variation. The final condensed model explained 54.1 percent of the experimental variation in terms of only five indepen¬dent variables, namely: 1. Ratio: width of cut/total width of cutter 2. Ratio: height of cut/diameter of cutter 3. Total horsepower of cutter-drive motors 4. Rotation speed (RPM) of cutter 5,. A subjective estimate of machine quality and operator skill Certain limitations were found to exist in the evaluation of the variables. Principle among these limitations was the impossibility of precise measurement of tonnage loaded in certain instances.

Jan 1, 1972

By B. J. Dalton

The Helium Research Center, Helium Activity, Bureau of Mines, is presently engaged in a critical examination of all of the PVT data on helium that appear in the literature. The long-range objective is the development of a single equation of state for helium that will allow all of the thermodynamic properties to be calculated and will reproduce all of the data within the accuracy with which the data are known. A preliminary objective is to obtain the best values of the second virial coefficients and to develop an equation that will reproduce the best values as a function of temperature. The method of treatment consists in expressing the PV product of a gas, for a given isotherm, in terms of a power series in either the pressure or the density and evaluating the constants by least squares solution. Associated with these functions whose coefficients have been evaluated by least squares, the following errors, or deviations, are of interest; the standard error of a single measurement; the standard error in each coefficient; and the standard error of the resulting function.

Jan 1, 1964

By B. J. Dalton

The Helium Research Center, Helium Activity, Bureau of Mines, is presently engaged in a critical examination of all of the PVT data on helium that appear in the literature. The long-range objective is the development of a single equation of state for helium that will allow all of the thermodynamic properties to be calculated and will reproduce all of the data within the accuracy with which the data arc known. A preliminary objective is to obtain the best val¬ues of the second virial coefficients and to develop an equation that will reproduce the best values as a function of temperature. The method of treatment consists in expressing the PV product of a gas, for a given isotherm, in terms of a power series in either the pressure or the density and evaluating the constants by least squares solution. Associated with these functions whose coefficients have been evaluated by least squares, the following errors, or deviations, are of interest; the standard error of a single measurement; the standard error in each coefficient; and the standard error of the resulting function.

Jan 1, 1964

By J. P. Walsted

The lack of an iron-smelting industry in the Pacific Northwest places the ferrous metals industries under an economic handicap. No iron-smelting enterprises, now dormant, had been operated successfully. Iron made at both of hoes installations proved to be satisfactory for normal pig-iron uses. Electric power and reductants acre available in the area. Power from the dames now completed and. those being constructed insures present and future needs for basic industries. Subbituminous coal, close to the main supply of iron ore, insures ample reluctant for all smelting requirements.

Jan 1, 1954

By Albert J. Rambosek

The objective was to obtain qualitative information on (1 ) the stress field in a core stub at the bottom, or face , of a cored borehole and (2 ) whether , and at what distance , in terms of core diameters from the face of the borehole , relief of stresses in the core is complete . The photoelastic and brittle lacquer techniques of stress analysis were used to determine the pattern of stresses in two- dimensional models , simulating the bottom of a borehole with a projecting stub of core . The core was stress- free at 1-1 /2 core diameters or more from the face of the simulated borehole . The analyses of the isoclinic and isochromatic patterns in the core near the face of the borehole reveal why core occasionally breaks into thin plates , when core or stress - relief drilling is attempted in highly stressed rock masses , such as heavily loaded mine pillars . stub broke away from the bottom in a hydrostatically loaded artificial rock specimen in a manner indicating that core " wafering" can result from tensile stresses developed in the core when a coring bit penetrates the highly stressed rock mass .

Jan 1, 1964

By A. J. Kraemer

[A great deal of interest has been manifested in the question of sulphur in fuels for automobile engines. Many different opinions have been expressed with respect to the effect of sulphur in gasoline on engine wear and engine performance. A wide difference of opinion exists as to the permissible limit of sulphur content for satisfactory operation.]

Jan 1, 1927

Coal is a combustible, carbonaceous, sedimentary rock that is formed by the accumulation, compaction, and physical and chemical alteration of vegetation [Simon and Hopkins 1981; Bates and Jackson 1987]. Coal is classified according to its type, grade, and rank. The type of coal relates to the plant materials from which the coal originated. The grade of coal refers to the purity of the coal-or the amount of inorganic material (including ash and sulfur) left after the coal is burned [Bates and Jackson 1987; Stefanko 1983]. The rank of coal indicates its degree of metamorphosis and roughly correlates to the geological age of the coal or the geological environment from which it has been mined [Bates and Jackson 1987]. Rank also indicates the percentage of carbon in dry, mineral-free coal [Whitten and Brooks 1973] and the degree to which the coalification process has progressed [Larsen 1981]. The geological process of coalification begins with organic materials (e.g., celluloses, lignins, and other plant compounds that are deoxygenated and then dehydrogenated) and ends with coal of various geological ages, from lignite to anthracite [Larsen 1981]. Table 3- 1 presents the American Society for Testing and Materials (ASTM) classification of coals by rank. According to Parkes [1982], high-rank coal includes anthracite and semianthracite coal ("hard coal," with 91% to 95% carbon); intermediate-rank coal includes low-, medium-, and high-volatile bituminous and sub-bituminous coal ("soft coal," with 76% to 90% carbon); and low-rank coal includes lignite (with 65% to 75% carbon or less). The rank of coal tends to increase from the western to the eastern United States, with anthracite occurring primarily in eastern Pennsylvania [Schlick and Fannick 1971]. Most of the coal currently mined in the United States is bituminous [Given 1984]. A classification of the coal in the United States is provided in Table 3-2.

Jan 1, 1997

By Gerald L. Finfinger

The Bureau of Mines conducted an experimental degasification project in Island Creek Coal Co.'s Virginia Pocahontas No. S mine. Methane from the overlying Pocahontas No. 4 coalbed was entering mine workings in the Pocahontas No. 3 coalbed through fractures in the roof rock. Small-diameter (l-S/B-inch) holes were drilled into the overlying coalbed to reduce the gas pressure and intercept methane flows, which were piped to the surface through an underground 6-inch-diam steel pipeline. The total methane flow rate from the vertical holes averaged 150,000 ft3/day for the first month. Methane flows into the mine were reduced by 47 pet, thereby demonstrating the effectiveness of this form of degasification in reducing ventilation requirements and providing a safer working environment.

Jan 1, 1979

By R. M. Santmyers

This paper represents one of a series of digests of foreign mining legislation that is being prepared in advance of a general report relative to the rights of American citizens to explore for minerals and to own and operate mines in various foreign countries . This interpretation of the mining legislation of Tunisia was prepared from a copy ( in French ) of the Mining Decree of Tunisia promulgated December 29 , 1913 , by the Resident General of France in Tunisia and effective January 1 , 1914. It is released subject to correction and amplification , if necessary , by the proper American diplomatic and consular officers , to whom it will be referred through the courtesy of the Department of State .

Mar 1, 1933

By B. K. Cantrell, K. L. Rubow

"Two source apportionment techniques have been applied by the Bureau of Mines to aerosol measurements in diesel equipped underground noncoal mines. The first technique is based on size selective sampling and the premise that the diesel exhaust fraction of the aerosol is predominately sub-micron in size while the mineral dust fraction of the aerosol is mostly super-micron in size. The second technique, Chemical Mass Balance (CMB) modeling, was used to referee the analysis of diesel and mineral dust aerosol concentrations with the size selective method.The size distribution data were modeled using a log-normal regression to parameterize the sub- and super-micron fractions of the sampled aerosol and to estimate the mineral and diesel contributions to each. For the mines visited, analysis of the size selective: samples yielded an average value for the fraction of the fine aerosol attributable.to mineral dust of 3 pct.'The CMB analysis, applied to both fractions of the respirable mine aerosol, yielded the amount contributed to each by the diesel· and dust aerosol sources. Less than 5 pct of the sub-microm fraction was mineral dust, however, as much as 20 pct of the diesel aerosol was found: ""in the super-micron fraction requiring a correction of the sub-micron fraction to account for the missing diesel mass. More accurate measurement will require a carbon specific analysis of the aerosol."

Jan 1, 1988

By John C. Machisak

INJURY DATA and experience at coal mines in the United States for 1957 are presented in this bulletin under the following general sections: (A) General injury experience: Tables 1-6: Current data on number of fatal and nonfatal injuries, frequency and severity rates, and average severity. (B) Selected injury experience: Tables 7-36: Current data on causes of injuries, distribution of injuries by part of body injured, days of disability, extent of hand and machine loading, experience by employ¬ment and production groups, and various other operating factors and physical conditions related to the occurrence of injuries at the Nation's coal mines. (C) Injury experience, by States: Tables 37-41: Data on injuries, injury rates, employment, causes of injuries, and severity rates. (D) Major disasters: Table 42: Data on major disasters from 1948 to 1957. A major disaster is defined as a single accident in which, or as a result of which, five persons or more are killed instantly or die at any time thereafter. (E) Historical coal-mine-fatality experience: Tables 43-47: Data on fatalities and their causes at bituminous-coal, lignite, and anthracite mines from the earliest records through 1957.

Jan 1, 1960