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By Noel N. Moebs

Studies by the Bureau of Mines have identified geologic structures in mine roof rock that contribute to many roof falls in Appalachian coal mines. These structures, including paleochannels, scours, pinchouts, slickensides, clay veins, crevasse splays, and joints, can often be identified during, and sometimes before, mine development. Mine projections can be revised to reduce the adverse effects of discontinuitites in roof structure; large roof areas of laminated sandstone or incompetent strata generally can be delineated or inferred from exploratory drill hole data, and the need for supplementary support can be anticipated. Accurate descriptions of roof geology also provide some indication of optimum length and type of roof bolts that should be installed.

Jan 1, 1981

By John C. Hartley

Three systems that monitor ventilating fans are described. These electronic monitoring systems automatically perform most of the operations required to conform with the provisions of the Federal Mine Safety Code in the event of fan failure or slowdown.

Jan 1, 1964

By M. Kanda, W. D. Bensema, J. W. Adams

Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating hardrock mine, Grace Mine, located near Morgantown, Pennsylvania. Diesel-powered haulage equipment is used in this mine, and the electromagnetic noise environment it creates was measured to see how it differs from the environment created by electric-powered haulage equipment. One technique measures noise over the entire electromagnetic spectrum of interest for brief time periods. Data are recorded using broadband analog magnetic tape and are later transformed to give spectral plots. The other technique records noise amplitudes at several discrete frequencies for a sufficient amount of time to provide amplitude probability distributions. The specific measured results are given in a number of spectral plots and in amplitude probability distribution plots.

Jan 6, 1974

By R. E. Thill

The ultrasonic pulse measurement system described measures velocities of longitudinal (compressional) and shear waves in rock to give values that can be used with density values to determine the dynamic elastic constants of rock. A special feature of this pulse measurement system is its unique acoustical bench that minimizes errors in pulse transit times that are commonly associated with coupling, sample alinement, and sample orientation. Some special features of the acoustical bench are its highly versatile transducer cartridges, a pneumatic ram coupling device, an orientation mechanism, and a vacuum chuck sample holder. The lathe-bed-like construction of the acoustical bench assures automatic alinement of samples and versatility in accommodating samples of various shapes and sizes.

Jan 1, 1968

By John W. Adams, W. D. Bensema, Motohisa Kanda

Two different techniques were used to make measurements of the absolute value of electromagnetic noise in an operating coal mine, Robena No. 4, located near Waynesburg, Pennsylvania. One technique measures noise over the entire electromagnetic spectrum of interest for brief tine periods. With present instrumentation, the spectrum can be covered from 40 Hz to 400 kHz. It is recorded using broad-band analog magnetic tape, and the noise data are later transformed to give spectral plots. The other technique records noise envelopes at several discrete frequencies for a sufficient amount of tine to provide amplitude probability distributions. The specific measured results are given in a number of spectral plots and amplitude probability distribution plots. The general results are that at frequencies below 10 kHz, power line noise within the mine is severe. Impulsive noise is severe near arcing trolleys, and at lower frequencies near any transmission line. Carrier trolley phone signals and harmonics are strong throughout the mine whenever the trolley phone is in operation. Additional information beyond that included in this report may be obtained from the authors, who are with the Electromagnetics Division of the National Bureau of Standards.

Jan 4, 1974

By Fred A. Williams

The cause of many deaths and extensive property damage in coal mines resulting from explosions and mine fires has been directly attributable to electric cable failures (including splice failures). The Federal Bureau of Mines data show that out of 355 underground coal mine fires investigated from July 1952 to January 1960, 103 (29 percent) were directly related to trailing cables. These cable failures resulted in the death of 7 men and injuries to 37 others. These potential hazards have become greater, obviously, through the widespread adoption of mechanized mining methods with electric-driven machinery powered through trailing cables according to Young,4 68.1 percent of the total bituminous and lignite production of the United States was mined underground in 1959. About 85 percent of this production was attained by mechanized loading methods. A large majority of the mines using the hand- loading methods also used equipment with trailing cables such as cutting machines, drills, and gathering locomotives. The problem of minimizing the loss of life, resources, and equipment from cable failures should be of concern to the management of all coal mines. It would be misleading to imply that no consideration has been given to the problem and its associated hazards. Through research cable manufacturers have endeavored to develop trailing cables that will withstand the severe service imposed by underground mining conditions. Technical research groups have undertaken studies for determining improved procedure and materials for field splices. Coal companies have instituted cable maintenance programs with a view toward the reduction of cable failures and consequent improvement in safety and efficiency of operations. Safety agencies are alert to unsatisfactory cable handling practices, poor workmanship in field splicing, mechanical

Jan 1, 1962

By William H. Pomroy, Annie M. Carigiet

This U.S. Bureau of Mines publication is an analysis of underground coal mine fire incidents occurring in the United States during the 15years from 1978 through 1992. The fire data used in this analysis were obtained from U.S. Mine Safety and Health Administration mine fire investigation reports. Fires were analyzed by year, State, coalbed thickness, mine size, mining method, ignition source, burning substance, location, equipment involved, detection method, time of day, time of year, number of injuries and fatalities, method of extinguishment, and evacuation measures taken. In all, 164 fires are included in this report, or an average of 10.8 fires per year. The most fires occurred in West Virginia, Kentucky, and Pennsylvania, respectively. However, the fire incidence rates for these States, expressed as the number of fires per million tons of coal mined, were the lowest, second lowest, and fourth lowest of all underground coal producing States. The most common ignition source was electricity; the most common burning substance was coal; the most frequent fire location was the belt entry; the most common equipment involved in fires was the conveyor belt; and the most common extinguishing agent was water.

Jan 1, 1995

Prevention of coal-mine explosions depends largely upon thorough knowledge of the causes that initiate explosions. A review of coal-mine explosions in one geographical area when supplemented by nationwide data of similar nature, should serve as a guide for the adoption of measures for explosion prevention. Explosions in bituminous-coal mines of the United States during the 10 years ended December 31, 1932, ranked third in the causes of fatal accidents and constituted 16.1 percent of all fatal accidents in bituminous mines. Kentucky now ranks fourth in coal output in the coal-producing States of this country; a study of the coal-mine explosions in this state will be of definite interest locally among coal-mining people, as well as to those in the coal-mining industry who are concerned in preventing coal-mine explosions. This circular reviews gas and dust explosions in Kentucky coal mines to show their hazards, to point out the influence of certain factors in causing explosions, and to indicate the effectiveness of preventive measures.

Jan 1, 1934

By R. S. Sanford

The Muir Inlet or Nunatak molybdenum deposits arc in the Glacier Bay district, Muir Inlet, miles northwest of Juneau. The deposits were examined by Bureau of Mines engineers, and the area was mapped by a field party of the Federal Geological Survey during the summer of 1942. 5/ The following year the Bureau of Mines began developing the deposits. A total of 217 channel samples were taken, and 2 diamond drill holes totaling 256 feet wore drilled. The samples were sent to the' Bureau's laboratories at Rolla, Mo. for beneficiation.

Jan 1, 1949

By K. P. V. Lei

An electrochemical process was developed for the preparation of vanadium from vanadium carbide. Commercially available vanadium carbide (V2C) was used as the starting material. Vanadium was obtained by electrolysis of the V2C in a BaCl2-KCl-NaCI-VCl2 electrolyte at 670° C using a helium-atmosphere, molten-salt electrolytic cell. Vanadium products were recovered with purities high as 99.6 percent. Current efficiencies of 87 percent and vanadium recoveries of 84 percent were attained. The cathode products were amenable to electrorefining to high-purity vanadium of 99.96-percent purity.

Jan 1, 1971

By J. W. Adams

Measurements of surface magnetic field noise were made at various locations over the Geneva Coal Mine near Price, Utah, on June 12, 1973. The locations selected were on the surface over emergency locator beacons underground at depths between 3S0 meters (1150 ft.) and 488 meters (1600 ft.). The surface terrain where these measurements were made was mountainous, and access was difficult. There were no power lines within several miles, and the weather was clear; therefore, the magnetic noise levels were about as low as will normally occur. Results of measurements of distant sferics indicate rather sharp cutoff frequencies below which broadband, impulsive noise is attenuated. The mechanism of propagation for this noise above the daytime cutoff frequency of 3500 Hz and the nighttime cutoff frequency of 1700 Hz is deduced to be a waveguide formed by the D or F layers of ionosphere as an upper plane and the earth as a lower plane.

Jan 1, 1974

By L. A. Neumeier

The Bureau of Mines evaluated creep and other properties of extruded Zn-30 pct-AI alloys containing 0 to 0.7 pct Mg. The alloys were extruded both above and below the Zn-Al eutectoid temperature of 275° C. Creep behavior is defined for the alloys as extruded and after various heat treatments. Tensile properties, hardness, thermal expansivity, impact resistance, and microstructures are given. The alloys, either with or without magnesium, required substantially less pressure for extrusion near 275° C than at higher or lower temperatures. The alloys containing magnesium exhibited significantly greater hardness, tensile strength, and creep resistance, but much lower ductility than the 2n-30 pct Al alloy. The properties were very sensitive to the processing conditions.

Jan 1, 1971

By Charles L. Kimbell

For a study such as this, which summarizes and amalgamates much information collected, compiled, and utilized by the numerous U.S. Bureau of Mines country specialists and branch chiefs for inclusion in the country and regional reports that comprise the five other sections of 1991 Minerals Yearbook-International Review, it is clearly impossible to cite all sources of information used in its presentation, but some recognition is due. Generally speaking, this study and its related detailed studies on countries and areas would be much more difficult, if not impossible, without the efforts of the personnel of national mining and geological agencies throughout the world. Information that they collect, compile, and then publish, either in their own volumes or those of central statistical agencies in their countries, are the foundations on which this work rests. Thus, appreciation is expressed to the multitude of persons employed by these agencies.

Jan 1, 1993

By J. Burlin Johnson

In small-scale blasting experiments conducted in the Bureau of Mines laboratory, small charges were used to produce craters in blocks of concrete mortar. The results are compared with larger scale experiments of other research workers, and the comparison demonstrates the similarity of the results obtained and indicates that small-scale blasting should be a useful tool for predicting large-scale blasting effects. INTRODUCTION The purpose at this investigation was to conduct blasting experiments in mortar in the laboratory and then, by comparing the results with those from larger scale field blasts in rock to determine to what extent, if any, the laboratory results resemble those in the field. The work described herein was the initial phase of a project aimed at evaluating small-scale blasting as a tool for use in improving blasting techniques. It is evident from the stand-point of control and cost that small-scale blasting would be valuable in the study of rock fragmentation by blasting in mines and quarries, if the extrapolation is valid.

Jan 1, 1962

By Barry W. Klein

The performance of the U.S. economy in 1977 was similar to that in 1976 which, in turn, had been a considerable improvement over 1974-75. In 1977 real gross national product (GNP) showed a similar, but some-what slower, growth pattern compared with 1976. Real GNP increased sharply in the first quarter of the year followed by smaller increases for the remaining three quarters. With only two exceptions, the monthly unemployment rate declined or remained steady throughout 1977, falling to a low for the year in December. The inflation rate in 1977 was slightly higher than in 1976, but the rate still remained far below that of 1974-75. Total U.S. output as measured by GNP in current dollars rose 10.8% in 1977. Real GNP in constant 1972 dollars increased 4.9%, and inflation, as measured by the implicit price deflator, rose 5.6%. In real terms, gross private domestic investment for residential structures increased 19.3% in 1977, only slightly below the 22.9% rise in 1976; State and local government expenditures increased 1.1 % in 1977; and personal consumption expenditures for services rose 4.5%.

Jan 1, 1980

By D. R. Flinn

The Bureau of Mines has studied the electrochemical parameters important to the preparation of coatings of the platinum-group metals. Using molten mixtures of sodium and potassium cyanides in an inert atmosphere, techniques have been developed that permit the preparation of baths for platinum, rhodium, and iridium electrodeposition. Cyclic voltammetric and slow sweep rate linear polarization techniques have been utilized to determine optimum potential and current values for preparation of plating baths and for the electrodeposition of coatings. Techniques are described for the deposition of platinum and rhodium coatings at near 100 percent anode and cathode current efficiencies, and for iridium at approximately 80-percent efficiency. Palladium deposition from these molten cyanide baths remains un-satisfactory. The chemistry of the palladium-containing cyanide bath is discussed. Examples of scanning electron microscope photomicrographs of typical platinum coatings are presented. Techniques are described for the preparation of platinum coatings on large objects.

Jan 1, 1982

Water infiltration control techniques are designed to reduce the total volume of water entering an underground mine, and thus, reduce the volume of mine water discharge During the development of underground mines, water may be encountered in various quantities This water must be pumped from the mine during active mining, and in many situations, the weight of water removed will be more than the total weight of mineral extracted After abandonment of the mine, infiltrating water either floods the mine workings or discharges from the mine (27, 127) Infiltrating water may enter underground mines from above, below, or laterally through adjacent rock strata Earth fractures such as faults, joints, and roof fractures resulting from surface subsidence are commonly primary causes of water entrance Into abandoned underground mines Factors affecting the quantity of water entering a mine will be the depth of the mine, location of water bearing strata, and ground water flow patterns Investigations of the quantity of water entering underground coal mines have found the average rate of infiltration to range from approximately 6,262 to 10,280 liters per hectare per day (670 to 1,100 gal/acre/day) (27) Water flowing through underground mines flushes pollutants from the mine and may result in their discharge to the environment A reduction in the amount of flow usually results in a reduction in total pollution load discharging from the mine The techniques discussed in this section can be used to reduce the volume of surface and groundwater available to enter the mine system and transport pollutants The selection of a control technique will depend upon the characteristics of the mine system and the expected cost effectiveness of the technique In order for water infiltration control to be effective in controlling mine drainage pollution, the reduction in mine water flow must not be accompanied by an increase in concentration of pollutants (127) REFERENCES 2, 27, 51, 58, 127, 132

Jan 1, 1975

By B. R. Mohal, F. F. Aplan, S. Chander

"The wetting behavior of coal has been determined in the presence of nonyl and octyl series of nonionic surfactants containing polyethoxy groups of different sizes. The wetting behavior was determined by a modified Walker technique and contact angle measurements. The results show that the wetting rate of coal varies with coal rank, structure of the hydrocarbon chain and number of ethoxy groups in the hydrophilic group of the surfactant. A close relationship has been observed between the wetting rates and the short-time advancing contact angles.INTRODUCTIONNonionic surfactants are used in many applications to improve wettability of solids. They can be used as dispersing agents [ 1 ] or dust suppressants [ 2-5] and to control the flotation, flocculation, filtration and flowability of particulates. This study was undertaken to study the effect of a series of nonionic surfactants on the wetting behavior of coal. Two series of surfactants, namely, ethoxylated nonyl and octyl phenols were used. The nonyl phenol series contains a linear hydrocarbon chain containing nine carbon atoms ( CH3 ( CH2 ) 8-C6H4-( OC2H4 )""' where n is the number of ethoxy groups). The octyl phenol series contains a branched hydrocarbon chain containing eight carbon atoms ( ( CH3 ) 3CCH2C ( CH3 ) 2-C6H4-( OC2H4)"").Initial wetting rates - modified Walker techniqueWalker et al. [ 6] developed a sink test to determine the wettability of coal particles. In this technique, coal particles are dropped individually onto the surface of surfactant solutions of different concentrations, and the most dilute concentration in which coal would sink ""instantaneously"" is determined. This technique is a variation of a procedure initially developed by Draves and Clarkson [ 7] to determine the effect of surfactants on wettability of cotton fibers."

Jan 1, 1989

By J. R. Hoskins

A recent survey of 23 vein-type metal mining operations in several western states discloses that some of the more serious deficiencies in ventilation technology are associated with inordinately high levels of mine resistance. This problem has progressively increased over many years of operation (without adequate remedial action) as mines have become extended in depth. Where two shafts form the downcast and upcast airways of a relatively deep mine, the whole of the mine air volume must pass through each shaft in turn. Since at least one of these shafts contains hoisting equipment, structural members are necessary to support the rigid guides and shaft walls. These offer high aerodynamic resistance. In some deep mines, a single shaft of this nature may represent upwards of one-half of the total mine resistance. The second shaft, depending upon its design, may represent an additional one-third of the mine resistance. Therefore, the various working levels throughout the mine contribute only the small remaining amount of the total mine resistance.

Jan 1, 1972

By R. L. Brown

This report, the seventeenth in an annual series, summarizes Bureau of Mines research and technologic work on coal and related investigations for July 1, 1951, to July 1, 1952. It 1s based largely on publications issued during the fiscal year, although 10 some instances data are presented that have not been published previously. Footnote references are given to the publications so that further details on the work may be obtained. Bureau of Mines research on the mining, preparation, and utilization of coal is directed toward developing and encouraging safer and more efficient mining practices and preparing and utilizing coals to the best advantage.

Jan 1, 1953