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By Jay D. Dixon

The Bureau of Mines has developed structural design data for unreinforced concrete tunnel linings for drifts used in block caving stopes. Design data are given that consist of moment, thrust, and deformation coefficients from which bending, axial, boundary stresses, and structural deformations can be determined at any point on the lining. Data is given for circular, horseshoe, and rectangular linings, each with two different thicknesses and subjected to eight different loading conditions for drifts excavated in hard and soft rocks. The structural analyses performed are based on procedures that account for both the structural behavior of the lining and that of the drift and take into consideration deformational interaction that occurs between them.

Jan 1, 1973

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

A portable, multichannel battery-operated mine-permissible measurement system was developed to measure the rms magnetic-field noise spectrum in the frequency range from 100 Hz to 375 kHz. During each measurement, the entire spectrum is measured simultaneously through the use of time-domain recordings which are later analyzed by Fast Fourier Transform processing. Dynamic ranges of 60 dB in a 125 Hz bandwidth are obtained for spectra covering the range from 100 Hz to 100 kHz. The method also allows a three-dimensional display of the way spectrum occupancy changes with time. Calibration and correction procedures allow absolute field strength measurement with an uncertainty of not more than 3 dB. We feel that further analysis of the system errors will allow this uncertainty to be reduced to less than 1 dB. Ambient magnetic field noise spectra covering frequencies from 100 Hz to 100 kHz are given for several underground coal mine locations. Examples are also given of magnetic field noise on the surface above the mine, noise in the mine face area, noise radiated by specific equipment, the voltage spectrum found on a 600 V dc trolley wire, and noise picked up simultaneously on loops and on roof support bolts.

Jan 1, 1973

By Byron A. Baker

The Bureau of Mines used a windowed cell to measure the phase-boundary pressures of two related series of gas-condensate fluid mixtures. Normal butane was added to the mixtures incrementally to determine its effectiveness for lowering phase-boundary pressure. All the experimental data were correlated, so that the pressure required to maintain light oils mixed with natural gas in the single phase may be computed for secondary recovery applications. The heavy hydrocarbon parts of the mixtures were distillation fractions of a Gulf Coast condensate. Intermediate normal hydrocarbons in the butane-heptane range and natural gas were added to the fractions in selected proportions, so that phase-diagram pressures of 26 fluids were actually studied. The experimental range of temperatures was 50° to 280° F. Two correlations were developed to represent phase-boundary pressures by means of a polynomial. Independent variables represent natural gas content, disparity of properties of components comprising the mixtures, and temperature. A fourth variable, for one correlation only, was the quantity of normal butane added to the original mixtures. The latter correlation with four independent variables contains 15 coefficients and is estimated to be accurate to 135 psi.

Jan 1, 1973

By Peter F. Strong, Robert L. Lagace, Alfred G. Emslie

This paper is concerned with the theoretical study of UHF radio communication in coal mines, with particular reference to the rate of loss of signal strength along a tunnel, and from one tunnel to another around a comer. Of prime interest are the nature of the propagation mechanism and the prediction of the radio frequency that propagates with the smallest loss. Our theoretical results are compared with measurements made by Collins Radio Co. This work was conducted as part of the Pittsburgh Mining and Safety Research Center's investigation of new ways to reach and extend two-way communications to the key individuals that are highly mobile within the sections and haulage ways of coal mines.

Jan 1, 1973

By M. Kanda, J. W. Adams

A system for measuring amplitude probability distributions (APD’s) of electromagnetic noise in coal mines is described and typical APD’s from an underground coal mine are presented. The APD is a basic statistic required for the design and analysis of communication systems, especially those intended for use in noisy environments, and where neither overdesign nor underdesign is acceptable. The rms and average field strengths are obtained by integration of the APD, and examples are shown at several frequencies. All field strength levels are given in absolute units. Selected frequencies cover the range from 10 kHz to 32 MHz.

Jan 1, 1973

By T. Kessler

As part of a respirable mine-dust research program at the U.S. Bureau of Mines, spark-source mass spectrometry has been used for the semiquantitative determination of trace elements (200 ppm weight or less) in raw coals. In addition, several minor and major elements have been determined using this technique. Sixty-four elements ranging in concentration from 0.01 to 41,000 ppm weight were determined in one anthracite, two mvb, four lvb, and six hvab raw coal samples. The samples represented 10 coal seams located in Pennsylvania, West Virginia, Virginia, Utah, and Colorado.

Jan 1, 1973

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 William J. Campbell

This analytical method development and evaluation was undertaken by the Bureau of Mines to provide accurate determinations of eight minor elements in low-alloy steels prepared from ferrous scrap. Fluorescent X-ray spectrography was the principal method investigated. Confirming analyses were made by conventional instrumental and chemical methods. All X-ray data were processed by a timesharing computer. No corrections were found necessary for inter-element effects or overlapping spectral lines. Concentrations were calculated from the least-square fit of a linear calibration equation derived from measurements on three sets of standard steels. These studies show that X-ray spectrographic analysis of lathe-finished surfaces provides accurate determinations of aluminum, copper, chromium, manganese, nickel, phosphorus, silicon, and tin.

Jan 1, 1973

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

APPENDIX E EQUIPMENT USED FOR FIELD TESTING OF MINE SEALING SYSTEM I. Drilling Operation - Equipment supplied by local drilling contractor 1. Mobile drill rig. 2. Flat bed truck, containing 20 lengths of drill pipe. 3. Auxiliary compressor. 4. Pickup truck for small parts and supply of diesel fuel. 5. Bulldozer. 6. Water supply, in this case the nearby stream. 7. Supply of casing, positioned next to the drill rig. 8. Ready mixed cement grout. 9. Drill bits, stabilizer units, cutting and welding equipment, other miscellaneous tools and supplies. II. Sonar Probing Operation 1. 25 foot tower with pulley mounted atop. - FMA 2. Electric winch with 100 feet of 1/4-inch cable, Model No. 100A, City Engineering Co. , Indianapolis, Indiana. 3. 400 feet of 1-1/2-inch-diameter aluminum pipe with alignment holes and coupling grooves. - FMA*

Jan 1, 1973

By Stephen Krickovic

Air quantity-pressure and methane concentration surveys were conducted by the Bureau of Mines in accessible portions of an area being pillared in a Pittsburgh coalbed mine in West Virginia. These included two mined-out and three active butt headings and a bleeder system. The particular mine workings were started in virgin coal directly from a set of main headings; the main reason for the study was the difficulty usually encountered in adequately bleeding the gobs under such conditions. Although the two separate return airways in each active butt heading and the North and 1 Left bleeders contained acceptable methane concentrations (0.01 to 0.78 percent in the butts and 0.73 to 1.0 percent in the bleeders) with significant total methane removal (109 cfm in butts and 631 cfm in bleeders), there were relatively large areas in the gobs with possible minimal airflows. This condition appears to have developed from lack of systematic regulation of the airflow across the gobs and appears to indicate the existence of considerably more methane in the probably low flow areas in the gob.

Jan 1, 1973

By H. H. Fields

The Bureau of Mines is in the process of degasifying a virgin area in northern West Virginia from the base of an 839-foot-deep vertical borehole¬. An in situ gas pressure hole 199 feet long, and seven degasification holes ranging in depth from 500 to 850 feet (average 618 feet) were drilled in an 8-foot-thick virgin Pittsburgh coalbed from the enlarged (14-foot-diameter) bottom of this borehole. The in situ pressure at the back end of the hole and the range of gas and water flows from degasification holes as they were completed and closed off were 203 psi, 79,000 to 257,000 cfd (average 160,000 cfd), and 5 to 8 gpm per hole (average 6.8 gpm), respectively. Twenty-four hours after the seven holes were connected through individual water traps to a common collector for natural venting of the gas through pipes to the atmos¬phere, the total gas and water flows and the in situ pressure dropped, respec¬tively, to 971,000 cfd, 1.3 gpm, and 18 psi. Eighty days later the correspond¬ing values dropped to 529,000 cfd, 0.50 gpm, and 13 psi. After 180 days of degasification, 91 million cubic feet of gas had been removed from the affected virgin area. This represents 60 to 70 percent of the gas calculated to be contained in the area of coal affected by the holes.

Jan 1, 1973

By Robert B. Worthington

This investigation was undertaken to develop a more efficient copper smelting practice that would help meet the increasingly stringent antipollution standards. Continuous smelting to copper and a 0.8-to 5-percent copper slag using pure oxygen has been demonstrated for several hours at a time in a unique double furnace, which was devised to overcome the heat losses inherent in a laboratory furnace. The use of pure oxygen to effect the smelting and conversion of copper sulfide concentrate in a single unit to produce blister copper and a very high S02 concentration provides a much reduced gas volume for more economical and thorough sulfur recovery. Although the process was successfully demonstrated for several hours at a time, extended test work using longer runs will be required to balance the system and to obtain test data for adequately demonstrating its technical feasibility.

Jan 1, 1973

By Vance G. Leak

A technique for recovering copper and steel from metallic scrap has been developed by the Bureau of Mines based on preferential melting in molten salt baths at 1,150° to 1,250° C, The molten salt, preferably barium chloride or calcium chloride, both minimizes oxidation of the metals and promotes heat transfer. Cleanest separations (0.01 percent copper remaining in iron) have been achieved by pretreatment (dipping or spraying) with sodium sulphate or sodium silicate, which alters and coats the surface of the iron to inhibit the alloying or brazing with copper. An economic evaluation of the process was carried out on six combinations of sweating media and inhibiting reagents. On the basis of the postulated model, a cost of about $0.20 per pound of copper recovered has been determined for the sweating treatment operation.

Jan 1, 1973

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 H. B. Carroll

The Bureau of Mines investigated the adaptability of the Meteorology Research Inc.2 (MRI) nephelometer and the Sinclair-Phoenix smoke meter for use in routine, analytical, smog-chamber experiments and to compare their responses to aerosol during these experiments. Both instruments' sampling systems were modified--smaller size sample input systems were studied using the nephelometer and a secondary sample system was added to the smoke meter to allow measurement of Aitken or condensate nuclei. Both instruments were easily adapted for use with small smog chambers and both displayed good precision and sensitivity to aerosol. A correlation was shown to exist between the two instruments' responses to aerosol. This correlation makes it possible to report the Sinclair-Phoenix measurements in visibility and/or mass units if desired.

Jan 1, 1973

By A. J. Farstad, R. G. Olsen

The Coal Mine Health and Safety Act of 1969, passed by Congress in the wake of the disaster at Farmington, West Virginia, led to an extensive study by the National Academy of Engineering of the problems involved in coal mine safety. One of the results of this report and subsequent research conducted by the U. S. Bureau of Mines has been the investigation of electromagnetic techniques for the location of trapped miners after a mine emergency. The Westinghouse Georesearch Laboratory has been involved in both the 2 theoretical and field studies relating to this problem. A compact personal beacon transmitter has been developed which can be attached to and powered by a miner's lamp battery. A compatible lightweight loop antenna package has also been developed which can be easily carried on a miner's belt. This antenna can be quickly deployed on the mine tunnel floor. For the purpose of calculating its electromagnetic fields on the earth's surface, the loop can be considered to be a magnetic dipole buried in the earth. (The earth is assumed to be homogeneous and to have a conductivity of s mhos/m.) The surface of the earth is assumed to be uniformily sloping and the transmitter dipole oriented as in Figure 1. The fields on the earth's surface can be computed by using a superposition of the fields of a 4 vertical magnetic dipole3 and of a horizontal magnetic dipole in proportions which depend on the slope of the terrain. In the case of level terrain a null in the horizontal magnetic 5 field occurs on the surface directly above the dipole. This null is designated as the apparent source location and is the criterion by which the source is located. The criterion was tested at two hardrock mines and two coal mines in the fall of 1972. The apparent source locations were compared to actual locations determined by conventional surveying techniques. It was found that due to nonlevel terrain the apparent and actual source locations differed by up to 13 meters. This discrepancy can be resolved by an examination of the fields of a source beneath uniformly sloping terrain. Figure 2 shows the experimental and theoretical results for a

Jan 1, 1973

By Madan M. Singh

Hydraulic mining has been practiced in the United States since 1852 and many mineral commodities, such as gilsonite, phosphates, lead-zinc, silver ores and St. Peter Sandstone can be mined in this manner. In 1958, the U. S. Bureau of Mines initiated research into the mining of coal using these techniques.1-4 These early investigations were conducted in the 5000 psi pressure range. The large nozzle diameters used in this pressure range produced extremely high flow rates which created visibility problems at the coal face, and required removal of large amounts of water from the mining area. Besides, the production rates were not much better than with mechanical methods. This indicated that with higher pressures the water quantities might be reduced using the same or higher horsepowers but enhanced breakage. For this reason intensive investigation in material removal using fine water jets at extremely high pressures (50,000 psi to 100,000 psi) has been undertaken. This was not the entire reason for this contract from the Bureau of Mines, however. The contract objective is outlined later. IIT Research Institute has done pioneering work in high pressure jet development in the United States.5-8 Similar schemes have been investigated abroad. 9-13 Hydraulic mining of coal at relatively low pressures is successfully being done in the Soviet Union, Japan, Canada, and most recently, in Germany.

Jan 1, 1973

By Brian M. Harney

The technique of remote sensing, used for many years by earth scientists, is being applied to the detection and monitoring of air pollution. Instrumentation being developed is of a very diverse nature and is effective, Fn varying degrees, at ranges from 1,000 meters to the altitude of a space satellite. This paper describes a number of the recent developments in this new field. Instruments based on spectroscopic, laser, and photographic systems are discussed. Sensors are being developed which utilize correlation spectrometry, interferometry, Raman scattering, Mie scattering, laser line absorption, and simple photographic detection.

Jan 1, 1973

By Paul J. Barrett

The Bureau of Mines evaluated a sulfurous acid-sulfuric acid process for recovering alumina from clay, in which clay is leached. successively with sulfurous acid and sulfuric acid. The resulting aluminum sulfite and aluminum sulfate solutions are combined and heated to produce a basic aluminum sulfate and sulfur dioxide. Alumina is extracted from the basic aluminum sulfate as sodium aluminate by leaching with dilute sodium hydroxide. After desilication, sulfuric acid is used to precipitate alumina as alumina trihydrate, which is then calcined to alpha-alumina. The estimated fixed capital cost for a plant producing 1,000 tons per day of alumina is about $74 million on a 1971 basis. For comparison with previous alumina-from-clay evaluations, the estimated fixed capital cost for the plant is about $67 million on an M and S Chemical Equipment Index basis of 24.0.0, which is equivalent to a 1960 cost level. Because the operating cost is highly dependent on fuel and electric power costs, graphs are included to show the effect of these items on the operating cost. On a 1971 basis, with natural gas costing 35 cents per million Btu and operating labor costing $4 per hour, the estimated operating cost is about $100 per ton of alumina. On a 1960 basis, with labor costing $2.30 per hour and natural gas costing 25 cents per million Btu, the estimated operating cost is about $86 per ton of alumina.

Jan 1, 1973

By David A. Monaghan, Kenneth R. Maser, Adi R. Gurdar, D. Randolph Berry

8. Field Demonstration of the Remote Mine Sealing System in a Coal Mine 8. 1 Selection of Field Test Site Eastern Associated Coal Corporation (EACC) offered its Federal No. 1 coal mine in Grant Town, West Virginia as the site for field testing of the remote sealing system. The choice of Federal No. 1 mine was particularly appropriate as the first attempt at fire control by remote sealing was done in this mine in 1963. EACC provided the men and equipment required for much of the initial preparation. Considerable assistance, advice, and background on coal mining technology was given by Mr. William Laird, Vice President for Research and Development, EACC, and by Mr. Lawrence Jackson, Resident Engineer at the Federal No. 1 mine. District 3 USBM office, the West Virginia Bureau of Mines, the Technical Support Group of the USBM, and Local 4047 of the United Mine Workers of America also cooperated. 8.2 Preparation of Field Test Site 8.2. 1 Underground Site Preparation The underground site chosen for the field testing was in a non-working portion of the mine within a few hundred feet of the main haulage road, as shown in Figure 80. Known as "Seven Switch, " this area was a 20 minute walk or 5 minute "jeep" trip from the man-trip shaft. Ten years having passed since this area was actively worked, considerable effort was required for gob clearing, roof bolting, rock dusting, and rejuvenating the track from the haulage road to the test area. Three primary borehole locations were chosen for the test program. Borehole No. 1 was in a straight passageway

Jan 1, 1973