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By Joseph C. Zelanko, Anthony T. Iannacchione

One of the most difficult and longstanding engineering problems associated with coal mining is the catastrophic failure phenomenon known as coal mine bursts (known in the United States as bumps). For more than 70 years, researchers and practitioners have attempted to determine whether this destruction observed underground is caused by stress conditions within the coal pillar or from distant seismic sources in the mine roof and floor strata. The role of confinement and the extent of failure in solid pillars and panels have also proven difficult to define. These are important issues, since control solutions need to be based on a fundamental understanding of the problem. Obsenations by U.S. Bureau of Mines researchers over the last decade have helped to clarify certain aspects of these issues. Microseismic sensors and geomechanic field measurements have located areas of excess energy release, identified stress conditions in coalbeds close to failure, and recorded the response of mine structures prone to bursts. In the present study, data available for a range of U.S. bursts were considered in an effort to evaluate both common and distinctive features. Although the attempt revealed little commonality, encouraging results were produced by categorizing coal bursts by source mechanisms. When a coal burst is thus categorized, differences in environmental factors-such as geology, stress fields, and mining methods-are highlighted, and viable control strategies are readily recognized.

Prevent the propagation of a fire and control the spread of smoke and toxic gas in underground mines. Approach A fire door suitable for large openings in underground noncoal mines and providing protection for openings requiring 11/2 hours of fire resistance, a 250°F maximum temperature rise, and high pressure differentials was de-signed, laboratory tested, and in-mine tested. How It Works The door is a double-acting swing type. Its two panels. connected by an overhead linkage, open in opposite directions. Consequently, high pressure differentials across the door have little effect on the force required to open and close the door. The door is constructed of 14-gauge sheet steel skins welded to both sides of a 5-inch-wide steel channel frame. The frame is rein-forced with 5-inch-wide steel channels in a horizontal and diagonal pattern. The voids between the reinforcing members are filled with a ceramic fiber insulation material to limit the surface temperature rise of the unexposed side of the door during a fire. A fire -resistant neoprene-coated fabric is used to seal around the edges of the door panels. The door is opened and closed by an air cylinder, attached to the over-head linkage and operated by lanyards on either side of the door. The door design includes an optional airlock manway for drifts of adequate width.

Jan 1, 1983

Provide a portable crushing capability to keep conveyor haulage close to the working face and permit more efficient and safer ore handling in low headroom, hardrock mines. Approach A readily portable jaw crusher is used which meets machine size, feed rock size, product size, and throughput requirements for low headroom, hardrock mines. How It Works The crusher is mounted on wheels to expedite frequent moves and to allow crushing of mined rock or ore near the working face. The crushed product is then placed on conveyor belts that are ex-tended as the crusher is moved. Keeping crushing and conveyor haulage near the face minimizes the haulage distances for trucks and loaders. Loading and haulage of run-of-mine ore is frequently the highest operational cost in underground mines. These costs can be significantly reduced by use of a belt conveyor, which is a common practice in coal and other soft mineral mines. The new low-profile hard rock crusher gives the same advantage of extensive belt haulage capabilities to low headroom, hardrock mines. The low-profile crusher will accept feed up to 30 inches when operating under 11 feet of headroom. The headroom required for crusher operation was reduced by tilting the jaws, feeding the crusher horizontally, and placing the eccentric shaft at the back or in a horizontal plane with the jaws. Material is fed by an

Jan 1, 1981

By H. W. Frevert, A. C. Fieldner, S. H. Katz

"The Bureau of Mines, in its investigations of as masks for use in mines and allied industries tests masks that are voluntarily submitted by manufacturers for examination, and issues approval certificates for masks that meet the bureau's specifications. This paper describes the tests that were conducted on an ammonia gas mask by the Bureau of Mines, which successfully met all requirements and tests for ammonia, masks. The mask tested, known as the GMD ammonia gas mask, is manufactured by the Mine Safety Appliances Co., Pittsburgh, Pa. This ammonia gas mask, which forms a pocket over the face and allows breathing through the nose, consists of a face-piece with non-shatter eyeglasses; this is attached by means of a corrugated rubber tube to a canister supported on wearer's chest by a harness. The canister is green in color and is of tinplate construction. It was a disc valve at the bottom to prevent exhalation through the canister. The filling of the canister consists of a specially impregnated activated charcoal, about 750 c.c. in volume and weighing about 520 grunn. The material is supported above the check valve by a dome of wire screen covered with toweling. Above the granular material is a filter of absorbent cotton screens, and all materials are hold firmly in place by pressure from strong"

May 1, 1926

By Doug Tesarik

The study of neutrinos?particles infinitesimally smaller than atoms?would be significantly advanced if a deep underground facility were available that would filter out unwanted cosmic radiation. Encouraging progress has been made in satisfying the criteria for such a facility with the selection of the Homestake Mine in Lead, SD, by the National Underground Laboratory Committee as the recommended site for a National Underground Science Laboratory (NUSL). The Homestake Mine is America?s oldest and deepest underground mine, and its well-maintained infrastructure to depths of 2438 m below the surface makes the mine an excellent site for such a laboratory. The investigation reported here is an initial study of the stability of the first of the proposed chambers. A cylindrical room with a dome-shaped roof and floor was analyzed in three dimensions using the finite-difference program FLAC3D. The results were compared to recommended support requirements based on Barton?s Tunneling Quality Index, Q. Based on model results and observations from previous mining studies, large rooms with 50-m roof spans can be constructed and will remain stable at 2141 m below the surface in the Poorman Formation when the rock is reinforced with cable bolts. Construction may be possible at lower levels in the Yates Formation if more extensive laboratory strength tests confirm initial results.

Jan 1, 2002

By Harry Dobroski, Larry G. Stolarczyk

Theoretical and experimental research sponsored by the U.S. Bureau of Mines shows that medium frequency (MF) electromagnetic (EM) signals propagate great distances in an underground environment such as a tunnel or mine. This propagation is enhanced by different mechanisms associated with the geology, and with the existence of metallic conductors in the entryways. In stratified geologies, a transverse electromagnetic (TEM) mode of signal propagation is possible if a low conducting layer is bounded above and below by higher conducting layers. In general, the difference in conductivities must be at least several orders of magnitude. Such geological waveguide conditions often exist in underground mines. Propagation via the waveguide effect is known as the "seam mode" of propagation. Another mode of propagation, the "tunnel mode," exists in underground entries with electrical conductors such as power cables, metal pipes, and phone lines. A monofilar mode of propagation exists when signals are impressed upon conductors and return via the surrounding rock. A bifilar mode of propagation exists when all signals exist only on local conductors. In a given location there is a combination of monofilar and bifilar modes that make possible an interaction between the conductors and a transmitting device in a tunnel or entryway. Signals can be impressed on or received from local conductors via magnetic dipole antennas (loops) or line couplers.

A construction material based on plasticized sulfur and mineral aggregate, that is superior in corrosion resistance and strength to portland cement concrete. The material can be used in the chemical, metallurgical, and fertilizer industries, and will also provide an attractive market for by-product sulfur resulting from compliance with pollution regulations. How It Is Made Sulfur concrete is thermoplastic material. Plasticized sulfur is mixed with sand and gravel aggregate heated to 375-400° F. The sulfur melts and acts as the binder or cement. The sulfur concrete is poured hot and sets at a temperature of 200° F. Full strength is attained in a few hours, compared to several days for portland cement concretes. Sulfur concrete even pours and sets in freezing weather. Although unmodified sulfur with aggregate will produce a sulfur concrete with good initial properties, it undergoes crystallographic modifications, and deteriorates with time, particularly when exposed to moisture or freeze-thaw conditions. The Bureau of Mines has developed plasticizers which, when reacted with the sulfur, give sulfur concretes with excellent moisture and freeze-thaw resistance. The plasticizers are based on mixtures of dicyclopentadlene (DCPD) and ollgomers of cyclopentadiene. About 5 percent by weight of the plasticizers is reacted with molten sui fur for several hours. The sulfur cement can be used directly or allowed to solidify for easier handling and storage.

Jan 1, 1981

By C. W. Lee

"Introduction of diesel engines in underground mines may generate severe health hazards associated with exhaust contaminants. One of the most important parameter in determining the optimal air quantity for hazard reduction is the exhaust dispersion. Through analyzing the exact solution of the diffusion equation and its approximation by finite difference method(FDM) , this paper aims at doing a fundamental research to find an efficient dispersion model suitable to the domestic mines. Diffusion coefficients are likely to be small in the underground airways with high ventilation resistance. This makes concentration profiles similar to the convection-based step functions. It is the case for fixed as well as moving engines. Concentration estimation by exact solution is almost impossible in the case of either a single engine moving at a variable speed or the existence of multiple engines. Application of FDM to the diffusion equation including turbulent dispersion results in the various problems; unstable concentration profiles depending on the engine location, nuctuating concentrations near the engine, and overestimation of the dispersion region of which error grows with waning diffusion coefficient.Convection-based dispersion model is found to fit well for dynamic simulation of exhaust dispersion from multiple diesel engines in the airways showing low diffusion coefficients. Its suitability is more likely in the regions with frequent equipment passage. Published"

Nov 1, 1995

By R. Andre, R. L. Grayson, T. Simonyi

"Results from research directed at determining the reason(s) for the ""rank factor"" in correlations between coal workers' pneumoconiosis incidence and coal seam of employment are presented. Using compliance dust samples collected from two longwall panels operating in coal seams of widely different rank, respirable particles were identified by mineral species under manual scanning electron microscope (SEM) energy dispersive x-ray (EDX) analysis and then further characterized by their physical diameter, general shape, and periphery angularity. Size fractional, mineralogical variations are presented.Of primary significance, the percentage of mineral particles from the higher rank coal seam that were uncontaminated by non-stoichiometric elements for a specific mineral species was twice that of those in the lower rank seam. The relationship held for each mineral species, including quartz. This fact may form the basis for the ""rank factor"" known to exist as well as provide a reason for the contradictory role of quartz and other minerals in previous CWP studies.An important subsequent research priority is now focusing on determining the percent¬age of all respirable dust particles that are minerals versus single-phase organic or multi-phase organic-inorganic complexes. This effort will be accomplished usingautomated SEM-EDX. The mineral purity factor will be developed further, but additional emphasis will be focused on determining the extent of inorganic inclusions in organic particles."

Jan 1, 1988

By R. P. Vinson, D. P. Tuchman

The personal dust monitor (PDM) is a sampling device developed for measuring the personal exposure to coal mine dust of mine workers. The device is based on proprietary technology known as the tapered element oscillating microbalance (TEOM) originally developed as a fixed- site environmental particulate mass monitor by Rupprecht and Patashnick Co., Inc., Albany, NY. Currently, the monitoring of exposure to coal mine dust relies on periodic samples taken by traditional coal mine dust sampling units that use a cyclone, filter, pump, and laboratory measurement of the filter mass. Better measurement of mine dust levels has been the goal of industry and labor for nearly two decades. PDM technology offers accurate, end-of-shift and near real time assessment of worker dust exposure. Laboratory and underground tests compared measurements taken by a prototype PDM-2 (a two-piece TEOM) to the average of multiple personal dust samplers monitoring the same space. In the range of mass loadings P between 0.5 and 4.0 mg/m the PDM met a 25% accuracy criterion 95% of the time with 95% confidence. However, some questions still exist about potential bias between types of coal. The prototype two-piece device is in the process of being combined into a single unit that also contains the miners' cap lamp creating a more ergonomic dust sampling system.

By E. C. Bennett

"INRTODUCTIONVarious methods of making leakage tests have been tried during a study of losses in the transmission of natural gas. This work has been carried on by the Bureau of Mines in cooperation with the Natural Gas Association of America. Results of torts show that the ""shut-in -pressure-drop"" method described by Rawlins is the most accurate and reliable; therefore its use is recommended. This paper describes a graphic method for computing the rote of leakage from the fall in pressure and change in temperature determined by the ""shut -in pressure-drop"" method of testing.METHOD OF MEASURING PRESSURE DROPThe gas is ""shut in"" line to be tested and is not allowed to escape except through existing leaks. The leakage causes the pressure in the line to fall. The charge in pressure is obtained with a dead weight gage. Approximate results may also be obtained from readings on a good spring test gage. Numerous tests show that the dead weight gage is more sensitive to small changes in pressure than spring gages.The temperature of the gas in the line is observed simultaneously with each pressure reading. Temperature changes affect the pressure exerted by a given quality of gas ""shut in a line, end since the rate of leakage from a closed system is directly proportional to the rate of pressure drop, fluctuations in temperature must be considered."

May 1, 1926

This report summarizes the work performed by the Bureau of Mines on the development of analytical procedures for determining metallic and interstitial impurities in high-purity tungsten. Fourteen published methods and seven unpublished methods are briefly described. Carbon, hydrogen, nitrogen, and oxygen, in microgram to higher quantity levels, can be determined by several methods. Trace levels of 29 metallic impurity elements can be determined by optical spectrography, X-ray spectrography, and other instrumental methods.

Jan 1, 1968

By Robert P. Vinson

A sequential sampler, based on the Archimedes screw, has been developed by the Bureau of Mines. Its initial purpose was to collect air samples during tracer gas studies in underground mines. However, the basic concept can be applied to other sampling needs, including sampling of liquids. A prototype was built and successfully tested in the Bureau's Experimental Mine at Bruceton, Pa. The simple design makes the sampler inherently durable and low in cost.

Jan 1, 1976

By Edmund S. Leaver

This information circular is written is response to the marry requests for information on the recovery, or reason for poor recovery, of fine gold by the amalgamation process. Checking Gold Content Experience has shown that in many cases error has been made because the true told content of a particular sample or deposit was not known. Fire assays of representative samples give accurate results and should be considered final in determining the gold content.

Jan 1, 1928

Objective Develop a method to warn of hazardous conditions and enhance safety during operation and inspection of vertical mine shafts and hoists. Background Mine hoisting is the most critical and potentially the most dan¬gerous operation in underground mining. Many hazards are related to falls of miners and materials, ground instability, and malfunction or lack of safety devices. All have the potential to cause a cata¬strophic accident. A condition known as "slack rope" is particularly dangerous, expecially if it occurs without the operator's awareness. The most common occurrence of slack rope is in metal or nonmetal mines that have a history of ground control problems near the "haft. Approach Studies of hoist safety features and Mine Safely a and Heath Administration (MSHA) accident statistics suggests a need to measure wire rope tension, conveyance speed and position, and shaft guide misalignment. The most accurate data are obtained directly from the conveyance. Such data could warn of potentially dangerous situations during hoisting operations, as well as during inspections, maintenance, and lowering of large equipment. Figure I shows the concept for monitoring wire rope tension, conveyance position, and guide displacement. Progress to Date A conveyance-mounted system has been developed that monitors rope tension: hoist conveyance position, speed, and load; and shaft guide misalignment. A "flex-beam" load sensor mounted just above the- conveyance protects against slack and tight rope. The measurements are transmitted 60 times a second via wireless equipment from the conveyance to the hoist room. An encoder mounted on the conveyance eliminates the need to correct the position because of rope stretch. Figure 2 shows the encoder wheel and guide displacement sensors being mounted on a cage in¬spection deck. A potentiometer monitors misalignment of the shaft guides during inspections. Information about the cage or skip can be acquired by the shaft inspector using a hand-held indicator. Inspection can also he conducted remotely from a station or hoist room using the wireless link to a laptop computer. Figure 3 shows test results from a simulated slack rope condition. Patent Status NIOSH has a patent pending on this device entitled "Cable-Load¬Sensing Device." For More Information NIOSH is seeking cooperators to assist in further tests of this technology to improve hoisting safety. Additional information can he obtained by contacting Michael J. Beus, Steven Iverson, or Elaine Cullen, Technology Transfer Officer, NIOSH, Spokane Research Laboratory, Spokane, WA 99207 at (509) 354-8000.

Feb 1, 1998

By H. P. Greenwald, G. E. McElrey

"Part IV.- The Resistance Caused by Right-Angle Bends. IntroductionThis paper deals with the fourth phase of an extensive research on coal-mine ventilation factors. A comprehensive report of the entire work is in course of preparation, but abstracts of the various chapters are being prepared in order to make the major results public as rapidly as possible. Parts I, II and III were issued as Serials Nos. 2621 (July 1924), 2647 (October 1904) and 2671 (March 1925) and dealt with the resistance of unobstructed entries, the resistance due to mine cars and, the resistance of timbered entries respectively.Description of the Tests With the last cutthrough between the two butt entries of the test section in the Experimental Mine open, the air flow was deflected, around two right-angle bends in the same direction, the butt entries being 50 feet center to center and approximately 6 by 9 feet in cross section. Each bend had a dead end opening off of it; that at the first bend was in the direction of flow and that at the second bond was at right angles to the flow. For a primary test condition the inner corner of each bend was trimmed square and the dead ends were closed off with board brattices set flush with the line of the cut-through.The two corners of the first band were, then modified both independently and in conjunction. Various modifications of both bends in conjunction were also tested with rather surprising results as to the effect of conditions at the first bend, upon the pressure losses at the second. To confirm the theory developed to fit these results a series of tests were made to give a direct comparison of the -pressure losses as between two bends with the air flow deflected in the some direction at each and with the air flow deflected in opposite directions. The former is designated ""double"" and the latter a ""reversed"" right-angle bend. This series of tests was conducted, however, on the bends at one of the intermediate cutthroughs at which the flow could be deflected us either direction at the second, bend. Here also the average cross-section was 6 by 9 feet and the bends were 50 feet apart."

Jan 1, 1928

By F. W. Jones

The perturbation of alternating electromagnetic fields by three-dimensional structures is considered. The general model is that of a semi-infinite conducting half -space which consists of regions of different conductivities. A numerical method is used to obtain the solution for the equations and boundary conditions. The effects on the fields at the surface of the half-space due to the conductivity discontinuities are shown by three-dimensional amplitude and phase plots.

Jan 1, 1973

By Wils L. Cooley, Herman W. Hill

'The electrical behavior of ground beds is often quite different from what would be expected based on experience with electric circuits. An explanation for this unique behavior is given, through means of an analogy, which should promote intuitive understanding of ground beds. The nonmathematical development of the text is complemented by an extensive appendix which describes the details of ground bed calculations. This work was supported by U.S. Bureau of Mines contract G0144138.

Jan 1, 1979

By Martin Harper

This paper concludes a five year program on research into the use of a portable X ray fluorescence (XRF) analyzer for analyzing lead in air sampling filters from different industrial environments, including mining, manufacturing and recycling. The results from four of these environments have already been reported. The results from two additional metal processes are presented here. At both of these sites, lead was a minor component of the total airborne metals and interferences from other elements were minimal. Nevertheless, only results from the three sites where lead was the most abundant metal were used in the overall calculation of method accuracy. The XRF analyzer was used to interrogate the filters, which were then subjected to acid digestion and analysis by inductively coupled plasma optical emission spectroscopy (ICP OES). The filter samples were collected using different filter holders or "samplers" where the size (diameter), depth and homogeneity of aerosol deposit varied from sampler to sampler. The aerosol collection efficiencies of the samplers were expected to differ, especially for larger particles. The distribution of particles once having entered the sampler was also expected to differ between samplers. Samplers were paired to allow the between sampler variability to be addressed, and, in some cases, internal sampler wall deposits were evaluated and compared to the filter catch. It was found, rather surprisingly, that analysis of the filter deposits (by ICP OES) of all the samplers gave equivalent results. It was also found that deposits on some of the sampler walls, which in some protocols are considered part of the sample, could be significant in comparison to the filter deposit. If it is concluded that wall deposits should be analyzed, then XRF analysis of the filter can only give a minimum estimate of the concentration. Techniques for the statistical analysis of field data were also developed as part of this program and have been reported elsewhere. The results, based on data from the three workplaces where lead was the major element present in the samples, are summarized here. A limit of detection and a limit of quantitation are provided. Analysis of some samples using a second analyzer with a different X ray source technology indicated reasonable agreement for some metals (but this was not evaluated for lead). Provided it is only necessary to analyze the filters, most personal samplers will provide acceptable results when used with portable XRF analysis for lead around applicable limit values.

Jan 1, 2007

By A. A. Giardini

This report represents the results of a literature study on boron nitride and related substances. The purpose of the study was to find Information that might be of value for production of a new, hard modification of boron nitride preferably in single crystal form. The report consists of a review of the major developments in boron nitride research, a discussion of the results, tabulations of physical and chemical properties;, conclusions drawn from the study, and a bibliography.

Jan 1, 1953