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By S. A. Matthes

This Bureau of Mines report describes a system for the dissolution of metal and mineral samples using a microwave heat source. Samples and an acid mixture are placed in sealed polycarbonate vessels. The vessel contents are heated using microwaves, digested for 2 min, and quickly cooled. After the solution is brought to a final volume, the vessel contents are heated an additional 2 min in the microwave oven. Using this method, a slag, a feldspar, and a Ni-Cu alloy were dissolved and analyzed by atomic absorption spectroscopy. Values obtained for Na, K, Cu, Ni, Si, Mg, Mn, Ca, Al, and Fe agreed with certified values and had an average relative standard deviation of 1 pct. This system results in a significant savings in time and expense over traditional methods of sample dissolution, and is ideal for preparing solutions for analysis by atomic absorption, plasma optical emission, or X-ray spectroscopy.

Jan 1, 1983

By M. J. Sapko

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) has conducted full-scale explosion experiments, to evaluate the strength characteristics of various seal designs, used for safely isolating worked-out areas in underground coal mines. Large-scale explosion tests conducted within the multiple entry section of PRL's Lake Lynn Experimental Mine (LLEM) is currently the only accepted test method used by the Mine Safety and Health Administration (MSHA), for deeming a seal design suitable for use in American mines. These explosion tests are labour intensive, expensive to conduct, and can interfere with other critical underground safety and health research programs conducted by NIOSH. The PRL has developed an alternative seal evaluation method, based on a hydrostatic pressure loading concept that can facilitate the in situ testing of seals in an operating mine. Two chambers within LLEM and one within PRL's Safety Research Coal Mine (SRCM) were used for hydrostatic pressure loading various seal designs. The results from these chamber tests compare favourably with those from the large-scale explosion tests in the multiple entries. In addition to testing seal designs at the required 20 psi static pressure level, the chamber test approach also allows for the determination of the seal's ultimate design strength. Six-scaling relationships for predicting the strength of seal designs as a function of entry size are also presented.

By Thomas R. Bur

The order of identification and in same cases the magnitude of the elastic constants of an anisotropic material depends on the orientation of the cartesian coordinate axes with respect to a set of reference coordinate axes within the material; thus confusion will result unless standard orientations are used. In this paper the relationship between the cause (the internal fabric) and the effect (the elastic properties in this case) is discussed for single crystals and for polycrystalline and amorphous materials. While reference axes based on the cause are used in the IRE (Institute of Radio Engineers) standard for piezoelectric crystals) it is shown that a reference coordinate system that would be suitable and practical for all anisotropic polycrystalline and amorphous materials must be based directly on a three-dimensional expression of the effect. The conventions offered are similar to the IRE standards for piezoelectric crystals) but use the elastic coordinates of the wave surface which can be quite readily established experimentally as the reference coordinates.

Jan 1, 1969

By Thomas R. Bur

The amplitude of the first peak of an ultrasonic pulse which has traversed the diameter of a sphere is obtained for many directions in the sphere. This amplitude is relative to an input which is held constant for all measurements on a given sphere. Since the boundary conditions, distance of travel, and the controllable experimental factors are constant for all measurements, variations in this amplitude reflect variations in the attenuation or absorption with direction. The data are plotted and contoured as an equal area projection. The attenuation symmetry is the symmetry expressed by the contour pattern. Analysis of the data from several rock types indicates that the amplitude expresses a higher percentage of anisotropy than the velocity. In most cases the attenuation symmetry appears to be of the same system as the elastic symmetry expressed by the velocity. Results are shown for three rock spheres.

Jan 1, 1969

By J. R. Wait, D. A. Hill

The feasibility of locating a buried vertical magnetic dipole source (horizontal loop) from surface measurements of the vertical and horizontal magnetic field components has been investigated by Wait (1971). , For sufficiently low frequencies, the magnetic fields have a simple static-like behavior, and a single observation of the ratio and relative phases of the vertical and horizontal field components is sufficient for location when the earth is homogeneous. However, when inhomogenieties are present, the surface fields will be modified, and source location may be more difficult. In order to obtain a quantitative idea of the surface field modifications, we consider a spherical conducting zone as a perturbation to the homo- geneous half-space. A rigorous solution for the buried sphere problem has been formulated by D'Yakanov (1959). Unfortunately, his solution is restricted to azimuthally symmetric excitation, and even then the solution is not in a convenient computational form. However, if the sphere is electrically small and is located at a sufficient distance from both the dipole source and the interface, the scattered fields can be identified as the secondary fields of induced dipole moments. The latter are equal to the product of the incident fields and the polarizabilities of the sphere. The details of the approach are given by Hill and Wait (1973). Wait (1968) has used this induced dipole moment approach for scattering by a small sphere above a conducting half-space. The method has the advantage that it is easily generalized to scatterers of other shapes for which both the electric and magnetic polarizabilities are known, such as spheroids (Van de Hulst, 1957). This concept has

Jan 1, 1973

By Peter G. Kovalchik, Lawrence W. Scott, Thomas H. Dubaniewicz, Frank T. Duda

Overheating of electric cables on shuttle cars has long been recognized as a cause of premature insulation failure leading to shock and electrocution. Use of cable reels on shuttle cars can cause excessive heat build up which, in turn, causes the cable insulation to soften and become easily damaged This heat-softened insulation reduces the life of the cable. Repeated cycling of a cable in this manner can cause premature aging of the insulation; it becomes bridle, cracks and allows electrical leakage paths to farm. These leakage paths provide the opportunity for shock and electrocution to occur if miners come in contact with the damaged section of cable. It is imperative that cable operating temperatures be maintained at safe thermal limits. This paper discusses a research project conducted by the National Institute for Occupational Safety and Health, Pittsburgh Research Center to determine dynamically the conductor temperature of reeled shuttle car cables using fiber optics technology. The research portrays typical shuttle car loading cycles (both current and time cycles). Root-mean-square current loading is calculated based on the results. The thrust of this effort is to provide the scientific basis for ampacity derating factors specifically for mine machinery using reeled cables This information will reduce the probability of electrical hazards from reeled cables

By J. Whyatt

A package of bench design programs is being publicly released by the National Institute for Occupational Safety and Health (NIOSH). These programs are designed to provide a probabilistic estimate of the likelihood that various widths of catch bench will be retained. Program modules address the mechanisms of plane, plane step path, and wedge failure. Results are drawn from statistical and geostatistical descriptions of fracture characteristics and other input parameters, and reported as the statistical chance that a given width of catch bench will survive, that is, that a catch bench will remain wide enough to catch rolling and sliding material and prevent such material from posing hazards to miners operating below. The capabilities and application of this software are demonstrated through a case example. Comparing bench width estimates obtained using geologic data with actual widths is a key step in verifying that a program is appropriate for particular site conditions and that proper statistical descriptions of fracture parameters for that site have been developed. Such verification efforts improve confidence, and hence usefulness, of this method for designing future slope benches. Development and release of these programs appears particularly timely given recent progress in photoanalysis methods, which promise to greatly reduce the cost of collecting fracture data.

Jan 1, 2004

By D. Harringtong

"There has been much writing and argument on the subject of giving bonuses to miners, quarrymen, metallurgical and chemical workers, and others as a stimulus for safe work and for work safely done. Theoretically, everyone should be careful and should not need monetary or any other type of encouragement for the prevention of accidents; as a. fact, few people are careful, and this is primarily the reason way many if not most accidents occur. A bonus, however, is not simply money given away by an employer; it must be earned, so to speak, before it becomes due; in other words, if the standard established is not reached, no bonus is paid, and in many cases some disciplinary action is taken.The United States Bureau of Mines Is asked from time to time for suggestions for rewards to mine workers who have a good attitude toward working safely or who need some stimulus to cause them to make greater or more earnest efforts toward safety for themselves and their co-workers. A recent inquiry prompted the collection of data on some safety bonus systems from reports of this bureau's field engineers and others, and some of these Now given. Bonus practice at both coal and metal mines is included because a system used at metal mines is generally adaptable to coal mines; in fact, in numerous cases, bonus systems recently started at some coal mines are based on systems in vogue and giving satisfaction some metal mines; in-some instances, also, metal mines have been able to get good suggestions from coal mines or from the cement or petroleum industries. it .should be understood that a bonus, even as applied to the encouragement of safety, does not necessarily mean payment of money; in fact, some successful bonus systems have in them no direct money exchange; hence, the bonus as treated in this paper is that defined as ""Something given in addition to what is ordinarily received by, or strictly due to, the recipient.""Acknowledgment is given here to members of the safety division of the Bureau of Mines who sent in some of the information here presented; to the Engineering and Mining Journal and Mining Congress Journal, from which some items were abstracted; to various mining officials who gave data in one form or another; and to M. von Bernewitz, of the United. States Bureau of lines who aided in framing parts of this paper."

Jun 1, 1932

By C. F. Swab

A relatively innocuous halocarbon was investigated as a substitute for the highly toxic carbon tetrachloride in the approval testing of chemical cartridges. The vapor effluent of 1,1,2-trichloro-1,2,2-trifluoroethane from chemical cartridges is continuously monitored by a nondispersive infrared analyzer. Breakthrough times for the cartridges, using the halocarbon, can be equated to those of carbon tetrachloride, if multiplied by the factor, 1.49.

Jan 1, 1970

By T. C. Phalen

"Necessary Qualities There mines are located in out of the way places, where timber is scarce and its price high, the problem of protecting it from fire risk is of considerable practical importance. Scarcity of timber for mining purposes is commonly met with in the more arid parts of the country, where, also, mine timbers are most likely to become dry, and inflammable, and where, therefore, the risk from fire is accentuated. Any effective and cheap method of securing adequate protection of such timber at the lowest possible cost is worthy of careful investigation. The use of magnesite cement has been suggested in this connection.The necessary qualities for any substance for the use suggested above may be summarized as follows: It should be resistant to abrasion, and to impact and structural stresses. It should be durable when subjected to the action of the ele¬ments, and stable to any minor derangements of the base on which it is placed. It must be relatively unaffected by changes in temperature, by the action of water, and should adhere to the material on which it is placed, and it should also be free from shrinkage cracks due to setting up the material, Magnesite cement appears to fulfill the various conditions outlined above.The elasticity of such cement is the outstanding quality which makes it desirable for exterior work. It also possesses the ability to adhere to all materials in a marked degree. Its freedom from expansion and contraction after setting is one of the principal reasons for its adhesive quality. It may be applied to old brick or stone walls, even tho they have been repeatedly covered with paint, and the quality of ad-hearing to wood makes it possible to secure a weather-proof protection to the wooden casings and trim of exterior openings. The quality of adhesion and elasticity is easily proved by applying a 1/2"" layer to a 1"" board which has been first covered with metal lath. Such a board, about 8 feet long, may be repeatedly deflected about 3"" in the center without breaking the bond to the board, or causing any cracks to appear in the magnesia cement. The ability to resist fire as well as the possession of insulating qualities are also desirable characteristics of magnesia cement stucco."

Dec 1, 1919

By G. E. McElroy

Economic solutions of problems of mine-ventilation improvement can be found by mathematical analyses of alternative methods of procedure, but, in the case of our older bituminous-coal mines, the airway network is usually so complex that mathematical solutions are too tedious to be practical. Recourse usually is made to extremely costly and uncertain trial-and-error procedures with the existing layout and equipment. The resulting errors often prove costly and sometimes create hazardous conditions. Both the economic and safely aspects of alternative methods of ventilation improvement may be rapidly and cheaply investigation with analogue computers. An electrical analogue computer, designed and built especially for analyzing mine-ventilation-distribution problems, has been placed in service by the Bureau of Mines at its Pittsburgh, Pa., Experiment Station. It is a nonlinear, low-voltage, fluid network analyzer of a type developed by Malcolm S. Mcllroy, professor of electrical engineering at Cornell University. It was designed in close coopera¬tion with Professor Mcllroy and built by the Standard Electric Time Co., Springfield, Mass. It is the seventh unit of this type to be placed in service and the first designed for mine airflow problems. The other six were designed for either water- or gas-distribution analyses. Three are much larger and more expensive units. The largest unit has a capacity of 20 sources, 576 mains, and 180 loads, or regulated-flow paths. The Bureau unit has a capacity of 5 sources, 128 mains, and 48 loads.

Jan 1, 1954

By Motohisa Kanda

The time and amplitude statistics necessary to adequately describe electromagnetic (EM) noise in mines are illustrated through computer software techniques. They are 1) Allan Variance Analyses (AVA), 2) Interpulse Spacing Distributions (ISD), 3) Pulse Duration Distributions (PDD), 4) Average Crossing Rates (ACR) , and 5) Amplitude Probability Distributions (APD) . These statistics are illustrated using data taken from a rather large store of raw analog data recorded in operational mines. The curves generated for the illustrations characterize the noise environment in the mines from which the corresponding data were taken, and should aid in the design of reliable communication systems for such mines.

To evaluate the potential for dust reduction, during blasthole drilling, of water or foam applied directly into the drill hole. Approach The Bureau of Mines tested a through-the-drill-steel water and foam injection technique in two noncoal mines to evaluate the method's potential for greater dust reduction. The tests were performed by drilling a series of blastholes for an entire face (a 90 minute time-period). For the first 45 minutes of drilling, foam or water was applied through the drill steel. Blowing ventilation was supplied to the entry about 50 feet from the face. The dust concentration measurements were made by a Real-Time Aerosol Monitor (RAM-I), and the data were read out on a strip chart recorder. The evaluation test results showed that the water or foam injection technique, when used on localized dust sources, can be an extremely effective dust control method. Small amounts of water used in this method have also allowed it flexibility to be used in water-soluble ores such as salt, gypsum, anhydrite, and trona. How The System Works Water or foam is mixed with compressed air (approximately 100-120 psi) with suitable metering systems and forced through the drill steel into the blast hole at the point of dust generation. Because the water or foam is applied at the source, minimal quantities of liquid are needed (0.2 to 0.6 gpm). These low flowrates are sufficient to just moisten the dust emerging from the blast hole, thus eliminating a major source of airborne dust. The wet drilling procedure also eliminates a second source of dust. With dry drilling, the dust from the blast hole falls to the floor. Since this can be a 15-ft drop or more, the impact can send the dust billowing up from the floor, adding to the airborne dust. With wet drilling, the moistened dust merely dribbles down the face.

Jan 1, 1982

By S. Gallagher, A. Mayton, R. Merkel

The prolonged exposure of equipment operators to shock and whole-body vibration (WBV) is linked to cumulative back, neck and abdominal disorders. In low coal mines, space restrictions make it difficult for seat suspensions to isolate operators from shock and WBV Researchers at NIOSH's Pittsburgh Research Laboratory are responding to these issues by investigating viscoelastie foams. For the full-load case, an ergonomic seat made with viscoelastie foams can isolate the shuttle-car operator from shock at 15 Hz. Researchers used results from additional foam testing using an analytical model to identify viscoelastic foams that provide shock isolation at a frequency below 5 Hz.

By J. R. Allsup

In cooperation with the Division of Advanced Automotive Power Systems Development, Environmental Protection Agency, the Bureau of Mines studied a conventional spark-ignition engine as a prime mover for use in a hybrid system. The study involved both steady-state and transient engine operation with ignition timing, air-fuel ratio, exhaust gas recirculation, oxidizing type catalytic converters, engine speed, and power output as variables. Data were obtained from two 1971 model 350-cubic-inch-displacement engines mounted on engine dynamometer stands. When the hybrid engine was operated with an oxidizing catalyst at power output levels required for a 4,000-lb curb weight hybrid vehicle, carbon monoxide and hydrocarbon emissions could be reduced to approximately 2.0 grams and 0.3 gram per brake horsepower-hour, respectively. With exhaust gas recirculation, oxides of nitrogen emission levels could be reduced to approximately 1.2 grams per brake horsepower-hour.

Jan 1, 1974

Control dust generated during mining in salt mines. Approach A machine-mounted exhaust ventilation system which moves with the cutting machine from place to place was developed. The system captures the dust at the face of the heading and exhausts it downstream of the heading in the crosscut. This helps cause fresh air from the crosscut to flow over the machine operator's position, and aids in keeping the dust cloud close to the face. How It Works The system consists of (1) a circular intake hood with a 10-inch slot extending 250 degrees around the base, bolted to the gearhead; (2) 20-inch-diameter wire-wound flexible ducting to connect the intake hood to the fan (25 ft. is allowed sufficient slack for bar movement); (3) an industrial exhaust fan capable of generating 10,000 cfm with 13 inches water gage pressure at 1435 rpm; and (4) 150 ft. of collapsible 24-inch tubing for the exhaust duct which is de-played and returned In each heading by the cutter operator and/or his helper.

Jan 1, 1983

Develop a method for mapping planar geologic features in deep underground mines where the presence of metal interferes with compass readings. Background A fundamental problem of mapping planar geologic features in deep underground mines is the presence of metal (water and air pipes, track, equipment, etc.), which affects the accuracy and consistency of compasses. Present geologic mapping methods include use of transits or theodolites, both of which are cumbersome and time consuming to use. To complicate the mapping, process each planar feature must be surveyed, and if that feature is not apparent on the opposite wall, it cannot be mapped. Another method of mapping is to stretch a tape measure between two survey spads and place a string along a planar feature on one wall and out into the opening until it intersects the tape measure. This method, in addition to being time consuming, is also inaccurate. Because detailed mapping of planar geologic features deep underground involves many repetitive measurements, a quick, accurate, and reliable method for making such measurements was necessary. The geolaser was developed to make such measurements in deep underground mines where metal interferes with conventionally used compasses.

Jan 1, 1990

By Robert G. Yewen, Ronald S. Conti

Underground mines rely on alarm systems, such as stench gas, audible or visual alarms, pager phones, telephones, and messengers to warn miners of a fire or other emergency. These systems are often slow, unreliable, and limited in mine coverage. This report describes the evaluation of a wireless signaling and warning system for underground mines. This system is applicable to both coal and noncoal mines. The work was conducted by the National Institute for Occupational Safety and Health in cooperation with TeleMagnetic Signalling Systems (TSS) under Cooperative3Research and Development Agreement No. BOM-CRDA-6200-0119. A TSS wireless ultra-low-frequency electromagnetic signaling system was installed at the Experimental Mine at Lake Lynn Laboratory near Fairchance, Fayette County, PA. A commercial smoke sensor was interfaced to a remote portable transmitter, and the alarm of the sensor was used to trigger the central evacuation and paging transmitter system during experimental mine fires. The underground/surface receivers flashed cap lamps and activated remote devices, such as strobe lights, within 30 to 40 s after the encoded signal was received. Evaluation results showed full-mine coverage of the electromagnetic field and that the encoded signal was received at the farthest point underground and on the surface perimeter.

Jan 5, 1997

By Brian G. White, Theodore J. Williams, Jeffrey K. Whyatt

Detailed mapping and examination of the site of a large rock burst at the Lucky Friday Mine, Mullan, ID, demonstrated conclusively that damage was caused by a splitting and buckling failure mechanism initiated by separation of rock into layers along steeply dipping metamorphic shear foliation subparallel to the affected crosscut. The thin tablular layers then buckled into the crosscut from both sides. Rigorous control of the burst by these layers suggests practical measures for avoiding bursts in crosscuts in the future by repositioning and reorienting openings so that splitting and buckling are reduced or precluded.

By S. Gallagher, A. Mayton, R. Merkel

The prolonged exposure of equipment operators to shock and whole-body vibration (WBV) IS linked to cumulative back, neck, and abdominal disorders. In low-coal mines, space restrictions make seat suspensions difficult to use in isolating operators from shock and WBV. Researchers at NIOSH, Pittsburgh Research Laboratory, are responding to these issues by investigating viscoelastic foams. For the full-load case. an ergonomic seat with viscoelastic foams isolated the shuttle car operator from shock at 15 Hz. Researchers used results from additional foam testing with an analytical model to identify viscoelastic foams that provide shock isolation at a frequency below 5 Hz.