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Continuously separate mixture of non-magnetic materials (such as scrap, precious metals, or certain ores) at a reasonable cost. Approach Nonmagnetic materials of different densities are rapidly float/sink separated by an augmented lifting force produced In a magnetic fluid (liquid) by the effect of an external magnetic field. The magnetic fluid is a colloidal suspension of magnetite In kerosene, prepared by a low-cost process. How It Works Separation is accomplished in an open trough filled with magnetic fluid. A magnetic field is established in the fluid, by energizing an electromagnet having poles on each side of the trough. Due to the design of the magnet poles and air gaps, the magnetic field is strongest at the bottom, about 10,000 oersteds, and uniformly decreases in strength to about 2,000 oersteds at the top of the fluid. Therefore, the magnetic field gradient increases with depth. The magnetic force attracts the entire separation medium (magnetic fluid) creating a reaction force of equal magnitude and acting in the opposite direction. This reaction created within a magnetic fluid/magnetic field combination is called a magnetic levitation force. It increases with the field strength. In this case because the magnetic field is strongest at the bottom of the trough, the magnetic levitation force will quickly float lighter material while heavier material sinks.

Jan 1, 1980

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.

Improve the health and safety of underground mine workers by finding ways of keeping them away from unsupported areas of the mine. Background Roof falls have been the leading cause of fatal accidents in the underground coal mining industry. During 1985-89, 92 coal miners were killed by falls of roof and rib, with more than 4,000 miners injured. According to accident investigation reports from the Mine Safety and Health Administration, 47% of the victims of these fatal roof fall accidents were in the area of unsupported roof al the time they were killed. There is an urgent need to find out why miners go under unsupported roof and to devise strategies for preventing this unsafe behavior. Approach To discover what can be done to prevent miners from going under unsupported roof, confidential interviews were conducted with 297 miners who work in the face crews of 6 different coal mines. The interview topics included company policies and actions regarding going under unsupported roof, how foremen react to people who go under unsupported roof, circumstances likely to cause some people to go under unsupported roof and how to prevent these situations, and observations concerning those who go under unsupported root.

Jan 1, 1991

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

Identity the difficulties of establishing vegetation on mining-related wastes resulting from adverse chemical, physical, and biological properties; describe the ecological and soil factors affecting the relationship between mycorrhizal fungi (soil microorganisms) and plants; and evaluate the feasibility of establishing vegetation on mine waste by introducing mycorrhizae. Problems in Revegetation Successfully using vegetation to stabilize a situ disturbed by mining-related activities depends on knowing the chemical, physical, and biological characteristics of the site prior to, or at the time of, stabilization. The primary objectives of mine land reclamation are to minimize environmental degradation and to facilitate the re-establishment of a functional plant-soil system. Mining disturbances can significantly alter the physical, chem¬ical, and biological characteristic of a site, thus affecting plant establishment, survival, and growth. The physical disturbance caused by the removal and replacement of soil and overburden, together with the waste material from ore processing, affect the chemical, physical, and biological process within the disturbed soil or waste. Additionally, variability in soil properties results from differences in climate, topography, vegetation, and parent material of the site.

Jan 1, 1993

By John C. Edwards

To have the capability to predict the development of localized spontaneous heating within a porous coalbed that is subjected to forced air ventilation or in an otherwise quiescent environment in which buoyancy develops, the Bureau of Mines developed three time-dependent mathematical models, which were used to calculate the temperature increase associated with chemisorption of oxygen by the coal. In each model, spontaneous heating is driven by an Arrhenius first-order reaction between the oxygen and coal. Two models are two-dimensional, and one is one-dimensional. In the first two-dimensional model, a constant-velocity forced convection airflow is specified; and in the other, buoyant flow is allowed to develop in the absence of forced convection. The third model evaluates the airflow from Darcy's law and a specification of the pressure at the surface of a one-dimensional porous coalbed. Numerical computations demonstrated how each model could be used to predict the onset of spontaneous heating when the porous coalbed was subjected to constraints of an imposed internal heat source or a high- temperature airflow. The effects of particle size and coalbed compaction upon spontaneous heating were examined with the third model.

Jan 1, 1990

To cool hot working environments in deep mines more efficiently, while substantially reducing the maintenance required by presently used cooling coil heat exchangers. Approach A mine's chilled water supply cools fresh air enroute to hot working areas, in an improved, direct-mixing heat exchanger. How It Works Warm, fresh ventilation air traveling through the mine's ventilation tubing enters the lower portion of the cooler heat exchanger through a large round opening designed to accept the ventilation duct. This air flow is turned upward and evenly distributed by egg-crate lattice and pair guide vans at the bottom of the cooler. On the diagram, warm air enters at the bottom left. As the air moves upward through the cooler, it passes through a plastic or wire mesh pad which is arranged so that it offers the most resistance to upward airflow immediately above the cooler inlet: this more or less equalizes the upward air flow along the length of the cooler. The air next moves through the cold water sprays, and then through a wire-mesh demister pad before exiting from the cooler at the top right. Cooling of the air is accomplished in several stages. As the incoming air passes through the lower plastic or wire mesh pad, it is exposed to water flowing downward through the pad to the water sump. This is water that has fallen from the sprays or dripped from the upper wire-mesh mist eliminator. This water is slightly warmer than the spray water since it has already done some cooling,

Jan 1, 1981

Design a new acoustic monitoring system to more accurately forecast impending rock bursts, and to assist in understanding the rock burst phenomenon. Background Rock bursts arc the major cause of injuries and deaths in deep underground mines in the Silver District near Wallace, ID. Bureau investigations of the rock burst phenomenon resulted in significant improvements in computerized acoustic technology, and achieved limited success in forecasting several large events. Research demonstrated that the location of rock noise, and the rate at which these events occur, are indicators of areas that could fail violently. In minewide monitoring, the typical array of acoustic sensors (geophones) is arranged to cover an entire mine with 16 to 32 separate instruments. The mines intended to be covered may be 7,000 feet in depth and up to several miles in extent. While such an arrangement is capable of detecting and locating large seismic events (rock slippage along natural fractures or faults), the geophones are too far apart to accurately locate mining-induced events at the active workplaces. The Bureau devised a strategy to concentrate the geophones into typical slopes (mining areas about 200 by 500 feet) to record the rock noise in areas where the miners work. By using such a dense geophone array at a mine, the Bureau provided event location and rate information to mine operators who removed workers and ceased production from active mine areas that subsequently suffered rock bursts.

Jan 1, 1989

By W. Blake, J. K. Whyatt, T. J. Williams

Researchers at the U.S. Bureau of Mines collected and analyzed over core measurements and other indicators of in situ stress characteristics at the Lucky Friday Mine, Mullan, ID. An analysis of these data revealed that significant local variations in in situ stress are present in this mine and that these variations existed prior to mining. High stresses were found to be associated with the most competent strata and a locked section of a fault. An estimate of the predominant stress field was developed for mine-wide modeling. The estimate shows that the greatest principal stress was oriented north of northwest. This information should provide a basis for mine-wide structural modeling of the Lucky Friday Mine and should generate important insights into localized stress conditions, which may significantly affect both local and mine-to-mine variations in seismicity induced by excavation.

Jan 1, 1995

By William J. Wiehagen

This is the third in a series of four articles that discuss underground fire-fighting preparedness. As with the first two articles, it is based on interviews with 214 miners conducted at 7 underground coal mines (referred to as Mines ?A? through ?G?) by researchers of the National Institute for Occupational Safety and Health?s (NIOSH) Pittsburgh Research Center [Vaught et al. 1996]. In the first article, the authors presented an overview of the study conducted by NIOSH on mine fire response preparedness and provided a general perspective on underground mine fires. The second article discussed miners? preparedness to evacuate a fire and their experience with incipient fires. In this article, we describe miners? experience in fighting underground mine fires and present their perceptions of training and readiness for fire-fighting.

Jan 1, 1997

By M. A. Elliott, H. H. Schrenk, L. B. Berger, John C. Holtz

"INTRODUCTION Among the hazards that may attend the use of Diesel engines in mines, tunnels, or other underground operations the presence of harmful or objectionable constituents in the exhaust gas must receive due consideration to prevent the formation of unsafe or unhealthful working environments in these places. Previous reports of this series have presented discussions of the composition of exhaust gas from engines in proper mechanical condition, 6/ the effect of adding some of the exhaust gas to the intake air of the engine, 7/ the effect of operation in atmospheres containing natural gas, 8/ and the effect on exhaust-gas composition of conditions that influence the characteristics of fuel injection in Diesel engines. In all these studies the properties of the fuels used were in general conformity with specifications usually recommended by the manufacturers of Diesel engines. In evaluating the physiological significance of the various components of the exhaust in these experiments, the toxic or objectionable gases determined were carbon monoxide, carbon dioxide, oxides of nitrogen, and aldehydes. Because of the low sulfur content of' these fuels, compounds such as sulfur dioxide and sulfur trioxide were not determined, although in discussion of the test results attention was directed to the fact that if fuels of higher sulfur content were used, the concentration of such compounds in the exhaust would become a significant factor in establishing the quantity of ventilating air required to furnish satisfactory dilut1on of the exhaust gas in underground working places."

Jun 1, 1943

By P. A. Bloom

Arsenic-containing flue dusts are currently being stockpiled by several nonferrous smelters in the United States. These stockpiles are a source of environmental concern since the dusts can be transported by wind and contain water-soluble arsenic. The stockpiles also represent an alternate source of metals. To provide a quality environment, the Bureau of Mines investigated a process to make environmentally acceptable the discard of arsenic obtained from the treatment of arsenical flue dust. The process includes (1) leaching arsenic from a lead smelter copper dross flue dust, (2) fixing arsenic as an insoluble compound, and (3) recovering other metal values. Overall results of acid-leaching tests on lead-smelter flue dusts showed that H2S04 dissolved 80 to 90 percent of the As, Zn, and Cd, and up to 86 percent of the In. Pb, Ag, and Au remain in the residue, which can be recycled to the smelter. Indium was recovered from the strong acid leach solution by solvent extraction; arsenic was fixed in a stable form by precipitation with Fe2(S04)3 and CaO or CaC03.

Jan 1, 1982

Improve the effectiveness of person-wearable self-contained self rescuer (PWSCSR) training by enhancing the memory retention of trainees in proper donning procedures. Background In the fall of 1989, a total of 185 miners and inspectors were trained by Bureau of Mines personnel to don the SR-100 PWSCSR using the Bureau's 3+3 method. With the exception of a few individuals, miners were trained underground in an area set up within their working sections. The instructional protocol was as follows: (1) after placing an SR-100 simulator (equipped with a cleaned and disinfected mouthpiece assembly) on the mine floor in front of the worker, a researcher guided him or her step-by-step through the complete donning procedure, (2) the miner was required to perform each step slowly, methodically, and correctly while being talked through the sequence, (3) following this pre-practice instruction, the apparatus was repacked and the subject donned the device without coaching, while being evaluated, (4) if an error was made, the worker received corrective feedback, the unit was repacked, and the entire donning trial was redone. This procedure was repeated until the miner achieved a perfect 3+3 sequence.

Jan 1, 1990

By Rudolf E. Greuer, Linneas W. Laage, Xinton Chang

Data or input files are used to describe the mine's ventilation system and physical characteristics necessary for ventilation calculations as well as the physical or mechanical disturbance to be modeled and simulated Data files are organized into lines of categories or groups of information Each line contains multiple sets of information or data items Data lines are read by the program, and the data items provide information to the program variables The data file is in American Standard Code for Informa¬tion Interchange (ASCII) format, sometimes called a DOS text format Creation or modification of a data file is accomplished with text editor software Most word pro¬cessors are also capable of making the required ASCII type files A sample data file and its associated output are included in appendix B. When selecting software for editing the data files, the user should be aware that the software will also be used for viewing the output of the simulation The output file can be quite large (several megabytes), if a lengthy simulation is performed The output can be sent to a printer for a hardcopy fisting, however, the user should also be aware that most printers currently used with PC's print at rates of 100 to 300 characters per second and large output files may take several hours to print Viewing the output with a text editor can save much time and paper DATA FILE MANAGEMENT The data files describing the event and mine to be simulated can reside either on a floppy disk or in a directory on the hard disk drive When the program starts, the user is prompted for the data file location and name The user response is in the form of a standard DOS path and file name For example, if the data file is on a floppy disk located in drive B and the disk has a directory MYMINE with the data file MYDATA DAT in that directory, then, at the prompt

Jan 1, 1990

By C. N. Schuette

"The production of silica and magnesia crucibles in the induction furnace was attempted and achieved in the laboratory of the Pacific Experiment Station of the United States Bureau of Mines. This work was undertaken at the request of other stations for laboratory crucibles of a certain specified wall thickness and capacity.The essential new parts of this work are the development of a technique for the high-frequency furnace production of silica crucibles of greater wall thickness than could be readily fabricated from commercial fused silica, and for heavy-walled magnesia. crucibles of great density and mechanical strength. A considerable bode of patent literature on the Production of fused silica ware in resistor-type furnaces was examined, but it furnished no significant help for the present problem. Similarly sintered magnesia refractories are often made for technical purposes, but for use at temperatures of 2000o C. or over, the material must be sintered at higher temperatures than can be attained by combustion firing, and the very great shrinkage encountered at these temperatures requires special methods. Small crucibles. of magnesia fused in the electric arc have been made by Tritton and Hansen,3 but the practical size of such containers is very limited.Many different methods of making crucibles in the induction furnace were tried before satisfactory results were obtained. The following description covers only the most satisfactory method, which produced crucibles of excellent quality in a reasonable time and with a moderate expenditure of power and materials."

Oct 1, 1929

To identify the most successful methods now in use for controlling respirable dust in longwall mines using double-drum shearers. Approach Conduct dust surveys at six longwall mining sections that use double-drum shearers and are regularly in compliance with the Federal Respirable Dust Standard, to identify effective dust control techniques. The selection of mine sites was based on recommendations provided by the Mine Safety and Health Administration. Instantaneous and short-term gravimetric instrumentation make it possible to isolate longwall dust sources and to determine the effectiveness of dust control techniques. (These procedures were developed by the Bureau of Mines, and are described in detail in Technology News Bulletins 134 and 135.) Production levels, and seam heights at each of the six longwall sections were: 53", 700 tps; 60", 800 tps; 72", 1000 tps; 79", 1500 tps; 84", 2000 tps; 96", 1500 tps. Survey Results Three effective dust control techniques were identified. 1. Shearer Operators on Intake Side of Lead Drum-At all mines surveyed, an important factor in controlling dust exposures at the shearer is the use of a cut ting sequence that allows the shearer operators to work most of the time on the intake air side of the lead drum. Dust profiles, like those plotted from data at two mines (see the graphs), show the large gradient in dust concentrations that can

Jan 1, 1982

Enhance coal mine worker safety and productivity by developing a means to control and predict coal mine mountain bumps. Approach The Bureau of Mines has been engaged in extensive research to understand coal mine mountain bumps and their effect on underground coal mining in the United States. Information was collected on the geologic conditions, mining techniques, and engineering parameters at five mountain-bump-prone mines. Although research has not yet evolved to the point where mountain bumps can be effectively predicted or controlled, such studies are invaluable for providing clues that can lead to the development of mountain bump mitigation technology. Case Study Results and Recommendations Mountain bumps in coal mines are explosions of the coalbed that violently release the strain energy stored within it into openings created by mining. Such an event is not only dangerous to mine workers, but can cause substantial amounts of damage to mine equipment, resulting in productivity loss and downtime. In a coal mine, the occurrence may cause coal to be expelled violently from the coal face or coal pillars or cause the mine floor to heave suddenly. Coal bumps are usually accompanied by a very loud noise and tremors or vibrations. Such ground failure:; usually occur in the vicinity of an active gob line in an active retreating room-and-pillar panel, or at or near the face in an advancing or retreating longwall mining panel.

Jan 1, 1989

By Kathleen Madland Kowalski

In recent years the issue of human stress response in emergency workers has begun to receive attention. This paper presents a rationale for considering human stress as a significant factor in the management of emergencies It discusses the concept of stress, Critical Incident Stress in emergency responders, and intro¬duces the Critical Incident Stress Debriefing (CISD) process. It is suggested that in a disaster, the CISD process can improve the effectiveness of response teams on site, their turnaround time on site, and post disaster time off the job. This paper, prepared by a US Bureau of Mines research psychologist, offers some ideas to the mining industry in general, mine rescue trainers and more universally, to those responsible for developing emergency management plans.

Aug 1, 1998

By Wm. C. Dean

The location of trapped miners from their seismic signals will be in- accurate if we assume the P-wave propagation velocity is a constant. P- wave velocities are anything but constant in regions about mines, so some calibration is necessary to obtain more accurate seismic locations. The reference event method compares the time arrivals of signals generated by the miners with those previously recorded from a reference or calibration event in the vicinity of the miners. This method locates the miners' position relative to the calibration source. Hence, the location of the miners is absolute if the reference event position is known absolutely, usually from surveys and mine maps. Advantages resulting from the system, besides greater accuracy, are locations independent of the velocity model assumed, the same solution from the full array and from any subset of four or more seismometers in the array (three if the miners' depth is known), fewer seismometers required, and no complex computers required for analysis. VELA Uniform experience shows that the accuracy of locations of teleseismic explosions and earthquakes is improved by an order of magnitude over locations computed from average travel time curves. Each calibration event is applicable only over a limited range. We recommend a field test of the method at a mine to measure its location accuracy, the range of effectiveness for each calibration event, the number of seismometers needed, and the number of reference events required per mine. From these experiments we could decide whether the reference event method was useful and, if so, what form a practical rescue system would take.

Jan 1, 1974

Reduce rockfall fatalities and injuries by using innovative blasting practices to reduce damage to the rock at the excavation limits with little or no increase in cost. The Problem Falls of highwall have been a leading cause of fatalities, injuries, and equipment damage in the surface mining industry. Although the number of highwall falls is not great, when such an incident does occur it is about 14 times more likely to be fatal or result in severe injury and damage to equipment than other types of surface mine accidents. Overbreak or damage to the rock from poor or improper blasting practices is a major factor contributing to rock falls. Presplitting or cushion blasting is the technique most often recommended for improved wall control. This type of blasting however, adds to drilling and blasting costs and is not universally accepted by the industry. Air gap presplitting techniques, also called air decks, are currently being used in some mines as a less costly alternative to conventional presplitting. Approach Blasting can cause highwall damage, but proper blasting techniques have been shown to reduce the magnitude of rockfall problems. In preventing rock falls, it is important to maintain the natural strength of the rock structure to the greatest extent possible. Improved blasting practices have three main advantages: 1) they are preventive rather than corrective in nature; 2) they are cost effective; and 3) they have a very low impact on the mining operation when properly implemented. New ways of evaluating highwall integrity, such as seismic refraction tomography, were investigated.

Jan 1, 1991