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By M. Howard Berliner

"INTRODUCTION During the last 4 months of 1943, the Bureau of Mines engaged in an investigation and exploratory drilling program in the area between the Coughlin and Galena Level mines near the town of Shullsburg, in Lafayette County, Wisconsin. The work was undertaken as part of a general Bureau of Mines investigation of the zinc-producing area of southwestern Wiscon¬sin at a time when an effort was being made to increase the production of metals important to the Nation's war program.The portion of the southwest Wisconsin zinc district in the immediate vicinity of Shullsburg and the Coughlin and Galena Level mines is well mineralized. The principal ore horizon is at shallow depth, and there is evidence that relatively extensive surface mining for lead was done over a period of many years. Underground mining' for lead and zinc has continued to the present time.The Bureau undertook an exploratory drilling program in the area immediately west and southwest of the Coughlin mine workings after thorough preliminary investigations and geologic studies indicated that such work would serve to guide operators in the development of new ore reserves needed for continuance of mining operations in that area."

Apr 1, 1947

By H. H. Schrenk

[A calorimetric method3/ for the determination of benzene in amounts as low as 0.001 m has been developed recently at the U.S. Bureau of Mines Pittsburgh Experiment Station by the authors, with the assistance of chemical personnel from the Allegheny County (Pa.) Relief Works Division. The method is based on the direct nitration of either liquid or gas - phase benzene, followed by neutralization, extraction with butanone, and final treatment with sodium hydroxide which produces a violet color. The color is matched with color standards of known values. Although the method is adaptable to many conditions the primary objective was a procedure that would be suitable for hygienic investigations.]

Jan 1, 1935

By M. G. Zabetakis

At ordinary temperatures and pressures methyl ethyl ketone (MEK)-air mixtures containing between 2.0 and 11 vol.-pct. MEK and methyl isobutyl ketone (MIBK)-air mixtures containing between 1.5 and 7.5 vol.-pct. MIBK are flammable. However, MEK-bromochloromethane (BCM)-air mixtures containing at least 6.2 vol.-pct. BCM and MIBK-BCM-air mixtures containing at least 7.0 vol.-pct. BCM are nonflammable. Also, MEK-BCM-air and MIBK-BCM-air mixtures containing less than 18.7 vol.-pct. oxygen are nonflammable. To assure the formation of nonflammable mixtures when mixed with air, MEK-BCM vapor mixtures must contain at least 1.6 vol. BCM per volume MEK, and MIBK-BCM vapor mixtures must contain at least 2.8 vol. BCM per volume of MIBK; these quantities of BCM would be produced by liquid mixtures containing 55 vol.-pct. BCM in the first case and 60 vol.-pct. in the second. An MIBK-BCM-trimethylene chlorobromide mixture containing equal volumes of each liquid forms nonflammable mixtures with air at ordinary temperatures and pressures. The same is true of a liquid mixture containing 34.6 pct. (liquid volume) BCM, 34.b pct. perchloroethylene, 15.4 pct. MIBK, 7.7 pct. toluene, 3.85 pct. ethyl amyl ketone, and 3.85 pct. trimethylene bromide.

Jan 1, 1960

By Paul M. Linebarger

This paper is one of a series of digests of foreign mining legislation and court decisions prepared in advance of a general report relative to the rights of American citizens to explore for minerals and to own and operate mines in various foreign countries. This interpretation of the laws of Mexico has been pro oared from the best information available in Washington but is released subject to correction and amplification, if necessary, by the proper American diplomatic and consular officers, to whom it has been referred through the courtesy of the Department of State. INTRODUCTION Present-day Mexican mining legislation involves, not only the latest minim enactment (August 1, 1026), but many other enactments and regulations, principal among which are the Constitution, the Civil Code, the Code of Commerce, the Foreign Law, the Mining Tax Law, and. the Civil Jurisprudence of Mexico--the last-mentioned being based in Dart on Supreme Court decisions. Ere Mexican Federal Government is supreme in mining legislation because, among other reasons, a large part of the revenue of the Government must come from the fiscal control of the mines. All circulars, decrees, and rulings that affect the mines not only have their origin in the Central Government but are administered thereby. The Department of Industry, Commerce, and Labor is in control of all mines. Attention may here be called, however,

Jan 1, 1929

By LB. Berger

"INTRODUCTION The use of gasoline engines as the motive power for lift trucks, tractors, and other types of mobile equipment operated in enclosed spaces, such as industrial plants and warehouses, may create a hazard because of the carbon monoxide present in the exhaust gases of the engines; gasoline-powered equipment should not be used in mines or tunnels. Because the equipment is mobile, local ventilation usually is impracticable, and general ventilation of the spaces is nec-essary to dilute and remove the carbon monoxide. To estimate the rate of ventilation required in such situations, information is necessary on the concentration of carbon monoxide in the exhaust gas and the rate at which exhaust gas is produced under given operating conditions. The purpose of this paper is to present data that may be used in making estimates of ventilation requirements.COMPOSITION OF GASOLINE-ENGINE EXHAUST GASThe exhaust gas of a gasoline engine consists mainly of carbon dioxide, carbon monoxide, hydrogen, oxygen, and unburned hydrocarbons (usually reported as methane), together with the nitrogen present as a residue from the air sup-plied for combustion. 3/ The exhaust also contains water vapor resulting from combustion of the hydrogen of the fuel. The water-vapor content is not included in exhaust-gas analyses calculated on a ""dry"" basis and is not involved in the estimation of ventilation requirements."

Jun 1, 1947

By Thomas M. Barczak

This U.S. Bureau of Mines study evaluates factors that influence longwall support and strata interaction. The longwall system is composed of an immediate and main roof structure and three supporting foundations: longwall panel, powered roof supports, and gob waste. The main roof forms a structure that is generally supported by all three foundations, while the immediate roof acts as a beam that cantilevers from the coal face to the powered support. In most cases, shield loading involves a complex interaction of both main roof and immediate roof behavior and is a combination of loads produced from convergence of the main roof and displacements of the immediate roof caused by deformations of the cantilevered roof beam. Since the shield stiffness remains constant for all leg pressures and main roof convergence is irresistible in terms of shield capacity, the shield must be able to control the behavior of the immediate roof or floor structure for shield loading to be sensitive to setting pressures. If the goal is to minimize total shield loading, any active setting force must be offset by reduced passive shield loading to justify the active setting loads. Field data sumest that the typical reductions in passive loading do not justify the required increases in setting pressure in some applications.

Jan 1, 2010

By R. V. Ramani, A. S. C. Owili-eger

Mathematical modeling is a scientific exercise with the objective of developing simplified mathematical statements that relate to one another the same way as the processes that are being modeled. The utility value of the model is dependent on the ability of the model to closely approximate prototype behavior. Development of a perfect model, therefore, is an unrealistic objective because of the simpli¬fying assumptions made in building it. However, for a model to be acceptable for application, its operating characteristics or data generated from it should, within reasonable accuracy, duplicate proto¬performance. The validity and accuracy of a model depends on the mathematical constraints presupposed in model formulation. The final model must be tested for mathematical validity and for closeness of representation of the prototype. Mathematical validity, does not, however, imply that the model is accurate and correct but is prerequisite. Model testing and verification for the steady state model are given in Owili-Eger et al (1973). The unsteady state model has been tested for mathematical validity and found to be correct but has not yet been applied to a field condition for lack of data. However, in the application discussed below, the unsteady state model results are compared with pressure curves reported in literature and also with results from the steady state model. Coal seam characteristics and gas reservoir pressure used in this application are extracted from Kissell (1972). These characteristics are for the Pittsburgh seam, Federal No. 2 Mine, Fairview, West Virginia.

Jan 1, 1974

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

APPENDIX D DEVELOPMENT AND EXPERIMENTAL VERIFICATION OF ACOUSTIC SEAL CHECKER THEORY 1. Introduction In Section 7 of the report the acoustic seal checker concept was described in a general manner and the parameters which affect the signal level at the microphone were discussed briefly. In this appendix the theoretical basis will be presented and the experimental program described which permitted the extension of the theory into practice. The basic goal of the acoustic seal checker is to relate the reduction in sound pressure level to the size of the residual hole in the fly ash barrier. The smallest hole size that may be measured is determined by the signal to noise ratio, where the noise in this case includes the ambient noise in the mine, the internal microphone noise and the sound transmitted from the acoustic source via the flanking paths through corridors adjacent to the one being sealed. The latter source of noise can be discriminated against, at the expense of increased complexity of the acoustic system, by employing a pulsed source and pulse gating of the microphone signal set to accept sound via the barrier path and to reject the delayed flanking path signals. In order that the acoustic system be insensitive to precise source and microphone location and to permit assessment of system performance on an acoustic power flow basis, a broad frequency band of pseudo-random noise is emitted by the loudspeaker source. The preferred frequency range must be determined, the advantage of a directive source must be assessed, and the necessity

Jan 1, 1973

By Robert A. Jankowski

Through laboratory and underground studies, the Bureau of Mines has evaluated the use of passive barriers (dust shields) to help confine dust generated by longwall shearers to the face area. Laboratory studies focused first on selection of the optimum barrier design, which proved to be a simple, gobside barrier (made of conveyor belting), coupled with a headgate splitter arm, which was found necessary to prevent the dust cloud from entering the walkway at the headgate end of the shearer when cutting tail to head. Further laboratory testing was done to determine whether using passive barriers in combination with different water-spray dust-reduction methods, including the shearer-clearer system developed by the Bureau, would improve dust reduction over that from using the water sprays alone. It was found that the combination of gobs ide passive barriers plus the full shearer-clearer system was most effective, and surmised that this would be especially useful in thicker seams. However, underground testing revealed that the shearer-clearer system alone was 35 pct more effective in reducing dust contamination than when used with the gobside passive barriers, and far more effective than using passive barriers with a conventional water spray system. For such an effective system as the shearer-clearer; the reduction in avail-able space over the top of the machine actually impeded system performance; this was shom1 in both eastern and western mines. But when used with comparatively inefficient water spray systems, the passive barriers, used in combination with a headgate splitter arm, provide consider-able help in reducing dust levels in the walkway.

Jan 1, 1986

By Stephen A. Swan

Bureau of Mines research has not included analyses of mining dredge safety since 1948. Because of the increasing use of dredges, 63 fatal accidents and several hundred nonfatal injury accidents involving dredges were examined. Also, 31 working dredges and 3 dredge manufacturers were visited to acquire qualitative information. Drowning accidents represented 59 pct of the fatalities and are delineated in detail. Also, countermeasures against other hazards are discussed.

Jan 1, 1985

By A. E. Wells

"When the United States entered the World War, the heavy requirements for sulphuric acid in the manufacture of explosives made necessary a definite knowledge of the sulphuric acid capacity of the country. The Bureau of Mines, under the authority conferred by the explosives regulation act, made a thorough survey of the sulphuric acid situation. In this work, which was personally directed by the writer, comprehensive data were collected on the situation and capacities of the various acid plants, sources of supply of raw materials (brimstone, pyrite, pyrrohotite, zinc ores and concentrates, waste sulphur dioxide gases from copper smelting, and spent oxide from gas works), the principal points in regard to manufacturing processes (chamber and contact) and the uses of the acid. The results of this investigaion have recently been published by the Bureau of Mines, as Bulletin 184, entitled ""The Manufacture of Sulphuric Acid in the United States"" by A. E. Wells and D. E. Fogg. The following paragraphs on the uses of sulphuric acid are abstracted from this bulletin.Sulphuric acid is one of the most important of all chemicals, not only because of the large quantities manufactured but also because of the wide use of the acid in many different industrial works. Sulphuric acid is to the chemical industry what iron is to metallurgy. The general public, however, does not realize this fact, for sulphuric acid does not appear in the finished product as does iron and steel, but is only a means to an end. It is essential in many industries, such for example as in the manufacture of phosphate fertilizers, explosives, dyes and petroleum products. In recent years in the United States, especially in the East, the demand for sulphuric acid for chemical and metallurgical industries has been an accurate and sensitive barometer of the general business conditions. This demand for acid responds much more quickly to a general slump or boom in the industrial world than does the demand for iron and steel."

Oct 1, 1920

By Neil B. Young

Analytical results for nahcolite, dawsonite, total extractable alumina, and oil yield are presented for samples representing Green River Formation oil shales in the saline section of two cores from Colorado's Piceance Creek basin. Analyses are also reported for samples extending the analyzed section of Colorado corehole No. 3 beyond that reported previously. These data permit evaluation of the deposit for possible production of three coproducts--shale oil, alumina, and sodium carbonates--from the saline section of the formation at these sampled points.

Jan 1, 1970

By George McCaa, H. C. Howarth

"During recovery operations following a recent coal-mine explosion, 12 small fires were encountered near the break line of pillar extraction in a large panel. All of the fires except one were quickly extinguished by the rescue and recovery parties. This fire had found its way into a large quantity of loose material at a corner of the cut-through between two rooms, about 100 to 150 feet from the break line of an extensive goaf; had it been necessary to seal the fire, the inclusion of this break line not only would have made the work difficult but would have made the section hazardous as it probably would have given off gas. The fire covered a floor space of about 100 square feet and when discovered was burning briskly, with the flame extending to the roof at a height of 3 or 4 feet; it was the cause of much apprehension on the part of those in charge of the recovery operations and resulted in delaying the work considerablyThe object of this article is to describe in detail the method by which the fire was brought under control and finally extinguished, so that other persons encountering similar conditions may have the benefit of the experience.When the fire was discovered a request for rock-dust, fire extinguishers, and other fire fighting equipment was telephoned to headquarters on the surface. The promptness with which fire fighting equipment and material was provided was a big factor in finally extinguishing the fire and illustrates one of the many advantages of a good organization for fire-fighting. Material was transported in mine cars to a point on the main hauling road about 1,200 feet from the fire. It was then carried to the scene of activity by workmen. The first material to be delivered at the fire was a number of fire extinguishers of various types. The contents of 30 to 35 of these were discharged on the fire and with the aid of a small quantity of rock-dust were sufficient to smother the flame temporarily. It was the opinion of several persons who were present when the fire extinguishers were used that the acid-soda type of extinguisher gave more effective results than the two or three other types used.When the contents of all of the fire extinguishers had been exhausted the fire was temporarily smothered, but as there appeared to be danger that the flame would burst forth again, means for completely extinguishing the fire were"

Feb 1, 1929

By D. E. Banks, J. K. H. Ma, Y. Rojanasakul, J. Y. C. Ma, C. J. Malanga

There is evidence to suggest that cell injury induced in alveolar macrophages (AM) following phagocytic activation by silica particles may be mediated through changes in intracellular free calcium [Ca 2+}. However, the mechanism of silicainduced cytotoxicity relative to [Ca2+], overloading is not yet clear. To provide a better insight into this mechanism, isolated rat AMs were exposed to varying concentrations of crystalline silica (particle size< 5 µm in diameter) and the fluctuation in their [Ca2+]; and cell integrity were quantitatively monitored with the fluorescent calcium probe, Fura-2 AM, and the membrane integrity indicator, propidium iodide (Pl). Results from this study indicate that silica can rapidly increase [Ca2+]; in a dose-dependent manner with a characteristic transient calcium rise at low doses (<0.1 mg/ml) and an elevated and sustained rise at high doses (>0.1 mg/ml). Depletion of extracellular calcium [Ca 2+]0 markedly inhibited the [Ca2+]; rise (˜90%), suggesting that Ca2+ influx from extracellular source is a major mechanism for silica-induced [Ca2+]; rise. When used at low doses but sufficient to cause a transient [Ca2+]; rise, silica did not cause significant increase in cellular Pl uptake during the time of study, suggesting the presevation of membrane integrity of AMs under these conditions. At high doses of silica, however, a marked increase in Pl nuclear fluorescence was observed. Depletion of [Ca 2+] 0 greatly inhibited cellular Pl uptake, induced by 0. 1 mg/ml or higher doses of silica. This suggests that Ca 2 + influx, as a result of silica activation, is associated with cell injury. Indeed, our results further demonstrated that the low dose effect of silica on Ca 2+ influx is inhibited by the Ca2+ channel blocker nifedipine. At high doses of silica (>0.1 mg/ml), cell injury was not prevented by nifedipine or extracellular Ca2+ depletion, suggesting that other cytotoxic mechanisms, i.e., nonspecific membrane damage due to lipid peroxidation, are also responsible for the silica-induced cell injury. Silica had no significant effect on cellular ATP content during the time course of the study, indicating that the observed silicainduced (Ca2 ... ); rise was not due to the impairment of Ca2 + -ATPase pumps, which restricts Ca2+ efflux. Pretreatment of the cells with cytochalasin B to block phagocytosis failed to prevent the effect of silica on [Ca2+]; rise. Taken together, these results suggest that the elevation of [Ca2+]; caused by silica is due mainly to Ca2+ influx through plasma membrane Ca2+,channels and nonspecific membrane damage (at high doses). Neither ATP depletion nor Ca2+ leakage during phagocytosis was attributed to the silica-induced [Ca2+]; rise.

Nov 1, 1995

By Kenneth L. Rubow, Virgil A. Marple, Bruce K. Cantrell

"In a cooperative study by the University of Minnesota and the U.S. Bureau of Mines, diesel exhaust and mineral dust concentrations have been measured for aerosols generated in the laboratory and in five underground coal mines. Three mines utilized diesel-powered haulage equipment and two used all-electric equipment. Two source apportionment techniques have been applied to differentiate between the mineral dust and diesel exhaust aerosol concentrations measured. The first technique, using a micro-orifice, uniform deposit impactor (MOUDI) for size selective sampling, is based on modeling aerosol size and the premise that the diesel exhaust portion of the aerosol is predominantly submicron and the mineral dust portion is mostly greater that one micrometer in size. The second technique, Chemical Mass Balance (CMB) modeling, was used to referee the analysis of diesel exhaust and mineral dust aerosol concentrations from the size selective sampling results.The MOUDI size distribution data were modeled to obtain parameters describing the fine and course fractions of the sampled aerosol and to estimate the contributions to each mode from both mineral dust and diesel exhaust aerosol sources. The results showed the size distribution of the mixed aerosols exhibited two definite modes with the minimum between the modes occurring at 0.8 µm. Less than 5 pct of the coal mine diesel aerosol was found in the coarse size fraction. CMB analysis confirms the original premise for using aerosol size to separate diesel exhaust and mineral dust aerosol during sampling.Based on the results from the size selective sampling, a personal diesel aerosol sampler has been developed for measuring diesel aerosol mass concentrations. Th.is sampler uses an inertial impactor to size separate the respirable aerosol at 0.8 µm. All material less than 0.8 µm is collected on an after filter for subsequent gravimetric analysis."

Jan 1, 1990

By R. Hogg

"Agglomeration processes and agglomerate characteristics are largely controlled by the forces of interaction between particles. The nature and typical magnitude of these interaction forces are evaluated relative to the external forces commonly present in agglomeration systems. The specific roles of the interaction forces in the various stages of agglomerate formation and growth and their effects on the integrity and mechanical strength of agglomerates are briefly reviewed. Because the interaction forces affect different aspects of agglomerate development in different ways, conflicting requirements can arise. Examples of such conflicts are given and used to demonstrate the importance of evaluating the effects of interaction forces etc., in the context of the overall agglomeration process and its ultimate objectives.INTRODUCTIONThe term agglomeration is generally used to refer to processes whereby discrete particles are caused, or allowed, to associate into clumps in which the individual particles retain their identity but are held together by relatively weak, usually physical forces. Various other designations are given to these processes, depending on the specific circumstances under which agglomeration occurs. The terms balling and pelletizing are often used to describe agglomeration in dry or semi-dry powders; coagulation and flocculation are used to refer to agglomeration of particles dispersed in fluids. Common to all of these cases is the fact that the formation, growth and integrity of the agglomerates depend primarily on the forces acting on and between particles. The same forces are, of course, responsible for manyaspects of the behavior of colloidal systems and their study and evaluation constitute the,basis for colloid and interface science.FORCES ACTING ON FINE PARTICLES AND AGGLOMERATES It is convenient to classify the forces acting on and between particles into two general types: external forces and interaction forces. It should he recognized, however, that a sharp distinction is not always possible.External Forces Gravity and inertial forces act on all particles and their magnitude is proportional to particle mass, i.e. they vary with the cube of particle size. Such forces are oftensignificant for large agglomerates but may be negligible for individual, fine particles.Hydrodynamic (""drag"") forces are important, for particles suspended in fluids. For very small particles, the drag force is directly proportional to size (Stokes' Law) while for very large particles or agglomerates it varies with approximately the square of size (Newton's Law). A useful procedure for estimating drag forces over a broad range of particle sizes and physical conditions has been given by Concha (1)."

Jan 1, 1989

By W. E. Wallace, V. Robinson, M. F. Keane, V. Vallyathan

"An in vitro study of the biologic responses of surface-modified and native silica and kaolin was made to provide comparative information on the supression of cytotoxicity by pulmonary surfactant. The release of alveolar macrophage cytoplasmic enzyme, lactate dehydrogenase (IDH), and lysosomal enzymes B-N-acetylglocosaminidase (B-NAG) and B-ghucuronidase (B-GLUC) and sheep blood-cell hemolysis were moni¬tored as indicators of cell membrane damage and cytutoxicity. Surface modification of silica and kaolin with dipalmitoyl lecithin (UPI) resulted in complete abrogation of cytotoxicity of both minerals. These findings indicate that surface modification of minerals with different adsorption properties by pulmonary surfactant generally lessens their prompt adverse effects.INTRODUCTIONAcute and chronic silicosis are well-characterized clinical and pathologic entities resulting from the inhalation of crystalline silica (Morgan and Seaton, 1984). Kaolin, a layered aluminosilicate clay frequently mined and used in manufacturing, contains tetrahedral silica alternately layered with alumina octahedra. Kaolin is relatively .inert biologically, and distinctly greater pulmonary burdens are seen in patients with kaolinosis than are seen in patients with silicosis. Crystalline siliea (quartz) induces a significantly greater degree of fibrosis in exposed animals in vivo than does kaolin (Hamilton and Hardy, 1974; Parkes, 1982; Hunter, 1976; Sheers, 1964; Warraki and t-lerant, 1963; Lynch and Mciver, 1954; Lapenas et al., 1984).This difference in pulmonary disease associated with the two types of dust is not reflected by in vitro cytotoxicity as Jetermined by pulmonary macrophage bioassays or erythrocyte hemolysis. Cytotoxicity studies using crystalline silica and kaolin of similar size fractions show comparable bioassay response on a mass basis. These cellular bioassays, therefore, do not correlate with the relative in vivo pathogenicity of silicates."

Jun 1, 1988

By R. L. Schmidt

Research conducted over the past 20 years in France, Great Britain, and the United States on the use of the large-hole burn cut has established cer¬tain advantages for this system. Advantages include longer pull and more complete fragmentation from blast rounds. However, research is needed to establish a set of parameters for optimum performance. As part of the Bureau of Mines Advancing Mining Technology for Marginal Resources program, the Twin Cities Mining Research Center, Twin Cities, Minn., acquired a horizontal rotary drill capable of boring holes up to 24 in. in diameter. This was used for a series of underground experiments at White Pine mine, White Pine, Mich., during 1973. Exceptional results were obtained with a 12-1/4-in void hole that yielded up to 18 ft of pull in a 10- by 20-ft drift, Fragmentation was excellent, and the compactness of the muck pile facilitated loading.

Jan 1, 1975

By O. M. Bishop

The Douglas fluorite property is in the Empire district of eastern Pope County, Ill., which lies near the west boundary of the productive Southern Illinois fluorspar field in Hardin and Pope Countios. Production from mines on the Douglas property accounts for about one-half of the 72,000 tons of fluorspar with which the Empire district is credited. This output was from the Sycamore, Pierce, Slapout, and Empire veins, which are normal fissure veins of little displacement along which there has been local wall-rock replacement by fluorite.

Jan 1, 1949

By R. V. Ramani, S. Shankar

"A convective dispersion model has been utilized to calculate the real-time airborne dust concentration in mine airways using re-entrainment as the only source term for airborne dust. It incorporates two important sources of re-entrainment in mines -- air velocity and movement of objects. The model has a sink term accounting for the deposition of particles along the airway. The model is solved using a finite difference scheme which is coded for computer. The computer model outputs airborne respirable and total dust concentrations along the airway as a function of time. The real-time and average gravimetric concentrations from several in-mine experiments were compared with the results from the simulation of the experimental conditions. This model can be used for estimating airborne dust entrainment due to air velocity, equipment movement, and persons walking. INTRODUCTIONEdwards and Ford (1988) developed a model for coal dust explosion suppression and utilized a predetermined value of threshold velocity for flowing air to pick up dust from floor. Depending on the strength of the removal forces, re-entrainment can increase the airborne dust concentration in mine airways. The most prevalent forces causing re-entrainment in mine airways are the drag and lift forces due to flowing air, and removal forces due to the movement of persons and vehicles. Shankar and Ramani (1991) have investigated the unique characteristics of the re-entrainment phenomenon in mine airways. Experiments on re-entrainment of coal dust particles were conducted in mine airways, and in a wind tunnel (Shankar and Ramani, 1994a, and 1994b). The results from the two experimental studies were found to compare well (Shankar and Ramani, 1995). There is no reported model to determine the airborne dust concentrations due to airflow or persons walking under conditions existing in mines. The present study is a part of a continuing research project in the Generic Mineral Technology Center for Respirable Dust on the spatial and temporal behavior of airborne dust in mine airways (Ramani, 1983)."

Dec 1, 1996