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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 Jr. Hardy, H. Warren Shen

"A study is presently underway by the authors to investigate the character of the bit-coal interaction during coal cutting and its influence on the size and shape distributions of the generated dust. An important aspect of this on-going project is the development of acoustic emission (AE) criteria which would make it possible to carry out remote monitoring of coal cutting operations. The on-going AE studies are fundamental in form and were undertaken to evaluate the general feasibility of AE monitoring techniques using simplified coal breakage and cutting procedures. The present paper will focus on the test facilities, experimental techniques, and results associated with linear, single-bit cutting. An AE-transducer, attached directly to the bit, detected AE signals during the cutting process.Experiments have been carried out on seven specimens of coal obtained from the USBM experimental mine at Bruceton, Pennsylvania. Three separate cuts were made for each of two bit angles (10 and 45 degrees) and two bit velocities (0.085 and 0.169 cm/sec), for a total of 12 separate cuts. Data associated with resulting particle size distribution and AE characteristics (major dominant frequency components) will be discussed. Data analysis has also been underway using a computer-based pattern recognition system known as ICEPAK (Intelligent Classifier Engineering Package). This program is able to evaluate over 100 features of an AE event and to make objective comparisons between AE signals associated with different loading or cutting parameters. The results to date show that AE generated during some of the test conditions can be recognized by ICEPAK with a recognition rate of 90% and higher while other conditions cannot at present be separated with a suitable recognition rate. Further analysis of the experimental data is presently underway.The reduction of the severity, and eventual elimination, of Coal Workers' Pneumoconiosis (CWP) depends on gaining fundamental understanding in a number of major areas. These include dust generation and entrainment, transportation, suppression, medical effects of dust, and possible treatment. At present a project is underway by the authors to investigate the character of the bit-coal interaction during coal cutting and its influence on the size and shape distributions of the generated dust. An important aspect of this on-going project is the development of acoustic emission (AE) criteria which would make it possible to carry out remote monitoring of coal cutting operations. Suitable on-line analysis of monitored AE data would allow engineers to evaluate factors such as shearer bit conditions and cutting efficiency, and to quantify the particle size and shape distribution of the generateddust. The on-going AE studies are fundamental in form and were undertaken to evaluate the general feasibility of AE monitoring techniques using simplified coal cutting procedures. To date experiments have been carried out on coal under uniaxial compression, linear single-bit cutting, and cutting using a laboratory-scale, single-bit shearer. A brief outline of the overall study has been presented in an earlier paper (Hardy, Shen and Kimble, 1995). This paper will consider the linear single-bit cutting studies in more detail.It is generally accepted today that most solids emit low-level seismic signals when they are stressed or deformed. In this paper this phenomenon will be referred to as acoustic emission (Hardy 1972, 1981, 1989). In essence, the measurement of AE activity in a field or laboratory structure is relatively simple. A suitable transducer is attached to the structure, the output of the transducer is connected to an associated monitoring system, and the AE signals occurring in the structure, due to internal or external stress, deformation, and failure are suitably acquired, pre¬processed and recorded."

Jan 1, 1998

Reduce injury to people or damage to equipment when a scheduled production blast is detonated. Approach The essential elements of an effective blast area security system were identified through case studies of five mining operations where the blast area guarding practices were considered to be superior to those generally found in the industry. These elements were used in making recommendations for improved blast area safeguarding practices. Background The blast area security system is a means by which the mine operator prevents injury to people or damage to equipment when blasting is performed. Analysis of blasting accidents showed that most blasting accidents occur during scheduled blasting and are due to inadequate blast-site security. Factors contributing to the system&apos;s breakdown are failure to clear the blast zone, inadequate guarding. and failure of personnel to follow instructions, retreat to a safe location, and/or take adequate cover. Mine personnel, visitors and even trespassers can inadvertently wander into a blasting zone unless proper procedures exist to ensure that all personnel are cleared from the blast zone and kept safely away until after blasting IS completed. Statistics show that the blaster is the miner most frequently injured In these accidents.

Jan 1, 1986

By James C. Barker

Gold placer deposits along the upper Yukon River, in the region between the river villages of Circle and Eagle, were investigated by the Bureau of Mines. The investigation was conducted intermittently between 1976 and 1985 as part of an evaluation of mineral resources on lands proposed for inclusion in the National Park System. At least 230,000 troy ounces (tr oz) of gold has been produced in the region, principally from Woodchopper, Goal, and Fourth of July Greeks. The placers are underlain by, or occur downstream of, early Tertiary sediments that have been deposited in the Eagle Trough. Strike-slip displacement along the Tintina Fault is responsible for creation of the trough and may have been a factor in the formation of the present placers. Placers were found to have a close spatial correlation to certain altered fault lineaments of the Tintina Fault trench. Placer concentrates contain several different textural forms of gold, suggesting multiple origins. Geological studies and a survey of 162 panned concentrates throughout the region indicated previously unreported sites of placer gold, and potential exists for the discovery of additional placer and lode gold. Because of nearly continuous soil and vegetation cover, further evaluation of the region will require subsurface sampling.

Jan 1, 1986

By R. Karl Zipf

In some instances, extensive room-and-pillar working scan collapse with little warning and pose a serious risk to underground miners. Traditional strength-based pillar design methods applicable to coal or hard-rock mines use a factor of safety defined as pillar strength divided by pillar stress. Factor of stability, defined as local mine stiffness divided by post-failure pillar stiffness, may offer a way to design room-and-pillar mines and eliminate collapses. Three alternative design approaches to decreasing the risk of large-scale catastrophic collapses are described: the containment approach, the prevention approach, and the full-extraction approach. Until good data on the post-failure behavior of pillars become available, the containment and full-extraction options are the safest. The limitations in our ability to evaluate both the stability of old workings and the long-term performance of room-and-pillar mines are described.

By Charles L. Kimbell

Following the pattern established in the 1989 edition of this study, the concept of data availability must be addressed, because there are perceptible changes from year to year, and the availability of accurately reported, precisely defined statistics and nonstatistical information provides the only sound basis for analytical studies of any type. As the countries of eastern Europe, including the numerous states that formerly comprised the U.S.S.R., undergo the transition from centrally planned economies&apos; to market economies, there has been a perceptible increase in information availability for rather obvious reasons. Any industrial operation seeing economic assistance from government and/or private sources outside the country in which the facility is sited must provide some appraisal of its operations at the time it seeks assistance, as well as some information on previous performance to serve as tools in evaluating its potential under the proposed development scheme for which it seeks financial assistance. This situation, coupled with governmental recognition that concealment of much of the national mineral production, trade, and consumption data for purposes of national security probably never was really necessary and certainly proved unnecessary with the end of the so-called cold war, has led to the publication of increasing amounts of both statistical and nonstatistical information in the countries undergoing economic transition.

Jan 1, 1993

By M. G. Pelipetz

High-pressure, high-temperature hydrogenation of coal has been known and practiced for many years. A full&apos; understanding of the mechanism in this process by which coal is converted to oil and gas must rest on a critical interpretation of the manner in which external variables influence the rate and the course of the coal-hydrogenation reactions. Same Bureau of Mines studies on the effect of temperature, catalyst, and rank of coal on these reactions have been published. The effect of pressure was not studied in this earlier work, and the effect of reaction time was complicated by the interruption of long reaction periods in order to refill the autoclave with hydrogen. It is the purpose of this paper to present data from more recent autoclave experiments that extend the results of Storch, et al, on the kinetics of coal hydrogenation. These data must be explained by any comprehensive theory of coal hydrogenation; their detailed evaluation, however, will be deferred until a later publication.

Jan 1, 1949

By G. E. McElroy

"while investigating the presence of heavy strata gases* in certain mines of the East Tintic mining district of Utah, a small, local body of light, very hot gas of high-nitrogen composition was noted in one of the mines. Observations and analyses indicate that this light gas was resulting from very rapid oxidation of finely disseminated pyrite, in lead-silver sulphide ore. The gas was actually mine air which had lost a large proportion of its oxygen content by reaction with the pyrite. This body of gas was hanging in a local high spot about 5 by 5 by 5 feet in size, caused by caving, at the end of a crosscut. Fifty feet from this spot, an air current of 6000 cubic feet per minute was entering the 5 by 7 foot cross-cat from a raise from below.On account of the vapor contained in the gas, the bottom level of the gas could be plainly seen and was practically a horizontal plane, but of slightly wavy appearance, coinciding with the point where an acetylene light was extinguished. This body of gas was visited on three occasions and samples obtained by means of evacaated bulbs and by water displacement. The temperature of the gas was ap¬proximately 175 degrees P. on all three occasions, so that sampling required thick gloves and quick action. Air three feet below the vapor line had a temperature of only 120 degrees F., and a relative humidity of 27 per cent. The stratification of the air and gas mixtures was so sharply defined that the sampler could hold his head a few inches below the vapor level for an appreciable period of time without any noticeable effect other than that due to the high temperature. At one foot below vapor level, it was 135 degrees F., and the relative humidity was 30 per cent. When a candle and an acetylene light were raised into the gas from below, the candle flame was extinguished at a point two inches lower than the acetylene flume, indicating a drop in oxygen content from about 16 per cent to 12 per cent (oxygen content of normal dry air 20.05 per cent) in the distance of two inches."

Sep 1, 1921

By Charles L. Kimbell

The concept of data availability must be addressed, because there are perceptible changes from year to year, and the availability of accurately reported, precisely defined statistics and nonstatistical information provides the only sound basis for analytical studies required for government policy planning or industry market analysis. As the countries of Eastern Europe and the former U.S.S.R. undergo the transition from centrally planned economies to market economies, there has been a perceptible increase in information availability for rather obvious reasons. Any industrial operation seeking economic assistance from Government and/or private sources outside the country in which the facility is sited must provide some appraisal of its operations at the time it seeks assistance, as well as some information on previous performance to serve as tools in evaluating its potential under the proposed development scheme for which it seeks financial assistance. Additionally, there was growing governmental recognition that concealment of much of the national mineral production, trade, and consumption data for purposes of national military and/or economic security probably never was very successful, never was really necessary for most commodities, and certainly proved unnecessary with the end of the so-called cold war. Indeed, the long-term unwillingness to publish uniform statistical series of reliable,

Jan 1, 1993

By Richard F. Hewlett

Use of digital computers makes possible a more efficient and complete analysis of data from a mineral deposit . This computer program was written and used during an investigation into the efficiency of methods of computing grade and tonnage of ore , wherein it was necessary to make repeated computations involving different combinations of data . This investigation was part of a continuing program of sampling methods research at the Bureau's Denver Mining Research Center.2-4 This program is designed to compute tonnage and average grade for 40 cutoff grades using either the statistical or polygonal methods . tational rate is from 200 ( input bound ) to 1,400 assays per minute , depending on the use of either individual ( one assay per card ) assay- interval length or

Jan 1, 1963

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

APPENDIX B - DEVELOPMENT OF FOAM-CONCRETE SLURRY MINE SEALANT 1. Introduction This appendix describes the results of an experimental development and laboratory evaluation of foam-concrete as a rapid setting, lightweight, self-supporting mine sealant material. Foam concrete, otherwise known as Aerated Concrete, is a form of lightweight concrete whose structure consists of air bubbles held together by a hardened cement mortar. Its principal applications are found in roofing, insulation, shock absorbing, and backfill. The air bubbles in foam concrete are formed either by chemical reaction in the wet, placed mortar, or by introducing a stable foam into the mortar during mixing. The mortar is usually a cement slurry with fine sand or fly ash as filler. Our attention focused on preformed foam concrete, since this is most adaptable to field applications. Equipment is available,* which simultaneously mixes and pumps a slurry of foam concrete. Such a slurry can be produced at a rate of up to 50 yards/hr and has been pumped in a 2-inch-diameter hose 1000-feet horizontally and 250 feet vertically up without significant bubble deterioration. One very attractive feature associated with the use of foam concrete concerns site logistics. Foam concrete can be generated with densities as low as 20 lbs/ft3, and hence the total number of

Jan 1, 1973

By J. Grumer

Nine dust and gaseous inhibitors of propagating coal dust-air flames (lean, stoichiometric, and rich) were evaluated in a newly developed 15-cm-id, 3.6-meter-long instrumented flame duct, under conditions such that wall quenching was virtually absent and the dust concentration was temporally and spacially uniform to within about t5 percent. Listed roughly in order of increasing efficiency, the inhibitors evaluated were rock dust (calcium carbonate), powdered oyster shells (calcium carbonate), Halon 1301 (trifluorobromomethane), Halon 1211 (difluorochlorobromomethane), sodium chloride, Super-K (potassium chloride), regular-grade fire extinguishant powder (sodium bicarbonate), Purple-K (potassium bicarbonate), and Monnex (potassium bicarbonate combined with urea). Experiments were extended to clouds containing 1 and 2 volume-percent of methane. The inhibition of lean, stoichiometric, and rich methane-air flames without coal dust was also examined in a few instances; results agreed with those obtained for coal dust-air flames.

Jan 1, 1971

By I. AITKENS

The precious stones rubies and sapphires are transparent varieties of the mineral corundum . Essentially they are aluminum oxide , but the aluminum is often replaced. by small amounts of chromium , titanium , or iron . The chromium is said to give a red color , titanium a blue , and iron a yellow . True rubies range from rose to a somewhat purplish red and are sometimes termed " oriental rubies " to distinguish them from spinel rubies , stones of inferior hardness , density , and value . " Oriental rubies " are very rare , and the so-called " pigeon's blood" variety is the most valuable . Sapphires normally range in color from palest blue to deepest indigo , but actually all precious varieties of corundum of any other color than red are called sapphires . The most esteemed tint is like that of the blue cornflower . Colorless corundum of gem quality is called white sapphire ; the yellow variety is described either as yellow or as golden sapphire ; and the pale pink is classed as pink sapphire . The word " oriental " is also used as a prefix in naming varieties of corumdum of less popular colors . For instance , oriental emerald is used for green corundum, oriental topaz for yellow , and oriental amethyst for violet to purple varieties . The chief physical characteristics of rubies and sapphires are hardness , adamantine luster , and moderately high specific gravity ( 3.9 to 4.1) . Next to the diamond, corundum is the hardest of all minerals ; in fact , the sapphire is number 9 on Moh's scale , ranking between the topaz and the diamond. Rubies crystallize in 6-sided prisms terminated by flat faces and other varieties of corundum with twelve inclined faces , six above and six below , meeting in a girdle . Corundum is doubly refractive , with a direction of single refraction running parallel to the edge of the prism . The refractive indexes are very constant, the ordinary index ranging from 1.766 to 1.774 and the extraordinary index from 1.757 to 1.765. The double refraction always remains the same.

Aug 1, 1931

By R. P. Beyer

A FORTW IV computer program has been written to calculate thermodynamic properties over a desired temperature range from spectroscopic data. This program computes heat capacities, enthalpies, and entropies for monatomic, diatomic, linear, and nonlinear polyatomic gases. This research is part of the Bureau of Mines effort to provide thermodynamic data for the advancement of mineral technology.

Jan 1, 1981

By William P. Diamond

A 3-inch pilot hole was directionally drilled to intercept the Freeport coalbed horizon horizontally at Mather, Pa., as part of a Bureau of Mines degasification project. The original concept was to continue the horizontal drilling into the coalbed, after the initial intercept, with a total of three horizontal holes eventually being completed. However, the erratic thickness (0.0 to 4.3 feet) of the Freeport coalbed at Mather was not sufficient to support the horizontal drilling degasification technique, and the site was abandoned after six attempts to locate adequate continuous coal thicknesses. The drilling of coreholes in the immediate vicinity of proposed well paths to evaluate coal thickness is essential prior to future slant hole operations. Although mechanical failures of the new directional drilling equipment, mud pump and rig breakdowns, directional control problems, and exploratory horizontal drilling in the Freeport horizon more than doubled the anticipated cost of the pilot hole, continuing improvements in directional drilling equipment and techniques should significantly reduce the time and costs of future drilling operations.

Jan 1, 1977

By Irving Hartmann, Bernard Lewis, John Nagy, H. P. Greenwald, H. C. Howarth

"ORIGIN OF INVESTIGATIONThe Federal Mine Safety Code for Bituminous Coal and Lignite Mines of the United States, July 24J 1946, contains the following provisions with regard to rock dusting: Article VI. - Section 2. Rock dusting.(a) All mines, except those mines or those locations in a mine which are too wet or too high in incombustible content to propagate an explosion, shall be rock-dusted to within 80 feet of the faces of rooms and entries; however, if the mine or any part of it is wet but becomes dry, the mine or portion of the mine so affected shall be rock-dusted as ·soon as it becomes dry. (b) In mines partially rock-dusted or in mines that are required to start rock dusting, haulageways and parallel entries connected thereto by open crosscuts shall be rock-dusted. Back entries shall be rock-dusted for at least 1,000 feet outby the junction with the first active entry. Inby this junction, the rooms, entries, and crosscuts shall be rock-dusted by generalized rock dusting as provided for in section 2(a).(c) Where rock dust is applied, it shall be distributed upon the top, floor, and sides of all open places and maintained in such quantity that the incombustible content of the mine dust will not be less than 65 percent. In trackless entries and air courses, protection in lieu of generalized rock dusting may be had by using bags filled with rock dust, if they are placed at regular intervals and staggered as described in Bureau of Mines Report of Investigations 3411."

Feb 1, 1948

By Daniel W. H. Su, Gregory J. Hasenfus

This paper demonstrates that finite-element modeling can be used to predict in situ coal pillar strength, especially under non ideal conditions where interface friction and roof and floor deformation are the primary controlling factors. Despite their differences in approach, empirical, analytical, and numerical pillar design methods have apparently converged on fundamentally similar concepts of coal pillar mechanics. The finite-element model results, however, are not intended to suggest a new pillar design criterion. Rather, they illustrate the site-specific and complex nature of coal pillar design and the value of using modeling procedures to account for such complex site-specific conditions. Because of the site-specific nature of coal pillar design, no single pillar design formula or model can apply in all instances. Understanding and accounting for the site-specific parameters are very important for successful coal pillar design. More work remains before the century-old problems related to pillar design are finally solved. Future research should focus on the cross-linkage of empirical, analytical, and numerical pillar design methods.

Jan 5, 1999

By Martin S. Oudenhoven

This Bureau of Mines report presents the results of a microseismic study conducted in the Climax block cave mine at Climax, Colo. Rock noises created by caving were monitored and their sources located during a 3-month period. A planar array of seven accelerometers, located above the block of ore being caved, detected the rock noise. A computer was used to calculate the location of the microseismic activity, using a traveltime difference method. The accuracy of these locations was estimated to be ±20 feet. An analysis of the data taken during the recording period showed a concentration of microseismic events located in the wall of the cave panel. This concentration of events was found to occur in a "high-silica" geologic forma-tion that cut across the caving panel approximately 200 feet behind the undercut.

Jan 1, 1973

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

By Richard V. Ageton

Compressed- air blowers are frequently used both in large and small metal ines , not only as an aid to ventilation , but in some mines as a substitute for an dequate ventilation system . As a temporary fixture , blowers have their uses , but hey should never be used in lieu of a permanent ventilation system. A number Probably the most common error made in placing dependence on compressed- air lowers as an aid to underground ventilation is the tendency to over- rate their cooling efficiency . It is a very common but natural error to assume that compressed air which issues freely from a blower is of the same temperature as the compressed air which issues freely from the exhaust port of a rock-drilling machine . of readings were taken in different mines of the temperature of the rock- drill exhaust , of the compressed air flowing from the blowers , and of the surrounding air In both cases . In general , the temperature of the rock- drill exhaust was from 10 to 30 degrees below that of the surrounding air , in many instances being slightly below freezing , 32° F . The average temperature for a number of compressed-air lowers and for the mine air surrounding them is shown in Table I.

Jan 1, 1922