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By Liming Yuan

Three-dimensional computational fluid dynamics (CFD) modeling is conducted to simulate spontaneous heating in a large-scale coal chamber with a forced ventilation system. Spontaneous heating is modeled as the low-temperature oxidation of coal using kinetic data obtained from previous laboratory-scale spontaneous heating studies. Heat generated from coal oxidation is dissipated by convection and conduction, while oxygen and oxidation products are transported by convection and diffusion. The water vapor transfer and the effect of heat of wetting are not modeled. The CFD model is validated by comparing simulation results with test results from U.S. Bureau of Mines experiments conducted in the coal chamber. The model predicts lower temperatures in the early stage but agrees well on the induction time for spontaneous heating. The effects of airflow rate and order of reaction on the spontaneous heating process are also examined. The calibrated CFD model is found to be useful for predicting the induction time for spontaneous heating in underground coal mines.

Jan 1, 2009

By S. H. Katz, J. J. Bloomfield

Fires in zinc dust have sometimes given particular trouble owing to their resistance to extinguishers and the liability of explosions . Similar problems , notably with aluminum dust* , have previously been subjects of investigation by the Bureau of Mines .

Mar 1, 1922

By D. Harrington

Research in connection with occupational diseases, including silicosis or, more definitely, pneumoconiosis, has been prosecuted much more actively in North American countries during the past 5 or 10 years than in any other known period. This applies particularly to the United States, owing largely to the fact that in recent years compensation for ill health presumed to be caused by industrial work of certain kinds is being paid to a far greater extent in this country than previously. Most other countries have had occupational-disease laws for many years. Court rulings in the United States, which started 5 or 6 years ago, have given a few heavy verdicts in connection with ill health or death caused, or alleged to have been caused, by some phase of occupational work other than traumatic injury, and these have called attention to the fact that ill health and even incapacitation can be caused by some kinds of employment. With the onset of the world-wide financial depression, which resulted in permanent abandonment of many business or industrial enterprises (among them mines) in the United States, the workers frequently believed that they could expect nothing in the future from their former employers, hence they felt free to demand monetary benefits or damages because of ill health which they suffered, or thought they suffered, because of their previous employment. The result was a flood of lawsuits and. compensation claims for occupational disease, particularly where dust was involved.

Jan 1, 1938

By Thomas Varley

"Concentration, ore-dressing, or the dressing of minerals are common terms used in metallurgy and indicate processes of separating valuable minerals from worthless gangue. It is understood, of course, that the products from such processes, being separated from the various minerals and gangue, are ready for commercial sale or for further treatment by smelters and refineries.Gravity concentration takes advantage of the difference in specific gravity of the various constituent minerals and gangue of waste material in the ore. The two most common forms of concentration by this means are jigging and table concentration. Jigs usually are used in the separation of relatively coarse material and the tables for the finer material, the line of division in general being about 20 mesh.There are mar factors to be considered .before a decision can be made as to what method would be best adapted to the successful treatment of an ore and only by careful experiments can this be determined. Among the important factors to be considered are. The nature of the minerals present, their physical and chemical relations to the gangue material, and the gangue material itself. Perhaps the most important is the number of minerals present and their relation to each other.Metals exist in ores in three principal forms -- sulphides, oxides or carbonates, and native. Concentration by gravity methods is in general best suited to sulphide ores, although in some places considerable success has, been obtained in the concentration of oxide ores by gravity methods."

Apr 1, 1920

By D. G. Kuehn

Studies were conducted by the Bureau of Mines to determine the positive ions and neutral species produced in glow discharges of gas streams containing 1.0 percent NO in helium, 29 percent dry air in helium, and 1.06 percent NO in N2, Mass spectrographic measurements were conducted for gas pressures from 2.3 to 10.0 torr and dc currents from 10 to 20 mAo Ion species observed included NO+, N2 +, O2 +, N+, and 0+ with lesser amounts of He+, He2+, and N02+. Variations in various ionic and neutral species with discharge duration were interpreted to be consistent with an electrically induced dissociation of NO to produce N2 and O2. No nitrogen oxides were observed to form in glow discharges of the helium-air mixture.

Jan 1, 1975

By W. W. Weller

Heat-capacity measurements of sodium dimolybdate (Na2Mo207) and sodium ditungstate (Na2W207) were conducted over the temperature range from 51° to 298° K. The entropies of the two compounds at 298.15° K were calculated from the heat-capacity values and were used, in conjunction with other entropy data, to evaluate the entropies of formation of the compounds from their constituent elements and oxides.

Jan 1, 1963

By Robert E. Dye

This paper describing the mining methods employed and setting forth prevailing, costs at the property, is one of a series being prepared by the United States Bureau of Mines dealing with properties in various mining districts of the United States and Canada. The Vipond mine is a gold property located at Timmins, Ontario, Canada, and operated by the Vipond Consolidated Mines (Ltd.). For the past fiscal year (ended July 31. 1930) ore was mined and milled at the rate of 310 tons per day, and the value of the bullion produced was $896,397.61.

Jan 1, 1931

By R. V. Ramani, K. Bode

"IntroductionIn part 1 of this paper, the results of the experimental work in a wind tunnel under controlled conditions were presented. To understand the spatial and temporal behaviour of airborne dust under mine conditions, experiments were performed in the Lake Lynn Experimental Mine of the US Bureau of Mines. The mine airway experiments were designed to study the variations of ambient concentrations along the length of an airway, and the deposition rates and deposition velocities in an airway cross section. Other objectives of the study were to investigate the spatial and temporal behaviour of airborne dust with regard to air velocity and particle density, the size distribution of the airborne dust cloud as it travels in the airway, and the size distribution of the dust particles deposited along the airway. Other objectives of the study were to compare wind tunnel results with In-Mine results, whenever appropriate.Experimental ProcedureLocationA complete description of the Lake Lynn Laboratory Mine of the US Bureau of Mines (USBM) can be found in the US Bureau of Mines Information Circular 8911 (Mattes et al., 1983). This mine provides excellent facilities for dust experiments. The airway dimensions are similar to those of a coal mine airway. The mine has a drift (D Drift, see Figure 1) that extends almost 500 meters without interconnecting airways, stoppings, or bends. The D drift measures approximately 6m in width and 2,25m in height.The Lake Lynn Laboratory Mine· is ventilated by a variable speed, 75 kW (100 hp), 28,3 m3/s (60 000 cfm) blower fan installed on the top of the ventilation shaft. Air velocities of 1, 1,3 and 1,8 m/s, respectively, could be obtained in the D Drift. However, the temperature changes at the surface can cause small variations in air quantities and velocities underground. The low background dust level in the mine reduces the problem of sample contamination from other sources of dust. Extended periods of uninterrupted data collection can also be scheduled. Mine airway parameters which are important for the analysis include the dimensions of the airway and the ventilation data such as the air velocity, and the pressure loss in the drift. All these data were acquired during altimeter surveys which were conducted prior to each of the experiments."

Dec 1, 1995

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

The title of this book, The Phoenix of Natural Disasters: Community Resilience is aptly chosen. ?The Phoenix is a mythical bird that never dies; the phoenix flies far ahead to the front, always scanning the landscape and distant space. It represents our capacity for vision, for collecting sensory information about our environment and the events unfolding within it.? (source: The Feng Shui Handbook, feng shui Master Lam Kam Chuen.) There are Chinese, Japanese, Russian, Egyptian, and Native American counterparts of the phoenix. All of these birds are identified with the sun and depicted as rising from the ashes ? living again. This is the essence of a community after a natural disaster ? they live again. The Phoenix of Natural Disasters: Community Resilience is edited by Kathryn Gow and Douglas Paton who have done an excellent job of creating a relatively seamless transition between chapters with different authors. The content is organized well with the first chapter providing an excellent overview of what is to come and each chapter including an abstract clarifying the focus of the chapter.

Jan 1, 2009

By Thomas M. Barczak, Ron Smith

Steel liner plates, which are bolted together to form a shell, are commonly used to provide temporary protective linings in the tunneling industry to ensure the stability of the tunnel and safety of the workers until more permanent ground reinforcement can be installed. As the ground deforms to try and close the opening, the liner plate is radially stressed, and by deforming redistributes these loads back to the surrounding insitu earth. Grouting behind the plates is done to fill any voids and ensure uniform contact to the strata around the back of the plates. Another function of the liner plate in some applications is to act as a platform or structure for the mining machine to react against in order to develop the necessary forward thrust to be able to excavate the face. In this case, the liner plates are loaded axially as a horizontal column of bolted liner plate rings, creating a jacking force against the liner plate assembly. In general, the buckling strength of the plate sections determines the jacking force capacity. Historically, the jacking force capacity of tunnel liner plates has been theoretically determined by some simplistic equations developed from tests of single liner plates. Recently, full-scale tests on a complete circular section of bolted liner plate ring segments have been conducted in the NIOSH Safety Structures Testing Laboratory using the unique Mine Roof Simulator to apply controlled loading in a manner that simulates the real world environment. Due to the unique size and capacity of the Mine Roof Simulator, these are believed to be the first full-scale tests conducted on the jacking force capability of tunnel liner plate rings. These tests indicate that the previously used theoretical equations tend to over predict the jacking force capacity of these tunnel liner plates. Unanticipated deformations in the field have been observed at loads below these theoretical design loads, therefore, a more accurate determination of the jacking force capability was needed. This report summarizes the full-scale test results, examines design parameters that impact the jacking force capability, and develops new mathematical models to improve the prediction of design loads.

By D. Harrington, M. W. Von Bernewitz

Sections 120 and 121 of Article XI. Fire Control, of a proposed Mine Safety Law in preparation, to be used as desired and when approved by any State, contains these provisions: After the adoption of these regulations, no mine operator shall erect any nonfireproof structure within 50 feet of any mine entrance. or airway. Every operating mine having nonfireproof structures within 50 feet of any mine entrance or airway, except headframes necessary for hoisting, shall have such structures fireproofed or removed and replaced with fireproof structures within six months of the adoption of these regulations. Before reopening, mines idle at the time of the adoption of these regulations shall have all non- fireproof structures fireproofed, removed, or replaced with fire- proof structures as required by the foregoing sentence. Upon receipt of the written statement of a mine operator that the fireproofing of existing structures is impracticable, the chief mining engineer (of the State commission) shall satisfy himself as to the abouracy of the statement. If he concurs that fireproofing is impracticable, and if at the same time he holds the opinion that adequate protection can be provided otherwise by such procedure, he shall have authority to issue a written permit for the substitution of fireproof door at or near portals of mine openings and collars: of shafts. Such doors shall fit as nearly gas-tight as possible. and shall be installed in such a way that the mouths of mine open- ings can be closed readily from outside of structures. The effec- tiveness of such permit may be made contingent upon the operator's continued compliance with any additional precautions which are necessary in the chief mining engineer's opinion to protect the lives of miners.

Mar 1, 1932

By Thomas P. Meloy

"The presence of respirable quartz-bearing mineral par-ticles has been well documented in many coal mines, and the Mine Safety and Health Administration regulations address the quartz content of mine dusts. Unfortunately, the correlation between the quantity of respirable quartz-bearing mineral particles and the pathogenicity of the dust is not strong. Work is currently underway by the National Institute for Occupational Safety and Health/U.S. Bureau of Mines and work is being included in the Respirable Dust Center Program by Dr. Seehra to determine the surface availability of quartz in mixed composition mine dusts. However, this paper propose a possible source of surface quartz or a spe¬cial region in the coal that may contribute to the pathogenicity of selected particles in the respirable dust.Assumed in this model is the hypothesis that either the cleat surface is coated with quartz or some cytotoxic sub-stance that in the body is capable of destroying macrophage and thus inducing a fibrotic response (1) that during the frag¬mentation a reasonable proportion of the respirable size coal particles contain some of the original cleat surface and that these particles have the same order of in vivo cytotoxicity as do the quartz particles. It may be that these cleat surfaced respirable size particles are only contributory to the overall pathogenicity of the coal dust, nevertheless, there are enough of these particles to to considered as a potential source of the cytotoxic dust particles.This paper demonstrates that if the cleat surfaces are mineralized with quartz or have a pathogenic coating, then in many mines there will be enough respirable coal dust particles containing some cleat surface to cause a fibrotic reaction. To understand why some of the dust particles contain as part of their surface some of the cleat surface, consider what happens when a beer bottle is broken. While there are a large number of beer bottle fragments, many of the fragments, particularly the larger fragment sizes, will have as a fraction of their surface part of the original beer bottle surface. The model and mathematics of this problem have been worked out by Meloy.(2-4)In the homogeneous IAC model, (2-5) a fragment or par-ticle resulting from comminution is equally likely to occur anywhere in the material being broken. Therefore the probability of a particle of size x having part of the cleat surface in it, p(x), is proportional to x. Thus:"

Mar 1, 1989

By S. P. Kinney, A. C. Fieldner, S. H. Katz

"The regrettable death of James S. Cunningham, Foreman Miner, attached to Bureau of Mines Rescue Car No. 2, while wearing a half-hour type oxygen breathing apparatus in a gasoline storage tank at Trinidad, Colorado, raised the question as to the possibility of gasoline vapors permeating the rubberized fabric of the breathing bags of such apparatus.It is known that most gases and especially certain organic vapors permeate rubber, by solution or a similar process. The rubber becomes saturated with the gas and if a concentration of gas is maintained on one side of the rubber sheet it slowly gives off gas from the other side. It of course takes some time for the gas to diffuse through the rubber and the length of time before it reaches the other side is proportional to the thickness of the rubber. The amount of gas that passes through per unit of area in unit time increases with the concentration of gas and also varies with the structure and composition of the rubber.It has been suggested that the gasoline vapor could not have penetrated into the interior of an oxygen breathing bag because the pressure is greater on the inside, but this is not true as the process of permeation by solution in the rub¬ber is affected only by the difference in the partial pressures of gasoline vapor on the inside and outside of the bag. The positive oxygen pressure on the inside can only prevent the entrance of gasoline vapor through measurable holes, and has no effect on permeation by diffusion through the rubber.A sample of gasoline was obtained from the tank in which Cunningham met his death. Examination by Dr. E. W. Dean of the Petroleum Division of the Bureau of Mines gave the following results.This shows the gasoline to be heavy and typical of the gasolines sold throughout Colorado for motor fuel A. Salvus half hour oxygen apparatus was arranged with the breathing bag only in a gas tight box in which the space was kept saturated with the vapor of this gasoline. The main part of the apparatus was outside the box. Oxygen from the apparatus was breathed by a man in the usual manner. Gas samples were taken from the box at intervals to determine the concentration of gasoline vapor, also samples of the oxygen breathed were taken from a side tube in the mouthpiece. The room temperature was 75°F. The concentration of gasoline vapor in the box at the beginning of the test was 4.3%. The man breathing from the apparatus thought he detected gasoline in his oxygen in two minutes after starting the test. Analysis of the inspired oxygen at this time showed 0.03% gasoline vapor. The same man remained on the apparatus for 18 1/2 minutes without suffering any ill effects. His place vas then taken by another man who wore the apparatus until the oxygen was exhausted without noticing more than a trace of gasoline at any time. At the end of the test the inspired oxygen contained 0.07% gasoline vapor. The total time of test was 38 minutes."

Dec 1, 1919

Wires leading to or from underground facilities can develop hazardous voltages because of lightning exposure. The locations of many mine portals are particularly susceptible to lightning effects. The application of protective devices to limit this potential danger is necessary.

Jan 1, 1975

By F. W. Lee

Operating engineers and mining executives are interested in the science of applied geophysics, but are looking for a simple and understandable exposition of its problems, instead of dissertations which are becoming more and more involved and increasingly difficult to comprehend. It may be well to discuss the goal, the attempted methods of reaching it and the psychological motive, if any, tack of the science. Where does the subject of applied geophysics stand from the viewpoint of (1) the physicist, (2) the mathematician, and (3) the geologist? Fundamentally, the science aims at a differentiation of subterranean geology with the object of finding useful mineral products by the study of gravitational, magnetic, seismic, electric, and other fields which may be associated with the materials naturally or which may be applied to them. The more skillfully these fields are recognized, applied, and analyzed the greater will be the possibility of interpreting results in a way that will be remunerative both economically and scientifically.

Oct 1, 1931

Provide an environmentally compatible means of producing lead from galena concentrates that replaces the current high-temperature pyrometallurgical primary lead smelting process and supplies pure lead metal within present and proposed Environmental Protection Agency (FPA) and Occupational Safety and Health Administration (OSHA) lead emission standards. Approach The U.S. Bureau of Mines developed an energy efficient and pollution-free leach-electrowinning method for use in recovering pure lead metal and byproducts from lead sulfide concentrates.

Jan 1, 1989

Provide an effective method for "soft" soldering aluminum and aluminum alloys using conventional tin-lead solder alloys and flukes. The Problem In the past, it was virtually impossible to solder aluminum and aluminum alloys using standard tin-lead soldering systems (solder and flux) due to the presence of an aluminum oxide surface film which forms instantly on aluminum and aluminum alloys when these are exposed to air. The tenacious and stable oxide film enables aluminum-base materials to maintain their bright luster. But the film also prevents the required wetting and spreading of solder on the substrate, causing the loss of adhesion between the solder and the substrate. In addition, the heat produced during soldering increases

Jan 1, 1983

Develop a curved ray geotomographic program with constraints to counteract non-uniqueness in order to improve the reliability of seismic tomographic imaging of geological structure in mining regions. Background Seismic tomography provides a two-dimensional image (tomographic reconstruction) of the distribution of the seismic velocity in geologic structures using measured travel times of seismic waves crossing the area. It can provide a more complete representation of features be¬tween boreholes than other crosshole processing methods that measure only average properties or borehole logging methods that measure properties only near each borehole. Seismic tomography has many mining applications. They include locating geologic structures of contrasting seismic velocity, detecting fractured regions where the seismic velocity is low, and monitoring solution injected above the water table where the increase in saturation increases the seismic velocity. Thus, tomographic imaging techniques show great promise for detecting and locating geologic hazards that affect the productivity, safety, and environment of mining operations.

Jan 1, 1992

Provide an economic alternative to drill-blast excavation with the same ability to excavate openings of varied orientation, shape, and size. Approach Develop an efficient, adaptable, mechanical excavation machine that produces unconfined tensile failure in rock. How It Works A drill-split fragmentation machine that combines a drill and a unique splitter has been developed. The drill and splitter are mounted on a carriage that positions the splitter in a hole immediately after it is made by the drill. The splitter creates force loads that cause the rock to fragment, and the process is repeated for excavation. The unique splitter applies both radial and axial loads to the rock mass, which produces an excavation action comparable to pulling a plug. This excavation action distinguishes the radial-axial splitter from typical demolition splitters, which require a free surface parallel to the axis of the splitter toward which to break rock.

Jan 1, 1989