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By J. H. Stears

This Bureau of Mines report presents information on the use of steel supports in U.S. coal mines, including accident statistics for a 3-yr period and a survey of present applications and problems. It also contains a summary of available steel arch configurations and a description of steel support design criteria for ground control applications.

Jan 1, 1984

By P. L. Loyselle, B. D. Comilsen, D. H. Carlson, J. H. Johnson

"In-mine airborne particulate samples have been successfully collected and the relative amounts of diesel and coal determined using the Laser Raman Quantitative Analysis (LRQA) method. This method allows analysis of filters which have been collected by a method similar to that used to determine the airborne respirable dust concentration in us underground coal mines. Samples were taken near the feeder-breaker, on haulage vehicles, and in the returns. Sampling methodologies were developed for coal-only and diesel-only particulate reference samples with sufficient filter loading for the LRQA method. A statistical analysis of reproducibility has been carried out. Samples have been collected simultaneously at two locations using the LRQA and the size-selective sampling methods. Good agreement between the two methods has been found.INTRODUCTIONThe goal of this research has been to develop the Laser Raman Quantitative Analysis (LRQA) method to measure the composition of respirable particulate, i.e. the fractions of coal and of diesel particulate, in the mine ambient air. In earlier Bureau of Mines sponsored research, we successfully demonstrated that the LRQA method could be used to measure the fraction of Diesel Particulate Matter (DPM) in coal/diesel particulate mixtures which were prepared in the laboratory.(I) 'The immediate objective was to test and refine this LRQA method on samples collected in a diesel underground coal mine.Specific objectives required to meet this goal include:I) Develop in-mine sample collection methods which will insure sufficient particulate loading on filters for LRQA. ,2) Develop methodology for in-mine collection of reference samples (""coal-only"" and ""diesel-only"" filters) which arc required for quantitative LRQA. 3) Analyze precision and accuracy of the LRQA method. 4) Compare composition measurements with another analytical method, i.e. the University of Minnesota/Bureau of Mines size selective sampling Micro-Orifice Uniform Deposit Impactor (MOUDI) method.An advantage of the LRQA method is that it allows analysis of filters which have been collected by a method similar to that used to determine the respirable dust concentration in US underground coal mines. No new sampling instruments and techniques are required. Transfer of sample from collection substrate to analysis substrate is not necessary. Furthermore, other analyses can be made on the same sample since the technique is nondestructive."

Jan 1, 1988

By T. M. Barczak

This report describes Bureau of Mines research to develop methods to evaluate loading on longwall roof supports to permit better design and more efficient utilization of these structures in compliance with the geological conditions in which they are employed. The resultant vertical and horizontal force acting on the canopy of a shield can be determined, either from a statically determinate solution assuming rigid-body mechanics and elimination of certain unknowns, or from an elastic solu-tion by analysis of the load-displacement relationship of the shield structure. A two-dimensional rigid-body model is presented that determines resultant shield forces by measurement of leg, canopy capsule, and lemniscate link forces. An elastic solution is presented, in the form of an elastic stiffness model with two degrees of freedom, which describes the load-displacement relationship from the stiffness of the shield structure as determined in the Bureau's Mine Roof Simulator (MRS). The ability of both models to determine resultant forces acting on the shield canopy are evaluated from full-scale tests in the MRS. More advanced numerical models are also discussed as part of the Bureau's continuing effort in the evaluation of roof support structures.

Jan 1, 1987

By K. R. Becker

The addition of a force gage and a reaction detector to the Bureau of Mines drop-weight impact apparatus made it possible to examine the details of the force exerted on the specimen and make estimates of the time to reaction. With the current setup the force was found to be oscillatory and not reproducble. However, single well-defined pressure pulses can be delivered to the explosive sample by modifying the drop-weight tools. With a modified test arrangement, the time to reaction and the peak force and energy at the time of reaction were determined as a function of drop-weight height for several different explosives. All these parameters were found to decrease as the rate of force application was increased. The same parameters were also found to vary with the thickness of the test sample. The implications of these results are discussed in terms of practical drop-weight testing.

Jan 1, 1972

Although the technology involved in removing material from below the earth's surface has a long history, communication systems in underground workings are relatively new to the industry. Communication equipment did not begin appearing in underground mines until the early 1900's. Figure 1-1 shows a miner using a Western Electric standard telephone set for underground mines in 1913. These early phones were essentially the same as those used aboveground, except that they were enclosed in cast-iron boxes as protection against moisture, acid fumes, and gases. In the 1950's, the Chesapeake and Potomac Telephone Co. of West Virginia introduced a telephone set for use in explosive atmospheres that was designed around the philosophy of explosion containment. To contain an explosion within the telephone set required a 39-pound casing, which greatly limited portability. [ ] Both of these telephone sets required "pipe" or conduit, not a very practical item for a 100-squaremile coal mine. A common thread prevalent in the first 40 years of design and development is that the primary effort was placed on the telephone set. In the early 19701s, as work began on the design of modern communication systems for use in underground mine environments, the following requirements were established: 1. Must meet intrinsic safety standards .--This applies not only to coal mines, but to other explosive environments. 2. Must be compatible with the environment.--The system must with- stand dust, moisture, and corrosive conditions. 3. Must be rugged in structure.-- The system must withstand maintenance by 10-inch pliers and 4-pound hammers, as well as impact from a falling piece of roof. 4. Must be size-flexible.--Whatever is built must be sized for the small operator as well as the large companies. 5. Must be a total system in design.--The system must be intrinsically safe, including cable, power supply, and station set. 6. Must work with present telephone system.--The system should be compatible with aboveground communications already in place; it should not be the single cause of change in aboveground communications. 7. Value-added pricing.--The system should be reasonably priced so that savings created by its introduction will more than offset the installation cost.

Jan 1, 1984

By John N. Murphy

INTRODUCTION It's a pleasure to be with you and to share in this opening session for the 27th Annual Institute on Mining Health, Safety, and Research. As we come together today, I would like to reflect for just a moment on the past Institutes. Much of the progress in Mine Health and Safety has been the subject of presentations and discussions at the previous Institutes, either by identifying the issues, proposing techniques to overcome the problems, or presenting new findings to address important issues for the mining industry. May I extend our thanks and congratulations to VPI and to the planners and organizers of all of these Institutes for their important contributions to our mutual goals of improving mine health and safety. In the time available today, I would like to accomplish two objectives: 1. Provide my assessment of the current status of the Mining Health and Safety Research Program; and 2. Share with you the continuing need and direction for the Mining Health and Safety Research. MINE HEALTH AND SAFETY RESEARCH TODAY Mine Health and Safety Research was conducted formerly at four geographical locations within the USBM, specifically: Pittsburgh, Spokane, Twin Cities, and Denver. Although the Twin Cities and Denver Centers were closed, we have been successful in relocatingfmaintaining much of the core competencies to conduct a responsive, multidisciplinary Mine Health and Safety Research Program. The current staff at Pittsburgh and Spokane directed toward Health and Safety Research totals 397. This includes Lake Lynn Laboratory, about 60 miles southeast of Pittsburgh, where large-scale mine fire and explosion research is conducted. With the closures and transition we have worked to maintain the core competencies necessary to address Health and Safety issues. In some cases we have made arrangements to provide the requisite core competencies through external organizations. An example is the reassignment of the diesel particulate instrumentation capability from Twin Cities to Pittsburgh. In the case of diesel emission control, due to the cost of relocating laboratories and the lack of the appropriate skills at Pittsburgh or Spokane, the emission control laboratory is now being operated in Minneapolis through a contractual arrangement with the University of Minnesota.

By Thomas P. Mucho, William D. Monaghan, John Wood, Michael A. Trevits

We have tested the ability of ground penetrating radar (GPR) to resolve adjacent mine workings. The work was conducted at two National Institute for Occupational Safety and Health locations – an underground coal mine and an underground limestone mine. The objective of our work was to determine if GPR signals could be received from distant mine workings. The GPR system was calibrated on underground mine pillars of known dimensions using a variety of antennas. The system was then tested at several underground locations in an effort to detect an adjacent drift entry; and an adjacent abandoned coal mine. As a means of verification, an in-seam horizontal hole was drilled from the active coal mine to the abandoned mine to confirm the presence and location of the abandoned mine workings. Our results show that in the case of the limestone mine the maximum depth of penetration where the mine workings could be resolved was 85 ft; and in the case of the coal mine the abandoned mine workings could be resolved at a depth of 205 ft. We conclude that it may be possible to utilize GPR for initial underground mine studies followed by directional drilling to accurately delineate the extent and position of adjacent abandoned mine workings.

By Seth C. Schaefer

The Bureau of Mines studied the standard free energies2 of formation of ferrous fluoride (FeF2) and ferric fluoride (FeF3) with high-temperature galvanic cells employing calcium fluoride doped with 1 mole-pet yttrium fluoride as the electrolyte. A free-energy change for the cell reaction Fe (s) + NiF2 (S) = FeF2 (S) + Ni (s) together with the standard free energy of formation of nickel fluoride yields a standard free energy of formation of ferrous fluoride from the elements of ?GF° = -168.74 + 30.63 x 10-3T ± 0.41 kcal/mole (897-1,098 K). (2) Combining the standard free energies of formation of magnesium fluoride, ferric oxide, and magnesium oxide with the free-energy change for the overall cell reaction 3MgO(s) + 2FeF3 (s) = 3MgF2 (S) + Fe2 03 (S) (3) gives a standard free energy of formation of ferric fluoride from the elements as ?Gf° = -281.45 + 90.46 X 10-3T ± 0,67 kcal/mole (880-935 K). (4) Free energies and equilibrium fluorine pressures for the two univariant equilibria of the Fe-F system are tabulated and illustrated.

Jan 1, 1975

By Irving Hartmann

Modern mechanized mining with high-speed machines, multiple-entry systems, multiple blasting, high-velocity air currents, and rapid haulage has brought many economic benefits and has on the whole enhanced safety in the coal-mining industry. It has, however, also introduced some added hazards, the control of which requires concerted effort and ingenuity. Mechanized mining has greatly increased the production and dissemination of fine coal seam or in mine entries. Use of high-speed machines has increased the probability of formation of incendive sparks, which are produced by frictional contact between moving metals and certain mineral substances in the coal seam or in the adjoining rock strata. In gassy seams rapid extraction of coal has increased the rate of gas evolution. These facts have made more urgent the need of preventing the ignition of coal dust and the development of widespread mine explosions. The ignition hazard can be controlled best by eliminating all potential igniting sources and by careful attention to ventilation designed to prevent accumulation of gas capable of triggering a coal-dust explosion. Frictional spark ignition by mining machines and suggested safeguards are discussed in a recent publication. Extensive research and long experience have shown conclusively that the propagation of coal-dust flames can be arrested and the development of widespread explosions prevented by properly applied, generalized rock dusting.

Jan 1, 1956

By Martin A. Elliott

"INTRODUCTION During the recent war the Bureau of Mines was requested to obtain in¬formation on the temperature at which ammonium nitrate mixed with certa: contaminants would react rapidly. This information was desired in connection with an investigation of an explosion that had occurred during the evaporation, by air agitation, of volutions containing ammonium nitrate in which compressor oil that might have passed the filters was suspected of being a contaminant.During the course of this work it was found that mixtures of ammonium nitrate and zinc reacted rapidly at comparatively low temperatures: and since zinc could not positively be eliminated as a contaminant in the explosion in question, a series of tests was carried out, not only with mixtures of ammonium nitrate and compressor oil but also ammonium nitrate and zinc with and without oil. A few experiments were made with metals other than zinc.The investigation was not as extensive as might have been desired, owing to limitations -in time. The results are presented at this time in view of their current interest in connection with the Texas City disaster, in which a large quantity of ammonium nitrate detonated in the holds of two ships."

Mar 1, 1948

By C. L. Brown

Among the more recent developments for breaking coal in mines is the Airdox system, in which high-pressure compressed air is conducted to the points of application by means of heavy-duty steel and copper tubing. Stray electric currents can be detected on y of the compressed-air lines, and evidence of such currents is rev led, by arcs and sparks when contact is made between the tubing and mine track or other equipment forming a current path with the track. Explosive gas is liberated in many coal mines; therefore, from the standpoint of safety, it is desirable to eliminate all possible sources of gas ignition, including stray electric currents. The purpose of this report is to reveal the source, magnitude, and possible methods of controlling stray currents in compressed-air lines that are used in connection with Airdox systems. Stray electric currents have been studied in most coal-mining localities in the United. States where Airdox equipment is used. The information given in this report is based on the find of these studies.

Jan 1, 1949

By A. A. Berk

In the course of a study of the formation of external deposits on tubes in water-tube boilers it became desirable to determine the sulfur dioxide (SO2) and sulfur trioxide (SO3) in the Due gases. Determinations made by the A.S.M.E. method for SO2 and SO3 in gaseous products of combustion did not give accurate results. It was found that minute quantities of copper, present in the flue gases from the coal in use, caused oxidation of sulfite in the absorption bottle and that the carbon dioxide (CO2) in the flue gases caused high values for SO2. The A.S.M.E. test procedure was revised to prevent oxidation of sulfite in the absorption bottle and to allow for the effect of CO2; subsequent analyses of flue gases produced reliable results. The revised procedure is described.

Jan 1, 1950

By Charles W. Huggins

The Bureau of Mines investigated palygorskite, a natural asbestiform material, to accumulate knowledge that might serve as a foundation for future synthesis of a similar material. Unit cell, chemical analysis, DTA, TGA, optical constants, and electron microscopy data were obtained. Selected palygorskite samples of bettor than 97-percent purity were used to obtain this information. Chemical analysis revealed the following formula: (OH2)4 (OH)2 Ca0.01Fe0.02K0 .c3Mg2.10A12.00Si7.93020.3.91 H2O. The optical constants for sodium light are a = 1.522; S = 1.530; ?=1.533; biaxially (-). The following orthorhomibic unit cell constants were determined: ao = 12.690 A, Z = 2, bo = 17.857 A, Dx = 2.327. co = 5.207 A, Identical diffraction patterns resulted from the three palygorskite samples that were studied. X-ray, chemical, DTA, TGA, and optical data were compared with literature values for similar fibrous materials. X-ray diffraction lines were indexed. Several electron micrographs were made to compare the structures of palygorskite and attapulgite with that of chrysotile. The micrographs revealed extremely short laths for attapulgite, very long flexible laths for palygorskite, and tubular structure for chrysotile.

Jan 1, 1962

By D. Harrington

In general, mining is carried on underground, that is, in confined places where it is difficult to obtain adequate lighting and frequently in rock strata requiring much care to prevent caving. Moreover, explosives must be used in mining with the numerous hazards associated with them, and some mines give off explosive or irrespirable gases; also, ma- chinery must be used, usually under conditions much more hazardous than on the surface. These and many other considerations cause mining to be probably the most hazardous occupation in which large numbers of our fellow countrymen are employed. Prevention of accidents in the mining industry is far more complicated than in surface industrial work, even of the more hazardous types, because the different elements that enter into possible accident occurrence are ascertained more readily above ground and suitable action can be taken against them; moreover, errors in connection with prevention of accidents in surface industrial work usually affect only one or, possibly, a few persons, while in zines one human error may readily cause an explosion or other untoward occurrence resulting in the death of scores or even hundreds of persons. This difficulty in the prevention of accidents in and around mines is well-known, and most countries and States have regulations to guard the safety and, to a much smaller extent, the health of workers in mining and allied industries. In general, the State laws and regu- lations regarding the welfare of mine workers are merely a skeletonized outline of some more or less fundamental minimum requirements and are far too general to do much more than suggest some procedure which may or may not be safe or healthful. Most of them are grotesquely out-of-date as applied to present-day conditions, and none of them is adequate to protect life, limb, health, or property. Unquestionably, there is great need for a closer correlation of the laws and regulations of the various States with regard to safety in the mining and allied industries, and while mining conditions vary far too much for a standardized mine safety law applicable to all of the States, on the other hand there are numerous standard and fairly fundamental safety pro- visions which apply to all mines and which should be embodied in the mining codes of all States. Undoubtedly, these standardized safety requirements would be opposed by a consider- able part of the industry, but the ultimate effect would be beneficial to the owners, work- ers, and the general public. For many years progressive mining companies in the United States have not been satisfied to operate only within the meager safety requirements of the State laws or regulations and have adopted additional and far more effective safety procedure of their own, although com- plying also with the State laws and regulations. As a result of this forward-locking policy, zany of these companies have made astonishing progress in the reduction of accidents.

Dec 1, 1935

By 1980, the U.S. mining community had reached a broad consensus regarding coal pillar design. The pillar load could be estimated from tributary area theory, and the pillar strength from empirical formulas and laboratory coal strength testing. Then the growth of longwall mining required new thinking. Recently, powerful design methods have emerged from analysis of large data bases of real-world pillar successes and failures. These include the Analysis of Retreat Mining Pillar Stability (ARMPS), the Analysis of Longwall Pillar Stability (ALPS), the Mark- Bieniawski rectangular pillar strength formula, and guidelines for preventing massive pillar collapses. Sophisticated numerical models have also helped transform the pillar design landscape. In the process, our understanding of pillar mechanics has been greatly enriched. A new paradigm divides pillar failure into three categories:

By R. B. Schluter

The Bureau of Mines investigated the flotation responses of two copper-nickel ore samples from the Duluth Complex with the objective of recovering bulk sulfide concentrates. One of the ores studied was taken from a test pit; the other was taken from a test shaft. The samples were quite similar except that the pit sample analyzed 0.35 pct Cu and 0.11 pct Ni and the shaft sample analyzed 0.69 pct Cu and 0.14 pct Ni. Flotation responses were studied in both laboratory and pilot plant tests. Pilot plant flotation responses were similar for both samples resulting in grades of 12.2 pct Cu and 2.5 pct Ni for the pit sample and 12.2 pct Cu and 2.1 pct Ni for the shaft sample. Weight recoveries were 2.5 pct for the pit sample and 5.2 pct for the shaft sample. Copper and nickel recoveries for the pit sample were 87 and 62 pct, respectively, and 92 and 73 pct for the shaft sample. Both concentrates contained small but significant values of cobalt and precious metals. Cobalt recoveries were low--less than 40 pct for both concentrates. Precious metals contents of the concentrates were 1.59 oz/ton for the pit sample and 0.99 oz/ton for the shaft sample. Silver was the predominant precious metal by weight, but platinum and palladium represented the highest values.

Jan 1, 1980

By E. V. Cilento, K. A. DiGregorio, R. C. Lantz

Pulmonary inflammation is accompanied by increased microvascular permeability and leakage of plasma into alveolar spaces. Serum has been shown to affect superoxide (O2-) production from pulmonary alveolar macrophages (PAM) in vitro, and in some cases serum has been shown to be necessary for stimulation of PAM. An electro-optical method was used to measure O2- production from single PAM by measuring the reduction of nitroblue tetrazolium (NBT) to a diformazan precipitate (NBTH2) from videorecorded images of individual cells. PAM were stimulated by their initial attachment to culture dishes independent of serum. The addition of 2% serum to the culture medium increased NBTH2 production during attachment, whereas concentrations of 5 and 10% serum had no additional effect. In contrast, PAM incubated for 2 hrs could not be stimulated by phorbol myristate acetate (PMA) or zymosan particles to produce O2- unless serum was present during the incubation and/or stimulation; however, NBTH production was similar in all cases of serum addition. Also2, serum alone did not stimulate adherent PAM indicating that serum is necessary but not sufficient for stimulation of attached. PAM. These results suggest that changes in microcirculatory permeability may have a pronounced effect on superoxide production by PAM and that serum may help regulate or condition these cells during inflammation of the lung. (Supported by USBOM Gll35142.)

Jan 1, 1988

By E. V. Cilento, K. A. DiGregorlo, R. C. Lantz

A kinetic model was developed to describe the production of superoxide (02) by single pulmonary alveolar macrophages (PAM). Model predictions were compared to experimental results obtained from single rat PAM. The O2 - was quantified by measuring the reduction of nitroblue tetrazolium (NBT) to a diformazan precipitate (NBTH2) from video-recorded images of individual cells. The kinetic model considered three reactions: (1) the production of extracellular 0 - from the reduction of oxygen by NADPH oxidase using intracellular NADPH as the substrate, (2) the subsequent dismutation of o2- to from O2 , and (3) the reaction of o2- and NBT. NBT specificity for o2- was analyzed by comparing results in the presence and absence of superoxide dismutase (SOD) which catalyzes the dismutation of o2- to H2o2. Measured PAM heterogeneity was accounted for by varying the concentration of intracellular NADPH, its rate of depletion, and the concentration of intracellular NADPH oxidase in the kinetic model. Model predictions compared favorably with experimental results except when SOD was present. This discrepancy may be due to diffusional limitations since NBT is a relatively small molecule (818 MW) compared to SOD (34000 MW). In addition, the cell surface is both ruffled and negatively charged, which may introduce steric hindrances and/or electrostatic effects since SOD is also negatively charged.

Jan 1, 1988

By Joseph W. Town

The Bureau of Mines conducted studies related to SO2 air pollution to determine attritioning rates, SO2 sorption rates, and sulfur loads that could be obtained on commercial alkalized alumina sorbent pellets. Fluidized-bed attritioning rates ranged from 0.025 pct/hr for alkalized alumina with a crushing strength of 4 kg to 0.075 pct/hr for 0.5 kg crushing strength mate¬rial. Airlift attritioning rates ranged from 0.50 pct/hr for 3 kg crushing strength alkalized alumina to about 3 pct/hr for 0.5 kg material. Attritioning rates for the commercial alkalized alumina were comparable to those obtained for sorbent pellets prepared in the Bureau of Mines laboratory. Sorption rates were related to S02 concentration in flue gas, temperature, and presence of nitrogen oxides in the gas stream. Sorption rates at 300° C were 0.35 X 10-6 gS/gp/sec (grams sulfur per gram pellet per second) in 0.045 pct so, gas, 5.1 x 10-5 gS/gp/sec in 0.34 pct SO2 gas, and 65 X 10-5 gS/gp/sec in 10 pct SO2 gas. For the 0.34 pct S02 gas, sulfur loads of 0.10 gS/gp (the projected load for regeneration) were obtained in 47 min at 130° C and in 116 min at 300° C. The presence of either NO or NO2 in the 0.34 pet S02 gas increased the SO2 sorption rates 2 to 3 times at 300° C, but had no effect at 130° C.

Jan 1, 1969

"A coordinated, integrated research effort aimed at studying the scientific, engineering and medical aspects of the respirable dust problem is underway in the areas of dust generation, dust dispersion and dilution, dust characterization, interaction of dust and lungs, and relationship of seam characteristics to dust generation and mobility. (FIGURE 24) The Center's research program explores these concerns with the objective of refining existing strategies and developing new respirable dust control techniques that are consistent with the dust-lung interaction processes that lead to mine worker disability. The fundamental aspects of this work are applicable to the control of respirable dust problems in both hard rock mines and coal mines and to other dusts such as diesel-generated.Research projects in the Generic Mineral Technology Center for Respirable Dust have effected several improved methods for the preparation and characterization of the dusts needed by these projects. Superior procedures for generating ""standard"" dust samples have been developed and are in regular use in the laboratory. Questions raised during the course of some projects regarding ""stale"" versus ""fresh"" dust have led to the development of sampling techniques where the dust is directly collected in a surfactant. MSHA and CANMET have requested and received information on Center generated software. An equipment manufacturer, TSI, Inc., requesting input on modifying the inlet of an aerosol sampler has been assisted as a result of research that was conducted at the University of Minnesota.The objectives, scope and progress of all the research projects in the Center, in the form of abstracts and reports, have been detailed in Volume 1 of this series. Research papers written by the principle investigators and resulting from the findings of projects (FIGURE 25) and which are funded by U.S. Bureau of Mines grant number G1135142 have been published in Volumes 3 through 6 and Volume 8 of this series. Volume 2 relates the cooperation and interaction of the U.S. Bureau of Mines and the Generic Mineral Technology Center for Respirable Dust in research on the problem of respirable dust in the mineral industries."

Aug 31, 1989