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By J. J. Rutledge, C. A. Herbert

In 1916 the Bureau of Mines, the Illinois Geological Survey, and the University of Illinois, working under a cooperative agreement, began an investigation of the subsidence of the surface above coal- mining operations. Four widely separated places where mining was in progress were selected as observation stations-one in the northern Illinois longwall coal field, one in the central Illinois coal field where the room-and- pillar panel system of mining was being used, and two in the thick coal of southern Illinois where the room-and-pillar panel system of mining was employed. These four points of mining activity gave a rather wide opportunity for observing subsidence when different mining methods were used. The four places selected for investigation of surface subsidence due to coal mining have been designated as follows: 1. A, in the northern Illinois longwall coal field, where the coal company has been operating coal mines for 30 years and where long- wall advancing is the only method of mining. 2. B, in Perry County, where panel room-and-pillar mining of a thick seam of coal is in progress and where mining operations have been carried on about 40 years. 3. C, in Macoupin County, where the coal company has been min- ing coal by the panel room-and-pillar method for about 15 years. 4. D, in Franklin County, where the coal company has been mining coal for 10 years by the panel room-and-pillar method.

Jan 1, 1927

The Navajo Nation is the largest Indian tribe in the United States and occupies a reservation encompassing about 16 million acres in northeastern Arizona, southeastern Utah, and northwestern New Mexico, with three satellite reservations in western and west-central New Mexico. Coal mining is conducted on a commercial scale at four large surface mines: two are in northeastern Arizona and the other two are in western and northwestern New Mexico. The principal coal-bearing region in Arizona is the Black Mesa coal field, which underlies about 3,200 square miles in the northeastern part of the state. The Black Mesa coal field lies within the boundaries of the Navajo and Hopi Indian Reservations and makes a significant contribution to the economies of both tribes. Coal reserves in this field are estimated to be 352 million tons, less than one-tenth of one percent of U.S. coal reserves. This coal was first mined by prehistoric Indians as fuel for cooking and heating. It has been estimated that the Indians removed more than 100,000 tons between 1300 and 1600 A.D. The coal-bearing region of the Navajo Reservation in New Mexico is located in the San Juan Basin. The Navajo Mine, which supplies coal for the Four Comers Power Plant, is located in this area. The Office of Surface Mining's Albuquerque, New Mexico, Field Office is responsible for regulating mining and reclamation on Navajo land. The Navajo Abandoned Mine Land Program was approved May 16,1988.

Jan 1, 1992

By Mark Larson, Steve Iverson, Brian G. White

The authors hypothesize that excavation-induced extension fractures are caused by elastic shearing displacement that in turn causes tension oblique to a propagating shear zone. Such extension is manifested as tension on scales larger than that of microcracks. En echelon fracture patterns are a common result. FLAC modeling confirmed that localized tension is created near the corners of mine openings. In the model, tension was concentrated at the leading edge of a simulated fracture in a pattern that could promote the formation of an en echelon fracture. Particle Flow Code models confirm progressive formation of en echelon tensile failures with distance from an opening. The elastic displacements and the resulting fractures facilitate reduction in applied load at the expense of shear deformation and lateral dilation. Understanding the mechanics of fracture and deformation is vital for designing more effective ground support practices, a major objective of ground control research being conducted at the Spokane Research Laboratory of the National Institute for Occupational Safety and Health.

By Albert W. Deurbrouck

Dense-medium cyclone tests in 4-and 8-inch-diameter units have shown the ability of cyclones to make sharp separations down to 100 mesh when washing coals of a finer top size than normally fed to dense-medium cyclones. The reduced top size of the feed apparently allows the finer size particles to report to the proper product by reducing the effect of very coarse particles in the congested separation zone of the dense-medium cyclone.

Jan 1, 1974

By Launa Mallett, Charles Vaught, Michael J. Brinich

The lack of good communication is a very real problem in mine emergencies. Sometimes critical information is not communicated to those who need it to make decisions. At other times, those on the receiving end of a warning do not think to ask the right questions. What happens in underground coal mine fires is a case in point. The authors interviewed 48 workers who escaped three serious fires in western Pennsylvania. In each case the location of the fire was known but did not get communicated to many of those who had to evacuate. Sometimes, even the nature of the problem was not clearly communicated. Some workers began their evacuation knowing nothing about what was happening. In an effort to improve emergency communication National Institute for Occupational Safety and Health (NIOSH) researchers worked with safety professionals to determine what sorts of information are critical in a mine emergency. An extensive list was generated, which proved too long to be remembered by individuals. The list was therefore collapsed into six categories. A communication protocol was derived from these categories.

By T. R. Rehak

Blasting operations are an essential element in the recovery of our Nation?s mineral resources. The mining industry uses billions of pounds of explosives annually. The majority of blasting occurs in surface mining operations. Blasting results in the fragmentation and often the projection of rocks. Frequently, the rocks are thrown beyond the expected limits. Flyrock and failure to secure the blasting area dominate blasting-related accidents in mining, especially in surface mining. Blasting accidents in the mining industry tend to result in critical injuries or fatalities. Accident reports and information collected from the Mine Safety and Health Administration (MSHA) and other government agencies provide supporting evidence. According to the data collected, blasting-related accidents (in mining) were 11 times more severe than all other types of mining accidents. Blasting accidents are not unique to mining operations - the same situation exists in the construction field. In this paper the authors have compiled a list of the primary causes of flyrock and the failure to secure the blast area. In the next phase of this project, typical blasting scenarios will be reviewed which will highlight the main reasons flyrock and/or lack of blast area security occur. This will alert miners and construction workers to the current problems/hazards associated with blasting and to identify other safety measures to protect personnel.

Jan 1, 2000

By Raja V. Rarnani, Robert L. Frantz

"The Generic Mineral Technology Center for Respirable Dust (GTCRD) was created at The Pennsylvania State University and West Virginia University by a congressional initiative in 1983 responding to recommendations in the 1980 National Academy of Sciences study on the Measurement and Control of Dust in Mines. Many of these recommendations dealt with the need to initiate focused fundamental research for further professional progress in dust control. Long-term, sustained support was emphasized to develop expertise in respirable dust research. In creating this Center, Penn State and West Virginia University were specifically recognized for their expertise in and facilities for research on coal mining and medicine. Today, the Center includes the Massachusetts Institute of Technology, the University of Minnesota, and the Michigan Technology University. The Respirable Dust Center is the only organization that coordinates and integrates the medical, scientific, and engineering aspects of respirable dust disease. The Center works with the U.S. Bureau of Mines (USBM), Mine Safety and Health Administration (MSHA), the National Institute for Occupational Safety and Health (NIOSH), the United Mine Workers of America (UMWA), and the U.S. coal industry in defining the research priorities for the programs of the Center to enhance research synergism.The Center's mission is to enhance the health, safety and productivity of miners by advancing the fundamental understanding of all aspects of respirable dust associated with mining and milling and the interaction of dust and lungs to reduce the incidence and severity of respirable dust disease.All Dust Center activities are focused to be responsive to this mission, which is shared by the several federal agencies closely associated with the GTCRD. While significant progress has made mine atmospheres cleaner and healthier, respirable dust-related disease remains the nation's most pernicious industrial hazard.The goals of the GTCRD were formulated with recognition of the diverse scientific, engineering, and medical aspects of respirable dust, in addition to a need to enhance researcher interaction, as well as education and technology transfer efforts, in the respirable dust area. These goals reflect the needs of the mining industry as determined by the National Academy of Sciences Committee on Measurement and Control of Respirable Dust study done in 1980. The report of this committee encouraged the Bureau of Mines to redirect its research efforts ""...toward obtaining fundamental understanding of the origin, transport and characteristics of respirable coal mine dust."" The GTCRD's goals, detailed in chapter three of this document, were formulated to mesh with NAS recommendations."

Jan 1, 1995

By J. F. Barkley

"In trying various coals at one of the Government power plants, comparison was made of the ash softening temperature of each coal, with the clinkering tendencies of the coal when burned in the furnace. The proximate analyses, ash softening temperature and plant reports as to clinkering were tabulated. It was desired to bring out any correlation that might appear between the ash softening temperature found in the laboratory, and the clinkering of the ash as found in the boiler furnace.Each coal used was sampled and analyzed, and the standard ash fusion test made. The clinkerring of the coal in the furnace was observed by the furnace operator. The furnace equipment consisted of the ""V"" or Murphy type of stoker with the ordinary fire-brick arch roof. With such arrangement very high furnace temperatures are apt to be produced at the ratings carried at this plant.The softening temperature of ash is defined as the temperature at which small cone of the ash, as tested in the laboratory furnace, has fused down to a spherical lump, The softening interval is the difference between the softening temperature and the temperature at which the first rounding, or bending, of the apex of the cone takes piece. The flowing interval is the difference between the softening temperature and the temperature at which the ash has reached a fluid condition as shown by spreading out over the base in a flat layer.While the analyses of the different samples of the some coal did not vary appreciably, the ash softening temperatures were not always so consistent. It will be noted from the following examples that the ash softening temperatures of different samples of the same coal differ as much as 290° F, Hence, in order to judge this property of a coal, many samples ore desirable, taken from many different shipment."

Aug 1, 1924

By Fred N. Kissell

In This Chapter [Early indicators of a gas problem How the methane hazard is reduced Ventilation principles for gassy tunnels Monitoring for gas Eliminating ignition sources and The all-important human factors component] This chapter gives guidelines for preventing methane gas explosions during tunnel construction. Emphasis is placed on assessing the hazard potential, on ventilation principles, and on monitoring for gas. The chapter also emphasizes the importance of human factors in reducing explosion risk. Ensuring safe conditions is much more than just good engineering design. It also involves the every-day vigilance of those working underground. This does not imply that the engineering design can be ignored, only that the job of providing safe conditions has just begun with design. EARLY INDICATORS OF A GAS PROBLEM For the engineer planning a tunnel project, reliable early indicators of methane are scarce. How-ever, the local geology can often provide some information.2 Carbonaceous rocks and tar sands are a likely methane source. Gas is also a distinct possibility if it is known to be present else-where in the same sequence of geologic formations. Swampy areas, sewerage systems, and landfills are also candidates because the decomposition of organic materials produces methane. The gas in a tunnel can originate in the strata being excavated, or it can migrate a considerable distance from adjacent strata. Test borings at the project site can also serve as initial indicators of gas. Methane has no odor, but may be emitted along with gases that do. If gas is emitted from the borehole, a sample may be collected by inserting a tube into the hole as far as possible and pumping the gas out. The gas sample should be collected in a sampling bag or canister for later analysis by a chemical laboratory.3

Jan 6, 2006

By M. J. Ankeny

The expression "firing open, unconfined shots," as used in this circular, means the firing of explosive charges not confined in boreholes. Examples are the so-called mudcap shots, adobe or dobe shots, or bulldozing shots consisting of explosive charges placed on, under, or between rocks for the purpose of breaking them. The practice of firing open, unconfined shots is not uncommon in coal mines, despite the fact that numerous mine explosions and dust ignitions have resulted from this practice. The usual method of preparing such shots is to place the explosive with its detonator on top of a piece of rock or coal and cover it with clay, loam, sand, or road dust; frequently no covering of any kind is used. In some mines, an open charge of explosive is placed on timbers to dislodge them or in crevices in the roof to break down loose rock that cannot be dislodged with a bar or pick. The explosive charges may be made and fired singly, although sometimes several charges are placed on one large piece of rock with a detonator in each charge, and all charges are fired simultaneously. Although it is general practice to use permissible shot-firing devices, which will not ignite gas or dust to fire these charges, electric power from the regular mine circuits is sometimes used. When the shot is fired, any coal dust that may be present is thrown into suspension by the blast and may be ignited by the intense hot flame of the explosive or by an arc or spark at the leg wires or the end of the firing leads if power from the regular mine circuit is used to fire the shot. Even if there is not enough coal dust present to form a dust cloud, open, unconfined shots can readily ignite methane.

Jan 1, 1952

By R. B. Moore

The story of helium is one of the romances of science . Probably nothing , except perhaps radium , compares with it in human interest . Helium is one of the best examples of a discovery in pure science that has wide commercial application . In 1868 , an eclipse of the sun was visible in India , several scientific men who were in India making observations of the eclipse turned a spectroscope for the first time on the solar chromosphere - that part of the atmosphere of the sun , about 10,000 miles deep , which merges into the corona . A bright yellow line was observed and was thought at first to be due to sodium . Janssen showed , however , that this line was not just the same as either the D or D₂ line of sodium, although it was extremely close to these lines , hence he suggested that the new line have the designation D₂ . Frankland and Lockyer decided that Dz was due to an element in the sun not previously discovered on the earth , and suggested for it the name "Helium" from the Greek work " Helios " the sun . For several years nothing more was done in connection with this element . In 1894 , Sir William Ransay , in conjunction with Lord Rayleigh , made his memorable discovery of argon in the atmosphere , which was announced at the British Association meeting in the same year . After this discovery , Ramsay looked for other sources of the element . Through Sir Henry Miers , he learned that Dr. W. F. Hillebrand , of the United States Geological Survey , had obtained an inert gas from certain uranium minerals , which gas he had decided was nitrogen . Ramsay believed that part of it might be argon ; he obtained from Hillebrand for experimentation , a sample of the mineral , cleveite , one of the uranium minerals , and after extracting gas from the mineral and purifying it , he ran it into a spectrum tube . The lines obtained ' were , however , different from those of argon; among them was the bright yellow line noted by Janssen . Thus was terrestrial heliun discovered .

Jun 1, 1922

By C. J. Tsai, K. Olson, R. Caldow, B. Cantrell, D. Y. H. Pui

"The amount of new surface generated during fracture of coal and rock has been found to be directly proportional to the amount of energy associated with the fracture. To confirm this and study the relationship between the new surface and dust aerosol formed during fracture the U.S. Bureau of Mines has conducted experiments simulating fracture as it occurs during mining operations. In addition to fracture energy measurements, fragment size distributions were determined over a size range of 0.5 microns to 1 inch. The size measurements accounted for the mass of the original sample. Material studied was Illinois No. 6 coal, coal from the Taggart seam of Virginia, and Berea Sandstone. The experiment employed a chamber to confine sample fracture fragments and a combination of particle measuring systems. Measurement methods included aerodynamic sizing of entrained dust aerosol with optical counting and inertial impaction techniques, physical sizing of non-airborne fragments by sieving, and optical sizing of fragments using optical counting and scanning electron microscopy.Results of the size distribution measurements indicate that a single size distribution law does not adequately describe the entire fragment size distribution. A combination of two size distribution laws, such as the Rosin-Rammler and log-normal distributions, is necessary to describe this size distribution. New surface created by fracture is primarily found 1n particulate between 2 and 50 microns with a mean size of 12 microns. It was also found that the specific energy of fracture can be linearly related to the .concentration of aerosol in this size range.Only a .small fraction, between 0.02 and 0.16 pct, of the dust particles .generated during fracture become airborne. The remainder adhere to the new surface created during fracture. An entrainment fraction, defined for a given particle size is the ratio of the mass of airborne particles to that of the total particles generated in that size range. This experimental entrainment fraction is related to the Van der Waals adhesion force and the electrostatic forces operating during fracture and is used to derive empirical parameters to model these two processes."

Jan 1, 1989

By Frederick L. Hoffman

Miners' nystagmus is the result of a peculiar form of eyestrain, which often results in impairment of vision and a consequent diminu- tion of the wage-earning capacity of the workman. Historically it has been pointed out by Shufflebotham that "This disease was first recognized by Gillett, of Sheffield, about 1854, although no case was mentioned in medical literature until 1861, when the symptoms were described by De Conde, a Belgian physician. Cases were reported by Pepp Müller as early as 1860, by Von Graefe in 1873, and by Bell Taylor, of Nottingham, and by Nieden in 1874. In this country (England) we are indebted to a very large extent to the observations and writings of the late Simeon Snell and for his pioneer work on this many-sided disease; in France Dransart occupies a similar position." In the treatise on "The Effects of Arts, Trades, and Professions," by C. Turner Thackrah, published in London in 1832, it is stated that- The complexion of the colliers, even after the removal of the dirt, is generally sallow and unhealthy. Their eyes, from the swelling of the lids, appear small, are affected with chronic inflammation and intolerant of full light. * Sickness and vomiting sometimes affect persons at their commencing the employ; and many, after a few years' trial, are obliged, by the injury which their health has sustained, and especially by the weakness of their eyes, to leave the mine. According to Greer, an authority on industrial diseases and acci- dents, miners' nystagmus occurs in 5 per cent of all miners, but it is quite probable that the reference is to European coal miners rather than to men employed in all branches of the mineral industry. According to the same authority, miners' nystagmus "is associated with a twitching of the eyelids and with considerable diminution of the range of movement of the eyes, and is particularly liable to occur in patients whose vision is subnormal owing to errors of refraction, especially astigmatism. It causes much inconvenience to those suf- fering from it and prevents them from following their usual occupa- tion as, owing to the movements of the eyes, everything at which they look appears to be in a state of perpetual motion, and in conse-

Jan 1, 1916

By Charles L. Kimbell

This study is intended to serve three roles. First, it represents a global overview and summary to supplement and complement the five regional companion volumes of the 1991 edition of the Minerals Yearbook International Review. In this regard, it also extends previous time series under this title that appeared as the introductory chapter to the international volume of the Minerals Yearbook from the inception of that volume in 1963 until it was subdivided into separate regional volumes in 1989. The basic statistical presentations herein generally contain data through and including that for 1991, although in a few instances the most recent statistics are those for earlier years because more recent, comprehensive global statistics simply are not yet available owing to delays in data collection and processing in some countries and continued governmental suppression of data in others. The second role of this study is to provide an update to the coverage of events impacting the world's mineral industry that have occurred between the end of 1991 and the preparation of this study. Inclusion of this update is almost essential because of the potential effect of some of these events on global mineral industry activities.

Jan 1, 1993

Reduce the dust exposure of workers in large processing buildings at mineral processing operations, using a total mill ventilation system.

Jan 1, 1994

By D. A. Paice, A. B. Shimp

A test program was conducted to determine the adequacy of molded case circuit breakers for dc electrical systems in coal mines. Mine electrical system parameters and the most severe operating conditions to be expected were determined. Tests of the interrupting capabilities of several molded case breakers were made under the worst conditions to be expected. Continuous and pulsed current carrying capability of the breakers was also investigated. Breakers from two different manufacturers passed all tests successfully. Based on the results of these tests, a set of guidelines for applying molded case breakers to dc systems has been prepared.

Jan 1, 1975

By Paul M. Tyler

The alkali metals , sodium and potassium , and more particularly sodium , occur abundantly in chemical combination with other elements . The elements themselves are available in metallic form but are so active chemically that they oxidize rapidly in contact merely with the air . Potassium will even catch fire spontaneously in air , and both the metals will decompose water with explosive violence . Inasmuch as they are almost as soft as wax they are not suitable for the structural or other mechanical uses characteristic of ordinary metals , and consequently the uses of these elements even in the metallic condition are based upon chemical rather than physical qualities . Sodium metal is used largely as a commercial reducing agent , but potassium metal is rarely found outside of chemical laboratories . Numerous salts and other compounds of these elements enter largely into world trade and are commercially very important , but none of these compounds except sodium peroxide and sodium cyanide are made economically from the metals . Sodium is generally considered as rather an uncommon metal , but in point of annual tonnage produced it is far more important than mercury , magnesium , molybdenum , bismuth, cadmium, cobalt , gold , silver , or the various rarer metals .

Apr 1, 1932

By M. J. Sapko

The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) has conducted full-scale explosion experiments, to evaluate the strength characteristics of various seal designs, used for safely isolating worked-out areas in underground coal mines. Large-scale explosion tests conducted within the multiple entry section of PRL's Lake Lynn Experimental Mine (LLEM) is currently the only accepted test method used by the Mine Safety and Health Administration (MSHA), for deeming a seal design suitable for use in American mines. These explosion tests are labour intensive, expensive to conduct, and can interfere with other critical underground safety and health research programs conducted by NIOSH. The PRL has developed an alternative seal evaluation method, based on a hydrostatic pressure loading concept that can facilitate the in situ testing of seals in an operating mine. Two chambers within LLEM and one within PRL's Safety Research Coal Mine (SRCM) were used for hydrostatic pressure loading various seal designs. The results from these chamber tests compare favourably with those from the large-scale explosion tests in the multiple entries. In addition to testing seal designs at the required 20 psi static pressure level, the chamber test approach also allows for the determination of the seal's ultimate design strength. Six-scaling relationships for predicting the strength of seal designs as a function of entry size are also presented.

By Donald W. Mitchell, John Nagy, Edwin M. Murphy

Information is presented on remote sealing of a mine passageway through a borehole by five methods : PPnneeuummaattiicc injection of mineral wool and sand, ureaformaldehyde foam , balloons , urethane foam, and caving by blasting . An adaptation of the method using pneumatically conveyed mineral wool was tried in an operating mine . Further research is needed to simplify and to improve the techniques involved , as well as to explore the possibilities of other methods and combinations .

Jan 1, 1964

By Dean H. Ambrose

This paper presents an approach for representing and analyzing random motions and hazardous events in a simulated three-dimensional workplace, providing designers and analysts with a new technique for evaluating operator-machine interaction hazards in virtual environments. Technical data in this paper is based upon a project striving to reduce workers' risks from being hit by underground mining machinery in a confined space. The project's methodology includes human factors design considerations, ergonomic modeling and simulation tools, laboratory validation, and collaboration with a mining equipment manufacturer. Hazardous conditions can be analyzed in virtual environments using collision detection. By simulating an operator's random behavior and machine's appendage velocity, researchers can accurately identify hazards, and use that information to form safe design parameters for mining equipment. Analysts must be discerning with the model and not read more from the databases than what the simulation model was designed to deliver. Simulations provided an interesting approach to data gathering in that there was no need for live subjects and logistics - test sites and costs associated with experiments-became insignificant. Collisions versus speed, operators' size, and risk behaviors proved the versatility found in the data obtained from the model. Preliminary results show that response time significantly affects the number of collisions experienced by the virtual subject. Also simulation data suggests that more mishaps occur with hand-on-boom-arm risk behavior.