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By Jon C. Volkwein

Advances in mining technology have enabled deeper seams of coal to be mined from the surface. Highwall mining is frequently used to mine areas at the perimeters of a surface mine when removal of the overburden becomes uneconomical or threatens environmentally sensitive surface features. At the same time, advances in materials and technology have enabled highwall mining of coal that create blind headings over 300 meters in length. Deeper surface mining and deeper highwall penetration depths have lead to more frequent encounters with methane gas. While this coal is remotely mined from the surface, underground ignitions of methane have propagated to the surface and injured miners. Methods described in this paper show how this hazard can be correctly monitored and controlled for auger type highwall mining machines. Research indicates that small quantities of gas liberated during mining migrate to the face, creating higher gas concentrations than would otherwise be expected. Using the same principles that cause the gas to migrate to the face, researchers have shown that inert gas introduced at the collar of the hole can inert the entire hole, thus ensuring safe conditions for mining.

By M. Terry Hoch, George J. Karabin, James M. Kramer

This paper introduces the fracture mechanics approach—a unique way to predict the stability of a coal mine panel. The technique uses analytic equations to calculate the stress, strain, and yield characteristics of coal support systems. It uses fracture mechanics to model almost every type of mine support structure. Another feature is a method that incorporates field-tested knowledge into the analytical analysis. For example, this technique can model the yield characteristics of a coal seam by combining empirical pillar strength equations into the analytic analysis. It may be possible to simulate multiple-seam mining by incorporating subsidence methods into the analysis. The method is simple and quick, which makes it attractive for stress analysis software. It should be more accessible to those in the mining industry who do not have expertise in rock mechanics or numerical modeling. Although the purpose of this research is for modeling coal mines, it should be adaptable to any mine in a tabular deposit.

Jan 1, 1999

By G. H. Schnakenberg

In response to the underground mining industry's growing concern with the exposure of workers to the diesel particulate matter (DPM) component of diesel exhaust, a method was developed to estimate the average workplace concentration of DPM that could be expected from using the new lower DPMemitting engines now being approved by the US Mine Safety and Health Administration (MSHA) when these new engines are equipped with state-of-the-art exhaust-control, technology for filtering and combusting DPM. The resulting estimate uses the MSHA-reported particulate index for these engines, the prevailing rule-of-thumb ventilation rate of 150 cfm/hp and the available diesel-exhaust filter technology that has been shown to be at least 80% effective in reducing tailpipe DPM. In the estimate calculation, every engine used in an underground mine is assumed to be equipped with this control technology. Under the stated reasonable conditions, an average DPM level of 90 µg/m3 (mass) is predicted as technically feasible.

By John Ward Smith

The Bureau of Mines derived equations expressing the theoretical relationship between density of oil-shale rock and its organic content. Effects on theoretical shale density produced by variations in mineral composition and organic matter properties were evaluated. The theoretical relationship was extended to relate oil-shale density to oil yield in both oil weight and volume units by considering the fraction of organic matter converted to oil and the specific gravity of the oil produced. Corollary equations relating organic content by volume to organic content by weight and to oil yield were developed. The general relationships apply to an oil-shale deposit uniform in character. Application of the theoretical relationships to Green River Formation oil shales was demonstrated.

Jan 1, 1969

By J. Whyatt

A variety of dynamic failure cases with regional impact were described at a bump symposium held in 1958. These types of events, while rare, are of particular interest because their ability to impact a large area has disaster potential. These cases can be grouped into two broad classes of events by mechanism. These are (1) slip along steeply dipping faults and (2) fracturing of strong strata above, or below, the coal seam. Both failure modes produce dynamic or ?shock? loads on the perimeter (roof, rib, floor) of mine openings. Special consideration should be given to these failure modes in planning of deep coal mines since their occurrence is not within the professional experience of many contemporary workers, and their potential is not evaluated by many of the analysis tools commonly used to evaluate hazards in coal mine plans.

Jan 1, 2009

GLOSSARY Acid- and toxic-forming materials. Rock or coal layers containing significant amounts of pyrite or other minerals which, if exposed by coal mining, will cause acid or toxic drainage to occur when acted upon by air and water. Add mine drainage. Any water with a pH less s than 6.0 draining from a coal mine. Water is often orange-colored because of the presence of oxidized iron. Adit. An underground mine entry at sites where coal seams are exposed at ground level. Apple core. A complete hilltop (360°) left exposed by not backfilling the highwall. Approximate original contour. The surface configuration achieved by backfilling and grading the mined area so that be reclaimed land closely resembles the general pre-mining surface configuration and blends into and complements the drainage pattern of the surrounding terrain. Area mining. A surface mining method that is carried on in level to gently rolling topography on relatively large tracts of land. Active area mine pits may be several miles long. Arid and semiarid regions. Lands, generally west t of We 100% meridian, where water use by native vegetation equals or exceeds that supplied by natural precipitation, and rainfall is insufficient to support agriculture. Annual precipitation is normally 20 inches or less. Auger mining. A mining technique often used by surface mine operators when the overburden becomes too for the coal to be mined economically using traditional surface mining methods. Large-diameter (usually 2'-4') horizontal holes are drilled as much as 300 feet into We vertical Me of the coal bed by an auger. Like a bit used for boring holes in wood, coal augers consist of a cutting head with a screw-like extension. As the auger turns, the head breaks up the coal and the screw carries it back into a conveyor that loads it directly into a truck. Backfilling. The operation of refilling an excavation using material removed during the mining process. Bench. The level or flat working area at the base of the highwall that is excavated between the exposed coal seam and the original surface of the ground. Bucket wheel excavator. A continuous-digging machine that uses a rotating vertical wheel with buckets for large-scale stripping and excavating. Cessation Order. Order to cease mining issued to a coal operator by the regulatory authority due to severity of violations, Contemporaneous reclamation. Restoration of mined land that occurs as soon as practical after coal removal. Contour mining. A mining method commonly used in eastern mountainous topography where coal is removed in a narrow strip around the hillside. The extent of the cut into the hillside is determined by the depth of overburden at the highwall compared with the thickness of the coal seam. Daylighting. A term used to describe a surface mining procedure that exposes abandoned underground coal mine workings to enable removal of the remaining coal. Daylighting is followed by land reclamation. Dragline. An excavating machine, usually used in large, flat areas, that drags a bucket (which holds up to 220 cubic yards of material) toward the machine by cables, loads it with spoil, and then hoists it wit a boom up to 350 feet long, allowing the machine to excavate wide benches by depositing the spoil hundreds of feet away from the highwall. Grading. The process of smoothing the disturbed areas of the mine site, after the coal is removed, to closely approximate the pre¬mining terrain. Haul road. Any road constructed, improved, maintained, or used by mine operators and located within the permit area. Head-of-hollow fill. See "valley rill." Highwall. The cliff-like excavated face of exposed overburden and coal in a surface mine. Hydroseeding. Planting of seed mixed in a water medium. Water, mulch, lime, fertilizer, and seed are blended and sprayed onto regarded soil.

Jan 1, 1992

By D. Harrington

"The fire boss in coal mining and the shift boss in metal mining, though held responsible to a large extent for safety of underground employees and of the mine, are, it seems to me, not always vested with sufficient authority nor given compensation commensurate with their duties. The metal-mine shift boss, although his position as regards his relations between employer and employee, is frequently an unenviable one, has as a rule much more authority than the fire boss and is not expected to perform the menial tasks required of the latter by many coal-mining companies.In most coal-mining States the coal-mine foreman and the fire boss are re¬quired to possess a certificate of competency obtained by passing an examination. The foreman is legally responsible for the safety of the miners, as in most instances the superintendent is not required to pass an examination. Although the foreman is held legally responsible for the safety of the miners, the law does not, in general, compel the superintendent or other higher officials to delegate sufficient authority to the foreman to enable him to put his wishes or judgment into effect; and this condition has tended in many instances towards perpetuation of unsafe conditions.The fire boss is held legally responsible for conditions in his ""beat"", but he is generally given only such authority as the mine foreman sees fit to delegate, frequently very little, Moreover, the fire boss is generally required to cover his ""beat"" within two hours before the entrance of the underground workers. Only too often his territory is so great that in order to reach all the working faces and chalk the required date at the face, he must travel at a rapid walk or even run. When such haste is necessary to cover the required ground, it is manifestly im¬possible for the fire boss to make a careful inspection or examination of the roof, timbering, wiring, gas, etc., at each place, and doubtless in his hurry many unsafe conditions escape his notice."

Sep 1, 1920

By C. E. Coleman, Joseph D. Davis

During some distillation experiments conducted by the Bureau of Mines in cooperation with the Trent Process Corporation it was observed that amalgams of heavy petroleum oils and finely pulverized coal tended to produce a denser coke than that obtainable from the coal when retorted alone . Even anthracite coal when retorted with oil yielded a coke . This led the writers to believe that by mixing a lowrank coal ( sub-bituminous or even lignite ) - with asphaltic oil and retorting it, a coke suitable for domestic fuel could be made . Thus there was contemplated the production of domestic coke and the utilization of a low- grade oil in one operation . - In order to decide on the practicability of this process , it was necessary to know the value of products obtainable by such a method , as compared with those obtained by separate distillation . A laboratory method was therefore devised , and while it was realized that no small - scale testing apparatus for destructive distillation gives results that are directly applicable to commercial - scale operations , by keeping distillation conditions uniform for comparative tests , results were obtained valuable for purposes of comparison . The plan was to distill mixtures of coal and oil in a laboratory retort , and then distill the constituents separately under the same conditions . The comparative quantities of products yielded were thus directly obtained , and their quality was determined by analysis . The following are the main points investigated : ( 1 ) Quantity and quality of coke ; ( 2 ) Quantity of oils boiling below 221 °C . ( gasoline stock) and oils boiling at 221 to 300° C . ( kerosene stock) ; and ( 3) Quantity and quality of gases .

Jan 1, 1922

By J. Nielen van der Merwe

For the last 3 decades, coal pillars in the Republic of South Africa have been designed using the well-known strength formula of Salamon and Munro that was empirically derived after the Coalbrook disaster. The database was recently updated with the addition of failures that occurred after the initial analysis and the omission of failures that occurred in a known anomalous area. An alternative method of analysis was used to refine the constants in the formula. The outcome was a new formula that shows that the larger width-to-height ratio coal pillars are significantly stronger than previously believed, even though the material itself is represented by a reduced constant in the new formula. The formula predicts lower strength for the smaller pillars, explaining the failure of small pillars that were previously believed to have had high safety factors. Application of the new formula will result in improved coal reserve utilization for deeper workings and enhanced stability of shallow workings.

Jan 5, 1999

By Charles L. Kimbell

The series summarizing the prices of the major nonferrous metals on the stock exchanges of the United States and the United Kingdom has been continued this year in tables 23 and 24. As a result of the lack of availability of comprehensive data on the prices of metals in Canada, the table that had presented that information in past years in this chapter has been discontinued and the price series for nickel that had been in that table now appears in the table presenting metal prices in the United States.

Jan 1, 1993

By H. O. Poppleton

This Bureau of Mines study was made to investigate a possible method for selectively removing the Si02 component of silicate minerals and ores. Of specific interest were aluminum ores and zircon. Methods are described for removing Si02 from these ores as volatile silicon sulfides by treating the ore with sulfur and carbon; with sulfur, carbon, and a reducing gas; or with sulfur compounds and carbon. Comparative results are also given for the desilication of some of the ores with carbon alone to form volatile silicon monoxide. The silica component can be removed partially from bauxites at temperatures above the sublimation temperature of SiS (940° C) by treatment with carbon, sulfur, and methane; however, it is more difficult to remove the silicon from kyanite, manganese silicate, red muds from aluminum processing, kaolinite, lateritic nickel ores, and zircon. Complete desilication requires temperatures ranging from 1,100° C for bauxite to 1,450° C for zircon. Although the high temperatures required and the undesirable metal sulfides produced eliminate practical application of this method using present technology, the Bureau is reporting this data so that they will be available to future investigators.

Jan 1, 1974

By Andrew D. O. O’Brien, Linda J. McWilliams, Joe L. Howell, Douglas E. Pollock, Jeanne A. Zimmer, Andrew B. Cecala

A quick, safe, and effective method has been developed that allows workers to clean their dust laden work clothing periodically throughout the day. For the mining industry, this technique is much more effective than the current federally approved method of using a vacuuming system. This newly designed method is relatively inexpensive and can be easily installed at any operation to allow workers to clean their clothing without contaminating the worker, the work environment. or co-workers to elevated respirable dust levels. This clothes cleaning process uses an air spray manifold to blow dust from a worker's clothing in an enclosed booth, which combines the dust for capture and removal by a baghouse dust collector. Since the air exhausted by the dust collector causes the booth to be under negative pressure. no measurable quantities of dust were ever measure escaping from the booth to contaminate the work environment and/or other workers. The worker performing the cleaning process is required to wear a half-mask fit- tested respirator with an N 100 filter, hearing protection, and full seal goggles. Dust samples taken inside the respirator of test personnel performing the clothes cleaning process showed very minimal to no respirable dust. This clothes cleaning process was performed in less than 20 seconds and was significantly y cleaner than either the Federally approved method of vacuuming, or the most common method or using a single compressed air hose. It was also determined during this research that polyester-cotton blend coveralls clean more effectively than coveralls which are 100 percent cotton. The newly designed clothes cleaning process has potential application to any industry where workers' clothing becomes contaminated with most any type of dust or product.

By Dana Reinke, Launa Mallett, Michael J. Brnich

Some segments of the mining industry, especially underground coal, have seen a large influx of inexperienced miners in recent years. It is anticipated that this trend will reach other mining segments over the next 10 years. This paper discusses the training needs of the younger generation of inexperienced workers who have just entered or are soon to enter the mines. Currently, many trainers are of the so-called Baby Boom generation. Can these different age groups learn to communicate across the generation gap? Even trainers who have been highly effective in the past should reassess their training styles and their classroom materials to determine if they are prepared to meet the needs of these new trainees.

Jan 1, 2002

By L. M. Chan, D. R. Carlson, J. H. Johnson

"This paper presents an apparatus and procedures to implement a methodology for controlling ambient air quality in a confined working environment, such as an underground mine, an underground storage area, or a tunnel. The air quality control methodology is directed at limiting the quantities of exhaust pollutants emitted by diesel-powered vehicles into the confined space by identifying vehicles that are excessive polluters. The methodology is based on tailpipe and ambient air measurements in the confined space, and the ambient air threshold limit values (TLVs) for the various diesel exhaust pollutants. The methodology consists of two computational methods; a deterioration criteria computational method to identify excessive polluting vehicles, and an engine performance computational method to determine engine performance and to provide information needed to diagnose engine faults. The methodology is designed for implementation in conjunction with a preventive maintenance program.The first part of the paper describes the mine air and tailpipe emissions measurement apparatus and techniques used to obtain data. This is followed by sections discussing the deterioration criteria and the engine performance computational methods. A section discussing some common engine emissions-related faults is also presented lastly, a proposed procedure to implement the methodology including a possible hierarchical structure for mine personnel involved to implement the procedures is presented.INTRODUCTIONDiesel-powered mining vehicles are gaining Popularity in underground coal mines and are almost universally used in underground non-coal mines due to their mobility, flexibility, and higher productivity. However, noxious gases and particulate matter in diesel engine exhaust are a concern because of the potential for being harmful to the health of miners. Diesel exhaust pollutant concentrations out the tailpipe of a mine vehicle change with time due to engine wear, inadequate maintenance, improper adjustments and other factors. This deterioration in pollutant concentrations, if not properly controlled, may adversely affect the air quality in an underground mine. To provide assurance that a clean and healthful work environment are maintained, a program is needed to identify and repair diesel engines that contribute to poor air quality. Also, earlier detection of deteriorated engines will make preventive maintenance possible, thereby eliminating further deterioration and possibly complete breakdown. Preventive maintenance also increases engine life and equipment availability in production which in turn will result in decreased operating costs."

Nov 1, 1995

By Richard L. Lewis

This is a discussion of the application of the zonal harmonic series to problems involving dipole sources in the vicinity of spherical boundaries. The application of a formal zonal-harmonic series solution to directly obtain numerical results involves two distinct problems: namely, the convergence of the series solution and the accurate calculation of the special functions involved in the series solution. Some interesting techniques will be introduced which help to improve the convergence properties of the series solution.

Jan 1, 1973

By R. S. Conti, C. D. Litton

This U.S. Bureau of Mines (USBM) report discusses the results of research conducted in the USBM experimental mine at its Lake Lynn Laboratory to determine the alarm times of smoke and carbon monoxide(CO) sensors, and a point type heat sensor (PTHS) to slowly developing coal-conveyor belt fires. The tests were conducted at air velocities of 0.44 and 0.97 m/s. The data clearly indicate that smoke sensors provide earlier warning of fire than 10 ppm CO sensors, and that 10 ppm CO sensors provide earlier warning than PTHS. A success rate of 1.0 (indicating detection of every test fire) was obtained for both smoke and CO sensors. For the PTHS, the success rate was 0.57 at the lower air velocity, decreasing to 0 at the higher air velocity. Data are also presented showing the sequence of fire events and detection events at the two air velocities as a function of time. Results show that early detection and warning of underground mine fires will improve the probability of miners’ escape.

Jan 1, 1995

By Vijia K. Karra

Making sure workers within the aggregates industry go home safely each day is the goal of aggregate companies throughout the United States. At the National Institute for Occupational Safety and Health (NIOSH) researchers are contributing to NIOSH’s vision of safety and health through a fact-finding approach to reducing injuries/illnesses in various mineral sectors. Surveillance data from the Mine Safety and Health Administration (MSHA) has been the primary source for such analyses. It helps to focus research efforts on key machinery, workers, and their tasks. The crushed stone category referred to in this article is represented as crushed and broken stone in the MSHA database.

By G. W. Groove, E. E. Quenon

"INTRODUCTION Uncontrolled mine fires originating in exposed coal beds through the acts of careless or irresponsible persons present a serious threat to buildings, surface property, and the life and health of persons near the affected area. Apparently, the seriousness of such fires is not fully understood by property owners or those residing in the vicinity, as practically nothing has been done to alleviate conditions. In many instances, such fires have been active for several years before property owners or civic organizations have shown any interest toward having the fire extinguished. Recommendations by Bureau of Mines investigators in the interest of controlling such fires are seldom followed, as the Bureau cannot provide the funds for doing the work.Several uncontrolled and widespread fires are burning along the outcrop of coal beds and in underground abandoned mine workings within a 25-mile radius of Pittsburgh, Allegheny County, Pa. If these fires are permitted to continue to burn unabated, the ultimate results may be far-reaching. Most of the outcrop fires investigated are believed to have originated from burning rubbish, forest fires, or workmen, hunters, or others building fires near the outcrop of ,the coal beds. In other instances, smoke and fumes have suddenly appeared in the vicinity of abandoned coal-mine openings, indicating that a fire has either burned its way along the outcrop of the coal bed or has traveled through the abandoned mine from another location. An underground or outcrop coal-mine fire will be very likely to continue to burn as long as an oxygen supply is present.; and, so far as is known, such fires do not stop burning automatically until virtually all combustible matter is consumed."

Feb 1, 1948

By M. L. Fenger, S. F. Mauser

This 1s a report on an Investigation performed during Contract No. H0166069 "High and Medium Voltage Trailing Cable Splices and Connections," which presents a summary of the requirements formulated. The requirements are presented in the form of considerations for medium-voltage splices, and medium- and high-voltage couplers used in underground coal mines.

Jan 1, 1979

By Kathleen M. Kowalski, Audrey Podlesny

The Maslach Burnout Inventory (MBI) was administered and scored for 154 Mine Safety and Health Administration (MSHA), U.S. Department of Labor, employees who serve as accident investigators for serious accidents and fatalities as part of their job duties. The subjects responded anonymously during a workshop on stress. The subjects consisted of randomly selected individuals, representative of locations across the country and representative of all mining commodities: coal, metal, nonmetal, stone, and sand and gravel. The Maslach Burnout Inventory assesses three aspects of experienced burnout: emotional exhaustion, depersonalization, and reduced personal accomplishments. The average results of the scores for each of the three subscales fell in the moderate range for the study group of MSHA accident investigators. The scores within the moderate range show that the subject population was at the lower end of the range for emotional exhaustion and depersonalization, tending toward a lower burnout risk, while the group evidenced a lower sense of personal accomplishment in their jobs, indicating a higher risk for burnout. It is concluded that overall this group is at moderate risk for burnout, and the authors recommend follow-up with this population.