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By Gregory J. Chekan

In order to reduce waste and improve resource conservation, mine planning, and development, the U.S. Bureau of Mines is investigating multiple seam interactions associated with longwall mining. Longwall gate entry and panel stability have been influenced by previous mining in coalbeds above and below a mine in Virginia that operates in the Lower Banner Coalbed. Directly superjacent, approximately 115 ft, the Upper Banner Coalbed has been partially worked by room-and-pillar mining. Directly subjacent, approximately 730 ft, the Tiller Coalbed has been worked by partial room-and-pillar retreat mining. The study mine has experienced problems during development of gate entries in areas of overmining and undermining. It is anticipated that stress fields associated with adjacent mining may further affect gate entry stability and face advancement during the extraction of the longwall panel. To assess overmining and undermining effects on ground stability, the Bureau gathered geotechnical information at the site. Headgate entries and pillars were instrumented and monitored to study loading behavior as the longwall face approached and passed potential problem areas. Measurements indicate that although increases in average pillar pressure were greater than predicted values, previous mining in adjacent coalbeds had little effect on headgate stability.

Jan 1, 1989

By Collin Stewart, Greg Hunt, Christopher Mark

Bowie Resources maintains one of the most pro-active ground control programs in the U.S. mining industry today. Its guiding philosophy is that everyone in the organization, from the miners at the face all the way through the top management, are involved in ground control. Some of the unique elements of the Bowie ground control program include: • Roof bolt operators log the stratigraphy of test holes in nearly every cut. These “lith-graphs” are used by section foremen to determine the need for additional roof support, and they are entered into the geologic data base for use in geologic modeling and mapping. • Underground core drilling is conducted to obtain data for CMRR and stability maps. • Weekly “Quality” meetings, involving mine management and technical staff, are held to ensure that ground control information is integrated into production operations. The paper will describe the program in detail, discussing the involvement of roof bolters, section foremen, surveyors, technical staff, and production managers. It will also show how the program has contributed to the mine planning process. Case histories of successful ground control interventions will be discussed.

Provide longwall operators with practical information and guidelines concerning mine design to reduce problems associated with the interaction of adjacent workings in multiple-scam longwall mines. Background The high productivity achieved by longwall mining demonstrates its potential to provide a substantial segment of underground coal production. Longwall mines produce more than 30 pct of underground coal, up from pct just 15 years ago. However, the continued growth of this mining method without appropriate multiple-seam planning may increase the cost and risk of mining. Research by the U.S. Bureau of Mines (USBM) indicates that 25 longwall mines (32 pct of the total number in the United States) have mining in adjacent coalbeds either above or below. About half of these longwall mines report some type of interaction problem with the adjacent workings, such as caving due to subsidence. Optimization of mine design factors is the best means for controlling interactions between operations in adjacent scams. To avoid higher mining costs, operators should focus on adopting practices and procedures that prevent and control interactions in multiple scams. The USBM, in an effort to improve longwall mine planning, has been investigating multiple-seam longwall design and development.

Jan 1, 1994

By T. R. Taubert, D. H. Carlson, J. H. Johnson

The U.S. Bureau of Mines and Michigan Technological University (MTU) are collaborating to develop an apparatus for measuring diesel tailpipe emissions in underground mines. A tailpipe emissions measurement apparatus (EMA) is described that dilutes diesel exhaust and measures the concentrations of diesel particulate matter (DPM), CO, CO, NO, and NO, at known dilution ratios. The EMA was evaluated by side-by-side comparison of its measurements with those by laboratory- grade instruments. Concentrations of CO and CO, measured by the EMA were usually within + 14 pct of concentrations measured by laboratory-grade instruments for CO and 220 pct for CO,. EMA- measured DPM concentrations were, on average, 29 pct lower than those measured by laboratory-grade instruments, with the differences being fairly consistent. The CO and CO, differences are related to the method of calculating the EMA's dilution ratio, and the difference in DPM concentrations is attributed to thermophoretic and/or condensation losses related to the EMA's unheated sample probe. Preliminary analysis of data obtained with a heated sampling probe and modifications in the sampling procedures have indicated reduced variability in DPM and in the calculated dilution ratios.

Jan 1, 1992

Detect hazards associated with abandoned mine openings through the use of integrated geophysical technology. Background Many abandoned mines in the U.S. present hazards to the public. The first step in abatement of these hazards usually requires locating the abandoned workings. Recent Colorado legislation resulted in a concerted effort aimed at mitigating the hazards associated with abandoned mine workings. The Colorado Department of Natural Resources-Mine Land Reclamation Division (CDNRMLRD) is responsible for locating and backfilling abandoned mine openings such as shafts, adits and collapsed features. Many shafts and adits can be located by inspection, other openings give little or no surface expression and must be located by drilling, or through the use of geophysical methods. A common method used for locating underground mine workings is to drill throughout the suspected area. However, it is prohibitively expensive to drill holes at the spacing needed to detect backlilled shafts and small voids associated with caving and/or chimneying. It may also be dangerous to move heavy equipment over shallow mined-out workings. Geophysical investigations that employ only a single method have had mixed success in detecting hazardous abandoned mine land cavities.

Jan 1, 1991

By Steven E. Mischler

The exposure of mine workers to diesel particulate matter (DPM) and gases is an issue of great concern to the underground mining community in the United States. Approximately 30,000 underground miners are potentially exposed to high concentrations of DPM. In January of 2001, the U.S. Mine Safety and Health Administration (MSHA) promulgated rules setting compliance standards for both underground coal and metal / nonmetal mine workers. As industry works to achieve compliance with these standards, mine operators are looking for feasible methods for reducing DPM concentrations in their mines. In addition, the industry needs methods to accurately measure DPM to ensure that the control strategies they adopt are working successfully. The Pittsburgh Research Laboratory (PRL) of the National Institute for Occupational Safety and Health (NIOSH) conducts research to evaluate control technologies and monitoring instrumentation that can be used to reduce the diesel particulate matter (DPM) exposure of mine workers. An overview of the strategies being utilized in underground US mines to reduce DPM concentrations will be presented. Also, updates on the development of diesel monitoring instruments such as the continuous elemental carbon monitor or the Personal Dust Monitor for DPM measurement will be provided.

Jan 1, 2010

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.

By John C. Edwards, Gerald S. Morrow

The U.S. Bureau of Mines has constructed a smoke chamber and developed sensitivity tests for smoke detectors. Response of ionization- and optical-type commercially available smoke detectors have been investigated. Six smoke detectors were measured with respect to visually obscuring smoke characterized by a corresponding optical density for smoldering and flaming coal combustion in the smoke chamber. It was determined that for one type of ionization smoke detector the alarm time was nearly equivalent to that of an odor monitor's alarm for smoldering coal combustion experiments and earlier for flaming coal combustion experiments. The experiments showed that an average CO concentration of 5 ppm corresponded to an optical density of 0.022 m for smoldering and flaming-1coal combustion. Two of the commercially available ionization-type smoke detectors were more responsive to flaming than smoldering coal combustion at an optical density of 0.022 m, whereas the optical smoke detectors-1showed the opposite trend. The responsive characteristics of the detectors evaluated with respect to known smoke conditions in the smoke chamber shows their potential for use as mine fire sensors or part of a mine atmospheric monitoring system to improve mine safety.

Jan 1, 1995

Determine the extent of upper extremity cumulative trauma disorders (UECTD's) in the U.S. mining industry. Background UECTD's are injuries that develop gradually over a period of time as a result of repeated stress to a particular body part without adequate time between stresses for full recovery to occur. The stresses that contribute to UECTD's may occur because of the following work components: awkward position of wrist or arm, excessive manual force, high repetitions of manual movement and effort, cold environment, and vibration. Cumulative trauma injuries to the arm and hand have become an ever growing concern among safety and health professionals in a number of different industries and work settings, such as meatpacking operations, assembly-line work, and keyboarding. Mine workers arc also exposed to a combination of stressors and work design deficiencies that result in arm and hand injuries. For example, certain job tasks and environments, such as that of an underground jackleg driller, expose miners to segmental (hand-arm) vibration and cold temperatures. Operators of underground mobile equipment, such as scoops and trams, regularly have their hands in direct contact with vibrating levers and controls.

Jan 1, 1992

By M. E. Poad, M. M. McDonald, J. C. Johnson, W. G. Pariseau

A U.S. Bureau of Mines case study of pillar recovery in high-grade ore near the Ross shaft at the Homestake Mine, Lead, SD, has demonstrated the usefulness of the finite-element method for evaluating shaft pillar mining plans and shaft stability. In this study, borehole extensometers and other instruments were installed to provide data for model verification and to monitor shaft displacement. Results of a recalibrated two-dimensional model (UTAH2)confirmed the premining stability evaluation. However, after mining began, concern developed because of cracks and other signs of ground motion that appeared at considerable distances from the area of active pillar mining. An intense three-dimensional modeling effort using the computer modeling program UTAH3 was initiated. The results again showed the observed effects were within expectations and that the shaft would remain safe. Three-dimensional analyses of alternate pillar mining scenarios indicated that more of the shaft pillar ore reserve could be recovered than previously thought on the basis of two-dimensional analyses. This report focuses on startup and implementation of the three-dimensional model, calibration of the three-dimensional model, and application of the model to shaft pillar mining.

Jan 1, 1996

By C. M. K. Boldt, R. L. Levens, A. D. Marcy

Researchers at the U. S. Bureau of Mines conducted investigations to evaluate the potential for ground water contamination by mine waste used as backfill. Samples of cemented waste backfill and water discharging from drillholes and seeps were collected to use in chemical analyses and laboratory tests to determine the physical and chemical factors that control release of heavy metals to ground water. Greater water retention by cemented backfill (as compared to uncemented sandfill) reduces the surface are aexposed to oxidation, which in turn reduces the amount of acid produced. The acid is neutralized by the cement and minerals contained in the backfill. The grain-size distribution of tailings used for backfill affects the structural integrity of cemented backfill under attack by acidic water; breakdown of the backfill structure releases neutralizing materials faster. Backfilled stopes in rock with low hydraulic conductivities will constitute preferential flow paths after mine flooding; however, the rate of flow through backfill will be much slower than when the stope is partially saturated during mine operation. Considering all factors, acid generation and release of metal ions from cemented backfill should be less than in uncemented sandfill.

Jan 1, 1995

By F. E. Walker, S. J. Aresco, J. B. Janus

The Bureau of Mines has been active in promoting the purchase of coal for Government use under specifications that define the requirements in terms of heating value of the coal , expressed in British thermal units , and the composition as shown by proximate analyses . To these , when required , are added the ash- softening temperature , the free- swelling index , and the Hardgrove grindability index . Under most of these specification contracts the bidders guarantee the quality of the coal , and that guaranteed by the successful bidder becomes the standard of his contract . The deliveries are sampled in accordance with instructions 4/ issued by the Bureau of Mines ; the samples are analyzed in the Bureau laboratory to determine whether the coal is of the quality guaranteed by the contractor and , if it is not , a price adjustment is made . Analyses of the delivered coal and tipple samples (samples collected at mine tipples as coal is being loaded into railroad cars or trucks ) provide valuable data for use in evaluating future bids . In addition , the continuous sampling of coal as delivered is a check on the practical results obtained in burning the coal . The Government purchased approximately 5 million tons of coal in fiscal year 1963 . In connection with these purchases , the Bureau analyzed 6,999 samples . These are published ( table 1 ) for the use of Government officials and the public . A series of publications has been completed on coal analyses by States or , where production is small in any one State , by groups of adjacent States . In addition to analytical data showing composition and quality of coals of the States , the publications contain brief descriptions

Jan 1, 1964

By R. W. Lowe

1. Reserves are estimated in the Nemo, Sewanee, Wilder, and White Oak beds of Fentress County, Tenn. The Wilder is the only bed being mined commercially and contains the largest known reserves. Eleven lesser known beds are present in the county, but not enough information on them was available for estimating the reserves. 2. Known measured and indicated reserves, based on a minimum bed thickness of 14 inches and on 1,800 tons per acre-foot of coal in place, are estimated at 102 million tons as of January 1, 1955. This total includes 66 million tons in beds 28 inches and more thick.

Jan 1, 1956

By J. P. Capp

The Federal Bureau of Mines and the Alabama Power Company conducted an experiment in underground gasification of coal at Gorgas, Ala. involving the use of hydraulic fracturing to increase the air acceptance of a coalbed for the introduction of combustion air and removal of product gases. Air acceptance is defined as the flow rate of air which can be injected into the coalbed at 65 p.s.i.g. This was the second time the hydraulic-fracturing technique was used at Gorgas. Sand suspended in a heavy oil served as the fracturing fluid in the first experiment; in the second the sand was two to six times larger and was suspended in a water-starch gel. In addition to providing further tests of the underground-gasification process, the purpose of the second experiment was to determine the effects of the larger sand and greater volumes of a water-base fluid on (1) the extent of the fractured area, (2) the air acceptance of the coal, and (3) the rate at which a gasification path could be carbonized (linked) through the coal, and to compare these results with those of the first experiment. The coal was fractured by injecting 11,000 lb. of sand and 33,580 gal. of water and water-gel at 200 to 600 g.p.m. and 900 to 1,000 p.s.i. The fluid fractured the coal and the sand served as a propping agent to hold the cracks and crevices open. Pressures during the fracturing operation at test boreholes indicated that the fracturing fluid extended only about 150 ft. from borehole H, the point of application of the fracture. Injection of air revealed that the air acceptance of the coalbed within this e t was materially increased. On the other hand, increased air acceptance also was noted at boreholes up to 280 ft. from borehole H and at the electrolinking area 300 to 400 ft. away, indicating that the fracture effects extended considerably farther than was evident from observation. Similar effects were noted at approximately the same distances after the first hydraulic fracture.

Jan 1, 1961

By Albert W. Deurbrouck

The preparation characteristics of the coals of Buchanan County, Va., are described in this Bureau of Mines report. Twenty-one samples ,,,ere collected from 9 coalbeds in the county. Of these samples 13 were of metallurgical quality as received, and 8 required some upgrading to provide acceptable products. In general, the coals were of low to medium ash and sulfur content, and ranked as medium-to high-volatile bituminous. In 1963, production in the county was in excess of 13 million tons, of which 2.2 million tons were mechanically cleaned.

Jan 1, 1966

By D. E. Redmon

Linear programing provides a mathematical technique by which activities can be planned in such a way that an optimal result is obtained. Routine applications of linear programing require only a knowledge of algebra. However, a complete understanding of the fundamentals of linear programing requires a knowledge of advanced mathematics. The purpose of this publication is clarification of terminology and illustration of applications in comparatively simple mining problems. Two mining situations are considered: Mine stopes from which ore is to be produced at a minimum production cost; also, uranium mines from which ore is transported to one mill, a maximum monetary value is desired. The details of data arrangement for solution by linear programing are described and the solutions are presented. Results of these solutions indicate successful applications of linear programing to mine production scheduling.

Jan 1, 1964

By James W. Miller

An investigation was begun by the Bureau of Mines in 1948 to determine the preparation characteristics of American coals. Results of the investigation were planned to be reported on a county basis and from the data developed, to determine: (a) Which coals either as mined or after beneficiation by conventional preparation are chemically suitable under present standards for producing metallurgical coke; (b) Which coals require special and more intensive treatment in preparation than is now practiced; and (c) Which coals cannot be considered potential sources of metallurgical coke, regardless of preparation. This report is one in this county series that describes the preparation characteristics of the coals of Perry County, Ky.

Jan 1, 1956

By Clyde E. Eilliams

In recent ye.ars much intere,t has been centered on the possibility of pro­ducing alumina from clq, a.nd proposed methods tor the recove:r,v of alumina are appearing constantly in parent lit,erature, As a good· grade of clay contains from 30 t<> 40 per cent of al"WDina, the prospect of tecovering it is alluring, al though obviously ditfieul t. A patent typical of m projected thermal processes is that 0£ Paul Migu.et, (U, S, Patent No, l,376,563) entitled nprocess for the preparation of pure alkaline alu:ninates.'' Re proposes to prepare alkaline a.luminate by fusing clay, lime, and acrap iron with a reducing aget in the electric furnAce, thereby reducing the silica a.r.d formin1s calcium alumina.te and ferrostlicon, The calcium aluminate, being lighter, would. float on top substantially free from foreign oxides, It could. then be tapped ott, cooledf ana later crushed and leached with aodium carbonate solution to torm, by double decomposition, sodium aluminate, and calcium carbonte. The fonMr is soluble and yields readily aluminum hydroxicie. 'l'he ferrosilicon wo'Uld be r,covered as such and sold at a profit.

Aug 1, 1922

By T. E. Gray, A. W. Deurbrouck

This report describes the preparation characteristics of significant coalbeds in Kanawha County , W. Va . It is one in a series of Federal Bureau of Mines reports planned to determine coals suitable for producing metallurgical coke , either as mined or after beneficiation . Almost 9.4 million tons of coal was produced in Kanawha County , W. Va . , in 1959 , of which about 67 percent was cleaned mechanically in 10 cleaning plants . It has been estimated that more than 5,505 million tons remain in the county . Samples were collected from Pittsburgh , Stockton - Lewiston , Winifrede , Cedar Grove , Peerless , Upper Kittanning , Coalburg , Powellton , Eagle A , No. 2 Gas , and the Lower Kittanning beds . These beds were selected by the Bureau based on current production rates and estimated minable reserves . Float - and - sink tests of the samples collected from Eagle A , Peerless , Cedar Grove , Winifrede , and No. 2 Gas beds show that these coals at one location each are suitable for metallurgical use without washing . Lower Kittanning bed at four locations ; Pittsburgh , Stockton - Lewiston , and No. 2 Gas beds at two locations each ; and Coalburg , Powellton , Winifrede , Peerless , Upper Kittanning , and Cedar Grove beds at one location each can be upgraded to metallurgical quality by mechanical cleaning . Crushing the samples to 3/ 8- inch top size increased yields substantially at 1.30 specific gravity of Pittsburgh ( 17.5 percentage points ) and Upper Kittanning ( 13.0 percentage points ) beds and increased yield for the other beds sampled to a lesser amount . At this specific gravity , finer crushing caused In the 1.58 specific gravity float a general decrease in ash and sulfur . fractions of the other samples tested , most of the yields , and ash and sulfur contents , were lowered slightly by finer crushing .

Jan 1, 1963

By Thomas M. Barczak

The success of longwall mining can largely be traced to the development of powered roof support systems. The most significant improvement in powered support design has been the shield support, which improved kinematic stability and promoted the application of longwall mining in difficult-to- control caving conditions where chock and frame supports were inadequate. The most obvious trend in shield design has been an increase in shield size and capacity. This U.S. Bureau of Mines report examines shield design and operation practices and their consequences for the utilization of high-capacity shield support systems. An optimization goal is to minimize support loading by selecting an active shield setting force that is compatible with strata behavior and shield loading characteristics. Shield stiffness is an important design parameter that is often overlooked. A consequence of increasing shield capacity by incorporating larger diameter leg cylinders is a proportional increase in shield stiffness. Setting forces have also increased in direct proportion to the increase in shield capacity. The increased stiffness and higher setting force cause the available capacity to be consumed more quickly, severely limiting the ability of high-capacity supports to last longer and provide reserve capacity for difficult mining conditions.

Jan 1, 1992