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By C. O. Karacan, S. J. Schatzel, W. P. Diamond

In coal mining, longwall mining is a preferred method to maximize production by extracting large blocks of coal that have been outlined with a set of development entries. In U.S. mines, longwall panels are typically 305 m (1,000ft) wide (with a continual trend towards even wider panels), and usually over 3,050 m (10,000ft) in length. The increasing size of longwall panels, while helping to increase coal production, may also increase methane emissions due to the exposure of the mining environment to a larger area of fractured, gas-bearing strata. Thus, understanding the impact of increased panel widths on methane emissions, and designing gob gas ventholes and bleeder systems accordingly, can enhance the safety of the underground workforce by reducing their exposure to potentially explosive accumulations of methane/air mixtures. As part of its mine safety research program, NIOSH’s Pittsburgh Research Laboratory has initiated a reservoir modeling effort to better understand the interaction of the various geotechnical factors influencing gas flow within and to the underground longwall mining environment. A focus of this modeling effort has been 1) the prediction of the incremental amount of methane emissions to be expected due to increasing longwall panel widths, and 2) optimizing gob gas venthole completion practices to capture more of the gas in the subsided strata above longwall panels before it can enter the ventilation system of the underground workplace. The history matching phase of the study has been carried out on a 381-m (1,250ft) wide panel in the Pittsburgh Coalbed. Simulations have also been completed for a 442 m (1,450ft) wide panel to estimate the incremental increase in methane emissions and the performance of current gob gas venthole placement configurations. Additional venthole placement configurations were simulated to investigate options for optimizing methane capture from the subsided strata above the wider longwall panel.

By Lincoln A. Stewart

"INTRODUCTION The First Supplemental National Defense Appropriation Act, approved August, 25,, 1941, authorized the Bureau of Mines to investigate sources of raw, material for western production and appropriated funds for that purpose. Numerous iron deposits and prospects in the Western States were investigated. Among those selected for more detailed investigation were tile Apache and Chodiski deposits in Arizona.The United States Geological Survey had examined these deposits in 1929 3/ and estimated that ""the quantity of minable ore reasonably to be expected in this locality will reach 10,000,000 long tons, but it will require prospecting by core drill to demonstrate this quantity with certainty"". C. H. Johnson, a mining engineer of the Bureau of Mines, made a preliminary examination in October 1941 and proposed exploration of the Apache deposit Canyon Creek.A trench sampling project was set up, and work at the Apache deposit commenced in November 1941. Mapping, trenching, and sampling of outcrops was completed in March 1942. Trenches were laid out at approximately 200-foot intervals for about 9,200 feet along the iron outcrop east of Canyon Creek, and channel samples were taken across the iron formation. The outcrop also was explored by trenching and sampling along a 1,900-foot outcrop on the west side of Canyon Creek.The first diamond-drilling campaign at Apache was initiated in May 1942 and continued to January 1943, when work was suspended owing to depletion of funds. Six holes spaced at approximately 500-foot intervals and, 500 feet back from the outcrop on the east side of Canyon Creek were drilled through the iron formation during this period.While this drilling was in progress, the Chediski deposit was mapped, trenched, and sampled. The trenches were spaced at intervals of approximately 800 feet along 10,000 feet of the iron-ore outcrop."

Jul 1, 1947

By Jon G. Bredeson

The electromagnetic noise that exists in a mining environment is quite severe and was shown to have been reasonably well documented by a number of researchers in the Phase I Report. The noise levels are such that prudent communication design requires the careful use of all the electromagnetic noise data available. A comprehensive survey was undertaken to determine techniques used in various industrial environments to achieve secure communications in the presence of electromagnetic interference. The techniques were given in the Phase I Report and are rudimentary, but have produced reasonably good results. A number of these techniques could be applied to the mining environment.

Jan 1, 1980

By PW Meisel

An hydraulic-powered reel system to minimize peak tension transients in shuttle car trailing cables has been theoretically designed and analyzed using a computer. A single spring-loaded take-up sheave stores or gives up cable to maintain tension within specified limits. Controls have been incorporated to shut down the vehicle before all cable is removed from the reel and to de-energize the cable in the event of a reel/cable jam. Full-scale hardware configuration drawings sufficient for manufacture of a test system have been completed.

Jan 1, 1983

By P. L. Swanson

Over a recent 20-month observation period, the U.S. Bureau of Mines obtained seismogram records from a single vertical-component, short-period seismometer installed at the surface of a metal mine in northern Idaho. The seismic events were analyzed for local (Richter) magnitude (M), time of occurrence, location, and relation to rock bursting and production blasting. Approximately 150 seismic events with -0.5 = M = 2.9 were located within the mine, yielding a b value (slope of the logarithm of the number of events with magnitude greater than M versus M) of 0.5. Event locations were constrained using a dense underground array of high-frequency accelerometers. Twenty of the surface-recorded events, with 0.5 = M = 2.9, were associated with rock bursts that produced damage requiring at least 1/2 day of cleanup and/or repair. Other possibly hazardous rock bursts, with magnitudes as small as -1.1, were numerous but were not associated with significant structural damage. Approximately 60 pct of the seismic events with M > -0.5 and 75 pct of damaging rock bursts occurred within 45 min of blasting. Estimates of characteristic rupture dimensions for rock bursts with -1.1 = M = 2.9, based on a conventional dislocation shear-slip model of failure, range from 3 to 300 m.

Jan 1, 2010

By Andrew M. Leszcykowski

A 1981 U.S. Bureau of Mines investigation indicates the Panamint Dunes Wilderness Study Area (WSA) has one active (intermittent) mine,--borrow pit MS 242 owned by the California Department of Transportation (Cal Trans). This mine produces cinders for road base and traction grit. It contains about 900,000 tons of inferred reserves. Examination and sample analyses indicate the Panamint Dunes deposit, covering about 480 acres of the WSA, may have silica resources and the Green Quartz Claim may have copper resources. Carbonate rocks occur in the WSA, but stone resources have not been identified. Adjacent to the WSA, the Big Four Mine contains 35,000 tons of inferred subeconomic zinc-lead-silver resources, and may have additional resources. Sample analyses indicate the Apple 1 Claim, also adjacent to the WSA, may have silver-lead-zinc resources.

Jan 1, 1985

By Thomas E. Finch

This report is an engineering-economic evaluation of alternate methods of handling the parting between two coal seams. It consists of evaluations of parting stowing techniques applicable in a representative, thick seam western United States mine. Methods are examined for their potential implementation, and an estimated operating cost per yard of material moved is developed. The methods are of two categories castback or haulback. Haulback methods use truck haulage except With scrapers, and the castback methods are a direct stowage with no intermediate haulage equipment. Possible equipment combinations include draglines, shovels, hydraulic backhoes, bucket wheel excavators, scrapers, and front end loaders. The purpose of this report is to evaluate the effective competetiveness of the various alternatives.

Jan 1, 1975

By J. P. Morris

The Bureau of Mines investigated the mechanics of fuming of iron-carbon melts during top-blowing with oxygen. Melts weighing 45 lb were prepared in an induction furnace and blown with oxygen by means of water-cooled lances. The rate of fuming was measured and correlated with the operating variables. The data showed that the primary cause of fuming was a boil at the bath surface in the impingement zone of the oxygen jet. Nucleation of the carbon monoxide bubbles producing the boil was apparently brought about by the precipitation of an oxide phase. The actual fuming mechanism involved partial oxidation and vaporization of bubble films and fine metal spray generated by the bursting of the bubbles. Bubbles that formed outside the impingement zone produced little fume. The distribution of trace elements between the metal and fume strongly indicated that the fume contained fine spray particles as well as particles that had condensed from vapor. The rate of fuming was found to be proportional to the carbon content of the metal) the concentration of oxygen in the jet) and the bath temperature) provided that a continuous boil occurred. In the absence of a boil) very little fume was produced.

Jan 1, 1967

By Lon A. Williams

This appendix contains drawing lists and drawings of components and assemblies designed for the prototype portable and machine mounted lighting systems per Tasks II & IV of Contract No. H0220065.

Jan 1, 1976

These proceedings consist of papers presented at two Bureau of Mines Technology Transfer Seminars in early 1980 for the purpose of disseminating recent advances in mining technology related to surface coal mining reclamation.

Jan 1, 1980

By Will H. Coghill, I. L. Feld, G. D. Coe

The object of this paper . is to make known the superior classification accomplished in a hydraulic classifier designed to make use of principles determined by recent research ... The details of the design , the results of preliminary research , and the final testing are given . The classifier of the new design shown in figure 1 and another one like it are in operation as concentration classifiers in a Birmingham iron- ore mill recovering 4 tons per hour of concentrates from table middling that ` otherwise would require regrinding and retabling . The four factors that contribute to the successful operation of these classifiers are ( 1 ) a teeter column of small diameter , ( 2 ) use of an open - bottom tooter column classifier with a periodic pincer instead of the usual type , which terminates in a vortex, ( 3 ) a sorting chamber under separate hydraulic control , and ( 4 ) a teeter column of more than the usual depth . · At the outset it must be stated positively what the authors mean by hydraulic classification : They mean the reconstruction of a multimineral ground product into fractions graded with respect to size , so that cach fraction has the heavy mineral segregated in the fine sizes and the light mineral segregated in the coarse sizes . This definition presupposes that in multiplespigot classification the low specific gravity minerals are carried beyond the first cells to the later ones . The reader must take into account that , from the standpoint of classification , " ores " may be divided into two types , represented - by the following : ( 1 ) Joplin flint - blende ores , which , because of the hardness of the flint and the softness of the blonde , yield upon comminution a product that already has the essence of classification ; and ( 2 ) Birmingham Big Seam iron oros , which contain " easily shelled - out " sca sand and , upon reduction to about 10 mesh , yield a heterogeneous mixture in which the size analyses of the respective " floats " and " sinks " arc almost identical .

Dec 1, 1945

By Charles L. Kimbell

In 1988, the aggregate value of total world international export trade in mineral commodities was estimated at nearly $542 billion in current (1988) dollars, which was about 8.6% above the 1987 level, but still 23.7% below the record high set in 1980. Comparable comprehensive data for 1989 were not available in time for inclusion in this chapter, but 1989 returns for developed market economy countries only were 1 1.8% above those for 1988. These countries accounted for about 50% of the total mineral commodity export trade in 1988. It would be unsound to utilize the overall 11.8% growth rate for mineral commodity export trade for these countries to extrapolate the growth in total world mineral commodity trade because these developed market economy countries account for substantially different shares of the five major mineral commodity groups listed in table 2. Specifically, developed market economy countries in 1988 accounted for 56% of world export of ore, concentrate, and scrap, 74.7% of world exports of iron and steel, 71.7% of world exports of nonferrous metals, and 57.8% of all exports of crude nonmetals, but only 26.6% of world exports of mineral fuels. Moreover, even within each of these groups, the actual product mix included in developed market economy country aggregates differ from that in developing market economy country aggregates and in centrally planned economy country aggregates. Nonetheless, an increase of 9% to 12% in the value of world mineral commodity export trade seems indicated by available returns.

Jan 1, 1992

By M. J. Sapko

A moderately scaled apparatus was developed by the Bureau of Mines to determine the fire resistance characteristics of mine conveyor belts and similar type materials. The design of the apparatus was based upon data obtained in full-scale fire tests and features a radiant panel to preheat the belt and a methane-oxygen ribbon burner to ignite the sample under ventilating condi¬tions in a rectangular duct. The test method overcomes the limitations of existing laboratory-scale methods and provides a measure of both ignitability and flammability in quantitative terms. Flame propagation depended upon such variables as air velocity, ignitor heat flux, and belt width and height in the test chamber. Data are presented for nine belt materials and fire resistance ratings are proposed in terms of the flame spread rate, heat release rate, and the critical ignitor heat flux. The ratings discriminate between the fire hazard posed by different fire-resistant belts and tend to be in reasonable agreement with those obtained in full-scale fire tests.

Jan 1, 1981

By P. M. Ambrose, A. C. FtELDNER

This , the twelfth annual report of research and technologic work conducted by the Bureau of Mines on coal and coal products , summarizes the research and tests conducted frah July 1, 1946, to July 1, 1947. The organic act of Congress establishing the Bureau of Mines authorized tech- nologic investigations of all phases of mining, preparation, treatment, and utilization. These investigations cover eight main fields of activ-. projects varies from time to time. The on ity. The emphase-half of the coal reservos of the world. United States These reserves are not always of the quality desired or in the place where they could best be used. It is necessary to continue research in order that increased output, greater recovery, and better quality can be main- tained under safe mining conditions. Coal comprises 98 percent of the known fuel reserves of the United States and ad eventually must take over much of the requirements now supplied by petroleum and natural gas.. The purpose of this report is to bring to the reader a resume of the work of the fiscal year. The material presented herein is based largely upon publications. In a few instances the results of research that would not otherwise be available in the immediate future are presented. For details concerning the research, it is suggested that the readers consult the publications given in the footnote references." Collected references to all Bureau of Mines publications on coal are published in a series of bibliographies. Technical Paper 576 covers 1910 to 1935; Technical Paper 639 covers 1935 to 1940; and Technical Paper 698, issued in 1947; covers' 1940 to 1945.

Jan 1, 1948

By Chas. F. Jackson

This circular is an abstract of a manuscript-completed in August 1932, which cannot be published in its entirety due to lack of printing funds. It was originally planned to publish the manuscript as one of a series of bulletins dealing with the mining and milling of ores of the principal metals. Because of the common association of lead and zinc minerals in many ore deposits, and because a considerable proportion of the zinc produced in this country is obtained as a by-product of lead mining or vice versa, it seemed necessary to treat the mining and milling of lead and zinc ores in the same volume.

Jan 1, 1934

By Richard H. Bares

This report describes the purpose and application of seventeen statistical and mathematical procedures used in a series of studies made in the project ?A Systems Approach to the Reclamation of Strip-Mined Areas in North Dakota". The objective is to help readers better understand the utility of these procedures.

Jan 1, 1982

By L. D. Patts, J. D. Noll, S. E. Mischler, G. H. Schnakenberg

In this study, we evaluated the ambient diesel particulate matter (DPM) concentrations (at the intakes and exhausts of the mine) as the entire vehicle fleet of a stone mine switched from using 35% biodiesel to using a water emulsified fuel (PuriNOx). Elemental carbon (EC) was reduced by 45% when a PuriNOx blend containing 10% water replaced 35% biodiesel and by 57% when a PuriNOx blend containing 20% water was used. Other factors such as engine duty cycle and production changes could potentially cause some day-to-day EC fluctuations, and no direct comparison to commonly used dieselfuels (No. 1 or No. 2) was achieved. Therefore, a second study was performed in a controlled “isolatedzone” environment to fametal mine, comparing PuriNOxto No.1 diesel fuel in a load haul dump vehicle. The EC fraction of the DPM was reduced by about 71% when the PuriNOx blend containing 10% water was used and by about 85% when the PuriNOx blend containing 20% water was employed. This study did not determine how the water emulsified fuel would affect the engine or power.

By Nan C. Jensen, Oliver Bowles

Stone , the foundation of the continents and the floor of the oceans , is one of the most substantial and enduring of all substances that constitute the material universe . Stone furnished rude shelter for aboriginal man , and through all succeeding ages it has provided a lasting and serviceable structural material . Limestone is one of the most widely used building stones .

Oct 1, 1947

By H. B. Carroll

The performance of commercially available portable instrumentation for detecting nitrogen dioxide, sulfur dioxide, and hydrogen sulfide was evaluated. Length-of-stain detector tubes from several manufacturers were included in the study. The instruments were evaluated in atmospheres with 50-and 80-percent relative humidities at 75° F and containing test gas concentrations of 0.1, 0.25, 0.50, 1.0, 1.5, and 2.0 times the threshold limit values. The results from the gas analyzers were correlated with the known contaminant concentration by calculating and plotting an estimated line of regression, confidence limits, and correlation coefficient for each detector system. An increase in the relative humidity from 50 to 80 percent at /5° F changed the instrument response to the contaminants. The uncertainties in detection precision reported are for the observer-instrument system. The main difference or inconsistency in toxic gas concentrations determined with length-of-stain tubes resulted from the observer's interpretation of the results rather than from a predominant difference in the tubes.

Jan 1, 1975

By William C. Hood

A leaching column technique that produces effluent similar in quality to coal mine drainage in the Eastern Interior Basin has been developed. The columns are charged with 1000 grams of crushed overburden and cycled through the leaching process once a week for twelve weeks. Inter-relationships among the important chemical constituents are very similar to those present in actual mine drainage waters, but the overall concentrations of ion are more dilute in the leachates. Multiplying the leachate concentrations by a factor of 4.5 gives values similar to mine waters. Available data suggests that each of the leaching cycles represents about three years of natural weathering, so that the leaching technique can predict the evolution of the mire drainage water over a time span of nearly 40 years. Use of the leaching technique with drill core samples should provide a method of approximating mine drainage quality in advance of mining and should be quite useful in identifying potentially toxic units in the overburden. However, the results should he considered to be a 'worst case' situation because the technique' does not consider the effects of reclamation.

Jan 1, 1984