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By Sean Gallagher, Gene Wilson, Christopher Mark, Craig S. Compton, Gregory M. Molinda

Falls of small pieces of rock from between roof bolts continue to cause fatalities and to injure hundreds of coal miners each year. Roof screen is the most effective way to prevent these incidents, but some mines are reluctant to use it because they believe installing screen can be awkward, expensive and time-consuming. The most common type of roof bolting machine used in mines today is the dual boom, outside-controlled roof bolter. Mines who install roof screen using these machines have developed some machine modifications and techniques to ease roof screen installation. This paper describes some successful techniques and machine modifications that are being used in productive mines to assist with roof screen installation. Since the material handling involved with roof screen installation can expose miners to an increased risk of musculoskeletal injuries, the National Institute for Occupational Safety and Health (NIOSH) ergonomists, designed machine modifications and implemented a series of tests to evaluate roof screen handling procedures for outside-controlled, dual boom roof bolting machines. Roof screen installation can also have a positive economic impact on a mine by reducing the cost of injuries, workers’ compensation, required spot or re-bolting, and clean-up of long term travel and belt entries.

By C. Melvin Lepper

The Bureau of Mines has developed an improved earth resistivity field system which employs a novel technique for obtaining null measurements. The instrument is designed to operate reliably in high-noise environments such as those found in the vicinity of operating mines. The system consists of a low-frequency transmitter, a sensitive receiver and an external battery pack, each in its own case to provide protection from the elements. The receiver and transmitter units have self-contained recharge-able batteries to supply power to the circuitry and separate built-in battery chargers that operate on standard 115 Vac power. The system is portable and simple to operate. Measurement accuracy, reliability, and dynamic range are superior to most commercially available equipment even though less time and effort is required to make null readings. Unlike some commercial systems, long integration times are not required to enhance signal-to-noise ratio in areas of high background noise.

Jan 1, 1974

To provide a faster means to open and close permissible electrical enclosures. Approach: An inspection and repair port with a multiple start thread which provides a permissible joint has been developed and tested. How It Works: The inspection port screw thread has a large pitch, which allows the port cover to be rotated from fully closed 10 fully open, in less than one revolution. See Figure 1. When the cover is screwed back in. it be-gins engagement within one eighth turn because the screw design has eight separate threads. To prevent Its unauthorized opening, the port cover has a bolt guarded by ears which accept a padlock. The threads are designed to tolerate a reasonable amount of grit without binding, although wipe-off cleanness is necessary during reassembly. Enclosures of two different sizes each fitted with the quick-access port, were

Jan 1, 1976

By Thomas C. Atchison

The experimental work described in this report is part of a continuing study by the Federal Bureau of Mines of the fundamental physical processes involved in breaking rock with explosives. Six explosives were tested for their strain-producing abilities in a dolomitic marble. The explosives selected for testing had a tenfold variation in detonation pressure and a fivefold variation in characteristic impedance (product of loading density and rate of detonation). Strain pulses produced by the detonation of small charges of the explosives were recorded at distances of 5 to 130 feet. Peak strain, ?, was found to decrease with distance, R, in accordance with an exponential propagation law previously determined for other rock types, namely ? = (K/R)e ?aR The absorption constant, a, did not vary significantly with the explosive and was of the same order of magnitude as that for other rock types. The different explosives produced a fivefold variation in the value of the intercept constant, K.

Jan 1, 1961

By Y. Miron

Previous studies at the Bureau of Mines outlined the hazards of ammonium nitrate-fuel oil (AN-FO) mixtures in the presence of pyrite-bearing ores. The recent trend in the mining industry to strengthen AN-FO by the addition of aluminum metal raised the question regarding the effect of aluminum in AN-FO in the presence of pyrite-bearing ore. Laboratory work, similar to that done previously, demonstrated that the temperature of a self-sustaining reaction in the presence of AN-FO ore-aluminum is not lower than that for a comparable AN-FO-ore mixture. However, as might be expected from known thermochemical data, once initiated, the resulting reactions between AN-FO, aluminum, and pyrite are much more vigorous than those observed for AN-FO and pyrites alone. The temperature required to produce a self-sustained reaction for the combinations tested in this study is 250°±20° F while in the previous Bureau study, reactions were noted, in some instances, at 150° F. The different pyritic ores may be the cause of this variation.

Jan 1, 1976

By George A. Morgan

Output of minerals was insignificant in 1981 and made a negligible contribution to the gross national product (GNP), estimated at $1.2 billion.2 Agriculture accounted for 40% of CNP and manufacturing accounted for 10%. The chief source of income was indirect taxes levied on traffic through the Port of Cotonou, an entrepôt. Trade statistics for Benin were incomplete and dated. Major trading partners were France and other members of the European Communities. Benin was a member of the West African Monetary Union and as such must coordinate its foreign currency, reserves, interest rate structure, and fund transfer with other member countries. Its currency, the Communauté Financière Africaine franc (CFAF), was fixed to the French franc.

Jan 1, 1983

By Joseph M. Kurtak

The U.S Bureau of Mines conducted a five-year mineral resource assessment of the 16.6 million acre Colville Mining District in northern Alaska, which includes part of the National Petroleum Reserve in Alaska. The study was initiated at the request of the Bureau of Land Management, which administers the majority of the region. The study was done in cooperation with the Alaskan Division of Geological and Geophysical Surveys, the U. S. Geological Survey, and the University of Alaska. During fieldwork, 1593 rock, soil, and stream sediment samples were collected and four bulk samples taken for beneficiation studies. A total of 40 mineral occurrences were documented, including 27 which were previously undescribed. No mining has occurred within the district. Mississippian carbonaceous shale and siliceous mudstone contain stratiform exhalative lead-zinc-silver occurrences. Grades average 8.0% combined lead/zinc and 51 gm/mt silver. Upper Devonian to Lower Mississippian sandstones host breccia veins, containing up to 29% combined lead/zinc and 274 gm/mt silver. Mineralized quartzites of similar age have potential for disseminated-type lead-zinc deposits. Samples from Lower Cretaceous mudstone and shale beds up to 6.5 meters thick, contain as much up to 12% manganese. Upper Mississippian carbonaceous shale and limestone beds contain up to 23% phosphate. Stratiform barite deposits hosted by cherts, are up to 27 meters thick with an average specific gravity of 4.16. Vein-type fluorite occurrences are associated with Mississippian limestone. Moderate potential exists for development of zinc -lead-silver, barite, and phosphate deposits.

Jan 1, 2011

By E. B. Nelson, B. W. Gandrud, B. M. Bird

"The Lewisburg No. 2 mine of the Sloss-Sheffield Steel & Iron Company is located in Jefferson County, Alabama, about 7 miles due north of Birmingham. At this point the coal from the Mary Lee seam when coked in by-product ovens yields an excellent quality of metallurgical coke suitable for use in the iron blast furnace; it is also an excellent steam coal. In mining, all three benches are worked. Coarse impurities are largely gobbed by the miners underground.In addition to giving the data obtained from screen-sizing and float-and-sink tests of a representative sample of the raw coal, this report presents the results of slotted-screen tests to show the proportions of flaky particles in selected sizes, and the results of tests to show how much coal is liberated from impurities by crushing the coarsest sizes. These data have been obtained in connection with an extensive study of coal-washing now being conducted by the U. S. Bureau of Mines and the University of Alabama, with U. cooperation of the different operators of Alabama. As the work progresses other reports will follow containing furtner data on the washability both of the Mary Lee seam and of other seams in Alabama and giving the results obtained in preparing these coals by various methods.Although a great amount of investigative work on the preparation of the Mary Lee scam was previously carried on by the various coal companies of the district, comparatively little of this information has been published. In governmental publications three references have been found. Forbes5 gives a number of sections with proximate and ultimate analyses of face samples taken in the mines. Gandrud and Britton'' show sections of this seam at Flat Creek and New Castle; they also give the specific gravity and ash contents of the partings of coal and impurities. In their paper Yancey and Fraser7 include washability studies and washing data from the Sayreton mine of the Republic Iron & Steel Co."

Jun 1, 1930

By James J. Dowd

The investigation to evaluate the reserves of coking coal in the United States suitable for the manufacture of metallurgical coke is being made by the Bureau of Mines in three parts: (1) To estimate known (measured plus indicated) recoverable reserves of all coking coals; (2) to upgrade marginal coals through effective preparation; and (3) to study the carbonizing properties of coals and coal blends not now widely used for metallurgical coke making. This is the fourth of a series of reports giving the results of studies by counties under phase (1) of the investigation. It covers Armstrong County, Pa., which comprises parts of the Foxburg, Clarion, Brookville, Kittanning, Bural Valley, Smicksburg, Freeport, Elders Ridge, and Indiana quadrangles. (See fig. 1.) A base map for each bed in each quadrangle was made to the scale of 1 inch equals 1,200 feet. Maps of mines, locations of drill holes, bed and total coal thicknesses, and the outcrop of the bed were plotted on the maps. With all available data plotted, isopach lines were drawn to limit areas of known unmined reserves in beds 0 to 14 inches thick, 14 to 28 inches thick, 28 to 42 inches thick, and more than 42 inches thick. These areas of coal reserves also were divided into "measured" and "indicated" categories. All areas in each thickness range and in each category, mined-out areas, areas excluded from the estimate, and areas outside the outcrop were measured by planimeter on the base maps, Estimates of total reserves 14 inches and more thick and maps for individual beds were prepared from these data.

Jan 1, 1951

By Daniel Ng

The U.S. Bureau of Mines-Michigan Technological University mine ventilation mainframe program was successfully adapted for execution in a personal computer (PC). The hardware requirement can be as modest as 256 kilobytes (33) of random access memory (RM) and two floppy disk drives. A version compiled for a PC possessing 512 Kb RAM has arrays dimensioned to accommodate 512 separate mine airways and junctions, and it contains all the features and capabilities of the original version. It has successfully analyzed all the ventilation networks tested, including a very large commercial mine (404 airways, 237 junctions, and 5 fans). In all cases the PC version produced practically identical results as obtained from the mainframe computer. In all respects, the PC version performed the same as the mainframe version with the exception of execution speed When a numerical coprocessor is employed, execution time can be reduced by more than 50%.

Jan 1, 1989

By W. R. Hardwick

This information circular describes open-pit mining methods and practices of the Bagdad Copper Corp., Yavapai County, Ariz. It is one of a series being prepared by the Federal Bureau of Mines on mining methods, practices, and costs in various mining districts of the United States. A brief history of the Eureka district and of early developments at the [gdad] mine is given, and the are deposit is described with particular emphasis on those characteristics (physical, economic, or engineering) that affected the choice of mining methods. Prospecting, exploration, and sampling and estimating the tonnage and grade are outlined. Development of the open-pit mine is shown. Mining methods, including breaking ground, primary drilling and blasting, secondary drilling and blasting, loading, transportation, engineering, and operating control, are described. A brief summary of mining equipment is given. Percentage of extraction, production rate, mine drainage and water supply, wage, contract, and bonus systems, safety and fire prevention, and the processing plant also are described. The last section gives a breakdown of such costs as are available for publication.

Jan 1, 1959

By W. J. Kroll

This report on the bibliography of zirconium has been confined to those publications and patents that appear to be useful in the commercial development of the metal, both the malleable and the nonmalleable. The methods of production have been stressed and special attention has been given to the alloys. Compounds of importance, like the oxide and chloride, for the manufacture of the metal or of the alloys have been considered. The use of the oxide in refractories anal in the glass and porcelain industries has been omitted. The present survey is critical; that is to say, an attempt has been made to evaluate the effectiveness of suggestions made in the literature. The exhaustive work of Marden and Richy, Bureau of Mines Bulletin 186, published in 1921, has been taken as a base to start from with the intention of bringing the subject up to date with material published in the last 24 years. During this time there was considerable 'advance in the preparation of the metal and Its alloys, and in the development of new uses. On the other hand, there was little progress in the methods of decomposing the ores, so that the chapter on this latter phase is necessarily short.

Jan 1, 1946

Significantly increase the amount of fresh air that sweeps the face in front of a continuous mining ma-chine, in order to prevent methane gas buildup. Approach Water sprays are mounted along the sides of a continuous miner and behind the cutter head to help push ventilating air along the required path, and prevent its short circuiting. How It Works A continuous miner is fitted with two sets of water sprays, one of which is used at a time. The set of sprays shown in the diagram, helps move the ventilating air forward along the left side of the miner and across the cutter drum from left to right. That air is then drawn into the exhaust air passageway located along

Jan 1, 1978

By J. Dean Warner

Alaska contains many critical and strategic minerals that are scarce in the conterminous United States. Among these are tin, tantalum, and columbium. This Bureau of Mines report summarizes available data on the production, reserves, and occurrences of these minerals in Alaska. Alaska produces about 200,000 lb of tin per year, with historical production since 1901 estimated to have totaled 5,830,600 lb. Measured, indicated, and inferred tin reserves total over 140,000,000 Ib. Much of the tin production has been from the placer mines of the western Seward Peninsula; however, most of the reserves are in that area's lode deposits. Alaskan tin occurrences are part of a belt of tin mineralization that extends along the western coast of North and South America. The Alaskan portion of this "tin belt" comprises placer occurrences and lode occurrences of five major types: greisen, vein, skarn, pegmatite, and volcanogenic massive sulfide. Greisen and vein occurrences are the most abundant, but skarn deposits have historically been the most economically important. Columbium and tantalum have not been produced in Alaska; however, they may be recoverable as byproducts of tin, tungsten, gold, or uranium mining. Approximately 135,000 Ib of columbium oxide (Cb205) are inferred within the Tofty placer deposits in the Manley Hot Springs district.

Jan 1, 1985

By C. M. Palencia

The Bureau of Mines evaluated the potential availability of molybdenum resources from 88 mines and deposits that account for more than 90 pct of the demonstrated resource base in market economy countries (MEC's). For each property, tonnage-cost relationships were developed that indicate the molybdenum potentially available at different average production costs, including a 15-pct rate of return on invested capital. From the 23 MEC primary deposits, 2.5 billion 1b Mo was determined to be potentially available at a price of $411b, rising to 4.7 billion 1b Mo at $8/lb. Copper price-molybdenum tonnage relationships were developed for those mines and deposits from which molybdenum can be recovered as a byproduct of copper production. This analysis showed that another 3.4 billion lb Mo is potentially available based on a copper price of $0.7511b, rising to 4.3 billion lb Mo at $l.00/lb. The United States has been the world's largest molybdenum supplier since 1924. Its remaining resources are sufficient to meet the domestic demand of 57 million lb/yr Mo (averaged for a 10-yr period) through the end of the century. Production from primary domestic mines was suspended during most of 1983 because of oversupply of materials. A major concern is the cheap molybdenum byproducts from foreign copper operations in which employment and the need for hard currency override economics in meeting production goals.

Jan 1, 1985

By Donald O. Capstick

The U.S. Bureau of Mines conducted an inventory of the prospects and mineral resources in the Scodies RARE II area (No. 5212) in 1982. No mineral production is recorded from the area, and no mines are being developed. The Scodies RARE II area is comprised primarily of light colored granodiorite with minor inclusions of mafic granitic rocks. Late stage differentiates of magmas resulted in quartz veins and pods. Metasedimentary rocks which have been mineralized in some parts of the Sierra Nevada were not observed within the study area during this investigation but small inclusions have been reported.

Jan 1, 1983

Reduce the danger to personnel and destruction of equipment caused by fires on surface coal augers. Approach: A reasonably priced reliable system which automatically senses a fire and activates dry chemical extinguishers, has been built and field tested. How It Works: Heat sensors mounted in the engine compartment and hydraulic hose areas detect the fire, usually before the operator does. This causes the system to automatically discharge A-B-C class dry chemical extinguisher through a fixed piping system.

Jan 1, 1976

By K. Zipf, Z. T. Bieniawski

"An extensive mixed-mode fracture toughness testing programme was conducted on coal from three coal fields. A special mixed-mode testing fixture for coal and other geologic materials was developed together with reliable specimen preparation procedures. Dynamic modulus measurements made on each of the 116 fracture toughness specimens showed that these coals exhibit certain degrees of anisotropy. The fracture toughness testing programme systematically varied the loading rate, specimen orientation and fracture loading mode. Loading rate did not significantly effect the fracture toughness over the quasi-static range tested. Orientation did have a significant effect on measured fracture toughness. In the coals tested, the divider orientation and arrester orientation had higher fracture toughness than the short transverse orientation. Data showed that one orientation could have almost twice the fracture toughness as another. The fracture toughness testing enabled certain evaluations of three mixed-mode fracture theories: maximum tangential stress, maximum energy release rate and strain energy density theory. Due to the extreme heterogeneity of the coals tested, definitive conclusions regarding the best mixed-mode fracture theory are not possible; however, data do tend to support the strain energy density theory. INTRODUCTIONThe major aim of this research is to ·develop a fundamental understanding of how fine· fragments of coal (respirable dust) are generated during a fracture process. In a related paper [l], a hypothesis was presented for the mechanism of fine fragment formation during a generic coal material/cutting tool interaction. In this hypothesis, fine fragments are created during coal material/cutting tool interactions that are best described as general mixed-mode fracture processes. Data are required on the mixed-mode fracture behaviour of coal, the physical character of the newly-created fracture surfaces and the character of the inherent flaw structure of the coal material. Accordingly, a test programme was designed that provided some information in each of these areas. The testing effort seeks to measure critical fracture toughness under mixed-mode loadings as a material parameter characterizing in part the tendency of various coals to generate undesirable quantities of fines and respirable dust."

Jan 1, 1990

By J. B. Janus

This report, the 25th in a series, lists analytical data of coal samples collected by the Bureau of Mines in connection with the purchase of several million tons of coal for various Government agencies during fiscal year 1975. Tipple samples were collected by Bureau of Mines engineers at tipples as coal was being loaded into railroad cars or trucks. Ultimate analyses are given for these coalbeds only. The delivered coal was sampled at destination in accordance with instructions furnished by the Bureau of Mines, and all samples were analyzed in the Bureau laboratory at Pittsburgh.

Jan 1, 1976

By G. L. Bartlett

"INTRODUCTION The major objective of our research is to help reduce the incidence and severity of coal worker's pneumoconiosis (CWP). To that end, this project is designed to improve our understanding of the processes that lead to pulmonary dysfunction following mine dust exposure, and how those processes might be interrupted or attenuated. The response of the lung ' to inhaled particles is complex, and the course of development of disabling CWP is slow and unpredictable. From among the numerous cellular and molecular interactions involved in the pulmonary response to inhaled particles, this project is focussed on the role that the pulmonary alveolar macrophage (PAM) may play in regulating the activity of fibroblasts.The PAM is the lung cell that has the most immediate and the most obvious interaction with inhaled particles. Within a short period after particles are arrested in the alveolus of the lung, they are phagocytized (engulfed) by these specialized cells. The PAM then has a diverse potential repertoire of subsequent activities. Which reaction actually ensues is determined, in large part, by the nature of the phagocytized _particles. Activated PAMs produce a variety of products that may affect adjacent lung tissue, including superoxide free radical, elastase, collagenase, prostaglandins, platelet activating factor, etc. Those may well be important in the pathogenesis of CWP, but they are beyond the scope of this project. Background information that is cogent to this project has come primarily from investigations using animal models of silicosis and asbestosis. PAMs that have ingested silica particles synthesize and release molecules that control the behavior of surrounding cells. One such mediator is interleukin-1 (IL-1), a molecule that plays a central role in many aspects of the response to injury. It can stimulate fibroblasts (the cells that help to hold tissues together) to release the enzyme collagenase, resulting in breakdown of the structural collagen fibers that support the lung tissue. IL-1 also stimulates fibroblasts to undergo mitosis and to proliferate, which is an initial stage of fibrosis. Certain stimulants cause PAMs to release fibroblast growth factors (FGFs) that are distinct- from IL-1. Under other circumstances activated PAMs synthesize and release molecules that stimulate fibroblasts to accelerate synthesis of collagen fibers, thus contributing to fibrosis. Although these observations provide a valuable precedent for analysis of the mechanisms involved in CWP, their relevance to CWP cannot be assumed since most of those studies involved macrophages or fibroblasts obtained from tissues other than the lung, and because almost none of them have used CMD as the stimulating particles. Therefore, the goal of this project is to learn how exposure to CMD affects the behavior of PAMs, and in turn how products of dust-exposed PAMs affect fibroblasts and the process of fibrosis in the lung."

Jan 1, 1988