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By Joseph Cervik, Maurice Deul, Albert Sainato

This Bureau of Mines report deals with water infusion of coalbeds, which can control methane emission at face areas during developmental mining and which may sometimes suppress dust. Studies show that water infused into the coalbed flows through the fracture system and displaces the methane in the fractures and prevents migration from the solid coal. Displaced gas migrates away from the face area that has been water infused and enters the return ventilation airways. A gradual decrease in methane emission is observed from the start of infusion until the infused zone is mined through. Depending on the permeability of the coalbed, infusion pressures ranged from 300 to 2,200 lb/in2. Face emissions in the Upper Kittanning coalbed were reduced by 89 pct; reductions of 38 to 79 pct were measured in the Pittsburgh coalbed depending on the relationship between the face cleat direction and mining direction. Respirable dust levels were reduced by about 75 pct on a longwall section in the Pocahontas No. 3 coalbed and by about 50 pct on a development section in the Upper Kittanning coalbed, but no statistically reliable reduction was found in the respirable dust levels in the Pittsburgh coalbed.

Jan 1, 1977

By J. H. Jansky, P. W. Jeran, G. L. Hassett, M. C. Irani

This Bureau of Mines report tabulates methane emissions from U.S. bituminous coal mines with daily emission rates of at least 100,000 cfd according to States, counties, and coalbeds. Most of the methane emitted is from mines in the Appalachian States. Total daily emissionin 1975 was 216.3 MMcfd, compared with 227.0 MMcfd in 1971 and 214.5 MMcfd in 1973. Thirty counties in nine States had daily methane emissions of 1 MMcfd or more, These emitted 93 percent of the total methane. The highest emissions were from Monongalia County, W. Va,, which accounted for 18.9 percent of the total. This was followed by Marion County, W. Va., 9.6 percent; Buchanan County, Va., 8.5 percent; Jefferson County, Ala., 6.1 percent; and Washington County, Pa., 5.9 percent. The Pittsburgh coalbed emitted 45.7 percent of the total methane, followed by the Pocahontas No. 3 coalbed with 12.9 percent. The report lists 196 mines, of which 60 had daily methane emissions of 1 MMcfd or more. Included in this compilation are the identification and thickness of the coalbed, methane emission, coal production and ventilation rates, number of drifts, shafts, and slopes used for ventilation purposes, shaft depth, age of mine, and gas-to-coal ratio.

Jan 1, 1975

By John L. Hill

"The Bureau of Mines is conducting research on the causes and methods for control of cutter roof failure in underground coal mines. This hazardous ground control problem exposes miners to the danger of falling roof rock and frequently results in massive roof failure. This report outlines the probable causes of cutter roof failure, which are proposed based on field investigations, numerical model analysis, and in-mine observations. Traditional methods of control are presented, as well as innovative methods based on mining concepts developed during earlier years of coal mining history. The report can be useful to a mine operator for assessing the causes of cutter roof failure on a site-by-site basis and for predicting the probability of its occurrence. A process is presented for selecting an optimum control method that includes both traditional and innovative control techniques for each of the various causes of cutter roof failure. INTRODUCTIONGround control research conducted by the Bureau of Mines is designed to develop technology that will aid in reducing the frequency of accidents associated with poor ground control conditions. Cutter roof failure often poses a safety hazard to miners and causes delays in production while massive roof falls are cleaned up and unstable roof is resupported. Implementation of control measures reduces the threat of injury to miners and prevents production delays.The definition of cutter roof failure used in this report separates this unique type of failure from other ground control problems, to aid in the analysis of the causes and in the development of control methods. The definition is as follows:Cutter roof failure in mine roof rock is a failure process that initially begins as a fracture plane in the roof rock parallel to, and located at, the roof-rib intersection. The fracture propagates upward into the roof over the mine opening at an angle usually steeper than 60° from the horizontal.The mappable extent of cutter failure may range in length from only a few feet to several hundred feet and may traverse entry-crosscut intersections without change in direction. Once initiated along the roof-rib line, a cutter may propagate away from the roof-rib line of one side of a room, cross the roof span, and continue along the other side of the room. It is important to note that this definition excludes a similar type of failure (sometimes referred to as ""kink roof') that has comparable characteristics but occurs in the center of the entry. (The reasons for this distinction are discussed in the ""Background"" section.) Researchers refer to the cutter failure discussed in this report as ""classic"" cutter roof failure; except for short deviations across intersections and entries, initial failure is confined to the roof-rib intersection."

Jan 1, 1986

By Donald P. Blasko

The Bureau of Mines investigated two areas of the Alaska Peninsula (Iniskin Peninsula and Becharof Lake) where oil and gas seeps were known to occur in an attempt to determine (1) whether the seeps are still active and (2) the amount of bitumen contained in the drainage leaving the seeps. The oil, water, oil-water, and gas were sampled and analyzed. Five oil samples were taken at four separate oil seeps. The API gravity of the oil ranged from 8.90 to 21.4° and the sulfur content was from 0.12 percent to 0.59 percent. Four of the seven gas samples obtained revealed fair high caloric values, ranging from 746 to 924 Btu/cu ft, and averaging 844 Btu/cu ft. A total of 44 water samples were obtained. Bitumen content of the water was as high as 9,773 mg/l at one seep, but averaged less than I mg/l where the seep-drainage water entered the Gulf of Alaska.

Jan 1, 1976

By E. D. Gardner

About five minutes after 3 o'clock on Thanksgiving morning, November 24, 1927, smoke was discovered coming up No. 2 shaft of the Magma Copper Co.'s mine at Superior, Pinal County, Arizona. Of the 49 men in the mine at the time, 42 were able to make their way to the outside unassisted, but 7 perished. Six bodies were recovered, and the seventh, that of an Apache Indian cage-tender at No. 2 shaft, is thought to be in the caved section between the 1,600 and 2,250 foot levels A second and independent fire broke, out in No. 1 shift about 2 a.m., November 27, burning .out the shaft timbers from the surface to the 200-foot level and destroying the surface fan and structures. About 20 men were underground fighting the fire in No. 2 shaft, but all were safely withdrawn, aril the fire in No. 1 haft was quickly controlled.

Jan 1, 1928

By N. B. Greninger

The U.S. Bureau of Mines conducted explosion tests on various full-scale cementitious bulkheads used in abandoned mine areas to evaluate the ability of the bulkheads to withstand gas explosion over-pressures of 20 psig. Tests were performed on 120-ft2 solid-concrete-block seals of varying thicknesses and designs. Of the seven solid-concrete-block seals tested, only the standard-type seal, having a 16-in thickness, keyed at the floor and ribs, all joints mortared, wedged at the roof, and a center pilaster, maintained its integrity when subjected to a 20-psig pressure wave. After being subjected to repeated explosions, the standard seal only showed a small hairline crack and had an air leakage of 87 ft3/min at a pressure differential of 1 in H2O. Tests were performed on cementitious foam seals of varying thicknesses and compressive strengths. Explosion tests have shown that 200-psi strength, 4-and 8-ft-thick seals can withstand a 20-psig pressure wave. At a pressure differential of 1 in H20, no air leakage was detected through the 200-psi, 8-ft-thick foam seal.

Jan 1, 2010

By Edward F. Divers

A new nonclogging water spray system for continuous-mining machines has been developed under contract with the Bureau of Mines. This paper presents installation and operating guidelines for the system, which consists of improved and easily maintained machine-mounted hardware, including an inline Y-strainer, a hydrocyclone, a backup filter, and two quick-opening valves for flushing particulates from the strainer and hydrocyclone. Underground tests with continuous-mining machines have shown that when properly installed and maintained, the new sys tern virtually eliminates nozzle clogging and thus greatly reduces spray maintenance. The sys tern is relatively inexpensive and has been installed on typical continuous-mining machines for a total cost under $1,000.

Jan 1, 1976

By A. W. Maynard

Simple chemical spot tests for the identification of major alloying elements in aluminum-base alloys are described. The tests are suitable for use by nontechnical personnel working outside a laboratory. Tests for zinc, copper, manganese, and magnesium employ electrographic sampling methods and sample papers. Use of electrographic sampling in a test for magnesium in aluminum is made possible by using glass fiber filter paper. Differentiations between magnesium and magnesium-silicon alloys of aluminum and between aluminum-base and magnesium-base alloys are made by direct chemical solution tests. Description of a device for obtaining reliable electrographic samples is included. A sequence of testing for identification by alloy groups is given.

Jan 1, 1971

By Jeffery M. Listak, Ernest A. Curth

"It took only 9 years from the first appearance of roof shields on the U.S. longwall mining scene to the present predominance of shield faces. An apparent consequence is the welcome downward trend in accidents related to failures in longwall ground control. The report addresses load prediction, the effects of shield geometry on support loads, factors contributing to ground control, and related techniques. The Bureau of Mines took an active part in the evolution of longwall mining, including developing one of the first shield faces in 1975, the first lemniscatetype shields in 1976, the Mine Roof Simulator completed in 1980, the first shields in steeply pitching coalbeds in 1981, and the first multilift working of a thick coalbed in 1982. The information offered in this state-of-the-art report will assist in establishing criteria for roof support selection. INTRODUCTIONIn terms of roof support technology, the introduction of shields in the seventies and eighties was a major step forward. Table 1 indicates the predominance of shield faces on the U.S. longwall mining scene and its apparent consequence, a welcome downward trend of ground-control related accidents.The rapid progress of longwall technology began in 1975 and is highlighted by a development leading from the caliper shield to the modern lemniscate type. Shields have been gaining preference over chocks since their advent to longwall mining in 1975. Safety and productivity factors favoring shields over chocks are--1. A sheltered working space requiring minimum cleanup work.2. Structural stability that allows advancing without delay even with brushing roof contact and, by controlling all lateral loads, removing the requirement for cumbersome leg restraint and restoration devices.3. Wide hydraulic range of mining height.The development of roof shields in the Federal Republic of Germany preceded and paralleled their rapid adoption by U.S. miners. In 1983, 87 pct of the total production in Germany came from shield faces (1).2 In Great Britain, the National Coal Board introduced the first shield support system in 1977 to initiate Advanced Mining Technology (ATM) and Heavy Duty Mechanization (HDM) programs; as of mid-1982, 44 shield faces were operating, or 7.5 pct of a total of 581 faces CJ_)."

Jan 1, 1985

By Nicholas Kyriazi, John P. Shubilla

The National Institute for Occupational Safety and Health, National Personal Protective Technology Laboratory, has undertaken a study to determine how well self-contained self-rescuers (SCSRs), deployed in accordance with Federal regulations (30 CFR 75.1714), hold up in the underground environment with regard to both physical damage and aging. This report presents findings regarding laboratory-tested SCSRs in the seventh phase of testing from May 1999 to August 2000. The SCSRs were tested on human subjects and on a breathing and metabolic simulator. The results indicate that most of the apparatus, if they pass their approved inspection criteria, perform satisfactorily. The deployed CSE SR-100s, however, exhibited significantly higher inhaled carbon dioxide (CO2) levels than new units, as they did in the previous two phases. Several Draeger OXY K-Pluses that rattled when shaken were found to have potassium superoxide (KO2) particles throughout the breathing circuit, including the mouthpiece. Draeger investigated the problem and developed a shake test to detect damaged units. The durations of new Ocenco M-20s were statistically significantly longer than those of deployed units, although only by 2 min.

Jan 3, 2002

By R. O. Kneisley

Rock mechanics measurements indicate that the present two-bed mine design used at the Big Island trona mine, Green River, Wyo., results in stable workings. Vertical pressure changes in the lower panel pillars and horizontal pressure changes in the lower bed roof and floor indicated negligible upper bed mining influence. Pillar stresses stabilized soon after upper bed mining was completed. Strata movements in the pillar ribs, roof, and floor were also negligible and stabilized soon after completion of upper bed mining. Using tributary area theory, the confined core approach, and studies of model trona pillars it is shown that increased extraction ratio is possible. A program of gradually increased extraction ratio accompanied by simple measurements should result in a mine design that includes both higher recovery and long-term stability.

Jan 1, 1981

By M. M. Fine

A satisfactory mean: of beneficiating a Brazilian phosphate rock was developed in a mineral-dressing-research study by the Bureau of Mines. High-grade concentrates well ever the specified minimum grade of 70 percent tricalcium phosphate, were produced, with goad recoveries by agglomerate tabling and flotation. A lower gads but usable secondary product was recovered by sedimentation of the minus-200-mesh fraction of the ore. The ore wan representative of an extensive deposit recently discovered near Recife in the State of Pernambuco, Brazil, which will be exploited in a plant planned to eventually produce at the rate of 500,000 tons of concentrate annually. Although Brazil has been reported to Lave a substantial reserve of phosphate rock,3/ the country has never been more than a small producer of this commodity. From 1945 to 1950 the highest production of phosphate rock attained in Brazil amounted to 10,421 tons. Production in 1949, the most recent year for which figures are available, was 4,553 tons.4/

Jan 1, 1954

By M. D. Marshall

This handbook is for the engineer or person responsible for the storage and removal of material from bins and silos in the minerals industry. The objective of the handbook is to prevent bin-related accidents by eliminating problems which require workers to enter bins. It provides basic information on handling materials so that knowledgeable decisions can be made on bin design and accessories to minimize flow stoppages. Materials are classified in terms of their flowability, and bin design and accessories suggested for each classification. A method for classifying a material is also given, and the various types of material flow aids reviewed. Safety around bins is the basic theme of the handbook. Federal regulations are reviewed and additional suggestions presented to prevent bin accidents. New equipment for releasing material hang-ups is reviewed.

Jan 1, 1984

By A. J. Barry

[This is the third report related to fundamental retail roof-bolting research in underground mines (1, 2)3/ and describes an investigation of the torque-load relationship for 3/ -inch, expansion-type mine roof bolts. In a previous investigation the relationship between torque and bolt load was established for 1-inch slotted-type bolts (1). The two types of bolts differ in diameter and method of tightening and consequently may exhibit different torque-load behavior. The 1-inch bolt is tightened by turning the nut, the 3/4-inch bolt by rotating the beaded bolt itself. Experience indicates that roof bolts should be tightened to moors satisfactory anchorage sand to minimise nag of tie roof over the mine opening. The generally accepted means for determining the bolt load is to see a torque wrench to measure he torque applied in tightening the bolt and, from a predetermined relationship between torque and molt load, to, determine the corresponding bolt load. Because frictional effects may vary between one type of shell assembly or bolt and others, 7 types of expansion shell units and 3 types of 3/4-inch-diameter, mild steel bolts were tested.]

Jan 1, 1954

By Joseph Cervik

Gas occurs in coalbeds in an adsorbed and a free gas state, Adsorbed gas is stored in the micropore structure and its transport is governed by Fick's law. The free gas occurs in the. fracture system and flows according to Darcy's law. These two modes of mass transport are interdependent. Production decline curves of coal-gas wells are of the constant percentage decline type and, thus, show no indications of flow characteristics peculiar to coal-gas reservoirs. The effectiveness of surface boreholes as a degasification scheme depends upon both good fracture permeability and a high fracture density. Conventional methods of reservoir engineering analysis are not applicable to coalbeds.

Jan 1, 1969

By R. Hogg, T. F. Dumm

"It is generally agreed that dust characteristics play a role in the development of Coal Workers' Pneumoconiosis (CWP). Unfortunately, there is a serious lack of information on what the characteristics of mine dust actually are and how they vary among different mining regions, coal seams, etc. This paucity of data can generally be attributed to the serious problems encountered in collecting sufficiently large quantities of dust for conventional analytical procedures.Personal samplers are widely used in coal mines for regulatory and enforcement purposes. Generally, these provide information only on the total (respirable) dust loading in the mine atmosphere and on the mineral matter (primarily quartz) content of the respirable dust. A procedure has been developed by which samples collected with a slightly modified personal sampler can be analyzed for particle size distribution, total mineral matter content and elemental composition, in addition to the standard mass and quartz measurements. These analyses could readily be performed on a routine basis. Shape analysis by Scanning Electron Microscope (SEM) could easily be included if appropriate shape criteria are established. Extension of the procedure to include the determination of complete size/specific gravity (composition) distributions is quite straightforward provided sufficiently large samples (at least 10 mg) can be collected. Typical sample sizes for a personal sampler carried by a miner for one shift range from about 0.5 to 2 mg.The basic procedure was developed and evaluated using synthetic mine dust prepared in the laboratory. Field tests in three working mines in Pennsylvania and West Virginia have confirmed the applicability of the approach to the real world. Particle size distribution measurements on mine dust collected in the modified personal sampler were found to agree closely with the results of simultaneous in situ measurements obtained using cascade impactors."

Mar 1, 1989

By Herbert R. Appell

Urban refuse, cellulosic wastes, and sewage sludge have been converted to heavy oil by heating under pressure with carbon monoxide and steam. Conversions of the organic matter to oil, water, and gas have averaged near 90 percent at temperatures of 250° to 400° C and pressures of 1,500 to 5,000 psi. The yield of oil, based on the dry organic matter of the waste materials, is usually near 40 percent. This is the equivalent of more than 2 barrels of oil per ton of dry, ash-free waste material. The oil from urban refuse and cellulosic wastes has a sulfur content near 0.1 percent. This low sulfur content makes the oil from refuse a desirable source of fuel oil.

Jan 1, 1970

By Oliver Bowles

Calcareous rocks, of which the principal varieties are marble and lime¬stone, are used extensively for building and ornamental purposes. Onyx and travertine, subdivisions of these groups, are sufficiently distinctive in origin and use to merit separate classification. The purpose of this paper is to define the terms "onyx" and "travertine" and to describe the occurrences and uses of the materials bearing these names. ORIGIN AND CHARACTER Confusion exists in the use of the word "onyx." True onyx is a banded chalcedony, a form of silicon dioxide related to jasper, agate, and flint. Calcium carbonate is commonly deposited from solution in successive layers of varying color closely resembling onyx, and for this reason such calcareous rock is also called "onyx." To distinguish the calcareous from the siliceous

Jan 1, 1940

By H. L. Burmeister

These properties were examined by a Bureau of Mines engineer in 1949. During 1950, these mines were studied by the Bureau to determine the possibility of increasing the production and augmenting the supply of fluorspar. As a result of this study, it was decided to core-drill the Knox-Yingling vein to test the continuation of fluorspar to a greater depth than that reached by mine workings. It also was desired to relate the present deposit with the Rosiclare formation. Development work by the Bureau of Mines was performed from February to May inclusive in 1951. Four diamond-drill holes aggregating 2,733 feet were drilled in the hanging wall of the vein.

Jan 1, 1952

By Loyal Clarke, H. H. Storch

"The discovery of large deposits of polyhalite (K2S04.MgS04.2CaSO4.2H2O) in Texas has led to an investigation of possible industrial proecsses for the extraction of potash from this material. This mineral was first discovored in small quantities in the European potash deposits in or about the year 1800. Chemists fire thought it to be a form of calcium sulphate, but a more accurate analysis by Strohmiyer indicated the composition as given by the above formula.The decomposition of polytalite by aster is very slow and results in the formation of a layer of gypsum at the surface of the polyhalite which retarts the solution of the potaseium and magnesium sulphates. To obtain a substantial yield of K2S04 in solution it is necessary to use large amounts of water at room temperature, for he concentration of K2S04 is limited by the low solubility of syngonite (K2S04.CaS04.H2O) whereas at 100º C. several days boiling are necessary to obtain more than a 6 per cent K2S04 solution even when finely powdered polyhalite is employed.In 1854 H. Rose discovered that calcination, followed by leaching with water, resulted in a larger extraction of the potassium and magnesium sulphates, as compared with leaching without precalcination. During the course of a series of investigations concerning formation of oceanic salt deposits, Van't Hoff and his pupils obtained sufficient data to construct the equilibrium diagram for the system K+Mg+SO4--Ca++.H2O for 25° C. and for 83° C. These data are very well summarized. in the International Critical Tables' and by Boeke and Eitel. From a consideration of the diagrams for 83º C. one would conclude that an extraction of polyhalite with moderate amounts of water at 33º C. would result in a solution whose maximum concentration of K2So4 would be about 3.6 grams per 100 grams of water and of M2SO; about 4.0 grams per 100 grams of water, corresponding to equilibriumwith the solid phases: Polyhalite potassiam-calcium pentasulphate and anhydrite.The fact that it has been found possible to obtain as high as 11.4 grams of K2S04 per 100 grams of water (see table 6) and an equivalent amount of MgSo4 (8.1 grams per 100 grams of water was obtained corresponding to a ratio K2/Mg of 0.98; indicates that the formation of these complex salts is very slow. To be sure, this results was obtained at 100° C. instead of 83º C. However, the work of Anderson and Nestall 9 on the double salts of calcium and potassium sulphates at 100º C. indicates that the diagram at 100º C. C. would not be greatly different from that at 83º C. This slow rate of approach to equilibrium when combined with precalcination of,of polyhzli-,a is the 17,asis of some of the more p:olisinE methods of extracting potash from polyhalite."

Jun 1, 1930