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By H. P. Greenwald

About mid-December 1936, the safety director of a large coal corporation visited the authors at the Bureau's Experimental coal mine to discuss a rock-dust barrier he had invented primarily for use in trackless entries of coal mines. The rock dust in this device was carried in its original paper containers and means were provided for ripping these open so that the dust might be scattered in the path of an explosion. The inventor termed the device a "bag barrier", and this term has been adopted in the present paper for convenience. At that time the device was in an early stage of development, and the inventor felt that the barrier should be tested to determine whether it had enough promise of being successful to justify further development. The matter was taken under consideration and finally three tests were made during the week of February 15, 1937. It was concluded that while the device did stop an explosion in two of the three tests, it was much loss effective than ordinary rock dusting, and that too few data were obtained to permit direct comparison with tests of other barriers. Apparently, the conditions under which the device could, be successful 'Were somewhat limited, out the limits could not be defined without additional tests.

Jan 1, 1938

By G. M. Molinda

The U.S. Bureau of Mines conducted an investigation to determine the nature and frequency of coal mine roof failure beneath valleys. A mechanism for this failure and suggestions for controlling this problem are presented. Hazardous roof conditions identified in some mines were positively correlated with mining activities beneath stream valleys. Mine maps with overlays of unstable roof and locations of stream valleys show that 52 pct of the instances of all unstable roof in the surveyed mines occurred directly beneath the bottom-most part of the valley. The survey also showed that broad, flat-bottomed valleys were more likely to be sites of hazardous roof than narrow-bottomed valleys. Evidence of valley stress relief was found beneath several valleys in the form of bedding plane faults and low-angle thrust faults. This type of failure, previously believed to be only a shallow phenomena, was found at mining depths as great as 300 ft. In situ, horizontal stress measurements beneath a valley and the adjacent hillsides, confirmed valley stress relief. Numerical analysis of 13 valleys overlying one mine property showed the effect of the valley excavation on horizontal and vertical stress.

Jan 1, 2010

By A. R. T. Denues

[Liquid oxygen explosives are ordinarily made from a carbonaceous absorbent and from liquid oxygen of high purity. These explosives have a limited but definite field of usefulness; their properties have been described in the literature, which includes several publications of the Bureau of Mines, the most recent dealing with fire-retardant treatments.3/ It seems generally conceded that the outstanding hazards in the use of these explosives are their high inflammability and their relative sensitivity to mechanical action. Each of these topics has been studied, and some interesting practical results have been obtained. Treatments have been described that render liquid-oxygen explosives prepared from granular carbonaceous absorbents practically immune to the action of igniting agents representing or exceeding practical hazards in violence.]

Jan 1, 1941

By P. R. Perry

This publication is a compilation of tested methods for the analyses of titanium tetrachloride, titanium sponge, and various intermediate materials and products. They are presented in concise form without the detail usually found in publication of new methods because many of them are modifications of well known procedures. The Electrometallurgical Experiment Station, Boulder City, Nev., has been developing titanium production methods since 1945. Most of this development was on a modified Kroll Process but also included work on sodium reduction and electrolytic methods. During these years a large variety of samples were analyzed. Most of the analytical problems were solved using published methods or modifications of the same. At the start, there were no published procedures for analyzing titanium sponge using spectrochemical methods. A great deal of study was given to testing several of the well known techniques, and some of them, such as direct sparking of the metal, proved to be completely unsatisfactory. Solution-spark techniques were finally tried, and satisfactory procedures were developed for some of the more common impurities. These spectrochemical methods were then put into routine use for several months before their publication.2/ Some new modifications have been made, and techniques have been developed to determine other impurities found in titanium sponge and tetrachloride. All spectrochemical methods used in 1954 are included in this publication.

Jan 1, 1955

By K. J. Liles

To encourage the development and conservation of the Nation's ceramic raw materials, the Bureau of Mines, U.S. Department of the Interior, under an agreement with the Georgia Department of Natural Resources, evaluated samples from a clay resource located in Clay County, Ga., for use as a raw material for lightweight aggregate. The physical properties of clay samples, taken from 5-foot increments of drill cores from 11 holes, were determined. Raw materials were plasticized and extruded to produce 1/2-inch by 1-inch pieces and fired in a rotary kiln to produce lightweight aggregate samples. The resulting expanded material had excellent loose pour weights ranging from 30 to 37 lb/cu ft. The expanded test materials were crushed, sized, and used as aggregate to form concrete cylinders. The unit weight and compressive strength of the cylinders averaged 106 lb/cu ft and 3,350 lb/sq in, respectively; these values meet American Society for Testing and Materials specifications for structural concrete. The clay from the drill cores was also used to make test bars that were evaluated for building brick.

Jan 1, 1980

By James Paone

The Bureau of Mines conducted laboratory drillability studies on nine rock types using two mining-type percussive drills. Percussive-bit action was simulated by dropping a known weight on a rock sample to obtain a coefficient of rock strength for each rock drilled. While no single physical property of a rock is completely satisfactory as a predictor of penetration rate, coefficient of rock strength showed a better correlation with penetration rate than did other physical properties. Results also indicate that over the range of energies investigated, energy per unit volume in a given rock is independent of blow energy. A drillability index for the percussive system is proposed that utilizes the coefficient of rock strength test to determine energy per unit volume for a given rock which, along with the work rate of a given drill and the bit diameter, is used to predict the penetration rate as shown in the following equation: [R = 4P pD2 E, where R = penetration rate, in/min, P = work rate, in lb/min, D = bit diameter, in, and Ev = energy required to produce a given volume of rock, in lb/in3.] Laboratory tests indicate this method's potential as a simple and reasonably accurate method of predicting penetration rates with any percussive drill and bit combination.

Jan 1, 1969

By Ernest A. Curth

A 3-month study in 1971 of the Essen Roof Support and Rock Mechanics Research Center's program of roof and support evaluation included 25 mine trips. German miners must adopt mining methods and environmental control measures involving methane drainage and water infusion to improve productivity under severe natural conditions. Pressing problems in ground control must be solved such as cavities in front and above the supports at longwall faces and excessive convergence in gate roads. The Center developed automatic data processing methods to quantify the results of roof and support surveys and to establish criteria. Another approach to ground control is the study of mine models. The Center's laboratory has the facilities to test elements of powered roof support and whole assembled units. Face automation and roof control by powered shields are novel developments that are under close scrutiny in the field as well as in the laboratory. Though the Essen Center's roof and support evaluation techniques are tailored to the needs of the coal mining industry of the Federal Republic of Germany under conditions vastly different from those in the United States, some application may be found here, for instance, monitoring faces and roadways and preventive maintenance of hydraulic systems.

Jan 1, 1974

By R. O. Kneisley

This U.S. Bureau of Mines report summarizes a study of large-scale strata response to longwall mining at a western U.S. coal mine. This study utilized surface and subsurface measurements, geologic mapping, in situ stress measurements, and pressure cell readings to characterize strata behavior. Preliminary analysis of surface subsidence and time-domain reflectometry (TDR) was used to determine a suggested main roof caving sequence. Coal ejected from the face apparently resulted from brittle failures that occurred because of lack of significant yield zone development. The combination of a strong coal with pronounced directional behavior, low overburden pressures, a good caving roof, and a high-production environment that minimized time-dependent loading apparently reduced yielding of the longwall face. The panel 1 headgate-entry design appears adequate; however, the abutment pillar and adjacent panel tailgate rib are highly stressed and may contribute to problems during second panel mining. The small chain pillar yielded after passage of the face, but the pillar width may be near maximum since evidence of a stressed core exists.

Jan 1, 2010

By T. D. Moore

Methane emission from two surface gob-degasification boreholes was measured by the Bureau of Mines. The investigation took place during mining of a 3,200-foot longwall panel in the Lower Kittanning coalbed in central Pennsylvania. The first hole was 500 feet from the start of mining, and the second hole was 2,200 feet. The first hole went on natural draft as soon as the longwall face passed it. This caused the methane flow in the return entries to drop 75 pct. In the 6 months required to complete the panel, the two holes emitted 69 MMcf of methane in varying percentages of concentration in air. In 3 years, the holes emitted a total of 150 MMcf of methane.

Jan 1, 1976

By G. W. Jones

As a part of its general safety program the Bureau of Mines has investigated various means useful for the elimination or mitigation of the explosion hazards in connection with combustible gases incident to the mining industry. Information has been obtained relative to the explosibility of numerous simple and complex gaseous combustible atmospheres. Although experiments along this line have pertained largely to combustible gases in the mining and allied industry, considerable information has been obtained relative to the explosive hazards of combustible gases and vapors used as anesthetics.

Jan 1, 1939

Objective To characterize the roof fall risk associated with underground limestone mining. Background During the first 5 years of this decade, more than one-fourth of the underground mining fatalities occurred as the result of fall of ground. The large openings in underground stone mines present limitations in observing ground conditions because of floor-to-roof heights ranging from 20 to 60 ft or more. Generally, the status of ground conditions in under-ground stone mines is based on observation and experience obtained during mining development. Some mines use monitoring instruments to gain information on roof conditions, but this practice is typically focused and localized to address issues in a particular area or section of the mine. The Roof Fall Risk Index (RFRI) described here provides a method of systematically characterizing the risk of roof falls to enhance the safety of mine workers. Approach As in many industries, a defective product signals the potential for failure. Similarly, defective rock or strata in an underground stone mine presents a potential risk. Assessing ground conditions relative to the concentration of defects observed provides a way to index or rate these conditions and the subsequent risk. Through observations at approximately 50 underground limestone mines in the United States, strata defects were categorized to develop a quantitative method for determining the RFRI. This method is specifically geared to underground lime-stone mines because strata defects are difficult to see and limited by the experience and knowledge of the observer. Overall, 10 defect categories were deter-mined: 3 that relate to geology, 4 that result from mine development, 2 that are indicative of the roof profile, and 1 that addresses moisture or water flow (see RFRI Chart 1). The defect categories are also weighted to reflect the conditions indicative of roof or strata movement or separation (categories 4 through 8). These weights are multiplied by the assessment value to determine the total category value. The benefit of using monitoring techniques to gain information on roof conditions is also factored into the RFRI for overall assessment of an area in the mine. Each defect category is assessed with a value of 1 to 5 based on parameters as defined in each defect category, with 5 indicating the highest degree or level of defect. The assessment value of 3 is also used when information on a parameter is unknown. The parameters for the defect categories are illustrated in RFRI Chart 2 for use in determining the assessed value. How It Works The RFRI provides a means to categorize the risk for roof falls in underground stone mines. The concept of this calculation is aimed at providing an indication of the level or degree of defect relative to the area of the mine examined. The RFRI for the calculation produces a distribution where RFRI values approaching 0 represent a stable condition and those ap-proaching 100 represent an unstable condition.

Oct 1, 2006

By L. B. Berger

Studies showing the effect of mixing hot exhaust gases with the intake air of a four-stroke-cycle Diesel engine are described. The results indicate a marked increase in carbon monoxide in tip exhaust gases, a decrease in oxides of nitrogen, and no significant effect on aldehydes. The increase in carbon monoxide was greater at higher fuel-air ratios and was caused partly by the increase in fuel-air ratio end partly by the decrease in oxygen concentration resulting when exhaust has was added. The application of these results to the use of Diesel engines underground is considered.

Jan 1, 1940

By C. L. Severy

The Reeder No. 1 well was drilled by the Bureau of Mines in cooperation with the Geological Survey as agents for the Defense Plant Corporation. The well is south of Crescent Junction near Thompson, Grand County, Utah. It was started May 5, 1942, and completed August 3, 1942, for the purpose of con-firming the presence of magnesium salts in a deeply buried bed. Drilling was done under contract by the Mack Drilling Co. This report contains an outline of the physical features of the well, a brief history of drilling, and a description of the deposits and occurrences of oil and gas encountered in the drill hole. The work performed by the Bureau of Mines is described in considerable detail, with particular emphasis on drilling procedure and sampling. The report is concluded with a brief description of core-sample preparation for analyses. Appendix A comprises a log of the drill hole, and appendix B is a tabulation of analyses of cores.

Jan 1, 1949

By Harold L. Rhodes

The Bureau of Mines has developed a quantitative method to determine water vapor in helium in the range of 0.1 to 15 ppm by volume. This method uses the quantitative chemical reaction of H20 with CaH2, which produces 1 mole of hydrogen for each mole of H20 in the sample. A gas chromatograph is then used to determine the concentration of hydrogen in the product. The precision of the H20 analysis is ±0.05 ppm at a concentration of 1 ppm. This method is used to calibrate a commercial platinum-phosphorus pentoxide (Pt-P205) electrolytic water vapor analyzer that has an improved inlet system and digital voltmeter readout.

Jan 1, 1981

By R. H. Sprute

This report describes Bureau of Mines laboratory test results in electro-kinetic dewatering and consolidation of metal-mine mill tailings from five mines in the Coeur d'Alene, Idaho, district. Classified (coarse) tailings, slimes, and unclassified material were separately tested. Tailings were placed in 0.3 ft3 plexiglass models, and dc potential was applied until dewatering ceased. Time-oriented measurements of water removal, changes in resistivity, and power consumption were recorded during the dewatering process. Moisture content and density of the dewatered material at test end indicated the method to be generally effective for all materials examined, but best results were achieved with well-mixed unclassified tailings.

Jan 1, 1974

By H. W. Kilau

The Bureau of Mines evaluated synthetic fluorspars as substitutes for natural fluorspar in basic oxygen steelmaking using a high-temperature rotational viscometer and a quarter-ton basic oxygen furnace (BOF). Consider-able variation in stability and BOF slag fluidizing properties were found when using the initial synthetic products, but improved synthesis methods produced synthetic fluorspars that were generally comparable to natural fluorspar in laboratory testing. Trials in the furnace showed the synthetic products to be operationally the equivalent of natural fluorspar. Higher sulfur and phosphorus contents in some of the synthetic materials did not adversely affect the steel chemistry. Analyses of wet scrubber samples showed evidence that the pelletized synthetic fluorspars experienced greater physical and chemical disintegration than did natural fluorspar. It was also found that operation of a BOF without fluorspar is possible when making low-carbon steels because iron oxide is intrinsically generated as the slag fluidizer.

Jan 1, 1981

By N. Kumar Kittusamy

The purpose of this study was to assess the adequacy of the cab design and to determine the percentage of musculoskeletal symptoms among workers. A questionnaire was designed to assess demographics, work information, job history, and musculoskeletal symptoms in operators of heavy construction equipment. Information concerning equipment included design of the seat/chair, levers, pedals, bothersome vibration, quality of egress from the equipment, proper preventative maintenance and repairs, and age of the equipment. The body regions that were evaluated included the neck, middle/upper back, low-back, shoulder/upper-arm, elbow/forearm, wrist/hand, hip, knee, and ankle/foot. One hundred and eighty nine operators completed the questionnaire. The results indicate that these workers are at risk for developing musculoskeletal disorders, the need to perform a larger survey to further substantiate the outcome, and the need to quantify risk factors (i.e., whole-body vibration and static sitting postures).

Jan 1, 2003

By John B. Knaebel

Hammer machines are now widely used for underground sampling and exploration. Their application to such work can be divided into two classes - sampling and testing with ordinary drilling equipment to shallow depths of 22 feet or less, and "long hole" drilling with heavy machines and special equipment to depths of as much as 250 feet or more. In the first category hammer drills are employed for either of two distinct purposes: first, as a means of checking the results of grab or cut samples or, in certain types of ore deposits, as a substitute for these methods; and second, as a method of sampling the ground 5 to 20 feet beyond existing faces and thus aiding in the control of stoping operations or in the direction of development headings, as the case may be. The deep-hole drill, in the second category, has proved to be a valuable adjunct to the old established methods of exploring, end developing ore, provided it is employed under natural conditions to which it is suited, handled by men thoroughly familiar with the technique of its operations, and used with its possibilities and limitations clearly understood.

Jan 1, 1932

By F. D. DeVaney

Metallurgists and coal-washing engineers have used heavy liquids for years in studying the characteristics of ores and coal. By such means true separations can be made between the various specific-gravity increments in the materials examined. To use of heavy liquids has permitted determination of the possible grades of tailings and concentrates by specific-gravity methods on any particular size, and therefore the size to which the ore must be crushed to free the valuable material. The simplicity of float-and-sink separation and the high degree of efficiency attained in the laboratory are factors that commend the method for commercial concentrations.

Jan 1, 1940

By G. W. Grove

The Joseph A. Holmes Safety Association acid the Holmes Association have fostered many chapters that have served as a medium in increasing safety in the mining industry. Details relating to the formation, operation, and achievements of the J. J. Forbes District. Council of the Holmes Safety Association, which operates in the Uniontown-Brownsville bituminous coal district of western Pennsylvania will be of interest to all who are striving to increase safety in mines, quarries, and in the oil fields. The Joseph A. Holmes Safety Association The Joseph A. Holmes, Safety Association' was organized in 1916 by 24 of the leading technical societies and mining organizations to perpetuate 'the memory of Dr. Joseph Austin Holmes, first Director of the United States Bureau of Mines.

Jan 1, 1929