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By G. K. Derby

The Bureau of Mines studied the problems caused by airborne contaminants from welding exhaust in surface mining operations and investigated equipment designed to reduce existing hazards. Four commercially available welding-fume exhaust units were tested to determine their effectiveness. Results indicated that the four units had the capability of controlling airborne particulate concentrations and bringing them to within allowable exposure limits.

Jan 1, 1981

By Wesley A. Grosh

The Sutherland copper prospect is situated in Floyd County, Va. The immediate area was prospected around 1850, and one of the adits possibly dates from that time. Little or no ore has been mined from the deposit. The deposit is a mineralized sulfide zone occurring in mica schist and consisting mostly of pyrrhotite with minor amount of copper. A magnetometer survey of the deposit by the American Metal Co. in 1939 showed an anomaly that was thought to indicate a zone: of secondary enrichment. The Bureau of Mines diamond-drilled 14 holes, totaling 913 feet, and opened an adit during February and March 1943. No appreciable copper values or indications of secondary enrichment were found.

Jan 1, 1948

By James J. Olson

The Bureau of Mines recorded peak particle-velocity levels and vibration frequencies to determine the nature and intensity of ground vibrations for tunnel blast rounds at the NORAD Complex, Colorado Springs, Colo. Previous Bureau of Mines studies in quarries and underground mines had shown that scaling (dividing) the distance from the blast by the square root of the charge weight removed the effect of the various charge weights on vibration amplitudes. The analysis of variance tests performed on the NORAD vibration data, however, indicated that the cube rather than square root scaling exponent grouped the data more effectively. The empirical propagation equation, V = 560 (D/w1/3)-2.04, where V is the maximum peak particle velocity in inches per second, D is the distance from the blast in feet, and W is the zero-delay charge weight in pounds described the attenuation, with distance, of the particle velocities from the tunnel blasts in the Pikes Peak Granite of the NORAD Complex.

Jan 1, 1972

By Irving Hartmann, Bernard Lewis, John Nagy, H. P. Greenwald, H. C. Howarth

"ORIGIN OF INVESTIGATIONThe Federal Mine Safety Code for Bituminous Coal and Lignite Mines of the United States, July 24J 1946, contains the following provisions with regard to rock dusting: Article VI. - Section 2. Rock dusting.(a) All mines, except those mines or those locations in a mine which are too wet or too high in incombustible content to propagate an explosion, shall be rock-dusted to within 80 feet of the faces of rooms and entries; however, if the mine or any part of it is wet but becomes dry, the mine or portion of the mine so affected shall be rock-dusted as ·soon as it becomes dry. (b) In mines partially rock-dusted or in mines that are required to start rock dusting, haulageways and parallel entries connected thereto by open crosscuts shall be rock-dusted. Back entries shall be rock-dusted for at least 1,000 feet outby the junction with the first active entry. Inby this junction, the rooms, entries, and crosscuts shall be rock-dusted by generalized rock dusting as provided for in section 2(a).(c) Where rock dust is applied, it shall be distributed upon the top, floor, and sides of all open places and maintained in such quantity that the incombustible content of the mine dust will not be less than 65 percent. In trackless entries and air courses, protection in lieu of generalized rock dusting may be had by using bags filled with rock dust, if they are placed at regular intervals and staggered as described in Bureau of Mines Report of Investigations 3411."

Feb 1, 1948

By William K. Tolley

The U.S. Bureau of Mines (USBM) is currently investigating the electrochemistry of mineral flotation. A significant need in this area is greater reliability of sensors. The USBM is testing electrolytic methods to clean and condition redox-sensing electrodes to improve the reliability and extend the service life of these instruments in the harsh physical and chemical environment of mineral processing slurries. A novel method for removing scale from fouled electrodes has been developed that includes anodic polarization to 1.2 V versus the Ag/ AgC1 reference potential, followed by brief potentiodynamic conditioning. Laboratory results show that this technique removes calcarious deposits from gold sensing electrodes and returns the electrodes to useful service within approximately 10 min. Mechanical abrasion to remove the scale is thereby avoided.

Jan 1, 2010

Provide a low-maintenance, reliable means of generating bubbles and controlling bubble size for column flotation. Approach Commercial sparger systems used in flotation columns to process minerals provide only limited means of controlling the size of bubbles generated and the rate of air injection. Generally, these limitations are a detriment to flotation performance, particularly in recovering coarse or fine mineral particles. In addition, conventional bubble generation systems require frequent maintenance, often requiring shut-down of the column itself for repairs. To permit greater control of the bubble size generated in the flotation column and to eliminate the counter-productive problems associated with the operation of current air sparger systems, the Bureau of Mines investigated alternative methods for generating bubbles. Based on the investigation, an external bubble generation system was designed, developed, and laboratory and commercially tested.

Jan 1, 1987

By Lisa Steiner

Almost every process has a predecessor, and studying the predecessor helps to define needs and shortcomings to be addressed in the new design. It also suggests what information is needed by the users in order for them to be able to operate safely and effectively. The end users of a system can provide important feedback to better evaluate the current and proposed designs. When new technology is introduced into a system, mishaps may occur before it is realized that human-system interactions were not considered adequately in the design process. A systematic methodology to evaluate the causes of these injuries and to develop remedial recommendations can enhance safety. This paper illustrates how such an approach was used to assess remote machine operation in underground coal mines. The dynamic work environment of underground mining with its unpredictable geologic anomalies can result in numerous hazards. Many of these hazards, including mine roof collapse, occur near the working face where coal is being extracted. The face area is also where the most intricate interactions of people and equipment occur. For these reasons, a high priority has been placed upon minimizing hazards to the workers at the face. A remote control operation was introduced to provide a safer working distance from these hazards. As the remote control technology began to be widely used for extended cut mining operations, new issues became evident. It was essential to develop mechanisms for mines to evaluate these issues in order to predict and reduce injuries. Mining methods and equipment changes must allow for the ability of workers to adapt to changes in their dynamic mining environment. Consideration should be given to how the worker will use familiar information to make decisions in now unfamiliar situations. There will be both intended and unintended consequences [Merton, 1949]. Designers try to anticipate and eliminate surprises, but it is impossible to eliminate them all. How, then, will the new system affect the tasks to workers which are currently accustomed? As suggested below, this question may be addressed and more of the unintended outcomes predicted with a planned design process which includes strong human factors input to determine interactions and behaviors of participants.

Jan 1, 2005

By S. H. Ash

"INTRODUCTION Mine fires have occurred since underground mining of minerals began, and they are still occurring. The technical literature is replete with papers relating to mine fires.Means and methods for controlling and extinguishing mine fires and preventing explosions and other accidents require the collection and analyses of samples of the atmospheres surrounding the fire. Such atmos¬pheres are complex mixtures of gases (1, 3, 4, 15, 21, 23).3/SUMMARYExperiences at mine fires (1, 3, 4, 15, 21, 23) have proved conclusively that mine-air analyses furnish the only means of judging what is going on in a mine fire area. Mine-air analyses give evidence of conditions that require immediate protection, govern the order and control the manner in which a fire is fought, show the necessity of bulkheads and establish the places to construct them, indicate whether or not a fire is being controlled or is being extinguished, and govern procedure in sealing and unsealing mine fires.It is commonly believed that danger to life and property from mine-fire atmospheres is greatest in coal mines; this is true only to the degree that the explosion hazard is greater in coal mines than in noncoal mines because of the presence of combustible gases. The problem of gas poisoning is greater in noncoal mines because of the more frequent occurrence of poisonous and innocuous gases, oftentimes the lack of controlled ventilation, and usually greater difficulties in sealing mine-fire areas. Sulfide minerals present a serious hazard in many metal-mine fires when sulfur dioxide is formed. The country rock or ore body itself may contain or be limestone, which may be calcined. Emanations of carbon dioxide are found."

Dec 1, 1950

By Ronald D. Hill, Elmore C. Grim

The goal of blasting is to get maximum fragmentation of the consolidated material in the overburden with optimum drilling and blasting cost. The amount of fragmentation required is determined by the stripping unit to be used In overburden removal. Many coal seams must also be broken by blasting; this is conducted before coal removal. There are environmental factors as well as due regard for public safety, health, and welfare that must be considered in choosing the blasting plan. The blasting plan should be made during preplanning and is based on data from the overburden cores. Analysis of the data will help In determining the kind of drilling equipment and bit types that will be needed for overburden preparation.

Jan 1, 1974

By W. P. Diamond, B. M. Bench, C. M. McCulloch

Coalbeds exhibit a directional permeability, with the maximum permeability oriented parallel to the face cleat. Thus, the most efficient pattern of vertical degasification holes for a coalbed is dependent upon cleat orientation. Surface joints, infrared photolinears, and Ronchi grating photolinears were investigated as potential estimators of subsurface cleat orientation. Cleat orientations were masured in 18 mines, in the Pittsburgh coalbed in southwestern Pennsylvania and northern West Virginia to be used as a standard against which prediction techniques would be evaluated. Two cleat systems with a strong geographic segregation were measured in the study area: N 67° W - N 28° E (95° separation) for the north, and N 76° W - N 17° E (93° separation) for the south. Directional data obtained from the three techniques investigated yielded satisfactory regional predictions of cleat orientation. Analysis of surface joints was the only technique considered sufficiently reliable on a local basis. Prediction of cleat orientation is based on the pairing of the principal directional sets into all reasonable combinations of fundamental systems. The system or systems composed of the most dominant sets nearest to 90° separation are likely to be a reliable prediction of cleat orientation. The most dominant set of the system selected is likely to be the face cleat.

Jan 1, 1976

By d&apos, Kathleen J. Amico

THIS SUMMARY is shown in volumes I and III of this series on mineral production in the United States (including Alaska and Hawaii), its island possessions, the Canal Zone, and the Commonwealth of Puerto Rico, and on the principal minerals imported into and exported from the United States. For further details on production, see the several commodity and area chapters. A summary table comparing world and U.S. mineral production also is included. [ ]

Jan 1, 1960

By W. K. Tolley

This report presents data collected during research by the Bureau of Mines on corrosion of grinding media. Corrosion rates of eight alloys commonly used in grinding media were tested in synthetic mill water using an ultrasonic grinding device especially designed for this work. Electro-chemical measurements showed variations in corrosion rates for these alloys between 9.8 mpy for medium-carbon steels and 0.14 mpy for high chromium white irons. Bureau data are discussed along with data from the literature to indicate that corrosion causes less than 10 pct of the wear of grinding media in commercial grinding mills. A comparison of corrosion rates for various types of grinding media shows that alloying elements and electrochemically active inclusions in steel affect the corrosion behavior of the media.

Jan 1, 1984

By Paul Hopkins

The following methods have been selected from a large number tried while assaying several hundred samples of placer concentrates. It is thought that some of these methods may be useful to those who are required to assay similar products containing large quantities of metallic articles, such as jeweler's sweepings. No great difficulties will be encountered in assaying black sand from beaches or river bars. Such samples require care in grinding and sifting so that no oversize particles of gold or platinum are lost. It is also necessary to have sufficient silica in the flux to form a fluid slag with the excess of iron, magnesium, or chromium which such samples contain. It is much more difficult to assay black sands, or concentrates, produced in large-scale placer-mining operations. These products are usually much harder and more abrasive than the beach black sands. They also contain numerous metallic particles resulting mainly from wear on the mining machinery. These particles consist chiefly of iron or steel but also contain lead, copper, and alloys such as babbitt, solder, brass, ferrosilicon, etc. Fairly large particles of gold are often found. Some samples will contain as much as 10 percent of such metallic particles. It is not feasible to remove the particles of iron with a magnet and discard them, as they invariably contain gold, sometimes a considerable amount. This gold is attached to the iron particles by rust or wedged into cavities. Scraps of sheet iron are often found which have become tightly folded or rolled and contain gold or amalgam within the folds.

Jan 1, 1934

By William C. Larson

A study was conducted by the Bureau of Mines to provide quarry operators with information regarding (1) the effects of jointing and bedding on rock fragmentation when bench blasting in two small-scale (2.5-ft) limestone benches, and (2) the successful use of inexpensive equipment and field techniques to determine the orientation and spacing of joints and bedding separations within the quarry. Using inexpensive equipment, such as a pocket transit and steel and paper tapes, joint and bedding separations were mapped and their frequencies measured. Results from two small-scale bench blasts in the Stewartville member of the Galena limestone formation showed that when the row of vertical blast-holes was oblique to the vertical joint orientations, the backface expression was outlined by two relatively large triangular protrusions (joint surfaces). In this blast, part of the rock burden was unbroken. When the line of vertical blastholes paralleled a predominant joint set, all of the rock burden was broken and displaced. The thickness of fragments that had been displaced by a blast correlated with the observed bedding thickness in the bench.

Jan 1, 1974

By D. T. Hahn

Adequate and cost effective erosion control is an important component in most plans for reclamation of surface mined land. Despite the fact that much is known about erosion of agricultural lands, insufficient conclusive knowledge is available about erosion of reclaimed surface mined land. Our study was conducted to characterize the erodibility of reclaimed surface mine land relative to unmined cropped land, and to evaluate the accuracy of the universal soil loss equation (USLE) in estimating erosion from reclaimed soils. A rainfall simulator was used to measure runoff and erosion rates from plots at three Indiana surface mines. The relation of erosion of the reclaimed soils was not completely constant with that from the cropped soils. Significant differences in erodibility were observed between reclaimed and nonreclaimed top soils, as well as reclaimed topsoils and reclaimed subsoils.

Jan 1, 2011

By M. G. Cherniack, A. J. Brammer, D. R. Peterson

Over the past two decades, there have been significant reductions in industrial exposures to hand-arm vibration, especially when specific tools and work processes have been redesigned to incorporate anti-vibration and ergonomic principles. Nevertheless, Hand-Arm Vibration Syndrome (HAVS) remains a significant occupational health problem as disease symptoms continue to occur even when vibration exposure levels believed to incur low risks have been reached2. This inconsistency may be related to the methodology that is typically used to estimate workday vibration exposure levels, involving laboratory and/or very short duration field measurements coupled with estimates of overall eight-hour tool operation times determined from brief observations of tool tasks and/or self-reported surveys. One solution is to use small, commercially-available, personal vibration dosimeters to calculate, record, and display long-duration vector sums and energy equivalents of vibration. However, since these devices are attached to the worker and require tool-mounted accelerometers, they are incompatible with the worker performing normal duties involving putting down or changing tools. In addition, these commercial systems do not allow for the characterization of the transmission of vibration to the hand such as monitoring the mechanical coupling between the hand and the tool handle (e.g., grip forces). O’Boyle and Griffin showed that variations in applied force can alter vibration transmission characteristics by 50% or more indicating that the measurement of grip force is essential for modeling vibration transmissibility and vibration exposures5. In summary, a need exists for the development of a method and device that will more accurately characterize workday-long vibration exposures. Methods A portable, light-weight, Vibration Exposure Monitor (VEM) system was developed to record user-specific tool-operating times, vibrations, and grip forces throughout all, or a representative part, of a workday. It monitors frequency weighted and unweighted accelerations from a palm-mounted uni-axial accelerometer (Model 352C22, PCB Piezotronics, Depew, NY) and calculates exposure levels using the root-mean-square (RMS) and higher power mean values, such as the root-mean-quad (RMQ) and the root-mean-oct (RMO). Grip forces are also monitored using a palm-mounted force sensor (Model 400, Interlink Electronics, Camarillo, CA) from which average grip force levels and exerted grip extrema are calculated. At the core of the VEM system is a commercially available, battery-powered microcomputer (Tattletale, Model 8v2, Onset Computer, Onset, MA) with one megabyte of memory and eight analog channels using 12-bit sampling at a single-channel maximum of 100 kHz. Analog signal processing (i.e., anti-aliasing, with cutoffs at 4 and 1250 Hz, and ISO 5349-13 frequency weighting) is accomplished using custom circuitry that is directly interfaced with the microcomputer. An embedded C-based protocol governs the data collection from each channel

Jan 6, 2006

By Kenneth C. Stewart

This contract was directed toward a study of the attenuating properties of earmuffs as worn by miners. Two attenuation measurement procedures were utilized. Human subjects were tested in a diffuse sound field according to threshold shift procedures recommended by the American National Standards Institute and a physical measurement procedure was accomplished in the same diffuse field on the same human subjects with microphones placed simultaneously on the inside and outside of the muffs. All measurements were obtained in one third octave of random noise. The results of the study indicated that physical and psychophysical attenuation measurements are in essential agreement at frequencies from 125 Hz to 2 KHz. Above 2 KHz the psychophysical measurement demonstrates larger amounts of attenuation than the physical measurement. The difference in attenuation ranged from approximately 7.0 dB to 9.0 dB at frequencies of 4 KHz and above. A possible explanation for the observed differences in attenuation has been presented.

Jan 1, 1980

By T. W. Hunter

THE TOTAL production of energy in the United States in 1954 decreased 4.6 percent below 1953. The production of coal continued to decline, and the production of crude oil decreased for the first time since 1949. These decreases were partly offset by an increase in the production of natural gas. The total energy production of 35,365 trillion B. t. u. in 1954 was the lowest since 1950. [ ] This drop in energy production was consistent with the 1.1-percent decline in gross national product during the year-from 364.5 billion dollars in 1953 to 360.5 billion in 1954.

Jan 1, 1958

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 Jami M. Girard

INTRODUCTION Slope stability accidents are one of the leading causes of fatalities at U.S. surface mining operations. The Spokane Research Laboratory of the National Institute for Occupational Safety and Health (NIOSH) is currently conducting research to reduce the fatalities associated with slope failures and other unexpected failures of ground. The purpose of this paper is to introduce various warning signs of slope instability so operators are better able to recognize hazards. The most common slope monitoring equipment and practical methods of installation are discussed as well as the limitations of these systems. CONSEQUENCES OF SLOPE FAILURES Unexpected movement of ground causes the potential to endanger lives, demolish equipment, or destroy property. Between 1995 and 2001 (2nd quarter), 34 fatalities were caused by ground instability. This accounts for approximately 15% of all surface mine fatalities (Figure 1). These figures include fatalities classified by the Mine Safety and Health Administration (MSHA) as “fall of face or highwall,” “powered haulage,” “equipment,” and other MSHA accident categories, where the primary cause of the accident was unanticipated movement of the ground. This includes fatalities resulting from bench and highwall failures, rock falls, waste dump and stockpile failures, and the collapse of unknown underground workings. [ ]