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By James R. Aggson

The theoretical relationships that are used to calculate in situ rock stress magnitudes and directions from borehole deformation data obtained during overcoring are based on the assumption that the rock is a linearly elastic material. Strictly speaking, this assumption is not valid in any rock. Thus, investigators using overcoring techniques must either accept various degrees of nonlinearity and the associated inaccuracies or use core testing techniques that address the problem and compensate for elastic nonlinearity. Previously developed test procedures for stress-relief overcores partially correct for nonlinearity. This Bureau of Mines paper describes a test procedure that completely corrects for elastic nonlinearity in stress-relief overcores.

Jan 1, 1977

By Oliver Bowles

Granites are classed as igneous rooks; they have been formed by the solidification of rook magmas or Solutions from deep within the earth. It is an almost invariable law of nature that mamas which cool quickly form fine-brained or glassy rocks, while those that cool slowly are completely crystallized and are coarser-grained. Granites, being of the latter class, are regarded as having attained their solid form at considerable depth below the surface under conditions of high temperature and pressure. The constituent minerals crystallized out slowly, the crystals interlocking with one another. The great depth of overlying rocks that must have been present when crystallization took place has been removed by erosion over large areas on the surface of the earth in consequence of which granites appear at or near the surface in many localities.

Jan 1, 1930

By Joseph A. Perry

One goal of the Bureau of Mines is to develop technology tp insure a dependable supply of minerals to the United States. To support this goal, the Bureau's Albany Research Center has modified a commercial atomic absorption spectrophotometer to rapidly determine trace levels of mercury by cold-vapor atomic absorption spectrophotometry. Such diverse materials as ores, mill products, stream water, sediments, and flue dust have been analyzed. A very high dynamic range of 0.2 ng/ml to 1 µg/ml of mercury in solutions is routinely analyzed by this instrument.

Jan 1, 1981

By Frank E. Cash

"INTRODUCTION The producing iron-ore ranges in the Lake Superior district are the Marquette and Menominee in Michigan, the Gogebic in Michigan and Wisconsin, and the Cuyuna, Mesabi, and Vermilion in Minnesota. These ranges produce about 85 percent of the iron ore mined in the United States. The accident experience in connection with this production is better than that of the regions producing the remaining 15 percent. Production and shipments vary slightly from year to year owing to stockpiling underground ore during the winter, or nonshipping, season but closely approximate each other over a period of years. This information circular supplements, combines, and continues the data contained in Information Circulars 7321 3/ and 7410 4/, including statistics for 1946 and 1947.Whereas the title ""Accident Experience"" is used for uniformity and logical indexing throughout this report, ""injury"" will be used as a general term to apply to disabilities of all degrees.During the 8-year period 1940 to 1947, inclusive, 619,054,023 long tons of iron ore was shipped from the Lake Superior district. 5/ Michigan and Wisconsin shipped 117,828,939 tons, or 19.03 percent of the total, and employed approximately 9,260 men. Minnesota shipped 501,225,084 tons, or 80.97 percent of the total, and employed an approximate annual average of 12,260 men. The tons produced and shipped per man employed in Minnesota is much greater than in Michigan and Wisconsin, owing to the large open-cut production in Minnesota."

Jun 1, 1949

By C. P. Bowie

[Frequent accidents in the transportation and. handling off petroleum and its more volatile products, serve as a reminder that this is indeed a hazardous undertaking and should always be conducted with due caution. On October 4, 1920, vapors in the held of the British tanks steamer G. R, Crowe became ignited and, caused an explosion which, it is reported, killed 5 men, injured. 40 others and endangered the lives of some 300 more. On November 10, 1920 the Morgan, Line freighter El Mundo was almost totally sot destroyed in New York harbor by fire caused by an explosion of gases in a fuel-oil tank. These two disastrous explosions emu emphasize the ever- present danger attending the use of petroleum products. This is also shown by the frequent occurrence of minor fires and explosions, caused by careless handling of baseline, which result in loss of life or serious injury to railroad employees, to oil-tank drivers, and to individuals in various walls of life. Statistics indicate that the lighter cuts of petroleum products, because of fire hazards, are dangerous, and are so considered by the railroad and other transportation companies. According o the Bureau of Explosives (Bar-eau of Explosives Report No. 13 p. 7) during 1919 transportation of gasoline in the United States resulted in 172 accidents, causing 2 deaths and 31 injuries, and a property loss to the extent of $687,966. Among the causes of ignition, an open light in the vicinity of the container stands out most prominently.]

Jan 1, 1920

By M. Hertzberg

This Bureau of Mines report proposes a new methodology for estimating industrial dust explosion hazards in terms of three probabilities or co-factors: The dispersion of the dust, the existence of a flammable dust concentration, and the presence of an effective source of ignition. This method or rationale is proposed as a replacement for the "explosibility index" that was first suggested 25 yr ago, but which, by consen-sus among leading researchers in the field, is now outdated. This report presents a detailed critique of the deficiencies of that old, material-oriented index, and develops the logical rationale for its re-placement by an approach that is better suited for quantitative hazard evaluations. A variety of such evaluations are illustrated, which show how a quantitative prediction of explosion frequencies can be obtained from laboratory measurements and operating conditions in a given indus-trial facility. The method has some pitfalls, particularly as they re-late to the correlation of events or their randomness. These are discussed, as well as the method's other limitations and uncertainties. This work is intended to provide a beginning to a quantitative approach to explosion hazard assessment. To that end, a new method is proposed for estimating thermal ignition probabilities in terms of the measured laboratory autoignition temperature of a dust, its relationship to the operating temperature, and its distribution within a given industrial system.

Jan 1, 1987

By M. R. Geer

All the coal lands in Alaska are publicly owned, and the Federal Government is the principal consumer of coal. Therefore the Government has long been concerned with the wise utilization of the coal reserves of Alaska as well as with the availability of coals meeting the specifications for use in various Government installations. Coal preparation plays a key role in both of these areas of interest. The proper choice and operation of coal-washing equipment permits the mining of inferior deposits, minimizes waste of coal in preparation, and assures a prepared product of the best quality obtainable from the raw coal. Thus, from time to time, the Bureau of Mines has made washability examinations on most of the coals mined in Alaska. Generally, these examinations were made when new mines or new beds were opened, when construction of new preparation plants was being considered, or when the operation of existing plants could be improved by better knowledge of the raw coal. The purpose of this report is to bring together all the washability data available on the coals of the Matanuska Valley and Beluga River fields. The pattern of energy development for the rapidly growing Anchorage area is not clear at this time. Formerly coal was the only fuel available for large-scale space heating and power generation. More recently both oil and natural gas have entered the market, and several hydroelectric projects have been completed. Additional major hydroelectric projects are being considered. The role that will be played by coal in this competitive energy market is uncertain. However I if coal is the fuel used in future power plants or industrial installations, the information contained in this report will be useful in indicating the quality of the coals that can be supplied and in selecting proper preparation techniques.

Jan 1, 1962

By H. E. Hilliard

The Bureau of Mines investigated hydrometallurgical procedures for concentrating precious metals from a mechanically processed metal fraction of obsolete military electronic scrap. Feed material for the leaching procedures described in this report was the high-tension-separated metal concentrate obtained as a fraction from mechanically processing partially stripped electronic units. Initial pretreatment with a 20-wt-pct-NaOH solution solubilized most of the aluminum. After washing, the resulting residue was incinerated to destroy any organics attached to metal particles. The incinerated residue was leached with 20-vol-pct H2S04 solution using two methods, countercurrent pressure and ultrasonic-aided leaching to solubilize the base metals, predominantly copper. Silver was recovered from the base metal leach residue using 50-vol-pct HN03, and gold contaminated with several percent palladium was recovered from the silver leach residue using aqua regia. The impure silver and gold plus palladium products represent about 1.5 wt pct of the high-tension-separated metal concentrate. Included is a three-step process evaluation study of mechanical processing of general electronic scrap and two hydrometallurgical procedures for leaching high-tension-separated metallic concentrates obtained from the mechanical processing step. Process evaluation concluded that only mechanical processing is economically viable.

Jan 1, 1985

By H. O. Poppleton

This Bureau of Mines study was made to investigate a possible method for selectively removing the Si02 component of silicate minerals and ores. Of specific interest were aluminum ores and zircon. Methods are described for removing Si02 from these ores as volatile silicon sulfides by treating the ore with sulfur and carbon; with sulfur, carbon, and a reducing gas; or with sulfur compounds and carbon. Comparative results are also given for the desilication of some of the ores with carbon alone to form volatile silicon monoxide. The silica component can be removed partially from bauxites at temperatures above the sublimation temperature of SiS (940° C) by treatment with carbon, sulfur, and methane; however, it is more difficult to remove the silicon from kyanite, manganese silicate, red muds from aluminum processing, kaolinite, lateritic nickel ores, and zircon. Complete desilication requires temperatures ranging from 1,100° C for bauxite to 1,450° C for zircon. Although the high temperatures required and the undesirable metal sulfides produced eliminate practical application of this method using present technology, the Bureau is reporting this data so that they will be available to future investigators.

Jan 1, 1974

By N. C. Tomoeda, W. D. Bensema, J. W. Adams

Measurements of surface magnetic field noise were made at various locations over the Geneva Coal Mine near Price, Utah, on June 12, 1973. The locations selected were on the surface over emergency locator beacons underground at depths between 350 meters (1150 ft .) and 488 meters (1600 ft .) . The surface terrain where these measurements were made was mountainous, and access was difficult. There were no power lines within several miles, and the weather was clear; therefore, the magnetic noise levels were about as low as will normally occur. Results of measurements of distant sferics indicate rather sharp cutoff frequencies below which broad- band, impulsive noise is attenuated. The mechanism of propagation for this noise above the daytime cutoff frequency of 3500 Hz and the nighttime cutoff frequency of 1700 Hz is deduced to be a waveguide formed by the D or E layers of ionosphere as an upper plane and the earth as a lower plane. The measurement systems used are similar to those used earlier. The technique is to record broadband, analog signals, digitize the data, and use a fast- Fourier transform to obtain spectral plots. This tech- nique is novel in that it can measure simultaneously all magnetic field energy within a limited portion of the spectrum for a limited time, and, after processing, reproduce the events occurring in that time interval in great detail .

Jan 6, 1974

By Thomas M. Barczak

This U.S. Bureau of Mines report describes methods to enhance the capacity, stiffness, and timber utilization of wood crib supports. Since stiffer supports minimize strata deflections that contribute to roof instability, efforts to maximize crib stiffness while maintaining stability through a wide displacement range should be a design priority. The stiffness and capacity of conventional crib designs, employing alternating layers of wood timbers that are loaded perpendicular to the grain, can be increased by increasing the interlayer contact area or by using higher strength wood. Contact area can be increased by using wider timbers or employing more timbers per layer. Concepts that provide parallel-to-the-grain timber loading will provide substantial increases in crib stiffness and capacity. Two concepts that utilize this principle are examined: (1) an original South African design that constructs wood cribs from preformed layers (mats) of timber where short blocks are oriented vertically between horizontal slabs; and (2) a design that employs full lengths of timber placed vertically in the interior of a conventional crib structure. These designs also provide more efficient timber utilization by providing greater support capacity per volume of wood used in the crib construction.

Jan 1, 2010

Provide better ventilation for mines by reducing air leakage around stoppings. Approach Most stoppings are constructed of concrete blocks and trowelled-on mortar and are not very airtight. Bureau of Mines research has shown that brushing on modified mortar containing fiberglass and/or other additives, that enhance strength and adhesion, minimizes air leakage around and through the stoppings. Airtightness is an important factor in building stoppings since an airtight stopping will provide for more efficient ventilation airflow and more cost-efficient use of the mine's ventilation system. How the New Technique Works After broken floor and rib material is removed, the stop-ping faces are covered with one or two coats of modified

Jan 1, 1982

By J. F. Smith

A series of studies of emissions from large coal-fired steam generators have included measurements of the concentrations of oxides of sulfur and oxides of notrogen. The sampling equipment, method of sampling, and analytical techniques used for processing of these samples are detailed. A method based on the precipitation of benzidine sulfate was developed for determining both SO3 and total oxides of sulfur in the presence of interfering acidic components in the stack gases. In addition, difficulties encountered with sampling and analytical techniques are also described.

Jan 1, 1968

By J. F. Barkley

The work covered in this report was done to meet the requests from many Government agencies for information on alleviating sludge difficulties in No. 6 (Bunker C) fuel-oil storage tanks. Accumulated sludge at times caused serious loss in tank capacities; pumps became overloaded or lost suction; strainers often required very frequent cleaning; fuel-oil heaters in some instances became fouled and inefficient; and gobs of sludge that passed the strainers interfered with good combustion. The requests also included questions regarding the usefulness in general of oil "additives" for preventing sludge and the relative merits of the many trade-named additives being marketed. Realizing that preventing such difficulties would result in substantial savings to the Government, an investigation was begun with the limited funds avail-able. Although various claims are made for No. 6 fuel-oil additives other than preventing sludge, only an investigation as regards the storage tank-sludge problem has been possible.

Jan 1, 1955

Capture airborne coal dust generated by a continuous mining machine to reduce workers? dust exposure and to improve face visibility. Approach Develop a low-profile dust collector system which can be mounted on the boom of a continuous miner. How It Works When coal is mined with a milling head continuous miner, a substantial amount of coal dust (respirable and non-respirable) escapes the dust suppression sprays at the cutter head. This can cause poor visibility around the cutting head and can expose the workers to high levels of respirable dust. A practical means of removing this dust is with a scrubber mounted directly on the mining machine. Under a Bureau of Mines contract, a low-profile, machine-mounted dust collector (MMDC) was developed to avoid adding extra height to the continuous

Jan 1, 1983

By Martin Hertzberg

The concept of limit burning velocities is being used to formulate a quantitative theory of flammability limits. Competing and complicating processes dissipate power from a combustion wave and quench propagation at some characteristically low limit velocity. Two earlier reports dealt with process (a), natural convection (RI 8127); and with process (b), conductive-convective wall losses (RI 8469). This report considers process (c), radiative losses, and process (d), selective diffusional demixing. The limit burning velocity for radiative losses is [(SU)c ~ e cp] It is normally not a significant process for premixed gas flames; however, for laminar flame propagation in a gravity-free environment, it is the only loss process present. Accordingly, limit velocities at zero gravity should be much lower than on earth, and premixed gases should be flammable over wider composition ranges. For highly emissive dusts, soot, or ash-forming flames, radiative losses are significant even under normal gravity conditions. Selective diffusional demixing is a complication that manifests itself in the form of cellular flame structures and wide gaps in composition between upward and downward propagation limits. It induces a burning velocity shift (?Su)d, causing the flame to behave as though it were richer or leaner than its initial composition, depending on whether the fuel or the oxidizer mole¬cule has the higher diffusivity. A simple pertubation analysis shows that the process generates stable cellular flames whenever [dsu] > 0, where ci is the concentration of the reactant with the higher diffusivity. The same analysis indicates that at the opposite stoichiometry, where [dcu] < 0, laminar structures are stabilized. A simple formula for the diameter of cellular flames is derived, which predicts that dcell should vary inversely with the product of the diffusivity difference Di -DJ, and the burning velocity slope [dc ]. Those predictions are in good agreement with the available data. Buoyancy forces for upward propagation induce flame front curvature, and hence buoyancy and selective diffusion are mutually supportive in upward propagation. Thus large gaps in composition between upward and downward limits are present in those composition domains where cellular flames are stable.

Jan 1, 1981

By Thomas M. Barczak

Longwall roof behavior is characterized by strata displacements in both the face-to-waste (horizontal) and roof-to-f1oor (vertical) direc-tions. The roof support structure provides resistance to this motion by translation of these displacements into vertical and horizontal support loading. Observations indicate that the shield reacts with both a vertical and horizontal force to uniaxial convergence (displacement). However, there are different magnitudes depending on whether the displacement is vertical or horizontal. This makes it possible to use supports as monitors of strata activity and loading. The Bureau of Mines examined this behavior using a linear elastic model of the support structure with two degrees of freedom. Vertical and horizontal load reactions were related to associated displacement actions of the strata. This was done by determining the stiffness of the shield under controlled vertical and horizontal displacement motions in the Bureau&apos;s mine roof simulator. This report provides example predictions of strata convergence and isolation of horizontal support loading due to vertical roof convergence using the linear elastic shield model. The report also examines efforts to determine strata behavior by direct measurement of support displacement.

Jan 1, 1987

By W. T. Abel

The Bureau of Mines tested 48 materials for their ability to absorb H2S from hot simulated producer gas (1,000°-1,500° F). The material found best from the standpoint of absorption capacity, durability, and amenability to regeneration was sintered pellets of 75 percent fly ash-25 percent Fe203. The performance of this absorbent under simulated and actual conditions is described. The effect of absorbent composition, absorbent temperature, steam content of the gas, and tar vapors and dust in producer gas is discussed.

Jan 1, 1974

By Lloyd A. Morley, Robert Stefanko

Before going directly to the analysis, it would be good to summar¬ize explosion-proof container approval methods. Both Magison (52) and Short (84) state that in general practice, the systems are certified for: 1. a rugged enclosure able to withstand an internal explosion but not allow explosively hot gases to escape, and 2. maximum surface temperature, with equipment operating inside, that will not ignite the surrounding atmosphere. Also, testing insures that any material in contact with the container surface will not be ignited by a hot spot. Associated with the first practice, the enclosures are inspected for: 1. a safe flange gap width, 2. a pressure increase during ignition, and 3. an hydrostatic pressure withstand level. The hydrostatic pressure level is almost always determined by a meas¬ured ignition-pressure test and is usually applied to prove the mechan¬ical design to some safety factor. Consequently, explosion-proof enclosure testing includes temper¬ature, permissible flame gap, and pressure. Specifications and prev¬ious research also can be similarly separated even though some interre¬lation exists between the flame gap size and internal enclosure pressure during an explosion. The Schedule 2G Sections applicable to these subjects are: 1. 18.2 Definitions; 2. 18.6 Applications;

Jan 1, 1974

To develop a magnetic levitation transport system that can reduce the cost and improve safety in transporting coal from the face of underground coal mines to the surface. Background Many conventional mining operations use conveyor belts to transport coal from an underground face to the surface of the mine. The Mag-Lev Transport System design replaces conveyor belts with magnetically levitated coal haulage containers moving through a dedicated pipe¬line. Cost estimates, based on current design data, show the Mag-Lev Transport System would have operating and capital costs that are less than or equal to those of an equivalent-capacity conveyor belt system. The safety hazards associated with conveyor belt systems include exposure to moving parts and pinch points, potential fire hazards due to mechanical friction, and the exposure of miners to respirable dust. These hazards would be eliminated or significantly reduced by this novel technology. Approach The Mag-Lev Transport System uses magnetic levitation technology that allows noncontact, frictionless conveyance of a levitated body within a dedicated transit corridor. The mag-lev technology utilizes two types of permanent magnets coupled with an electronic position control system to achieve noncontact levitation. Levitation is provided by neodymium-iron boron (NdFeB) magnets mounted in the base of the haulage containers and inexpensive ceramic-5 magnets located in the bed of the transit corridor. An electronic position control system is used to overcome the inherent instability of the repelling permanent magnets. Proximity sensors, a signal processing circuit, electromagnetic actuators, and fixed ferrous side rails are the major components of the positioning system.

Jan 1, 1994