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By Robert Stefanko

Roof bolting in coal mines has progressed very rapidly in the last decade, and today this method of support is in general use. There are many theories concerning the functions of roof bolts, but the importance of beam building is indisputable. Proper tension in the bolts minimizes shearing along bedding planes and creates a thick, competent beam from individually weak layers. Bolting must be accomplished immediately upon exposure of the roof, and bolt tension must be maintained if roof failure is to be prevented. Seams are being mined today with roof bolt support where conventional timbering was not effective1. The widespread use of continuous mining equipment was made possible by roof bolts which permit long supported spans free of obstructions.2 Since adequate anchorage is the key to successful bolting, better methods for determining the efficiency of anchorage are continually being sought. Attempts have been made to measure bolt loads, thus assessing anchorage efficiency by employing sensing devices between the bolt head and roof. 3,4,5 None of the techniques appears to be very accurate, and all have at least one serious deficiency.

Jan 5, 1962

By James E. Hoffmann

This paper reviews the chemistry of selenium and its compounds as it applies to the recovery of selenium from electrolytic copper refinery slimes. Based on this chemistry various processes for the extraction and recovery of selenium from refinery slimes are explained and developed. The optimum selenium technology processes is dependent upon many factors including copper refinery location, environmental and regulatory conditions, local markets for selenium or selenium chemicals, and other plant processes. For this reason there is no one best process but rather a variety of useful processes for winning selenium. Those which have demonstrated consistent utility in both ease of recovery and reliability are discussed in more detail. Recovery of selenium by Doré furnacing of slimes is the topic of a separate paper. The companies that have developed selenium extraction technology are not being cited in this paper for the following reasons: o Their current technology may be different o The actual inventor of a process is difficult to credit since many different organizations have pursued parallel inquiries in developing better processes. Finally, some selenium extraction processes have been omitted; not because they are unworthy of consideration but rather due to limitations of space.

Jan 1, 1984

By David Mitchell

THE production of fluorspar is one of the smaller nonmetallic indus-tries in the United States with a capital investment-about $10,000,000. Shipments from United States mines' in 1936 totaled 176,231 short tons valued at $3,111,268, an average price of $17.65 per ton. The United States produces about 40 per cent of the world's fluorspar, of which about 90 per cent comes from the Illinois and Kentucky deposits along the Ohio River.2 Further detailed information on the fluorspar industry in the United States is given by Hatmaker and Davis.28 Fluorspar is marketed according to the following relative quantities and specifications: Consump- Specifications, Per Cent Use Form tion in 1936, Per Cent CaF2 SiO2 Fe2O3 Metallurgical Gravel 79 +85 -5 or lump Ceramic,. Ground 10 +95 -3 -0,1 Acid Ground 11 +98 -1 The concentration of the coarser sizes presents relatively little diffi-culty, good recoveries being obtained with jigs and tables. However, sizes smaller than about 10 mesh cannot be successfully treated by ordinary gravity separation methods and so have been accumulating as

Jan 1, 1938

By Dilip K. Paul, Charles H. Jacoby

The economic importance of salt domes has been recognized throughout the world, primarily because of oil and gas accumulations on their flanks, and to a lesser degree, for the value of their salt and potash. Recently they have become of value as hosts for cavities used to store hydrocarbons. In the near future we believe that their main value will be a source of geothermal energy. Although tremendous effort has been expended on the understanding of the geology and physical characteristics of the strata intruded by salt domes, relatively little energy has been exerted in the comprehension of the salt dome itself. Salt domes have long been recognized as a geological heat anomaly. With respect to other sedimentary rocks, salt is a good conductor of heat. Expressing values in 10-3cgs units, sedimentary rocks vary from 1.0 to 8.0; metamorphic rocks from 5.2 to 8.4 and igneous rocks from 3.1 to 9.8. Rock salt in its pure form has a thermal conductivity of 17. Thus a salt dome can be expected to act as a conduit bringing heat vertically from deep within the earth's crust.

Jan 5, 1974

By John Nelson

AN OUTLINE survey of the economic outlook for the United States export trade in petroleum products resolves itself broadly into two general divisions; first, a consideration of our present position in this trade, and second, a discussion of the visible factors which promise to affect appreciable changes in the immediate future in that trade. The UNITED STATES PETROLEUM EXPORTS OF MAJOR PETROLEUM PRODUCTS 1925, 1926 and 1927 Gasoline, Naphtha, and Other Light Products 1925 1926 1927* Quantity (gal.) 1,286,787,796 1,784,154,802 1,851,494,190 Value $197,491,588 $263,199,938 $214,721,652 'Illuminating Oil, Kerosene 1925 1926 1927* Quantity (gal.) 885;136,041 924,680,979 827,162,280 Value $84,699,724 $100,352,877 $80,358,082 Gas and Fuel Oil 1925 1926 I 1927 Quantity (gal.) 1,365,358,988 1,449,688,394 1,815,130,464 Value.... ? $49,040,024 $45,354,108. .. $50,343,031 Lubricating. Oil 1925... ....1926 .. 1927 Quantity .(gal.) 402,572,584 388,767,055 403,369,512 Value $90,596,671 $86,414,621 $88,926,815

Jan 1, 1928

By John G. Hall

The unstable metal market during 1949, with resulting lower metal prices, has focused every mine operator's attention on the problem of reducing operating costs. Improvement in mining methods, use of modern mechanical mining equipment, and increasing the efficiency of the labor force are the tools with which we will have to work. Careful planning is necessary to coordinate all phases so that no one phase is overdone. A mine may become over-mechanized if, for instance, capital charges against new equipment exceed the savings in labor costs, or where a large enough tonnage is not produced. The cooperation of labor is essential to any mechanization program. There have been too many instances where mechanization and improvements have done nothing more than make up for a decrease in labor efficiency, thus bringing the production of labor back to its old standard. The operator has gained little and labor has gained only a "softer job." In any mechanization program there are gains to be had by both the operator and labor. By the efficient application of modern equipment and improved mining methods the operator should gain by decreased costs, and labor may profit by receiving a share of these decreased costs.

Jan 8, 1950

I. THE ENERGY CRISIS STILL EXISTS A. ALTHOUGH IMMEDIATE SHORTAGE IS NOW ALLEVIATED BY: 1. Increased imports through lifting of Arabian embargo; a. Imports were 6.5 million bpd during the week ended January 17, or 1.3 million bpd higher than last year. b. 1.7 million bpd higher than March '74. 2. Decreased demand resulting from higher prices and conservation. a. January 1975 demand was 17.9 million bpd, 0.1 million bpd lower than January 1973 and … b. 2.0 million bpd, or 10% under originally projected demands for January 1975. c. Gasoline (excluding tax) went up 59% from 27d/gal in August 1973 to 43c/gal in September 1974. d. Gasoline demand for January 1975 was 6.3 million bpd, 0.1 million bpd higher than 1973 but 0.7 million bpd ( 10% ) under projected demand. 3. Increased crude and major product inventories. a. January 17, 1975 crude and major product inventory was 794 million bbl, 99 million bbl higher than the same date in 1973. b. 105 million bbl increase since April 12, compared to only 38 million bbl increase during the same period in 1973.

Jan 5, 1975

By C. S. Barrett

Measurements of impact hardness of ß-brass are reported for a wide range of temperatures. Abrupt softening is observed when temperatures are raised above 425ºC, accompanied by abrupt widening of deformation bands in the deformed samples. Current theories of these effects, and of the lack of twinning, are discussed. HARDNESS1 and flow stress2 of a sample of ß-brass at room temperature depend upon the temperature from which the sample is quenched. It is believed that the state of order in the superlattice is responsible for this dependence—not the order within individual domains, which reaches near-perfection during the quench from any temperature, but the size of the domains which is presumed to be a minimum in the hardest samples, those quenched from temperatures near the critical disordering temperature of 468°C. Measurements of impact hardness made over a range of temperatures and microstructural studies of samples deformed both rapidly and slowly over a range of temperatures, reported herein, should be of aid in reaching a more complete understanding of the underlying factors controlling the properties of the disordered body-centered-cubic material and the ordered material. It appears that such data have not

Jan 1, 1955

By I. L. Barker

ALTHOUGH valuable information has been pub-lished on the important problems of slag losses with which every copper metallurgist has to contend, a great deal of money is still being wasted in copper smelters all over the world, through metal being irretrievably lost in reverberatory slags. When smelting a relatively low-grade pyritic concentrate together with a proportion of direct-smelting oxi- dized ore, as is done in Oroya, slag volumes are of necessity high, and even a relatively clean slag, say of 0.5 pct Cu, means a loss of almost 4 pct of all the copper charged, or over $1,000,000 annually at present output and prices. While it is known that such losses can often be reduced by allowing the slag time to settle, with or without addition of a reducing agent such as coal or pyrite, the facilities for such treatment are not always available in a plant of old design working to capacity under severe space limitations. Nor is it easy under such conditions to run large scale tests which may endanger the smooth flow of production for considerable periods without yielding

Jan 1, 1958

By David R. Mitchell, R. B. Hewes

MANY processes for cleaning coal that are in use depend primarily on physical properties of coal and refuse other than specific gravity and surface conditions relating to froth flotation. These properties are' shape, coefficient of sliding friction, resilience, friability, magnetic susceptibility, and electrical conductivity. In many of these processes specific gravity does have some effect and many separators are designed to utilize more than one of the physical properties cited. Although the processes described herein do not have a widespread application, yet for specific coals and specific conditions, they are economically important. A problem confronting many coal-mining districts is the marketing of the slacks or screenings and dust passing the final sizing screens. Proc¬esses in commercial use installed primarily to increase the form value, and hence the market value, of these slacks and dusts include briquetting, packaging, and low-temperature carborization. MECHANICAL PICKERS Machines utilizing shape, frictional resistance, and differences in resilience of coal and impurities are usually called mechanical pickers. They require a closely sized feed, therefore their use is confined to the pea, nut, and egg sizes. Various types of these devices are described by Berrisford, 1. 2 Taggart, and Yeele.

Jan 1, 1943

By Rudolf Bernhard

STATIC soil investigations with more or less heavy loads and extensive borings do not always have efficient results; also, they are very expensive. The new geophysical method of dynamic tests described herein is simple and cheap and avoids several disadvantages of the routine investigation, thus forming a useful supplement to the older methods and even at times replacing various static tests. The fundamental principle of dynamic soil tests consists in the appli-cation of artificial vibration. The technique employed is essentially geophysical in nature and in some respects is akin to seismic studies. Artificial vibration may be excited by centrifugal forces resulting from eccentrically supported rotating masses. The reactions of soil and structures caused by these vibrations may be measured. Their dynamic constants, such as amplitudes, phase speeds, damping, reflection, and interference effects, can be investigated. This geophysical method has been used for several years with increasing success. The results of these tests, summarized at the end of the paper, indicate that this method opens a new field for the practical engineer in investigating soils (capacity and formation), foundations, dams and structures, and especially buildings that must withstand earthquakes.

Jan 1, 1938

By R. S. Burns, J. G. Erskine

The performance of the nine 5.5 m diameter x 6.4 m mills (18 x 21 ft) initially installed at Bougainville Copper Ltd. did not meet the laboratory and pilot plant derived design expectations as measured by Bond Work Index. During the post-commissioning period, inefficient grinding of coarse material resulted in a build-up of large circulating loads and led to reduced throughputs because of pump and cyclone overloading. Installation of larger pumps and cyclones and development of an improved circuit control philosophy alleviated materials handling problems and permitted higher tonnages to be attained. Since 1977, plant throughput has been increased by installation of three additional mills. These are 0.9 m (2.9 ft) longer than the other nine and have a higher capacity. Developments in classification and mill speed-up, together with a finer ball mill feed size and substantial improvements to mill availability (99% in 1982) have further increased plant capacity. There is a continuing emphasis on improving grinding circuit efficiency in terms of throughput/grind. Current development work includes trials of graded ball charges, different liner profiles, and assessment of scalping/regrind proposals.

Jan 1, 1985

By George B. Clark, Edward E. Hornsey

Pulses from large underground explosions which traverse the rock beyond the "fracture" and "plastic" zones do not behave as a spherical elastic model. Observed attenuation is greater than that predicted by the elastic wave equation, and the pulse form changes in a different manner, i.e., it usually lengthens with the first power of the distance. To more clearly define a mathematical real earth-wave model, detailed analyses of the spherical elastic and the Voigt viscoelastic models have been made, and results compared with observed wave forms from large confined chemical and nuclear explosions. TRANSIENT SPHERICAL ELASTIC WAVES Scope of Investigation Transient elastic spherical waves were investigated in detail. However, an elastic model is not, in general, an exact representation of wave propagation in rock. An understanding of transient elastic waves is desirable for gaining insight into explosive-generated wave phenomena because it can be employed for comparison of more complex and realistic models, such as the Voigt model, or others which may simulate real earth waves. The study was concentrated primarily on the peak values of the radial wave parameters : displacement, particle velocity, acceleration, stress, and strain.

Jan 1, 1972

By J. McD. Porter

In many of the old placer-mining districts are still to be found large tracts of gold-bearing gravel not suitable to be worked with a dredge, because the bed is too shallow or the gulch too narrow. Frequently there is not enough grade to handle the gravel successfully by ground-sluicing or a bedrock flume, or it contains too many boulders to be worked succeeefully with the ordinary hydraulic pipe or tube elevator. In southwestern Oregon, two practical placer-miners named Ruble, after working for years trying to make money out of placer-ground coutaining many large boulders, invented and patented a hydraulic elevator of an entirely new type, and one that has been found to work very successfully in flat ground and in gravel containing many large boulders. It is a very simple contrivance. A few years ago I acquired the property near Pierce City, Idaho, known as the American placer-mine. Various attempts had been made to work this ground. A bed-rock flume had been installed by one company, an Evans elevator by another, and still other methods were tried on a smaller scale. All were

Jan 1, 1910

By S. J. Hubbard, S. D. Michaelson, A. W. Last, B. H. Ensign

Of the seventeen western states, five-Arizona, Utah, New Mexico, Montana, and Nevada-produce about 90 pct of this country's primary copper. All seventeen of these states occupy 60 pct of the nation's land area but receive only 25 pct of the country's total precipitation. Seventy percent of this precipitation returns directly to the atmosphere through evaporation and transpiration, leaving very little for ground reservoir recharge or immediate domestic, agricultural, or industrial use. With so limited a supply available for all, competition for water rights among users is severe. The result does not always permit using the limited supply to produce the most valuable end product. Most of industry and much of agriculture can shop around for suitable operating locations. Where water is critical to their purposes, they can and do locate in areas where the needed amounts are available. Such is not the ordinary lot of the mining industry, which must locate in the area of the deposit it is planning to mine and concentrate. In the case of copper this happens to be, for the most part, right in the heart of the semi-arid regions of the West.

Jan 7, 1960

By J. C. Marquardt L., J. A. Bratt, J. P. Hunt

The Quebrada Blanca copper/molybdenum prospect lies on a dissected plateau in the high Andes of Northern Chile. The Superior Oil-Falconbridge Group began exploration of the Property in 1977 under a joint venture foreign investment agreement with the Chilean government. Quebrada Blanca is a relatively high grade secondarily enriched porphry copper deposit. Primary mineralization occurred 38 million years ago and accompanied quartz monzonite intrusive. Early disseminated Primary mineralization was followed by hydrothermal mineralization, mineralized breccia, and post-mineral faulting. After supergene enrichment Quebrada Blanca was buried under late Tertiary gravels and then partially re-exposed in Quaternary time. During the past five years, a successful exploration program has developed an open-pit mining reserve, provided samples for bulk metallurgical testing, and located more than adequate supplies of water for future operations. The main orebody is amenable to conventional metallurgical treatment and contains more than 400 Mt (441 million st) of recoverable open-pit ore at about a 1:1 overall stripping ratio. The average millhead grade during the first six years of operations will exceed 1.5% Cu, plus recoverable molybdenum values. Several hundred million tons of additional reserves are available in the surrounding districts

Jan 1, 1984

By K. Winterton

The effect of a near-saturation unidirectional magnetic field was to decrease slightly the endurance life in Armco iron in the annealed condition. This is expected since the energy-absorbing mechanism associated with domain wall movemenfs is inhibited bv the strong field. THE factors determining failure under dynamic loading are not yet clearly recognized. One of the properties of a metal which might be thought to influence fatigue life is its damping capacity. Foppl1 conducted an alternating torsion test at a frequency of 700 cpm continuously for a period of 3 years, without the test piece breaking or showing any sign of deterioration after 1100 Million cycles of stress; the rate of dissipation of energy was sufficient to maintain the test piece at about 100°C above the ambient temperature. cazaud2 concludes from this, and others follow him, that ('the capacity for dissipation in the form of heat by internal damping is unlimited" and that therefore "damping is not directly related with fracture by fatigue." Future work may necessitate qualification of this rather uncompromising view. It is shown later that in all

Jan 1, 1960

By R. W. Nash, A. E. Schwaneke, V. R. Miller

The Bureau of Mines developed a detector for controlling sorting devices to separate the copper-bearing fragments from the barren portion of Michigan native copper and western prophyry copper ores. A successful sorter could be used to preconcentrate the ore and eliminate costly hoisting or hauling of waste. An induction balance unit was developed and used in sorting tests on crushed sized - 2.5 + 1.3-cm (- 1 + 112- in.) ores from the Kingston (0.9% Cu) and Centennial (1.6% Cu) mines of Upper Michigan. Concentrates of 4.0% and 7.5% Cu, respectively, were obtained at recoveries of 85 and 80% of the copper in the feed. Eighty percent of the sorted ore was rejected as tailing. Sorting larger fragments improved the separation efficiency. Tests on - 10+ 5-cm (- 4 +2-in.) sized Kingston (1.6% Cu) and Centennial (2.1 % Cu) ore samples yielded concentrates of 4.3 and 4.5% Cu, respectively, with corresponding recoveries of 92 and 91 %. A bout 60% of the sorted ore was discarded as tailing. Porphyry copper sulfide ores also responded to electronic sorting but at a lower separation efficiency. Sorting response was affected by the degree of segregation.

Jan 1, 1979

By William Newton Best

Oil burners, oil furnaces, and methods of installation, have been the subject of many articles, but information concerning oil-burning systems, based upon scientific principles, is still in great demand, especially in the manufacturing districts of our country. Fuel oil, as it is termed (this being the residuum from oil refineries), has for many years been of great service to our manufacturers, and has justified its popularity not only by producing a superior manufactured product, but by turning out approximately 50 per cent. more product than can be made with coa1 fuel under like conditions. To install a system requiring only an oil-storage tank, a small pump, and an oil-supply main with numerous laterals leading to the various burners, furnaces, boilers, etc., is a comparatively simple matter; and, because fuel oil is very volatile, it is not necessary to heat it, even during the winter months in a very cold climate. Furthermore, only a small amount of power is required to atomize fuel oil, this often being done by a positive pressure blower, or by a mechanical burner. An analysis of fuel oil, together with that of various other liquid fuels, is given in Table I.

Jan 1, 1915

By H. F. Haller

COLUMBIA-SOUTHERN'S Barberton limestone mine, 8 miles southwest of Akron, Ohio, is a million-ton-per-year producer from a depth of over 2200 ft in a district where other underground mining at this depth is unknown. Mining extracts 46 of the top 51 ft from a formation of Devonian limestone discovered by drilling in the 1890's. The same drilling revealed extensive salt deposits below the lime- stone, which led to the location of the chemical plant at Barberton as a division of the Pittsburgh Plate Glass Co. in 1899. Soda ash was the principal product of the plant, and as production increased the demand for limestone increased. Columbia's first attempt to secure a reliable all-weather source of stone was the development of a quarry at Zanesville, Ohio, in 1919. Zanesville production eliminated some of the stock- piling required by the use of Michigan stone, avail- able only during the lake shipping season. Stone from some Zanesville horizons, however, was found to be more suitable for cement production than for soda ash, and rail transportation remained an important factor. As demand continued to increase, plans were made to develop the Barberton deposit.

Jan 12, 1954