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By C. W. Dunham

DESIGN of the structures for the Morenci Reduction Works involved many interesting problems. Naturally, the chief purpose of these structures is to house and support the equipment and other things necessary for or incidental to the conduct of production. hence most of the features of the design were developed to suit these particular conditions; however, several are so generally applicable as to warrant description.

Jan 1, 1942

By Harold Markus, Gerhard Derge

THE first paper1 of this series described a technique of careful surface preparation by means of which reproducible results may be obtained from potential measurements of the behavior of tin in carbonate solutions with a pH range from 8.4 to 11.2. It then went on to establish the behavior of pure tin electrodes under these conditions and showed that the metal remains active at all times, though the steady potential attained after several hours decreases from I.I2[t] volts at a pH of 12.6 to 0.6 volts at a pH of 8.4. This behavior may serve as a norm with which all other data can be compared. In the second paper,2 small amounts of other anions were added to the carbonate solutions and the conclusion was reached that the common impurities encountered in alkaline materials packaged in tin do not increase corrosion. In fact, in some cases these anions may actually promote the formation of protective films. The present paper rounds out this survey by presenting data on the influence of cations added to the carbonate solutions, as well as the effect of alloy additions to the tin. In many cases the potential data are supplemented with weight-loss measurements. Information is also presented on the effects of some additional anions, the influence of gases above the electrolyte, the behavior of high-purity tin, and the effect of atmospheric oxidation on the corrosion resistance of the above-named alloys. Analysis of the entire body of data discloses some general rules applicable to corrosion in carbonate solutions. The experimental methods used are the same as those previously described. EXPERIMENTAL DATA Cations.-The carbonates of the cations K+, Li+, NH4+, which are soluble, were studied in the same way as the anions, by adding 0.01 mol of the metal carbonate to one liter of 0.2 M sodium carbonate solution, pH 11.2, or to 0.1 M sodium bicarbonate, pH 8.4. The other metallic carbonates are only slightly soluble, of the order of 0 7-3 mols per liter or less, and the sodium carbonate solutions were saturated by adding excess reagent several days before the experiment, shaking frequently, and filtering just before use. The chemicals were c.p. grade in each case except the indium salt. This salt was prepared by solution of the metal in hydrochloric acid and precipitation by addition of Na2CO3. These cations may be divided into two classes, according to their effect on the potential behavior of the tin: (I) normal, (2) passive. To offer a basis of comparison, curves I of Figs. I and 2 are given to illustrate the behavior of tin in carbonate solutions saturated with CaCO3. These curves are the

Jan 1, 1941

By Nathaniel Hen

IN the United States, in the 2 1/2 years since the rescinding of the wartime order closing gold mines, conditions have not yet returned to normal. Shortages of man power have prevented some mines from operating at all, and most of those in operation are still at reduced capacity. This fact, combined with shortages of materials, the high cost of supplies and labor, high tax rates, and a fixed price for the product have made the past years rather rough ones for gold producers. In foreign countries conditions are rather similar. In Canada several new mines are coming into production and some others are enlarging. Costs have not increased as much as in the United States and gold production is being encouraged. Recently a bonus of 20 per cent on increased production has been proposed. In South Africa, where gold mining is of major importance in the national economy the industry is also in a favored position with government; new discoveries of major importance there will markedly increase the gold output. Demand for labor is rap-

Jan 1, 1948

By Harold B. Goldman, Don Reining

The sand and gravel industry is the largest nonfuel mineral industry in the nation. In 1981, the production of sand and gravel totaled 755 million tons valued at $2.3 billion. California, which leads the nation with more than 110 million tons, together with Alaska, Texas, Michigan, and Ohio, account for 36% of the total production in the nation (Table 1). In commercial usage, sand applies to rock or mineral fragments ranging in size from particles retained on a No. 200 sieve (0.074 mm openings) to those passing a No. 4 sieve (4.76 mm openings). Gravel consists of rock or mineral fragments larger than 4.76 mm, ranging up to 88.9 mm (3 ½ -in.) maximum size. The construction industry consumes 97% of the sand and gravel produced; the remainder is sand used for specialized products such as glass (see the chapter on "Silica and Silicon"). Utilization The building industry uses sand and gravel chiefly as aggregate in portland cement concrete, mortar, and plaster; the paving industry uses sand and gravel in both asphaltic mixtures and portland cement concrete. Aggregate is commonly designated as the inert fragmental material which is bound into a conglomerate mass by a cementing material such as portland cement, asphalt, or gypsum plaster. Portland Cement Concrete Aggregates Portland cement concrete consists of sand and gravel surrounded and held together by hardened portland cement paste. Concrete mixes commonly contain 15-20% water, 7-14% cement, and 66-78% aggregate. Sand and gravel used as concrete aggregate have to meet many requirements (Goldman, 1956). Premature deterioration of concrete has been traced in many instances to the use of unsuitable aggregates. Asphaltic Aggregate Asphaltic mixtures used predominantly for paving consist of combinations of sand, gravel, and mineral filler (material finer than 0.003 in.), uniformly coated and mixed with asphalt produced in the refining of petroleum. Except for the addition of mineral filler, sand and gravel used as asphaltic aggregate must meet the same general physical requirements as materials used for portland cement concrete aggregate. General Requirements of Aggregates Construction aggregate has many requirements that are difficult to meet if only unprocessed material from natural deposits is used. Suitable material is composed of clean, uncoated, properly shaped particles which are sound and durable. Soundness and durability are terms used to denote the ability of aggre- [ ]

Jan 1, 1983

By J. B. STEWART

T HE position of each hole of any series of holes was carefully located by the surveyor, plotted in plan and elevation, and numbers assigned to them. The second series was staggered halfway between the first and so on for each succeeding series. Two and a, half to three months was frequently required to grout a series of holes calculated to insure safety for sinking a distance of 10 meters or say 33 ft. Naturally the initial operation called for drilling and grouting two series of holes but thereafter each sinking campaign required only one series of holes as shown in Fig. 8. The pump handling about 75 gal. per minute corresponds to 46 tons of grout or 6 tons cement delivered as a fair over-all average for the 24 hours. Thus 600 to 800 tons of cement was used for a single section of 33 ft. depth of shaft. One campaign used nearly 1100 tons of cement. Some holes were effectually sealed with as low as 30 tons, while many required 60, and some 80 to 90 tons.

Jan 1, 1926

By F. Ernest Brackett

Much new data on the flow of gases have been discovered by recent experiments by the United States Bureau of Mines and others. Although additional investigation is still desirable, the information now collected seems sufficient to attempt a tentative coördination of the friction factors. This study is confined entirely to fluid friction when the density throughout the duct is so nearly constant that it may be so considered. In the subsequent discussion the following notation is used: v = mean velocity of fluid in duct, feet per second. v' = mean velocity of fluid in duct, meters per second. R = hydraulic radius of duct, feet. R' = hydraulic radius of duct, meters. S = the hydraulic slope. P = pressure absorbed by friction, pounds per square foot. p = pressure absorbed by friction, pounds per square inch. p' = pressure absorbed by friction, kilograms per square centimeter. A = sectional area of duct, square feet. O = perimeter of duct, feet. L = total length of duct, feet. L' = total length of duct, meters. d = diameter of a cylindrical duct, inches. w = density of the fluid, pounda per cubic foot. g = specific gravity of the fluid compared with water = w % 62.4. C, k and B, coefficients for formulas using English measures. C' = metric coefficient, v' = C'R'S. n = coefficient of roughness for English or metric units. The basic formula for the flow of all fluids at constant density appears in the three following forms, which may be denominated: (a) The slope formula, v = CRS (b) The ventilation formula, " n = (c) The pipe formula, C is Kutter's coefficient, which is extensively applied to the flow of water in ducts and channels of all kinds; E is Atkinson's coefficient, used principally with air in ventilation problems; B is a coefficient conveniently adapted to studying the flow of water, gases and vapors in pipes. 312

Jan 1, 1927

By William Romanoff

IN AN ARTICLE on "Recovering Smelter Dust and Oxide," published in the Engineering and Mining Journal (Vol. 131, No. 2), the authors briefly described some dust-recovery equipment and its operation at a secondary-metals brass-smelting and refining plant. A description of our experience in overcoming certain operating difficulties may prove of interest or value to those who are confronted with some of the same problems or who should equip their furnaces with dust-collecting equipment. The dust loss from reverberatory smelting and refining of brass con¬sists largely of zinc, with smaller percentages of lead, tin, and copper in the order named. At the Kramer plant, the fume discharge from the two stacks amounted to 3 to 4 tons of solids per day, making a dense smoke. With dust equipment in operation, the discharge from the stacks is invisible and approximately 2500 lb. of zinc and other metals is recovered daily thereby from each furnace operating.

Jan 1, 1933

By Edmund M. Warner

Any city dweller who has walked alone along a remote mine passageway has to be impressed by the eerie silence-the total absence of noise except for one's own breathing and scuffing of boots on the bottom. An underground mine can have tremendous contrasts, from complete silence to the ear piercing clatter of percussion drills working in the mine roof. Noise in underground mining machines is both useful and detrimental. Without characteristic noises that are recognizable to miners, operators would have a more difficult job operating their machines. Noise serves as a warning of approaching machinery, and changes in noise give indication that breakdowns may occur.

Jan 1, 1979

By Arthur W. Ruff

One of the major challenges to management in the mining industry today is the establishment and maintenance of positive and dynamic programs for cost control and cost reduction. To meet the challenge, management must have a good cost system. There are various types of cost accounting systems in use today: some companies check their, performance by comparing the costs incurred during one period with the costs incurred during previous periods, while others compare the current costs with estimated costs which the company considers desirable. A third type of system is a standard cost system which provides predetermined allowances for the various cost elements and operating activities. Such a system, based on sound standards, can be established to fix responsibility for cost performance in each segment of the operation; recognize the impact of volume or rate of activity by establishing a standard volume and evaluating departures: take into consideration fixed and variable costs and their dissimilar behaviour at varying levels of operations: and provide consistent and equitable yardsticks for measuring performance.

Jan 11, 1962

By S. E. Craig

UPON entering the Uranium Field it was a pleasant surprise to find almost absent two factors that have always been a problem to the lead-zinc miner: 1) milling cost per ton, and 2) transportation cost to the milling site. Another interesting condition was the fixed price for the product. Under such conditions it seems rather simple to calculate the economics of a mining venture when grade and tonnage of a uranium ore deposit is known. That is assuming, of course, there is a market for the ore. It has been quite generally assumed by operators that a guaranteed price carried with it a guaranteed market, a subject about which there has been a great deal of discussion in the past several months. The fixed price for uranium in crude ore, calculated to U3O8, varies only slightly in value per pound from rather low grade ore to rather high grade ore. It is by taking advantage of this slight variation in price per pound in certain ranges that miners and shippers may increase substantially the monthly returns from ore shipments.

Jan 7, 1958

By J. W. JESSUH

TO certain people the name of Northern Rhodesia brings only a vague recollection of a distant country somewhere in Africa; to others, it means a big game territory and the opportunity for excellent shooting; to some, a land of sunshine and peace; but to mining men the name signifies the land where the latest discoveries of copper ore are astonishing the mining world and bid fair, in a few years, to make Northern Rhodesia one of the largest copper- producing countries. There is a fascination about this part of the globe that is somewhat similar to southern California, and at the same time there is that feeling of mystery peculiar to a tropical climate. Perhaps it is the isolation, the fear of wild animals, or the influence of an undefinable something which cannot be expressed.

Jan 1, 1931

By H. W. Maynor, C. J. McHargue

DURING the course of an investigation of materials suitable for use as thermocouples at elevated temperatures by one of the authors, several nlolybdenum-rhenium alloys were prepared. Micrographs of an annealed alloy containing 25 pct Re (intended concentration; analysis not obtained) showed a number of twins, Fig. 1, suggesting a face-centered cubic structure. This note reports the structure and recrystallized wire texture of an alloy containing 25 wt pct Re. Alloys were prepared from 99.9 pct Mo (Fansteel Metallurgical Corp.) and rhenium obtained from the University of Tennessee (purity unreported). Powders were combined and briquetted at 56,000 psi and sintering was carried out at 2400°C for 5 hr in vacuum. Ingots so prepared were swaged at 982.2" to 1037.8oC into wires 0.036 in. diameter, a reduction in diameter of 85.6 pct. These wires were vacuum-annealed 1 hr at 2000°C. A North American Philips 114.59 mm powder camera and nickel-filtered copper radiation were used for structure determination. For the texture determination a Laue-type camera was used with zirconium-filtered molybdenum radiation and, because of the high background, aluminum foil was mounted next to the film. Exposures were taken with the wire perpendicular to the X-ray beam and tilted by 10". It was found that the X-ray pattern could be indexed on the basis of a face-centered cubic structure. Because of difficulties associated with obtaining a good X-ray pattern for this material, accurate parameter determinations were not made. An indicated parameter value of 3.70A was obtained. The X-ray data are given in Table I. The annealed wire texture was observed to be a sharp [111] texture. The spread about this fiber axis was k8" at the surface of the 0.036 in. wire. The annealed wire textures of aluminum have been reported as retention of the [Ill] deformation texture for anneals below 500°C and a new [1121 texture for anneals above 600°C.1 In copper wires, with a [Ill] plus [loo] deformation texture, results indicate a retention of this texture for annealing at lower temperatures and new components or the disappearance of components for annealing at higher temperatures.' The presence of the strong [I111 texture in the molybdenum-rhenium alloy after a 2000 °C anneal suggests that the deformation texture was the same. Acknowledgment The wires used in this study were prepared and heat-treated at the Institute for Atomic Research, and Ames Laboratory, Iowa State College, and the authors wish to express their thanks to the Institute for allowing the use of the material and permission to publish the results.

Jan 1, 1954

By P. J. Dean

This Paper contains a comprehensive survey of the known electron-hole radiative recombination mechanisms in the family of III-V compounds. Because of space limitations, the luminescence properties of each III- V compound are not reviewed separately and exhaustively. Instead, the different known types of recombination processes are discussed in turn and exemplified with reference to the III- V compound in which they were first recognized, or are best understood. Electron-hole recombinations usually occur predominantly at impurities or lattice defects either introduced de1iberately or inadvertently present, but radiative intrinsic interband electron-hole recombinations, which occur in perfect crystals, have been observed. Recombination processes which involve the participation of impurities or lattice defects ("extrinsic" recombinations) considered include transitions in which a) free carriers recombine with carriers trapped at impurities ("free to bound" transitions) , b) electrons bound at donor impurities recombine with holes trapped at acceptor impurities ("donor-acceptor pair" recombinations), C) excitons bound to charged or neutral donor or acceptor impurities recombine radiatively (both "resonance" and "two-electron" "bound exci-ton" transitions have been observed), d) excitons bound to neutral donor or acceptor impurities recombine non-radiatively (an example of an "Auger" recombination), and e) excitons bound to impurities with the same number of valence electrons as the host atom which they replace ("isoelectronic " traps) recombine radiatively. In addition, Auger recombination processes involving one or more free carriers have been observed. These extrinsic processes all involve impurities which are present as point defects. Some apparently well-authenticated examples of the recombination of excitons bound to complex impurity-lattice defect centers including nearest-neighbor donor-acceptor pairs are also discussed. Identificalions of the transitions involved in stimulated emission from the direct gap III-V compounds are briefly reviewed. Although the examples of these recombination mechanisms are selected from the III-IV compounds ia this review, these processes have quite general relevance in semiconducting crystalline solids; irrdeed most of them have also been identified in the 11- VI compounds and elernental semzconductors. THE development of crystal growth and purification techniques in recent years and concurrent advances in the understanding of physical processes in solids has accelerated the development of a wide variety of solid-state electronic devices of proven utility. These de- vices are generally used for switching or amplifying operations in electrical circuits. Most solid-state circuit elements are very photosensitive. This photo-sensitivity is generally undesirable and the single-crystal chip forming the active portion of the solid-state device is mounted in an opaque container. The photosensitivity is made use of in phototransis-tors and photodiodes, which are among the most sensitive detectors of electromagnetic radiation particularly in the near infrared.' In these devices, light is converted into electrical power. The solid-state lamp utilizes the inverse effect, namely the conversion of electrical power into light. There is an increasing tendency to use single-crystal diodes rather than the earlier electroluminescent cells in which the active material is present as a powder embedded in a suitable dielectric.' The radiation is emitted at a rate far in excess of the thermal equilibrium rate for the frequencies and temperatures involved; i.e., luminescence occurs. The development of practically efficient solid-state lamps is at an early stage compared with solid- state circuit elements or even photodetectors. Considerable progress has been made in recent years, however.3 The present review is devoted to a survey of the radiative recombination processes in the semiconducting compound crystalline solids formed from elements in groups I11 and V in the periodic table. These materials exhibit the full range of known recombination processes in solids. In fact many of these processes were discovered in 111-V semiconductors. Nonradiative recombination processes, which control the lutninescence efficiency, are also discussed. Luminescence is efficiently excited in semiconductors through processes which produce large excess concentrations of free electrons and holes in the energy bands of the crystal. Transitions induced by lattice defects or impurities usually predominate in the recombination process. By contrast, luminescence in the conventional fluorescent lamp is excited by optical absorption at the luminescent impurity center itself (the activator) and/or at a second type of impurity center (the sensitizer). This latter type of photoluminescence process, occurring in doped ionic crystals with wide band gaps, is outside the scope of this review.4 I) ENERGY BAND DESCRIPTION OF ELECTRON STATES IN CRYSTALS The energy band description of the energy states available to an electron in a crystal forms the basis of our understanding of the empirical division of crystalline solids into metals, semiconductors, and insulators in accordance with their electrical and optical properties.' Nonmetallic crystals have a finite energy gap between the highest energy band which is

Jan 1, 1969

NORTH AMERICA ALASKA Anchorage.-Strandberg, H. College.-Barber, R. J. Burns, W. T. Henricksen, R. Henton, H. M. Joesting. H. R. Comet.-Albertson, F. E. Douglas.-Cahill, W. E. Carlson, L. Fairbanks.-Andregg. J. N. Coats. R. R.

Jan 1, 1938

By R. A. Bergman, C. J. B. Fincham

THERMODYNAMIC properties of many high-temperature systems containing sulfur, such as slags, metal sulfides, and solutions of sulfur in liquid metals, have been studied by means of equilibration with known gas mixtures.'" This method presupposes a complete and accurate knowledge of the thermodynamic data for all possible components of the gas phase at high temperatures. However, a survey of the data available up to 1952 on the thermodynamics of gaseous sulfur species and compounds, by Richardson and Jeffes,' showed that there was considerable uncertainty in the values of the free energies of formation of S, SO, HS, and CS. In many cases, this uncertainty made it impossible to decide whether or not these species would form a significant proportion of the sulfur present in the gas phase in any given system. After the review by Richardson and Jeffes had been published, St. Pierre and Chipman6 measured, by an indirect method, the free energy of formation of SO. This also enabled a clear choice to be made among the three possible spectroscopic values for the dissociation energy of S2 into atoms10 thereby determining the free energy of formation of S from S2, and fixing the free energy of formation of HS more accurately" The main purpose of the present investigation was to measure the free energy of formation of CS, which was still in considerable doubt. For example, at 1600°C, it could be estimated to be +6 +25 kcal per mole,* most of the uncertainty being in the * Based on the dissociation energles of CS6 and S2,5 the heat of sublimation of graphite, and, the assumption that the entropy of formation of CS is the same as that of CO. value of the dissociation energy." A secondary purpose of the investigation was to determine more accurately the equilibrium sulfur pressures over dilute solutions of sulfur in carbon-saturated liquid iron. General Method Dilute solutions of sulfur in liquid iron, saturated with carbon, were brought to equilibrium at 1600" and 1800°C, with known gas mixtures consisting, initially, of A and CS2. After equilibrium had been reached, the melts were quenched and analyzed for sulfur. In the high temperature region of the furnace, an equilibrium was set up between the various possible sulfur species and compounds in the gas phase; namely, CS2, CS, S2, and S. (It can be calculated that the amounts of S6 and S, are negligible at these temperatures:) Morris and Bueh17 and Kitchener, Bockris, and Libermana had previously studied the corresponding

Jan 1, 1958

By Edgar M. Dunn

Part I. Determination oF Gases in Smelter Flues. General considerations. Regular methods for carbon monoxide, oxygen, nitrogen, moisture. Sulphur oxides-—Methods of Lunge and Hempel tried, and either modified or discarded, with reasons therefor. Gravimetric method developed at Anaconda. Description of apparatus used. Brief notes on Richter and Hawley methods for the direct cietermination of sulphur trioxide. Carbon dioxide, with complete notes on same. Arsenic trioxide. Table of percentages of flue gas constituents found at a Western smelter. Some final notations as to the value of flue gas analysis, in connection with an intelligent log of furnace operations. Part II. Notes on the Determination oF Dust Losses at the Washoe Reduction Works, Anaconda, Mont. Discussion of problem, with description of flue system. Various places and methods for determinations of velocity. Instruments used. Procedure in making determinations for velocity. Soundings of cross-section for depths of dust. Calculation of velocities and areas. Daily volume of gas, and plant operations during tests. Place for dust determinations. Apparatus and methods of 'sampling. Results obtained, with table of daily amount of dust losses. Analysis of dusts for values, from various sampling stations. Complete analysis of composite sample of stack emanation. Last analysis totaled to show form in which present. Discussion of recovery as a commercial proposition. References on Pitot tube and calculations.

Jan 1, 1914

(Under this heading will be published notes sent to the Secretary of, the Institute by members or other persons introduced by members.) Development and production. Member open for engagement. Past year in war mineral field work, operation and production. Ten years' thorough experience in both subordinate and executive positions, gold, silver and copper in the United States, Mexico, and South America. Age 37, married. Minimum salary $3600. Interview. South or East. A-577. Engineer and executive. Captain U. S. Army, age 36, expects discharge before July 1. Seven years' mining and metallurgical experience. Six years with large technical college as assistant professor of mining and directing extensive experimental work. Desires position as executive or research engineer with reliable company or as professor of mining with first-class college. A-909. Mining engineer. Twenty-five years' experience including mine and works operation, construction, plant installation, and mine examination. Speaks Spanish. A-1173. Metallurgical engineer. Twelve years' laboratory and operating experience, covering copper blast furnace, roasting, reverberatory smelting and latest Cottrell treater practice on copper dust and zinc dust. Technical graduate. 36 years of age, married. Highest recommendations. Open for immediate engagement. A-2354. Mining engineer. Junior Associate. At liberty about July 1. Captain Heavy Artillery. Single, age 24. Go anywhere. Best refer-ences. A-2843. Engineer. Age 26, single, graduate Missouri School of Mines, B. S. in Mis. Met. E. Desires position with oil or metal company in any capacity. Location immaterial. At present engaged, desires change. A-2844.

Jan 7, 1919

By C. S. Roberts, S. L. Couling

PLASTIC strain in polycrystalline metal as a result of bulk movement of one grain with respect to another along grain boundaries is not new. Rosenhain and Humphrey observed such effects shortly after the turn of the century.' Since then, observations of grain boundary deformation have been made on several metals. In recent years, intensive studies of the deformation at grain boundaries have been performed on polycrystalline metal and bicrystals.14-20 Aluminum or its alloys have been used in these latter studies. The subjects of controversy at present appear to be not whether grain boundary deformation exists, but 1) how quantitatively important it can be in polycrystalline metal, and 2) what its detailed mechanism is. Some investigators have concluded that such de- formation is minor in importance while others have concluded that it is a major consideration. Some have concluded that it involves shear of one grain over another at the interface while others have concluded that it operates by crystallographic deformation within the grains near ,the boundary. A categorical statement for electrolytic magnesium cannot be made on either of -these points. When polycrystalline magnesium is deformed in creep under conditions of high strain rate and low temperature, grain boundary deformation is relatively slight." Under these conditions, much deformation occurs within the grains and boundary contours change to a higher-energy jagged form. The result is shown in Fig. 1, where boundary jaggedness is pronounced upon polishing and etching after a plastic strain of approximately 6 .pct at 300°F and 3000 psi. No migration of the boundaries has been detected in this process. When the same metal is deformed the same amount at 600°F and 300 psi, resulting in a much lower strain rate, the boundaries migrate toward a lower energy configuration, where

Jan 1, 1958

By Maurice Grieves

The great majority of shafts constructed today are still excavated by drilling and blasting, a method which changed very little in over 100 years until the introduction of the mechanical lashing unit and cactus grab by the South Africans, which enabled muck to be removed as fast as massive hoisting systems could handle it and resulted in very rapid rates of sinking. Record breaking month's performances were achieved at -Hartebeestfontein No. 4 shaft, October 1960-337.1 m; Western Reefs No. 4 shaft, October 1961-340.7 m; and Buffelsfontein eastern twin shaft, March 1962-381.2m. The method was very labor-intensive, requiring a crew of over 60 workers at the shaft bottom during the drill cycle. Safety precautions were strict, but in the drive to achieve rapid advance, cases of personal injury were still somewhat high because of the large number of people engaged in this potentially hostile environment. The South African method, as it came to be referred to throughout the rest of the world, was adopted in the United Kingdom in the late 1950s in a modified form with greatly reduced manpower and nonsimultaneous sinking and lining, which was insisted on by the British Mines Inspectorate. In that instance, it was successfully used to sink the 7.3-m-diam concrete-lined shafts at Kellingley to 770 m depth, with rates of advance of over 90 m/month achieved, a British record at that time. During the sinking of the 1.15-km-deep twin shafts at Boulby potash mine in the UK in 1970, the method was again used, but for the first time ever in Britain exemptions from the mining code permitted the use of crash beams, crash doors, jack catches, and semi-simultaneous sinking and lining techniques. New British shaft sinking records of over 120 m/month were achieved in both shafts. Similar equipment and techniques were used in the early 1970s to sink several deep shafts in Canada, notably Creighton #7 and the Con zinc mine at Yellowknife in the NW Territories. Today, this equipment is standard for deep shafts in the US and the rest of the world. However, with the tremendous escalation in mining labor costs, the impact of health and safety legislation, and environmental regulations, coupled with a very real shortage of miners willing to work in this exposed situation it was apparent that an alternative to the labor-intensive conventional method of shaft construction had to be found. Recognizing the trend is inevitable, one or two major German shaft sinking contracting firms began to take a fresh look at full face boring techniques applied to tunnels and raise bored shafts. The results were most encouraging. Tunnel drivage techniques using moles had developed considerably from Colonel Beaumont's original channel tunnel machine circa 1880 to the superbly engineered Priestley machine selected to cut the British side in 1975 and the double shielded Robbins Grandori borer on the French side of the English Channel. Full face tunnel machines were being successfully used to drive uphill in inclined shafts in Austria and Switzerland. At Mapprag in Switzerland, the Demag mole drove the first (intentional) vertical transition and curve, and then went on to successfully complete the 730-m-long penstock shaft at an inclination of 35°. In Austria, the Wirth mole drove the Kaprun Glacier ski-lift railcar tunnel at record breaking rates of 457 m/MONTH (best 30 m/d) through green schist at an inclination of 29° for a distance of 3.35 km while the Hydro tunnel at Sarrelli in Switzerland was being driven by the Robbin's mole at an inclination of 35°. Simultaneously, extremely promising results were obtained using large assemblies of cutter discs on raise borer heads, such as the 4.87-m-diam X 460-m-deep shaft raised by Teton for Jim Walter Resources Inc. Bearing in mind that most mine shafts in the future (unless in exceptionally competent rock) will require some form of lining, and the trend will be toward deeper shafts as the more easily accessible mineral deposits become exhausted, it was seen that normal raise boring had definite limitations in vertical accuracy, in the limitation imposed by the drill string on the available torque that could be applied to the cutter head, and in the risk of collapse of the unsupported shaft rock wall in friable or jointed and fissured ground, since it is not possible to apply any form of temporary support until the permanent lining is being installed. A further problem was the economics of installing a subsequent lining, necessitating setting up a headgear and hoisting arrangement approaching in size that required for conventional drill and blast sinking and lining. Because of the economics, German contractors opted for a phased transition from drill and blast to the full face, rodless, out of the solid shaft mole, by starting off with a down-the-hole shaft boring machine -without a drillstring-but using a pilot hole to get rid of the muck.

Jan 1, 1982

By AIME AIME

AMONG the recent mining and metallurgical developments in England great interest has been shown in the development of an iron-ore field covering 26,0.00 acres in Northamptonshire, containing 500,¬000,000 long tons of ore; and the erection at Corby, by Stewarts & Lloyds, of a modern basic bessemer steel plant and tube works. The entire project was planned to cost about £3,300,000. Many improvements have been made in the varied equipment that is being installed, some of which has set mew records for massiveness. There is, for instance, a new roll crusher, which has been manufactured by Hadfields, Limited, of Sheffield, the largest ever built in England, and weighing 130 tons. This machine, shown in Fig. 1, as erected at the Hadfields shops, is primarily designed to take blocks of iron ore as they come from the steam shovel. The maximum size is 54 by 48 by 36 in., hut occasional pieces slightly larger than this may be accommodated. The capacity is upwards of 500 tons per hour, the product passing to a secon-

Jan 1, 1934