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Scraper and Slide Riddell Mucker Boskovich Device Hydro-mucker Inclined Shaft Mucking The Benching Method Performance Chart

Jan 3, 1950

By Wilson Blake

Rock deformation and failure taking place around underground openings is usually both accompanied and preceded by the phenomena of rock noise or microseismic activity. These small-scale releases of seismic and acoustic energy can be detected with special geophysical monitoring equipment. Use of this equipment allows one to look inside a rock mass to determine how an opening is behaving under the applied loading system. Microseismic equipment and monitoring techniques are briefly reviewed, and use of the microseismic method as an engineering tool in monitoring rock structure stability is illustrated by case histories. Examples cited range from evaluating roof stability using single-channel portable equipment, to rock burst monitoring using sophisticated computer controlled, multichannel monitoring systems.

Jan 1, 1983

Jan 1, 1967

In the maintenance of rubber-tired mining equipment, tires may well represent the single greatest problem. Using a 50-ton truck as an example, engine upkeep averages about 8% of the machine's total yearly operating cost, while tires average a whopping 20%. In fact, depending upon such factors as job layout, conditions, and whether it is maintenance or production people who run the job, tire costs can climb to as high as 50% of the truck's total operating expense. Similar costs apply to other earthmoving equipment such as tractor-scrapers and front end loaders. While operators must resign themselves to "normal" tire life and wear, there are many corrective steps that can be taken to fight the "abnormal."

Jan 8, 1978

By Wallace W. Wilson

It scarcely is possible to read a new issue of any of the principal mining trade journals without noting some mention of a major new overseas mining venture with which one or more domestic companies are involved. These projects follow a fairly consistent pattern; most are large open pit mines with relatively low grade orebodies but huge reserves; the total price tag is in nine significant figures and half or more of the total cost is for infrastructure. West' notes that nearly $7 billion is being invested annually for new mining projects and the expansion of existing mining ventures in the free world. He anticipates that by 1975 such investments will reach the $10-11 billion annual figure and that in the period 1972-76 total capital requirements can be expected to aggregate around $45 billion. West estimates that 75% of the total capital will come from internally generated funds. Conceivably, a substantially higher percentage could be attributable to external financing, especially if the trend of recent mineral development in Canada and Australia is any criterion, and including local sales of equity as a part of the package.

Jan 7, 1973

By James Norman

SEPARATION of minerals by froth flotation is rightly called an art. It can truthfully be said that no two ores separate in the same way. The difference in results obtained when natural and synthetic mixtures of minerals are separated is so great that such tests frequently have been worthless in attempting to select conditions in which a natural mixture will separate. With a few rare exceptions, the natural mixture is much more difficult to treat than a synthetic mixture, and a much poorer separation is obtained. Perhaps several experimenters have wondered why 10 or 20 per cent of a mineral being floated from an ore does not float and is different from the 90 or 80 per cent that is recovered. In experimental tests on pure sphalerite, observers1 have noted that varying amounts of sphalerite may be froth-floated with pine oil alone, the amount recovered in the froth depending apparently upon the source of the sulphide. The only explanation of results such as these, barring insufficiency of frother or time of flotation, is that the surface of the mineral floated is different from that of the mineral depressed. This difference often has been found to be caused by natural contamination of mineral surfaces, apparently brought about by weathering and exposure to natural solu-tions. There is virtually no rock that is absolutely unweathered. One of the writers had an exceedingly instructive experience in 1931 while working with United Verde copper-zinc iron sulphide ore in Arizona. Nonselective flotation of chalcopyrite and sphalerite away from some of the pyrite was all that could be accomplished. All known depressants produced only slight effect. Sodium cyanide showed some effect, but so much had to be used that only a small amount of chalcopyrite could be

Jan 1, 1939

By John J. Theiler

Early in 1963, the Inspiration Consolidated Copper Co., at Inspiration, Ariz., began a program to make automatic the lubrication of several critical points on their KW Dart 37SL haulage trucks. Prior to installation of the automatic lubrication system, all the haulage trucks were serviced by hand every three shifts. Now, with automatic lubrication, the service period has been extended to four shifts. What are the principal benefits to be expected from such a system? 1) Uninterrupted production; 2) extended machinery life; 3) good housekeeping; 4) lower maintenance costs. Of these points, the most important to truck maintenance are extended component life and lower maintenance costs.

Jan 5, 1965

By R. C. Allen, Ralph Arnold

The writers have no new system and no new principle of taxation to propose. The general subject of taxation is as old as governments are and as familiar to taxpaying Americans as the general thesis on the inalienable rights of man. We believe, therefore, following the committee of the National Tax Association, that improvement in the general conditions of taxation, including mine taxation, maybe brought about mainly through a better adjustment of known and tried principles and methods of taxing to modern complex forms of property and income, and that not much is to be expected from abandonment of experience for new ways and means, methods and principles, should anything new be discovered, which in our opinion is very doubtful. The committee referred to has constructed the general framework of its Model System of State and Local Taxation1 on familiar forms of taxing, by eliminating some that ' have proved bad, suggesting improvements in others, and adopting the best, leaving plenty of room for the accommodation of the general plan to the varying conditions of taxation in the several states. Unfortunately, the taxation of mines is dismissed by the committee with the statement that the subject has been reassigned for further investigation and report by a special sub-committee, frankly recognizing that the peculiar difficulties of this phase of the subject require special study and investigation. Much may be hoped for from the labor of this sub-committee if the problem is approached from the viewpoint of recommendations already published. In this paper, the writers state their opinion on some of the broader aspects of mine taxation with too little attention to the grounds on which they rest. Contrary to inclination space requirements compel them to resort to summary statements without adequate discussion for a satisfactory presentation of the whole subject. All they can do is to qualify the witnesses and record the testimony. The senior writer was introduced to the practical aspects of the subject of this paper in 1913, when, as State Geologist of Michigan, he was

Jan 1, 1920

By Milton C. Head, Aulton E. Roland, William E. Hawes

INTRODUCTION Uranium mining in the Grants Mineral Belt has undergone changes from methods pioneered during the 1950's and has now become fairly standardized throughout the district. The orebodies vary in size and shape and have been most successfully mined by using modified room and pillar methods with pillar recovery. This paper will expand on methods and equipment that are being used and modifications of these that will increase productivity and efficiency. GEOLOGICAL BACKGROUND The petrology of the Grants Mineral Belt consists of alternating layers of sandstone and shales (mudstone), with occasional thin layers of coal. The sandstones are aquifers which are generally artesian to some extent. The shales are bentonitic and decompose into extremely sloppy mud when exposed to water. Figure 1 shows a typical geologic section. Most of the uranium produced in the Grants Mineral Belt comes from the Westwater Canyon member of the Morrison Formation and occurs as scattered ore bodies throughout the formation. This formation consists of layers of bentonitic shale and sandstone of varying degrees' of cementing and grain size. It is also a very significant artesian aquifer. The unconfined compressive strength of the various formations is not high, as shown in Table I. It is important to note that these represent average values and a great range may exist within a single formation, especially In the Westwater which is the ore formation. [ ]

Jan 1, 1982

By Luther M. Krupp

A 3 ½ -mile asphalt mixed mat haulage road joins American Smelting & Refining Co.'s El Tiro copper pit northwest of Tucson and its Silver Bell mill. Two-axle trucks operate continuously over the road- way but the asphalt top shows none of the wash- board wear usually seen on dirt haulage roads during use by heavy vehicles. The following data cover construction of this road, and results of its use by Asarco and Isbell Construction Co., the road's builder.

Jan 11, 1958

Jan 1, 1965

By H. P. Greenwald, H. C. Howarth

The rapidly increasing use in coal mines of portable auxiliary fans, which are generally 'blowers" employed in connection with canvas tubing, raises questions concerning the hazards of such equipment, especially where the practices are opposed to established methods of ventilating face workings. Half a dozen or more coal-mine explosions and some fires have been attributed to the use of auxiliary fans; moreover, competent mining engineers have found many dangerous installations and methods of use-for example, intermittent running of the fans in gassy mines with consequent accumulations of firedamp at the faces. These facts have led the U. S. Bureau of Mines to issue this recommendation: "In the interest of safety, the Bureau of Mines, Department of Commerce, recommends that auxiliary fans or blowers should not be used in coal mines as a substitute for methods of regular and continuous coursing of the air to every face in the mine." The comparatively recent introduction of new types of mining machines, mechanical loaders, face conveyors, and slabbing machines has encouraged the trial of new systems of face mining, all of which have for their object the rapid advance of the faces. Although the latter has certain economic advantages, in gassy mines the rate at which gas is given off is generally found to increase in proportion to the speed of advance into new territory, which in turn increases the difficulties of efficient ventilation of the face workings. Some of the systems of advance mining being tried in connection with new mechanizing methods practically compel the use of blower fans and tubing, as single narrow places arc now driven 300 ft. or more without crosscuts. In some instances a series of parallel headings are driven without crosscuts pre-

Jan 1, 1928

By D. H. Forbes, H. M. Manasevit, F. L. Morritz

Single-crystal thin films of molybdenum have been grown. by the pyrolytic decomposition of molybdenum hexafluoride in a hydrogen ambient on various insulating substrates at temperatures front 650° to 900° C. Single-crystal discs of various orientations of magnesium aluminate spinel, a aluminum oxide, magnesium oxide, and the natural facets of beryllium oxide were all observed to exert epitaxial control on the depositing film. Determinations of the crystallographic relationships existing between film and substrates have been made, using X-ray diffraction three-circle goniometry and Laue back-reflection techniques. Using these data, crystallographic overlays have been constructed which suggest a possible interfacial geometry on the basis of a match between metal deposit atoms and metal ion sites in the substrate. A continuing program has been in effect in the Auto-netics Laboratories over the past several years aimed at the development of electronic materials in new and useful forms using chemical vapor deposition techniques. During the course of these investigations, the epitaxy of silicon1"5 and tungstenep7 on single-crystal metal oxide insulators was studied extensively. The deposition of molybdenum is a logical extension of the tungsten work since the crystal structure is identical and the lattice dimensions differ by less than 1 pct. The pyrolytic decomposition of molybdenum hexafluoride in hydrogen was used to grow molybdenum films on the oxide substrates AlzOs, MgA1~04, MgO, and Be0 at from 650" to 900°C, depending on the substrate material. Under the experimental conditions to be described, monocrystalline films of controlled orientation were obtained. The materials investigated and their crystal structure are listed in Table I. EXPERIMENTAL The molybdenum depositions were effected by the hydrogen reduction of molybdenum hexafluoride (MoFe) in a flowing system of hydrogen at atmospheric pressure. The schematic of the apparatus is shown in Fig. 1. The hydrogen, purified by passage through a heated palladium thimble, was mixed with the vapor of the liquid MoFe maintained in a steel bottle at room temperature (25°C). The mixture was passed over the substrate, which was heated by rf induction of a sup-

Jan 1, 1969

By P. R. Sperry, M. L. Holzworth, P. A. Beck

The basic work of Z. Jeffries 1,2,3 has long ago established the main features of grain growth in the presence of a dispersed second phase. Working with sintered specimens of initially fine grained tungsten, to which various amounts of thoria had been added, Jeffries found that grain growth was inhibited, that is, practically prevented, up to a certain annealing temperature. When this temperature, which increased with the thoria content, was exceeded, extremely large grains developed abruptly from the fine grained matrix. such a a temperature" was later found by Gross-mann~3,14 in certain types of steel, while ~~i~ showed15 that in other steels grain growth was gradual, without inhibition and abrupt coarsening. Later work demonstrated the connection between coarsening and aluminum additions. The viewpoint that the direct cause of inhibition and coarsening in aluminum killed steels is a fine dispersion of aluminum oxide21 appears to be held quite generally, although some doubts have been voiced even very recently, 20 In steels with Ti additions the titanium carbide phase is considered responsible for the inhibition effects found.20 The coarsening temperature increases with the titanium content. That coarsening may occur, as a result of, certain heat treatments, even in low carboil rimmed sheet steel, was shown by Samuels. He also detected coarsening in a steel ingot of similar composition, after giving it the same heat treatment as that used by him for the sheet material. In this instance the identity of the inhibiting phase has not been determined. However, Tangerding found23 that even the few small carbide particles, which occur in carbonyl iron, have a very marked inhibitive effect. As a result of an oxidizing anneal at 850°C, large grains begin to form at the surface of the carbonyl iron specimen, and gradually grow inward as the subsurface oxidation of the carbide particles progresses and eliminates the obstruction. The carbide particles Can be removed also by annealing in hydrogen, with similar results. But if the oxidizing anneal of 10 hr at 850°C in air is followed between in hydrogen for 75 hr at the Same temperature, grain growth is more hibition usually the whole specimen is transformed into a single crystal (approx. 1.5 cm X 5 cm). The reversed procedure, that is, hydrogen annealing followed by oxidizing annealing leads to smaller grains. Tangerding arrived at the logical conclusion that there must have been in his specimens some additional obstruction to grain growth hibition from a minor impurity, other than carbon. It seems likely that this obstruction was caused by an oxide formed during the oxidizing anneal and gradually reduced rtain the subsequent hydrogen-annealing. Other instances of grain growth inhibition of varying severity, associated with a dispersed second phase, have been described by several authors. Notable examples: lead with 0.06 pet Cu or Ni,24 cartridge brass with 0.12 pct Cr,25 or with up to 0.15

Jan 1, 1949

By J. D. Hanawalt, C. E. Nelson, J. A. Peloubet

The subject of the salt-water corrosion resistance of magnesium alloys is somewhat like that of the pitting of stainless steels, in that it involves a relatively small. percentage of the applications but receives a much greater proportion of the publicity. Actually magnesium alloys are in use in many exterior applications as well as interior, with no trouble from corrosion. Magnesium and its alloys have a striking stability against atmospheric attack, being far superior to iron. Specimens exposed unprotected to atmospheric weathering for Io Years show only a superficial surface-film formation. The basic nature of magnesium and of its important alloys is that they are also resistant to the attack of salt water even in an unprotected state, giving substantially no loss in weight after one year of alternate immersion in 3 per cent NaCl solution (Fig. 1). This basic behavior is often masked because of the extreme sensitivity of these alloys to certain impurities and combinations of impurities. It is known, and the subject of increasing emphasis, that higher purity leads generally to greater stability for many materials, non-metallic as well as metallic. However, a review of the literature on the corrosion factors in magnesium alloys shows that almost all researchers worked with base metal in which metallic impurities varied in uncontrolled amounts. The major factor, that of metallic impurities, Probably greatly overshadowed the effects of minor ones such as flux inclusions, nonmetallic impurities, porosity, metallographic state, which these researchers presumed to study. In the present investigation the first observation of interest is that whereas magnesium of commercial purity (99.9 per cent pure) has a corrosion rate in alternate immersion in 3 per cent NaCl solution at room temperature of anywhere from 5 to Ioo mg. per sq. cm. per day, the corrosion rate of high.purity magnesium is 0.15 ± 0.05 mg, per sq. cm. per day. The principle followed in the experiments was to add to such base magnesium other elements, singly and in inin in controlled and known amounts and to observe the corrosion behavior of the resulting alloy. These experiments show the existence of what may be called tolerance limits" of magnesium and some of its alloys for certain impurities. The extremely small percentages of impurities involved and the sharpness of the corrosion discontinuities appear to be quite unpredictable, In order to carry on this work, it was necessary to develop an analysis technique suitable to the problem. In some cases it was necessary quantitatively to analyze impurities to less than 0,001 per cent. The experimental data to be presented are based on observation of about 5000 alloy specimens and on more than 50,000 quantitative analyses. while the primary purpose of this paper is to present the experimentally obtained data on corrosion rates as a function of composition, and particularly to demon-

Jan 1, 1942

By J. D. Hanawalt, C. E. Nelson, J. A. Peloubet

The subject of the salt-water corrosion resistance of magnesium alloys is somewhat like that of the pitting of stainless steels, in that it involves a relatively small. percentage of the applications but receives a much greater proportion of the publicity. Actually magnesium alloys are in use in many exterior applications as well as interior, with no trouble from corrosion. Magnesium and its alloys have a striking stability against atmospheric attack, being far superior to iron. Specimens exposed unprotected to atmospheric weathering for Io Years show only a superficial surface-film formation. The basic nature of magnesium and of its important alloys is that they are also resistant to the attack of salt water even in an unprotected state, giving substantially no loss in weight after one year of alternate immersion in 3 per cent NaCl solution (Fig. 1). This basic behavior is often masked because of the extreme sensitivity of these alloys to certain impurities and combinations of impurities. It is known, and the subject of increasing emphasis, that higher purity leads generally to greater stability for many materials, non-metallic as well as metallic. However, a review of the literature on the corrosion factors in magnesium alloys shows that almost all researchers worked with base metal in which metallic impurities varied in uncontrolled amounts. The major factor, that of metallic impurities, Probably greatly overshadowed the effects of minor ones such as flux inclusions, nonmetallic impurities, porosity, metallographic state, which these researchers presumed to study. In the present investigation the first observation of interest is that whereas magnesium of commercial purity (99.9 per cent pure) has a corrosion rate in alternate immersion in 3 per cent NaCl solution at room temperature of anywhere from 5 to Ioo mg. per sq. cm. per day, the corrosion rate of high.purity magnesium is 0.15 ± 0.05 mg, per sq. cm. per day. The principle followed in the experiments was to add to such base magnesium other elements, singly and in inin in controlled and known amounts and to observe the corrosion behavior of the resulting alloy. These experiments show the existence of what may be called tolerance limits" of magnesium and some of its alloys for certain impurities. The extremely small percentages of impurities involved and the sharpness of the corrosion discontinuities appear to be quite unpredictable, In order to carry on this work, it was necessary to develop an analysis technique suitable to the problem. In some cases it was necessary quantitatively to analyze impurities to less than 0,001 per cent. The experimental data to be presented are based on observation of about 5000 alloy specimens and on more than 50,000 quantitative analyses. while the primary purpose of this paper is to present the experimentally obtained data on corrosion rates as a function of composition, and particularly to demon-

Jan 1, 1942