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By M. T. Melvin, N. P. Kripakov

The practical application of a post-processing modeling procedure to simulate progressive rock failure around the periphery of coal mine entries is presented. This numerical scheme utilizes a simple rock model that incorporates easily obtainable input parameters consistent with basic rock mechanics principles. These parameters include the cohesion, angle of internal friction, modulus of elasticity, and Poisson's ratio of the bedded deposits that comprise the imediate roof, coal seam, and immediate floor. The geometry of the entry, along with the in situ stresses existing at a mine site prior to mining, are also considered in the analysis. The potential of this procedure as a predictive tool in determining the extent of pillar rib fracturing and yielding of the immediate roof and floor is evaluated assuming a Mohr- Coulomb failure criterion. The procedure is designed to be user oriented and is adaptable to any finite element code with linear elastic capability, making it particularly attractive to users with limited budgets and computer size.

Jan 1, 1983

By Charles Fettke

The deposits described occur in a belt starting 1 ½ miles east of Juncos and extending 6 miles in a southeasterly direction. They are of the contact metamorphic type, being associated with a limestone and calcareous tuff that is interbedded with andesite tuffs and andesites which have been invaded by a quartz diorite intrusion. Of the fire occurrences examined, the largest can be traced for a horizontal distance of 2000 ft. No mining has, been done, but some of the outcrops lead to the belief that deposits of commercial size are present. IN CONNECTION with the gathering of data for a report on the geology of the Humacao district of southeastern Porto Rico during the summer of 1916, under the auspices of the Scientific Survey of Porto Rico and the Virgin Islands, conducted by the New York Academy of Sciences, the writer had an opportunity to make a brief examination of the magnetite deposits of the eastern portion of the island. Inasmuch as these deposits have attracted some attention as possible future sources of iron ore, and as there is only scanty reference made to them in literature,1 a short description based on this reconnaissance survey was deemed to be worthy of record. The magnetite deposits of eastern Porto Rico occur in association with a belt of limestone, trending approximately S 53° E, which begins 1 ½ miles east of Juncos and can be traced for about 6 miles toward the coast. Four outcrops of magnetite were observed, which are designated

Jan 2, 1924

By Ernest Kirkendall

THE amount of research done in the last few years on the subject of diffusion in solid metals is significant of the importance of this problem. To review the literature dealing with diffusion is unnecessary here. Desch1 in 1912 reviewed the work that had been done on diffusion in solids and gave a bibliography of the literature published before that time. Mehl's paper in 1936 2 is an excellent review of diffusion in metals and contains a large bibliography. Of importance also for its review and bibliography is an article by A. I. Krynitsky.3 While considerable material has appeared in the literature on diffusion in brass, the amount of information is not great compared to that pertain-ing to some of the other alloys. Most of the information published is of a qualitative nature; that which is quantitative varies considerably. Thus the quantitative determination of the rates of diffusion of copper and zinc in alpha brass by a new method appeared worth while. In the present investigation the rate of diffusion of zinc in approxi-mately the same composition alpha brass has been determined at three temperatures.

Jan 1, 1938

By C. M. Wayman, M. Miyagi

COMPARED to many of the binary alloys of iron, Fe-Ir alloys have received very little tud.'' Virtually nothing is known about the Fe-Ir equilibrium diagram' except for a few details concerning the liquidus-solidus positions for dilute iron-based alloys. It is reported1 that the y to a transformation temperature in Fe-Ir alloys (up to 40 wt pct Ir) is composition-dependent, varying from -900°C for pure iron to 0" to 100°C for Fe-40 pct Ir in an almost linear manner. The y to a transformation appears to be reversible,' the transformation hysteresis width increasing with increasing iridium content. In a qualitative way, the composition dependence of the y to a (and vice versa) transformations appears similar to those in the widely studied Fe-Ni system. In that the y phase (in Fe-40 pct Ir) can transform at -1000C, it

Jan 1, 1967

By George H. Hanna

THE importance of the Donets coal field (the Donbas) to the national economy of the Soviet Union is well known. Great as was the significance of this tremendous deposit of coal in prewar days it is destined to become an even greater factor in the economic life of the country now that the tremendous havoc wrought by the Germans is being remedied. Since the war began, new coal fields have been extended; for example output of the Moscow and Karaganda (Kazakhstan) fields has become considerably larger while new mines are producing coal in several parts of Uzbekistan and Kirghizia. The huge West Siberian coal field, the Kuznetsk Basin, is producing more coal than ever before to supply the industries of that region and of the Urals. But so great has been the development of industry to meet war needs, especially in those districts of the Soviet Union that lie to the East of the Urals, that the coal obtained, eked out by such locally-won fuels as peat and wood, is still barely sufficient to meet industrial requirements. The main burden of the coal supply for the restored industries of the West, therefore, will fall on the Donbas.

Jan 1, 1945

By Ernest R. Dickie

BRIEFLY, the ore body of the Bagdad Copper Corp., Bagdad, Ariz., is a monzonite porphyry carrying copper values fairly evenly distributed from the surface down through the primary zone. Tabular in shape, the ore body extends over several hundred acres. The oxidized zone averages about 60 ft thick and assays about 0.50 per cent copper. Under this is the chalcocite zone, or the zone of secondary enrichment, which averages about 100 ft in thickness and assays about 1.4 per cent copper. Under this zone lies the primary zone which extends in places to a known depth of about 150 ft and averages in grade about 0.60 per cent copper. Several years ago the block-caving method of extracting the ore from the chalcocite zone was installed. Then it was necessary to draw only about 250 to 300 tons per day, the capacity of the old milling plant. Early in 1943 the new 2500-ton concentrator was put into production. Drawing ore from the developed stopes in sufficient tonnage to furnish the mill at capacity proved unsuccessful in more ways than one. First, drawing the ore at an accelerated rate caused a large amount of dilution, there-by lowering the grade, and also caused funneling through to the surface. The surface material was detrimental to milling metallurgy and development of these stopes was costly per ton of ore extracted. The grade of ore decreased. making it impossible to maintain a mill head of over 0.9 per cent copper. The

Jan 1, 1947

By T. A. Rickard

T HE life and career of Daniel Cowan Jackling constitute a distinctive part of a passing era, marked by the intensive exploration and exploitation of the mineral resources of the western regions of the United States. In the development of his abilities and in the use of his opportunities, he typifies the initiative, the energy, and the skill of a modern captain .of industry. Daniel C. Jackling was born at Hudson, Mo., on Aug. 1.4, 1869. He was the only child of Daniel Jackling, born in England of English parents, and Lydia Jane (Dunn) Jackling, born in the United States, but of Scottish ancestry. His father died a few months after he was born, and he lost his mother less than two years later. The orphan boy was adopted by his aunt. He went to school as soon as he was old enough to walk the two miles, and back, alone. As opportunity offered, he went

Jan 1, 1937

By R. W. Raymond

THE Brüclrner roasting-cylinder is well known as an apparatus which has done good work in the desulphnrization, particularly of refractory silver ores, in the western districts of this country. A paper by Mr. J. M. Locke, of Cincinnati, describing the cylinders, as constructed by Messrs. Lane & Bodley, in that city, may be found at p. 295, vol. ii., of the Transactions of the Institute; and a paper by Mr. N. H. Cone, vol. iv., p. 226, gives an account of their operation in Colorado. The purpose of the present paper is to present an .improved construction, designed by Mr. Brückner. This is clearly shown in the accompanying plate, which scarcely needs explanation. It will be seen at once that this construction involves two cylinders, instead of one. Mr. Brückner thinks that three cylinders might be better yet, as securing an exact mechanical reproduction of the work of the well-known three-hearth Fortschaufelungsofen, the most perfect of the reverberatories in which delicate roasting is performed with hand-labor. THE APPARATUS. Erection of the Cylinders.—Although the cylinders may he put lip at any locality, or added to existing works, it is preferable, if possible, to choose the site on a hill sloping naturally, say about 30' or 33. Two excavations are made, one 8 to 12 feet higher up than the other; and each is protected by a wall with a batter of about 1 inch to the foot, to prevent slides of stone and earth. Each cylinder being 20 feet long and 7 feet in diameter, the total excavation should be 60 to 70 feet along the hill, and 15 to 25 feet wide. On each level a building is erected 35 feet long by 20 feet wide and 12 feet high, with the roof containing a ventilator against the hill. When both buildings are on the same level, there should preferably be a solid frame-work of very heavy timber, to carry the four rollers which bear the upper cylinder. The four rollers carrying the lower cylinder should preferably rest on two very heavy pieces of timber, strongly braced together and laid to their top in a foundation made of stone or brick and cement. Foundations are necessary only under each two opposite rollers, but they must be made carefully,

Jan 1, 1886

By R. G. Ward, John Henderson

It has been shown1 that the observed density1-' of liquid iron silicates in contact with solid iron depends upon whether nitrogen or argon is used to protect the experimental system from oxidation. These densities have been measured by the maximum bubble-pressure method, in five different labora-

Jan 1, 1965

By Robert C. Emmett, Donald A. Dahlstrom

FOR many years gravitational classification has been employed as a basic tool in beneficiation of minerals and coal. While improvements have been made to increase efficiency and fields of application, the basic flow pattern has remained relatively unchanged in most gravitational classifiers. Feed slurry is introduced into a settling pool wherein the coarser solids settle against either an upward or horizontal fluid current, or a combination of both, and are withdrawn in a concentrated underflow stream. The finer solids below the classification point possess too low a settling velocity and thus are primarily swept out through a weir overflow by the bulk of the fluid. Because of its simplicity, efficiency, and low power and maintenance costs, gravitational classification finds a wide acceptance for separations in the range of 20 to 325 mesh.

Jan 10, 1953

By Max Barber

PRESENT equipment and practices in open-pit mines of the Lake Superior iron ranges have been described recently in some detail by A. H. Hubbell.1 It is anticipated that any further improvements will be the result of gradual evolution of present methods and equipment, just as those now used have been gradually evolved from earlier methods. An exception to the process of gradual evolution during the last decade has been the adoption of electric power for operating shovels and trains in open-pit mines, but it is not expected that any such revolutionary changes will be made in the future. The use of Diesel, engine equipment will gain considerable headway, no doubt, and will find favor in certain lines of operation as improvements and adaptations are evolved to meet particular requirements. The question of installing belt conveyors for handling material from deep mines of restricted area, where haulage grades become a serious consideration, or even for transferring earth, rock, or ore material for distances of several miles, is now being studied and some very interesting data are being obtained.

Jan 1, 1932

Jan 1, 1971

By William E. Ford, Edward Salisbury Dana

The important BARITE GROUP is the only one among the anhydrous sulphates and chromates. Mascagnite. Ammonium sulphate, (NH4)2S0,. Orthorhomhic. Usrially in crusts and stalactitic forms. p = 1.523. Occurs about volcanoes, as at Etna, Vesuvlus, etc. Taylorite. 5K2SOa.(N&)ySOd. 111 small compact lumps or concretions. From the guano of the Chincha Islands. Thenardite. Anhydrous sodium sulphate, Na2S04. In orthorhombic crystals, pyrarnidal, short prismatic or tabnhr; also as twins (Fig. 384, p. 160). White, to brpwnish. 0 tically +. p = 1.477. Soluble in water. Often observed in connection with salt lates, as on the shores of Lake Balkhash, Central Asia; similarly elsewhere; also in South America in Tarapaca, Chilc. In the United States, forms extensive deposits on the Rio Verde, Aria. In Cal., at Borax Lake, San Bernardino Co. Aphthitaiite. Arranite. Glmerite. (Ii,Na)&O1. Rhombohedral; also massive, in crusts. Color white. From Vesuvius, upon lava; at DouglashaU near Weateregeln, Ger- many, in hloditc; Stassfurt, Germany; Rocalmuto, Sicily.

Jan 1, 1922

By A. M. Gaudin, C. S. Chang

Adsorption was measured for barium ion and laurate radical, using radioactively marked agents, over wide range of concentrations. Laurate adsorbed in absence of barium fails to float. With barium, flotation-effective laurate coating needs not exceed 5 pct of monolayer. Barium adsorption then is several fold larger. No barium laurate coating is obtained. IN general, fatty acids or their alkali salts do not cause clean quartz to float. However, the presence of multivalent ions, such as the alkaline-earth metal ions and heavy-metal ions, can activate quartz and thus make it respond to soap flotation. The mechanism of activation and soap flotation of quartz has been studied.'-' The problem was attacked by making flotation tests rather than by careful adsorption measurements on suspensions of ground quartz in solutions containing the activator and the collector. Attempts have been made to determine the adsorption of barium ion and calcium ion on quartz. The results have only qualitative value as the analytical methods were not adequately precise. Artificial radioactivity and progress in radioactivity detection have introduced a new analytical tool, which can have a sensitivity several orders of magnitude greater than that of other methods."-" In the experimental work described in this paper the radioactive tracers, barium 140 and carbon 14, were employed. Lauric acid was synthesized, having a radioactive carbon atom and was used with Ba" to study the adsorption of barium and laurate ions from aqueous solution on ground quartz. Flotation tests, using the vacuum flotation technique,' were run in conjunction with the adsorption experiments. The object of this investigation was to understand better the reaction mechanism of barium activation and soap flotation of quartz. Methods and Materials Quartz Sample Preparation: Lumps of hand-picked quartz, washed free of stains, were reduced in size to —20 mesh in laboratory crushers. The product was boiled in concentrated hydrochloric acid to remove the abraded iron. The cleaned product then was ground dry in a laboratory porcelain mill, using siliceous pebbles, to pass through a 200 mesh screen. The ground product was deslimed by sedimentation at 37 microns. This —200 mesh +400 mesh material was subjected again to boiling with concentrated hydrochloric acid, followed by washing with distilled water and further desliming. The cycle was repeated until no trace of iron could be detected in the wash liquor. During the final washing, the pH of the wash water was checked to insure the complete removal of the acid from the mineral. The quartz then was rinsed with conductivity water. The resulting product was dried in a drying oven and stored in mason jars. The impurities (spectrographic) were as follows: Al, 0.01 to 0.001 pct; Li, Mg, Mn, Na, each less than 0.001 pct; Fe and Cu not detected. The specific surface of the quartz sample was determined by the krypton gas adsorption method.' The average of two measurements was 881 sq cm per g. The calculated specific surface for 37/74-micron quartz particles, using a surface factor of 1.96; is 900 sq cm per g. This is in good agreement with the measured value of 881 sq cm per g. Beta-Counting Method: The radioactive isotope of barium used in the experimental work was barium 140. It has a sufficiently long half-life, 12.8 days, emits high-energy beta particles (up to 1.0

Jan 1, 1953

By A. M. Gaudin, C. S. Chang

Adsorption was measured for barium ion and laurate radical, using radioactively marked agents, over wide range of concentrations. Laurate adsorbed in absence of barium fails to float. With barium, flotation-effective laurate coating needs not exceed 5 pct of monolayer. Barium adsorption then is several fold larger. No barium laurate coating is obtained. IN general, fatty acids or their alkali salts do not cause clean quartz to float. However, the presence of multivalent ions, such as the alkaline-earth metal ions and heavy-metal ions, can activate quartz and thus make it respond to soap flotation. The mechanism of activation and soap flotation of quartz has been studied.'-' The problem was attacked by making flotation tests rather than by careful adsorption measurements on suspensions of ground quartz in solutions containing the activator and the collector. Attempts have been made to determine the adsorption of barium ion and calcium ion on quartz. The results have only qualitative value as the analytical methods were not adequately precise. Artificial radioactivity and progress in radioactivity detection have introduced a new analytical tool, which can have a sensitivity several orders of magnitude greater than that of other methods."-" In the experimental work described in this paper the radioactive tracers, barium 140 and carbon 14, were employed. Lauric acid was synthesized, having a radioactive carbon atom and was used with Ba" to study the adsorption of barium and laurate ions from aqueous solution on ground quartz. Flotation tests, using the vacuum flotation technique,' were run in conjunction with the adsorption experiments. The object of this investigation was to understand better the reaction mechanism of barium activation and soap flotation of quartz. Methods and Materials Quartz Sample Preparation: Lumps of hand-picked quartz, washed free of stains, were reduced in size to —20 mesh in laboratory crushers. The product was boiled in concentrated hydrochloric acid to remove the abraded iron. The cleaned product then was ground dry in a laboratory porcelain mill, using siliceous pebbles, to pass through a 200 mesh screen. The ground product was deslimed by sedimentation at 37 microns. This —200 mesh +400 mesh material was subjected again to boiling with concentrated hydrochloric acid, followed by washing with distilled water and further desliming. The cycle was repeated until no trace of iron could be detected in the wash liquor. During the final washing, the pH of the wash water was checked to insure the complete removal of the acid from the mineral. The quartz then was rinsed with conductivity water. The resulting product was dried in a drying oven and stored in mason jars. The impurities (spectrographic) were as follows: Al, 0.01 to 0.001 pct; Li, Mg, Mn, Na, each less than 0.001 pct; Fe and Cu not detected. The specific surface of the quartz sample was determined by the krypton gas adsorption method.' The average of two measurements was 881 sq cm per g. The calculated specific surface for 37/74-micron quartz particles, using a surface factor of 1.96; is 900 sq cm per g. This is in good agreement with the measured value of 881 sq cm per g. Beta-Counting Method: The radioactive isotope of barium used in the experimental work was barium 140. It has a sufficiently long half-life, 12.8 days, emits high-energy beta particles (up to 1.0

Jan 1, 1953

By J. Mote, P. Ward Flynn, J. E. Dorn

The effect of strain and strain rate on the critical resolved shear stress for prismatic slip in specially oriented single magnesium crystals was determined over a range of temperatures in an effort to identify the thermally activated strain-rate controlling dislocation process. Below about 450°K prismatic slip was preceded by twinning and fracturing. Above 450°K extensive prismatic slip was obtained followed by fracturing. Neither the Peierls&apos; mechanism nor the dislocation intersection mechanism can account for the observations. The data, however, are in good agreement with the dictates of Friedel&apos;s theory for cross slip to the prismatic plane. PREVIOUS investigations on single and polycrys-talline magnesium have resulted in the identification of the mechanisms of plastic deformation summarized in Table I. The-only well-confirmed mechanisms are {0001}, (1010}, (1011) slip plus (1012) twinning. The other twinning modes were only tentatively established and additional investigations are required to further confirm their operation. As noted in Table I, slip in this hexagonal close-packed metal invariably occurs in the direction of greatest atomic density, revealing that the Burger&apos;s vector for-active slip dislocations is always given by b = a/3<1210>. Slip is easily induced on the basal plane, and recent investigations have shown that the strain-rate controlling mechanism at low temperatures is the thermally activated intersection of the glide dislocations with dislocations threading the basal plane. In contrast, very little is known about prismatic slip. It has been reported to be active at points of stress concentration in polycrystals below

Jan 1, 1962

By H. Le Chatelier

Jan 1, 1894

By Albert Sauveur

To understand this paper properly, the reader must have a clear conception of what is meant by the " critical points " of iron and steel; * and in order to avoid the necessity of tedious references to previous publications on the part of those unfamiliar with the subject, it is here briefly recapitulated. Critictl Points.—If a piece of steel containing, say, 0.50 per cent. or more of carbon, be heated to a high temperature and then allowed to cool slowly, the cooling proceeds at first at a uniformly retarded rate until a temperature of about 700° C. is reached, when there is a sudden " retardation " in the fall of

Jan 1, 1897

By Cyril Wells, Robert F. Mehl

The two earlier papers in this series1,2 presented data on the rate of diffusion of carbon and of manganese in gamma iron. Apart from their scientific interest, these data are needed chiefly in order to treat data on carburization, on rate of formation of pearlite, and on rate of austenit-izing in a quantitative way.1&apos;2&apos;9&apos;10 In the present investigation rates of diffusion of nickel in ?-Fe over wide temperature and concentration ranges have been determined, and the effects of carbon, of im- purities, and of grain size on these rates have been studied. Claussen,3 using the data of Fry,4 has calculated the diffusion coefficient of nickel in y-Fe as 9.2 X 10-11 sq. cm. per sec. at 1200ºC., but had no data from which to calculate the variation of D with concentration, temperature, and percentage of carbon. Method and Materials Method.—Nickel was diffused along the axis of a cylindrical specimen across a concentration gradient, concentration-penetration curves were determined and D values calculated from Grube or Matano solutions.5 Details of the method are given

Jan 1, 1941

By R. L. Wiegel

The National Science Foundation, Erie Mining Co., and University of Minnesota Mineral Resources Research Center jointly sponsored a project to demonstrate the use of a small computer in the control of cyclone overflow size on one line in the Erie Mining Co. concentrator. The Erie circuit, similar to most taconite circuits, uses magnetic separators to reject tailings following each stage of grinding, resulting in additional variations in the demands made on the grinding circuit because of weight rejection fluctuation. Mathematical models were developed for rod milling, ball milling, hydrocycloning, fine screening, and five stages of magnetic separation. These models were used in concert to simulate the operation of Erie&apos;s circuit from rod milling through finisher magnetic separation.

Jan 1, 1980