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By Arthur F. Taggart

A general awakening of interest among mill men concerning the mechanical efficiencies of their crushing machines is evident from a perusal of the recent files of mining publications. Considering the large part of the power bill which must be debited to the crushing department, such interest is natural. When, however, the articles on the subject are read, the only statement upon which the writers agree is that fine grinding consumes a large amount of power, and that the machine which, from a concentration standpoint, offends as a slime producer is, for that reason, a serious offender in wasting power. When the mill man attempts to find a method for measuring the power wasted, or to compare the efficiency of one machine with that of another for the same work, he is confronted with a choice of methods which lead to conflicting results. There are two reasons why the work of crushing is not more generally understood. In the first place, experimental data are difficult to obtain; and in the second place, before these data can be put in general form certain assumptions must be made. A difference in these assumptions by different investigators has led to conflicting conclusions. This conflict has resulted in the proposal of two laws. The first of these is the so-called Rittinger's law, which is variously stated as follows: "The work of crushing is proportional to the reduction in diameter."—R. H. Richards: Ore Dressing, p. 304 (1903). "The work required to crush rock is very nearly proportional to the reciprocals of the diameters crushed to."—A. Del Mar: Engineering and Mining Journal, vol. xciv, No. 24, p. 1129 (Dec. 14, 1912). "The work done in crushing is proportional to the surface exposed by the operation, or better expressed for this purpose, the work done on a given mass of rock is proportional to the reciprocal of the diameter of the final product, assuming that all the mass has been reduced to one exact size, which is only theoretically possible."— A. 0. Gates: Engineering and Mining Journal, vol. xcv, No. 21, p. 1039 (May 24, 1913). ' ' " Of this law as variously stated above H. Stadler says (Grading Analyses and Their Application, Author's Reply to Discussion, Transactions of the Institution of Mining and Metallurgy, vol. xx, p. 426 [1910-111):

Jan 1, 1915

By J. Fred Johnson

COROMANT is the trade name of the alloy-steel drill rod tipped with a chisel-type tungsten-carbide bit manufactured by Sandvik Steel Works Co., Ltd. Other names, such as Swedish or air-leg method of drilling, are used in various localities. Coromant drilling in Sweden was the natural sequence of the adaptation of tungsten-carbide inserts to the already established routine of drilling. By the middle thirties the percussion drill had reached practically its highest attainable efficiency as a drilling machine. Since then improvement has been in metallurgy of component parts to increase life or lessen weight, in the development of pneumatic and automatic feeds, in the use of jumbos to more quickly and easily handle machines, and in changes in drill rods and bits. By 1937, drilling in the United States and Canada was done by relatively heavy mounted drifters with positive hand or automatic feeds. In Sweden, on the other hand, emphasis had been placed on light equipment and drifting was done with pneumatic bars and reverse-feed stopers. In 1938, one of the most prominent American drill manufacturers developed an air-leg for successfully drilling the extremely variable but relatively soft iron ores of some of the northern Michigan mines. Also in 1938, a comparative Swedish test, also in soft iron ore, of a 50-lb jackhammer mounted on an air-leg, against a 100-lb reverse-feed drifter on a pneumatic bar, showed the net drilling time was increased by the air-leg set-up from 51 to 71 pct, in drilling 6-ft rounds in a 6 1/2x6 1/2 ft drift. Miners were becoming scarce in Sweden even at that time and, since the lighter equipment made the work easier and more attractive, the airleg was then made use of in some types of soft rock. In 1940, for instance, a large tunnel for a hydroelectric plant was driven with this equipment. By 1943, when tungsten-carbide inserts came into the picture in Sweden, a great many of the kinks in percussion drilling with this hard-metal had been worked out in Germany under the stress of war conditions. However, only 10 pct of the drilling machines manufactured in Sweden were jackhammers for use on air-legs and only the one manufacturer made air-legs in the United States. American practice had largely supplanted integral forging of drill bits by the detachable steel bit. Canada and South Africa were using the one-pass throwaway bit but Sweden was still using the same old integral forged bit. After a long study of the trend toward simplicity

Jan 1, 1952

By Russell Paul

THE Wisconsin zinc district, also known as the Upper Mississippi lead and zinc district, is an area of about 2500 sq. mi. in the southwestern portion of Wisconsin and adjacent parts of Illinois and Iowa. It includes Iowa, Grant and Lafayette counties in Wisconsin, Jo Davies County in Illinois, and an irregular strip of Clayton and Dubuque counties in Iowa, parallel to the Mississippi River. During periods of high metal prices mining has been quite active in this district, but recently the lower metal prices have caused many companies to suspend, so that at the present time there are only a small number of mines operating. The short life of these mines and the low mineral content of the zinc deposits limit the investment in development and equipment, and necessitates the operation of this equipment at maximum running time and maximum capacity. The tonnage of rock handled (locally termed dirt) is large in comparison with the tonnage of concentrate produced. Moreover, the zinc content of the concentrate is low, varying from 25 to 40 per cent zinc, and the value per ton is correspondingly low. The life of the mines varies greatly. An exception-ally good deposit may produce 2,000,000 tons of rock during a period of ten years, market value permitting, from which will be obtained 100,000 to 150,000 tons of concentrate. One property which might be con-sidered as fulfilling the requirements of a profitable operation was developed and equipped in 1925, oper-ated continuously for a period of two and a half years, produced 484,292 tons of rock, from which was obtained 37,659 tons of zinc concentrate, 34.4 per cent Zn, and 1155 tons of lead concentrate, 67 per cent Pb. During the war period prices of ore permitted the mining of lower grade ores than has been possible in the past few years. The maintaining of a higher grade mill-feed has resulted in reducing the size of stopes formerly carried in the old mines and confining the workings within narrower limits.

Jan 7, 1928

By C. E. Birchenall

DaVIES and Richardson1 have measured composition changes for Mn1-Owith variation in the equilibrium partial pressure of oxygen at 1500°, 1575°, and 1650°C, where 6 is the deviation from the simple stoichiometric ratio. No trend in this relationship with temperature was observed, so these remarks apply to the whole temperature range. The experimental values and their spread are shown by the bounded straight-line segments in the figure. Davies and Richardson assume that the stoichiometric oxide shows Frenkel disorder, given by the equation Mn2+Mn2+ + Mn" [1] where Mn2+ is a normal lattice ion which moves into an interstitial site (Mni2+) leaving a vacancy (Mn,"). The superscript dashes indicate that there is an excess charge on the anions surrounding the vacancy. Schottky disorder, in which a perfect crystal acquires equal numbers of cation and anion (Ov") vacancies according to leads to equations of exactly the same form in the analysis below. In view of the neutron diffraction results of Roth,2 which shows extensive Frenkel disorder in Fe1-o, Eq. [I] seems more appropriate. The deviations from stoichiometric composition, MnO, result from the addition of oxygen according to In effect Davies and Richardson ignore the variation of Mn3+in constructing equilibrium constants. This approximation might not appear to be very serious if the excess positive charges are really free posi- tive holes (P+) and if the intrinsic conductivity is high as a result of the reaction where e- is a conducting electron. However, the calculations of Buessem and Butler3 indicate that the partition functions of the free charges make a large contribution to the equilibrium constant, and this approximation would not be a desirable one. Furthermore, Morin4 shows that the positive holes are probably localized in MnO and therefore are described better by the mass action principle than by a degenerate gas model. Davies and Richardson's considerations require that activity corrections be applied beyond a 6 value of about 0.005. It is proposed to show here that the dissociation pressure curve can be calculated reasonably well over the whole composition range studied without activity corrections by choosing appropriate equilibrium constants for reactions 1 and 2. As stoichiometric composition The mass action constant, Ks, for reaction [I.] and the equilibrium constant, K,, for reaction [2] are given by where the concentrations which do not change significantly have been absorbed into the constants. The brackets denote concentrations. The deviation from stoichometric composition is given by gardless of [Mni2 ]. Substituting Eq. [7] in [6]

Jan 1, 1961

By Arthur F. Taggart, A. W. Thomas, T.C. Fitt

It was noticed early by operators that high recoveries and flocculation of the sulphide minerals were closely correlated in agitation-froth flotation. Later, this readily visible flocculation was found almost invariably to be due to the binding together of the oiled sulphides by minute air bubbles, and is now known to be characteristic of pulps in which at least one of the mineral species is coated with an insoluble collecting oil. In 1930 it was reported1 that in differential flotation a correlation exists between Brownian movement of particles in the pulp and their nonfloatability, and that Brownian movement and dispersion are likewise correlated, whence it would appear to follow that dispersion of a mineral particle in a flotation pulp denotes a particle condition unfavorable to flotation. In 1934 it was postulated2 that Brownian movement, dispersion and nonfloatability all flow from the condition of the surface of the dispersed particles. It was also postulated at that time that the surfaces of dispersed particles are ionized, the ionized compound being a product of reaction between a component of the particle and a component of the pulp, of a mass solubility of the general order of a fraction of a milligram to I 5 to 20 mg. per liter. It was then further asserted, and has since been confirmed by Bankoff,3 that sulphides so conditioned with soluble collectors as to be floatable flocculate without the intervention of air bubbles as binding media. The present paper comprises an inquiry into the nature of the bound and counter ions in zinc sulphide dispersed by sodium arsenate. A part of its findings was mentioned in the 1934 paper above cited.= The tests show that: I. When powdered granular zinc sulphide is immersed in aqueous solutions of sodium arsenate, arsenate ion is abstracted from solution and anchored to the solid surface, while sulphate and lower sulphoxy ions are concurrently displaced therefrom in substantially stoichiometric quantities. 2. The ion counterbalancing the anchored arsenate ion is zinc. 3. Dispersion and Brownian movement of zinc sulphide are concurrently maxima at an arsenate-ion concentration lying between 0.01 and 0.001-molar sodium arsenate. 4. Any condition or reaction that tends. to remove the zinc arsenate coating from the zinc sulphide particles decreases dispersion and Brownian movement concurrently. Experimental Three samples of zinc sulphide were used. Lot I was C.P. zinc sulphide, washed well be~ond absence of chloride, as shown by test with silver ion. Lot 2 was prepared by precipitation from hydrochloric acid solution of arsenic-free zinc, and was washed as lot I. Lot 3 was prepared by heating a portion of lot 2 in absence of air at 1200° to r300°C. for one hour."

Jan 1, 1943

By Arthur F. Taggart, T. C. Fitt, A. W. Thomas

It was noticed early by operators that high recoveries and flocculation of the sulphide minerals were closely correlated in agitation-froth flotation. Later, this readily visible flocculation was found almost invariably to be due to the binding together of the oiled sulphides by minute air bubbles, and is now known to be characteristic of pulps in which at least one of the mineral species is coated with an insoluble collecting oil. In 1930 it was reported1 that in differential flotation a correlation exists between Brownian movement of particles in the pulp and their nonfloatability, and that Brownian movement and dispersion are likewise correlated, whence it would appear to follow that dispersion of a mineral particle in a flotation pulp denotes a particle condition unfavorable to flotation. In 1934 it was postulated2 that Brownian movement, dispersion and nonfloatability all flow from the condition of the surface of the dispersed particles. It was also postulated at that time that the surfaces of dispersed particles are ionized, the ionized compound being a product of reaction between a component of the particle and a component of the pulp, of a mass solubility of the general order of a fraction of a milligram to I 5 to 20 mg. per liter. It was then further asserted, and has since been confirmed by Bankoff,3 that sulphides so conditioned with soluble collectors as to be floatable flocculate without the intervention of air bubbles as binding media. The present paper comprises an inquiry into the nature of the bound and counter ions in zinc sulphide dispersed by sodium arsenate. A part of its findings was mentioned in the 1934 paper above cited.= The tests show that: I. When powdered granular zinc sulphide is immersed in aqueous solutions of sodium arsenate, arsenate ion is abstracted from solution and anchored to the solid surface, while sulphate and lower sulphoxy ions are concurrently displaced therefrom in substantially stoichiometric quantities. 2. The ion counterbalancing the anchored arsenate ion is zinc. 3. Dispersion and Brownian movement of zinc sulphide are concurrently maxima at an arsenate-ion concentration lying between 0.01 and 0.001-molar sodium arsenate. 4. Any condition or reaction that tends. to remove the zinc arsenate coating from the zinc sulphide particles decreases dispersion and Brownian movement concurrently. Experimental Three samples of zinc sulphide were used. Lot I was C.P. zinc sulphide, washed well be~ond absence of chloride, as shown by test with silver ion. Lot 2 was prepared by precipitation from hydrochloric acid solution of arsenic-free zinc, and was washed as lot I. Lot 3 was prepared by heating a portion of lot 2 in absence of air at 1200° to r300°C. for one hour."

Jan 1, 1943

By L. K. Eigenbrod, F. Notaro

Enactment of Public Law 91-173 (Federal Coal Mine Health and Safety Act of 1969) has placed new responsibilities on the mining industry. The new law, aimed at eventually solving the problem of pneumoconiosis, sets new respirable dust standards at 2 mg per cu m. Techniques employed to date have been shown to lack total effectiveness in meeting the prescribed standards. Since it is possible that even the new standards will eventually have to be lowered to effectively attack the medical problem, the need for new and more reliable methods of assuring clean respirable air will intensity. This paper presents, in a preliminary manner, both the present technical capability and growth potential of cryogenic technology for supplying miners with clean breathing air. Work with two sizes of prototype supplied-air (cryogenic-liquid) respiratiors in Union Carbide's Fawn Coal mine, will be described. Other potentially fabricable systems will be discussed and a preliminary assessment made of the potential cost of introducing cryogenic air breathing systems in coal mine service.

Jan 1, 1972

By B. J. Scheiner, A. G. Smelley

The Bureau of Mines, US Department of the Interior, is conducting research on a dewatering technique for fine particles generated during the mineral beneficiation process that will recover a portion of the water now being lost using conventional waste disposal methods and significantly reduce the time required for land reclamation. The technique utilizes a flocculant, polyethylene oxide (PEO), that forms strong stable flocs that can be dewatered rapidly on static and/or rotary screens. Infield tests, phosphate clay waste has been dewatered from a nominal 2.5% solids to greater than 20% solids. In other field tests, coal-clay waste has been dewatered from a nominal 3% solids to greater than 55% solids. In addition, small-scale continuous tests have shown that bentonitic clays can be dewatered from 12% solids to 40% solids.

Jan 1, 1985

By S. Ramachandran, L. A. Vazquez, N. L. Grauerholz

A novel process is described for the selective flotation of scheelite from low-grade (- 0.5% W03) tungsten ores having appreciable quantities of calcareous and siliceous gangue minerals. Specifically developed for the Tempiute, Nevada facility of Union Carbide, the process yields tungsten concentrates exceeding 15 percent W03 with at least 85 percent recovery. This condition was not achieved through conventional processes. This process consists of conditioning the ore pulp with judicious amounts of lime, followed by soda ash and sodium silicate as modifiers. The scheelite is then floated using a mixture of oleic and naphthenic acids as collector. Contrary to the common observation as to the deleterious effects of calcium in fatty acid flotation systems, lime addition is found to be beneficial in achieving satisfactory results. The process has also shown excellent results on a Brazilian scheelite ore.

Jan 1, 1976

By C. A. Stetefeldt

The iron-ore deposits worked by this Company occur in lenses 200 to 1000 feet long and 5 to 80 feet wide, and stand at an angle of from 65' to 75, with a vertical height of 250 to 500 feet, other lenses occurring below. A number of the deposits were first worked as open pits, which in some cases were carried to the depth of 150 feet, when, owing to the weakness of the walls, underground mining was adopted. While the ore was being removed from the open pit, shafts mere in several instances sunk into the foot-wall, the intention being to mine the ore with breast-stopes of an approximate height of 20 feet, followed by underhand-stopes of the same height, leaving floors between of the necessary thickness to support the walls, or to effect the removal of the ore by means of what is known as the stall system. As the work progressed, however, it was found that the walls (which are of chlorite) were too weak to permit the working of breast-stopes 20 feet high, there being frequent heavy falls of ground from the hanging and, in some instances, from the foot. The plan of following breast-stopes with underhand-stopes was, therefore, abandoned. By working breast-stopes only, but little more than one-half of the ore could be removed, and that only at an excessive cost, the ore being so hard that power-drills with 3 1/8-inch pistons . and 6-inch stroke, working under 60 pounds of compressed air, are able to drill but 8 feet in ten hours as a yearly average, while from 6 inches to 2 feet is a common result of ten hours' drilling. It was plain that some other system of mining must be adopted, and it was proposed to sink by levels of 75 feet, carrying in the cross-cuts from the shafts and working out the ore each way from the shaft from foot to hanging, and from 15 to 20 feet in height. When this has been done, drift-sets consisting of caps and legs are set up the whole length of the opening and connected with the cross-cut; the necessary openings for ladder-ways and chutes or mills are timbered from

Jan 1, 1893

By Howard N. Eavenson

WHEN the A.I.M.E. was formed 75 years ago the bituminous coal industry was in its swaddling clothes, although it had been operating for more than a century and coal was being mined in every state now producing it, and its output had long passed that of anthracite. In 18/1, the value of bituminous coal was about seventy per cent of the value of all metals produced and more than one fifth of the value of all products of mines, both metallic and nonmetallic.[1a] While many of the operating mines then shipped by rail, most of the development was along waterways, although the canal era of transportation was nearly at its end. Coal mining is a heavy industry and one of the best measures of its progress is its output throughout the period. Fig. 1 shows this graphically from 1800 to 1945. From 1870 to 1910, the production-which is very nearly the consumption-almost doubled every decade, a most amazing growth. In 1918, in World War I, a peak was reached and a decline began, which ended in 1932. A gradual recovery then started, interrupted in 1938 but culminating in the record output of 1944, when, owing to World War II, a tonnage of 619,576,000 was produced. It is evident that the forces leading to the continuous increase ending in 1918 have spent themselves and that only unusual conditions will require so large a production again. The postwar conditions of World War II will probably

Jan 1, 1947

Long range expansion plans begun in 1966 by The International Nickel Co. of Canada, producer of over 50% of the free world supply of the white metal, are so mammoth as to give rise to the speculation that something might have to burst at the seams. From an annual level of capital expenditure of $35 to $70 million, the company jumped in 1967 to $145 million in new capital investment and will come close to $200 million in 1968. Inco expects to spend $700 million in the next five years, beginning in 1968, for new mines and surface facilities in Canada. The program involves the opening of nine new mines within the next 3 1/2 years, expansion of producing mines, and construction of new plants and modernization and expansion of established ones to process the increased ore production. Beyond this, the company is committed deeply in developing new sources of nickel abroad. Any one of these new projects, if proven economic, would necessitate expenditures of about $100 million or more. For Inco, the economic strain was relieved without a rupture this spring when Henry S. Wingate, company chairman, reported' at the stockholders annual meeting that $150 million had been raised by the sale of bonds. This marked the first time in 32 years that the company had gone into debt.

Jan 10, 1968

By P. A. Farrar, M. D. Silver, K. L. Komarek

Thermodynamic properties of Hf-0 alloys have been determined from 0 to 25 at. pct 0 between 1000" and 1200°K by equilibrating specimens with alkaline metal oxide-metal vapor combinations. Partial molar-free energies, enthalpies, and entropies of oxygen have been obtained and are conzpared with similar results for the Ti-0 and ZY-0 In continuation of a thermodynamic investigation of the Ti-O and Zr-O systems1 activities of oxygen and lattice parameters of Hf-0 alloys have been deter- system. The positional entropy in all three systems corresponds to an ideal random interstitial solution with one interstitial site per one metal atom. The lattice parameters of hafnium and Hf-O solid solutions have been determined in the range 0 to 20 at. pct O from measurements of Debye powder patterns. mined. All three metals dissolve large quantities of oxygen to form interstitial solid solutions. The phase diagram of the Hf-O system is shown in Fig. 1.' The maximum solubility of oxygen in the cph a phase is considerable (up to 25 at. pct O). The solubility in the high-temperature phase is much smaller. The only stable compound in the solid state is HfO2 which may exist with a certain oxygen deficiency. The low partial pressure of oxygen of Hf-0 alloys required the application of an indirect method. As the most suitable procedure a method, first applied by Kubaschewski to the V-O system,3 was combined with a principle developed by Herasymenko for the

Jan 1, 1963

By George Simkovich

It was hypothesized that solid-state point defects should alter the flotation properties of solids. Tests conducted on pure AgCl and AgCl doped with CdC12 show that atomic point defects exhibit an important role in the floatability of AgC1. Tests conducted on PbS doped with Ag2s or Bi2S3, also show that the defect structures resulting from these dope additions, i.e., a combination of electronic and atomic point defects, contribute significantly to the flotation of PbS. IT has been established that flotation occurs only when a finite contact angle exists between a solid and a gaseous bubble.' This angle, measured through the liquid phase, is expressed by the equation where the are inter facial free energies and the subscripts S, G, and L represent solid, gas, and liquid phases, respectively. As is seen in Eq. [I] three interface free energies, sG, sl, and GL, enter into the contact angle equation. Therefore, any variation in these energies which sufficiently varies the contact angle will, in turn, vary flotation processes. Changes made in any of the phases concerned, i.e., gas, liquid, or solid phase, are reflected through the changes occurring in two of the surface energy terms. Thus, a change in the liquid composition would be noted in sL and GL, and it is this phase, the liquid, which is most frequently altered in flotation studies., Changes in the solid phase must be reflected through the changes occurring in the sG and sL terms. In particular, it is hypothesized that changes in the surface concentrations of point defects in the solid-phase will alter the sG and sL terms which, in turn, will be reflected by flotation results. As an illustration of this hypothesis one may consider the defect structure and the flotation of AgC1. The bulk defect structure of AgCl is essentially one involving equal number of cation vacancies and interstitial cations.3 Upon adding CdC1, to AgC1, a greater number of silver ion vacancies are created in the bulk of the crystal.4 On the surface of the crystal the smaller binding forces and the free space accomodations may also allow for the creation of "surface interstitial anions", which will be designated as ad-anions. Thus, the point defect structure of the surface of AgCl doped with CdCl, will consist of cation vacancies and/or adanions. If the molecular forces responsible for the surface energies, ?SG and ?sL, are significantly altered by the presence of these surface point defects, then differences in flotation results will be noted as the concentration of these defects is varied. The defects present in AgCl are predominantly atomic in nature. In the case of PbS both electronic and atomic defects are present.5 This compound conducts electrically by either electrons or electron holes depending upon whether excess lead or excess sulfur is present. Upon disolving BiS3 in stoichio-metric PbS, one increases the concentration of cation vacancies and the number of electron carriers in the bulk of the crystal.5" At the surface, the possibility of ad-anions must also be considered. Conversely, upon dissolving AgS in stoichiometric PbS one increases the concentration of interstitial cations and the number of electronhole carriers in the bulk of the crystal.5,6' At the surface the interstitial cations will be designated as ad-cations. Thus, the point defect structure of the surface of a PbS crystal doped with Bi2S3 will consist of a number of cation vacancies and/or ad-anions and an excess of electrons. Conversely the point defects on the surface of a PbS crystal doped with Ag2S will consist of a number of ad-cations and an excess of electron holes. Again, as in the case of AgC1, should the molecular forces responsible for the magnitude of the interface free energies, ?sG and ?sL, be significantly altered by the presence of these surface defects then significant differences in flotation results will be noted as the concentration of these defects is varied. EXPERIMENTAL To test this hypothesis flotation tests were conducted on pure and doped AgCl and on PbS doped with either Bi2S3 or Ag2S. Preparation of the AgCl samples was performed as follows: AgCl and weighed amounts of CdC1, were melted in a porcelain crucible. The melt was then forced through a capillary tube and the particles emitted solidified in air as they fell about 1.5 meters. Spherical particles, -0.50 + 0.25 mm, were separated from the remaining solidified material

Jan 1, 1963

By C. D. Hunter, I. B. Browning, N. W. Shiarella

During the year 1936 improvement in the oil industry in Kentucky continued at about the same rate as shown by that of the year 1935 over the year 1934. The development of several new pools in western Kentucky and the increase in the application of repressuring methods to the old fields of eastern and to a lesser extent of western Kentucky increased the total production to 5,481,227 bbl., as compared to 5,175,054 produced in 1935. The principle sources of this increased production are the Livermore field and the new Bates Knob field in McLean County, in western Kentucky, and the result of repressuring operations in the " Corniferous" pools of Lee, Powell, Wolfe, Morgan and Estill Counties and the "Weir" sand (of Mississippian age) fields of Magoffin, Lawrence and Johnson Counties in northeastern Kentucky. The last named fields have a producing sand especially adaptable to these methods. Drilling No new fields were opened in eastern Kentucky during the year. All new drilling was codned to pressure wells and new oil wells to complete patterns around the intake wells. Owing to the relatively low "initial" or flush production of the wells in this section—even though the ultimate recovery per acre is as large—higher prices for crude will have to prevail before extensive search for new fields is begun; as in northwestern Kentucky, where active exploratory work has been carried on as in the several preceding years, resulting in numerous new and prolific, although comparatively small fields. In this section approximately 500 new oil wells drilled in the Owensboro field, embracing several pools in Ohio, Hancock, Daviess, McLean, Henderson, Webster and Nuhlenberg Counties in the northwestern part of the state. The total oil production for this field during 1936 exceeded by many thousand barrels the 2,821,722 bbl. produced in 1935. In these fields the producing sands range from the middle Missis-

Jan 1, 1937

By Donald C. Myntti

Modern open-pit mining can be described as a capital-, labor-and energy-intensive, large-scale, mechanized, and highly repetitive bulk material preparation and handling operation, with emphasis on the word "mechanized." In hard rock, this generally means shovels loading blasted materials into haulage units for transport to processing plants, stockpiles, or waste dumps. Mine management deals with several primary concerns on a daily basis; e.g.: Will any serious accidents and labor problems occur today, and will the tonnage targets be met considering the physical condition of the equipment? The latter subject will be discussed from a maintenance perspective. A successful, progressive heavy equipment maintenance program that protects company assets involves many elements. They include: •Proper equipment selection and procurement •Well-trained and motivated workforce •Good shop facilities •Preventive maintenance (PM) program •Warehouse support •Operations-maintenance department cooperation •Meaningful paperwork

Jan 3, 1978

By AIME AIME

No democracy such as ours, can ever be prepared for war, because we could never conceivably be the aggressor. The aggressor prepares in secret, designs his new tactics, and invents and makes new equipment and selects the time to strike. If a democracy prepare done year and the war came later, all that it had one would have to bed one over. All that England has today in the way of effective armament has been invented, designed, made, and the crews trained since the war began, because the totalitarian aggressor introduced new types of equipment and new techniques.

Jan 1, 1941

B. R. Coil (Electrical Installations at the Miami Mine are Cheaper with Flexible Cable, P. 356) was born in Higginsville, Mo., and attended McKinley High School and Missouri School of Mines. He received a B.S. in mining engineering. Mr. Coil has worked for the Braden Copper Co., Rancagua, Chile as junior engineer and foreman. He was employed by Miami Copper Co. as a jigger boss, shift boss, development engineer and mine foreman. He worked as mine superintendent and general superintendent of the Castle Dome Copper Company, Inc. Mr. Coil may be reached at Box 100, Miami, Ariz. He is an AIME Member. Mr. C. R. Ross was co-author with Mr. Coil in the preparation of this paper. His paper covers the present installation of electrical equipment in block caving stopes along with background data. In this paper he has given one solution to wiring problems in heavy stopes.

Jan 1, 1952

By R. E. Goodman, M. A. Mahtab

The, state of stress around a vertical wellbore in rock following nonlinear stress-strain laws is examined by means of finite element analysis. The wellbore, is considered an axisymmetrier body with axisymmetric loading. The initial vertcal and borizontal stresses are "locked" in the rock elements around the wellbore and a new state of stress is generated by the displacements which occur around the borehole. A point-uise variation of the elastic moduli is made on the basis of the new stress state and the triaxial data. The initial stresses tire now reintroduced along with tile changed moduli and original boundary constraints. This procedure is repeatrd until convergent stresses are reached. The effect of nonlinearity on streases is examined for a 6,000-ft wellbore in a scbistose gnezss and Berea sandstone using results of laborratory triaxial compression tests. The results sbou that the effect is restrited to one well radius from the bottom periphery of the bole. Beyond a distance of one-quarter radius, the elfect of nonlinearity on stresscs IS almost always less than percent for the cases conszdered, The consideration of a static pressure inside the well does not magnify the effect of monlinearity on borehole stresscs. INTRODUCTION The terms " wellbore" and "borehole" here designate cylindrical openings in the ground with vertical axis and a circular cross-section. A knowledge of the stress redistribution that occurs on excavating a wellbore is important in understanding (1) the behavior of the lined or unlined hole, (2) hydraulic fracture response, and (3) the effect of stress redistribution on drillability; also it is important in predicting initial stresses in the virgin ground, and in analyzing the response of measuring instruments placed in the borehole. Our knowledge of the state of stress around a wellbore has been restricted to homogeneous, isotropic, elastic material and derives chiefly from the analysis by Miles and Toppingl and the photoelastic work of Galle and Wilhoit2 and Word and Wilhoit.3 In this investigation the state of stress is examined for a nonlinear elastic material by means of finite element analysis. Many rocks possess stress-strain curves that depart notably from straight lines in their initial or final portions. While the literature contains abundant stress-strain data from triaxial tests (axisymmetric loading) on cylindrical rock specimens, there is little information on rock deformability under nonaxisymmetric loading conditions such as occur at each point around the bottom of a wellbore. Although there is some knowledge of the effect of intermediate principal stress on rock strength, there is virtually nothing known about its effect on rock deformability; therefore, we have assumed here that the effect of intermediate principal stress can be ignored. A schistose gneiss4 and Berea sandstone5 were selected as representative rocks for this analysis. The traditional graphs of deviator stress (ol -o3) vs axial strain were reworked to give the tangent modulus as a function of the deviator stress for varying values of the minor principal stress. The result is a nesting family of skewed, bell-shaped curves for tile gneiss (Fig. 1A) and the sandstone (Fig. 2A). A similar replotting of the lateral strain data defines the variation of Poisson's ratio (v) with the deviator stress and confining pressure. These curves, shown in Fig. 1B for the gneiss and in Fig. 2B for the sandstone, are not so well ordered as the tangent modulus curves. However, all of these display an increase of v with deviator stress application, but the rate of increase diminishes with confinement. The ET and v curves for the two rock types are tabulated in Tables 1A and 1A for use in a digital computer so that material properties corresponding to a given state of stress can be assigned by interpolation. STATEMENT OF THE PROBLEM Given a state of stress in the ground prior to drilling a hole (initial stresses), we assume that

Jan 1, 1969

By P. Chiotti, G. R. Kilp

IN the study of zinc-zirconium1 and zinc-uranium2 systems, vapor-pressure measurements were made in order to establish the equilibrium phase diagrams for a pressure of 1 atm. In each of these systems, only zinc has an appreciable vapor pressure over the temperature range investigated. The zinc pressure was measured over a sufficiently wide temperature and composition range to permit calculation of the standard free energy, enthalpy, and entropy of formation for the compounds ZrZn, ZrZn2, ZrZn3, ZrZn6, ZrZn14 , and U2Zn17. In these calculations the compounds were treated as line compounds. Although the exact composition range was not determined, metallographic and thermal data indicate that the solubility range for these compounds is small. It is to be noted that the compound initially reported to correspond to the formula UZn9, 2 has been shown by the crystal structure work of Makarov and vinogradov3 to correspond to the formula U2Zn17,. The crystal structure is similar to that for the compounds Th2M17, investigated by Florio,4 et al; here M represents iron, cobalt, or nickel. Therefore, thermodynamic calculations are based on the formpla U2Zn17 EXPERIMENTAL The dew-point method employed to measure the vapor pressure of zinc over uranium-zinc alloys has been described previously.2 The same procedure and apparatus were used in measuring the zinc pressure over zinc-zirconium alloys. In the case of alloys in the two-phase region consisting of a zirconium and the compound ZrZn, the Knudsen effusion method was employed to obtain a few values in the temperature range 600" to 560°C. In most cases, tantalum crucibles were used to contain the zirconium alloys. THERMODYNAMIC PROPERTIES OFU2Zn17 A least-squares treatment of the vapor-pressure data obtained for 35 and 65 wt pct U alloys in the temperature range 650° to 940°C gave lOg10PAtm = 7,713/T + 6.33 Here, as in following equations, T represents degrees kelvin and P represents the zinc vapor pressure in atmospheres. The probable errors for the two constants were calculated to be 60.68 and 0.0563, respectively. This relation represents the equilibrium dissociation pressure for the reaction U2Zn17 (s) - 2U(s) + 17Zn(v) The solubility of zinc in solid uranium is negligible and the only additional information required to calculate the free energy of formation of U2Zn17 is the free energy of vaporization of pure zinc. K. K. Kelley5 gives the relations, AF°= 30,902 + 6.03Tlog T + 0.275 X 10-3T2 - 45.03T

Jan 1, 1961