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By B. K. Miller, R. S. Bradley

The principal producing areas of fire clay in Missouri are: (I) the east central district, which includes Audrain, Callaway, Montgomery, Warren, and Boone Counties (Fig. I); (2) the St. Louis district, which includes St. Louis and St. Louis County; (3) the north central Ozark district, which includes Franklin, Gasconade, Osage, Maries, Phelps, and Crawford Counties. Most of the semiplastic‡ fire clay is found in Audrain, Callaway, Montgomery and St. Louis Counties, and in St. Louis. Flint fire clay is found in Callaway, Audrain, and Montgomery Counties and in most of the north centra! Ozark district. High-alumina diaspore clay is found only in the north central Ozark district, except a few deposits found in Montgomery County. This paper is concerned with the semi-plastic fire clay that occurs in the east central Missouri district near Mexico, Audrain County, Missouri, which is mined by the open-pit method as practiced by the A. P. Green Fire Brick Co. About one-fourth of the semiplastic fire clay in that district is mined in shaft mines, and three-fourths in open pits.

Jan 1, 1942

By Gerhard Bockstiegel

Kuczynski's formula has been derived for the case of nonspherical particles. TWO formulae of Kuczynski's type have been derived, one describing the increase in tensile strength, the other describing the progress of shrinkage of a powder compact. It has been strength,shown that the exponents of all three formulae each contain two magnitudes of different physical characters, viz, the geometrical factor a and the kinetic factor ß. The interrelationships between the three exponents are stated. SOME years ago Kuczynski1 experimentally showed that the radius, x, of the area of contact between very small spherical metal particles and a metallic block is related to the time of sintering, t, by the following equation x = constant tk [11 where k has the value 1/5 or 1/7. Assuming that the metal particles were perfect spheres and the metallic block was perfectly flat, he derived the foregoing equation from theoretical considerations of the process of material transport in metals, and he showed that exponent k is different for different mechanisms of transport, e.g., k = 1/2 for viscous flow (according to Frenkel2), k = 1/3 for evaporation and condensation, k = 1/5 for volume diffusion, and k = 1/7 for surface diffusion. From this Kuczynski concluded that the mechanism of transport was either volume diffusion or surface diffusion, depending on whether the value of k, as found in his experiments, was 1/5 or 1/7. Subsequently. Cabrera8 corrected Kuczynski's calculations with regard to surface diffusion, showing that the theoretical value of exponent k is 1/5 for both volume and surface diffusion. He supposed that the different experimental values of k were due to slight differences in the shape of the metal particles. An exponential relationship similar to the aforementioned was found by Okamura, Masuda, and Kikuta,4 Masuda and Kikuta, and Takasaki8 when studying the rate of shrinkage on powder compacts during sintering. The authors measured the shrinkage by means of the fraction w = Vp — V./Vp — V,,,, where V,, is the volume of the green compact, V, is the volume of the sintered compact, and V,,, is the volume of the compact in its densest state. This fraction, w, they found, is related to the time of sintering, t, by the equation w == constant tm. [21 Further, Bockstiegel, Masing, and Zapf7 observed that the tensile strength, s, of sintering iron powder compacts can also be related to the time of sintering, t, by an equation of the foregoing type, i.e., s = constant tn. [3] For exponent n the values 0.28 (S=2/7) and 0.35 ( 2/5) were obtained, and the authors pointed out that there might exist a simple interrelation between exponent n as found in their experiments and exponent k in Kuczynski's equation. The authors supposed that 2k = n, since the strength of adhesion between a metal sphere and a block (as in Kuczyn-ski's experiments) must approximately be proportional to their contact area, p. x2. Theoretical Considerations This paper is an attempt to correlate the fundamental experiments of Kuczynski's type with the results obtained with powder compacts as represented by Egs. 2 and 3. In particular, the paper is to show how the rate of sintering is influenced by the geometry of the sintering particles and by the type of material transport. As the geometry of particles conglomerating in a powder compact is very complex, some simplifying assumption has to be made, of course, in order to adapt the problem to mathematical treatment. In the following paragraph a suitable simplification is introduced, and Kuczynski's formula is derived for the case of nonsphcrical particles. Relation Between Area of Contact and Sintering Time—As the face of contact between two particles in a sintering powder compact is not necessarily a circle (as in the case of spheres sintering to a block), Kuczynski's formula is modified as follows: Let the perimeter of the face of contact be described by means of polar coordinates R, 4, as shown in Fig. la, so the area of contact, f, is determined by f= 1/2 . S112p[R(Æ) ]2 dÆ [4] Then, let the two particles be intersected by a plane perpendicular to area f. The intersection is shown in Fig. lb. According to the nomenclature in this figure, the distance, h, between the surfaces of the two particles is a function of T and Æ: h = h(r,Æ). For the particular case of spherical particles, as in Kuczynski's theory, this function becomes: h = constant r2. It shall be assumed here that in the close neighborhood of their

Jan 1, 1957

By Murray F. Hawkins

Horner1 and van Everdingen8 ave shown that the pressure drop within the wellbore, as a result of having produced the well at a constant rate q for time t, where t is sufficiently large, is: van Everdingen observed that better agreement between theory and well performance can be obtained if, instead of assuming the permeability is kc everywhere about the well, it is assumed the permeability near the well-bore is substantially reduced as a result of drilling, completion and/or production practices. In order to account for the additional pressure drop he introduced the dimensionless quantity S, the skin effect factor, so that Eq. 1 becomes: Eq. 2 might have also been obtained as follows. Assume a zone of altered permeability k, exists about the well out to a radius r and beyond that the unaltered, external permeability k. The additional pressure drop required to overcome this skin of reduced permeability may be calculated with sufficient accuracy using the incompressible flow equation; for Browns-combe and Collins1 have shown almost no difference between compressible and incompressible steady-state flow, in the vicinity of the wellbore, and the small volume of fluid in the vicinity of the wellbore makes unsteady-state mechanics unnecessary. Then. The sign of this skin pressure drop will be positive or negative depending upon whether the altered permeability k, is smaller or larger, respectively, than the external permeability k... Adding the pressure drop of Eq. 3 to Eq. 1 to find the total pressure drop: Comparing Eq. 4 with Eq. 3 it is seen that the skin effect may be defined by: be determined from pressure build-up tests1,3,4,5,6,7,8 The average permeability kavg including the altered and external permeabilities, can be determined from PI tests, and may be defined approximately on the basis of steady-state flow, as was done by Thomas' in defining the damage factor, by: The productivity ratio is the ratio of the average to the external permeability, kavg/ke or This equation shows that the productivity ratio and the skin effect are not uniquely related, because of the uncertainty in the drainage radius, and also, in many instances, the wellbore radius. Fortunately, they enter in the logarithm. The curves of Fig. I are plots of Eq. 8 for values from 100 to 50,000. The points represent the skin effects and corresponding productivity ratios from a large number of well tests, taken from Fig. 15 of Ref. 5 or Fig. 13 of Ref. 9. While some of the data

Jan 1, 1957

By P. Pietrokowsky

RECENTLY a comprehensive investigation of the various sigma binary alloys was published by Duwez and Baen.1 It was shown that the following conditions are necessary for the formation of the sigma phase: (1) the difference in atomic diameters of the two alloying metals must not be more than about 8 pct; (2) of the two elements which form sigma, one must exhibit a body-centered cubic structure while the second metal must be face-centered cubic, at least in one of its allotropic forms. In addition, a tetragonal unit cell was proposed and powder patterns of six sigma phases were indexed for d spacings greater than 1.640 kx. Since the indexing, based on tetragonal symmetry, led to only fair agreement, the possibility of sigma being orthorhombic was investigated. Various methods for indexing orthorhombic powder patterns are de- scribed in the literature.' The method used in this investigation was a graphical examination of the differences in values of sin' 9 for the adjacent lines of the powder diffraction pattern. This method led to a complete indexing of the Cr-Co (60-40) pattern. Because of the strong similarity between the various sigma alloys, it was then possible to assign indexes to the patterns of Fe-Cr (50-50), Fe-Cr-Mo (30-30-40), Fe-V (50-50), Co-V (50-50), and Ni-V (50-50). The values of sin' 9 and indexes of the six sigma alloys, together with visually estimated intensities, are presented in table 1. In general, the similitude between the six patterns is quite good. For spacings greater than 1.75 kx a few differences are noticeable. In the Ni-V pattern, no (320) exists and the two strong lines (030) and (031) are separated by only two lines of lower intensity, unlike any of the other sigma patterns. However, very little is known about the Ni-V phase diagram and it is possible that the equal atomic percentage composition in this system lies in a two-phase region. At lower spacings there is a close analogy between the patterns. The planes

Jan 1, 1951

By J. J. Gilman

IT is well established that dislocations exist in crystals and account for crystal plasticity.' However, the origins of the dislocations are not clear. Among the means by which dislocations might originate are: a) through crystal growth accidents, b) by the collapse of condensed sheets of vacancies, or c) by stress-induced nucleation. Theoretical calculations' have indicated that the last means should require very high stresses in order to operate. The purpose of this paper is to show that the stresses around the tips of cracks are large enough to nucleate large numbers of dislocation loops. Specifically, it will be shown that (100) cleavage cracks in LiF crystals nucleate dislocations in regions of the crystals where dislocations did not exist previously. It is believed that the use of LiF for this investigation does not restrict the significance of the 1 results. In fact, it is believed that this complements and extends previous papers by the same author which dealt with metal crystals.10,14 The dislocations were detected by means of the etching techniques that were described in a previous paper by Gilman and Johnston.3 In that paper it

Jan 1, 1958

By S. C. Fall

The basic aims of the drilling and blasting program at the Mission mine are fourfold: 1. To provide 100,000+ tpd of broken alluvium and rock material for shovel excavation; 2. To obtain fragmentation that will permit the most efficient digging of the broken material and provide an acceptable crusher feed; 3. To conduct the drilling and blasting program in accordance with approved safety procedures; 4. To obtain these objectives at the lowest possible cost. The material that is mined from the pit is divided into four different rock types and the overlying alluvium. Each of these materials is broken by using procedures tailored to its individual characteristics.

Jan 9, 1965

By Cuppam Dasarathy

THE object of this note is to report briefly certain results of investigations on the Fe-In phase diagram. BISRA-high purity H-iron and 99.9 pct pure indium were used to prepare the alloys. The experimental techniques consisted of thermal analysis, optical metallography, and X-ray diffraction. A phase diagram based on the present results as well as those reported earlier by the author' is shown in Fig. 1. It is seen that the liquidus points fall on a smooth line which meets the monotectic isotherm at 1470°C. The liquidus extends up to 3.4 at. pct In. The phase boundary separating the two liquidus L1 and L2 is shown dotted. The experimental solidus meets the monotectic isotherm at -0.9 at. pct In. The 6/6 + L2 boundary drops steeply to the 6 + La/y + L2 boundary at -1350°C. In this region, it is impossible to detect satisfactory thermal arrests because of the steep phase boundary. The present diagram shows that indium lowers the temperature of the d/y transforma-tion and raises the temperature of the y/a transfor-mation. The y +d region is found to be very narrow. Indium gives rise to a restricted y field when alloyed with iron. The width of this field is between 0.4 and 0.5 at. pct In. Details of the alloys containing 40 and 50 at. pct In have already been reported by the author' and the transformation temperatures of these alloys are included in Fig. 1. It appeared from optical metallography and X-ray diffraction that the room temperature solubility of indium in a iron is less than 0.28 at. pct since alloys of 0.28 at. pct In and above, slow cooled to room temperature, contained dark etching second phase particles situated both in the matrix and grain boundaries of the a-grains, see Figs. 2 and 3. These particles were identified to be unalloyed indium by X-ray diffraction. The lattice parameter of the a phase reached a maximum of 2.8672A at the indium level of -0.28 at. pct. The present diagram, Fig. 1, is in substantial agreement with that of Stadelmaier and Fiedler' except for certain differences in detail. For example, they found the monotectic composition and temperature to be 7.0 at. pct In and 1443oC, respectively, while the present work indicates them to be 3.4 at. pct In and 1470°C. The 6 + L2/y + L2 transformation is indicated in the present work to occur at -1350°C, whereas Stadelmaier and Fiedler find this to occur at -1320°C. They also claim that the width of the y field is 0.2 at. pct In while the present work shows the width to be between 0.4 and 0.5 at. pct In. 1) Indium, when alloyed with iron, gives rise to a restricted y field, the width being >0.5 at. pct In.

Jan 1, 1970

By W. J. Millard

Owing to a moratorium in the drilling of crown-land leases in Trinidad during the year of 1931, only 40 wells were spudded in during the first eight months as compared with 110 during the same period in 1930. Nevertheless the production will show an increase of about 400,000 bbl. over that of 1930. An estimate is given in Table 1. Since the oil produced in 1930 was 9,418,907 bbl. and that in 1931 probably will be 9,853,976 bbl., the year 1931 probably will see an increase of about 4.6 per cent. The gross production of crude oil in the colony has increased steadily year by year, with the exception of 1919, when there was a slight decline. A tabulated statement was given last year.' The Petroleum Times of March 21, 1931 (p. 413) gives the total production of 1930 as 9,418,000 bbl. and the average monthly production as 784,833 bbl. The same two items for 1931 are estimated at 9,853,976 and 821,165 bbl., respectively.

Jan 1, 1932

By R. Ehrlich, F. E. Crane

A consolidated porous medium is mathematically modeled by networks of irregularly shaped, interconnected pore channels. Mechanisms are described that form residual saturations during immiscible displacement both by entire pore channels being bypassed and by fluids being isolated by the movement of an interface within individual pore channels. This latter mechanism is shown to depend strongly on pore channel irregularity. Together, these mechanisms provide an explanation for the drainage-imbibition-hysteresis effect. The calculation of steady-state relative permeabilities, based on a pore-size distribution obtained from a Berea sandstone, is described. These relative permeability curves agree qualitatively with curves that are generally accepted to be typical for highly consolidated materials. In situations where interfacial effects predominate over viscous and gravitational effects, the following conclusions are reached. 1. Relative permeability at a given saturation is everywhere independent of flow rate. 2. Relative permeability is independent of viscosity ratio everywhere except at very low values of wetting-phase relative permeability. 3. Irreducible wetting-phase saturation following steady-state drainage decreases with increasing ratio of nonwetting- to wetting-phase viscosity. 4. lrreducible wetting-phase saturation following unsteady-state drainage is lower than fir steady-state drainage. 5. Irreducible nonwetting-phase saturation 101lowing imbibition is independent of viscosity ratio, whether or not the imbibition is carried out under steady- or unsteady-state conditions. Experiments qualithtiveIy verify the conclusions regarding unsteady-state residual wetting-phase saturation. Implications of these conclusions are discussed. INTRODUCTION Natural and artificial porous materials are generally composed of matrix substance brought together in a more or less random manner. This leads to the creation of a network of interconnected pore spaces of highly irregular shape. Since the geometry of such a network is impossible to describe, we can never obtain a complete description of its flow behavior. We can, however, abstract those properties of the porous medium pertinent to the type of flow under consideration, and thus obtain an adequate description of that flow. Thus, the Kozeny-Carmen equation, by considering a porous medium as a bundle of noninterconnecting capillary tubes, provides an adequate description of single-phase flow. With the addition of a saturation-dependent tortuosity parameter in two-phase flow to account for flow path elongation, the Kozeny-Carmen equation has been used to predict relative permeabilities for the displacement of a wetting liquid by a gas. 1-5 It has long been recognized that relative permeability depends not only on saturation but also on saturation history as we11.6,7 Naar and Henderson8 described a mathematical model in which differences between drainage and imbibition behavior are explained in terms of a bypassing mechanism by which oil is trapped during imbibition. Fatt9 proposed a model for a porous medium that consisted of regular networks of cylindrical tubes of randomly distributed radii. From this he calculated the drainage relative permeability curves. Moore and slobod,10 Rose and Witherspoon,11 and Rose and Cleary12 each considered flow in a pore doublet (a parallel arrangement of a small and large diameter cylindrical capillary tube). They concluded that, because of the different rates of flow in each tube, trapping would occur in one of the tubes; the extent of which would depend upon viscosity ratio and capillary pressure. They limited

Jan 1, 1970

By Norman D. Fitz Gerald

The lack of a continuous operating balance in petroleum refining, which is analyzed in this paper, is by no means a feature solely of this division of the oil industry. Serious disequilibria of a capital as well as an operating nature exist both in the producing and marketing departments, while problems in the former and to some degree the latter are complicated by political involvements. Attention has previously been directed to the unstabilizing influence of present proration formulas in stimulating unnecessary drilling.' While equilibrium in petroleum refining operations has been fairly well maintained in the past decade, examination of departures may prove fruitful. Economic analysis is the application of time and motion study to the functioning of management, rather than labor. Properly applied it may reveal changes in policies that would increase the utility of the properties and facilities of the industry for stockholders, employees and the public, while contributing a stabilizing influence to the general economy. The study of economic equilibrium is essentially one of measurement and interpretation, requiring adequate data and the development of a technique of analysis that employs statistical and mathematical methods as a supplement to the broad descriptive phase of economics. Economic equilibrium in petroleum refining is a dual concept. It embraces both the over-all balance between total storage and total demand for major products and the internal balance between the demands and inventories of the various products. The latter is the more complex of the two for it is concerned with proportionating the supplies of the several products stemming from the joint source to the demands for the individual products which are subject to wide variations. All the products are essentially nondurable goods, and they are used both by producers and consumers but in varying proportions. Motor fuel is very largely a consumer's good, while residual fuel oil is almost entirely a producer's good, the other products falling between these extremes. The peculiar-

Jan 1, 1939

By Norman D. Fitz Gerald

The lack of a continuous operating balance in petroleum refining, which is analyzed in this paper, is by no means a feature solely of this division of the oil industry. Serious disequilibria of a capital as well as an operating nature exist both in the producing and marketing departments, while problems in the former and to some degree the latter are complicated by political involvements. Attention has previously been directed to the unstabilizing influence of present proration formulas in stimulating unnecessary drilling.' While equilibrium in petroleum refining operations has been fairly well maintained in the past decade, examination of departures may prove fruitful. Economic analysis is the application of time and motion study to the functioning of management, rather than labor. Properly applied it may reveal changes in policies that would increase the utility of the properties and facilities of the industry for stockholders, employees and the public, while contributing a stabilizing influence to the general economy. The study of economic equilibrium is essentially one of measurement and interpretation, requiring adequate data and the development of a technique of analysis that employs statistical and mathematical methods as a supplement to the broad descriptive phase of economics. Economic equilibrium in petroleum refining is a dual concept. It embraces both the over-all balance between total storage and total demand for major products and the internal balance between the demands and inventories of the various products. The latter is the more complex of the two for it is concerned with proportionating the supplies of the several products stemming from the joint source to the demands for the individual products which are subject to wide variations. All the products are essentially nondurable goods, and they are used both by producers and consumers but in varying proportions. Motor fuel is very largely a consumer's good, while residual fuel oil is almost entirely a producer's good, the other products falling between these extremes. The peculiar-

Jan 1, 1939

By Norman Carmichael

This paper describes the evolution of transportation at an important mining property, beginning at a time when the railhead was 400 mi. distant, and tracing the steps leading to the development of what is probably the heaviest ore train ever operated in underground mine service over narrow-gage tracks, a 300-ton ore train on a 20-in. track, at working costs closely approximating those obtained on systems involving much greater capital expenditure. Useful where geological and financial considerations render inadvisable the excavation and maintenance of large tunnels and heavier rolling stock. THE problem of transportation in the Clifton-Morenci district of Arizona has been one of peculiar difficulty and consequently has been an important factor in the cost of mining and treating the ores produced. From the crude beginning made over 50 years ago, many changes have been necessary to keep pace with the increased output of copper. A heavy-duty haulage system has developed on the original 20-in. track gage to meet the existent metal-mine conditions.

Jan 3, 1924

By C. M. Means

Considering the hazard involved in mining operations, statistics show that a very small percentage of accidents is chargeable to electricity. These accidents do represent quite a large percentage of those that are preventable and they are the direct result of the introduction, for purely economical reasons, of a dangerous element. The introduction of electricity in mines should decrease the hazard, and in no case should electricity be applied to the mechanical operation of equipment if by so doing the dangers incidental to mining are increased. The greater number of accidents are the result of persons coming in contact with exposed conductors at potentials varying from 258 to 508 volts direct current. The use of alternating current at higher potentials than these is quite common in large mines, but it is very rare that an accident happens from this source. This is explained by the fact that where these high voltages are warranted, proper precautions are taken, and the installations are directed by those who fully appreciate the dangers incidental to the work. Direct current is in much more general use than alternating current because of its adaptability to haulage locomotives and the low cost of installation in small operations. We are, however, coming to a more extended application of alternating current for the operation of mechanical devices used in connection with mining. Our underground direct-current wiring system is an evolution from the surface trolley and feeder systems. This is probably due to the fact that our earlier successful applications were electric locomotives, which required the use of a trolley wire. The trolley current has been almost banished from industrial establishments on the surface because of the hazard involved, yet we use it indiscriminately underground, where the dangers from accidental contact or fire are infinitely greater., This does not mean that the underground trolley systems should be eliminated, but it does imply the proper safeguarding of such equipment as is necessarily a part of the trolley systems. It is a fact that the men now employed in the installation and maintenance of mining equipment may be in many cases incompetent or not thoroughly familiar with the work, but they are the men who must do the work and, in order to do it properly, it is necessary that they be educated

Jan 1, 1915

By Joseph W. Richards

This method of briquetting flue-dust, or flue-dust mixed with fine ores, or, in a few exceptional cases, coke-dust, has come into large commercial use in Europe, and a small plant is already in operation in the United States. It promisea to become of such great importance to the iron industry of the United States that the following description will certainly interest the majority of our pig-iron producers. Discovered in 1908, the process Tests upon the observation of Dr. Schumacher that blast-furnace flue-dust, while possessing of itself no binding or cementing properties, acquires strong cementing properties if mixed with a very small amount of certain salt solutions, the amount of which is so small that the resulting cementation appears to be rather by catalytic action of the salts added than by the mass-action of such chemicals. To be more specific, fresh blast-furnace flue-dust mixed with from 5 to 10 per cent. of its weight of magnesium chloride or calcium chloride solution—that is to say, with from 0.25 to 2 per cent. of its weight of magnesium chloride or calcium chloride—acquires the property of setting within a short time, from 15 to 60 min., and forming a hard cemented briquette. Alkaline solutions appear to have no action such as described, and they even interfere, if present, with the action of the magnesium and calcium solutions. When treated in this way the flue-dust briquette sets very hard, apparently from pure excess of cementing- and setting-power. It is, therefore, possible to mix with the flue-dust a considerable proportion of inert ore or like material, which has no setting-power by this process, and thus to make a compound briquette containing large quantities of ore mixed with flue-dust, but in which the flue-dust may be regarded as the cement or binding-material. A particularly strongly cementing flue-

Jan 1, 1913

By E. A. Anderson

THE copper-zinc phase equilibrium diagram has been the sub-ject of many investigations. Until recently, however, the boundary of the terminal solid solution of copper in zinc (eta) has not been thoroughly investigated. This paper reports determinations of the solid solubility of copper in zinc at temperatures from 100° to 400° C., the course of the liquidus and solidus for the eta solid solution and determinations of the peritectic temperature and peritectic point for the reaction between epsilon and the melt to form eta. The liquidus of the eta phase was determined by thermal analysis and the solidus by the microscopical examination of specimens quenched from temperatures above and below the solidus. The temperature of the peritectic horizontal was obtained by thermal analysis and the com-position at the peritectic point was determined by extrapolation of the solid solubility boundary of the eta phase to the peritectic horizontal. The solid solubility boundary of the eta solid solution was investigated very carefully. Particular care was used to achieve equilibrium in the alloys at each temperature selected. The X-ray, electrical con-ductivity and microscopical methods were used in determining the solid solubility limits. The X-ray method measures the changes in the solvent lattice with increasing solute content and in this manner locates the composition of the alloy at which no further change in the solvent lattice takes place, the limit of solid solubility. The method of electrical conductivity measures the conductivity of the alloys of a graded series of compositions, whereby the solubility limit is indicated by a discontinuity in the conductivity-

Jan 1, 1934

By L. Adler

A relatively simple and effective technique is proposed to deal with the failure of geologic masses containing weakness planes. This technique, termed irextended" rupture envelope, provides a means to clearly distinguish rock and soil from fractured rock and, on a theoretical level, considers a matrix-inclusion system. It may also constitute the link between Mohr's and Griffith's failure theories. Included in the article are five sample problems concerning site location, structural design, strengthening the plane of weakness, changing the magnitudes of major and minor principal stresses and changing the orientations of major and minor principal stresses. Engineers trying to solve design problems in rock and soil mechanics have often assumed an iso-tropic and homogeneous medium. For naturally occurring geologic masses this assumption has always been viewed with regret. The following analysis which deals with the effects of plane anisotropy on failure presents a solution to this. The planes of weakness are joints, faults, bedding planes, fracture and cleavage (natural and induced), foliation and schistosity. The physical properties of these weakness planes include an undulating surface, frictional resistance, discontinuous extent, filling material, tightness and presence of water to cause a hydrostatic pore pressure. All of these properties relating to failure can be summarized in Mohr's rupture envelope for the plane of weakness. This, along with the geometrical orientation, strike and dip, of the plane of weakness produces what is termed an irextended" rupture envelope. MOHR'S STRESS CIRCLE AND RUPTURE ENVELOPE The significant features of these concepts are listed below.' 1) A point on the u - r coordinate plane represents the normal and tangential stress components on a reference area in the material. This area can have any orientation. (Fig. la)

Jan 1, 1963

By Joel Watkins

THE terms kaolin, china clay, ball clay, and paper clay are more or less loosely and interchangeably applied to a large class of white-burning clays. These clays are made up chiefly of hydrous amorphous (colloidal) aluminum silicates with variable amounts of free silica and other impurities in small quantities. Occasionally also the term kaolinite is wrongly applied to a white-burning clay, for kaolinite, is a mineral of definite chemical composition and definite crystalline form which occurs but sparingly in nature. It is not the purpose of this paper, however, to define or classify clays, or to enter into a discussion of the chemistry of clays. It is rather a general description of the occurrence and methods of mining of a kindred group of clays, and a discussion of their future economic aspect. In the Southern Appalachian States, the mining of white-burning clays has in recent years become an important industry. Although these clays are of several distinct types, which occur in as many localities under different geologic conditions, they are for the most part. primarily of the same origin. They are essentially the same in elementary constituents, and are largely consumed in the same industrial arts. From the standpoint of a mining engineer, therefore, and for convenience in comparison and correlation, it should be interesting to discuss them under one heading.

Jan 2, 1915

By T. M. Yegulalp

This article summarizes some of the results of the continuing research activity at the Henry Krumb Schools of Mines, Columbia University, directed towards a better understanding of the stochastic behavior of slurry flows in underground coal-slurry pipeline systems. Fundamental ideas supported by field observations are presented and a Semi-Markov model of the slurry flows is developed. As a result of this formulation, behavior of combined slurry flows from N independent coal faces can be expressed in analytical form. The contents of a slurry surge tank receiving slurry flows with certain stochastic characteristics is investigated in a function of discharge pump characteristics and time.

Jan 1, 1983

By Blamey Stevens

It is now generally agreed that most metals have been brought to the surface of the earth by volcanic agencies. The question as to how these metals came from the volcanic matrix to the mineral deposit has been often discussed. It might be useful to give more serious consideration to the ultimate origin of the volcanic material. It is possible that some light might thus be shed on the persistent associations of some metals with certain particular kinds of rocks. For example, the very general association of gold with acid types of igneous rocks, of tin with granites or quartz-felsites, of certain types of deep-seated copper-deposits with magnesian eruptives, and so on. One interesting question is as to whether the metals brought near the surface by volcanic agencies appear here for the first time, or whether they came from the central core of the earth. The interior of the earth is, without doubt, much more highly metallic than the crust, and so the core is often thought to be the origin of many of the metals which are uncovered by man. The Differentiation Theory.—Although a great many theories bearing upon these matters have been discussed,' the only one now considered as worthy of much consideration among American geologists is the " Theory of Differentiation of Igneous Magmas."2 According to this theory, lakes of molten magma are supposed to exist very far down beneath the earth's surface. In these lakes a process of differentiation is supposed to be going on whereby the liquid magma is split up into two or more liquid phases. Each of these phases is supposed to take with it the metallic constituents for which it has the greatest affinity.

Jan 1, 1913

By J. Szekely, G. P. Martins

A formulation is given and a general analytical solution is presented for the problem of spherical phase growth in multicomponent systems. The results are valid for describing the rate of bubble growth in the absence of translational motion and, therefore, should be relevant to heterogeneous nucleation processes. Typical worked examples are given, which include bubble growth due to the simultaneous diffusion of hydrogen and nitrogen in molten steel, and the growth of CO bubbles in steel, due to the reaction: C + 0 = CO. The calculations predict that the presence of additional components would enhance the growth rate and also increase the absolute rate at which the individual components are transferred into the bubble. These findings should be relevant to degassing processes. THE problem of spherical bubble growth in the absence of translational motion is appropriate to the description of the heterogeneous nucleation and subsequent growth of gas bubbles while attached to a solid surface. Such problems are of considerable practical relevance to various vacuum degassing and steelmaking processes where bubble nucleation and subsequent growth play an important part in the overall reaction mechanism. A definitive formulation of spherical phase growth has been given in the now classical paper by Scriven1 and the analogous problem for solid phase growth has been discussed by Horvay,2 furthermore a thorough review of the relevant literature has also become available.3 All this previous work was concerned with one component or binary systems. The purpose of this paper is to show that the technique developed by Scriven may be generalized to alow the consideration of multicomponent systems. The results of this generalization would be particularly relevant, as gas bubble nucleation in the metallurgical systems previously mentioned frequently involves the simultaneous diffusion of several components. In the following a general formulation is given and typical worked examples are presented. FORMULATION Consider the growth of a spherical gas bubble due to diffusion in a quiescent liquid of infinite extent, as sketched in Fig. 1. The formulation of such problems requires the statement of the following conservation equations relating to the liquid phase: Equation of continuity Equation of motion Conservation of the diffusing species—Diffusion Equation. The following assumptions are made: a) The fluid is incompressible, quiescent, and of infinite extent b) The bubble is stationary, i.e., it undergoes no translational motion c) Spherical symmetry is observed throughout d) The mass diffusivity is constant e) Chemical equilibrium exists at the surface of the bubble, and any reactions occurring there are fast compared to the diffusion process f) Inertia and surface tension effects are neglected. Equations derived on the basis of these assumptions by previous investigators were found to provide a reasonable representation of bubble growth while attached to a surface in organic and aqueous systems4,5 For gas bubble growth in molten metal systems assumptions a) to d) chould hold reasonably well. The exclusion of chemical kinetics as a possible rate limiting step may not be universally valid, but should hold for many systems operating at high temperatures. The effect of hydrodynamic inertia may be neglected for moderate growth rates; finally, the assumption neglecting the effect of interfacial tension on the bubble growth was made for the sake of mathematical convenience; its inclusion would have required the use of quite cumbersome numerical techniques. While surface tension effects could be appreciable on the initial values of the overall growth rate, especially at low absolute pressures and in case of small bubbles, they are not thought to modify the relative effects present in multicomponent systems, the study of which is the objective of this paper. Within the framework of the above assumptions

Jan 1, 1970