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By Irving B. Cadoff, Ernest Levine

The crack formation and propagation in the single -phase Cu-4 pct Ag alloys were studied. The alloys were loaded in mercury to various stress levels, the mercury was removed, and the specimen examined for cracks. Cracks were found to develop below the fracture stress; the frequency of such cracks increased with increasing stress level. Some cracks were nmpropagative. Fracture in mercury was found to occur by the link-up of cracks formed at various stress levels rather than by the growth and propagation of a single crack. If the mercury environment is removed prior to a critical amount of crack formation, then continued loading results in ductile fracture. The appearance of the cracks at selected grain boundaries is related to the relative orientation of the boundaries, as are the propaga-tive characteristics of the crack. The mercury interaction appears to be one of lowering the strength of the metal-metal bonds in the high-stress area of the grain boundary. GRIFFITH'S microcrack theory1 proposed a critical crack size above which a crack in an elastic material grows with decreasing energy at a stress of From his theory it was proposed that the presence of a liquid tends to lower the surface energy of the microcrack faces2 leading to a decrease in the critical crack size necessary for spontaneous fracture propagation. stroh3 proposed that the stress concentration at a grain boundary due to pile-up may initiate a microcrack at the grain boundary. petch4 and Stroh5 evaluated the stress distribution at the head of a pile-up in a polycrystal-line material and deduced that the critical crack size and hence of is dependent on the grain size. Experimental verification of this dependence was found by petch6 for hydrogen embrittlement of steel. Studies in stress-corrosion cracking7 have provided a picture of fracture which shows that initial separations occur in a scattered, independent fashion in regions of high tensile stress. A minimum or threshold stress is necessary to produce a sufficient stress concentration to initiate frac- ture. These separations join up to form a crack. The extension of fracture is largely discontinuous and consists of a joining up of cracks. In recent worka evidence of this scattered crack network was found in a Cu-Ag alloy embrittled by mercury. For the Cu alloy-Hg couple, the crack path has also been found to be dependent on the orientation of adjacent grains, and with the addition of zinc to mercury a reduction in embrittlement along with a change in fracture morphology was found.9 In this present study, a mercury-dewetting method was used to observe crack initiation and fracture morphology when a Cu-4 pct Ag alloy is deformed in mercury and Hg-Zn solutions. PROCEDURE Specimens of Cu-4 pct Ag were prepared as in previous crack-path studies.' The specimens were heated at 770°C for 24 hr and water-quenched Tension tests using a table-model Instron were carried out in mercury and in various concentrations of Hg-Zn. Loading was in steps up to the fracture stress, with the load being removed and the specimen examined for surface cracks at each step. The specimens were dewetted after each load to permit examination of the surface structure and rewetted prior to continued loading. The specimens were wetted by electro polish ing in phosphoric acid, rinsing in alcohol, and then immersing in a pool of mercury. Dewetting was accomplished by flame heating the specimen for 30 sec in a vacuum. Some surface contamination was found, but not enough to obscure crack configurations and grain boundaries. RESULTS Fracture Characteristics in Mercury. Fig. 1 is a stress-strain curve showing the progressive step-wise loading of the specimen. As may be seen from the graph, the first position stopped at a is at a stress 5000 psi below the expected fracture stress of 25,000 psi. Examination of the specimen after removal of mercury showed only one crack. The appearance of this crack at a stress far below the fracture stress of this alloy in mercury did not affect the stress-strain curve in any manner. The specimen was then recoated with mercury and deformation was continued (curve b, Fig. 1) raising the stress by 4000 psi, and the same procedure re~eated. The initial crack was located and appeared as in Fig. 2 (crack lb). In this figure the crack is

Jan 1, 1964

By E. M. Tory, P. T. Shannon

An analysis of batch and continuous thickening in terms of the movement of planes of constant concentration (i.e. continuity waves) is presented. Use of solids flux as a primary variable greatly facilitates the analysis and clarifies the relationship between batch and continuous thickening. An "ideal" slurry is defined as one whose settling rate is a function only of the local solids concentration. An analysis of continuous thickening of this ideal slurry in an ideal thickener explains many aspects of the steady — and unsteady — state behavior of real slurries, such as the main features of a thickener's "solids profile" (including the break attributed to rake action), the sudden appearance at abnormally high feed rates of a zone of constant concentration and the velocity with which it rises, and the effect of detention time at constant weight of sludge per unit area. Where deviations exist, they are explained in terms of the batch settling behavior of real slurries. The purpose of this paper is to interpret continuous thickening phenomena in terms of batch settling behavior. Both types of thickening may be considered as the process of propagating concentration changes, due to the downward movement of the solids, from the bottom of the settling vessel upward through the slurry.' These concentration changes may be either finite or infinitesimal as in the case of the propagation of a continuous concentration gradient. The slurry itself may be moving downward as in the case of continuous thickening. The downward velocity of the slurry may be such that the concentration changes being propagated up from below remain stationary relative to the thickener walls. This is the case for steady-state thickening. It seems appropriate to analyze continuous thickening in terms of the movement of planes of constant concentration. This has already been done for batch settling."3 Although our main interest is in real slurries, there are certain aspects of both types of settling which can be deduced from a theoretical analysis of highly idealized systems. To this end, an "ideal slurry" is defined as one for which the dimensionless settling rate at any point is a function only of the local solids concentration.1,2 An "ideal thickener" is one in which there is no radial variation in either the solids concentration or in the downward component of slurry velocity. The underflow outlet is a point sink. It is to be expected that the behavior of non-ideal systems will deviate in some measure from theoretical results. However, the same characteristics which cause deviations in continuous thickening should be evident in batch settling, permitting a rational explanation of the former in terms of the latter. PREDICTED RESULTS FOR AN IDEAL SLURRY IN AN IDEAL CONTINUOUS THICKENER General Theory: In continuous thickening, the downward solids flux (mass/area-time) relative to the thickener, G, results from two different

Jan 1, 1967

By H. S. Thomsen, W. C. Duesterhoeft, R. E. Hartline

The attenuation and phase shift which formations produce in the electromagnetic field of an induction-type electrical well-logging instrument are great enough to substantially affect the response of the tool to formation conductivity under normal logging conditions. The application of the general equations for the propagation of an electromagnetic field in a conductive medium to the transmitter-receiver coil pair of an induction-logging-tool coil system gives an expression for the response which properly takes the propagation effects into account. A comparison of a calculation of this type with the response computed from the commonly used geometric factor concept, which does not include the propagation effect, leads to a factor Go representing the ratio of the responses computed by the two methods. The value of Go decreases not only with increasing formation conductivity, but also with increasing transmitter-to-detector coil spacing. For a single coil pair with a 40-in. spacing, the value of Go is 0.972 in a 20-millimho/m formation. The value is reduced to 0.915 and 0.812 for conductivities of 200 and 1,000 millimhos/m. As a result, the basic signal generated by the induction-logging coil system is not linearly related to formation conductivity as expected from the geometric factor concept. A uniform conductivity scale can be obtained only by adding a suitable nonlinear element to the recording system. The addition of auxiliary coils, having spacings less than the main-coil span, to achieve focusing results in an even greater departure of the basic signal from linearity with conductivity. The solution of the field equations near the interface between two formations of different conductivity gives the curve shape on an induction logging tool in crossing the interface. The addition of auxiliary coils to achieve focusing can add anomalous character to the curve shape in crossing the interface, which might be mistaken for lithological detail. Preliminary calculations which include the propagation effects in the determination of the conductivity correction for thin beds lead to correction factors which are substantially smaller than those obtained from geometric factor considerations. It is apparent that thin-bed corrections derived from geometric factor calculations are of doubtful validity. INTRODUCTION Although the electromagnetic induction type of electrical well log has been used for a number of years and has gained general acceptance in quantitative well-log interpretation, no technically complete investigation of the mechanism and of its operation has been published. The studies which have been presented are based upon the premise that neither the shape nor the intensity of the induction field of the logging tool is in any way affected by the electrical characteristics of the formation. From the inception of induction logging it has been recognized that under some formation conditions the performance of the instrument could be expected to be substantially different from that predicted by the simplified analysis. This anomalous performance has been called "skin effect" since it is the result of the same phenomenon which causes high-frequency alternating currents to flow only near the surface of metallic conductors. In the range of conductivities encountered in the sediments, the formation actually does not exhibit the sharply defined conducting "skin" shown by metals. The gradual modification of the distribution of the currents in the formation, produced by the induction field of the logging tool, is the direct result of phenomena associated with the propagation of the electromagnetic field through the formation. Therefore, it can be much more appropriately described as the "propagation effect". One purpose of this paper is to review the results of a solution of the equations for the performance of a single transmitter-receiver coil pair induction-logging system which takes into account the propagation effect, showing the manner in which the tool performance established by this analysis differs from that derived from the less comprehensive analyses currently in use. PRINCIPLE OF OPERATION OF THE INDUCTION LOGGING INSTRUMENT The high-frequency alternating current which is maintained at a constant value in the transmitter coil

By G. K. Manning, A. R. Elsea, C. R. Simcoe

Boron increases the hardenability of hypoeutectoid steels by decreasing the nucleation rate of ferrite and bainite. It is postulated that concentrations of lattice imperfections, such as exist at the grain boundaries, furnish the necessary energy for nucleus formation. Boron, because of its atomic diameter, will concentrate at lattice imperfections where sites of suitable size are present. Boron will decrease the energy of these local areas by occupying these sites. This mechanism accounts for the large increase in hardenability observed with small amounts of boron. The loss of the boron hardenability effect and the boron precipitate formation are explained on the basis of increased concentration of boron at the grain boundaries either with increasing boron content of the material or with increasing temperature. COMMON alloying elements affect both the nucleation and growth rates of the austenite decomposition reactions.' This effect is largely a result of the slow diffusion rates of these elements. Although a small addition of boron markedly increases the hardenability of steel, the diffusion rate of boron, which is of the same order of magnitude as that of carbon, can hardly account for this effect. An addition of boron in the range of 0.001 to 0.003 pct is about as effective as an addition of 0.30 pct Mo, 0.40 pct Cr, or 1.25 pct Ni in increasing the hardenability of a 0.40 pct C steel;' however, increasing the carbon content of the steel decreases the effectiveness of the boron addition."' The difficulty in understanding why so small an addition of boron can replace much larger quantities of the more strategic alloys, together with the erratic behavior sometimes encountered in boron-treated steels, has interfered with their general acceptance by industry. In the belief that an understanding of the mechanism by which boron increases the hardenability of steel should lead to a more general acceptance of boron-treated steels, a research investigation to determine this mechanism was undertaken at Battelle Memorial Institute under sponsorship of Wright Air Development Center. Experimental Work In order to study the effect of boron on the transformation of austenite to ferrite and bainite, a group of steels was made with a basic composition similar to that of the SAE 8600 series. This base composition was chosen because it has sufficient hardenability to permit accurate measurement of the times required for transformation to start at various temperatures. The chemical analyses of the steels used in the first part of this investigation are listed in Table I. These steels were made as 200 lb heats in an induction furnace. The furnace charge was Armco ingot iron with the alloying elements added as ferroalloys. After the alloy additions were made, the heat was deoxidized with 0.125 pct Al. A 100 lb ingot was cast and an addition of 0.003 pct B, as ferroboron, was made to the metal remaining in the furnace. This metal was cast into a second 100 lb ingot. The ingots were forged to 11/4 in. diam bar stock from which end-quench hardenability specimens were obtained. Part of this material was further reduced by hot rolling to lx¼ in. bar stock from which specimens were obtained for isothermal transformation studies. Studies of Nucleation and Growth: End-quench hardenability tests were performed on these steels, using an austenitizing temperature of 1600°F. The hardenability curves, shown in Fig. 1, indicate that boron treatment resulted in considerable increase in hardenability of the steels. Any such change in hardenability must result from a change in the transformation rate of the austenite, and these rate changes can be established readily by isothermal transformation studies. Isothermal transformation studies were conducted on these steels as follows: specimens were austeni-tized at 1600°F for 15 min, transferred to a lead bath operating at a constant subcritical or intercritical temperature, held for various lengths of time, and water quenched. The specimens were sectioned for metallographic examination to determine the amount and the type of transformation products present. In order to determine the effect of boron on the formation rate of ferrite, isothermal transformation tests were made on the 0.20 pct C steel in both the boron-treated and boron-free condition at an intercritical temperature of 1375°F where ferrite is the only decomposition product of this low carbon austenite. The results of these tests are shown in Fig. 2, where the percentage of ferrite formed is plotted as a function of time at temperature. It is apparent that boron markedly decreased the transformation rate of austenite to ferrite at this temperature.

Jan 1, 1956

By A. L. Barnes, A. M. Rowe

A heat transfer study was made of hot gas injection into oil shale through wells interconnected by vertical fractures. This analysis involved the simultaneous numerical solution of a nonlinear, second-order partial differential equation that describes two-dimensional conduction heat transfer in oil shale and a nonlinear first-order partial differential equation that describes convection heat transfer in the fractures. Three nonlinear, temperature-dependent coefficients were used in this work; they are thermal conductivity, thermal capacity and retorting endothermic heat losses of oil shale. Vertical fractures were considered to be of finite height. Although vertical conduction heat transfer was not considered, an estimate of the error resulting from this limitation was made. The effects of injected gas temperature, injection rate, system geometry, cyclic injection and time upon retorting efficiency were investigated. Results from this study show that the rate of retorting oil shale is a direct function of both injection temperature and rate, and the theoretical producing air-oil ratio:(AOR) is an inverse function of temperature. Retorting rates are constant until "breakthrough" of the 700 F isotherm at the producing well, assuming constant injection parameters. Retorting rates for bounded systems are higher than the analogous unbounded systems and likewise AOR's are less. The use of an alternating injection-soak routine with high injection rates is less efficient than continuous injection at lower rates. These results indicate that injection temperatures on the order of 2000F or greater may give theoretical AOR's in the economic range. INTRODUCTION Over half of the known oil shale reserves are located in the U.S., and most of them lie in the Piceance Creek basin of Western Colorado. The Colorado oil shale outcrops on the edges of the Piceance Creek Basin. At the outcrops the shale beds are relatively thin, from 25 to 50 ft thick. In the center of the basin the oil shale is as great as 2,000 ft thick and is covered with 1,000 ft of overburden. It has been estimated that there are over 1,000 billion bbl of oil in shales having an oil content over 15 gal/ton in this basin. Oil shale does not contain free oil but an organic matter called kerogen. Kerogen yields petroleum hydrocarbons by destructive distillation. It must be heated to approximately 700F, at which temperature it decomposes into shale oil, gases and coke. The U.S. Bureau of Mines and, more recently, oil companies have conducted considerable research on surface retorting methods to economically recover oil from this shale. Another approach to exploit the oil shale deposits, in particular that portion having 1,000 ft of overburden, is to retort the oil shale in place and produce the liquid and gaseous hydrocarbons through wells drilled into the shale. Some research has been done on this approach.l,2 There are several variations to the in situ retorting approach. These variations fall into one of two groups, depending upon the geometry of the system: (1) retorting in a highly fractured or broken up matrix; (2) retorting from single fractures between production and injection wells. The latter is the group studied. Several investigators,3-6 using various assumptions, have studied flow of heat through horizontal systems. The objective of this work was to make a heat transfer study of in situ retorting oil shale by hot gas injection through wells interconnected by single vertical fractures of finite height. The oil shale thermal conductivity, thermal capacity and retorting endothermic heat losses were considered to be functions of temperature. A knowledge of the

Jan 1, 1969

By R. M. Raymond

The Mining Section of The National Safety Council recently sent out a questionnaire to operators, regarding the class of rope used, specifications required or obtained, factors of safety observed, methods of fastening ropes, lubrication, inspection, and points observed when rope is to be discarded. The answers received from this questionnaire, largely from metal mines, give interesting information, from which recommendations for safety practice on hoisting ropes are drawn. Depth of Mine The depth in the majority of cases noted is from 1000 ft. to 1500 ft. (304 to 457 m.) and records come from a number hoisting from depths of 2000 to 3000 ft. Hoisting is generally done in balance, with a few companies using counterweights. Seldom, more than two shifts are occupied in hoisting. A number of large operators limit the shift for engineers to 6 hr. A few of the larger operators have separate hoists for men and supplies, with a higher class rope for men. The range of loads varies from 7 to 17 tons and greater in a few cases, with a balanced weight of 4 to 7 tons. Size or Drums and Sheaves The size of drums and size of sheaves are generally in accordance with recommendations of rope manufacturers. Only one-half of the operators use grooved drums; one, The Sulphide Corpn., New South Wales, uses wood-lagged drums. Very few operators have drums capable of holding all the rope in a single wrap. Cone drums or cone and cylinder drums, in the mines heard from, are very rare. A few mines of shallow depth use a small drum and large-sized sheave. While this may be allowed, and in some cases is all right, the size of drum and sheave should be fully equal to that recommended by the rope manufacturers and should be at least 60 to 100 times the diameter of the

Jan 1, 1923

By Ernest A. Kaarsberg

This paper presents the results of studies of the elasticity of some isotropic and anisotropic rock samples based on longitudinal- and shear-wave pulse velocity measurements. Experimental evidence from velocity measurements on isotropic steel samples is also presented to show, within error limits, that any two of the elastic constants required to completely describe the elasticity of an isotropic solid can be obtained from any two of the following four velocity measurements: longitudinal "rod,' "plate," extended medium (infinite medium equivalent), or shear wave. Measurements of three of these velocities in an approximately isotropic basaltic rock sample are used to illustrate this application to this type of rock. For the anisotropic study, a suite of Colorado oil shale samples is used. These rocks exhibited transverse isotropy. The five elastic constants required to completely specify this type of anisotropy are obtained from longitudinal- and shear-wave pulse velocity measurements made in directions parallel, perpen-dicular, and at 45° to the bedding plane. Density, velocity, and elastic modulus relationships among these shales are also given. Duvall 1 has described a method for determining the elastic constants of isotropic and, in two cases, anisotropic rock samples. This method is based on ultrasonic pulse techniques and on resonance-frequency measurements of rock samples in the shape of rods (diamond drill cores). Rock samples, however, are not always available in rod form. When this is the case, other methods can be used to study their

Jan 1, 1969

By Douglas Bunting

THE first presentation of this paper was before the Pennsylvania Anthracite Section of the Institute in May, 1914, after which a committee was selected to verify and add to the data contained in the original paper. The author is indebted to G. W. Engel, H. W. Montz, R. V. Norris, and H. H. Otto, of this committee, for additional information. I also wish to acknowledge the courtesies extended me by a number of the mining companies for information relative to accidents, systems of proving, and mining practice. The paper should bring forth additional criticism and recommendations, which will be of value in establishing future practice relative to this subject. Throughout the northern anthracite field of Pennsylvania glacial and alluvial deposits of sand, gravel, and clay exist in varying quantities. The extent and character of these deposits are described by N. H. Darton in Bulletin 45 of the U. S. Bureau of Mines, entitled, Sand Available for Filling Mine Workings in the Northern Anthracite Basin. It is estimated that the northern field contains 10,000,000,000 tons of these deposits, or a sufficient quantity to cover the 176 square miles of coal area to a depth of about 25 ft. These deposits of sand, etc., overlying the coal measures attain a maximum depth of more than 300 ft., and are usually saturated to such an extent as to render them semi-fluid. It is .this condition of fluidity that limits the mining of coal seams cropping in or in close proximity to these deposits, and it is in the interest of safer and more efficient mining methods under these conditions that the study of this -subject is here presented. The dangers incident to mining under deep deposits of sand have long been realized by operators in the northern anthracite field, and much has been done to prove the contour of the rock and vein croppings underlying these water-bearing deposits of sand and gravel.

Jan 1, 1915

By R. M. Raymond

The Mining Section of The National Safety Council recently sent out a questionnaire to operators, regarding the class of rope used, specifications required or obtained, factors of safety observed, methods of fastening ropes, lubrication, inspection, and points observed when rope is to be discarded. The answers received from this questionnaire, largely from metal mines, give interesting information, from which recommendations for safety practice on hoisting ropes are drawn. Depth of Mine The depth in the majority of cases noted is from 1000 ft. to 1500 ft. (304 to 457 m.) and records come from a number hoisting from depths of 2000 to 3000 ft. Hoisting is generally done in balance, with a few companies using counterweights. Seldom, more than two shifts are occupied in hoisting. A number of large operators limit the shift for engineers to 6 hr. A few of the larger operators have separate hoists for men and supplies, with a higher class rope for men. The range of loads varies from 7 to 17 tons and greater in a few cases, with a balanced weight of 4 to 7 tons. Size or Drums and Sheaves The size of drums and size of sheaves are generally in accordance with recommendations of rope manufacturers. Only one-half of the operators use grooved drums; one, The Sulphide Corpn., New South Wales, uses wood-lagged drums. Very few operators have drums capable of holding all the rope in a single wrap. Cone drums or cone and cylinder drums, in the mines heard from, are very rare. A few mines of shallow depth use a small drum and large-sized sheave. While this may be allowed, and in some cases is all right, the size of drum and sheave should be fully equal to that recommended by the rope manufacturers and should be at least 60 to 100 times the diameter of the

Jan 1, 1923

By Howard Steven Strouth

The Blind River mining camp in Canada is all set to stage a major revolution. Enthusiasts on the scene say it will bring large-scale mining to North American uranium operation. If orebodies already discovered live up to their promise, it will be anything but the usual business of a few men handpicking orebearing rock out of small mines. Because of the geological structure of the region referred to generally as the Algoma district the ore may prove an extremely lucrative enterprise for years to come. The present center of activity is in Ontario about 75 miles east of Sault Ste. Marie, and just north of Lake Huron. It stacks up as one of the large uranium discoveries in the Western Hemisphere. For a change modern mining machinery working against large ore faces of predictable grade will enable mine operators to send a product to mills of several thousand tons daily capacity. Ore shapes-up as worth more than $20 per ton. Already, many millions of tons of ore have been outlined and apparently reserves are sufficient to keep the proposed large mills going for decades. And the end is not yet in sight. This region in the Sudbury subdivision has been known for decades as having occasionally rich but sporadic occurrences of nickel, gold, pyrite, and other minerals. Because of the unpredictable mineralization for more than 80 miles along the contact line of a huge reversed "S" there was no record of successfully organized mining in the district-until the present one.

Jan 5, 1955

By William Kent

William Kent, Pi.~t~bIJrQh, Pa.: The steel rnanufac.tnret of this country nlust ever he grateful to Dr. Dudley for his painstaking and conscientious endeavor to estaldish the relation between the chemical analysis and the wearing capcity of steel rails. They tnust thank him for the vast array of $acts he presents, and for having given them sixty-four analyses with which to combat his own conclusions and to establish their own, which are entirely opposite to his. In Dr. Duclley" discussion of his former investigation, at the Pittsburgh meeting, he said, "If you do not like my conclusions, draw your own conclusions." I have studied his last paper as thoroughly as the limited time since I received it would adruit, and have drawn some concluvions which I will first state, and then attempt to demonstrate. Briefly stated, my conclusions are: lst, That as far as these 64 analyses reveal anything of service to railmakers and cotsumera, it is that within the following chemical and physical limits, viz., Carbon,..0.20 to 0.60 Pisovphorue ,..0.026 to 0.146 Silicon,.. 0015 to 0.480 BInnganese.......0.262 to 0 880 Phosl~horus un~ts,..20.3 to 6.72 Bending weight,. 2270 lbs. to 4260 Ibs. Drfl~ctinn,.. 13O to 190° or in other words within the limits of rienrly the whole range of the chenlical and bending testa of these 6-2 mils: the wearing capacity bears no relation at all to mrbon, to phosphorus, to silicon, to mnnganese, to phosphorus units, to bending weight or to deflection or if there is any relation between the wearing capacity and thest! six or sr!ven variables, it is so obscured by the action of other cause or variat~les not yet known, that such relation cannot be expressed by any practical formula. 2d. That the difference in wearing capacity of these 64 rails was not due to unrbon, to phosphorus, to silicou, to manganese, or to anj combinntion of these four elements, but that it was due to some other cause or cornbination of causes, of which Dr. Dudley's whole iuvestigtion furnishes 11s no clue whatever. A few of the nlarry possible causes I lnay name : sulphur, copper, oxide of iron inclossl air or other gases, orerblowing, underblowing, oyrhaiting, undcrIreatinp, too hot-finishing, too cold-finishing, cold-straightening, toc great or too litkle rductiun hlu the rail to the ingot, or the portion

Jan 1, 1881

By Henry H. Otto

The anthracite industry can be divided into two parts—the underground, or mining, and the outside, or preparation or manufacture. To understand recoveries in the two branches, some of the history of the industry and the changes that have taken place in the past century should be considered. It is a long step from 1807, when 55 tons were produced in the Wyoming field, to 1917, the peak year, when 80,841,223 tons were shipped to market from all the fields. In 1820, the Lehigh Coal Co., the predecessor of the Lehigh Coal & Navigation Co., shipped 365 tons in arks down the canal of the Lehigh Navigation Co. The Schuylkill field was not opened until 1822, when 1480 tons were shipped. The Wyoming field really became a producer in 1829, when 7000 tons were mined and shipped. It is well to note, at this time, the passing of the Coleraine colliery after a life of 88 years; in collieries of this age will be found the romance of the region, as well as the history of the changes to date. Mining Methods In the Lehigh region, the first coal came from the old quarry mines at Summit Hill; a little later the open-cut workings, or quarries, east of Jeansville, and near Beaver Meadow were opened. In the Wyoming field, it was necessary to resort to underground mining almost from the very first. Ashmead1 has described the changes in outside preparation methods, dl tending to increase the percentage of coal shipped to market. A description from the days when the lump coal was raked and screened out in the quarries or mines, to the modern breaker of today, shipping as high as 6000 tons of at least eight sizes of coal in an 8-hr. day is a very interesting story. Each size is a step toward increasing the yield from the property. With the belief that the supply was inexhaustible, the early mining was conducted with the thought of getting the maximum amount of coal on first mining. The superintendent was his own foreman and engineer.

Jan 1, 1925

By W. M. Courtis

. There seems to be a well-established belief that there is an indescribable something in the appearance of gold-quartz not to be learned from books, that enables those who are fortunate enough to have acquired the power to recognize this characteristic, to pronounce at once that a certain quartz will or will not pay. The stronger this claim is made, the more certain is the claimant to be one of the self-styled practical miners. After several years spent among the gold-mines of California with practical and professional gold-miners, I have come to the conclusion that very few care to risk an opinion on a piece of quartz until some of it has been "horned out." Nevertheless, there is what the miners call a " kindly " appearance, that is more often followed by good results than is a vitreous, water-wet-looking quartz. A dark, resinous quartz seems to be most in favor, but there are so many exceptions that even quartz as " white as a hound's tooth " produces gold in some mines.. The ribbon-quartz, a laminated variety, separated by thin talc or chlorite partings, has a well-known good name. The slides of rich quartz specimens show that this parallelism is a microscopical characteristic of the only macroscopical distinction that, as a rule, these quartzes show. This is shown by Nos. 12 and 13, photographs of the richest quartz, that averaged $65 per pound. It is noticeable, also, in Nos. 7 and 9, and others. Dr. Hensoldt, of Columbia College, who prepared, excellently, a large number of my slides, and whom I have to thank for descriptions and suggestions, says of Nos. 12 and 13: "This variety of quartz differs considerably, microscopically, from the others of your locality, and is, in more than one respect, remarkable. Like the

Jan 1, 1890

By Claude P. Heiner, Carl S. Westerberg

OBSERVATION of the clinkering action of coal from the Castle Gate D seam in underfeed stokers over a period of years has given rise to the present investigation of the effect of bony coal on clinkering. Some very costly examples of slagging clinkers in particular cases have been of especial interest to the authors. In such cases coal analyses and ash-softening and fluid temperatures have been found of little value. In general, it was noted that slagging was accompanied by a somewhat higher ash content of the stoker slack, and the suspicion naturally arose that foreign matter was the troublemaker. One would naturally suspect bony coal and rock impurities because of their occurrence and prevalence within the seam and the relative absence of sulphur or other impurities in the coal mined. The test results given herein indicate that the concentration of the bony coal and rock impurities in the coal determines the clinkering tendencies of the ash during combustion. CASTLE GATE D SEAM Extending from the Utah-Colorado line near Grand Junction, Colo., westward to Greenriver, Utah and thence in semi-circular form north and westward to Castle Gate, and from there southward to Mt. Hilgard in central Utah, is a line of nearly perpendicular cliffs, composed of interbedded massive sandstone and shales, making up the coal-bearing horizon of the Mesaverde formation of Upper Cretaceous age. The cliffs face roughly concentrically toward the south and southeast and the strata, with conformably enclosed coal beds, gently dip away from the face of the cliffs and at right angles to their front line. Back of these cliffs the mountain masses rise to an altitude of from 8000 to 10,000 ft. above sea level. Stretching away from their foot is a great shale plain, on which the towns are situated and over which the railroad lines and highways run. The Castle Gate mines enter the coal beds at their outcrop; the workings extending within a particular coal bed away from the outcrop and under the mountain mass back from the cliff line (Fig. 1). Throughout the Mesaverde formation in the Castle Gate general area, there are from two to five workable coal beds. Usually not all of these are coincidentally of workable size and merchantable quality throughout any given large tract. In the Castle Gate mine area, the base of the Mesaverde horizon and coal measures is marked by a massive, cliffmaking, gray sandstone bed 6o to 8o ft. thick. Locally this is referred to as the "Castle Gate sandstone floor." Frank R. Clark, in U. S. Geol. Survey Bull. 793, designates it as the "Aberdeen sandstone." At Castle Gate the various coal beds are designated by the letters A, B, C, etc., commencing with the lowest bed. Fig. 2 is a graphic generalized vertical section, compiled from physical exposures

Jan 1, 1941

By John W. Cahn

Tile avevage value of the mean curvature of surfaces in a specimen can be precisely delermined by sitrlple measurements performed on random sections or on 1 vojectiotzs of these surfaces. For surjaces enclosing particles, the quanlity is sllown to be velated to the probable tlurrrhev ot particles intevcepted by a random platne and, under certain conditions, to the perimeter of their Projected image and to the increuse in surjace area when the particles grow. Many of the velalionsl~ips are valid for any shape or size of the particles. THE recent growth of the field of stereology or quantitative microscopy is largely the result of the discovery of a limited number of rigorously defined geometrical parameters that can be precisely measured on random sections or projections of a structure without assumption about particle shape.' Such parameters have been the volume fraction and surface area and line length in a unit volume. The present paper introduces the average of the mean curvature of surfaces in a volume, and shows that it can be rigorously measured by counting methods alone. AVERAGE CURVATURE ON A PLANE Consider a curve y = v (x) on the xy plane. The curvature Kp in the plane at any point is given by Kp = (dZy/dx2)/[1 + (dy/dx)2]3/2. The average curvature along the curve may be defined as Kp = (1/L) fKpdl |1] where dl = [(dx)' + {dy)2]1/2 is the length of an element of the curve and .(dl = L is the total length of the curve. The integral on the right-hand side of Eq. [l] will be called the total curvature, It is dimensionless and readily evaluated by substituting d = arctan (dy/dx) to give ah which is the change in direction of the tangents to the ends of the curve, Fig. 1. Hence, Kp = (1/L)(?h) [2] It can also be seen that Eq. [2] is applicable in the limit of sharp corners. Even though the curvature is infinite at a corner, f Kpdl remains integrable and equal to the change of angle. The signs of the quantities Kp and dl are arbitrary and, if the areas adjoining the curve are equivalent, there seems to be no compelling reason to fix the signs. For a closed curve, however, it becomes worthwhile to use the signs to distinguish among different types of areas or phases enclosed. For such a closed curve AO = t2r and As a convention, we shall take the direction of the integration along the curve in such a way that the area or phase under consideration (henceforth called a) is kept to the left side of the curve, Fig. 1. Then Kp is positive where the curve is concave and negative where the curve is convex. For a closed curve Ad - +2n if the curve encloses a, and Ad = —2n if the curve is surrounded by a. PLANAR SECTIONS OF THREE-DIMENSIONAL STRUCTURE OF ISOLATED a PARTICLES Consider next a planar section of a microstructure containing particles of a in a matrix. We place no restriction on shape of connectedness of these particles, and begin by considering the curvature of only the boundary between a particles and matrix' Clumps of contiguous a particles are then treated as a single a particle. The two-dimensional section will show in a unit area na simple closed curves enclosing a particles and nh closed curves of holes, in-

Jan 1, 1968

By G. R. Gardner, D. H. Davis

Increasing realization of the importance of dust control, and the recommendations of various agencies, have led the mining industry to become actively concerned with this problem. The background and necessity for adequate dust-suppression measures have been discussed in a number of publications, including those of the U. S. Bureau of Mines, and the use of spray water to reduce dust at the face and on roadways has been recommended. The problem resolves itself into obtaining adequate dust reduction at a reasonable cost. Inasmuch as the term "adequate dust suppression" has never been clearly defined, nor have permissible limits of dustiness (in terms of dust count) been established, it is apparent that any method selected may be required to meet additional demands. Until the industry has been given some indication of permissible limits of dustiness, no permanent solution is possible. Progress will be somewhat handicapped until such information is available. In addition, dust reduction must be obtained without the addition of any excessive moisture to the coal, since consideration must often be given to: I. Quality standards, particularly reduction in heat value. 2. Handling characteristics, particularly in regard to unloading from railroad cars and bins. 3. Application of dry methods of coal cleaning. 4. Necessity for fine screening within specified limits of oversize and undersize. Little detailed information is available as to the advantages and disadvantages of the several methods of water distribution, the location and protection of sprays, operating data on pressure, quantity of water, and so forth, and results obtained. In 1940 an investigation was undertaken to determine and evaluate the principal factors involved. This paper constitutes a progress report on this work and cannot in any way be regarded as complete on any one of the several phases. Classification of Dust Sources The various sources of underground dust may be classified as primary or secondary. A primary source is one associated with appreciable degradation of size, that is, where the greater part of the actual fines capable of becoming air-borne dust are produced. A secondary source may be considered as one in which the greater part of the fines have been produced at some previous operation and are in such condition that they can be dispersed as air-borne dust. These conceptions appear to be of practical significance, as experience indicates that when dust is controlled at the primary sources the importance of secondary sources is minimized. For these reasons, investigations to date have been concerned principally with the primary sources of dust, and this paper is concerned particularly with one of these—namely, undercutting. In accord with the foregoing definitions, the sources to which the following opera-

Jan 1, 1942

By G. C. Rauch, T. H. Courtney, J. Wulff

The superconducting behavior of Nb-Ti alloys containing 40 and higher wt pct of Nb and variable oxygen content was studied as a function of thermomechanical processing. Critical current density (Jc) us applied transverse magnetic field (H) data were obtained for 0.010 in. diam wires at 4.2° Kin steady fields up to 120 kOe. The precipitate responsible for increase in Jc in each of the alloys studied was related to niobium and oxygen content. In alloys containing 40 to 60 wt pct Nb with less than about 1600 ppm of oxygen, w precipitation in the range 350° to 450°C appears to be responsible for the maximum value of Jc observed. In alloys of higher oxygen content (-2500 ppm), the oxygen-enriched a phase which precipitates in the temperature range 450° to 550°C is a more effective fluxoid pinner. Maximum Jc in low oxygen (350 ppm) 80 wt pct Nb alloys was achieved by 600°C aging heat treatments. Measurements of resistive critical field also reflect the changes in composition accompanying precipitation in these alloys. It is well known that the superconducting critical current density, Jc, of solid solution superconducting alloys can be increased by precipitation heat treatments.1-4 The precipitate, to serve as an effective superconzlucting fluxoid pinner and increase Jc, must be of proper size and spacing.' Its electronic properties must also be different from those of the matrix.6 As in age-hardenable systems, optimum temperature and time of aging are dictated by the composition and history of the particular solid-solution alloy under consideration. The alloy diagram of Ti-Nb7-9 shown in Fig. 1 is typical of ß-stabilized Ti alloys. Precipitation to achieve high Jc in Ti-Nb and Ti-Ta alloys is usually carried out in what is believed to be a two-phase a + ß region.1,2,4,10 Previous work on Ti-Nb4,11 and on other ß-stabilized systems such as Ti-V, Ti-Mo,12-14 has shown, however, that the first precipitate to appear is not necessarily (Y. Under specific conditions the meta-stable w phase is precipitated instead. A further complication arises in such alloys from the strong influence of contained oxygen on the phase stability and on the kinetics of precipitation.15,16 The superconducting critical current density of Nb-Ti alloy containing less than 36 wt pct Nb has been studied by Vetrano and Boom1 and Kramer and Rhodes.4 The most effective aging temperature was found to be about 425°C; fluxoid pinning was attributed to the precipita- tion of a by Vetrano and Boom and of w by Kramer and Rhodes. Although the latter workers used recrystal-lized material and the former cold-worked, studies carried out in our laboratory lead us to believe that the type of precipitate responsible for increased Jc is unaffected by prior cold-work.17 That other types of precipitates may also be effective, especially in higher oxygen-containing alloys, has been demonstrated by Reuter, et al.2 in this laboratory with the aid of electron microscopy. Reuter et al. found that at an aging temperature of 600°C, fee-TiO is precipitated, resulting in high values of Jc. Even higher values of Jc were observed after heat treatment at 500°C, but the precipitate could not be indexed as fee-TiO. Whether the precipitate was oxygen-rich w or a could not be clearly distinguished. The work nevertheless indicates that appreciable amounts of oxygen alter the nature of the phases precipitated at different temperatures, at least in alloys containing more than 36 wt pct Nb. Since such compositions are more readily worked into suitable wire than lesser niobium content alloys, it was decided to study the response to aging of the alloy compositions reported in the present paper with the hope of clarifying the effect of composition on the precipitation processes responsible for high values of Jc. I. EXPERIMENTAL Nb-Ti alloys containing 40, 50, 60, and 80 wt pct Nb were prepared by are-melting 35 g ingots of iodide crystal bar titanium and electron-beam melted niobium.

Jan 1, 1969

By B. Ramaswami, Y. Nakada, U. F. Kocks

Compression tests were performed on single crystals of aluminum, silver, gold, and a Ag-10 pet Au alloy, with height-to-width ratios from 8:1 to 1:1. As this ratio decreased, so did the amount of easy glide until, for cubic specimens of all the pure materials, it was entirely absent. Heterogeneity of deformation is proposed to he a major contribution to the explanation of easy glide in slender specimens. For comparison, one single-crystal cube of zinc was tested and showed a behavior very similar to that in tension. Beyond easy glide, tension and compression curves are very similar. It is concluded that, in this range, neither grip effects nor orientation change influence the work-hardening characteristics to any significant extent. (121) and (100) crystals of all materials had similar stress-strain curves in tension and compression, except that the stress level of the flat portion of aluminum (109 crystals at high strains mas somewhat higher in compression. These results are at variance with previously proposed mechanisms of orientation dependence by both Hosford and Kocks. The compression tests themselves are described in detail and it is shown that they are essentially frictionless and produce single slip when the crystal is suitably oriented. DEFORMATION in uniaxial compression does not necessarily give the same result as deformation in uniaxial tension, essentially because the boundary conditions chosen are practically always different. 1) The shape and size of the specimens are usually different, and any genuine effect of size on work hardening should thus influence the result. 2) The grip constraints are usually different and can vary substantially for different kinds of tests. If the compression specimen is a thin plate and the friction on the platen is large, the grip contraints are more serious than in tension and lead, in the extreme, to uniaxial strain rather than uniaxial stress. If the specimen is roughly cubical and the friction is low, the specimen is less constrained than in tension inasmuch as displacements in the contact face are allowed. 3) The orientation change of single crystals is of opposite sign in tension and in compression; it is furthermore different in detail, because the relevant orientation in a squat specimen is the normal to the contact face, whereas that in a slender specimen is the generator of the side faces.' The considerable dependence of work hardening on the initial orientation in tension would suggest that the orientation change should also be very important. 4) Finally, localized deformation instabilities found in tension tests, such as necking and Lüders band propagation, are not possible in squat specimens. This is, for some investigations, a favorable consequence of the large grip influence. Even if one is not interested in any of the effects mentioned above, compression tests are often desirable just because the specimens needed are so much smaller and sturdier. For example, they have been very helpful in the investigation of latent hardening by means of alternate longitudinal and lateral compression of cubes,* and for testing

Jan 1, 1964

By G. R. Gardner, D. H. Davis

Increasing realization of the importance of dust control, and the recommendations of various agencies, have led the mining industry to become actively concerned with this problem. The background and necessity for adequate dust-suppression measures have been discussed in a number of publications, including those of the U. S. Bureau of Mines, and the use of spray water to reduce dust at the face and on roadways has been recommended. The problem resolves itself into obtaining adequate dust reduction at a reasonable cost. Inasmuch as the term "adequate dust suppression" has never been clearly defined, nor have permissible limits of dustiness (in terms of dust count) been established, it is apparent that any method selected may be required to meet additional demands. Until the industry has been given some indication of permissible limits of dustiness, no permanent solution is possible. Progress will be somewhat handicapped until such information is available. In addition, dust reduction must be obtained without the addition of any excessive moisture to the coal, since consideration must often be given to: I. Quality standards, particularly reduction in heat value. 2. Handling characteristics, particularly in regard to unloading from railroad cars and bins. 3. Application of dry methods of coal cleaning. 4. Necessity for fine screening within specified limits of oversize and undersize. Little detailed information is available as to the advantages and disadvantages of the several methods of water distribution, the location and protection of sprays, operating data on pressure, quantity of water, and so forth, and results obtained. In 1940 an investigation was undertaken to determine and evaluate the principal factors involved. This paper constitutes a progress report on this work and cannot in any way be regarded as complete on any one of the several phases. Classification of Dust Sources The various sources of underground dust may be classified as primary or secondary. A primary source is one associated with appreciable degradation of size, that is, where the greater part of the actual fines capable of becoming air-borne dust are produced. A secondary source may be considered as one in which the greater part of the fines have been produced at some previous operation and are in such condition that they can be dispersed as air-borne dust. These conceptions appear to be of practical significance, as experience indicates that when dust is controlled at the primary sources the importance of secondary sources is minimized. For these reasons, investigations to date have been concerned principally with the primary sources of dust, and this paper is concerned particularly with one of these—namely, undercutting. In accord with the foregoing definitions, the sources to which the following opera-

Jan 1, 1942

By R. S. Sandhu, S. H. Advani, J. K. Lee, B. L. Aboustit

A comprehensive finite element formulation for thermo-elastic consolidation based on a general variational principle is presented Sample one dimensional problems associated with isothermal consolidation, heat conduct ion, and thermo-elastic consolidation are presented. In addition, evaluations of thermo-elastic consolidation for an underground coal conversion field site are conducted.

Jan 1, 1982