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By H. D. Hagen, C. E. Nelson

14.1-1. Coal Mining. CORPORATE STRUCTURE. Most coal companies that operate surface mines had their beginnings as basically one-man organizations, with all decisions and controls in the hands of the founder. At the early stage of the company development, it is usually quite possible for one man to handle all management functions as the mining operations generally are quite localized and the founder can have a first-hand knowledge of all facets of the operation. However, with continued growth, the entrepreneur finds that he must limit himself more and more to the top level of management and delegate the day-to-day operation to others. An organization must be developed that provides not only for current operations but also for continued growth of the company through acquisition of coal reserves in market areas that the company desires to serve. In general, a successful coal company engaged in surface mining must develop an organization consisting of the following departments or divisions: operations, sales, engineering, exploration, land, purchasing, financial, and legal. Of course, all of these departments are not required in the beginning. When the company is small, there is much overlapping of functions. For instance, the operating department will handle purchases and the engineering department will also handle exploration and land functions. A growing surface-mining company has generally evolved through the various stages of development into an organization that is typical of large mining companies. An examination of a typical company and its various departments and their functions should give an insight into the organizational trends of surface mining companies. Having begun as a typical one-man organization, a company of today can be highly centralized, with firm control of all phases of the company's operations in the executive offices. This is achieved by having all department heads (Fig. 14.1-I), as well as the senior management, based in central offices.

Jan 1, 1968

By G. A. Guess

THIS investigation was started with the idea of determining whether copper-nickel mattes might not have a lower flowing temperature than copper mattes, and thus perhaps aid in accounting for the difficulty so far experienced in attempts at pyritically smelting copper-nickel ores. We have used the term flowing temperature to avoid confusion with the usual melting temperature. The idea at first was that there might be a greater viscosity range in the one matte than in the other. In the early experiments it was in our minds to determine the relative fluidity of the mattes at a given temperature. Looking to this end we tried pouring equal quantities of matte at the same temperature down an inclined graphite slab, and comparing the distances traveled. Results from such experiments were not satisfactory. We next tried pouring equal quantities at the same temperature through a drilled hole in an Acheson graphite crucible, timing the flow with a stop watch, the whole operation being carried out in the muffle. The flowing temperatures of the mattes tried in this way appeared to be about the same, and there was no marked difference in their fluidity when well fused. Oxidation gave some trouble. These experiments finally led to the adoption of the following apparatus which we thought at the time was wholly original with us, but which we have since found was described by W. McA. Johnson.' The tray used was a slab of graphite 8 in. long, 2 in. wide and ¼ in. thick. It had six holes, into each of which sat a cup of Acheson graphite. Centrally in the bottom of each cup was a vertically drilled hole 3/16 in. in diameter and ½ in. long. The mattes to be tested were put into the cups, in a solid piece. The cups were covered with inverted Battersea "A" cups. The tray was put into the muffle of a gas-fired furnace. Supports on .each end held the tray about 2 in. from the floor of the muffle. Udder

Jan 6, 1916

By John Chapman, J. C. Vaughan

Although a considerable amount of practical importance attaches to systems involving gases and molten metals, little is known regarding the effects of alloy elements upon the solubility of gases in liquid iron. The solubilities of hydrogen1 and nitrogen2,3 in pure liquid iron arc known and it has been shown that small amounts of silicon and aluminum3 exert only a small effect upon the solubility of nitrogen but greatly increase its rate of solution. This paper presents the results of a study of the solubility of nitrogen, at pressures approximately one atmosphere, in molten iron containing up to 15.8 per cent silicon. EXPEBIMENTAL METHOD There are two general methods by which the solubility of a gas in a molten metal may be determined. In the first, which Sievertsl employed, the gas is measured from a burette into the enclosure containing the metal and the amount absorbed is found by subtracting from the total volume that of the dead space in the container. The second method, which was used successfully for pure liquid iron, is to expose the molten metal to the gas until absorption ceases, then to solidify and analyze the metal. In either method the stirring produced by inductive heating prevents the development of a stagnant layer at the metal surface and ensures actual attainment of equilibrium. Obviously the second method is accurate only when the saturated metal is capable of solidifying without gas evolution. Since the rate of solution of nitrogen in iron is increased by the presence of silicon, it was to be expected that the rate of evolution would be correspondingly increased and for this reason the first method was selected. A sketch of the furnace is shown in Fig. 1. A small high-frequency coil having 17 turns fitted closely around a fused silica tube, 2 in. in diameter, in which was placed, on a bed of 60-mesh alumina sand, an

Jan 1, 1940

By L. H Levenson, Charles S. Barrett

The orientation of metal crystals and grains, both large and small, can be detcrmined conveniently and accurately without the use of X-ray apparatus. This seems to be appreciated by so few metallurgists that it may be useful to explain in detail the method we have found most satisfactory in the laboratory—the reflection of light from crystallographie etch pits. This note includes a description of a suitable inexpensive instrument and instructions for etching various metals and for plotting the data. As the stereographie projection is used to facilitate handling the data, this note may he considered as an appendix to an earlier review of the metallurgical uses of the stercographie projection.' Various methods involving etch pits have been used by other investigators. Bridgman's method2 consists of attaching the specimen to a sphere (a transparent sphere is convenient4 , holding it at arm's length, and marking a spot on it when it has been turned so that the eteh pits reflect light into the eye of the observer from a lamp standing behind him. It has an accuracy of about 2" and is extrernely rapid. A greater accuracy can be obtained by having the reflected light fall on a screen, as has been done by Czochralski,5 Chalmers,6 and Schubnikov.7 All of these methods have been intended for undeformed single crystals. Tammann and his coworkers3,8 developed a method for estimating the number of grains in a polyerystalline aggregate having orientations in a given region of the stereographic triangle and thus obtained statistical information about deformation and reerystallization textures. While the method has had some use in recent years,9 it is not applicable to the majority of problems in physical metallurgy. Smith and Mehl10 determined orientations by plotting the directions of the sides of individual etch pits on a stereographic projection. The accuracy is limited to about 3" and the method requires careful polishing and high magnification.

Jan 1, 1940

By George R. Mansfield

Interest in the reserves of phosphate rock in the United States and their proper conservation has recently been aroused by hearings held in different parts of the country by the "Joint Committee to investigate the adequacy and use of phosphate resources of the United States." This committee was appointed within a few days after a Presidential message to Congress on the same subject, dated May 20, 1938, and began to function almost immediately. Hearings were held in Washington, D. C., Pocatello, Ida., Wilson Dam, Ala., Knoxville, Tenn., and Lakeland, Fla. The resulting testimony, when published, comprised a volume of 1182 pages.l At the earlier hearings held in Washington and Idaho the seeming disparity between the great reserves of the West and the smaller reserves in the East led to some suggestions as to the desirability of curtailing or even prohibiting the exportation of phosphate rock so that eastern producers, becoming alarmed, cooperated in making available for the use of the committee information hitherto closely guarded. This information has provided an opportunity for new studies by official agencies, for a restatement of the reserves of Florida and Tennessee, and for some modification of figures for the Western States. The writer, representing the Federal Geological Survey, was given free access to the Florida material and has prepared for publication a report,² some features of which are summarized in this paper. The Tennessee material was studied by Dr. G. I. Whitlatch,³ of the Tennessee Division of Geology. Prof. J. Stewart Williams,* of the Utah State Agricultural College at Logan, has published a recent study of the phosphate resources of Utah and the writer has given some further study to reserves of western phosphate from the viewpoint of including material of lower grade than that hitherto considered. Technologic advances in the phosphate industry must be credited with a large share in the expansion of reserves by making available for

Jan 1, 1942

By W. P. Shinn

In a paper contributed by W. A. Goodyear, M.E., on "Water Gas as Fuel," read at the Boston Meeting, February, 1883,* the following statenlent was made: "The latest experiments on a scale of some magnitude in our citier, in the way of heating buildings and furnishing power for manufacturing purposes, have been by the distribution of high-presslire steam through pipes laid in the streets. Hilt these experiments (1) have not hitherto been very successful; and when we consider the high cost and (2) the great and unavoidable loss of heat and power, which always accompany the conveyance of high-pressnre steam to any considerable distance in pipes, to say nothing of (3) certain practical difficulties in the management of the pipes themselves, (4) it is evident that all such methods must eventually disappear before a system which can furnish a cheap gas of great heating power, easily distributed wherever wanted, without requiring pipes to stand pressures of 50 to 75 pounds per square inch, and (5) without keeping the whole mass of ground in the streets through which it passes hot, gratis, for a distance of ten or fifteen feet, in all directions around the pipes!' For the purpose of controverting Mr. Goodyear's statements in regard to steam-distribution in cities, I hare numbered the points made in his indictment, my principal object being, not a professional discussion of the technical and theoretical merits of steam vs. watergas, but a simple statement of facts, in regard to the present state of the street system of steam distribntion. Taking Mr. Goodyear's points in their order: 1. Concerning what he terms " These experiments," saying that they " have not hitherto been very successful," I propose to show, that the problem of stearn-distribution has passed beyond the experimental stage, and that its practical solution is highly successful. This will be shown by the facts hereinafter fully set forth. 2. "The great and unavoidable loss of heat and power whicn always accompany the conveyance of high-pressure steam to any con-

Jan 1, 1884

By George R. Mansfield

Interest in the reserves of phosphate rock in the United States and their proper conservation has recently been aroused by hearings held in different parts of the country by the "Joint Committee to investigate the adequacy and use of phosphate resources of the United States." This committee was appointed within a few days after a Presidential message to Congress on the same subject, dated May 20, 1938, and began to function almost immediately. Hearings were held in Washington, D. C., Pocatello, Ida., Wilson Dam, Ala., Knoxville, Tenn., and Lakeland, Fla. The resulting testimony, when published, comprised a volume of 1182 pages.l At the earlier hearings held in Washington and Idaho the seeming disparity between the great reserves of the West and the smaller reserves in the East led to some suggestions as to the desirability of curtailing or even prohibiting the exportation of phosphate rock so that eastern producers, becoming alarmed, cooperated in making available for the use of the committee information hitherto closely guarded. This information has provided an opportunity for new studies by official agencies, for a restatement of the reserves of Florida and Tennessee, and for some modification of figures for the Western States. The writer, representing the Federal Geological Survey, was given free access to the Florida material and has prepared for publication a report,² some features of which are summarized in this paper. The Tennessee material was studied by Dr. G. I. Whitlatch,³ of the Tennessee Division of Geology. Prof. J. Stewart Williams,* of the Utah State Agricultural College at Logan, has published a recent study of the phosphate resources of Utah and the writer has given some further study to reserves of western phosphate from the viewpoint of including material of lower grade than that hitherto considered. Technologic advances in the phosphate industry must be credited with a large share in the expansion of reserves by making available for

Jan 1, 1942

By W. Mostowitsh

I. Introductory LEAD sulphate occurs as anglesite, and is formed in every roasting of lead sulphides or sulpho-salts containing lead. In smelting in the blast furnace an ore containing natural or artificial lead sulphate, a large part of the sulphur present goes to the formation of the intermediary product matte which requires further treatment for the recovery of the values it contains. It is therefore of importance to study the behavior of lead sulphate at elevated temperatures, both without and with reducing agents, especially as the information available gives data which are more or less conflicting. II. Decomposition of Lead Sulphate by Heat The dissociation of PbSO4 into PbO and S03 or S02 and 0 has been discussed by many metallurgists. The following data are considered to be representative. Doeltz and Graumann1 found that PbSO4 was not affected by heat at 800° C.; that dissociation began at 900° C., and was rapid at 1,000° when the salt lost in 1 ½ hr. 14.3 per cent. of its weight, the dry salt containing 26.43 per cent. SO3. Hofman and Wanjukow2 summarize their work upon the dissociation of metallic sulphates with the statement that the decomposition of PbSO4 begins at 195° C., but progresses very slowly, with the formation of the basic salt 6PbO.5S03 at 705°; that this salt undergoes a transformation at 847°, begins to be decomposed at 888°, to sinter at 896°, and to fuse at 910°; rapid dissociation begins at 952°, and is accompanied by volatilization of PbO; retardations at 958° and 962° indicate an acceleration of decomposition which, however, is not complete. Proske3 found that PbSO4 gave off at 900° C. in 30 min. only 0.63 per cent. of its SO3, and that the loss increased with

Jan 5, 1916

KARL A. PAULY,* Schenectady, N. Y.-We are deeply indebted to Mr. Hobart for a record of the actual experience of the Lehigh Coal and Navigation Co. with electrification. One of the essential features of this test is that it was made under actual operating conditions. In one of the western mining districts I was once discussing the electrification of a large hoist with a mining operator, who told me that they had made a very thorough test and that the results were such as to indicate that electrification was not warranted. When questioned regarding the test, he said that they had called on the mining college in the Territory for assistance, and one of the instructors and a group of students had made the test. They first cleaned the boilers and then operated them at a' continuous load, using the maker's guaranteed steam consumption per indicated horsepower as a guide in estimating the steam consumption under actual hoisting conditions. Such a test is absolutely valueless. The efficiency of the boilers 'is affected by the intermittent demands on the steam. The standby losses, as indicated by Mr. Hobart's paper, are quite equal to the actual fuel consumption required to do the work; very frequently, also, the cost of repairs is either omitted or underestimated. One noticeable feature of Mr. Hobart's tabulation is that there is no mention of steam consumption. Intentionally or otherwise, the steam-hoist builders have befogged the question by making a great point of the steam consumption of hoists. The operator is not at all concerned in steam consumption; it is the actual cost of operation that he is interested in, and it is a comparison between the cost of operation of the two systems, all factors being considered, that should determine the choice. The steam consumption, or its determination by test, is only one step in the problem of estimating the fuel consumption, which, in an actual installation, can be directly measured much more accurately, as was done by Mr. Hobart.

Jan 4, 1918

By Roy W. Wright

Introduction The title of my paper is satisfyingly broad and allows me to touch lightly or dwell at length on virtually any aspect of mining, while endeavouring not to trespass on the subjects of other papers to be presented. However, at this stage in our world history when for the first time we are beginning to take conservation and the welfare of future generations more seriously, I want to concentrate mainly on the question of whether or not there will be the resources of minerals available to sustain mankind's progress in the generations ahead. Metals and the Population Problem The supply of raw materials is of course only one of the fundamental problems that will face future generations: if we assumed that the world population would continue to increase at the present explosive rate, then I believe we can say with certainty that other fundamental problems of much greater significance would arise long before a shortage of raw materials - or other substitutes -had any impact on the progress of mankind. Thus, I must start this paper with the assumption that some equilibrium in population will be arrived at before these other problems overwhelm the world. Will the Metals Run Out? At the 75th Anniversary Meeting of this Institute in March, 1947, Clinton H. Crane, President of St. Joseph Lead Co., prophesied that for the next 100 years there would be enough copper, lead and zinc for every essential need. He defined a need as essential where the qualities of the metal in that use were irreplaceable. Today, except for one or two cases such as lead in lead-acid batteries, few metals have qualities that cannot be provided either by another metal or by another material. It is more a question of what the engineer or manufacturer is prepared to pay for special qualities as compared with using cheaper materials and perhaps a less satisfactory design.

Jan 1, 1971

By R. S. Barneyback

Not much more is known about concrete today than was known to the Romans. For all the research only better tools have resulted to measure the quality of the materials that go into it." In this paper "some of the materials for lightweight concrete and their characteristics are considered and effort is made to indicate their effect on the end result — a structure of lightweight concrete." Lightweight concrete had noble beginnings. It is believed that the first specification for lightweight concrete was written by the Roman Emperor Hadrian in the early years of his reign, 117-138 AD. Hadrian, was an engineer by trade and an Emperor by adoption. He took considerable interest in the structures sponsored during his reign, even to the point of working out the structural details and preparing working drawings for some of the more prominent works in the vicinity of Rome. In order to reduce the dead weight of the 140 ft diam dome of the Pantheon he specified that the lightweight structural concrete members supporting this concrete and tile composite dome were to be fabricated from a concrete containing pumice and scoria. Still standing after 18 centuries of abuse, this structure has been described as the master effort of a great structural genius, the ultimate achievement of Roman engineering skill.' The Romans were the first to employ many concrete techniques we think of as modem innovations. Some unnamed superintendent noted that when a carefully measured amount of pigs blood was measured into each batch of concrete during mixing, the concrete was more durable and exhibited much better resistance to freezing and thawing climates. He no doubt, attributed this success to the appeasement of one of the gods who in return provided protection for the building containing this sacrificial offering in its walls. It is known today that the blood-entrained air in the concrete tends to make mixtures more workable, resistant to moisture penetration and more resistant to frost damage.

Jan 1, 1964

By Earl Oliver

THE term oil property, in this discussion, includes any type of easement or grant under which petroleum might be produced; it ranges from the mere right to drill on undeveloped wildcat acreage up to a fully developed oil property. The values of an oil property, as thus defined, vary widely according to the use for which it is intended, whether it is from the viewpoint of the speculator, the fraudulent stock promoter, the refiner and pipe-line owner, or the oil producer. The market value of a property is usually a combination of some two or more of these influences, and occasionally a combination of all of them, but we prefer to treat each viewpoint as distinct from the others, allowing the reader to make his own combination in such proportions as his inclination and property seem to require. This paper will treat the subject from the viewpoint of the oil producer. However, the other influences have such bearing on the cost of property to the producer and on the price he might obtain by its sale as to warrant brief discussion of them. Speculation, particularly lease speculation, is a parasitic growth on the oil industry, healthy enough, but of no economic value. The class of property usually dealt in for this purpose is the undeveloped lease. Its speculative value may have some relation to its probable productive value, but most frequently this value is the product of temporary excitement due to local development. The lease speculator, seeking out the trend of development or securing early information regarding a proposed test or a new discovery, immediately secures leases whose market value will be increased when the existence of such development becomes more widely known. His profits are purely unearned increment. Not proposing to spend money in exploration, he can afford to compete in purchase with the operator, who, in addition to bonus paid, must spend large sums in testing out his own acreage and that of the nearby speculator as well. It has a tendency to compel unduly high bonuses.

Jan 2, 1920

By A. Patton

Introduction THE use of roll scale in the Bessemer process dates back, to the "best of our knowledge, at least 20 years. It was first used by the Ohio Steel Co.; Youngstown, Ohio (now the Ohio Works of the Carnegie Steel Co.) under the direction of Sam, MacDonald, Superintendent of the Bessemer Department at these works. Two 10-ton vessels and one blowing engine capable of blowing one heat at a time were employed. The object of using the scale was to -shorten the length of the blow; or in other words, to increase the production with the same equipment. Various means were tried out for introducing the roll scale into the bath of molten iron: It was shoveled into the vessel before the heat was charged, so that the metal would flow over the scale; it was shoveled into the bath after the vessel was turned up; it Was dumped into the empty iron ladle by the wheelbarrow-load, and at times wars dumped on top of the molten metal in the iron ladle. But the practice of introducing the scale into the iron ladle had to be abandoned on account of danger from explosions and of skulling the -ladles. It was soon learned that the proper place to charge the scale was in the empty vessel, so that when the molten iron was poured into the vessel it flowed over the scale, causing a considerable reaction to take place before the heat was turned up. Eventually, cylindrical chutes similar to those now in use were installed. Into these chutes the scale is dumped and carried into the empty vessel. Before this convenient means of introducing the scale was adopted, the Ohio Works had satisfactorily demonstrated that roll scale would increase production, by blowing 107 heats in one 12-hr. turn (1,087 tons) with one blowing engine, blowing one heat at a time; whereas, prior to the use of scale, the best practice at these works was about 80 heats under the same conditions.

Jan 2, 1917

By William P. Blake

Copper Basin in Yavapai county, Arizona Territory, about twenty miles southwest of Prescott, is well named. It is a depressed area, and a region of cupriferous impregnation.* The geologic conditions are simple. The foundation rock is a coarse-grained granite and gneiss, in which soda feldspar predominates. There are also dykes of porphyritic rock, and a large quartz vein containing pyrites. Superimposed on this crystalline foundation, we find heavy beds of mechanically formed rocks, conglomerates, breccias, and sandstones, in horizontal layers cropping along the bed of a creek, and apparently the remnants of a much more extended formation, now denuded and largely carried away by gradual atmospheric erosion. The heavy beds of conglomerate are in many places much broken and tilted up, even standing on edge in large blocks, as if they had been lifted by some great convulsion; but the cause is much more simple, being merely the removal by gradual disintegration and erosion of the softened and decayed granitic rock below. The materials of these sedimentary beds are chiefly fragments of granite, gneiss, and plutonic rocks loosely mingled. They are the chief repositories of the copper-ore, which forms the cementing substance. This copper-ore is the blue and the green carbonate, azurite and malachite, and the ore is so generally spread through the mass of the beds that the blue and the green croppings can be seen at a great distance, particularly after or during a shower of rain, when the colors are extremely brilliant and beautiful. The copper carbonate is not only a matrix and a cementing material for the fragments of rock, but it invests and covers these fragments so that only malachite and azurite are visible. The beds are from three to ten feet or more in thickness, and, although seemingly solid carbonate of copper, rarely contain over 12 or 15 per cent. of that metal. Some portions of the conglomerates are much more highly charged with copper than others, and in places the beds are almost without copper. If a lump of the coarse sandstone

Jan 1, 1889

By Jan Wolski

Today's rapidly shrinking world requires a common language of measurements, a consistent system which could be used by everyone. The S.I. system of units is generally accepted as such and is already in use by a great majority of nations in the world. The change to S.I. units is also slowly taking place in U.S. engineering practice. The transition period is difficult and long because it takes time to get familiar with the new system, to start "feeling" values in new units. Instruments, formulas, computer programs, survey grids, etc. have to be converted or exchanged. The transition period should be used not only for substitution of units, but also for rationalization of presently used calculation methods. This paper examines the major parameters of mine ventilation from the above point of view and discusses a system which is much simpler and more consistent than the American Unit System still in use in the United States. In October 1979, the Society of Mining Engineers of AIME decided to introduce the S.I. unit system in all its publications including the periodical "Mining Engineering", and since February 1980 the system has been used consistently, not only in SME publications but in all conferences and meetings organized by this Society. The authors have no intention of explaining the details of the S.I. system in general. Any reader can find this information in many available publications and conversion tables, and in particular in the ASTM Standard for Metric Practice, E380-79. A comparison is made between various units used in mine ventilation from the past and those presently in use. This will allow an easy translation from one system to another, important when reading publications from abroad. S.I. and customary U.S. formulae are shown side by side for easier visualization of similarities and differences. Recommendations for the necessary steps in order to switch from American to S.I. units conclude the paper.

Jan 1, 1982

By F. A. Jerabek, H. L. Hartman

This study presents results of investigations in a small model of segregation in discharged fill slurry, the quantity of solids escaping in the drain liquid, and the relationship of solids to slurry concentration and discharge rate. Compressibilities of fine fill material, in dry and wet states and individual size fractions, are compared. Two terms are frequently used in describing the hydraulic placement of fill material underground: hydraulic stowing is mostly associated with the underground flushing of coarse-sized fill material, such as coal washery refuse; while hydraulic backfilling refers to placement of small-sized fill material, e.g., sand or classified mill tailings, mainly in metal mines. Characteristically, in backfilling, only a few hours may elapse between the time the material is hoisted as ore and redeposited as fill underground. Hydraulic filling was first used about 100 years ago to control subsidence in coal mines. It was subsequently adopted in many mining operations all over the world, but its basic concepts have never been adequately studied and analyzed. This is not surprising, when one considers the number of variables involved in the hydraulic backfilling operation. Recently, much work has been done on the problems of transportation of slurries in pipes. Comparatively less research work has been done concerning the physical properties of fill material (compressibility, cementation, permeability, etc.). Very little work has been done on the problems of fill placing, distribution, and segregation of fill material discharged in the mine void. It is the purpose of this paper to explore two of the basic, lesser known aspects of filling: segregation and compressibility in discharged fill slurry. Difficulties in observing the behavior of hydraulic fill slurry during the pouring operation underground, and insufficient knowledge to conduct any kind of meaningful theoretical analysis, suggest experimental model studies. The tests described in the following sections were conducted in the Rock Mechanics Laboratory of the Department of Mining at Penn State.

Jan 1, 1965

By B. Amadei

INTRODUCTION Laboratory studies on the deformability and strength of intact rocks generally involve the uniaxial compression test, the standard triaxial compression test and direct or indirect tension tests. If [al ,a2 ,a3] are principal stresses [(al>a2>a3)] with compression taken as positive and tension taken as negative, the applied stress field for each one of these tests can be represented as shown in Fig. 1. However, for most in-situ conditions, such as those that exist at any point around an underground excavation, the stress field is truly three-dimensional or multiaxial [(al+ a2+a3)] and none of the tests shown in Fig. 1 can be used to predict the mechanical behavior of the rock. There are special cases for which one of the three principal stresses vanishes. Biaxial loading of rocks in-situ takes place, for instance, when rocks deform and fail in plane stress conditions. This can occur in a free unloaded surface of a rock structure such as in the wall of an underground excavation or a rock slope. Parallel to the free surface, the stress field components can be both compressive [(al>a2>0)], both tensile [(O>a2>a3)], or mixed, one component being compressive and the other one tensile [(U~>O>U~)]. The purpose of this paper is to present the results of 25 true biaxial tests that have been conducted on cubical specimens of Indiana Limestone using the multiaxial cell available at the University of Colorado at Boulder. The tests include uniaxial compression and tension, biaxial compression and combined biaxil compression- tension. Flexible fluid cushions and brush bearing platens were used for compressive and tensile loading respectively in order to minimize loading end effects on the test specimens. The paper begins with a review of previous investigations on the multiaxial behavior of rock. Then, test results are presented in terms of

Jan 1, 1984

By A. T. Peters

DURING an investigation concerning the use of large nozzles for pouring of low-carbon rimming steels, the practical details of which were reported elsewhere, it was noticed that increases of nozzle sizes were generally followed by improvements of slab surface quality. It is the purpose of this note to present the data available and some tentative opinions about this phenomenon. The problem of correlating pouring rates with the metallurgical performance of steels is complicated by several factors. The two most important are; 1) Variations of the steel pouring rate throughout a pour, these being due to the nozzle erosion, which enlarges the bore area, and the dropping ferrostatic pressure in the ladle. The pouring rate is lowest towards the end of a heat when the ladle is nearly empty. 2) Variations in the ingot pouring time due to the different ingot weights poured. Consequently, the use of the average pouring rate of a heat may not be exact, but in large-scale production it is not practical to treat ingots separately according to their pouring rates. The variations of ingot weights and sizes may be overcome by considering the rate of rise of steel in the mold. Hence, the average rate of filling of molds throughout the pour of a heat, inches per second, will be used in this note. Every ingot rolled at Inland is rated at the blooming mills prior to hot machine scarfing as being good, fair, or poor for cracks, scabs, and checking. The latter term refers to the network of breaks or lines associated with overheating or burning in the soaking pits. It is also known that thin-skinned steel is prone to show this defect if the subsurface blowholes are exposed during reheating or rolling. The experiences with the surface quality of slabs rolled from ingots poured at different rates are presented in Fig. 1. The data represent nearly 11,000 ingots. It appears that all three types of defects are in-

Jan 1, 1960

By Donald L. Katz

Charts for predicting the pressure to which natural gases may be expanded without hydrate formation have been prepared for gases of even gravity. Pressure-temperature curves for hydrate formation were established for gases having gravities from 0.6 to 1.0. These curves and the thermal behavior of the gases during free and adiabatic expansion were used to prepare the charts for estimating the permissible expansion of natural gases without hydrate formation. The problem was solved by L. F, Albright, W. T. Boyd, J. J. McKetta, G. Martin, P. Poettman. and A. P. Snyder.-, who are first-year graduate students in the department of Chemical and Metallurgical Engineering at the University of Michigan. This paper is essentially a summary of their results. Prediction of Conditions for Hydrate Formation in Natural Gases Each natural gas under a given pressure will form solid hydrates at a corresponding temperature provided sufficient water is present.1-5 The temperature of natural gases below about 5000 lb. per sq. in. decreases when the gases are expanded freely.6,7 This decrease in temperature may cause the expanding gas to enter the region of temperature and pressure at which hydrates will form' The final pressure to which a natural gas may 'be expanded without hydrate formation depends upon the initial temperature and pressure and the gas composition. This paper presents charts that give the final pressures to which gases of gravity 0.6 to 1.0 at given initial temperatures and pressures may be expanded without formation of hydrate. Hydrate-forming Temperatures and Pressures as a Function OF Gas -Gravity Experimental data of pressure versus temperature at which solid hydrate will form, provided sufficient water is present, are available for a series of gases.2,3 A method of predicting the pressure-temperature curve for a given gas composition has been reported.' The solution to this problem requires that these curves relating pressure to temperature be established for gases of given gravities.

Jan 1, 1945

By W. A. Selvig

BY plotting fixed carbon against British thermal units of coals free from mineral matter, and ranging in rank from anthracite to lignite, it is found that the coals of higher rank, from anthracite to the higher rank of the high-volatile bituminous coals, inclusive, can be separated into groups according to their degree of metamorphism by reference to their fixed carbon. Such charts show also that the coals lower in rank can be best separated into groups with respect to B.t.u., especially when plotted on the moist basis, that is, coal containing its natural bed moisture. A tentative scheme for coal classification was presented at the October, 1932, meeting of the Technical Committee on Scientific Classification, of the American Standards Association Sectional Com-mittee on Coal Classification. This scheme was sponsored by Sub-committee IV on Tentative Classification of Coals, under the chairmanship of W. T. Thom, Jr. It proposed the grouping of coals according to rank by reference to fixed carbon and B.t.u., on the basis of coal containing its natural bed moisture but free from mineral matter. This scheme proposed classifying coals into four broad classes: (1) anthracitic, (2) bituminous, (3) subbituminous, (4) lignitic.. The anthracitic class was divided into three groups designated as meta-anthracite, normal anthracite, and semianthracite. The bituminous class also was divided into three groups, low volatile, medium volatile, and high volatile. The high-volatile group was further subdivided into four subgroups according to moisture content, as follows: (1) less than 5 per cent, (2) 5 to 10 per cent, (3) 10 to 15 per cent, and (4) 15 per cent and more. The subbituminous class was divided into two groups, group, 1 including subbituminous coals having calorific values of 10,500 B.t.u. or more, and group 2 including those with less than 10,500 B.t.u. , The lignitic class of coal was divided into two groups both below 8,000.B.t.u., the one group consisting of consolidated and the other of unconsolidated

Jan 1, 1934