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By D. A. Lyon

Discussion of the paper of DORSEY A. LYON and ROBERT M. KEENEY, presented at the San Francisco meeting, September, 1915, and printed in Bulletin No. 104, August, 1915, pp. 1707 to 1730. LAWRENCE ADDICKS, Douglas, Ariz.-I think papers of this character, while general in, nature, are of particular value and interest, because when we figure on competing with the East in electrometallurgical industries, on account of the cheap power on the Pacific Coast, we have to take two or three things into account. In the first place, power very rarely amounts to more than 20 per cent. of the total cost of an operation, even .though it be electrometallurgical, and I think it is the common opinion among those who are not familiar with those particular industries, that it amounts to more than 50 or 60 per cent. Take copper refining; we may say that it is 15 per cent. of the total cost. In the second place, around New York City, with 100 per cent. load factor and a reasonably large load, say 10,000 kw., we can generate from a certain class of coal 1 kw.-hr. for about 0.3c. I might say, however, that 0.3c. does not include overhead charges, interest on the investment, etc. The third factor we have to consider out here is that any product to be salable, must command a retail market. It would be useless to produce wire bars here on the Pacific Coast because there is no place to roll them. If we were going to establish a copper refinery, that part of its output which goes into wire bars would have to be taken care of by building a rolling mill alongside of it to turn it into wire and finally make a product that is salable. I do not think, however, that Mr. Lyon need have excluded copper refining from his industries. There are perhaps 50,000,000 lb. of copper a month refined in this country on a custom basis. I think the smelting companies would be very glad to build refineries here if conditions warranted it. The recent extensions of the Great Falls refinery and of the Tacoma refinery in the last few months give evidence of that.

Jan 12, 1915

By Fred Wright

IN A recent paper1 a detailed discussion is given of the possibilities. of using polarized light in the examination of opaque substances. The factors underlying the problem .are there treated from the viewpoint of the electromagnetic theory of light and the presentation is necessarily mathematical in form. The practical methods resulting from the discussion are, however, relatively simple and promise to be of value in the determination of certain ores and metals when studied in reflected light under the microscope. The results of the theoretical investigation referred to may be summarized by stating that in general the optical constants, such as refractive indices and absorption indices, cannot be satisfactorily ascertained on small, random, polished sections; that the use of polarized light enables. the observer ordinarily to determine whether the crystal plate is isotropic or anisotropic, and also to ascertain the degree of anisotropism; that for this purpose methods based either on the contrast in intensity between the two reflected components of non-polarized light, or on the amount of rotation of the plane of polarization, on reflection, of vertically incident, plane-polarized light, may be employed; that methods based on the phase difference between the two reflected components are in general of little value because of the small differences in phase which ordinarily result for a relatively large change in birefringence or biabsorption. The measurement of the optical properties of transparent minerals, even in minute irregular grains, is a simple task with modern petrographic microscope methods and is accomplished by petrologists as part of their ordinary routine work. But the determination of the optical constants of opaque substances is difficult and is rarely attempted; all observations are necessarily made in reflected light and are restricted commonly to the determination of color, of hardness, of the character of crystallization, and

Jan 2, 1920

By August Wendel

It is a well-known fact to all Bessemer steel manufacturers using a blooming mill, that ingots show large cracks in the first few passes of the rolls, which, in the following ones, do not always roll up satisfactorily. This deficiency in the quality of the product is generally called "red-shortness," though, in the writer's opinion, mostly unjustly so. Different explanations for the said peculiarity are given by the leading authorities, each works selecting one element as a special scapegoat for the inferior quality of the ingot. The sulphur is generally first charged as being the principal cause of all mischief in this direction ; then, after ascertaining that sulphur is not higher than the average, and sometimes lower in the very worst heats, silicon has to bear its share of abuse. How and why silicon should affect the working qualities of the metal, the writer could never precisely learn, but is convinced that the doctrine of its pernicious influence is an established one with many. In cases where silicon failed to explain everything, resort was taken to calcium, aluminum, and some other known or unknown elements, without settling the difficulty; and lastly, when the skill of the chemist became exhausted, " practical men " came to the same conclusion, which many leading blast-furnace managers had arrived

By Frank Peterson

THE manufacture of gasoline by extraction or precipitation from the natural gases in which it is found, the present status of. the industry, its past development and future extensions; offer a subject which is so broad that to handle it in its entirety would require a voluminous paper. The writer will, therefore, attempt to concentrate the essential matter of the subject for a general presentation, giving some of the most interesting details of the factors that are important to the industry. This industry has drawn liberally on the principles of physics and chemistry, and, to a large extent, has had to adapt such information as is most useful-not from data recorded with reference to petroleum, but from data recorded with reference to general treatment of other materials. Because of the complex character of the petroleum series of hydro-carbons and the fact that data, such as solubilities, vapor pressures, etc., of the different petroleum compounds have not been determined, we are still working by rule of thumb in. some essential phases of the industry. Furthermore, the difficulties of determining such data are almost insurmountable. We have not one,, but two butanes to deal with-not one, but several, pentanes, hexanes, heptanes, and, as we ascend in the series the complexity and multiplication of isomers increases at such a rate as to make the task of isolating and studying their physical characteristics almost beyond the hope of possible attainment. The industry is the connecting link knitting the interests of oil producers and refiners into a much closer relationship than ever existed .prior to its inception and development. The relation between the producer and the refiner of petroleum prior to 1910 was. a rather antagonistic one in a commercial sense. It was to the interest of the producer of crude petroleum to sell it for a maximum consideration; the refiner's interest was to obtain the same product for a minimum consideration; therefore, each side of the business transaction retained within his own hands as far as possible the trade secrets of his business. Each side maintained an attitude of cold-blooded business sympathy only for the other. Cas-

Jan 12, 1917

By C. Richard Tinsley

INTRODUCTION Documentary complications arise from the risk apportionment in project financing which generally means that once the project is up and running and has satisfied the lender's completion test, the loan agreement specifically limits the lender's recourse to the project and its assets. It is the purpose of this paper to describe the special considerations which apply to industrial minerals projects and explore the reasons why so few project financings are negotiated in this industry. SIZE Small projects do not warrant the relatively high costs of negotiating and documenting project financing. The extent of the documentation is directly proportionate to either (a) the degree of risk apportionment, or (b) the amount of control given to lawyers to negotiate the documents. Although one would like to believe that project-finance documentation could be off-the-shelf, it is almost always necessary to tailor the documents to the mine development itself and the individual desires of the borrower. Accordingly, the documentation costs and initial expenses are seldom less than $40,000, and for complex projects can reach $400,000. In addition, banks often charge an up-front fee to partly compensate them for their staff time and partly to increase their yield on what is deemed to be a "riskier" loan asset. Another factor is the generally lower debt:equity ratio when bankers are uncertain of the accuracy of the cash flow projections. The ratio of the amount of cash flow left over after debt service to debt service itself is a key tool for project finance (debt service coverage). Bankers will require a higher coverage ratio for industrial minerals projects because of the relatively higher uncertainties in the following categories: Prices Markets Geology/Quality Transportation Environmental This, in turn, means that lower debt:equity ratios are the norm for new industrial minerals projects. INDUSTRY STRUCTURE It is hardly worthwhile to generalise about a field as diverse as industrial minerals, but there are four other structural reasons why project financing has not been widely applied. 1. The most obvious example is the predominance of small-sized operations, largely a function of transportation economics. Geological conditions also contribute to their dispersion. 2. Often, the product is only a small part of a company's business in contrast to many petroleum, metals, or coal companies whose sole business is the production of the raw material. The construction industry is a good example here for cement, gypsum, crushed stone, sand and gravel, and the drilling-mud services business for barite and bentonite. A company is unlikely to jeopardise its main business through the failure of a project financing on one of its key inputs. The corrollary is that the mined input is often regarded as a cost centre and not run on the sort of economic basis suitable for project financing. 3. There may be a reluctance to reveal key aspects of an industrial minerals venture to an outsider for purely competitive reasons. Unlike the other minerals industries which readily share technical information at plant visits and

Jan 1, 1985

By Herbert H. Uhlig

A STUDY of passivity in chromium-iron alloys holds considerable interest, both because of the present-day practical importance of the stainless steels, and because of the scientific importance attached to the mechanism of their corrosion resistance. Upon the discovery of the passive chromium-iron alloys in 1912, it seemed logical to attribute the observed phenomenal corrosion resistance to a thin, continuous, protective reaction product on the surface. The product was thought to be Cr2O3 or a similar oxide containing both chromium and iron. This mechanism seemed likely in view of Michael Faraday's conjecture that passive iron is not reactive in concentrated nitric acid because of an oxide on the metal surface.† Since 1912, data have accumulated that permit a further exploration into the nature of passivity and provide a new approach to the problem. A summary of the facts lends considerable weight to a mechanism based not on physical protection of an oxide or similar compound, although such compounds may be present on the surface, but to a change in tendency of surface metal atoms to react chemically. This change in reaction tendency is ascribed to chemisorbed films that effectively satisfy residual valence forces of the metal surface, but do not appreciably disturb the positions of metal atoms in the lattice. In other words, formation of a new lattice such as that of an oxide is not a necessary condition for this type of passivity. The decreased reaction tendency of the metal by reason of chemisorbed films can thereby account for low reaction rates of the stainless steels in many media, as well as a noble galvanic potential as is observed. Substances capable of adsorbing on the stainless steels, and hence accompanying the property of passivity, are typically oxygen, nitrites or chromates, but are not in any sense limited to these. Other elements and compounds can also chemisorb, and therefore may also play a major part in the mechanism of passivity in specific media. The mechanism of passivity based on chemisorption or activated adsorption begins with the interpretation Langmuir proposed for his experiments concerning adsorbed oxygen on tungsten.1 He found that adsorbed oxygen was tightly bound, remaining on the tungsten surface above temperatures at which WO3 rapidly volatilizes. The oxygen in such a state did not readily react with hydrogen even at

Jan 1, 1947

By William P. Blake

The occurrence of enormous masses of pure copper has given the mining district of Lake Superior worldwide reputation. The first masses brought from there excited great attention, and directed the notice of the mining world to the few particular mines from which they were taken. It may not now be generally known that nearly all the veins which are worked, and which cut across the trap ridge, contain mass copper, and that large masses are continually being raised from them. The largest continuous mass which has been taken out was probably that from the Minnesota, in 1857, which is variously stated as weighing 420 tons and 470 tons. Its length was about 45 feet, its breadth or height 22 feet, and its greatest thickness 8 feet. All such masses are very irregular and ragged in their form and thickness, thinning out generally from a foot to a few inches, and straggling through the vein until they connect with other large masses. This was the character of a mass found in the Phœnix Mine, one of the oldest on the lake, which mass altogether weighed some 600 tons. But this was really a series of masses more or less connected by strings of metal, yet no one large part of it weighed, singly, over 200 tons. A similar series of masses, weighing about 600 tons, was extracted from the Miunesota. Some of the Phœnix masses were four to five feet thick of solid copper. The Cliff Mine has yielded masses weighing from 100 to 150 tons in one piece. One of 40 tons was taken out this year, besides numerous blocks weighing from 1 to 8 tons. This mine and the Central are now yielding mass copper in abundance. It is, bf course, impossible to pick, or drill, or to break out such huge masses of solid metal when they are found, by drifting upon the course of the vein. The method of extraction is as follows: The miner picks out or excavates a narrow passage or chamber upon one side of the mass, laying it bare as far as possible over its whole surface. It is usually firmly held by its close union with the veinstuff, or by its irregular projections above, below, and at the end. If it cannot then be dislodged by levers, the excavation of a chamber is commenced behind the mass, and this excavation is made large enough to receive from 5 to 20 or more kegs of powder. In one

By Austin Park

More metal at a lower profit continued to be demanded from the mining industry during 1969. Correspondence with U.S. and Canadian mining districts and a study of the mining literature indicate that, a large majority of the mines are keeping pace and rising to the challenge. Continued research and better understanding of pneumatically applied concrete for roof and wall support was of top interest. Many mines are changing mining methods for the adaptation of load-haul-dump units. The most recent adaptation being the use of these units in cut- and-fill stoping and in various types of development headings. Boring methods and use of two- or three- boom drilling jumbos mounted on rubber tires for versatility continues to be the favorite approach to the demand for rapid excavation.

Jan 1, 1970

By A. L. Simpson, J. M. Edwards

The application of the Scintillometer to radioactivrty surveys in boreholes of oil wells has made it possible to determine bed thickness with a high degree of accuracy. This fact, combined with known relation of logging variables, makes thin bed porosity determination practical. With the use of the Scintillometer a method hot been derived whereby the apparent level of radiactivity, as recorded on radiation logs, may be converted to the true level. The true level of radioactivity is that level to which the recording pen would have traveled had the detector remained at a given depth for on infinitely long period of time. This factor is: radioactivity level, Ra, is the apparent radioactivity level, T is the bed thickness, D is drag, and L is the length of the detecting system. This method depends entirely on accurate measurements of bed thickness and drag. A thorough discussion of the concept of time constant and logging speed as related to drag is undertaken. INTRODUCTION Neutron curve interpretation has become one of the accepted methods for porosity determination in oil field practices. A great deal of literature has been published about neutron derived porosities, but this has been concerned with thick beds, or possibly even averaging of a series of thin beds as a single unit. There has been a lack of written information on methods whereby porosity can be evaluated for beds less than 10 ft in thickness. In certain areas, production is derived from relatively thin formations. The importance of thin bed evaluation, the fact that the Scintillometer is an adequate tool for this application, and the general lack of published information concerning neutron porosity for thin beds are the fundamental reasons for presenting this method of porosity determination. This concept is not put forth with the idea of discounting existing methods, but is merely suggested as a modification of other accepted methods of porosity determination which makes no allowance for quantitative evaluation of thin beds. The effects on the neutron log of counting statistics, statistical variation in the porosity of earth materials, and hole size must be taken into account to obtain neutron derived porosities. Since these effects have been described in past literature, the authors have not made an attempt to go into the subject in detail. With the use of statistical and repeated sections on the log, it may be determined which responses on the log actually correspond with lithologic changes. EFFECT OF DRAG AND ITS RELATIONSHIP TO TIME CONSTANT AND LOGGING SPEED Before entering into a discussion of porosity determination of thin beds, there should be a thorough

Jan 1, 1956

By J. G. Paterson, J. A. Meech

Abstract-Activated carbon is a strong adsorbent for amyl xanthate, capable of removing from solution up to a quarter of its own weight in xanthate. In selective flotation systems where depression is unstable, separation efficiency increases with activated carbon additions. The improvements observed are brought about by two mechanisms. First, by removing stripped and residual collector ions from solution, competition between depressant and xanthate is reduced and depression is stabilized. In addition, the texture of the froth phase at high pine oil concentrations is modified by activated carbon such that better drainage between the air bubbles takes place, alleviating the mechanical entrapment of depressed mineral particles. In treating a bulk copper/lead concentrate produced from GECO ore, selectively between galena and chalcopyrite is increased when activated carbon is used. Although the rate of flotation of galena is marginally lowered by activated carbon, a small extension in the duration of flotation allows the lead recovery to increase by 19% at the same recovery of copper. An addition rate of 0.75 kg/ton (1.5 lb/st) of bulk concentrate is suggested as optimum from this testwork. However, the actual level wed in the mill is dependent upon the residual concentrations of collector and frother in the bulk concentrate Pulp.

Jan 11, 1978

Plans have been completed with only details to be arranged for the first Metals Branch Conference in the Northwest. The two day meeting will be held jointly with the Industrial Minerals Div. on Friday and Saturday, May 9 and 10, 1952, at the Davenport Hotel in Spokane, Wash. For, some time the metals activities in this area have been neglected. Expansion of metal producing and fabricating industries in Washington and neighboring states has brought sufficient interest to insure the success of such a meeting. A committee has been hard at work for several months. Nonferrous extractive metallurgy men will find an extensive program in the April issue of JOURNAL OF METALS. Sessions for iron and steel producers, physical metallurgists, and educators will make the Metals Branch picture complete. Metals Branch members residing in Washington, British Columbia, Oregon, Idaho, Montana, Wyoming, Nevada, and Utah, or who can be in the Northwest at this time should make plans now to attend. A Metals Branch luncheon is planned for Friday and a dinner jointly with the Industrial Minerals Div. is planned for Saturday according to F. R. Morral, metallurgist with the metallurgical research div. of Kaiser Aluminum & Chemical Corp., P. O. Box 1451, Spokane, Wash.

Jan 1, 1952

By R. E. Sinke

Demerara Bauxite Co. in British Guiana has come a long way in tackling the problem of stripping and removing overburden. When the company started mining in 1917, overburden was hand-loaded into carts pulled by donkeys. Since then it has been recognized that overburden removal is one of the greatest problems. Over the past years a great quantity of equipment has been purchased, discarded as it became obsolete, and replaced with better and cheaper tools. The policy has kept the company's overburden removal costs within reason. Accurate records of costs per cubic yard and cubic yards per hour per unit have been kept for many kinds of equipment. Walking draglines and hydraulicking equipment are the key approaches to the current operation, but shovels, tractor-drawn wagons, self-propelled rubber tired scrapers, and tractor-scrapers still have limited applications. Mackenzie, operational headquarters of the Demerara Bauxite Co. Ltd., is on the Demerara River, 65 miles from Georgetown, British Guiana. Ore treatment and ship loading facilities are at Mackenzie, head of navigation for ocean-going vessels and the mines are located 7 to 40 miles farther upstream.

Jan 4, 1955

As a means of lending weight to the activities of its Committee on Industrial Organization, with particular reference to the work on mental hygiene and the prevention of illness, the Institute has recently invited a number of members of the medical profession to become Associates of the Institute. We are glad to observe that the wisdom and utility of this departure have been appreciated by the gold mining industry, in testimony whereof we are pleased to publish the accompanying sketch from the pen of Mr. P. A. Robins, Managing Director of the Hollinger

Jan 8, 1918

By Thomas T. Read

MINING, which is at least twenty centuries old, was at first, and long, wholly a practical art. Little more than two centuries have elapsed since the inception of the idea that general education and a knowledge of natural science would be of advantage to those engaged in the mining industry. Though schools of mining began to develop in Europe early in the eighteenth century the concept of educational preparation for technical conduct of the industry was slow in winning general acceptance in the industry itself. John Hays Hammond, in his autobiography,1 recalls that when he sought employment with a mining company after he had graduated from Yale and Freiberg he had to assure its executive, before being even considered for employment, that he did not consider that he had learned anything about mining. This was as late as 1880. Existence in the industry of a prejudice against education of the academic type is perhaps an explanation why inadequate provision has been made by the mining industry for the continuing education of technical employees after they enter employment, although engineering education prior to engaging in industry has now won general acceptance. I am familiar with the existence of "loop" courses for engineering graduates in metallurgical plants, of schemes for giving mining graduates "practical experience," and of the interest in vocational courses for workmen which sprang up in the period of labor shortage during and immediately following World War I (but which quickly died when the depression of 1921 again made experienced workmen available in sufficient supply), having been chairman of a committee appointed by the Mineral Industry Education Division to make a survey of existing provisions for post-employment training for engineers in our industry. The results of that survey, reported elsewhere, clearly indicate that it is inadequate as to amount; the aim of this paper is to present evidence for belief that it is also inadequate in quality. To avoid becoming too involved, no reference will be made here to post-employment vocational training for workmen, which is a subject differing so much from post-employment education for engineers as to require separate treatment. Neither will postgraduate education for metallurgical engineers be discussed, because a distinction must then be made between training for research work and for plant operation, whereas mining engineers engage almost exclusively in operations. Since the situation in the coal-mining industry has been discussed at several recent meetings, that also will be passed over, and what follows should be taken as a discussion applying exclusively to the metal-mining industry. PROFESSIONAL DEVELOPMENT In the operations field (both in mining and metallurgy) the work to which a beginner is assigned is seldom closely related to previous academic education. The contrast is almost as great as between

Jan 1, 1941

POSITIONS VACANT (Under this heading will he published notes sent to the Secretary of the Institute by members or other persons.) In the course of the next few months, a mechanical engineer, who has specialized in the design and erection of copper-smelting plants, including steel work, power equipment, etc., may be required by a company operating abroad. Man speaking German preferred. No. 23. ENGINEERS AVAILABLE (Under this heading will he published notes sent to the Secretary of the Institute by members or other persons introduced by members.) Member, 31 years of age, married, graduate of Massachusetts Institute of Technology, desires position with malleable iron or steel firm. Nine years' experience as chemist and metallurgist in malleable, gray iron, and steel. No. 123. Member, metallurgist, desires position with company making steel, castings, or tool steel. Has had six years' experience with the electric furnace, making steel castings and tool steel, also heat treatment of same. No. 124.

Jan 9, 1914

By R. C. Palmer

THE testing of flotation oils has occupied a large part of the time of the testing departments of various companies using the flotation process in the beneficiation of their ores. The great differences in ores and iii oils has made such work necessary as it has not been possible to select the oil best suited for the purpose without trial of many kinds. In fact, individual shipments of flotation oils from the same manufacturer will often differ so radically that the mill men have been forced to test every lot of flotation oil before its use in the mills. Further, although almost every imaginable product of the distillation of wood, from alcohol to pitch, has been tested in a more or less perfunctory manner by various people, few companies have allowed the results of their tests to be made public. This work was undertaken for the purpose of obtaining reliable data regarding the value as flotation agents of a number of products that are obtained from the distillation of wood by different methods, and incidentally to determine whether some of the products not used at present could be used. Large quantities of such materials are being wasted or burned in the wood-distillation plants of the United States, and if some use other than fuel could be found for these materials, such a use would represent a distinct saving to the country as a whole, would increase the profit of wood-distilling plants now operating and perhaps make it possible for others to operate which at present cannot do so except at a loss. At the same time it was thought that if such products can be used as flotation agents, then their use would serve to increase the number of oils and other products available for flotation purposes. It was also hoped that it might be possible to discover a substitute for some of the most effective but comparatively high-priced oils which are now used for flotation

Jan 8, 1916

By John E. Miller

Unit Rig & Equipment Co., manufacturer of Lectra Haul trucks, is continually studying methods of reducing the operating costs of large haulage trucks. Reduction of haulage system operating costs is an important goal that equipment operators and equipment manufacturers constantly try to improve on. One of the most variable and important factors affecting operating costs is actual truck operating practices. An examination was centered on methods to optimize truck utilization. It was found that a very effective method of accomplishing this goal would be an automatic truck control (ATC) system to automatically control a fleet of haulage trucks in a predetermined pattern. Economic studies were conducted which showed a very favorable reduction in mine operating costs by use of an ATC system. In 1970, Unit Rig & Equipment Co., in conjunction with SAAB-SCANIA began preliminary development of adapting, for truck use, a proven automated control system, previously used for train systems, small trucks, and military target vehicles. In 1974, the first prototype system was installed on a Lectra Haul M-100 and tested extensively at Unit Rig's test track in Tulsa, OK. This truck and system were then displayed publicly at the 1974 convention in Las Vegas. In 1976, the system was redesigned for production to maximize reliability, ease maintenance, and to accommodate future control and-status reporting developments proposed for haulage trucks. The new design equipment was manufactured, and a full system test will be conducted in an actual open-pit mine for an extended period to evaluate reliability, compile economic data, and obtain application information to evaluate complete mine haulage system conversions to ATC. System Description The ATC system is designed to provide automatic control of all the vehicle functions normally accomplished by the vehicle operator. The basic system consists of the on-board control equipment and the wayside control equipment. The on-board equipment receives commands from the wayside equipment and controls all the truck functions. In addition, on-board sensors monitor all critical truck functions and provide instructions to the truck and system to assure safe operation. The wayside equipment consists of a buried guidewire, block control units and a central controller which provides predetermined signals to the on-board equipment for speed control, steering, and for auxiliary functions (dumping, horn, etc.) through the guidewire located in the truck's path. The wayside equipment also controls vehicle separation, system status, and provides truck location to a central display panel. The central control panel can vary the speed level signals over any segment and can also command an emergency stop to halt all the units. [Fig. 1] illustrates a typical ATC installation. If ATC is used in operations which require flexibility and mobility at the end of the ATC guidance network, the trucks can then be operated by either radio remote control or manually to complete their assigned functions.

Jan 1, 1982

By Harry Perry

In the United States the state mining laws enacted in the late 1800s were the first laws to recognize that an employer had a responsibility to provide the employee a place to work that met at least some minimum safety standards. The coal mining industry was also the first major industry in the United States to be regulated in 1952 by federal safety laws, although federal inspectors had the right-of-entry as early as 1941. Within recent years, however, the Congress has enacted a number of federal safety regulations for a variety of industries, such as the Aviation Act (1958), National Traffic and Motor Vehicle Act (1966), National Gas Pipeline Act (1968), and Radiation Control for Health and Safety Act (1968). The fatality and injury experiences of the mining industry in the United States, while at a significantly higher rate than for industry as a whole, showed a continuous improvement until the last decade or two-at which time the rate leveled off. Although fatality and injury rates in foreign countries have been generally lower than in the United States, further improvement in those countries also has been difficult to achieve in recent years. It appears, therefore, that some major change in mining laws, combined with a radical improvement in mining technology and a more effective labor-management safety program, will be needed if further reductions are to be achieved in fatality and injury rates. At the same time, there is a growing awareness by society that an employee's place of work, where he spends nearly half of his waking hours, should be made as safe as possible. As increased consideration is given to means for achieving greater safety in all industrial situations, it is becoming apparent that more is required than merely providing physical safeguards on tools and machines. Rigorous, strictly enforced safety standards are useful, but more important is the desire of labor and management to make certain that industrial accidents are prevented. The pressure to achieve increased productivity, and thus receive higher wages, can be a significant deterrent to safe working practices. The temptation can be great to "take a chance" or "cut a corner" in order to speed up production. Public concern over all types of industrial safety in the United States was reflected by the introduction of a number of general occupational health and safety bills in Congress for the first time in 1968. While no legislation resulted, the hearings revealed that, although there were differences in how standards should be set and who should administer them, there was agreement on the need for adequate laws. Since the mining industry has been subject to safety standards longer than other industries, it is not surprising that advanced safety concepts for mining are being explored by the industry and the enforcing agencies. More complete and sophisticated accident reporting is being planned that will reveal the

Jan 1, 1976

By A. H. Geisler, J. H. Keeler

Preferred orientations in unalloyed zirconium were determined by the Geiger-counter spectrometer X-ray diffraction technique. With increasing P-annealing temperature the following textures were obtained: l—a retained a-annealing texture, 2—additional orientations predictable from the a-p (Burgers) relationship, and 3—a texture derived from a cube texture in the p phase. Earlier work on cold-worked and a-annealed zirconium was reappraised to show a quantitative dependence of rotations on temperature and to identify spurious areas of some of the pole figures. IN a previous paper,' the preferred orientations of high purity zirconium sheet were described for cold-rolled and annealed samples. Annealing temperatures up to 900°C, which is slightly above the allotropic transformation temperature, were explored. Of interest was the observation that the orientation of the hexagonal-close-packed material after annealing in the temperature range of the stable body-centered-cubic phase was similar to that of the material which had been annealed in the a temperature region, although a change in texture would be expected because of the many new orientations based on an orientation relationship between the two forms of zirconium. The reversion to an original orientation after an allotropic transformation cycle is not unusual. It has been found for titanium,"* for thallium," and for cobaltB among the hexagonal metals. Burgers found in his original work7 that, when zirconium was cooled through the allotropic transformation and then reheated, the body-centered-cubic phase reverted to the original orientation. Additional experimental work has been carried out to further explore the textures of zirconium after annealing in the temperature range above the allotropic transformation. In addition, a reappraisal was made of the earlier results for zirconium' in light of recent work on titanium4 which has shown that the texture type depends quantitatively on the temperature of annealing and that spurious areas may be encountered in the pole figures of hexagonal metals determined by the X-ray spectrogoniometer technique of analysis. Experimental Procedure Crystal-bar zirconium prepared by the iodide process was the material used in this investigation. The major impurity was hafnium which was less than 0.3 pct. The composition obtained by spectro-graphic analysis is given in Table I. Cold-rolled specimens were prepared from crystal bar by a series of reductions of approximately 0.010 in. until the sheet reached a thickness of 0.010 in., after which it was cold rolled to 0.001 in. thickness between sheets of alloy steel. The total cold reduction amounted to about 99.8 pct. Specimens were annealed for % hr at 1000" to 1100" to 1200°C or 1 hr at 1400°C in an evacuated Vycor or quartz tube. The transmission pole figures were obtained by

Jan 1, 1956

By David E. Van Dillen

INTRODUCTION Current design practices for deep tunnels make extensive use of plasticity solutions by Newmark (1970) and Hendron and Aiyer (1971). These solutions are applicable to a circular tunnel subjected to a hydrostatic stress state in a Mohr-Coulomb plastic medium. The role of rockbolts is introduced into these solutions as a uniform internal pressure equivalent to the yield stress of the rockbolt pattern. The application of these solutions is hampered by their inability to consider the biaxial nature of the in-situ stress field or any surcharged stress, such as due to blast loading. As a means of considering the biaxial stress field, designers have turned to relatively costly alternatives, such as the finite element method. The recent work of Detournay (1983) simultaneously provided two generalizations to the state of the art of the analysis of circular tunnels. Whereas the solution of Newmark applies to nondilatant Mohr-Coulomb materials, and that of Hendron and Aiyer applies to materials having associated flow rules, the solution of Detournay covers materials of arbitrary dilatancy. Secondly, Detournay's solution is valid for biaxial stress states, as long as the problem remains statically determinate (St. John, Detournay, and Fairhurst, 1984). The topic of this paper is an investigation of various alternatives for introducing the effects of rockbolts into simple tunnel design charts developed using Detournay's solution. The study was conducted using the BMINES finite element code, into which rockbolt elements have been added (St. John and Van Dillen, 1983). These rockbolt elements allow for plastic deformation of the bolt, bolt

Jan 1, 1984