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By H. Biloni

PORE formation during solidification has recently been studied theoretically by Piwonka and Flemings.1 For the ordinary conditions of cellular solidification, these authors state that there is a difficulty in explaining the formation of pores. The difficulty arises because the conditions necessary for pore formation are not those obtained during cellular growth. Therefore Piwonka and Flemings1 had to examine various unusual possibilities in order to explain the apparent presence of pores in a cellular substructure of aluminum, taken from Doherty.2 For aluminum, Doherty and Davis3 have developed a pitting technique to reveal substructure, which depends upon the condensation of vacancies from supersaturated solution after quenching. This technique as further developed4 was used to study solidification substructures. In the case of striations, delineation of the substructure is produced by the absence of surface pitting after quenching: in the vicinity of the striations the dislocations which constitute this substructure are sinks for vacancies. In the case of the cellular substructure the experimentally observed effect is the same. However, in this latter case Doherty and Davis4 suggested that micropores associated with the cellular substructure were the agent responsible for providing sinks for vacancies. This interpretation seemed necessary for the cellular substructure because no misorientation arising from a dislocation array could be observed. It is noted especially that Fig. 1 presented by Piwonka and Flemings1 and Fig. 5 by Doherty and Davis,4 as

Jan 1, 1968

By W. G. Moffatt, J. Wulff

BRAZED joints and their strength have for some time been of great practical as well as theoretical interest. A good summary of the previous work in this field may be found in the reports of the Armour Research Foundation. In spite of excessive scatter in test data, the fact that the strength of a brazed joint may exceed the ultimate strength of the brazing material itself by many times continues to be of interest and of value in engineering. That this is qualitatively due to plastic constraint of the brazing material by the faying surfaces of the base metal is not in dispute, yet no complete interpretation of the data exists. The purpose of the present work is not to provide such a new interpretation, but to report new experimental data which we hope may lead to a better understanding of the important variables concerned. The work of Bredz' definitely shows that the thinner a brazed joint is, the greater is its strength. Dianeter of a joint has seldom been taken into

Jan 1, 1958

By Eugene A. Stephenson

Critical analyses of the work expended in producing oil by the utilization of gas energy have appeared in the publications of Shaw,' Pierce and LewisI2 and Herold,3 authors who have ably discussed the factors which must be taken into consideration in comparing energy consumed per barrel in various wells which are flowed by means of gas-lift. However, two distinct phases of oil production are concerned with the ratio of gas energy consumed to oil produced. One of these phases is the gas-lift, which utilizes the differential gas pressures for the purpose of flowing oil, whether these pressures be natural reservoir pressures or be induced by artificial compression of gas or air. The other phase has to do with prorating oil production in pools which are operated either as units, or are subject to such restrictions as those imposed at Oklahoma City by the Corporation Commission, or by similar controlling groups in other fields. An abundance of literature is available relative to the problems of flowing wells by gas-lift, but the first suggestion that the energy of the gas within the oil and gas pool might serve as a basis for proration, appeared in the timely article by Mc Williams.4 Much of the dissatisfaction with proration in certain fields arises because some operators feel that besides the hazard to the wells which accompanies the test, the method of allocating production on the basis of the " potential" gage is inequitable and gives some operators a distinct advantage over others.5 The most severe penalty may be exacted from the most progressive operators or those who attempt to produce their oil with a minimum quantity of reservoir gas. If no difficulties ever developed in drilling, shutting off water, or in well completion, it might

Jan 1, 1931

By C. M. Signer, W. P. Hewitt

THIS is a story of a mine discovered in the days of the Conquistadores but that remained unimportant until the second decade of this century. Without the usual legendary history of romance and fabulous riches it has become famous for the development of unexpected metals and unusual problems. These developments and experiences, exciting and interesting as any legend, are the substance of the San Antonio mine of the Santa Eulalia district in northern Mexico. Originally opened for its silver-lead content, it developed a tin deposit of singular economic importance and unique geologic interest, a vanadium orebody that for a few years placed it among the leading vanadium producers of the world, and now lead and zinc sulphide ores. It has been the seem of a disastrous flood that brought deep-sea divers into Mexico's desert mountains and raised important problems regarding ground water, demanding unusual measures. Geology and operating questions relating to the above matters will be discussed and much of it is recent history which has become a part of Mexican mining lore. History Dates Back to 1325 Santa Eulalia is the oldest of American cities, founded in 1325 by the Aztecs under the name of Tenochtitlan and devastated in 1521 by Cortes and his rapacious band of iron-willed adventurers. Their lust for gold burned through the Aztec empire and onward into most of North America. Santa Eulalia was in the path of conquest. In 1591 the district's first ore discovery was made near what is now the San Antonio mine. The ores carried no gold and the silver-lead content was unattractive to the early pioneers. Not until 1700 was real mining activity undertaken.

Jan 1, 1952

By D. R. Mitchell

This paper discusses some of the fundamental physical and chemical characteristics of coal in Illinois that affect its preparation for the market. At the present time preparation consists almost entirely of sizing and hand-picking. The washing of coal has almost entirely disappeared from the state. This is a rather startling fact when one considers that in the year 1908 Illinois outranked all other states in the quantity of coal washed and a few years later, in 1912, 85 washing plants were reported. Two reasons are apparent for this change. One, which is probably the most important, is that immense areas of comparatively clean coal were opened; the other is that many of the early washing plants were inefficient, so that washed coal was looked upon with disfavor in many trade centers. Objectives of Operators Some of the outstanding preparation aims being given due consideration by operating men are: 1. The greatest possible production of lump and domestic sizes which bring in the market at least $1 per ton more than the fine sizes or screenings. 2. Efficient screen sizing with as little breakage as is consistent with economical operation. 3. The removal of extraneous ash and sulfur. 4. Utilization of low-priced screenings. 5. Suppression of dust in domestic coal shipments. Preparation Underground To get the greatest possible production of the larger sizes, preparation must start at the face. Improvements in blasting and loading have increased the sizes larger than 2 in. by as much as 20 per cent. at some mines. Tiffany and McKitterickl report the results of an investigation they made at a mine in southern Illinois in which, by a carefully controlled

Jan 1, 1931

By Norman F. Schulz, Emert W. Lindroos, Strathmore R. B. Cooke

DURING the course of an investigation of the effects of various starch products on hematite and quartz in regard to their separation by flotation, it was found that whereas most starches flocculated suspensions of hematite in water, they did not flocculate similar suspensions of quartz. However, a derivative of whole corn starch containing approximately one tenth aminoethyl group (-—CH,CH2NH2) per glucose unit proved to be an exception. This aminoethyl starch was a very good flocculant for both hematite and quartz, and also possessed the property of depressing both minerals in cationic flotation tests. In view of the widespread use of starch as a flocculating agent of solids in tailing water, pulps, and for coal slimes, ore and various other purposes in sulphide and nonsulphide flotation, attention is called to the effective surface activity of aminoethyl starch in flocculating suspensions of the two minerals investigated. Test Materials The starch products employed included Globe Pearl starch No. 144 and fresh aminoethyl starch, both supplied by the Corn Products Refining Co. Dr. A. L. Elder" has kindly furnished a description The minerals used in the various tests are listed in Table I. Their specific surfaces were determined by the air permeability method, which gave results reproducible to within plus or minus 3 pct. Surface areas obtained by krypton adsorption were greater than the air permeability values by a factor of 2.0 for quartz and 62.4 for hematite. Starch Adsorption on Mineral Surfaces Starch adsorption data were obtained by agitating for 1 hr measured volumes of neutral starch solutions of known concentrations with weighed quantities of finely divided mineral of measured specific surface. The mineral then was separated from the pulp liquor by centrifugation and the residual starch content determined by chemical analysis. The analytical procedure consisted of oxidizing the starch with an excess of dichromate in acid medium at elevated temperature and titrating the excess dichromate by the ferrous ammonium sulphate—potassium permanganate method. Analytical results were reproducible to within less than 1 pct. Adsorption data obtained in unbuffered solutions near the neutral point are plotted in Fig. 1. The adsorption on either mineral was far greater for the aminoethyl starch than for the Pearl starch. Flocculation The degree of flocculation was determined for a given pulp by measuring the time required for the supernatant liquid to reach a certain degree of clarity. This was accomplished by passing a standard light beam through the pulp, contained in a glass settling tube, and measuring the time required after agitation ceased for the intensity of the transmitted beam to reach a predetermined value. Starch reagent was added to each pulp in small uniform increments, and the settling time was determined after each such addition. Increase in pulp liquor volume due to the added starch reagent was ignored in these tests. Pulps were maintained at or near neutrality. of the preparation of the aminoethyl starch: "Three hundred and sixty grams of powdered unmodified corn starch was slurried in 3 liters of water and stirred during gelatinization. Eighty-six grams of ethylenimine was added slowly during reflux which was continued for 4 hr. The yellow solution set to a gel upon cooling. This was broken up and neutralized with HC1. The thick paste was dried on hot rolls. Adsorbed polyethylenimine and salts were removed from the yellowish products by washing first with acidified aqueous '60 per cent' alcohol. The white product contained nitrogen corresponding to about one aminoethoxy group per ten glucose residues." Only laboratory samples of this starch derivative have been prepared. The starch reagents for use in flocculation, flotation, and adsorption tests were made up by dispersing the appropriate quantities of air-dry starch in cold water, adding boiling water, and heating for 30 min at 120°C under pressure. When used ip adsorption tests, the starch solutions first were cleared of insoluble matter by centrifugation.

Jan 1, 1953

By Strathmore R. B. Cooke, Emert W. Lindroos, Norman F. Schulz

DURING the course of an investigation of the effects of various starch products on hematite and quartz in regard to their separation by flotation, it was found that whereas most starches flocculated suspensions of hematite in water, they did not flocculate similar suspensions of quartz. However, a derivative of whole corn starch containing approximately one tenth aminoethyl group (-—CH,CH2NH2) per glucose unit proved to be an exception. This aminoethyl starch was a very good flocculant for both hematite and quartz, and also possessed the property of depressing both minerals in cationic flotation tests. In view of the widespread use of starch as a flocculating agent of solids in tailing water, pulps, and for coal slimes, ore and various other purposes in sulphide and nonsulphide flotation, attention is called to the effective surface activity of aminoethyl starch in flocculating suspensions of the two minerals investigated. Test Materials The starch products employed included Globe Pearl starch No. 144 and fresh aminoethyl starch, both supplied by the Corn Products Refining Co. Dr. A. L. Elder" has kindly furnished a description The minerals used in the various tests are listed in Table I. Their specific surfaces were determined by the air permeability method, which gave results reproducible to within plus or minus 3 pct. Surface areas obtained by krypton adsorption were greater than the air permeability values by a factor of 2.0 for quartz and 62.4 for hematite. Starch Adsorption on Mineral Surfaces Starch adsorption data were obtained by agitating for 1 hr measured volumes of neutral starch solutions of known concentrations with weighed quantities of finely divided mineral of measured specific surface. The mineral then was separated from the pulp liquor by centrifugation and the residual starch content determined by chemical analysis. The analytical procedure consisted of oxidizing the starch with an excess of dichromate in acid medium at elevated temperature and titrating the excess dichromate by the ferrous ammonium sulphate—potassium permanganate method. Analytical results were reproducible to within less than 1 pct. Adsorption data obtained in unbuffered solutions near the neutral point are plotted in Fig. 1. The adsorption on either mineral was far greater for the aminoethyl starch than for the Pearl starch. Flocculation The degree of flocculation was determined for a given pulp by measuring the time required for the supernatant liquid to reach a certain degree of clarity. This was accomplished by passing a standard light beam through the pulp, contained in a glass settling tube, and measuring the time required after agitation ceased for the intensity of the transmitted beam to reach a predetermined value. Starch reagent was added to each pulp in small uniform increments, and the settling time was determined after each such addition. Increase in pulp liquor volume due to the added starch reagent was ignored in these tests. Pulps were maintained at or near neutrality. of the preparation of the aminoethyl starch: "Three hundred and sixty grams of powdered unmodified corn starch was slurried in 3 liters of water and stirred during gelatinization. Eighty-six grams of ethylenimine was added slowly during reflux which was continued for 4 hr. The yellow solution set to a gel upon cooling. This was broken up and neutralized with HC1. The thick paste was dried on hot rolls. Adsorbed polyethylenimine and salts were removed from the yellowish products by washing first with acidified aqueous '60 per cent' alcohol. The white product contained nitrogen corresponding to about one aminoethoxy group per ten glucose residues." Only laboratory samples of this starch derivative have been prepared. The starch reagents for use in flocculation, flotation, and adsorption tests were made up by dispersing the appropriate quantities of air-dry starch in cold water, adding boiling water, and heating for 30 min at 120°C under pressure. When used ip adsorption tests, the starch solutions first were cleared of insoluble matter by centrifugation.

Jan 1, 1953

By Fred C. Bond

SIX years have passed since the last grindability table was published.1 In that time the list has been increased with many new tests, and the development of the new Third Theory of Comminution2 has made possible the reduction of all results to a consistent work index value. In this tabulation all grindability and crushability test results are given in terms of the work index, with formulas for reversion to the older units if desired. The average values for 57 different classes of materials are listed in Table I. The total number of work index values listed is 1211, and the overall average work index is 14.42.

Jan 3, 1953

By Edward Keller

Under the title, Labor-Saving Appliances in the Works-Laboratory, I published a paper1 in which mas described how multi-manipulations in a works-laboratory and in the furnace-room of an assay-laboratory, can be condensed into single manipulations by applying the proper mechanical devices. For example, I now deposit ill, or withdraw from, a muffle a set of 48 cupels as one unit. The front row (8) of these are blanks or heaters; the other 40, when they have attained the proper temperature in the muffle, are charged simultaneously with the 40 lead-buttons. Three manipulations here accomplish an operation which by the generally customary method requires 136, and this number is only limited by the size of muffle and cnpels. This operation is an enlargement of what I have already described in my former paper, and Fig. 1 shows the improved implements. In the paper referred to I described a gold-silver bead parting-bath, which is the last of the devices used in regular sequence in practice. This bath mas designated as being convenient, but mas not a labor-saver properly. Fig. 2 of the present paper shows a new device. Instead of the original tray, there are now sectional holders for the test-tubes, each having a wooden handle on either end, so that the holders ma?-be removed from the boiling bath, and the acid or water poured oE from each set of tubes (in this case, 7) without waiting to cool. The tubes, held in place by clutches, as shown in Pig. 3, rest in holes in the base-strip, having a smaller diameter than the tubes. Each holder is stamped at either end with a number, so that the bath becomes further useful by permitting several men to use it at the same time without interference. Apart from the handles, the holders are made of sheet-copper.

Jan 1, 1911

By C. E. Meissner

The need for a practical method of deciding upon new alloy steel analyses to widen its markets was the problem facing the Chrome Steel Works at the beginning of 1927. In addition to determining the physical properties of the alloys under consideration, it was necessary to test their value in service. Small melts of steel in a crucible, from which test specimens could be made, were insufficient to determine more than physical properties, therefore actual castings and ingots had to be made before the products could be placed in service. Furthermore, to save further experimental work, it was desirable that these heats should be made on a "pilot" basis; that is, actually duplicating regular open-hearth furnace practice. Therefore a one-ton (2000-lb.) acid open-hearth furnace was built. Furnace Design There are no special features in the design of this furnace. Standard acid open-hearth practice is followed, with the reproportioning of the dimensions necessitated by its small size; notably, a considerably increased length in proportion to width in order to get proper flame propagation. After the first heat was made it was found that the check-ers were insufficient. The checker chambers were increased in size and the checker openings were made much smaller. The furnace was started late in March, 1927, and made 65 heats. Experimental work was then stopped unti1, the data accumulated could be worked up and summarized. The run was resumed in November and the furnace is still operating, having made at this writing 60 additional heats. For the last series of runs, there was some rebuilding of both the furnace itself and the checkers. Slag pockets were added. Fig. 1 shows details of construction; Fig. 2, the general appearance. All designing was done by the operating and engineering staff. Construction materials were those available around the plant. The reversing valve is a standard butterfly type taken from an old furnace. The slag pockets and checkers are cleaned by digging down to arched openings which have been bricked up.

By G. E. Erdman

Gouverneur Talc produces a dry mineral filler from the tremolite talc rocks located near Gouverneur, New York. The raw material for this rock powder is a silicate rock and dust is controlled by water sprays whenever it becomes a problem underground. In the milling operation, there are some nine baghouse-type dust collectors which are utilized for the control of dust created in the crushing and grinding process. These collectors have been installed over a period of years since 1947 and are assigned to specific areas where the particle sizing of the dust can be returned to the plant circuit or product involved at the point of collection. It has been found very advantageous to mount most of these collectors on the top of the mill building and packhouses where the return of the dust can be accomplished by a gravity feed. In the years of effort involved in efficient control of dust generated in the plant, many things have been learned in the construction of ducts for control valves. The company has found useful such things as grasshopper legs for interconnecting silos with similar products, the elimination of fiat dust ducts, cleaning cyclones for coarse dust or heavy loadings, refractory linings for cyclones and certain duct areas, and the avoidance of square intersections when diverting or combining ducts. Operating cost records indicate that collectors handling the finest dust have the least expense. Operating costs on high-temperature dusts generally run higher than other types of material collected. Experience further indicates that the multiple cyclone-type collectors can provide a low cost and efficient way of removing hot dusts from process air streams before the introduction of the material into a baghouse. High moisture conditions and cold northern climates have been found to combine and create conditions under which baghouses can not efficiently function as dust collectors. Gouverneur Talc feels that its several dust collection systems have been a considerable maintenance expense but well worth the cost when it came to safeguarding the employees' health and preventing air pollution.

Jan 1, 1974

By V. H. Wilhelm

During the first half of the year 1935, the oil industry in California was on a fairly profitable basis, owing mainly to the operation of the Petroleum Marketing Agency. Coincident with the discontinuance of enforced curtailment, California production surged upward from an average of about 500,000 bbl. per day (over the first five-month period) to approximately 625,000 bbl. per day (over the last seven-month period). On Dec. 9 the state production had reached a peak of over 700,000 bbl., a figure that had not been approximated since the early days of voluntary curtailment (Fig. 1). A price cut was instituted during the last half of August, but had no deterring effect on operators that were determined to take advantage of the breakdown of curtailment and produce to capacity. New reserve figures, compiled from actual potentials, available after cessation of curtailment, revealed the startling fact that California reserves were rapidly declining. This situation, coupled with the desire among operators to obtain a more equitable price for their dwindling reserves, caused a restoration in November of a portion of the August price slash. A further rise in price was effected in early December, and crude quotations at the end of the year closely approximated those in effect during the first right months. At the close of the year, the industry felt confident that the production situation was under control. In all fields where competition is keen because of close spacing, production is gradually declining. In the Los Angeles Basin especially there is no likelihood of a large amount of overproduction, unless a new pool is discovered or deeper drilling reveals a prolific source of crude. As long as the fields that are operated by a few companies, such as Kettleman Hills, North Belridge, Ventura Avenue, West Coyote, Dominguez, and some others, can be controlled, it is believed that the overproduction problem in California will be solved.

Jan 1, 1936

By V. H. Wilhelm

During the first half of the year 1935, the oil industry in California was on a fairly profitable basis, owing mainly to the operation of the Petroleum Marketing Agency. Coincident with the discontinuance of enforced curtailment, California production surged upward from an average of about 500,000 bbl. per day (over the first five-month period) to approximately 625,000 bbl. per day (over the last seven-month period). On Dec. 9 the state production had reached a peak of over 700,000 bbl., a figure that had not been approximated since the early days of voluntary curtailment (Fig. 1). A price cut was instituted during the last half of August, but had no deterring effect on operators that were determined to take advantage of the breakdown of curtailment and produce to capacity. New reserve figures, compiled from actual potentials, available after cessation of curtailment, revealed the startling fact that California reserves were rapidly declining. This situation, coupled with the desire among operators to obtain a more equitable price for their dwindling reserves, caused a restoration in November of a portion of the August price slash. A further rise in price was effected in early December, and crude quotations at the end of the year closely approximated those in effect during the first right months. At the close of the year, the industry felt confident that the production situation was under control. In all fields where competition is keen because of close spacing, production is gradually declining. In the Los Angeles Basin especially there is no likelihood of a large amount of overproduction, unless a new pool is discovered or deeper drilling reveals a prolific source of crude. As long as the fields that are operated by a few companies, such as Kettleman Hills, North Belridge, Ventura Avenue, West Coyote, Dominguez, and some others, can be controlled, it is believed that the overproduction problem in California will be solved.

Jan 1, 1936

By Edward F. Fitzhugh

Quantitative appraisal of the chances of finding various tonnages and grades of ore clarifies any exploratory development proposal. Ways are discussed of appraising chances in conformance with probability principles, and graphs are suggested to show tonnages, grades and the corresponding judged expectancies. Introduction When exploratory development of a mineral deposit is contemplated, three interrelated questions normally must be answered before a sound decision can be reached. How much will the program cost? How much will the anticipated ore add to the immediate value of the mine? And what is the chance of developing this ore? To justify development, the deposit should present a favorable disparity between the three factors, cost, chance and return. If, for example, there is a 50-50 chance of success, the ore that is sought should have an immediate worth (after deducting all subsequent charges that it must bear) of more than twice the cost of the development. Likewise, if the chance of finding the ore is but one in five, that ore should enhance the immediate value of the mine by more than five times the cost of developing it- With sound economic and operating assumptions, the cost of exploratory development and a present value of anticipated ore may be estimated within reasonable limits. Less general attention has been given to appraising ore chances in comparable terms. The exploratory experience of the mining industry is broad enough that knowledge, vision and judgment may be combined to yield more tangible evaluations of Ore expectancy than are now customary' A way of making such appraisals is suggested herein. The mathematics of probabilities cannot be applied directly to the search for ore. By coupling applicable principles of probability, however, with pertinent experience gained in mineral exploration, an estimate often can be made of the chance of finding a certain tonnage and grade of Ore in a specific location. Such estimated, or judged, expectancies for the several blocks of ground in a deposit may be combined in a simple chart to show the relationship of the various exploratory possibilities and the potential magnitude of the deposit' An engineer or geologist may find that the quantitative thinking required for an appraisal of this type is an aid in clarifying and coordinating his views and recommendations. For a person wishing to understand these views, an ore-expectancy

Jan 1, 1949

By Edward F. Fitzhugh

Quantitative appraisal of the chances of finding various tonnages and grades of ore clarifies any exploratory development proposal. Ways are discussed of appraising chances in conformance with probability principles, and graphs are suggested to show tonnages, grades and the corresponding judged expectancies. Introduction When exploratory development of a mineral deposit is contemplated, three interrelated questions normally must be answered before a sound decision can be reached. How much will the program cost? How much will the anticipated ore add to the immediate value of the mine? And what is the chance of developing this ore? To justify development, the deposit should present a favorable disparity between the three factors, cost, chance and return. If, for example, there is a 50-50 chance of success, the ore that is sought should have an immediate worth (after deducting all subsequent charges that it must bear) of more than twice the cost of the development. Likewise, if the chance of finding the ore is but one in five, that ore should enhance the immediate value of the mine by more than five times the cost of developing it- With sound economic and operating assumptions, the cost of exploratory development and a present value of anticipated ore may be estimated within reasonable limits. Less general attention has been given to appraising ore chances in comparable terms. The exploratory experience of the mining industry is broad enough that knowledge, vision and judgment may be combined to yield more tangible evaluations of Ore expectancy than are now customary' A way of making such appraisals is suggested herein. The mathematics of probabilities cannot be applied directly to the search for ore. By coupling applicable principles of probability, however, with pertinent experience gained in mineral exploration, an estimate often can be made of the chance of finding a certain tonnage and grade of Ore in a specific location. Such estimated, or judged, expectancies for the several blocks of ground in a deposit may be combined in a simple chart to show the relationship of the various exploratory possibilities and the potential magnitude of the deposit' An engineer or geologist may find that the quantitative thinking required for an appraisal of this type is an aid in clarifying and coordinating his views and recommendations. For a person wishing to understand these views, an ore-expectancy

Jan 1, 1949

By Nigel B. Pearson

INTRODUCTION Chingola Division of Nchanga Consolidated Copper Mines Limited is situated in the Copper- belt of Zambia, approximately 30 kilometres south of the border with Zaire. It is the country's leading producer of copper and its principal foreign exchange earner, and has been, in its time, the largest single copper producer in the British Commonwealth and the second largest in the world. There are two 'primary' copper sources at the Division, namely Underground producing approximately 100 000 tonnes of contained copper annually, and the Open Pits, producing approximately 200 000 tonnes annually. Following the commissioning of the Tailings Leach Plant in 1974, treating final tailings, metallurgical recovery increased from approximately 70% to in excess of 80%. Extensive deposits of cobalt are present and following the rise in the market price in 1979 and 1980, plans were made to extract this separately. Cobalt production commenced in 1980 from Underground and will increase substantially when the Open Pit cobalt reserves become available in approximately 2 years time. This paper covers the development of the production method of the principal Underground Orebody, known as the Lower Orebody, and the control systems applied to it. HISTORY The Lower Orebody, formerly known as the Nchanga West Orebody, was discovered by extensive Diamond Drilling operations in the late 1920's. Development of the Shaft complex and the orebody commenced and continued until 1931 when flooding from development on the 480 foot horizon necessitated closure. The mine remained closed until 1937 and production commenced from the Lower Orebody in 1939. Various expansion schemes of the Metallurgical Plants and the Underground workings were completed over the years with the result that Underground production increased steadily to in excess of 150 000 tonnes copper annually in the 1960's. In recent years production has levelled out at slightly less than 100 000 tonnes annually. This decrease is as a result of producing from a lower grade reserve, available within a more limited production front, and the application of production constraints in the light of experience gained. GEOLOGY Within the Nchanga Mining Licence Area of Chingola Division, there are a total of 14 known copper orebodies in the basal part of a thick succession of sediments of Pre-Cambrian age. The sediments rest on a Basement Complex of granites, gneisses and schists. Three superimposed stratiform orebodies, known locally as the Lower, Intermediate and Upper Orebodies, occur over a vertical interval of approximately 150m. Current annual copper production is approximately 300 000 tonnes. The ore originates from four different mining operations, one Underground mine and three Open Pits. Approximately 9 million tonnes of ore grading between 3 and 3.5% copper are milled annually. The two largest sources of ore, the Under- ground mine and the Nchanga Open Pit are on the gently dipping south limb of the Nchanga Syncline (Figure 1). In the Nchanga Open Pit the major source of ore is the Upper Orebody with lesser tonnages from the Intermediate and Lower Orebodies. In the Underground mine the Lower Orebody is the only orebody being mined, underground mining of the Upper Orebody being suspended for economic reasons in 1978. The typical stratigraphic column is illust- rated in the legend on Figure 1. The footwall rocks comprise either Nchanga Red Granite or the Arkose formation, both of which are hard competent rocks, offering generally good mining conditions for footwall development. Copper mineralisation of the Lower Orebody extends from the upper part of the Arkose to the top of the Lower Banded Shales. Overlying the Arkose is the Transition zone (0-18111 in thickness). The Transition zone comprise a lower member, Transitional Arkose, consisting of incoherent kaolinised sandstone, and an upper member, Transitional Lower Banded Shales consisting of normally soft bleached and silicified shale. The soft nature of the Transitional rocks is

Jan 1, 1981

By T. Leser, A. W. Jenike

The problems of caving and underground subsidence can be considered as the failure of a highly compacted rock and its subsequent flow in the form of broken rock. The problem is complex because the propagation of failure and flow have to be considered simultaneously; the yield strength of the virgin rock and the broken rock are different; and, while under certain conditions it is sufficient to consider the virgin rock as homogeneous, the density and the yield function of broken rock are both pressure and time dependent. A study of the failure and flow of solids with a pressure dependent yield function has been published recently by Jenike.' In this paper the density of the broken rock is assumed to be only time dependent and the consequences are examined in the case of one-dimensional vertical subsidence into an initial cavity. The following describes an attempt to develop a tool which, in combination with other tools, may lead to mathematical solutions of real problems of caving and subsidence. STATEMENT OF THE PROBLEM An underground cavity of horizontal cross section 4 = 1 and height 6 is assumed to exist at some depth below the surface. At the time t = 0 rock above the cavity fails and completely fills out the cavity with expanded broken material. With passing time the broken rock consolidates and subsidence proceeds continuously upuard in a vertical shaft. The phenomenon is one-dimensional (see Fig. 1). The problem consists of finding the displacement and the velocity with which the frlmt of the subsidence (wave front) moves upward as a function of the time and of the rock properties. DIFFERENTIAL EQUATIONS CONTROLLING THE PHENOMENON With the assumptions that the broken rock is a continuum and that the subsidence occurs continuously, we can apply the one-dimensional differential equation of contitiuity (conservation of mass) and the equation of preservation of momentum The latter equation is replaced by an assumed relation based on experience, which takes care of the

Jan 1, 1962

By C. E. Webber

THE economical recovery of the valuable constituents from the effluent of gas-con-densate wells has developed into a problem of balancing the cost of recovery against the cost of compressing the residual gas back into the formation. A possible method of extracting the gasoline and distillate from the natural gas is by oil absorption at high pressures. In order to design and evaluate an absorption plant, fundamental data on the composition of the coexisting hydro-carbon vapor and liquid phases at various temperatures and pressures are essential. A review of the literature indicated that the necessary data for the design of such plants are lacking. The nearest approach to desired published data is that of Katz and Hackmuth,5 who experimentally deter-mined the composition of the coexisting vapor and liquid phases in a natural gas-crude oil system at pressures up to 3000 lb. per sq. in. and at temperatures from 40° to 200°F. This paper presents the results of the experimental determination of the equilib-rium distribution of the hydrocarbons methane through hexane between natural gas and a typical absorber oil. The ranges of temperature and pressure chosen were from 33° to 180°F. and from 100 to 5000 lb. per sq. inch.

Jan 1, 1940

By William P. Blake

In southern Arizona and in Mexico the word caliche is in general use to denote a calcareous formation of considerable thickness and volume found a few inches, or a few feet, beneath the surface-soil, upon the broad, dry, gravelly plains and mesas. , In western South America the same name is applied to the beds of crude soda-niter (Chili saltpeter). While these deposits of South America and of Arizona are totally different in composition, and have nothing in common, except that both occur in

Jan 1, 1902

By R. I. Garrod, R. A. Coyle

The shapes and positions of X-ray reflections from specimens of copper, steel, and aluminum alloy haue been examined in the elastic and plastic ranges both while the specimen was under stress and in the unloaded condition. For the aluminum alloy the shape was unaltered by the application of stress either within the elastic limit or in the plastic range provided that no additional plastic strain was induced. In copper the broadening accompanying plastic deformation was very slightly reduced when the specimen was unloaded. A similay but more marked elastic component of broadening was also found for steel, but in this case below the yield stress. Line profiles corrected for instrumental and particle-size broadening indicate very large internal stresses in local regions of the plastically deformed metals. The results are discussed in terms of a recent suggestion that the heterogeneous dislocation distribution between the cells and their boundary walls plays a major role in the peak shifts and broadening of the X-ray reflections. STUDIES of the X-ray line profiles from strained polycrystalline aggregates concentrate usually on one or the other of two main parameters: a) the displacement of the peak of the intensity contour from its position for a strain-free aggregate, or b) the shape of the profile. From peak shifts data can be obtained either on the relation in both the elastic and plastic ranges between applied external stress and average lattice strains in a given (hkl) direction, or, alternatively, on the residual lattice strains which are present after a plastically deformed specimen is unloaded.' On the other hand, the shapes of the broadened profiles from cold-worked metals can be analyzed to separate the broadening produced by small particle size and by heterogeneous lattice strains.' In this paper the terms "size broadening" and "strain broadening'' are used in the general sense adopted by warren.' In the past, apart from two early qualitative observation, it has been customary to examine only the movements of the peaks of the profiles while the specimen is actually under load, since the line broadening induced by plastic strain remains after removal of the external stress. Consideration of the implications of existing data of this type suggests, however, that fruitful additional information on a number of fundamental aspects might be gained by careful examination of whether the X-ray line profile is in fact different in the loaded and unloaded states of the specimen. By taking advantage of the sensitivity and convenience of modern diffractometer techniques it is possible to explore with relative ease the magnitude and importance of any elastic effects which may be superimposed upon the well-known permanent changes in profile. The main aim of the work to be described was thus to investigate this point for typical metals and alloys. For this purpose annealed specimens were extended first elastically and then plastically and the positions and shapes of X-ray reflections were recorded. Initially it was anticipated that prime interest would center on observations within the plastic range; it has been found, however, that small changes in profile sometimes occur both before and after the nominal elastic limit of the material is reached. It is shown that the results obtained have important implications in relation to the structural changes and processes associated with deformation. I) EXPERIMENTAL To enable the diffraction lines to be recorded while the specimen was under uniaxial-tensile stress, a small hydraulic testing machine was designed and constructed for direct attachment to the goniometer of a Philips diffractometer. The specimens, which were machined from 1/2-in.-diam rod and had a central rectangular section 3/8 by 1/16 in. over a gage length of 1 in., were held in the machine by split collets mounted in grooves in the cylindrical ends of each specimen. No special precautions were taken to ensure precise axiality of loading. Constant oil pressure was maintained by a lever and weights system and transmitted to the loading rig by flexible pipe. The actual load on the specimen was measured by a load cell in the machine to an accuracy of * 1 pct. To enable smooth X-ray profiles to be obtained the specimen and machine were oscillated continuously during recording through *7-1/2 deg about the normal half-angle position of the goniometer. The three materials chosen for the investigations were high-purity copper as representative of a ductile fcc metal, a low-carbon steel for a bcc metal, and an aluminum alloy as a material in which the proof stress/ultimate strength ratio is high. Details are as follows. a) Copper. 99.999 pct purity. After machining the specimen surface was polished mechanically and

Jan 1, 1964