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By T. Cameron Kenney

INTRODUCTION Whereas the design of rock slopes in open-pit mines is done largely by mining engineers and geologists, the design of slopes in overburden at this point in time is a problem for which civil engineers or geotechnical engineers are best prepared to deal. The reasons for this situation are to be found in the educational curricula and the technical journals of the two groups, where soil mechanics has received little attention by mining engineers and geologists, and rock mechanics has similarly received little attention by civil engineers. In ten years' time this paper will hopefully be considered by young mining engineers to be a repeat of the material that they studied at university. However, even in ten years time I believe that the civil (or geotechnical) engineers will be extensively used as consultants on overburden- slope problems of open pit mines because mining companies will find this more expedient than maintaining their own geotechnical staff, special field equipment and special testing laboratories. For this reason, the purpose of this paper is not to condense several university soil mechanics courses into a twenty-page text for mining engineers and geologists. Rather, the purpose of the paper is to offer a general explanation of various factors affecting slope stability so that mining engineers and geologists will have a better understanding of the behaviour of overburden soils in slopes. A great deal has been written in soil mechanics literature on the subject of slope stability. No attempt will be made to reference all this material but rather only a selected number of references will be cited. Excellent general treatments of the subject of stability of overburden slopes are available (1,2,3,4). Further information of a more specialized nature is to be found in such publications as the Journal of the Soil Mechanics and Foundation Division of the American Society of Civil Engineers, Geotechnique (printed by the Institution of Civil Engineers, England), Canadian Geotechnical Journal, and the proceedings of the conferences of the International Society for Soil Mechanics and Foundation Engineering. FACTORS INFLUENCING SLOPE STABILITY There are two general scales of slope-stability problems, gross stability and local stability. Gross stability refers to large volumes of soil, and gross instability would involve large rotational-type shear failures. Local stability refers to something much smaller and examples

Jan 1, 1972

By Peter H. Fletcher

THE ECONOMIC THEORY It will assist in the understanding of the Resource Rent Tax ("RRT") proposals in Australia if the economic theory behind the tax is briefly explained. The idea goes back to the concept of rent put forward by the nineteenth century economist David Ricardo. His analysis was broadly as follows: A tenant who farms land which is just on the margin of economic viability cannot afford to pay his landlord any rent, because the value of the crop produced by such marginal land is equal to the cost of producing the crop, plus the cost of keeping the tenant alive. There is nothing left out of which to pay rent to landlord. A tenant who farms good land can afford to pay his landlord rent -- but the maximum amount of rent that he can be asked to pay is the excess of the value of the crop produced by the good land over the cost of producing the crop and of keeping the tenant alive. Adapting this theory to the taxation of mining projects, modern economists who favour this system of taxation say that a profitable mining (or resource) project produces rent in the Ricardian sense. The amount of the rent is the excess of the profits by the project over the amount of profit which is required to attract the taxpayer to invest in the project in the first place. This explains why the tax is called "Resource Rent Tax". PAPUA NEW GUINEA PRECEDENT Although Papua New Guinea ("PNG") is now independent of Australia, there are still close links between the two countries, and strong similarities between their respective tax regimes. PNG introduced an Additional Profits Tax ("APT") in 1978. In many respects, Australia's RRT proposals follow the precedent set by PNG1s APT. However, in practical terms, not a great deal can be learned at this stage from PNG's experiences since, according to the writer's understanding, no PNG mining project has yet paid any APT. The Bougainville mine is not liable to APT, being subject to tax under its own separate Act, which contains a different formula. Outline of PNG Additional Profits Tax. PNG has two versions of Additional Profits Tax ("APT) - one applying to general mining, the other to petroleum mining. The two versions are very similar. The general mining version is described below. The tax applies on a licence by licence basis. This means that losses on Licence A cannot be offset against profits on Licence B. Expenditure relating to two or more licences, is apportioned "in such manner as the Chief Controller thinks reasonable". Tax is levied on the "accumulated value of net cash receipts" at the rate of (70 - n)% where n=the rate of income tax. The accumulated value of net cash receipts ("av") is calculated as follows: Calculations commence from the first year in which substantial expenditure was incurred on the construction of facilities for the carrying out of mining operations on the licence. For that year the av consists of the total allowable expenditure to date on that lease. For the second year, the av is the av at the end of year one indexed in accordance with the statutory formula set out below, plus the total allowable expenditure in year 2. For year 3, the av is the av at the end of year 2 adjusted by the index factors, plus the total allowable expenditure in year 3. This process is repeated year after year. When the licence starts to earn revenue, the revenue is deducted from total allowable expenditure for that year. If revenue exceeds total allowable

Jan 1, 1985

By B. Fagerberg, P. H. Fahlstrom

Crushing and grinding practice in Sweden follows closely the international pattern. Certain special circumstances, however, have had an influence on its development. Most mines are worked underground. These mines are either quite small or very large. Sulfide ores are commonly treated by custom milling and, apart from the cement industry, the rock species treated are hard and abrasive. Another important factor is the increasingly strict requirements placed on the mechanical condition of different products, especially lump ores and coarse iron-ore concentrates. Increasing requirements are being placed on the concentrate grade to suit the new steel processes. As a result, iron ore beneficiation has expanded considerably for the production of fine pelletizing concentrates. This applies especially to magnetite ores in the intermediate phosphorus range 0.1-1% P. In 1969, about 5.5 million tons of pellets will be manufactured. It should be pointed out, however, that fairly large quantities of coarse products are still being made at mills where the right conditions are available. Crushing and grinding is also of great importance in the production of rich concentrates at high recovery from sulfide ores. In fact, a large part of the development work on the concentration of sulfide ores has been devoted to the crushing and grinding processes. Boliden has played an important role in this connection.

Jan 10, 1969

By Richard N. Grigsby

INTRODUCTION The Chord property was acquired in 1975 from Roy Chord, an early prospector and miner of the area. He had staked numerous claims on the southern flank of the Black Hills in the early 19501s, and by the late 50’s, many small open pit and underground mines had been or were in operation. By the mid 1960's small tonnages of high-grade oxidized uranium ore had been mined from the property. Starting in 1975, Union Carbide conducted a series of exploration programs to determine the remaining economic potential. The previously mined areas were re-examined in order to define additional oxidized mineralization. Meanwhile, a wide-spaced drilling program was initiated to determine the potential for deeper unoxidized deposits. Through the exploration program of 1979, measured minable reserves in excess of two million pounds of contained uranium had been discovered. GEOLOGY The Edgemont District is located on the southern end of the Black Hills Uplift. A succession of pre-Cambrian to Cretaceous Formations is exposed within the core and across the flanks. The uranium host is the lower Cretaceous Inyan Kara Group which is divided into two formations, the Lakota and Fall River Formations (Figure 1). The basal Lakota Formation rests unconformably on the Jurassic Morrison Formation and consists of fluvial channel sandstones

Jan 1, 1983

By Floyd Kelley

THERE is an ever-increasing demand for furnaces with controlled atmosphere, due to the large quantities of steel being used in the automotive industry, such as the .high-chromium stainless irons, the 18 Cr, 8 Ni stainless iron and low-carbon steel sheets. The difficulties involved in the annealing of such materials, if they are to be kept absolutely free from oxidation, are many. It is possible to bright-anneal these steels in small laboratory hydrogen furnaces, using specially purified hydrogen and taking some additional precautions. In the first place, the insulation, usually of alumina or magnesia, holds small amounts of water vapor, which it is almost impossible to remove completely. Secondly, there is always condensation of water vapor in the cooling chambers of such furnaces, and with the continuous circulation of the hydrogen gas in the furnace, the water vapor is carried from the cooling chamber back into the heating chamber. This water vapor oxidizes the charge. Lastly, the supply of moisture is made sure by the diffusion of small amounts of air from the atmosphere into the furnace against the pressure of the hydrogen. The oxygen combines with the hydrogen and forms more water. Under such conditions there is, little gained by using specially purified gas, because it becomes contaminated after reaching the furnace.

Jan 1, 1931

By Wido Tilmann

13.6-1. Importance. In Germany there are large tertiary brown coal reserves, most of which are located close to the surface. Therefore, brown coal has been recovered for many years by means of opencast methods. By utilizing a high degree of technology, a rational operation has been achieved, and as a result, the mining techniques have become renowned all over the world. After the war, all the dredgers and overburden spreaders, as well as the means of conveyance, had to be redeveloped for adapting this equipment to the changing conditions of the deposits. Numerous auxiliary machines were adopted from the American earth moving industry and altered according to the different requirements. As a result of such technical developments, the output per man and per shift was increased remarkably in spite of the deterioration of the geological conditions. In the whole of Germany, the total reserves of brown coal amount to 100 billion metric tons, of which 60 billion tons are situated in the Federal Republic of Germany. In the latter area, 8.5 billion tons will be recover- able by opencast means, of which 3.5 billion tons are already developed. The annual output reached 102 million tons in 1965. This total figure comes from four different mining districts: Rhineland, Helmstedt (town at the border of the Soviet occupied zone), Hesse, and Bavaria. The production figures (1965) are as follows: [ ]

Jan 1, 1968

By AIME AIME

ON the morning of Monday, Nov. 9, 1936, two motorcycles, with sirens screeching, - escorted a procession of 70 automobiles from the Colonia Railway Station in Mexico City to the Hotel Geneve. Riding in' the cars were just over 200 visitors- members of the A.I.M.E. and their guests. They had come, via St. Louis, in two special trains from 24 different states for the 146th General Meeting of the Institute. During the morning they and 200 others, who had come from the United States by automobile or from various cities and mining camps in Mexico, duly registered with !efficient Mme. Irma Ordoiiez de Obregon and her assistants. Then started a week of strenuous but delightful activity that will never be forgotten by the participants. They were to cover more than 500 miles by automobile, always with a motor escort, and often

Jan 1, 1937

By D. B. Williams

The end of the war in Europe and the Pacific failed to curb the upward trend of production in Venezuela,- which easily surpassed that of any previous year. The total production for 1945 amounted- to 323,369, 430 bbl., which was 26 per cent over the total for 1944, the previous peak in the history of the oil industry of the country. This increase was caused mainly by the greater demand for petroleum in the last stages of the war; the fact that the danger from enemy submarines had been overcome, which allowed all oil companies to use increased shipping facilities, and the fact that more materials were available for drilling operations. However, the materials supplied were by no means adequate and considerable credit is reflected on the Venezuelan petroleum industry for the increased production obtained by utilizing all available equipment to its fullest extent.

Jan 1, 1946

By George D. Roberts

INTRODUCTION CIVIL engineers are primarily interested in maximum core recovery. This is even more important in foundation work than in mining investigations where sludge samples are of some value. The soft materials, such as clay, gouge, or partially decomposed seams that are most readily ground up or washed away, are the materials that usually have the greatest influence on foundation and leakage conditions. Undisturbed samples of such materials should be obtained for detailed geological examination and laboratory tests. Therefore the attainable goal of sampling in connection with foundation investigations is the recovery of 99.9 pct of undisturbed core. FACTORS CAUSING CORE LOSSES The principal factors contributing to core losses are: (I) coring badly fractured or very soft material; (2) use of improperly designed coring equipment, including the use of bits of too small a diameter; (3) lack of the proper training and attitude on the part of the drillers and pertinent technical information on the part of the supervising personnel. Little can be done about the character of the material being cored but the other two factors contributing to unsatisfactory performance can be corrected. Although the title of this paper is the improvement and standardization of core barrels, it is believed that the drillers' shortcomings and the lack of pertinent technical literature are more detrimental to good core recovery than either of the other factors. USES FOR LARGE DIAMETER CORE BARRELS It is well known that the use of larger diameter bits and core barrels generally produce better cores, particularly when sampling soft or broken material. The use of larger and larger bit diameters and the insistence on better core recovery is well demonstrated by the change in practices of the various districts of the Corps of Engineers. Today NX core is the smallest diameter commonly permitted for investigational work and the more active districts are using coring bits up to 6 in. in diameter, as well as 36 and 40-in. calyx rigs. The latter size has proved to be just as economical because it provides more room for core removal and cleanup operations. The use of large diameter cores to replace the driving and jacking methods of obtaining soil samples is also increasing. The 5 7/8-in. Denison sampler, developed by H. L. Johnson to obtain samples from soft formations, is one example. The principal uses for bits larger than NX are: sampling soils and semi-consolidated rock; sampling decomposed rock or rock with soft seams; sampling concrete; obtaining samples for laboratory tests; drilling drainage holes, and other miscellaneous work. CORE DRILLING PRACTICES OF SEVERAL ENGINEER DISTRICTS Little Rock District The writer was employed in the Little Rock District from 1938 until 1942. Prior

Jan 1, 1947

By G. L. Oldright

THE metallurgist is familiar with the rapid development of concentration -by flotation and smelting in the reverberatory in recent years, brought 'about chiefly by the exhaustion of' bodies of .rich, coarse, direct smelting ore. Geologically speaking, in many porphyry-copper districts, the richer contact or replace let deposits surrounding 'the main ore-forming igneous intrusion have been exhausted, and it is necessary to beneficiate the copper minerals disseminated throughout the mass of the intrusion itself. The organization of great companies to treat such low- grade ores on a large scale and the practices resulting from the necessity for an economic method of treatment 'are among the most prominent metallurgical developments of the past decade. It is interesting to note the effect of the present trend of practice on the inter-relationship of the concentrator and smelter, on the constituents of the smelter charge, and on smelting in general.

Jan 1, 1925

By Dwight M. Lemmon

Encouraged by increased demand and higher prices for such metals as copper, lead, zinc, silver and tin, search was pressed in 1964 for mineral raw materials, especially in parts of the world that are relatively more stable politically and economically. New discoveries of metallic ores continued to be made, discoveries based on extensive geologic and geophysical work but nonetheless made in part because of good fortune.

Jan 2, 1965

By P. Sanchez-Mejorada

GEOLOGISTS who are acquainted with the mines of northeastern Mexico realize that the most important lead-silver replacement deposits of the province are confined to a single formation. But since the formation is several hundred meters thick, the author has determined the relative position of the lead mantos in the belief that this information will prove useful in the search for new mines. This article describes the stratigraphic location of lead-silver replacement deposits known in several mines situated in a region comprising part of the states of Coahuila and Nuevo Leon. The area studied extends for 200 km* (125 miles) from east to west and 70 km (45 miles) north to south.

Jan 1, 1958

By L. K. ARMSTRING

ANYONE doubting prosperity in the mining industry should visit the Kootenays of British Columbia where the West Kootenay Power & Light Co. is kept busy running new power lines and connecting mines and mills with lines already in service. Quoting from an inspired statement "The four hydro-electric plants of the West Kootenay Power & Light Co. on Kootenay River have been in continuous operation." At the recent 35th annual meeting of the Eastern' British Columbia Boards of Trade held in Nelson, a two-day session indicated unusual activity. The following information was obtained through personal contact, through the press, and by hearsay. Much of it has been checked and proved accurate. Reversing the order of the flowsheet. Secretary J. R. Hunter reported as fol¬lows regarding the value of the 1934 production of the Consolidated Mining & . Smelting Company's metallurgical, plants at Trail and Tadanac:

Jan 1, 1935

By M. E. Bell

The term "operational research" was probably first used to describe work started under E. C. Williams, now Director, SHAPE Air Defense Technical Center, late in 1937 or 1938, at the Bawdsey Research Station of the British Air Ministry, a laboratory center concerned with the development of radar equipment. After the practicability of the early techniques had been demonstrated, a large (for those days) program of development and installation was authorized. It was very soon realized, both by the Royal Air Force and by the scientists that almost as important as the gear itself was the way in which it should be used. Accordingly, it was decided that some scientists should cooperate to study the way in which the equipment should be deployed and operated in conjunction with the Royal Air Force. To distinguish this work from the normal work of a research and development establishment, the term "operational research" was coined. It merely meant at this time that this particular section of scientists was to be concerned with the use of the gear rather than with its technical development and it seemed natural to those concerned to adopt the word "operations" which has a specific connotation in the armed forces.' This method was later extended to peacetime business enterprise, government operations and other human activities. Operations research appears to have penetrated the extractive industries more slowly and less completely than other industries, the military, or the government. This may be due (1) to a difference in the attitude of management towards operations research, or towards research of any kind, for that matter; (2) to unsuitability of the extractive industries for application of the operations research method; (3) to inaccessibility of the data; (4) or to a lack of trained personnel who are interested in applying operations research to the mineral industries.

Jan 8, 1963

By Z. T. Bieniawski

The importance of understanding the phenomena associated with rock fracture has long been fully appreciated in rock mechanics. This is clearly apparent from the special attention paid to rock fracture in the comprehensive papers published within the past four years.l-5 These papers present a picture of how the knowledge of brittle fracture of rock was gradually enriched and also show that what was often taken for granted three or four years ago is no longer considered as valid today. The Griffith hypothesis,6 thought in the past to predict the strength of rock, is now known to be applicable to fracture initiation only. The knowledge of a failure criterion for fracture initiation is not sufficient, however, as after fracture initiation the rock is still a useful material even possessing increasing load-bearing ability. The importance of the fracture propagation process, subsequent to fracture initiation, is thus obvious. Yet, relatively little attention has so far been paid to brittle fracture propagation in rock. As it is now realized that understanding of this process is a prerequisite for practical rock mechanics applications, studies of propagation of brittle fracture in rock constitute an important aspect of rock mechanics research. It has been pointed out 4 that it is essential that the failure mechanism is fully understood before a failure criterion is postulated. Many failure criteria have been propounded in the past on the basis of theoretical reasoning alone and could not be verified by experimental evidence. Recently, a hypothesis for the mechanism of brittle fracture of rock was propounded, 4 describing the events taking place in the rock from the initial application of gradually increased load to complete disintegration of the material.

Jan 1, 1972

By K. D. Snyder

Barite deposits occur in the Iglesiente-Sulcis district of southwestern Sardinia, an historically important lead-silver-zinc district. Barite, often genetically associated with the base metal deposits, has become an independently important economic commodity. Barite deposition in southwestern Sardinia was related to Caledonian, Hercynian, and Alpine orogenic cycles. A model is presented that relates synsedimentary, karstic, vein, and residual deposits. Synsedimentary deposits are widespread, have common depositional characteristics, and act as sources, along with hydrothermal systems, for other barite deposit types. Caledonian-, Hercynian-, and Alpine-related secondary enrichment processes resulted in residual and karstic deposits that are complex in terms of their geometry and texture, but are more economically important than those of synsedimentary or hydrothermal origin.

Jan 1, 1985

By J. J. Jakosky

THE fundamental hydrodynamic principles governing the production of oil from wells have been carefully studied and evaluated by many investigators. These prior studies are quite complete and cover virtually the entire field of oil production and recovery.1 One of the most impor-tant measurements in production studies is that of the bottom-hole pressure at various rates of production.2 It is the purpose of this paper to outline the technique and economics of fluid-level measurements as applied to pumping wells and to review briefly other methods for obtain-ing bottom-hole data. The applications of bottom-hole pressure or fluid-level measure-ments are based on simple hydrodynamic principles. Under equilib-rium conditions, pbh = hd + pg + pch [ l] when pbh = bottom-hole pressure, lb. per sq. in. absolute, h = height of fluid in well, ft., d = average fluid density, lb. per sq. in. per foot, pg = weight of section of gas column 1 in. square from fluid level to casing head, pch = casing-head pressure, lb. per sq. in. absolute. In words, equation 1 states that the bottom-hole pressure is equal to the weight hd of the column of fluid plus the weight of the column of gas between the fluid and the casing head plus the casing-head pressure. At moderate rates of flow, the rate of production is approximately proportional to the difference between the reservoir, or static bottom-hole, pressure and the flowing or producing pressure; i.e.: Q = c(pr - pbh) [2] pr = the reservoir pressure, c = the constant of proportionality. However, at production rates approaching zero and also at high rates the proportionality may break down. By combining equations 1 and 2 the

Jan 1, 1939

By George J. Young

The recurrence of mine-fires in Nevada during the past decade is not only a matter of interest, but also one of considerable concern to engineers and mine-managers. The more important fires may be enumerated as follows: Forman Shaft fire, Gold Hill, April 21, 1903; shaft-house, machinery, and shaft destroyed; loss estimated at $50,000; cause unknown. Union Shaft fire, Virginia City, July 14, 1904; shaft-house, machinery,and shaft in part destroyed; loss estimated at $100,-000; cause of fire stated as the careless throwing of a match in the rope-house. Sutro Tunnel fire, Virginia City, Jan. 27, 1909; 700 ft. of tunnel-timbering destroyed, and direct damage of $10,000; cause " probably electric wires." Belcher Shaft fire, Gold Hill, Aug. 9, 1910; shaft-house destroyed, machinery ruined, and upper part of shaft damaged; damage, $25,000; no cause given. Belmont Mine fire, Tonopah, Feb. 23, 1911; fire started ill winze; 17 men killed. Giroux Mine fire, Kimberly, Aug. 23, 1911; fire originated in shaft-station from unknown cause; 7 men killed, and $34,-521 damage caused. (Note 1.—On June 11, 1912, some time after the present paper was written, a fire broke out in the pump-room on the 2475 station of the Ward shaft, Virginia City. This fire was caused by the short-circuiting and exploding of the starting-switch on No. 5 pump. The oil in the switch was scattered about and set fire to the timbers and lagging of the pump-room. The pump-man in charge notified the surface, and the electric current was shut off. A hose was then turned on the fire, but the dense smoke drove the attendant out. Inspection by the electrician and the shaft-foreman, equipped with oxygen-

Jan 1, 1913

By David B. Campbell

Production of both metallurgical and thermal coal represents a significant sector of the mining economy of British Columbia. The coal measures are located in the Rocky Mountains, and the majority of the coal is produced by open pit mining. The coal seams occur interbedded with siltstones, sandstones, mudstones, and shales. Consequently, large volumes of waste rock are generated in the course of open pit mining. The waste rock is consigned to waste rock piles that of necessity must be developed on moderate to steeply sloping terrain. Some of the waste dumps currently under development will ultimately contain in excess of 500 million cubic meters of material, and some of the proposed waste piles will attain heights in excess of 300 m. These waste piles must be developed in a manner that will assure their stability through all stages of development, as well as over the long term after mining operations have been completed. This paper describes methods of waste dump development, factors affecting stability, modes of potential failure, and a simple method for monitoring movements to provide a warning of pending unstable conditions.

Jan 1, 1985

By Albert W. Giles

The splitting of the coal by partings is a familiar feature of many coal beds. The partings are normally argillaceous, more rarely sandy or calcareous. The material is usually fine-grained, less frequently coarse-grained to conglomeratic. Many partings are wedge-shaped, others are lenticular, and in some coal beds thin partings but one or two inches thick persist as thin sheets throughout areas of regional extent. The origin of the partings differs, and in some cases is obscure and uncertain. Origin of Thick Partings Wedge-shaped Partings Wedge-shaped partings are normally of indefinite linear extent but of short transverse section. They are developed adjacent to the borders of the original peat-forming swamp or around islands formed within the swamp, hence their presence is indicative of the approximate limit of the coal bed or of an interruption in the continuity of the coal bed. Following deposition of the parting gradual reestablishment of swamp conditions is followed by burial of the parting with accumulating peat. Partings developed adjacent to the borders of swamps normally thicken toward the periphery of the swamp and represent either detrital materials carried in from adjacent land areas during floods or materials carried in by advancing waves and currents after a barrier confining the swamp had been breached by the waves. Partings formed in the manner first mentioned should become coarser and more arenaceous toward the source of supply of the detrital materials, and the overlying and underlying coal should gradually grade into carbonaceous shale as the margin of the original swamp is approached. Partings formed by advance of waves across a barrier should be largely or entirely arenaceous, thin wedges of short longitudinal section, possibly with fossils of marine or brackish affinity. The subjacent coal normally should "pinch out" against the barrier, and the overlying coal continue to the barrier, or even extend across it, depending on the geographic conditions established following the breaching of the original barrier. Islands may be formed in swamps in a number of ways. They may represent local uplift of the swamp floor during earthquakes, or

Jan 1, 1934