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By Adrian Brown

INTRODUCTION The primary tool which is available to improve the stability of an open pit mine at a given slope angle is control of groundwater pressure. This paper sets out the methods by which water pressure control can be achieved in large mines in different materials. The emphasis of this paper is on large mine slopes because. these slopes exhibit the greatest need for groundwater control, the greatest economic benefit from groundwater control, and the greatest technical challenge in achieving groundwater control. STABILIZATION USING MTER PRESSURE CONTROL Groundwater pressures reduce the stability of slopes in two fundamental ways, as shown schematically in Figure 1. In the example, a horizontal failure surface intersects a vertical joint or weak zone. Water pressure acts: o On the base plane to reduce the normal force on the sliding surface and hence reduce frictional resistance to sliding, and o On the vertical back plane, to create a driving force for the system.

Jan 1, 1983

By Desmond De Villiers Oxford, Peter H. Williams

Nchanga Consolidated Copper Mines, Ltd., is one of the four mines operated by the Anglo American Corp. in Northern Rhodesia, now the independent nation of Zambia. Today Nchanga is the second largest single producer of copper in the world, accounting for more than 200,000 long tons of copper annually at a monthly milling rate of 430,000 tons of ore. The average mill-head grade is about 5.20% total copper, of which approximately 60% is copper sulfide. The remainder, referred to as "acid soluble," is copper oxide. Nchanga mines three separate orebodies varying in grade and sulfide-to-oxide ratio. Ore is processed in two separate grinding circuits feeding into three separate flotation circuits. A fourth flotation circuit treats leach plant residue for additional recovery of sulfides.

Jan 1, 1965

By AIME AIME

NO other man now on the Institute's Board has a record of long service to his professional society comparable with that of Karl Eilers. He joined in 1888; he was a Councilor as far back as 1909, a Vice-President as early as 1912, and for the last ten years has been continuously a Director and Treasurer. It seems fitting, therefore, that he is the only member of the present Board that is also an Honorary Member of the Institute. Karl Emrich Eilers was born near Marietta, Ohio, Nov. 20,,1865, which makes him 71 years old. Columbia School of Mines gave him his E.M. in 1889, after which

Jan 1, 1937

By C. E. Shoenfelt

The most important development in an otherwise colorless year in Colorado oil fields was the completion, late in 1933, of a well on Iles dome on the western slope of Colorado, with an initial production of 1100 bbl. of oil. No great amount of activity beyond the drilling of necessary offset wells is to be expected as a result of the completion of a well of this size because the acreage on Iles dome is closely held; there is no pipe line outlet other than to the Texas Company's small refinery at Craig, 24 miles distant; and the market for the oil is limited to the demands of sparsely settled communities in the high mountains. The Iles field is located on a large dome developed in Mancos shale of Cretaceous age, and having a closure of approximately 400 ft. The structure is highly faulted on the southern end. The first commercial oil well on this dome was completed by the Midwest Refining Co. on the south side of sec. 22-4N.-92W. Oil of 37" gravity was developed in Nancos shale at 2560 ft. and water in the Dakota sandstone at 2630 ft., but a considerable amount of additional oil was found in the shale immediately overlying the Dakota. From 2630 ft., the well produced in 16 hr. 750 bbl. of fluid, 33 per cent of which was water. Production in the Sundance sand of Jurassic age was found in the Midwest Refining Company's No. 4 Parkinson, in the NE.-SW.-SE. of sec. 22-4N.-92W., and completed on the last day of the year 1926, for an initial production of 450 bbl. of oil at a total depth of 3242 ft. The well completed in 1933 is also a Sundance sand producer and was finished at a depth of 3447 ft. It extends the productive area of the field about a quarter of a mile cast. The Iles field is said to have a potential production of 5000 bbl. of oil a day from its present wells, but for the past year has been held at about 600 bbl. a day. The most important test, stratigraphically, ever drilled on the western slope of Colorado is the California Company's No. 1 Raven, NW.-SE. of sec. 30-2N.-102W., which had an initial production of 138 bbl. of oil of 32" gravity, in the Weber formation (Pennsylvanian) between 5750 to 6315 ft. It mas drilled to 7137 ft., probably near the base of the Weber, and then plugged back to 6315 ft. It was shot quite heavily with nitro-glycerin, but failed to respond. While the well can hardly be classified

Jan 1, 1934

By Robert L. Wilson

Computation of reserve tonnages, stripping ratios, and grade of ore has long been a revolting aspect of the young mining engineer's job. Weeks at the desk calculator may turn into months before a single job is completed. Then many additional hours are necessary to check the calculations. During the last decade, computing machines have been widely publicized as instruments which will accomplish fantastic feats. Tales of their magical qualities have overshadowed their most basic characteristics-that of being a labor-saving device. Prior to a discussion of the electronic calculator's use on a mining problem, it may be well to point out that these machines are neither magic nor will they replace the judgment of an experienced engineer. In short, the "mighty morons," as the computors are sometimes called, are excellent labor savers but must be used correctly. They are not a substitute for thinking.

Jan 6, 1961

Graham Macfarlane, Louisville, Ky. (communication to the Secretary*):—In the paper by S. Whinery under the above caption mention is made of the occurrence of Clinton iron-ore in Kentucky and Tennessee. I believe that this is really a ferruginous limestone in what the Tennessee Geological Survey calls the Fernvale formation. In Davidson and Sumner counties, Tennessee, this occurs at about the horizon stated by Mr. Whinery. The maximum thickness of the deposit is from 10 to 12 ft., but it averages between 6 and 8 ft., lying practically horizontal. The Red River Furnace Co., under my direction, opened a mine in the Fernvale " red rock" near Goodlettsville, Tenn., several years ago. When it was first found we assumed it to be Clinton ore, but the absence of the characteristic Clinton fossiliferous structure and other evidence satisfied us that it is really limestone saturated with iron oxide. I think the very low ratio of SiO2 and Al2o3 to iron content as compared with the usual ratio in the Clinton ore is also evidence in favor of its being the Fernvale. The Tennessee Geological Survey states that at outcrops where this ore has been leached it carries about 44 per cent. of iron; under cover, from 20 to 25 per cent. of iron and from 3 to 6 per cent. of silica, the remainder being chiefly calcium carbonate. Its phosphorus content is irregular and generally rather high for a foundry-iron mixture. Since it is more than self-fluxing, we have at times operated with a mixture of brown hematite and red ore with no limestone.

Jan 1, 1913

By Zden[e]k P. Bažant

Due to their heterogeneity, most rocks fracture with a zone of distributed cracking ahead of the fracture front. This makes linear elastic fracture mechanics inapplicable. The present study describes a mathematical model in which the progressive microcracking is taken into account by strain-softening stress-strain relation. In a simpler version of the model, the triaxial strain-softening stress- strain relation is obtained by direct adjustment of the elements of the compliance matrix. This formulation is rigorous only if the principal stress directions do not rotate during fracture formation within the fracture process zone. As a more sophisticated and generally applicable model, the so-called microplane model which is an analogue of the slip theory of plasticity is outlined. Comparison with fracture data for various rocks are given.

Jan 1, 1984

By Robert M. Lewis

Can wet-ground mica be produced from mica schist ores, and if so, would its properties be comparable with products now on the market? This was the problem which prompted the development of a flowsheet for the beneficiation of mica schist. The fine-ground mica industry relies on weathered pegmatites and alaskite ores as sources of raw material. The mica concentrates obtained from these ores are relatively clean and require moderate beneficiation to meet color and bulk-density specifications. Mica obtained from mica schist is iron-stained and decrepitated and requires additional beneficiation to produce a wet-ground mica product. Despite these adversities, there are several advantages to be gained by mining and processing mica schist ores. The mica content of these ores is considerably higher than that of the pegmatites and alaskite ores now being mined, often containing in excess of 40% mica. This higher-grade mica feed should promote a lower mining and milling cost. The mica schist ores with their higher mica content would mean less tailings to handle; however, there would have to be a means for disposing of acid and sulfate wastes. A flowsheet was developed whereby mica could be recovered from mica schist ores and beneficiated in a way that would result in a high-quality end product.' The essential phase of the process involves using reducing reagents to increase the magnetic susceptibility of iron contaminants which then can be removed with a magnetic separator. General Treatment Procedure The mica is floated by either of two methods, an amine float in an acid circuit' or the U.S. Bureau of Mines (USBM) amine-fatty acid float in an alkaline circuit' The flotation mica is ground in a pebble mill to liberate contaminated particles and expose iron-stained surfaces. The concentrate is then conditioned with a reducing reagent and passed through a Frantz Ferrofilter for the removal of magnetic material. The nonmagnetic product is acid-leached to further reduce the iron contamination. The leached material is then ground to product size and checked for specifications. Discussion of Flowsheet and Its Development Flotation: The mica is concentrated by flotation using either of two methods: an amine float in an acid circuit, or the USBM amine-fatty acid float in an alkaline circuit.' The writer does not wish to elaborate on the relative merits of the two flotation procedures; however, after investigating ores from various localities, it was felt that the amine float in an acid circuit was more consistent when using a standard procedure. Iron Reduction and Magnetic Separation: This phase of the flowsheet may be considered the key to the process. It was developed when it became apparent that hot acid leaching had just about reached its maximum effective¬ness for color improvement. S. C. Sun and William Hirsh in "Hydrochloric Acid Leaching of Iron From Pennsylvania Aluminous Clays,"` reported iron extraction for -20-mesh minerals of 82.20% for hematite and only 33.46% for magnetite. The test procedure employs a 19% hydrochloric acid solution, 104°C temperature, and 10% solids. It was felt that magnetic removal of some of the iron contaminants before leaching therefore would be advantageous. Since the iron minerals present as contaminants vary in magnetic susceptibility, it was decided to experiment with reducing reagents as a means of influencing their magnetic properties. Zinc hydrosulfite or sodium hydrosulfite were the reagents used throughout the tests. The procedure developed consists of conditioning the mica concentrate in a closed container at approximately 5% solids with a reducing reagent. Approximately 10.0 lb of zinc hydrosulfite per ton of mica concentrate is used. The ferric iron is reduced to the ferrous state (magnetic) and oxidation is retarded by isolation from the atmosphere in a closed container. After the desired conditioning time has elapsed, the material is passed through a Frantz Ferrofilter where the magnetic particles are retained and discarded as

Jan 1, 1972

The attached tables show that in 1935 production of crude oil in Poland slightly decreased (minus 14,450 tons) and that gas production

Jan 1, 1936

The attached tables show that in 1935 production of crude oil in Poland slightly decreased (minus 14,450 tons) and that gas production

Jan 1, 1936

By H. Sadek

The accompanying table shows the available data pcrtaining to the Hurghada field, the major oil and gas field in Egypt. Operations in Abu Durba, a small field, amounted to almost nothing in 1935.

Jan 1, 1936

By H. Sadek

The accompanying table shows the available data pcrtaining to the Hurghada field, the major oil and gas field in Egypt. Operations in Abu Durba, a small field, amounted to almost nothing in 1935.

Jan 1, 1936

By Charles A. Ashburner

A very limited development has been made of the coal-fields of this Territory. This is to be accounted for by the fact that a number of the coal-fields lack railroad transportation, by the distance of other fields from the consumers (due to restricted settlements), and finally by the poorer quality of a number of coals which have been mined as compared to others which can be economically imported into the Territory. The consumption of coal in Utah during 1886, outside of that used by the railway companies, was: Tons. Utah coal,..........110,000 Wyoming coal,. .....19,000 Colorado coal,........* 4,945 Total,........... 133,945 It is estimated that there are 1100 miles of railroads in the Territory which use coal for fuel. The consumption of these roads for the year is estimated at 100,000 tons, making an aggregate consumption in the Territory of 223,945 tons. The consumption of coal in Salt Lake City duriug the year was as follows: Tone. From Grass Creek mines,.......21,000 " Pleasant Valley Company's mines,.. 12,700 " Utah Central Company's mines,.9,000 " Bock Spring mines,.6,500 " Almy mines .. ., .. .. . 6,000 " Miscellaneous sources,..5,800 Total ,.........60,000

Jan 1, 1888

By H. M. Howe, W. E. C. Eustis

THE processes which form the Subject of this paper have been experimented on in the laboratory of W. E. C. Eustis, but have not passed beyond the experimental stage. The first is the invention of Mr. J. L. Thomson, of Capelton, Quebec, Canada, the others have been invented by the writers. THOMSON'S PROCESS FOR THE EXTRACTION OF NICKEL This consists essentially in first rendering the nickel magnetic, and then separating it from the materials. with which it is mechanically

Jan 1, 1882

By Theron Wasson

During 1936 the state of Michigan produced 11,868,573 bbl. This is approximately 4,000,000 bbl. less than produced in 1935. The principle reason for the decrease in production over the previous year was the rapid decline of the Crystal field, which reached its peak in October 1935. The old producing area—Mt. Pleasant, Porter, Yost-Clark— accounted for over 7,000,000 bbl. during 1936. Crystal produced a total of 2,400,000. Outstanding among the old fields were Vernon and

Jan 1, 1937

By Robert H. Richards

The object of this paper is to enlarge the field of settling velocities treated by me in my former papers, Close Sizing Before Jigging, and Sorting Before Sizing.' There seemed need of work both on coarser and on finer sizes. Messrs. A. Sidney Warren and M. L. Nagel undertook the investigation for the coarser sizes, from 12.85 mm. down to 2.05 mm. diameter. Their work, because of the closer spacing and because of the increased number of observations and consequent stronger averages, called for a revision of the former work. Messrs. G. A. Barnaby and Ralph Hayden undertook this part of the work, from 2.49 mm. down to 0.28 mm., which is near the limit of sifting. Their work covers the ground much more minutely and comprehensively than the former papers. There remained to be covered the portion of the field too fine for investigation with the sieves. This part, covering the range of grains from 0.48 to 0.03 mm., was undertaken by Mr. E. S. Bardwell. For it he used the elutriation method. 11. The First, or Coarsest, Section of the Field. The first desideratum in this investigation was a series of sieves for sizing the sands preparatory to making the tests. It became necessary, therefore, to decide on a sieve-scale for this purpose. A sieve-scale is a series of sieves in which the dimensions of the holes of the successive members form a series increasing by a definite ratio. There are three natural sieve-scales: 1, progressing by doubling the width of the hole for each suc-

Jan 1, 1908

By B. Yarar

Samples of coal from an adit in the Fording River District of British Columbia showed hydrophilic properties between depths of 0-24.5 m (0-80 ft) and was naturally hydrophobic at greater depths. Laboratory experiments indicated that weathered samples (i.e., those mined at 0-24.5 m) could be upgraded by froth flotation at pH32 following slimes removal. The i.e.p. of samples varied regularly between pH = 1.6-4.1, the weathered fractions being at the lower end of the pH scale. These values followed a pattern comparable with the flotation behavior of samples. A patchwise structure for coal surfaces determining the resultant disjoining pressure which in turn determines flotation-non-flotation relationships is postulated.

Jan 1, 1983

By Brian W. Mackenzie

Since mineral economics is often coupled with mining engineering in the solution of mineral industry problems, it is important that the principles of this science be a part of the mining engineer's education. Essentially, mineral economics is the application of economic principles to analysis of the multistage process by which minerals are converted from geologic resources to marketable products. In some instances, it may require only the analysis of case studies from a well- developed economics core. In others, however, it requires special skills, because some aspects of the mineral conversion process--such as mineral occurrence, exploration investment and depletion-have no complete parallel in general economics. The mining engineer has been an important contributor to the analysis of mineral economics problems because of his special knowledge of the mineral industry.

Jan 1, 1971

By F. D. Rosi

IT was recently shown1 that slip bands can be observed in bent germanium crystals after deformation, by means of etch pits along the slip traces. It is the purpose of this note to show how chemical etch pits can also be usedto examine the appear- ance of slip bands in silicon, as well as other deformation markings. A 30 ohm-cm, p-type single crystal bar, 2x1/4x1/8 in., was plastically bent at approximately 1200°C in a vacuum of 1x10-5 mm Hg. The axis of the crystal was coincident with a <III> direction, and the surface normal to the axis of bending was within 4" of a (110) plane. Prior to the deformation, the (110) surface was mechanically polished with

Jan 1, 1958

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Jan 1, 1928