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By E. L. Frueh

AMAX Base Metals Research & Development, Inc. has developed a process for treating copper-nickel mattes to produce copper cathodes and a pure nickel sulfate solution. In this process, the input matte is preleached in a copper sulfate electrolyte bleed solution so as to dissolve nickel from the matte and cement copper from solution. The preleach leaves a substantially pure nickel sulfate solution. The residue from the preleach is roasted to less than about one percent sulfur. A portion of the calcine is leached with sulfuric acid to make a copper sulfate solution for input to the tank house. The residue from this leach and the remaining calcine are smelted to form a bimetallic (copper/nickel.) anode. The anodes are electrolytically refined and copper is preferentially deposited on the cathode while the nickel reports to the electrolyte, A bleed stream is taken from the electrolyte and used in the preleaching of the input matte. This process produces high purity metal streams while consuming less energy and smaller amounts of reagents as compared with other matte processes.

Jan 1, 1983

By Arthur L. Murray

"During recent months much criticism as to the efficiency of mine labor has been heard from various, sections of the country. No doubt much of this criticism has been well founded. The present lack of efficiency and of stability is due primarily to a spirit of restlessness and partial irresponsibility engendered during the transition from war conditions to peace time conditions. This spirit or unrest not only among the laboring classes but in every branch of the human family following a period of intense nervous tension in a nation appears to be a natural sequence of war and beyond the control of man. This condition will gradually disappear, and the majority of our people will again assume their natural order of living, but labor will for a considerable period be sensitive to these influences, whether they be exerted for good or for evil. Employers of labor should take cognizance of this fact and bend every effort towards the development of measures that promote efficiency and permanence of the working force.Labor efficiency depends upon many and varied factors. Some of these factors as applied to mine labor are briefly enumerated in the following paragraph:Selection and Placement of Manpower:In the selection of men the two main considerations are physical ability and adaptability. The laws of mechanics should be applied in the selection of men as in the selection of machinery. If a machine is required for a certain class of work, the type of machine known to be mechanically fit for such work is selected. Likewise, men should be selected with regard to their physical and temperamental fitness for the kind of work expected of them."

Apr 1, 1920

By Warnie Flint

PERSONAL INJURY ACCIDENTS According to statistics compiled by the National Safety Council, US Bureau of Mines, American Medical Association, and other agencies, accidental injuries cause more deaths than all the leading diseases. NO one is immune to an accident. Probably the best way to describe an accident is to say that it is an unexpected happening. The automobile driver is not expecting a terrifying crash, the electrician does not expect to be electrocuted, nor is the coal miner expecting the roof to fall on him. All personal injuries will not result in death. There is a multitude of victims who arc living proof of what accidents can mean to an individual-victims who are blind, paralytic, missing arms, legs, etc. In most instances the earning power of these individuals is gone, and they arc utterly dependent upon family or welfare. For many years there seemed to be an attitude that prevailed in industrial America that accidents were inevitable, and that so many fatalities and injuries should be expected. This, of course, was utter nonsense. Since the birth of such organizations as The National Safety Council, American Society of Safety Engineers, and the US Bureau of Mines, much progress has been made in reducing accidents. The enactment of compensation laws greatly contributed to the progress that has been made. Does this mean that all accidents can be prevented? Unfortunately, it does not. Human psychology indicates that men will work unsafely or perform unsafe acts for the following reasons : 1) Lack of Knowledge or skill. 2) Conflicting motivations, such as: (a) to be more conformable, (b) to save time or effort, (c) to be accepted by a group. 3) Physical or mental condition. Nearly everyone desires his own safety, hut not all individuals are willing to do what they know to do to insure their own safety.

Jan 1, 1981

By Guoxiang Chi

The Cornwallis Fold Belt in the Canadian Arctic Archipelago contains numerous Mississippi Valley-type (MVT) Zn- Pb occurrences and the world-class Polaris deposit. The occurrences are mainly hosted by the dolostone in the Thumb Mountain Formation which spreads over 25000 km2. Success in exploration requires further understanding of the genesis of these occurrences and an assessment of their parentage with the giant Polaris deposit. Syn-sulfide dolomites in regional occurrences share C-O-Sr isotopic characteristics similar with Polaris dolomites, indicating warm basinal brines enriched in 87Sr. The dolomites and sphalerites contain fluid inclusions with ice-melting temperature between ?45° and ?25°C, which is significantly lower than for most MVT districts in the world (?30° and ?10°C). These characteristics indicate that all the Cornwallis occurrences were produced by fluids of the same sources and/or aquifers. The deposit size was largely controlled by the rate and duration of the metal-carrying fluid flow, and by the availability of reduced sulfur at the site of mineralization.

May 1, 2001

By Ivan L. Nichols

Tailings dumps at Mercur, Utah, contain about $7 million worth of gold in 3.5 million tons of mill tailings assaying about 0.07 ounce of gold per ton. Commercial mining and milling at Mercur ceased in 1942. To determine whether improved technology was now available that might permit economic reprocessing of the Mercur dumps, the Bureau of Mines probed for a low-cost method that would be applicable to these tailings. A composite sample prepared for laboratory studies assayed 0.062 ounce gold per ton. About 10 percent of the gold occurred as a water-soluble cyanide. Conventional cyanide leaching dissolved 32 percent of the gold, and hot, strong cyanide solution dissolved 42 percent. Results were not improved by pretreatment with acids, bases, or oxidants. After expensive preroasting, gold recovery by cyanidation was increased to 65 percent. The simple procedures were ineffective, and more effective procedures were too costly for economical processing of Mercur tailings.

Jan 1, 1970

By Zhang Junzhi

This paper relates cross-border mergers and acquisitions (M&A) risk management theory to actual coal enterprises in China. The 3 phases of M&A are preparation, implementation and integration. By using the Analytic Hierarchy Process and fuzzy evaluation methods, we will try to establish a model to assess risks of the cross-border M&A of China?s coal enterprises. We then apply this model to the case of Yankuang Group acquisition of the Felix Company and receive the assessment results. There are significant reasons for quantitative research on risks of cross-border M&A of China?s coal enterprises, such as effective prevention and risk-aversion, and facilitation of cross-border M&As.

Aug 1, 2013

By N. W. Sager, H. W. Mossman

The arrangement and general dimensions of the reverberatory furnaces and waste-heat boilers for the Nos. 2 and 3 smelting units at the McGill plant of the Nevada Consolidated Copper Corporation are shown in Fig. 1. Each of the two reverberatory furnaces has its own set of waste-heat boilers, and before February, 1932, each furnace, when it was in operation, delivered waste-heat gases to its own boilers only. In January, 1933, the idea was suggested of using some of the waste-heat boilers as economizers to operate in conjunction with the waste-heat boilers that were generating steam. The execution of this idea gave rise to the gas-flow scheme depicted in Fig. 1, the advantages of which were obvious, particularly so in view of the fact that for some months prior to the adoption of this scheme the smelting had been confined to No. 2 furnace, with No. 3 furnace and its boilers idle. The waste-heat gases from No. 2 furnace pass through the boilers serving this furnace as steam-generating units, thence through the original exit duct to a point where a bulkhead diverts the gases in a reverse direction through two of the boilers of No. 3 furnace. After the gases have traversed these two boilers, another bulkhead placed in the duct between No. 3 furnace and its boilers causes them to traverse still one more boiler, from which the gas path leads to the stack. In this scheme the last three boilers traversed by the gases, i.e., the boilers behind No. 3 furnace, function as economizers and preheat the feed water for the two steam-generating units directly serving No. 2 furnace. This discussion will give consideration to the results obtained in waste-heat recovery by the scheme shown in Fig. 1, and, further, will compare these results with those obtained before the boilers of No. 3 furnace were set up to act as economizers, but before going into the detail of heat generation, distribution and recovery, will present some additional details of the equipment. All boilers in this waste-heat plant are of the Stirling type. The two behind No. 2 furnace, acting as steam-generating units, of class 13, are 40 tubes wide and rated at 1112 boiler hp., while the three boilers behind No. 3 furnace, acting as economizers, are also of class 13, but 28 tubes

Jan 1, 1934

By George A. Komadina

From its modest beginning in 1957 with one mill grinding section handling 3000 tpd Pima has steadily expanded. In July 1966, work was completed that allowed the concentrator to treat in excess of 18,000 tpd. Almost immediately Pima embarked on another expansion program that will increase plant capacity to 30,000 tpd during the summer of 1967. This repeated expansion has corresponded with the development of additional low-grade ore deposits and with the improved operating economics realized by handling larger masses of material. Early in the life of Pima it was known that a mineralized area was present on the flanks of the high-grade orebody which systematic drilling had shown to be a low-grade copper orebody. Many months of engineering studies revealed that this was sufficient to allow Pima to compete with other large scale, low-grade copper operations in the Southwest.

Jan 11, 1967

"MASSACHUSE'M'S INSTITUTE OF TECHNOLOGYBOLSAITIS, PETERMassachusetts Institute of TechnologyDepartment of Mineral Engineering77 Massachusetts AvenueCambr1dge,MA 02130(614) 253-5069ELLIOIT, JOHN F.Massachusetts Institute of TechnologyDepartment of Mineral Engineering77 Massachusetts AvenueCambridge, MA 02130(617) 253-3305RING, TERRYDepartment of Materials Science and EngineeringMassachu5etts Institute of TechnologyCambridge, MA 02130(6117) 253-4299"

Jan 1, 1988

By Joseph Hays

MORE years ago than I care to admit I conferred the title of "combustion engineer? upon my-self since nobody else would confer it. I thought at the time, and for some, years thereafter, that my field was limited to the precincts where the fuel was being burned, but I found that I could stand in the door of the furnace room and hear distressed heat units calling for help all over the plant. Some of them were over-worked, others were compelled to do useless work, and still others, anxious to render a proper account of themselves, were not permitted to do any sort of work at all and were utterly wasted. The combustion engineer has something to do at that interesting occasion when the heat unit is being born in the furnace, but his responsibility does not end there. He must follow the little fellow throughout the entire period of its hectic existence in the plant and see that it gets a fair chance and a square deal everywhere. I fear that the general impression of the combustion engineer's duties is much as mine was in the beginning; that his job is limited to the implements and processes incident to the specific operation of converting fuel into active, heat energy and of applying it to the boiler, the still, or what-not, with the least possible waste. But is it not true that a heat unit saved in a remote corner of the plant means just as much to the fuel account as another saved at the furnace? And if nobody else is looking after the heat units out on the range why should the combustion engineer spend all of his time hanging around the corral? If combustion engineer is not a broad enough title to cover the man in charge of a general heat unit rescue campaign call him any-thing else you please. The job is all that counts. The name means nothing. A skunk by any other name would smell as bad. The greatest field I have ever found for general "heat rescue" work is the oil refinery. In refining we first put heat into the oil and then take it away from the vapor. The greatest heat losses occur during the cooling operation, but there are losses, many of them preventable, either wholly or partly, at every step of the several processes in oil refining.

Jan 3, 1928

By D. Malhotra, K. Purdy, G. Ramadorai

INTRODUCTION Today, flotation is clearly the dominant mineral concentration method. Since it is a relatively selective process, it is used for almost all sulfide minerals. A recent U. S. Bureau of Mines study indicated that approximately 225 million metric tons of sulfide ore was processed in 67 plants in the United States in 1980 (USBM Staff, 1981). There were over 100 plants processing copper ores in the world (Bassarear, 1985). Sulfide ores containing lead, zinc, copper, molybdenum, precious metals, cobalt, nickel, and iron are generally separated and concentrated by flotation. This chapter briefly reviews the plant practice related to the recovery of the above-mentioned sulfide minerals with emphasis on chemical reagents used for the production of marketable-grade products. PROCESSING OF SULFIDE ORES It is beyond the scope of this chapter to review the milling data for operating plants which have been extensively covered in literature (Tveter and McQuiston, 1962; Rausch and Mariacher, 1970; Weiss, 1985; Crozier, 1979). However, the following generalizations can be made regarding the processing of sulfide ores: 1. The primary grind is targeted to produce as coarse a product as necessary to provide an economic degree of liberation. 2. The concentration process, generally flotation, is designed to produce a concentrate consisting predominantly of valuable minerals and a middling fraction which may require further grinding to produce an optimum release of minerals. 3. The chemical reagent suite (collectors, frothers, etc.) for the separation of sulfide minerals from gangue minerals is generally complex. Total reagents used in the flotation process can be as high as six to eight, as is the case for lead and molybdenite separation from complex sulfide ores. 4. Chemical reagents are generally expensive because of the high selectivity for sulfide minerals. The process flowsheet is dependent on several factors, including ore grade and mineralogical composition. Generic process flowsheets for processing different sulfide ores have been developed for discussion in this chapter. However, there appears to be a consistent relationship between the reagent combination choice and the mineralogical composition of the ore (Tveter and McQuiston, 1962). These are covered in detail in the following sections. LEAD AND ZINC Galena (PbS) and sphalerite (ZnS), which commonly occur together, are the only minerals of lead and zinc, respectively, in most primary deposits. Feed ore grades are typically 1 to 5 percent Pb and 1 to 10 percent Zn. Very often economic quantities of copper and precious metals, silver and gold, also occur with these base metals.

Jan 1, 1986

By L. I. Kiss, A. Larouche, V. Dassylva-Raymond

Control of the quenching capacity of the cooling water is of primary importance for maintaining the quality and recovery rate of ingots produced by direct chill casting. Industrially, this can be done using a cylindrical metallic probe undergoing rapid quenching by direct immersion in a reservoir filled with casting water. Such a test rig originally developed at Alcan Arvida Research and development Centre was modified and used to assess the role of key parameters affecting the boiling heat transfer. During the tests, the probe of the instrument undergoes the effects of different heat transfer mechanisms. An experimental study was performed in order to clarify the details of the probe-water heat transfer during rapid quenching. The heat flux along the surface was determined by mathematical modeling using the measured temperature signals, while the corresponding heat transfer regimes like stable and unstable film boiling, nucleate boiling and natural convection were identified by the analysis of high-speed video recordings. Aluminium

Jan 1, 2006

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

5.1 TECHNOLOGY FOR INJECTING GROUT INTO BOREHOLES The grouting of fractured rock aquifers is carried out in separate stopes' whose size is determined by the hydro¬stratigraphy and the hydrogeologic properties of the rocks. The number of grouting stopes required depends on the number of intervals in the hydrogeological section. Each grouting stope can include one or several aquifers. Com¬bining several water-producing strata into one stope is pos¬sible only when the values of their permeability coefficients are very similar. In order to achieve efficiency, as many aquifers as possible are included in each stope. In practice, the length of a grouting stope in a borehole usually ranges within 10 to 40 m, but occasionally up to 100 m or more. When conducting grouting operations through boreholes drilled from the face of underground workings, the stope's size can be determined by the thick¬ness of each fractured zone (fault) or by the length of the hole if the entire rock is fractured. Injecting grout into separate intervals of fractured rock can be done from the bottom to the top with ascending stopes or from the top to the bottom with descending stopes. Injection from bottom to top is always preferred. Injection also can be accomplished in separate fractured permeable horizons in the section. The STG integrated grouting method is based on the use of packer and injection equipment and technological schemes that facilitate injection in highly isolated fractured aquifers. For this purpose STG has developed a standard series of packers. 5.1.1 INJECTING GROUT THROUGH BOREHOLES DRILLED FROM THE SURFACE Grout can be injected according to one of four techno¬logical schemes depending on the depth of the fractured aquifers, their hydrogeologic properties and the availability of grout injection equipment if the area is remote (Fig. 43). In the first and most preferred technological scheme (1), the grout is injected from the bottom up with ascending stopes. When this scheme is employed, grouting holes are drilled to the entire projected depth based on the field investigations injection tubes is installed above the top of the first hydrostratigraphic unit to be grouted. This scheme al¬lows the grout to be injected only into the permeable stra¬tum or strata isolated by the packer near the bottom of the hole; it precludes the need to clean or redrill the hole before injecting grout into the next overlying stope. This ascending stope scheme is preferred because of its simplicity and ef¬ficiency. It is used in most of the grouting of saturated fractured rock for the purpose of isolating aquifers while excavating deep mine shafts in the USSR. The second technological scheme (II in Fig. 43) injects the grout in sequence from top to bottom with descending stopes. Injection under this scheme is accomplished through the hermetically-sealed mouth of the hole. It is most advis¬able to grout with descending stopes in saturated fractured rock wherein the aquifers constitute thick networks of frac¬tures. Under these conditions it is practically impossible to drill a grout hole to the entire depth of the underground workings due to the large production rate of ground water. In conducting isolation operations with descending stopes, additional work (relative to ascending stopes) is necessary to drill out the grout in order to create and inject the next stope. As a result, the total amount of drilling required to drill out grout can even exceed the volume of drilling of original rock. Consequently it is advisable to use this inefficient scheme only for injecting grout into holes that contain prolific frac¬tured aquifers at depths less than 150 to 200 m. The third and fourth technological schemes (III and IV in Fig. 43) are used in the selective grouting of separate aquifers. For example, these methods would be applied when a grout hole is drilled to its entire depth, wherein grouting of the upper aquifers must be done first so that the sinking of the first shaft can begin prior to deeper grouting. The third technological scheme is used for the selective injection of grout into an aquifer with a thickness of up to 5 m. For this work the DAU-1-2 removable dual packer is installed. It is lowered into the borehole on an injection pipeline. For aquifers with thicknesses of more then 5 m, the selective injection of the grout is carried out according to the fourth technological scheme; a combination of the DAU-2 hydrodynamic plug and the DAU-1 packing device is used. In order to implement this injection scheme, the DAU-2 hydro-dynamic plug is installed at the bottom of the fractured aquifer and the DAU-1 packer is installed at the top of the aquifer.

Jan 1, 1993

By H. Siebel, N. A. D. Parlee

MIZIKAR, Grace, and parlee' studied rates of absorption of oxygen in stagnant liquid silver in a new type of open-ended gas-liquid metal diffusion cell, where the capillary diameters used were 1.5, 2, and 3 mm. They reported that the rates appeared to be controlled by the rate of diffusion of oxygen atoms in liquid silver and they used their data to arrive at the following equation as a reasonably good representation of the diffusivity (D) of oxygen in liquid silver: D = (14.7)10-4 exp (-7100 ± 3200)/RT cm2/sec Since this type of diffusion cell offers a promising method of measuring diffusivities of gas atoms in liquid metals, the senior author of this note and his students are carrying on a critical examination of the method, and are attempting to improve and extend the technique. The research reported briefly here was designed to examine more carefully the earlier conclusion1 that the absorption rate is diffusion-controlled, and to find out whether the diameter of the cell could be greatly increased and thus extend the method to systems where gas solubilities and diffusion rates are much smaller than in the case of oxygen in silver. For the purpose of these experiments, the open-ended capillary cell used by Mizikar, Grace, and Parlee was replaced by a small cylindrical crucible (1 to 1.7 cm in diam) containing pure silver (to a depth of 1.3 to 3 cm) resting in the bottom of a closed-ended vertical quartz tube, with an evacuated quartz filler tube just above the crucible to reduce dead volume. The method of measuring the rate of absorption was otherwise very similar to that of Mizikar, Grace, and Parlee and all the same precautions were taken. A much smaller and shorter tube furnace was used for heating, but simi- lar precautions about temperature gradients were observed. This technique was nothing more than the application of a Sieverts apparatus to the measurement of rates of absorption in small crucibles of stagnant liquid silver. In each run the volume of gas absorbed (V) was plotted against the square root of time (vt) and apparent diffusivities were calculated from the slope of the line, as described by Mizikar, Grace, and parlee.' Care was taken to use only the data obtained during the early part of the total absorption period while the cell functioned as one of infinite depth. The results at 1000°C are summarized in Table I and Fig. 1. The following conclusions may be drawn: 1) Diffusion cells up to 1.7 cm in diam yield, within experimental error, the same values for the diffusivity of oxygen (D) as the capillary cells of 1.5, 2, and 3 mm in diam employed by Mizikar, Grace, and Parlee. Cell diameters as large as 1.7 cm are probably not desirable for the most precise work. Intermediate sizes, perhaps 0.5 cm, will be most practical. 2) All absorptions measured were consistent with a model where the rate is controlled by the diffusion of gas atoms in the metal. The fact that runs at absorption pressures ranging from 0.1 to 1 atm (at any one temperature) give

Jan 1, 1965

By Floyd B. Bowen

Pumping methods are used, almost exclusively, to transport materials in the mining, beneficiation and chemical processing of phosphate rock in the Florida phosphate pebble field. Matrix pumping systems capable of pumping 15,000 g.p.m., transporting 15,000 long tons (dry) per hour, are now in use. They utilize 16-by 48 Yz -in. pumps, driven by 1.250-h.p. motors, discharging into pipelines 20 inches .in diameter .and sometimes several miles in length. As an average, it is necessary to pump 3 tons of matrix to the beneficiation plants, and to dispose of 2 tons of sand tailings and clay as waste, in order to produce 1 ton of shipping-grade rock. The washers and flotation plants, where the clay and phosphate and silica particles are separated, require the movement of large volumes of slurries with densities ranging from 2-3 per cent to 45 per cent solids, by weight. Extensive waste disposal systems require the pumping of dilute clay slurries in quantities of up to 50,000 g.p.m.,

Jan 1, 1963

By A. L. Murray, P. A. Surgeon

The Spring Canyon Mine Rescue Association is a cooperative association supported jointly by five coal-mining companies located in Spring Canyon, Utah. The properties of mining companies the Carbon Fuel Co, Rains , Utah, the Liberty Coal Co. , Latuda, Utah, the Standard Coal Co. , Standardville , Utan, the Spring Canyon Coal Co. , Storrs , Utah, and the Peerless Coal Co. , Peerless , Utah about a mile apart and normally employ a total of 915 men , 733 underground 182 on the surface . and The Association was organized on July 5, 1921 , and Rudolph Clark, fomerly first - aid miner on U. S. Bureau of Mines Rescue Car 11 , was placed in charge. as manager . A board of directors made up of a representative from each of the cooperating companies (usually the mine superintendent ) is the governing body of the Association and the expenses are prorated on a basis of the production of each of the five mines . The Association maintains eight sets of Gibbs rescue apparatus and a motor truck fitted up as a combined rescue truck and ambulance . Additional apparatus are to be purchased . Standardville is the central camp in the canyon and has been made the headquarters of the Association . The apparatus are now kept and the truck housed in a small station, but plans have been prepared for a large station which will be built this summer . This new station will have a large apparatus room , a test chamber, a suitable room. for training, and a garage on the first floor, while above will be the living quarters of the manager . There is a good road through the canyon and the other camps are all within two and one -half miles of Standardville .

May 1, 1922

By J. Clair, H. Mirabel

The determination of the temperature and electrical potential distributicms in the cathodes of aluminum electrolytic cells is difficult. The reascms come from the various nature and the intricate three-dimensional geometry of the materials; besides thermal and electrical phenomena react upon each other. A method of calculation using a computer program applied to a mathematical model, figuring the cathode, is developed. Both of the thermal and electrical phenomena are simultaneously considered. Temperature and electrical potential distributions are finally obtained by successive iterations. Results are compared with measurements on industrial cells. Theoretical and practical applications of these studies are given. Up to the present time the study of the distribution of the temperatures and electric potentials in the electrodes, anode and cathode, of the electrolytic cells used for the production of aluminum was limited to one of the two aspects of the phenomena because of lack of a simultaneous method of calculation. For example, the anode or cathode drop was studied assuming that the temperatures in the iron and carbon are known, a method that obviously is very approximate since iron resistivity, in particular, greatly varies with temperature, which in turn depends on current density. Consequently we tried to find a method of calculation simultaneously taking into account both thermal and electrical phenomena. We proceeded to the study of the cathodes as an initial approach to the problem. Although the cathode and surrounding materials may have varied forms and particularly very heterogeneous characteristics, their structures are simpler than that of the Sijderberg anode and boundary conditions are more easily represented than in the case of anodes even though they are prebaked. The study was in two parts: a) development of a model schematizing the true geometry of a cathode and defining the thermal and electrical boundary conditions, and b) working out a method of calculation of the temperatures and potentials by means of an electronic computer. To facilitate solution of the problem, a model was used initially much simplified in comparison with an actual cathode. This model permitted development of the method of calculation. In a second phase, this model was adjusted to the study of actual cathodes and applied to different types of cells: low- or high-intensity cells, cells set up at ground level or above ground level, cells with cathodes more or less heat-insulated. Simultaneously measurements were made with cells equipped with cathodes of the types studied to compare the values resulting from calculation. The initial model was also used for general studies, in particular for studying the effects of current density in the carbon and iron. The results were confirmed or made precise by the model of the true cathodes. This report successively describes: a) the manner in which the model representing a cathode was worked out, with the simplifications and/or the hypotheses used, b) the method of solution of the problem by means of the electronic computer, and c) an example, stating the extent to which the results obtained may be realistic. Further the possibilities offered by such a study are examined. 1) CATHODE REPRESENTATION The purpose of this phase is to represent the cathode in the form of a so-called "mathematical model", that is with a simplified geometrical configuration, in order to meet the subsequent calculation requirements, while keeping to the true facts as closely as possible. This model further includes the thermal and electric conductivities with regard to temperature for the varied materials composing the cathode, as well as the thermal and electrical conditions at the model boundaries. 1.1) Guiding Principles. For calculating the temperatures and potentials the model is divided by trior-thogonal planes into a network of small elementary parallelepipeds. At the summit of these parallelepipeds' so-called mesh points, the temperatures and potentials are computed. The number of mesh points is of course limited by the capabilities of the computer, since 1) the number of equations to be solved depends on the number of mesh points selected, and 2) the amount of time spent by the computer considerably increases with increasing this number. These conditions call for the following requirements as concerns the model: a) Dimensional requirements: the calculation will be all the more accurate as the network is more closely meshed. Since the number of mesh points is limited in practice, it is necessary to restrict the dimensions of the model. b) Geometrical requirements: so as to make things easier in working out the network, the model must be given a simple geometry. In particular, it will be convenient to have the cathode so constituted that the surfaces limiting the cathode and the surfaces within the cathodes separating the different materials consist of triorthogonal planes. 1.2) Schematization of the Cathodes. After the tech-

Jan 1, 1968

By B. Briggs

Over the past 15 years, the tunneling industry has pushed towards a higher degree of mechanization in nearly every phase of construction. The overall objective of the mechanization was to increase production and the level of safety in tunnel operations. However, the overall complexity of some systems have been a hindrance to a seamless transition to the newer technologies as increased maintenance requirements and re-training of skilled workers has altered the benefit curve for some innovations.

Jan 1, 2010

By Lonie W. M

The rapid development of the Australian steel industry over the past twenty years has greatly increased the demand for coking coal from the collieries owned by the Broken Hill Proprietary Co. Ltd. and Australian Iron & Steel Ltd. This in turn has called for an intensive and continuous programme of colliery expansion and new colliery development, along with the reorganization and modernization of existing collieries.This paper presents a general description of the factors involved and the techniques used in planning modern colliery development for the steel industry.PRELIMINARY GEOLOGICAL INVESTIGATIONSIn any colliery development, preliminary geological investigations require a detailed and practical knowledge of the geology and characteristics of the coal-field as a whole. In the early stages of the investigations, probably the most valuable information is obtained from outside the particular area under review, rather than within it, and unless the geology of the coal-field is understood, the projection of the known information into the unknown area cannot be carried out with certainty.Because development of the coal seams from the outcrops has been an apparently simple matter and not subject to the risks involved in deep mine development, the geology of the New South Wales. coal-fields has not received the attention that major mineral resources warrant.Only the most accessible regions of the coal measures have been generally prospected, while the potential areas remain...

Jan 1, 1957

By William E. Bonini

Gravitational field anomalies have been observed over many igneous intrusives of medium (4000 km2) to small (100 km2) size in outcrop area. These studies give good results because the residual anomalies can be separated from larger scale crustal anomalies and density contrasts usually are present. Although unique solutions are not possible, the analysis of the gravity anomalies can put limits upon the geologic interpretation of such bodies. Three examples in Montana, U. S. A. are discussed: (1) the Boulder Batholith, a late Cretaceous quartz monzonite series of intrusives of 4000 km2 outcrop area; (2) the Little Rocky Mountains, an up-domed area, in which an Eocene porphyry (130 km2) has intruded the Precambrian crystallines and lower Cambrian sediments; and (3) the Crazy Mountains, an Eocene diorite (100 km2), which has intruded the Paleozoic and Mesozoic sediments. In both the Boulder Batholith and the Little Rocky Mountains, intrusive rocks are less dense than the surrounding rocks and negative anomalies are found (40 and 28 mgal, resp.). In the Crazy Mountains, the intrusive is more dense than the surrounding sediments and a sharp positive residual anomaly of 42 mgal is observed. The analyses of the gravity anomalies predict that: (1) the thickness of the Boulder Batholith is on the order of 10 to 15 kms and is concave upward; (2) the Little Rocky Mountain syenite is not a simple laccolith, but is T-shaped and extends in depth to about 16 kms; (3) the Crazy Mountain diorite is not a simple small scale series of stocks, but a large connected body extending in depth 5 kms to the basement (although nothing can be said of it within the basement because there is little density contrast). The analyses of the anomalies place important limits on both the areal and depth extent of the intrusive bodies. Of all possible geophysical techniques, gravity studies offer the most promise in the determination of the shape in depth of intrusive bodies.

Jan 1, 1969