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AFRICAN NATIONAL COMMITTEE ON TUNNELLING In 1970, the South African Institution of Civil Engineers, the South African Institute of Mining and Metallurgy, the South African Institute of Mechanical Engineers, and the Geological Society of South Africa held an international conference on tunnelling, known as Tuncon 1970. SUID-AFRIKAANSE NASIONALE TONNELBOUKOMITEE In 1970 het die Suid-Afrikaanse Instituut van Siviele Ingenieurs, die Suid-Afrikaanse Instituut vir Mynbou en Metallurgie, die Suid-Afrikaanse Instituut van Meganiese Ingenieurs en Die Geologiese Vereniging van Suid-Afrika 'n internasionale konferensie in verband met tonnelbou gehou, wat bekend gestaan het as Tonkon 1970.

Jan 5, 1974

By R. A. L. Black

13.8-1. Introduction. Table 13.8-1 shows that production from the African continent is an important part of total world mineral production. In three of the major particular resources listed, diamonds, gold, and cobalt, African production accounts for considerably more than half the world output. Overall, South Africa including South West Africa plays a dominant role in the mineral economy of Africa, other than in petroleum production. Table 13.81 also shows that much of the production is won by surface mining methods. In addition to the minerals listed in Table 13.8-1, Africa is a main world source for the following minerals: [Beryl 33% of total world production Columbium-tantalum 50%" " 1' Platinum group metals 20% l' " 11 Corundum 55%" " " 11 Vermiculite 30% (' " (6 Uranium oxide 15 0/, of free world production] South Africa and Rhodesia together account for nearly all of this production, except for columbium (niobium) of which Nigeria is the main producer. Thus the importance of southern Africa as a major mineral province can readily be appreciated. The consequences of serious political or military conflict between white-dominated southern Africa and the rest of the continent would be grave indeed, particularly for the West whose financial and economic interest in Africa as a whole is very large. The development of mineral resources in Africa involves the same basic elements as are involved anywhere else in the world: exploration, drilling and sampling, metallurgical assessment, and economic evaluation before, if it is justified, a prospect is brought to the productive stage. The same range of factors controls the economic viability of a project in Africa as elsewhere, of which the most important are:

Jan 1, 1968

By Steve Kral

The Society for Mining, Metallurgy and Exploration’s origins can be traced back to 1871. This was when 22 Pennsylvania coal mining engineers founded the American Institute of Mining Engineers (AIME). The organization’s objective was to “promote the arts and sciences connected with economic production of the useful minerals and metals, and the welfare of those employed in those industries by all lawful means.” Metallurgy and Petroleum were added to the AIME name in 1919 and 1956, respectively. Divisions of AIME were formed throughout the following years in recognition of the increasing trend toward specialization among mineral industry engineers. At the time, SME’s divisions consisted of the Coal Division (1930, now known as the Coal and Energy Division), the Industrial Minerals Division (1935), the Mineral and Metallurgical Processing Division (1948) and the Mining and Exploration Division (1949). The Environmental Division was created in 1997.

Jan 1, 2007

By A Agasty, O Langefeld, MáKellner, E Clausen

The lowering of the pollutant concentration limits at the workplace subjects the mining industry to higher requirements for dilution; this situation is worsened with the current discussions within the European Union (EU) to set new stricter exposure limits for nitrogen oxides in the workplace. This is directly reflected in the performance of the mine ventilation system, which may need to be revised to meet the new standards. The after blast re-entry time, being inversely proportional to the threshold limits, will be higher for a lower limit. This in turn increases the down time for production from the blasted area.Numerical tools have been very useful in predicting the effectiveness of ventilation. This study aims at analysing the dilution time for NOx gases from an ANFO blast in a room and pillar panel. The effect of changing the ventilation on the dilution time is studied next, which helps with the selection of a suitable ventilation system.CITATION:Agasty, A, Clausen, E, Kellner, M and Langefeld, O, 2013. After blast re-entry time for a room and pillar operation, in Proceedings The Australian Mine Ventilation Conference , pp 179-186 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 1, 2013

By David Guy, John Stanbury, Gilbert Tallard

"In 2009, storm surge from Hurricane Sandy inundated the Bay Park Sewage Treatment Plant located at El. +4 to +12 (+1.2 to +3.6 m) in East Rockaway, Long Island, NY. With all systems down, raw sewage water mixed in the floodwaters. A recurrence of such an event being unacceptable, and in view of rising future sea levels, a flood protection project was developed by Nassau County with funding coming in large part from the federally funded Sandy Rescue Fund. Designed by Arcadis/Hazen & Sawyer Engineers J.V., the protection took the form of a perimeter barrier capable of withstanding future storm surge. Due to limitations imposed by property lines and existing facilities, a levee design with three different types of cross section was developed to adapt to each location, adding construction complexity. The Long Island subsurface is characterized by beach sand extending to great depth. The clay required for the core and levee cover therefore had to be brought in from out of state. A thin silty clay layer at El. -23 to -25 (-7.0 to -7.6 m) served as an aquitard. The under-seepage was reduced by a hanging cut-off wall designed as a vibrated beam thin wall and filled with a salt water resistant, low permeability, self-hardening slurry.INTRODUCTIONOn October 29, 2009, Hurricane Sandy hit New York City, with a devastating effect on the region. The low lying Bay Park Sewage Treatment Plant (STP) (Fig. 1) serving Nassau County on Long Island was submerged (Fig. 2). All basements and underground mechanical facilities were flooded (Fig. 3) and millions gallons of effluent were released into the waters of the nearby Hewlett Bay which connects via other small waterways to the Atlantic Ocean."

Jan 1, 2016

A symposium concerning "The Image of the Coal Industry" was presented at 2:00 p.m. in the Conference center and chaired by Charles W. Margolf, RMCMl Program Chairman and Vice President, Western Coal Development, W. R. Grace & Co. MR. McKEEVER: I'd like to do one thing and that's to introduce our Program Chairman, Charlie Margolf, who will be handling this portion of the program. Charlie and I have been acquainted since late 1973. He has worked together with me on several projects at W. R. Grace here in the west; a dear friend and one that I just want to say thanks to again. I think I have a little token of that appreciation here for Charlie. Here you are Charlie. (present given) I turn the command over to you. Mr. Margolf, a native of State College, Pennsylvania, received a Bachelor of Science Degree in Industrial Engineering from Pennsylvania State University in 1950 and a Juris Doctor Degree from University of Pittsburgh School of Law in 1953. His professional experience has beem as an attorney in the Law Department of Reynolds Metals Company, Richmond, Virginia, where he served as legal counsel to the Geological Department the mining subsidiaries of the parent company both foreign and domestic, the Power Department and the Oil and Gas Division. He was closely associated with Reynolds Mining Corporation's project at Lake DeSmet, Wyoming, from its inception in 1954 and became Manager of the Wyoming Division of Reynolds Mining Corporation when it was established in 1966, holding that position until September 1972 when he joined Cameron Engineers, Inc. of Denver, Colorado as Vice President in charge of its coal, water and environmental activities. Mr. Margolf joined W. R. Grace & Co. in January 1974 as Director of Western Coal Operations. Memberships are held in the Virginia Bar Association, the Wyoming Bar Association, the American Bar Association and its Section of Natural Resources Law, the Wyoming Engineering Society, the Colorado Mining Association, the Rocky Mountain Coal Mining Institute which he has served as vice president for Wyoming, the Society of Mining Engineers of the American Institute of Mining, Metallurgical and Petroleum Engineers, the Minerals Information Committee of the Denver Chapter of AIME and the Denver Coal Club which he has served as Chairman of its Board of Directors. He has also been a member of the Montana Coal Council and served as a director, the Wyoming Water Development Association which he has served as a director for industry and as first vice president and the Wyoming Mining Association. He has been reappointed by Governor Lamm to the Governor's Scientific Advisory Council. He was appointed by the Federal Power Commission, Gas Policy Advisory Council, to its Supply- Technical Advisory Task Force - Synthesized Gaseous Hydrocarbon Fuels and served as Vice Chairman of that Task Force. He has been reappointed by the Secretary of the Interior to the Solid Fuels Unit, Department of the Interior, National Defense Executive Reserve. He also serves on the Advisory Council to the Industrial Ecology Institute of the Colorado School of Mines and was recently elected a member of the Board of Directors of ROMCOE (Center for Environmental Problem Solving). Chairman Margolf presented the symposium from the perspective of: ? A local government official - The Honorable Michael Enzi, Mayor of Gillette, Wyoming ? A former state government official - Harris D. Sherman, former Director of the Colorado Department of Natural Resources ? A representative of a national environmental. organization- Robert Golten, Senior Counsel, National Wildlife Federation ? A representative of the printed news media- Ralph Looney, Editor of The Rocky Mountain News in Denver

Jan 1, 1982

By É. Roberge, S. Makni, G. Gagnon, F. Lavoie, A. Faucher

"Feed particle size is an important variable for the primary grinding mill operation. Several commercial vision systems have proven to successfully measure online many types of ores and are used for automatic control. However, due to limitations associated with segmentation algorithms, these systems fail to provide good measurements when the feed is composed of a specific bimodal particle size distribution: very big rocks and a large amount of fine particles. This is typically the case for crushed iron ore. This paper presents a technique to overcome the limitations of existing vision systems by using 3D cameras and appropriate processing methods. It provides online particle size distribution indicators and bulk volume flow rate measurement. It is designed to be very cost-effective, robust, precise, easy to install and to maintain. The 3D system was validated in two iron ore processing plants and the results clearly show that it can be used to optimize primary grinding mill operation where 2D segmentation vision systems fail.INTRODUCTIONFragmentation measurement using digital image processing has successfully been applied in mining and mineral processing operations. Several maintenance and operating applications are already deployed in the industry: Measurement of rock fragmentation after blasting (Maerz, 1999; Palangio, 1999) (Pragyan, 2012) Truck inventory (Palangio, 2005) Monitoring of crusher mantle wear Automatic control of crushers and SAG mills (Bouajila, 2000) (Bartolacci, 2001)Commercial technologies like WipFrag (Maerz, 1999), VisioRock and others proved to be very efficient to precisely measure the particle size distribution of many types of materials. These products are mainly composed of a camera, a lighting system and an image processing system based on a segmentation algorithm. By controlling adequately the lighting conditions and with periodic maintenance on the segmentation algorithm calibration parameters, it is almost always possible to achieve reliable measurements.However, the segmentation algorithm is not adequate when the particle size distribution contains big rocks and a large amount of fine particles. In this case, the area containing the fine particles is accounted as a big rock while big rocks get segmented as multiple smaller sized particles, leading globally to a wrong measurement. This situation prevails for crushed iron ore and coke, among other materials. Figure 1 shows a picture of a material which is typically very difficult to process through segmentation techniques."

Jan 1, 2015

Palabora Mining Company (PMC) processes a multi-component ore body using a circuit consisting of two AG mills in parallel, closed with vibrating double deck screens and hydrocyclones. The bottom screen undersize feeds the hydrocyclones, but the screen oversize products can be treated in a variety of ways. The top deck screen pebbles can be crushed and then combined with the bottom deck oversize and recycled to the AG mill. Alternatively both the top and bottom deck screen oversize can by-pass the recycle crusher and be recycled directly to the mill. A full tap-off is a configuration when both the top and bottom deck screen oversize streams are stockpiled. The other configuration is when the bottom deck screen oversize is recycled to the mill while the top deck screen oversize is stockpiled - termed partial tap-off. This article reports the findings from the surveys performed to evaluate the performance of the PMC auto mill circuit when operated under the four different configurations discussed. Ore characterisation tests were performed to assess the deportment of the key ore components for the different configuration.

Jan 1, 2012

By José Arce

El sistema AG-DAS entró en operaciones en 2015 y su aplicación tiene diversas ventajas sobre el método de polarización inducida convencional. El concepto del sistema fue el uso de múltiples receptores de dos canales, que registran la señal completa con sincronización de tiempo por GPS. La tecnología DAS (sistemas de configuración distribuida, por sus siglas en inglés) brinda mayor confiabilidad en la detección y modelamiento tridimensional de mineralización metálica con geometría compleja a profundidades de hasta más de 800 metros.

May 22, 2019

By N. B. Strydom

The data on heat stroke cases reported during the past five years were examined to determine the influence of age on the incidence of heat stroke. Relating the age distribution of these cases to that of the total number of Bantu mine workers showed clearly that the older men run a significantly higher risk of developing heat stroke than the younger men. Although the number of Bantu over 40 years of age in the industry is less than 10 per cent of the total they nevertheless accounted for 50 per cent of the fatal heat stroke and 25 per cent of the nonfatal heat stroke cases during the period under review. Age must, therefore, be recognised as a causal factor in heat stroke and the worker over 40 years of age should be allocated to work on surface, or in cool areas or to non-strenuous and supervisory tasks in hot areas.

By Gaoming Wang

Outline 1. The Gangdese porphyry Cu-Mo belt 1.1 Regional geological background 1.2 Cu-Mo-bearing porphyries 1.3 Mineralization and alteration 2. Dating methods and results 2.1 Qulong porphyry 2.2 other porphyries 3. Geodynamic implications 4. Conclusions 5. Acknowledgements

May 1, 2004

By Hui Lu

The structural changes in solutionized AA2618 during natural aging and their effects on subsequent artificial aging were investigated by hardness measurements, X-ray diffraction, differential scanning calorimetry and transmission electron microscopy. The changes in lattice parameter and hardness during natural aging indicate that copper-enriched clusters form in the earliest stage, followed by the formation of magnesium-enriched clusters and coppermagnesium co-clusters. Prior natural aging consistently weakened the hardening during subsequent artificial aging at 180, 200 and 230 °C but had no effects on artificial aging at 150 °C. The decreased age hardening was attributed to the reversion of small clusters/zones that formed during prior natural aging. The lattice parameter exhibited erratic changes with increasing artificial aging time, reflecting the complex sequence of the reversion and precipitation.

Jan 1, 2006

By D. B. Swanepoel

Hulamin Rolled Products (Ltd) developed a high Mn and Si containing alloy, EN 4017 as a scrap consuming alloy from the waste generated in producing their range of clad products for brazing of inter alia automotive heat exchangers. The multifaceted composition of this alloy (Al -1.2 wt% Si -1.1 wt% Mn -0.2 wt% Mg-0.26 wt% Cu) suggested that it might display some degree of strengthening via precipitate formation of the Mg2 Si-types. The aging isotherms constructed showed that EN 4017 with 0.19% Mg reached a lower peak strength (YS~210 MPa and UTS~260 MPa)compared to the EN 4017 material with 0.43% Mg (YS~270 MPa and UTS~325 MPa). The higher Mg variant of EN 4017 was comparable with the age-hardenable reference alloy EN 6061. Selected area electron diffraction (SAED) studies proved that the microstructure of age hardened EN 4017 contained a combination of ß', ß" and U2 phase after being aged at 175ºC for 65 h. The general microstructure contained precipitate free zones as well as grain boundary Si films, although these did not lead to significant embrittlement. The role of Mn dispersoids in the fracture mechanism of 4017 is also discussed. The article will compare the behaviour of EN 4017 with that EN6061. Keywords: Age-hardening, dispersoids, magnesium silicide, precipitate free zones

Jan 1, 2009

By Finley A. Campbell

THE Quemont and Horne mines are located at Noranda in north-western Quebec. As shown in Figure 1, the Noranda area lies between the Cadillac-Bouzan fault zone on the south and the Porcupine-Destor fault zone to the north. Both of these major structural lineaments appear to be geometrically, and possibly genetically, related to the Grenville Front. The regional geology has been discussed by Wilson (12), Cooke et al. ( 2), and others. The geology in the Noranda vicinity, as compiled by Dugas and Gilbert ( 3), is shown in Figure 2. The Cadillac-Bouzan fault zone separates the dominantly Temiskaming-type sediments in the south from the Keewatin-type canic rocks to the north. These volcanics, which vary in composition from rhyolite to andesite, form a broad anticlinorium with a general eastward plunge. A succession of dioritic stocks, sills and dikes have been mapped in the area. The principal granitic rock masses include the Powell, Flavrian and Dufault stocks.

Jan 1, 1962

By A. A. Levinson, M. B. Kirkley, J. J. Gurney

"Scientific advances in the past decade have greatly clarified our understanding of certain concepts relating to the age and origin of diamonds. These advances are largely the result of geochemical studies of mineral inclusions in diamonds, made possible by modem analytical techniques which enable the accurate chemical analysis of micro-sized particles of the order of 200 microns in maximum dimension. As a generalization, the inclusions indicate that most diamonds formed from either of two rock types, peridotite and eclogite. Peridotitic diamonds have yielded ages of 3300 million years, whereas eclogitic diamonds areyounger and rangein agefrom approximately 1000to 1600million years. Kimberlite and lamproite, the two rock types usually associated with diamonds, typically are much younger than the diamonds they contain. Thus, it is now dear that kimberlites and lamproites are only the transporting mechanisms which brought diamonds to the surface and are in no way related to the formation of most diamonds. The latest concepts which developed during the past decade regarding the sources of carbon for the crystallization of diamonds from peridotite and eclogite, and the mechanisms of kimberlite and lamproite emplacement, IntroductionThe decade of the 1980s has seen major advances in our understanding of the age, origin and emplacement of diamonds. The information presented herein is applicable to virtually all natural diamonds, excluding diamonds related to meteorite impacts. There is still some question, however, as to the applicability of the new information to industrial grade ""fibrous"" or ""coated"" diamonds, and to microdiamonds (< 1 mm). In addition to drawing upon our own experiences, this review is summarized from a voluminous literature and for those interested in the original sources we recommend the books by Mitchell and Bergman (1991), Ross (1989), Nixon (1987), Mitchell (1986), Glover and Harris (1984) and Dawson (1980), and the review articles by Mitchell (1991), Gurney (1989) and Meyer (1985).are also discussed."

Jan 1, 1992

By E S. Bernard

Toughness testing of fibre reinforced concrete (FRC) at 28 days age is typically undertaken as part of quality control for the many applications where fibres are used in concrete, including shotcrete, tunnel segments, and cast-in-place tunnel linings. The performance achieved at 28 days is usually assumed to be retained with increasing age. However, as the average strength grade of concrete used in most tunnelling applications, including tunnel segments, has steadily increased over the last 20 years, this assumption is becoming increasingly unviable. This is because for some types of fibre the mode of post-crack fibre behaviour depends on the strength of the concrete and can change from a desirable high-energy pull-out mode to a low-energy rupture mode as the strength and age of concrete increases. This paper describes a series of trials performed over two years in which the American Society for Testing and Materials (ASTM) C1609/C1609M beam tests were used to assess the performance of FRC reinforced with two widely used brands of steel and macro-synthetic fibre. The hooked-end steel fibres used for half the beams exhibited a dramatic fall in performance beyond 56 days age as the mode of failure changed from pull-out to rupture. The other fibre did not exhibit a fall in performance with age. This phenomenon highlights the need to quantify performance of FRC at much later ages when long-term performance is required, for example, to resist seismic events or changes in ground stress due to nearby excavations. As an alternative, a reduction factor may be applied to the performance of FRC mixes for which evidence of satisfactory long-term performance is not?available.CITATION:Bernard, E S, 2014. Age-dependent changes in post-cracking performance of fibre-reinforced concrete for tunnel?segments, in Proceedings 15th Australasian Tunnelling Conference 2014, pp 229–236 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 17, 2014

By William Fink

APPROXIMATELY two years ago the authors obtained data that indi-cated that initial precipitation could not be detected by change of lattice parameter in the aluminum-rich aluminum-magnesium alloys. Some of these data were first published in a brief note in MINING AND METAL-LURGY1. Cast specimens were used at that time and they showed initial precipitation relatively sooner than sheet material of the sane composi-tion. For this reason a more thorough investigation has been carried out using a homogenized aluminum-magnesium sheet containing approxi-mately 10 per cent magnesium. Materials.-The aluminum used in the preparation of the aluminum-magnesium alloy was of high purity, containing less than 0.01 per cent each of iron, silicon and copper. The magnesium was high-purity sub-limed magnesium. Preparation of Alloy.-Approximately 4 kg. of the aluminum was melted in a plumbago crucible in an electric furnace and the magnesium was added. The melt was thoroughly stirred with a graphite rod and fluxed with chlorine gas before casting. The alloy was cast in the form of a sheet ingot in a cold iron tilting mold (approximately 200 by 165 by 40 min.) and into small chill-cast, slabs for chemical analysis (75 by 40 by 5 mm.). The chemical analyses were made upon drillings from the analysis slabs. The analytical methods were those described in "Chemical Analysis of Aluminum," published by the Aluminum Company of Amer-ica. The composition of the alloy was found to be: magnesium 10.30, silicon 0.013, iron 0.008 and copper 0.005 per cent.

Jan 1, 1936

By William Fink

ALTHOUGH age-hardening in an aluminum-base alloy containing magnesium was observed by Alfred Wilm1 as early as 1911, it was not until 1919 that a theory of the mechanism of age-hardening was proposed. Merica, Waltenberg and Scott,2 studying the age-hardening character-istics of Duralumin at the National Bureau of Standards, came to the conclusion that age-hardening of this alloy is caused by the precipitation of CuAl2, which is less soluble at the aging temperature than at the solu¬tion heat-treating temperature. It was postulated that the initially precipitated particles were of fine colloidal dimensions but that they gradually grew in size. Maximum hardness was assumed to be attained when the particles reached a critical size. This theory was at first received skeptically, since it was a widely accepted view at that time that the solid solution state should represent the hardest state of an alloy. Shortly thereafter, Jeffries and Archer proposed their well-known "slip interference theory."3 They suggested that age-hardening was accomplished by the precipitated particles acting as keys interfering with slip along crystallographic glide planes. They showed that this mechanical theory led directly to the assumption that maximum harden-ing would be produced by particles of a critical size, which they suggested would have a diameter approximately 10 times that of the aluminum atom. This contribution amplified and explained so rationally the age-hardening theory of Merica, Waltenberg and Scott that wide accept-ance resulted.

Jan 1, 1939

By F. R. Hensel

Up to the present time few attempts have been made to produce hard nonmagnetic materials by heat treatment of austenitic steels. The usual result has been to cause them to pass into the martensitic stage, thus destroying to a great extent the typical austenitic properties, since this involves a transition of a portion of the iron from a face-centered to a body-centered type of atomic arrangement. High-strength nonmagnetic materials such as might be provided by properly hardening austenite are required in the electrical industry for different machine parts. In Europe nonmagnetic retainer rings for restraining the end-turns of the rotor windings in turbo-alternators have been developed as a special application of high-strength austenite. In testing1 a 28,000-kva. three-phase Siemens turbo generator running at 3000 r.p.m. at full load current, the losses in the short-circuit test were 450 kw. for the magnetic ring and 286 kw. for the nonmagnetic, and the difference should be attributable to the magnetic ring. The differences in temperatures during the same test are given in Table 1 and these show the advantage of a nonmagnetic over a magnetic retainer ring.

Jan 1, 1931

By Morris Cohen

WITHIN the past two years, a number of publications have called attention to the double peaks, or stages, that appear in the hardness and strength curves of certain aging alloys. The author has shown the existence of double hardness peaks during the aging of a high-purity silver-copper alloy;1 and on the basis of electrical resistance, microscopic, dilation and lattice-parameter measurements, he concluded that the initial hardness peak occurs prior to precipitation while the secondary hardening is due to precipitation. It was suggested that the general mechanism of age-hardening involves two consecutive processes, the first consisting of nucleus or knot2 formation, and the second consisting of actual precipitation and particle growth. It was further held that the two stages are interdependent, but because of nonuniform precipitation they may overlap each other to an extent that increases as the aging temperature is raised. At high aging temperatures, the effect of the first stage cannot be detected because of the rapid occurrence of precipitation. The general theory of age-hardening recently presented by Dr. M. L. V. Gayler3 is in close agreement with the picture outlined above. With reference to work done on duralumin, copper-beryllium and copper-silver alloys, Dr. Gayler also concluded that age-hardening takes place in two consecutive steps: first, diffusion (in which the solute atoms migrate to certain crystallographic planes), and then precipitation. However, W. L. Fink and D. W. Smith4 have shown that the double aging peaks that appear in the strength curves of high-purity aluminum-copper alloys may be explained without recourse to pre-precipitation phenomena. By means of very careful metallographic technique, Fink and Smith demonstrated that during aging the precipitation takes place at an accelerated rate along the grain boundaries and slip planes as a result of the plastic deformation caused by the drastic quench from the solution heat-treatment temperature. ? The general precipitation occurs at a

Jan 1, 1938