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By R. Sun, R. G. Gillies, R. S. Sanders, J. Schaan

The pipeline transport of paste, backfill or thickened tailings slurries is an important component of the tailings disposal process in many mines around the world. These mixtures contain significant fractions of fine (clay) and coarse (sand) particles, causing them to exhibit non-Newtonian flow behaviour and high frictional pressure gradients. There is often economic incentive to operate these pipelines in the laminar flow regime. Irrefutable evidence has shown that coarse particle settling can occur during the laminar flow of these slurries even when static settling tests show no indication of such behaviour. Previously, a ?rule-of-thumb? minimum frictional pressure gradient of ~1.5 to 2 kPa/m was suggested to ensure effective sand transport, based on the results of tests conducted using viscous Newtonian oils. In this paper, we examine the results of laminar flow tests of non-Newtonian, coarse-particle laden slurries conducted with pipeline loops of 50, 100, 150 and 250 mm in diameter. The results indicate that the ratio of the mean wall shear stress to the mean surficial particle stress is abetter indicator of laminar flow settling tendency than frictional pressure gradient.

Jan 1, 2007

The problem of providing adequate thrust to manually operated rockdrills operating at air pressures of 70 lb/in2g to 80 lb/in2g with the aid of an air-leg is analyzed. It is shown that adequate thrust is provided by an air-leg or the stiff-leg if it is inclined at an angle to the floor of about 25°. However, this requires that the leg react against some support or protuberance, as the friction force between the leg and the floor is inadequate to contain the thrust. Conclusions summarizing optimum thrusts, blow frequencies, penetration rates, drill steel life and bit wear are presented.

By L. A. Vermeulen, C. P. Campbell, D. D. Howat

The production 01material liner than 75 µm in a number of open-circuit mills was investigated. The mils ranged from laboratory rod and ball mils treating a variety 01 ores to large industrial rod mils treating gold and copper ores. It was shown that the dependence on feed rate 01 the production 01 material liner than 751J.1T1 can be accurately described by a simple formula that was derived in previous work. In some 01 the systems reviewed, it proved possible to assess the feed rate 01 ore to the mil at which the rate 01 production 01 material finer than 75 µm can be maximized.

Jan 1, 1991

By A. J. Burger, F. L. D. Cloete

Tests indicated that effective recovery of pyrite from a coarse Witwatersrand quartzitic ore can be accomplished by intensified flotation in an air-sparged hydrocyclone. Air is fed through the porous cylindrical wall of the hydrocyclone into a swirling layer of slury. Hydrophobic particles are attached selectively to small air bubbles, which form a froth and are recovered through the overflow. Hydrophilic particles pass out in the underflow. A spigot in which flow is restricted by an orifice was found to be more successful in preventing blockage by wood chips than an annular opening between a pedestal and the cylinder wall. Pyrite recoveries of 85 to 93 per cent at grades of 35 to 40 per cent sulphur were obtained in the air-sparged hydroclone with residence times of about 1 second. Comparative tests in a batch flotation cell after 320 seconds yielded average recoveries of up to 96 per cent, but with a mean grade of 32,5 per cent sulphur. A high colector dosage of 120 g/t was required in the cyclone, compared with the 40 gft used in conventional operations. An air flowrate of about 150 I/min was adequate at a slury feed rate of 35l/min. Particle sizes between 38 and 106µm yielded the best flotation results.

Jan 1, 1988

By F. F. Roxborough, P. King, E. J. Pedroncelli

This paper describes tests on the performance of a continuous miner in cutting South African coal. Although coal cutting has been investigated extensively overseas, the results have not led to significant changes in machine design because these machines find little difficulty in cutting the softer overseas coals at a fast rate. In general, the results of the tests show that cutting efficiency improves markedly as the depth of cut per revolution of the drum increases, and that the best spacing of picks on the drum is twice the depth of cut. Pick shape is of secon¬dary importance in terms of cutting efficiency, only small differences having been found between the performances of conical- and chisel-shaped tools.

Jan 1, 1981

By K. N. Karparov

The stress state on two slope profiles overlying an inclined surface with layer inclination of 50 and 150 are investigated. It is demonstrated that the induced stress state in an imbedded weak layer, exposed at the base of the slope, forms a zone of induced tensile vertical and horizontal stresses, which can lead to failure. The zone length depends on the slope angle and the angle of the inclined layers. L’état des contraintes sur deux profils en pente en superposition sur une surface inclinée avec une inclinaison de couche de 5o et 15o est étudié. L’étude présente démontre que l’état induit des contraintes dans une couche faible insérée, exposée au bas de la pente, forme une zone de contraintes de traction induites horizontales et verticales, qui peut amener à la rupture. La longueur de la zone dépend de l’angle de la pente et l’angle des couches inclinées. Die Druckvorkommnisse zweier Hangprofile auf einer schrägen Fläche mit einer Schichtneigung von 5º und 15º wurden untersucht. Es zeigte sich, dass die induzierten Druckvorkommnisse in einer eingebetteten schwachen Schicht, die am Hangfuße offen liegt, einen Gürtel induzierter vertikaler und horizontaler Zugkräfte bildet, die zum Zusammenbruch führen können. Die Gürtellänge ist von der Neigung des Hanges und der Neigung der schrägen Schichten abhängig.

Jan 1, 2003

By John Freer

A colloquium on solid-liquid separation was held by The South African Institute of Mining and Metallurgy on 23rd September, 1982, at the State Pavilion Auditorium, Milner Park, Johannesburg, to co-incide with the Electra Mining Exhibition. It was attended by about 150 delegates. Eight papers were presented covering: Geostatistics The School of Earth Sciences of Stanford University, the Centre de Geostatistique ofthe Paris School of Mines, and the Department de Genie Mineral of the Ecole Polytechnique of Montreal are cosponsoring the organization of a 2nd NATO ASI (North Atlantic Treaty Organization Advanced Study Institute), under the name of 'GEOSTAT TAHOE 1983', to be held at South Lake Tahoe, California, on 4th to 17th September, 1983.

Jan 1, 1982

By Donald J. Murdock

Column flotation has been developed over the past ten years as an alternative to conventional flotation. It has been used mainly in the cleaning applications of sulphide flotation, where its ability to wash the froth of entrained gangue and produce a higher-grade product has given it a distinct advantage over other technology. The benefits of column flotation can be summarized as follows: Improved concentrate gradeby 2 to 5 per cent . Significantly lower operating costs . Savings in capital investment . Superior control. Since the initial development of the equipment, a number of design improvements have been developed that now form the basis of the Cominco column-cell design. The purpose of this article is to discuss some of those design innovations, and present some typical industrial results.

Jan 1, 1991

Publications of the 13th CMMI Congress, by J.T. Woodcock (editor-in-chief). Melbourne, Australasian Institute of Mining and Metallurgy, 1986. Set $A90,00. Reviewer: J.D. Austin

Jan 1, 1988

By J. W. Klokow, S. L. Mulder

Early removal of the shaft reef is usually considered necessary on deep level South African gold mines to avoid damaging stress build-up associated with traditional shaft-protection pillars. In the case of the relatively shallow Beatrix Gold Mine it was largely motivated by early access to ore and the consequent earlier return on invested capital. A number of options were considered to protect the shaft from possible damaging stress changes and to minimise deformations in the shaft-reef area. Numerical modelling was used to evaluate the options and to quantify as accurately as possible the likely deformations to be accommodated by the shaft steelwork designs. The option chosen was a combination of strategically placed satellite pillars and yield pillars, and backfill. Following the mining of a small inner cut during the shaft sinking process, full-scale mining is progressing away from the shaft. Suitable instrumentation has been installed to monitor deformations associated with the shaft reef removal. Enlever rapidement le filon du puits est en général considéré nécessaire dans les galeries de fond des mines d’or sud-africaines pour éviter l’accumulation nuisible de contraintes associée aux piliers de protection de puits traditionnels. Dans le cas de la mine d’or Beatrix, relativement peu profonde, l’enlèvement était motivé en grande partie par l’accès rapide au minerai et par conséquent un profit plus rapide sur l’investissement. Un certain nombre d’options furent considérées pour protéger le puits contre les changements de contraintes potentiellement nuisibles, et pour minimiser la déformation dans l’aire puits/filon. La modélisation numérique fut utilisée pour évaluer les options et pour quantifier aussi précisément que possible les déformations probables que la conceptualisation du puits devrait prendre en compte. L’option choisie fut une combinaison de piliers satellites placés à des points stratégiques avec des piliers de protection, et terre de remblayage. Pendant le fonçage de puits une petite coupure intérieure fut exploitée, et maintenant l’exploitation à grande échelle, au-delà du puits, est en cours. Les instruments nécessaires ont été installés pour surveiller les déformations associées à l’enlèvement du filon du puits. Die frühe Entfernung des Riffschachtes wird normalerweise bei südafrikanischen Tiefbaugoldmienen als notwendig erachtet um den zerstörende Druckaufbau zu vermeiden, welcher mit traditionellen Schachtschutzpfeilern verbunden ist. Im Fall der verhältnismäßig flachen Beatrix Goldmine war es hauptsächlich vom frühen Zugang zum Erz und dem konsequenten frühen Rückfluß des investierten Kapitals motiviert. Eine Anzahl an Optionen wurde erachtet um den Schacht vor möglichen zerstörenden Druckänderungen zu schützen und Deformationen im Riffschachtbereich zu minimieren. Um die Optionen zu bewerten und mögliche Deformationen so genau wie nur möglich quantitativ darzustellen die von den Schachtstahlkonstruktionen aufgenommen werden müssen, wurden numerische Modelle verwendet. Die gewählte Option war eine Kombination aus strategisch plazierten exzentrischen Pfeilern und Schutzpfeilern sowie Hinterfüllungen. Nach dem Vortrieb eines kleinen inneren Einbruches während des Abteufens wird der Vollvortrieb vom Schacht weg vorgenommen. Um die Deformationen, die mit der Riffschachtentfernung verbunden sind zu überwachen, müssen geeignete Instrumentenausrüstungen installiert werden.

Jan 1, 2003

By W. Spencer

An examination is made of quality standards in castings produced by the South African foundry industry, and some examples are given of the consequences of poor quality to the user. Corrective measures are suggested.

Jan 1, 1981

A Special General Meeting of The South African Institute of Mining and Metallurgy was held at Kelvin House, Johannesburg, on Wednesday, 20th August, 1986. Mr H.E. James (President) was in the chair and declared the meeting open at 15h45. Background The Chairman explained that the meeting had been called to consider a number of amendments to the SAIMM constitution. The proposed changes had been set out in detail in a document that had been mailed to all members on 4th July, 1986. He then briefly reviewed the background to the proposals, which is outlined in the Preface to the Annual Report (page 357 of this issue). The Chairman added that the Executive Committee of SACPE at its meeting on the 8th August, 1986, had resolved that the proposed amendments to the SAIMM constitution did comply with the requirements of Regulation RI525 dated 17th July, 1981, regarding the recognition by SACPE of a society as a Professional Engineering Institute.

Jan 1, 1986

A very successful banquet was held in the Ballroom of the Carlton Hotel on 7th March, 1986. The Institute thanks the Organizing Committee and the sponsors (listed on this page), without whose generous support the banquet would not have been possible.

Jan 1, 1986

By J. P. Hoffman

The School on the Continuous Casting of Steel, the second school organized by the Technical Programme Committee-Metals Technology of The South African Institute of Mining and Metallurgy (SAIMM), was held at the C SIR Conference Centre from 16th to 20th May, 1988.

Jan 1, 1988

Messrs B. R. Braekman and D. W. Penman have notified some errors in the Addendum that was attached to their paper, 'The Prieska experience: Flotation developments in copper-zinc separation', which was published in the August issue of this Journal (vol. 91, no. 8, pp. 264-265).

Jan 1, 1991

By A. M. P. Henderson

Twelve members of the Witbank/Middelburg Branch, on a technical excursion, were hosted by the Technical Department, Pinelands site, of AECI on 10th February, 1989. The tour opened with some well-presented talks on 'Permitted Emulsion Explosives', and the application of the 'French' test to the development detonators.

Jan 1, 1989

The 97th Annual General Meeting of the The South African Institute of Mining and Metallurgy was held in the Gold Room, Transvaal Automobile Club, 60 5th Street, Lower Houghton, Johannesburg on Wednesday, 10th August, 1994. Obituaries The President announced the passing during the year of the following members:

Jan 1, 1994

By M. P. Mohring

A School on the Total Utilization of Coal Resources, which was organized by the Technical Programme Commitee of The South African Institute of Mining and Metallurgy in conjunction with the South African Coal Processing Society, was held in the Civic Theatre at Witbank from 30th October to 2nd November, 1989.

Jan 1, 1990

Arthur Robert Owen Wiliams died on 18th May, 1989, at the age of 84. ARO, as he was known, was educated at Malvern in England, and graduated from the Royal School of Mines in 1926. He went to South Africa as a Learner Miner with Consolidated Gold Fields at Robinson Deep.

Jan 1, 1989

By D. Visser, P. D. Toens

The development of a continuous recording scintillation counter mounted on a cyclometer by P. D. Toens (Fellow) and D. Visser (Visitor) In order to facilitate ground radiometric surveys the Atomic Energy Board has developed a continuous recording device attached to a scintillation counter which is mounted on a cyclometer. Details concerning the construction are given.