Search Documents

By M. F. G. Bruce

Two backfill systems have been developed on West Driefontein, namely the centrifuge dewatered tailings system and the cyclone-classified tailings system. Modifications to the two systems since the publication of the original paper (Close and Klokow, 1985) are discussed in addition to the results obtained. Considerable experience has been gained from the operation of the centrifuge dewatering units as well as the placement of dewatered tailings in a difficult mine environment. The centrifuge dewatered tailings method has proved successful in the extraction of a highly stressed block of ground at No. 5A Sub-vertical Shaft. The utilization of backfill support in this area made it possible to dispose of a high-grade barrier pillar. This pillar was considered necessary prior to the introduction of backfill support. The recovery of the gold from this pillar made the use of dewatered tailings backfill cost- effective, despite high labour and maintenance costs. Current experience with the bagfilling method of placing cyclone- classified tailings indicates that it is viable and requires considerably less capital investment. Although expensive at present, it is envisaged that costs will decrease once cheaper bags and other forms of stope support are used. The placement of backfill in small-diameter sausage-type bags requires no change in mining cycle and allows the backfill to be placed close to the stope face. Both backfill systems are being expanded but preference is to be given to the cyclone-classified tailings system.

Jan 1, 1988

By C. Holck, J. Yarmuch, J. Read

"Steepening of slopes provides the means to reduce waste extraction and increase ore recovery in open pit mines; however, it may also adversely affect safety by posing a higher risk of slope failure. The implementation of slope monitoring programmes is recommended to manage this risk inherent in steeper slopes. In this paper, the design and evaluation of monitoring campaigns to measure subsurface deformation and groundwater pore pressure in open pit mines is presented. The monitoring programmes were applied to a theoretical case of an open pit mine designed using DeepMine software (BOAMine SpA, 2015). Mine plans were developed based on the initial base case scenario with monitoring programmes considered for four types of monitoring instrumentation: two established technologies, in-place inclinometers (IPIs) and vibrating wire piezometers (VWPs); one emerging technology, the ShapeAccelArray (SAA); and a novel technology under development, the Enhanced Networked Smart Markers (ENSMs). Technical and economic appraisals of the monitoring programmes and sensitivity analysis of the developed mine plans showed that using ENSMs spaced every 4 m had the lowest cost per unit of data gathered. IntroductionSeveral open pit mines have already exceeded their design life and, as they become deeper and reach depths over 1000 m, they face higher rock stress levels and tensile deformations (Stacey and Xianbin, 2004; Stacey et al., 2003). The more complex the conditions in modern open pit mines, the more difficult it is to achieve long-lasting, stable pit slopes and to meet the mine’s economic needs: maximize financial returns, minimize risks to operational safety, achieve optimal ore recovery, and minimize waste extraction (Stacey, 2009). Steepening of slopes provides the means to reduce waste extraction and increase ore recovery (Stacey, 2009; Calderon and Tapia, 2006; Bye and Bell, 2001; Jefferies, Lorig, and Alvarez, 2008); however, it may adversely affect operational safety, as steeper slopes are less stable than shallow slopes (Steffen et al., 2008; Mphathiwa and Cawood, 2014)."

Nov 1, 2018

By B. Mienie, J. F. Morrison, C. H. Wyndham, M. J. Martinson, N. B. Strydom

Contribution to discussion M. J. Martinson (Associate Member)*: Application of the simple selection test mentioned in the penultimate paragraph of the paper (reference to a more detailed description of the test would not have been inappropriate) should assist South African mining engineers to make more efficient and possibly more humane use of available labour. The authors mention that the test 'is in use in the gold mining industry', and it would be interesting to know the extent of this usage in terms either of number of mines or as a percentage of the total number of labourers employed on 'heavy' tasks. The paper would have been of greater interest had the authors attempted to relate their findings to the statistics of labour usage in gold mines, members of the Chamber, and to the 'heavy' tasks in particular. On this the authors confine themselves in their Introduction to the somewhat ambiguous statement that 'A relatively high proportion of the 360,000 Bantu mine labourers are employed underground on manual tasks'. To appreciate the practical significance of the authors' work one needs a detailed breakdown of the underground labour force by occupations, together with estimates of quantities such as: (a) total stope and development tonnages moved manually per shift: by shovelling by shovel/tram by tramming together with distances and any other relevant data; (b) theoretical energy expenditures required to accomplish (a); (c) actual energy expenditures required to a accomplish (a); (d) energy theoretically available to accomplish (a) based on 50 per cent of the total maximum oxygen intakes of the labour force allocated to these tasks. Analyses of this sort on an industry basis might demarcate the more promising areas for detailed investigation. Stress is often laid on the need for increased mechanisation to increase stope productivity, but it may be questioned if enough is known about the characteristics, performance and potential of our underground labour force to warrant blind acceptance of stope mechanization as the industry's panacea. Provided that health and safety are not compromised, the ultimate yardstick for assessing any form of stoping is profitability; obviously the industry must investigate very thoroughly any form of mechanization which might reasonably be expected to increase profitability, but it should also be remembered that a radical overhaul of existing systems-which have after all evolved by trial and error over the past 75

Jan 11, 1968

By D. K. Chibwe, P. Taskinen

"Typical operation of industrial Peirce-Smith converters (PSCs) used in copper smelting results in several common phenomena such as excessive splashing, slopping, tuyere blockage, and low converter campaign life due to high tuyere line refractory erosion. These phenomena give rise to an inefficient operation from both a process and an energy perspective.This investigation presents numerical and physical models of flow patterns, mixing, solid-liquid mass transfer, and slag-matte phase distribution in a slice model of an industrial PSC. For physical simulations, a 0.2-scale cold model was developed. Water, kerosene, air, and sintered benzoic acid compacts were used to simulate matte, slag, injected gas, and solid additions into the PSC. The two- and three-dimensional numerical simulations of the three-phase system were carried out using volume of fluid (VOF) and realizable k- e (RKE) turbulence models to account for the multiphase and turbulence nature of the flow respectively. These models were implemented using the commercial computational fluid dynamics numerical code FLUENT.Both numerical and physical simulations were able to predict, in agreement, the mixing and dispersion characteristics of the system in relation to various blowing conditions employed in the investigation. Measurement of mass transfer characteristics conclusively indicated that fluid flow in the PSC is stratified. Both blowing configuration and volume of slag in the converters were found to have significant effects on mixing propagation, wave formation, and splashing.The splashing and wave motion in these converters are known to cause losses of metal/matte and potential production time due to the requirement for intermittent cleaning of the converter mouth, resulting in reduced process throughput. To prevent these losses and hence to increase process efficiency, we propose a combined blowing configuration using top lance and lateral nozzles. The numerical simulations were conducted on combined, as well as lateral, blowing conditions. In comparison, the recent results of the combined blowing concept were found to be encouraging."

Jan 1, 2014

By S. Kauchali

"Underground coal gasification (UCG) is recognized as an efficient mining technique capable of chemically converting the coal from deep coal seams into synthesis gas. Depending on the main constituents of the synthesis gas, chemicals, electricity, or heat can be produced at the surface. This paper provides a high-level graphical method to assist practitioners in developing preliminary gasification processes and experimental programmes prior to detailed designs or field trials. The graphical method identifies theoretical limits of operation for sensible gasification within a thermally balanced region, based primarily on the basic coal chemistry. The analyses of the theoretical outputs are compared to actual field trials from sites in the USA and Australia, with very favourable results. A South African coal is studied to determine the possible synthesis gas outputs achievable using various UCG techniques: controlled retractable injection point (CRIP) and linked vertical wells (LVW). For CRIP techniques, an important result suggests that pyrolysis, and subsequent char production, are important intermediate phenomena allowing for increased thermal efficiencies of UCG. The conclusion is that South African coals need to be studied for pyrolysis-char behaviour as part of any future UCG programme. The results also suggest that UCG with CRIP would be a preferred technology choice for Bosjesspruit coal where pyrolysis dynamics are important. Lastly, the use of CO2 as oxidant in the gasification process is shown to produce syngas with significant higher heating value. Introduction and literature surveyCoal is a commonly utilized fossil fuel, providing over 40% of global electricity demand and about 90% of South Africa’s primary energy needs. However, less than 20% of the known world resources are suitable for possible extraction using conventional surface and underground mining techniques (Andrianopolous,, Korre, and Durucan, 2015). Underground coal gasification (UCG) has the potential to recover the energy stored in coal in an environmentally responsible manner by exploiting seams that are deemed unmineable by traditional methods. The UCG process, if successfully developed, can increase coal reserves substantially. For example, in the Limpopo region of South Africa alone, the estimated potential for UCG gas, based on existing geological records, is over 400 trillion cubic feet (TCF) natural gas equivalent – this is about a hundred times more gas than the existing 4-TCF Pande-Temane natural gas field reserve in Mozambique (de Pontes, Mocumbi, and Sangweni, 2014)."

Oct 1, 2018

By E. Molobi

"Studs are rods threaded on both ends and are used as mechanical fasteners for two or more components. Stud finds usage in industries such as automotive, construction and aviation. The advantage of studs is that they allow for disassembly of components during maintenance. Studs are continuously subjected to both tensile and shear stresses, depending on the application, therefore they should be manufactured from suitable materials that are capable of withstanding all these external forces. Studs are sometimes manufactured from re-sulphurized steel due to its improved machinability; however, there is a certain limit on the amount of sulphur, above which failure may occur. Premature failure of studs has been a common problem, but failed studs are commonly replaced with new ones without conducting failure investigations. The present work investigates the premature failure of two re-sulphurized steel studs used on a rocker arm assembly and recommends alternative materials. The investigation was carried out by conducting visual examination, microstructural analysis, hardness measurements, chemical analysis and a detailed scanning electron microscopy (SEM) investigation on the fracture surface.IntroductionTwo rocker arm studs used on a 16-cylinder diesel locomotive engine failed prematurely after being in service for less than 5 months. The rocker arm studs had a life-cycle of 5 years. The studs were manufactured from resulphurized steel. The paper aims to establish whether re-sulphurized steel is applicable for the manufacture of studs in the automotive industry.BackgroundLocomotives are classified as either electric or fuel-powered. Diesel locomotives are an example of fuel-powered locomotives. This type of locomotive uses a diesel engine as a means for propulsion. An engine converts chemical energy into mechanical energy required for traction. In an internal combustion engine a rocker arm is an oscillating lever that conveys radial movement from the cam lobe into linear movement to open and close poppet valves of cylinders (Husain and Sheikh, 2013). The rocker arms are secured on to the cylinder head by rocker arm studs."

Jan 1, 2016

It is well understood that to develop wagon wheels with higher abrasion resistance, fracture toughness, and fatigue resistance, steels with lower amounts of inclusions need to be used. Clean steels are produced with technologies that minimize the amount of inclusions in the microstructure. The demand for cleaner steels is high, and lowering of non-metallic oxide inclusions and controlling their morphology, composition, and size distribution is vital. Reduction of residual impurity elements such as sulphur, phosphorus, hydrogen, nitrogen, and trace elements is essential in the production of cleaner steel. Material cleanliness is vital for fatigue endurance, since oxide inclusions may act as stress concentrators and initiation points for fatigue cracks. To better understand the relationship between the cleanliness and toughness of the 34-inch cast wagon wheels, two samples of different levels of cleanliness were supplied for investigation. This paper presents the results of metallurgical analysis using scanning electron microscopy(SEM), energy-dispersive spectrometry (EDS), and mechanical tests for the pearlitic high-performance cast rail wagon wheel (identified as Class B) that are currently being used. The Charpy V-notch impact test results for the three samples from wagon wheels were compared. With the aid of SEM/EDS analysis system, non-metallic inclusions in these steels were detected, and it was possible to determine the position, size, shape, and composition of each particle. Alumina and manganese sulphide inclusions could be identified as the dominant inclusion types in the investigated samples. Fracture surface analysis of the Charpy specimen with high inclusions indicated that transgranular cleavage was the predominant fracture mode. Fractography of fracture surfaces of Charpy impact test samples also showed improvement of toughness properties on the clean sample.

Jan 1, 2013

By S. K. Murphy

A partial shaft pillar extraction project was embarked on at a mine in the West Wits mining region in South Africa. Prior to the extraction, a rock engineering assessment was conducted with the main objective being to establish which areas of the shaft pillar could be extracted without unduly affecting the stability of major infrastructure within the shaft pillar. Standard numerical modelling methods were used to conduct this assessment and several areas were identified for extraction. However, during the extraction process, it was found that the infrastructure was affected more than was originally predicted by linear elastic modelling. In addition to this, several large events resulted in far more large aftershocks than would normally be predicted. In order to gain an understanding of this phenomenon, seismic data was integrated with numerical modelling as follows: > The seismic data in the form of displacements was integrated in 3D space within the model to assess the effect of static stress changes associated with seismic activity > Data from large events was integrated onto specific structures, where displacements associated with large events were integrated onto the plane of structure in question. This paper describes the methodology and results obtained from each of the above processes and include insights into the mining process that were previously unfathomable using standard linear elastic numerical modelling. The way forward for this rock engineering assessment of partial shaft pillar extraction is also discussed.

Jan 1, 2012

This International Mine-Surveying Conference will take place in Budapest (Hungary) from 5 to 14 June, 1972. Detailed information can be obtained from the Mine-Surveying Working Committee of the Hungarian Mining and Metallurgical Society. Write: OMBKE Bányaméröi Munkabizottsag Budapest, V., Szabadsag ter 17, Hungary. SYMPOSIUM ON NICKEL The 'Gesellschaft Deutscher Metallhiitten-und Berglaute' is holding a Symposium on nickel on 24-25 September, 1970 at Wiesbaden, on the occasion of the G.D.M.B. Annual Meeting. Some 24 papers will be presented by metallurgists from many important companies around the world. Information may be obtained from The Secretary, G.D.M.B., Postfach 210, 03392 Clausthal-Zellerfeld, German Federal Republic. VISIT TO THE COUNCIL FOR SCIENTIFIC AND INDUSTRIAL RESEARCH On 23rd June, 1970, members of the Institute visited the C.S.I.R. in Pretoria. More members had booked for this tour but the current flu epidemic caused cancellations which was unfortunate. The visit was organised with military precision, which prevented detailed discussion of any particular subject, but provided a bird's eye view of a large number of interesting projects. The visit was packed with interest for all and those requiring further information were invited to contact the relevant divisions afterwards. Or Denkhaus welcomed the delegates and stressed the importance of integrating research efforts with industry's requirements. An excellent colour and sound film was shown which depicted the work of the Rock Mechanics division. This showed very clearly methods used for preparing rock samples and demonstrated the machines and instruments for the various tests. It made one realise the extent to which this research has been integrated with the actual mining situation. The fullscale experiments underground showed the failure of pillars under applied loads and were very interesting. This is undoubtedly a film which all mining people should see. After the film the rock mechanics laboratories were visited where the actual machines were seen and described. We then visited the metal and strength mechanics sections where the metallurgists were able to see some interesting experiments and tests. We also visited the Aeronautics Research group where a large 1 000 hp wind tunnel was inspected. We were told enough about this to realise something of the complexities involved in the design and operation of a closed circuit tunnel of this type. The tunnel is used for tests on models which are necessary for the design and modification of aircraft. After a very excellent lunch at the C.S.I.R. recreation centre, the delegates attended two lectures-one by Mr. Mandersloot of the Chemical Engineering group, who outlined the varied functions of this group and told us something of their work. Of particular interest was the research into the suitability of various South African manganese ores for dry cell batteries. Work on the thickener settlement studies interested the metallurgists. The second lecture was given by Mr Donaldson of the National Building Research Institute. This Institute has about ten divisions each of which covers a particular aspect of building research. The work of the soil mechanics division was described in detail and illustrated by coloured slides. This was particularly interesting and demonstrated clearly how building failures result from lack of attention to detail of construction where unstable soil conditions exist. Cracks in walls of compound blocks brought the subject home forcibly to the mining delegates. This division has also caried out important work on sinkholes and sUmes dams and produced some positive results. Altogether the visit was most interesting and enjoyable. It was made more worthwhile because the emphasis was on the work being carried out and not on just seeing the laboratories. The Institute is greatly indebted to the C.S.I.R. and its staff for the very excellent arrangements made.

By P. C. Pistorius, M. P. Maphutha, J. D. Steenkamp

Advanced high-strength steels (AHSS) are sophisticated materials being developed by the steel industry to mitigate challenges related to the performance of motor vehicles. To meet the requirements of AHSS, the ferromanganese alloys (FeMn) utilized in the production of the steel are required to contain acceptable levels of unwanted impurities, i.e. P, S, N, H, and C. The focus of the current study was to investigate dephosphorization of ferromanganese to produce a low-P alloy that could be effectively utilized in the production of AHSS. The study involved conducting laboratory-scale testwork to study the efficiency of CaO-based slag systems to dephosphorize FeMn alloys. The addition of Na2O, CaF2, and BaO to MnO-CaO-SiO2 slag was considered. The test work was carried out in a 25 kW induction furnace at temperatures of 1350°C, 1400°C, and 1450°C. The P partition coefficient (Lp) remained small at <1, which is an indication that dephosphorization had not been achieved. The baseline slag, comprising 40%CaO-40%SiO2-20%MnO, reported higher Lp values. Addition of Na2O and CaF2 did not show any further benefit. Substituting half of the CaO by BaO, resulted in similar Lp values to those of the baseline slag under conditions of 1350°C and 1450°C at 30 minutes. In summary, based on the Lp values obtained, the conditions investigated with the CaO-based slags appeared to have been unfavourable for dephosphorization of FeMn alloys, as most of this impurity element remained in the alloy.

Sep 1, 2021

A Colloquium and General Meeting were held on 17th March 1971, the theme being &apos;Future trends in steel production&apos;. Mr V. C. Robinson (President) was in the Chair. The Colloquium was attended by 121 delegates and was opened by the President at 10 a.m. OBITUARIES THE PRESIDENT: &apos;It is my sad duty to announce the death of the following: F. O. Read, Fellow, who joined the Institute in 1957 and passed away on 13th January, 1971. P. G. M. May, Member, who joined the Institute in 1969 and passed away on 10th August, 1970. R. J. J. Rademeyer, Life Fellow, who joined the Institute in 1942 and passed away on 23rd September, 1970. As a mark of respect to the memory of the deceased and in sympathy with the bereaved I would ask you all to rise and observe a few moments silence. CONFIRMATION OF MINUTES THE PRESIDENT: &apos;May we confirm the minutes of the monthly general meeting held on 21st October and 18th November, 1970, as published in the Journal&apos;. Agreed. MEMBERSHIP THE PRESIDENT: &apos;I have much pleasure in announcing that the names of the undermentioned candidates, having been published in accordance with ByLaw 5.2.2, Council has elected them to membership of the Institute in the following grades: FELLOWS: Romain August Lathioor, Paolo Piga, Renato Ribacchi, Willem Frederick Jacobus Smith, Matthew Churchill, Thomas Anthony James Braithwaite, Hugh Patrick Hart, Eleanor Innocentius Muller, David Alton Smith. MEMBERS: Douglas Adendorff, Petrus Jacob du Plooy, James Valentine Grant Middleton, Karl Anders Ullerstam, Josephus Theodorus Johannes van Wyk, Frank Douglas Abbott. GRADUATES: David Mervyn Gilbart-Smith, John Philip Wilcocks Bennie, Hendrik Theunis Burger, Johann Wilhelm Coetzee, Johannes Stephanus StOols, Leon van Tonder, Brian George Harvey, John Kennedy McLean. ASSOCIATES Richard Cyril Lee Stoyell, Terrence Brian Gouws, Alister Rodney Frederick MacDonald. STUDENTS: Andries Groenewald, Christiaan Johannes Hattingh, William Hendrik Hofmeyr, Stanley Thomas Vincent. I welcome the new members to the Institute and congratulate them on their election. COLLOQUIUM The President welcomed everyone present and mentioned that this was the first of the Colloquia which are to replace the Institute&apos;s monthly meetings. He stressed that discussion at Colloquia would be completely informal and would not be recorded unless the contributor requested publication. In conclusion, he thanked the organising committee, the authors and the contributors, and introduced the author of the first paper. The following papers were presented:- &apos;The future development of the Iron and Steel Industry&apos; by J. P. Coetzee (Published in the Journal March 1971). Among those who contributed to the paper were Dr Bleloch, Dr K. Gebhard, Dr Way and Professor Müller. The main point made by Dr Bleloch related to the reserves of coking coal and of coal for power generation this in country and he deduced that in South Africa we are critically short of coking coal. On the basis that 4 million tons per year of coking coal are consumed for our present steel production, over 16 million tons would be required to meet the anticipated expansion in steel output by A.D. 2000. This must be set against the grim forecast made by the Coal Advisory Board in 1967 that our national reserves of coking coal will be exhausted before A.D. 2000. This gives tremendous significance to the development work presently being carried out by Iscor on alternative methods for coke production. On the other hand the blast furnace may have to be replaced by an alternative process for the reduction of iron ores, e.g., the use of rotary kilns followed by electric arc smelting. Dr Bleloch also expressed grave forebodings about the reserves of bituminous coal, pointing out that with present methods of mining the recoverable coal in any given reserve is in general only 50 per cent of that reserve. He stated that in the past seventy years great quantities of coal have been forever placed beyond the reach of mining by being undermined by extraction of lower seams or lost by being burned. A final point made by Dr Bleloch was the fast rise in the capital investment in a fully integrated steel plant, the figure having risen in the past decade from just over R200 to R350 per ton of finished steel per annum. Dr Gebhard spoke of the direct reduction processes for iron making pointing out the difficulties of securing a high percentage of reduction and the relatively high cost of smelting in electric arc furnaces. As an alternative he suggested briquetting the high carbon sponge iron

The November General Meeting of the Institute was held in Kelvin House, Johannesburg, on Wednesday, 18th November, 1970, at 4.00 p.m. V. C. Robinson (President) was in the Chair. There were also present 30 Fellows, including J. K. E. Douglas, R. C. J. Goode, Dr J. P. Hugo, Prof J. de V. Lambrechts, D. G. Maxwell, Prof R. P. Plewman, Dr M. D. G. Salamon, P. W. J. van Rensburg, L. W. P. van den Bosch (Council Members), R. E. Burnton, S. Craib, D. de Villiers Oxford, J. C. Fritz, G. W. Gray, G. H. Henderson, S. D. Hill, C. H. Kruger, B. Leach, C. S. MacPhail, D. J. Molony, W. G. Fyne Mercier, R. A. Scott, M. v. R. Steyn, I. E. van Aswegan, A. D. Vos, J. M. Vosloo and N. Zolezzi. Four Members, including I. G. Evans, R. W. Shearer, W. Wilson. One Associate: P. M. C. Wilson. Four Students: H. G. Albertyn, J. T. Davies, P. G. Henderson and P. J. Pretorius. Fourteen Visitors, including S. R. Barker, F. H. Deist, Dr de Jager, L. F. Duvel, P. du P. Kruger, B. D. Maree, B. R. Meyer, R. Redmond, J. Rietief, A. W. S. Schumann, Mrs A. W. S. Schumann, T. S. Stoffberg, C. A. Visser and R. van der Wait. Secretary, D. C. Visser. Total present 55. The President: "Gentlemen, I would like to welcome all members of the Institute who are present, and visitors, and I would like specially to welcome any members of the Suid-Afrikaanse Akademie who are present this afternoon." OBITUARIES The President: "Before starting on the agenda the first item, of course, is unfortunately obituaries and it is my sad duty to announce the death of the following: I would like to start with a person who is not actually a member of the Institute but who, in his capacity as President of the Chamber of Mines, was Honorary President of this Institute three times and I refer, of course, to Mr Herman Calderwood Koch who passed away last Saturday. Then I would refer to Richard Beaumont Tasker, Life Fellow, who joined this Institute in 1932, and who died on the 22nd of October, 1970. Then, lastly, Mr Jean Francois du Plessis, a student, who joined the Institute on the 19th June, 1968, and passed away on the 11th of November, 1970, as the result of an accident. Mr du Plessis was to have received a Student Prize today for his paper entitled, Displacements and stresses in the vicinity of a horizontal long-wall&apos;. We were all most upset to learn of his death last week, and we are now going to make arrangements to hand his prize to his widow on a suitable special occasion. As a mark of respect to the memory of the deceased, and in sympathy with the bereaved, I would ask you all to stand and observe a few moments&apos; silence. Thank you." CONFIRMATION OF MINUTES The President: "May we confirm the minutes of the monthly general meeting which was held on 16th September, 1970, as published in the November Journal?" Agreed. MEMBERSHIP The President: "I have much pleasure in announcing that the names of the undermentioned candidates having been published in accordance with By-Law 5.2.2, Council has elected them to membership of the Institute in the following grades: Fellow: Ronald White Ballantine. Members: Jan Johannes Hertzog Viljoen, Agge Petrus Rutgerus van der Meer, Peter Anthony Reynolds, Ernest Esdaile Leyde Hans Lutz Klingmann, Ronald Archer.&apos; Graduates: Trevor Stanley Schultz, Thomas Cochrane Meiklejohn, Leslie Harold Heyman, Dennis William Bosch, Sydney Stuart Absolom. Associates:Roderick James.Vermaak, Theodorus Daniel van Wyk, Michael Osmond Savignac Stedman, Leslie Owen Raymer, Bryan Arthur McKay, Leon Ellis Finlay Leask, Dudley Graham Lovedren Hall, John Arthur Gibbon, Richard Reginald de Villiers, Carel Frederik Boshoff. Students: Frederik Wilhelm Christian Coetzer, Phillippus Johannes de Wit, Jan van der Merwe Grimes, Davood Khareghani, Jan Wolvaardt Oberholzer, Johannes Lodewikus Pretorius Pieter Jacobus Strobos, Herbert Gerald Waldeck.&apos; MEMBERS TRANSFERRED TO A HIGHER GRADE From Associate to Fellow: Howard Mitchell Wells. From Associate to Member: Ernest John Dominy. "I welcome the newly elected members to the Institute and congratulate the members who have been transferred to a higher grade." AWARDS The President: "It is with very great pleasure that I can announce that Council has agreed to make the following awards for papers presented to the Institute during the year ended July, 1970. Gold Medals to Prof Plewman and W. D. Ortlepp for their paper entitled &apos;The development and application of a digital computer method for the solution of strata control problems&apos; written jointly with F. H. Deist (Visitor) and presented in September, 1969. A Silver Medal to Dr Finkelstein for his paper entitled &apos;The Influence of sulphydryl and cationic flotation reagents on cyanidation of native gold&apos; written jointly with Dr K. G. Ashurst (Visitor), and presented in June 1969 at the Symposium on the Recovery of Pyrite. &apos; May I congratulate these gentlemen on the high honour they have won with their papers. As new medals are in the process of being designed the actual awards will be made at a later date to be announced to members.

By Wilson. D.

The Vaal Triangle Branch of The South African Institute of Mining and Metallurgy was established on 20th November, 1986, at a meeting enthusiastically supported by local members. In attendance were special guests Dr H. Wagner (President, SAIMM) and Dr O.K. H. Stefen (Junior Vice-President, SAIMM).

Jan 1, 1987

By J. H. Viljoen, A. Heyns, J. F. Morrison, C. H. Wyndham, N. B. Strydom

Discussion M. J. Martinson* (Associate Member): This is another interesting paper in the series which the Human Sciences Laboratory is publishing on the physiological cost of the more strenuous manual tasks performed underground. As a mining engineer-albeit presently an academic one -this contributor is more concerned with the practical significance of the study in the field of stope cleaning than with physiological niceties, but before discussing some of the practical issues raised by the paper perhaps the authors would care to reply to lay comment on three physiological matters. Firstly, in two places the authors make statements to the effect that the maximum oxygen intake of &apos;average&apos; (sic) Bantu mine workers is 3.0 l/min. What do the authors mean by &apos;average&apos;? Maximum oxygen intake in the individual is probably some function of inter alia age, physical fitness, state of health, ambient partial pressure of oxygen, diurnal and/or seasonal changes in metabolism, and possibly cumulative exposure to dust and other occupational contaminants. Since maximum oxygen intake is apparently such an important quality in manual labourers we ought to have a clear picture of its distribution in the entire labour force, and also know precisely how the individual&apos;s quantum is affected by factors such as those mentioned above. Secondly, arising out of the same statements and ignoring the reservation implicit in the previous paragraph, is it correct to say that the &apos;average&apos; Bantu mine worker has a maximum intake of 3.0 l/min? In the August 1966 issue of the South African Journal of Science four of the present co-authors reported the mean maximum oxygen intake of a random sample of 338 Bantu recruits of different tribes to be 2.63 l/min with a standard deviation of 0.542 l/min, and these figures were repeated in a paper published in the November 1968 issue of this Journal. Admittedly the mean maximum oxygen intake of the six subjects used in the present study was 3.05 l/min, but since they were selected on the grounds of previous shovelling experience they can hardly be regarded as being &apos;average&apos; recruits. Thirdly, it seems to me that the authors are perhaps a little uncritical in their acceptance of the &apos;50 per cent of maximum oxygen intake&apos; level of activity for endurance work. I am not unmindful of the evidence upon which this level is based, but I suggest that the evidence is at best tenuous and that the whole topic of fatigue and &apos;optimum&apos; levels of productivity under conditions of high muscular activity and considerable psychological stress is a lot more complicated than would appear from the authors&apos; ready acceptance of the 50 per cent level. Under present working conditions the question is largely rhetorical because it would need an army of supervisors to ensure that all members of a typical gang work at &apos;optimum&apos; levels throughout the shift, but if individual performance should ever become more readily determinable the issue might become crucial to management and malayisha alike. So much for physiological matters; now a few random thoughts on some wider, practical issues raised by the paper. In the paragraph headed Material the statement is made that &apos;The mixture (of fine, medium-sized and bigger rocks) was considered to be representative of an average underground rock sample&apos;. Elsewhere in the report the authors specifically draw attention to the effect of particle size on the oxygen consumption of men shovelling graded material, and intuitively one imagines that the size distribution of the material being shovelled would be highly significant in a study such as this. Presumably the authors were forced to assess size distribution subjectively because of the lack of objective data on the subject, and possibly the necessity for this assumption highlights how little we know quantitatively about any of the variables in stope cleaning systems. In this connection it may be remarked that although the present study was largely designed to show how dip and stoping width effect energy expenditure in shovelling, no data are given-nor, probably, are they available-to show how the industry&apos;s stoping tonnage is distributed in terms of these two factors. It seems to me that if the mining industry seriously hopes to improve stope productivity it must start by measuring the basic variables in existing systems. Elaborating somewhat on the previous paragraph, there also seems to be a tremendous gap between the present study-and its predecessors-and the prospect of gainfully using the information so carefully garnered by the authors. It would be reassuring to hear from the authors that their work on the physiological aspects is being integrated in some master plan for increasing productivity of manual labour. This I fear is not the case, and if productivity has changed at all in recent years I would hazard a guess that the change has been brought about by random factors rather than by systematic engineering design. The Human Sciences Laboratory has worked extensively in stopes in the past, and possibly the time has come when it should widen the ambit of its operations to include engineering-type analyses of cleaning systems, with particular emphasis on the economics of rapid cleaning by manual labour. Perhaps experiments could be conducted with stakhanovite-type gangs consisting of men selected for their high maximum oxygen intake and superior motivation; these men might be offered special incentives in the shape of extra pay

Jan 10, 1969

By R. R. M. Cousens, W. S. Garrett

Discussion: L. T. Campbell Pitt: When Mr Garrett and I discussed the design and construction of plugs and bulk head doors to resist great water pressures in mines about ten years ago, we visualized an emeregeny when there would be no time for site preparation. We could not however, anticipate a problem of such magnitude and urgency as the one described in the paper under discussion. The paper very clearly describes the flooding and the measures taken to save the mine. The complete flooding would have been a national disaster. The account of the combat between man and water reads like the account of a military operation. It was an endeavour which achieved success because there was a master plan, tenacity and, in fact, heroism. The paper is of necessity a long one. In my contribution I will mention some historical facts and factors that I believe have relevance to the flooding and the saving of the mine. It is of great satisfaction to me to have been one of the two initiators of a new approach to underground plug design and construction. The investigation was taken over by a Chamber of Mines Committee which combined our early work with further research and the resulting data had a significant bearing on the West Drie emergency plug designs. The final plug length was correctly based on the requirements to obviate leakage. A plug to have structural strength only would have been very much shorter but so ineffective as to have become a waste of labour, material, and in consequence, wasted the limited time available to prevent flooding of the whole mine. The figure of 75 lb per sq in. sheer stress provided a very ample margin, in my opinion, but under the very difficult site conditions and the limitations of plug material suitable for the very unusual construction, justified such a figure. There must have been considerable temptation to reduce the safety margin due to the urgency to complete and commission the plugs, but it is much to the credit of the directors of this operation that nothing less than a safe design was permitted. In about 1945 Blyvooruitzicht Gold Mining Company, which was then mining in to the West Driefontein area to assist in early development, decided to protect themselves from a possible inrush of water from the latter mine. A bulk head door was accordingly designed and installed on 2 level between 1945 and 1948 at 4,218 ft below surface. Since West Driefontein paid for it, Gold Fields consulting mechanical engineers collaborated with their colleagues of Rand Mines who completed their design after a few modifications were agreed. This door was never used to prevent an inrush into Blyvooruitzicht but the exercise was very useful to Gold Fields when the high pressure doors initially installed on 10 and 12 levels between Nos. 2 and 3 shafts to enable isolation of one section of the mine from another were designed. At that time the capacity of West Driefontein to cope with an inrush of water was comparatively small because the storage in stoped areas and the installed pump capacity were much less than in later years. These doors together with others of the same design were later moved to the lower levels served by sub vertical shafts. In addition, doors to prevent flood water entering the pump chambers on 18 level were installed at each end of that level, and designed for a head of 360 feet so that water would have to reach 16 level before the pumps were flooded. All these doors were called upon to hold water and it is reported that only a small plug in one of the doors and a 4 in. dia flanged pipe joint failed. The lesson is that in these cases the smallest details warrant as much attention as the major ones. That these were the only equipment failures when so much depended on equipment, is very much to the credit of design engineers, both of the Gold Fields head office and companies who supplied both mechanical and electrical equipment. Until I had read the paper I wondered why the policy of isolation by bulk head doors was not continued as the development moved eastward towards the Bank Compartment and particularly when it pierced the Bank dyke. The reasons have been given in the paper. It was unreasonable to expect provisions to be made to counter the remote contingency that the large installed pumping capacity and mine capacity to store water would be exceeded during a peak inrush. When pumps were being considered for West Driefontein, it was decided that the Gold Fields standard underground main pumps at that time of 1 million gallons per 24 hours would be too small. Three alternatives were considered. 1. Very large units that would require underground sub assembly and dismantling of both pump and motor. 2. The largest pump and motor that could be conveyed as a complete pump or motor from surface to the pump chamber. 3. Pumps of higher speed to reduce dimensions and weight. It was decided to adopt alternate 2 because of avoidance of transporting pumps in parts and assembling underground. Alternative 3 was not favoured because high speeds would have introduced problems of more exact rotor balancing. I believe the decision was correct and in the crisis enabled comparative easy transport of pumps and motors to surface for overhaul and, if required, transfer to other pump stations. The standard pump thus became a 10 stage 1,500 rpm pump with a capacity of approximately 2 million gallons per 24 hours against a static head that varied

Jan 3, 1969

By G. A. Wiebols, N. G. W. Cook, N. C. Joughin

Discussion R. E. Rarnes (Member): The original concepts and the pioneering work now brought to the practical test stage by the Mining Research Laboratory team deserve our highest praise. The authors of this comprehensive paper rightly stress the urgency of establishing the extent to which the apparent potential can profitably be realised in practice. It is to be hoped that adequate funds will be made available by individual mining companies, the Chamber of Mines and manufacturers to attract the necessary staff and maintain the high rate of achievement of the last two years. From the Seventy-Eighth Annual Report of the Chamber of Mines and its members we see that, in 1967, with a Working Revenue of R759.8 million from gold and R54.6 million pit mouth coal sales and with profits from gold and uranium and pyrite of R307.9 million, only R1.9 million was spent by the Chamber on all forms of Research. It is considered unlikely that the associated mining companies and manufacturers exceeded this investment expenditure. Assuming a total of R4 million spent by the industry on Research and Development, this is less than half of 1 per cent of sales of gold and coal. This percentage, so low in comparison to North America and Europe, is no worse than that of Exploration expenditure which, in 1967, with South Africa&apos;s total mineral production of R1,287 million, was estimated to have been R6 million (Pretorius 1968). In a primary industry with ever present depletion of ore deposits and with cost escalation, expenditure on Exploration and on Research and Development is not a risky luxury but a tactical obligation. The potential rate of return on research expenditure into rock breaking is high. Stores consumed by gold and coal mines, members of the Chamber of Mines, totalled R316.2 million in 1967. Except for purchased power costing R42.2 million the highest cost group was explosives, drills and drill steel totalling R33.8 million or 10.7 per cent of the total stores consumed. In the paper under discussion it is claimed that the low &apos;effective stoping width&apos; should greatly reduce the likelihood of rock falls or rock bursts to the extent that permanent support can be dispensed with. Insofar as this narrow cut is only 12 in. in advance of the working area which, with a 10 in. channel, is unlikely to be much reduced in width from that achieved by current methods, this claim is not readily understandable. Were it to have been based upon the regional support gained from packed waste it would have been more acceptable. Pre-developed stope drives may give serious trouble at depth and for this reason it is questioned whether a stoping area can avoid periodic sub-development blasting-the spoil and fumes from which will interfere with the rock flow and continuous mining of the rock-cutter. If, in the mining method proposed by the authors, stope drives are cut as small as possible (6 ft by 6 ft) then 25 per cent of the total tons handled (excluding resued waste) and 5 per cent of the gold will be blasted conventionally in the stope. At this stage one cannot envisage tunnelling machines economically or practically capable of such work. The various methods described by the authors and subsequent contributors for breaking waste are most interesting. It was noted that the &apos;bull wedge&apos; and &apos;explosives&apos; in Fig. 1 of the paper were no further from the ideal point &apos;A&apos; than was &apos;cutting&apos;. The writer considers that the bold and imaginative steps taken by the Mining Research Laboratory Team, the mining companies and the manufacturers concerned will eventually lead to a successful rock cutting machine with universal application largely independent of rock type. This may take many years. In the meantime other methods of improving productivity of saleable metal by rock breaking teams should be investigated even if such methods have local applications only. In 1955 the writer conducted tests with a wire saw similar to those used in quarries in the Northern Transvaal and elsewhere. Jeppestown shale, the immediate footwall of much of the East Rand gold field, was cut at the rate of 6 in. per hour using sand, water and a special endless rope driven by a low h.p. motor. A hypothesis on its application was submitted to the Office of the Government Mining Engineer in 1955 and to other mining institutions in 1966 after the writer returned to South Africa. By inference, rope sawing was classed as less promising than other methods tested in the Orange Free State Goldfields (Parker 1969). With highly resilicified hanging and footwall quartzites this was not surprising and confirmed the writers findings when testing hanging wall quartzite from the East Rand in 1955. The relatively uniform conditions, the low strength, hardness, and silica content of the Merensky Reef platinum deposits (Gray and von Bardeleben 1969) and in particular, the existence of overlying Merensky pyroxenite (Cousins 1964) make this and the East Rand attractive areas for larger scale testing of wire saws. It is envisaged that in suitable rock types the 5/8 in. slot would be advanced down dip or down a minor dip. In undisturbed areas &apos;faces&apos; of up to 200 ft in length could be cut several feet in advance of breaking which could then consist of light blasting to the second free face or some of the methods now being tested for breaking waste in rock-cutting operations. A wire saw is an inexpensive and simple machine which, in some areas, could make significant and early gains in rock breaking efficiency as well as in ground and stoping width control.

Jan 5, 1968

By Peter Stacey

This presentation provides comments on the increasing challenges associated with pit slope designs from the perspective of a design reviewer. Besides the technical issues related to the significant increase in current and proposed slope heights since the primary methodology in current use for pit slope designs was developed, other factors are coming into play. These include changes in mining equipment and associated operating practices, as well as a growing awareness on the part of mining executives and other stakeholders of the significance of stable, or at least well-managed, slopes. In the latter area, the associated clarification of responsibility has led to the increased use of either in-house or independent review consultants working on the behalf of management. From a technical perspective, since the mid-1970?s there have been significant improvements in the tools, particularly analytical methods, that are available to slope designers. There is also an increased understanding of the importance of a detailed geological model, with strong emphasis on alteration and/or structure to form the platform for the slope designs. However, the basic technology for determining the rock strength aspects has changed little, although an expanding body of experience is being accumulated in its use and there is a reasonable degree of comfort in its application for slope heights of up to at least 500 m. In addition, slope management is now viewed as a critical part of the implementation of slope designs and this has been supported by continuing improvements in slope monitoring systems. In recent years safety has become a primary concern, in part as a result of some major slope failures that have attracted the attention of regulators and the public, as well as mining executives, who are being held more responsible for unsafe conditions and associated events. There is therefore a growing demand for risk assessments to replace the deterministic design approaches upon which the current design technology is largely based. The focus of mine executives on safety has undoubtedly in part facilitated the recent long overdue revitalization of research into the design and stability of large pit slopes, the requirement for which has been recognized for many years by practitioners. This research, as well as the CSIRO Large Open Pit Study, will almost certainly provide advances beyond the empirical strength determination methods such as the Hoek-Brown failure criterion, which form the basis for current rockmass strength determination. At the same time, as mentioned above, there is a growing awareness of the requirement for a detailed structural model as a major component of every large slope design. In addition, other areas requiring further research include the impact of groundwater pressures on rock mass strength, particularly in rocks with low permeabilities, and the role of stress in high open pit slopes. From the perspective of design implementation, even with the recent significant advances in metal prices, mine operators remain under pressure to minimize mining costs. To address these constraints, mining equipment of ever increasing size is being introduced. There are, however, some disadvantages to this trend in the area of slope design. For example, the large electric shovels are not well designed for scaling bench faces, nor are they cost effective in this mode. As a result, specialized equipment may be needed in the mining cycle to perform the clean-up duties, which in turn increases operating costs. Further, where the large equipment is used in minimum width pushbacks to reduce the instantaneous stripping ratio, the advance rates can be high, but at the same time the associated changes in operating procedures are often not conducive to the concurrent use of such measures as controlled blasting, careful scaling and drain hole installation that generally improve stability. The resulting conflicts which may arise between the interests of production and those of slope stability are often exacerbated by the fact that these stabilization techniques actually increase the operating costs on which the operations manager is frequently judged, even though there is an overall increase in profit. Meeting the objective of developing slope designs which are practicable , i.e., achievable in terms of every aspect of the operating constraints in the specific pit, requires interaction and compromise between the geotechnical engineer, mine planners and operating staff during the formulation of the design criteria. In the current environment, it is often no longer sufficient to present slope designs in deterministic terms to a mine planner who accepts them almost without question. Increasingly, the requirement is that they be proposed within the framework of risk levels, related both to safety and to economic outcomes, to a decision maker who may not be a technical expert in the mining field. In this context, the mine executives must have sufficient information and understanding to be able to establish acceptable levels of risk for the company and other stakeholders; in this process the slope designers must play a major role. These changing requirements for presentation of slope designs necessitate clear communication of the basis for the design, which may be very complex, so that the implications of the designs may be thoroughly understood by all concerned. To ensure clarity at this stage, the slope designer must not only quantify the uncertainty in the input parameters, including the geological model, but must also be able to communicate and defend the resulting design recommendations. Where particular designs may have high associated risks, simply because of the degree of uncertainty in the data, this must also be recognized and proposed methods of reducing the uncertainty included in the presentation. In summary, from a reviewer?s perspective slope designs must not only be technically sound, but must also address the broader context of the mining operation as a whole, taking into account such factors as safety aspects, the available equipment to implement the designs, and the acceptable risk levels for the company. In addition, the designs must be presented in a way that will allow the mine executives, who are ultimately responsible, and the operators, who implement the designs, to fully understand the basis and short-comings of the designs and the risks associated with deviation from any constraints defined by the designer. It goes without saying that there must also be a well-defined monitoring system to confirm stability and detect and manage any variations in the design model or unexpected instability.

Jan 1, 2006

By N. Mangesana

The effect of high solids concentration and coarse particle sizes (d50 ranges 90?300 µm) on the viscosity of a suspension of water and silica sand was investigated. The experiments were designed to include conditions that have been tested by other authors and those encountered in the operation of tumbling mills. The rheological data was measured using a tube rheometer with operating pseudo shear rates of up to 1500 s-1. The rheograms obtained depicted dilatant behaviour. The Otswald-de Waele, Bingham, Herschel-Buckley and Casson models were fitted to the experimental data. The Herschel-Buckely model, which approximates the yield point and gives an indication of the shear thinning or shear thickening behaviour of the suspension, was found to provide the best description of the flow curves for all slurries. The Herschel-Buckely model was then used to determine the apparent viscosity of all the tests. The apparent viscosity and yield stress increased with solids concentration and particle size at the different pseudo shear rates. The increase in slurry viscosity with solids concentration was attributed to increased frequency of particle-particle interactions. The increase in slurry viscosity with particle size was attributed to increased inertial effects. At low shear rates the sand slurry exhibited shear thinning behaviour for all solids concentrations. At higher shear rates above 1000 s-1the high solids concentration suspensions exhibited a transition from shear thinning to a shear thickening behaviour.

Jan 1, 2008

By F. W. Petersen

The Conference Minerals & Materials &apos;96 was held in Somerset West, South Africa, from 31st July to 2nd August, 1996. It was organized by the Universities of Stellenbosch and Cape Town, the Cape Technikon, and the Western Cape Branch of The South African institute of Mining and Metallurgy (SAIMM). The three-day Conference was attended by 180 delegates, representing countries such as Australia, South Africa, United Kingdom, Finland, Sweden, Germany, Poland, Zambia, and Zimbabwe. The programme and associated exhibition were well organized, and each of the delegates received two volumes of proceedings containing the 77 papers presented at the Conference.

Jan 1, 1996

Professor G.T. van Rooyen has guided the Department of Materials Science and Metallurgical Engineering at the University of Pretoria in South Africa for the past 32 years. During this period, 54 masters&apos; degrees have been awarded in the Department, and 17 doctorandi promoted. He has also made a major contribution to industry by his incisive analysis, relevant and practical synthesis, and his exceptional talent in innovative design. He is still active in fracture analysis, thermal fatigue, weld simulation transformation kinetics, and fracture mechanics, and continues to contribute to a better understanding of metallurgical problems encountered in practice. He has advised many companies, and has received many honours and recognitions.

Jan 1, 1994