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By S. Kahraman

The prediction of rock properties from indirect testing methods is important, particularly for preliminary investigations since indirect tests are easier and cheaper than the direct tests. In this study, we investigate the predictability of the uniaxial compressive strength (UCS) and Brazilian tensile strength (BTS) of rocks from the indentation hardness index (IHI) obtained using point load apparatus. Forty-six different rock types, 14 of which were igneous, 15 were metamorphic, and 17 were sedimentary were tested in the laboratory. The UCS and BTS values were correlated with the corresponding IHI values and the results were statistically analysed. The influence of rock classes on the relationships was also investigated. A strong correlation between UCS and IHI was found for all data. The correlation between BTS and IHI is not as strong as the correlation between UCS and IHI, However, it is in the acceptable limits. When the regression analyses were repeated for igneous, metamorphic, and sedimentary rocks, the correlation coefficients were generally increased. The results show the UCS and BTS can be estimated from IHI, In addition, the effect of rock classes on the relationships between IHI and both UCS and BTS is important.

Jan 1, 2012

By J. A. Venter, M. K. G. Vermaak, J. G. Bruwer

Electrostatic separation is employed in the concentration of zircon and rutile. The zircon concentrate undergoes an acid treatment to remove impurities from the surface of both the zircon and rutile. The purpose of the acid treatment is to increase the difference in the resistivities of the two minerals, thus ensuring the best possible electrostatic separation efficiencies. Previous test work suggested that these impurities are not removed, but only modified; the surface modification seemed more prevalent in the case of the rutile. The resistivity of the rutile changes with pH and thus the electrostatic separation of the rutile is influenced. X-ray photoelectron spectroscopy (XPS) indicates that there is an increase in the OH and adsorbed H2O concentrations on the rutile surface. XPS also showed significant differential charging on the rutile surface, which indicates that the species on the rutile surface have different resistivities. The zircon particles from the conducting and non-conducting streams have similar resistivities and no major differences in their surface species. Zircon losses during the final electrostatic separation appear not to be due to surface effects, but due to shielding of particles during the separation.

Jan 1, 2007

By G. Chunnett

Platinum metal prices have risen significantly during the past 18 months, and have remained at elevated levels. Driving these bullish prices are sustained jewellery demand, mainly from the Far Eastern markets, and ongoing autocatalyst usage in response to ever more demanding global environmental legislative requirements. Within South Africa, the areas north and south of the Steelpoort River in the Eastern Bushveldare well known for their significant resources of platinum. The bulk of the resources have lain dormant in anticipation of the very situation that is currently occurring in the marketplace. Anglo Platinum is the largest primary platinum producer in the country, and is uniquely positioned to take advantage of the current elevated metal prices and shortfall in supply of platiniferous metals. In addition to its production capabilities, Anglo Platinum holds an extensive portfolio of mineral reserves and resources which underpin its ability to implement expansion projects to continue growth in platinum group metal production. It also has access to, and is actively expediting, the exploration of a range of properties where the company can further expand current production capacity or supplemented depleted production levels.

Jan 1, 2006

By G. Mitchell

Much debate has ensued over the past few years on the speed of transformation in the mining industry. By transformation is meant the degree to which the industry has met the requirements of the Mining Charter. In response to this, the Department of Mineral Resources (DMR) commissioned a research study in 2009 to ascertain the degree of industry compliance. The mining industry in response made a presentation to the Minerals Portfolio Committee in Parliament in 2011, during which it released aggregated figures on industry compliance to the Mining Charter. The conclusions of both of the studies are widely divergent. It is argued in this paper that both processes are flawed. The government-sponsored research is empirically and methodologically weak and the results therefore have to be taken with a great degree of caution. The Chamber of Mines figures, on the other hand, while faithful to the reporting of the Chamber member companies, do not represent the entire span of the industry but only the larger mining companies. It is further argued that in order to ascertain a true reflection of the industry an independent audit be undertaken using recognized social scientific survey methods.

Jan 1, 2013

By A. Bain

The use of plastics in the coal mining industry is making slow progress whereas these materials could make a greater contribution to safety, to a reduction of working costs and to the higher productivity of mine workers. Possibly the reluctance to experiment with the new material of our age is due to the low profit margin of coal mining. This note has been prepared to present a brief survey of what has been done in the last few years and to mention some of the investigations the author has made and is making in an attempt to develop more use of plastics in the industry. Some of the plastics used on the mines have taken their place in the industry in the same manner that they are used in everyday life while others have been introduced because there has been a need for them. New uses and applications are being developed and these are the ones that are most interesting. The plastic that is specially developed to give the maximum benefit and not the one that is a modification of some other everyday product is the next development in the field. Many manufacturers are keen to promote such investigation but are not aware of the problems the mines wish to solve and therefore it is only through management itself that this development can be carried out. This note deals with plastic material under three headings: (a) Plastic as the superior material, and briefly describes how plastic has replaced a few major items which are better when made from plastic. (b) Plastics of necessity, being a short summary of how plastics had to be introduced because of laws and conditions making it a necessity. (c) Development of new ideas, being briefly some of the ideas being developed overseas and some of the ideas being tried by the author. Plastic items in common use such as in housing, electric cables, laboratory equipment, awnings, nylon bearings, locomotive brake linings, etc. being well known are not discussed. PLASTIC AS THE SUPERIOR MATERIAL Plastic belting underground Following a fire in a belt road in England resulting in the deaths of many workers, and subsequently a fire accompanied by fatalities in a belt road in a mine in this country, a law was introduced which states that only flameproof belting is to be used underground. This ruling forced the mines to use P.V.A. belting as no other was available. This belting has non-inflammable characteristics that are superior to rubber. Due to the high tension on long-distance belts used today the need for stronger belting material called for something better than cotton and the answer to this was nylon. Nylon also has the ability to withstand dry-rot which reduces the life of a belt very quickly.

By P. C. Schutte, J. R. Smith

The objective of ergonomics is to enhance the effectiveness and efficiency with which human tasks are carried out. Furthermore, the objective is to improve desirable human values. This can be achieved by enhancing safety, reducing fatigue and stress, increasing comfort, increasing job satisfaction, having greater user acceptance and thereby improving the quality of life. Mechanization has influenced the prevalence of injury, mainly due to the application of human physical effort as the power source. With mechanization, the operator’s function is now essentially one of control rather than being an energy source, however the risk of injury has not diminished. Mechanization in itself has introduced inefficiencies, health risks and physiological stress. The major objectives of ergonomics are discussed through examples of acceptable and less successful implementation of ergonomics within mechanized mining. The influence of the machine system on the human is addressed and practical solutions to improve and optimize the interaction of the human and the machine are outlined. Furthermore, practical examples of control and display integration, anthropometric and biomechanic influences on design, orientation, posture and stereotypes are used to accentuate the advantages of the application of sound ergonomics principles to the specialised area of mechanized mining.

Sep 1, 2001

By H. A. D. Kirsten

The effects of the mining of deep-level tabular reefs are usually evaluated by use of continuum, elastic mining simulation analyses. This paper gives the results obtained from a series of analyses in which stopes of limited span are considered to be excavated in a non-linearly non-elastic, jointed and fractured rockmass. In particular, the theoretical influence of soft backfill in these conditions is evaluated. It is shown that the stress distribution and behaviour of the rockmass, alternately taken as an intact-elastic and as a fractured non-elastic medium, are completely different. The relevance of the energy-release rate commonly calculated in mining-simulation analyses, and the efficacy of its correlation with seismicity and the associated rockbursts, are reviewed. In deep-level mining operations, it is not practically feasible to obviate releases of seismic energy. The fact of their occurrence should therefore be accepted and, rather than considering the reduction of energy release as the primary objective, efforts should be concentrated on minimizing the effects of such release. Analytical results are given to demonstrate that this approach is not only correct, but also the only feasible solution to the rockburst-seismicity problem in deep mines.

Jan 1, 1989

By F. G. Hill

The paper reviews the restrictions imposed by the Department of Mines (now the Department of Mineral and Energy Affairs) on the surface use of ground that has been undermined at shallow depths (down to a depth of244m). The reasons for the restrictions are discussed, with special reference to the early records kept by the Department of Mines on subsidence and fracture of the surface. A discussion of the nature of the strata overlying the ore-body, and the effect of undermining, is followed by a detailed account of investigational work, particularly since 1970, on the stability of shallowly undermined ground. The significance of the data collected during the investigations is considered next, with special reference to the social and economic implications. These are so farreaching, that it is proposed that the already flexible approach of the Department of Mineral and Energy Affairs in considering what structures may be built on undermined ground should become even more flexible. To this end, the appointment of a Commission is proposed to collect as much information as possible on the stability of ground undermined at shallow depth, and to revise the current overrestrictive conditions or guide lines that are in use.

Jan 1, 1981

By N. C. Joughin

A simplified economic model is derived for the financial return from a new gold mining project. The model is used to analyze the effects of changes in the mining rate, capital costs, working costs, value of the reef and the stoping width. The most effective avenues for improving the return from a new project are indicated. It is shown that those technological innovations which would improve the return significantly, and therefore make it possible to open more mines, are the use of smaller mines, means for improving the mining rate to capital costs ratio for smaller mines, planning and control of mines by computer simulation, an improved mine valuation procedure and means for mining at a decreased stope tramming width.

Jan 1, 2014

By L. Forbes, G. Forbes, J. Wang

Bubble size measurement is a vital part of flotation system analysis and diagnostics. Over the years, a great many different bubble size analysis tools have been developed. However, all of them rely on ex-situ measurement and in-pulp sampling techniques. This paper evaluates the Mettler Toledo ParticleView™ Measurement probe as a novel method for in-situ bubble size measurement. This device is then compared to the conventional Anglo Platinum Bubble Sizer (StoneThree). It was found that the in-situ bubble size analysis technology appears to be a more user-friendly and reliable option for determining bubble size in flotation. However, the current instrument design is not suited to industrial applications. Keywords: Bubble size measurement, bubble coalescence, PVM probe

Jan 1, 2020

By E. Mpoloka

Debswana together with ADP as their design partner have embarked on an RDP project at Jwaneng Mine. The objective of the project is to install a 2 million ton per annum mineral processing plant that will fast track the recovery of diamonds from the Debswana tailings resource to ensure maximum return on investment for the company. Due to the prevailing economic conditions Debswana has had to review the way they used to build plants in the past and consider simple, fast and effective ways of doing things. The rapid deployment plant concept is therefore the most suitable means of achieving this objective. Debswana is also considering an operating partner who will operate far more efficiently and cheaply compared to the larger more cumbersome and less agile Debswana.

Jan 1, 2010

By D. Clement

A comparison between hydraulic and pneumatic rockdrills by D. CLEMENT The regulation of compressed-air reticulation systems is very poor compared with that of electrical systems; this means that electrohydraulic rockdrill systems offer greater flexibility, additional power being readily available at the working face. Hydrometallurgy A new journal devoted to all aspects of the aqueous processing of metals is scheduled to appear this year. Entitled Hydrometallurgy, the journal will be published in quarterly issues, one volume per year. Mineral dressing Contributions are invited for the Symposium on Recent Progress in Mineral Dressing in South Africa, which is to be arranged jointly by the South African Institute of Mining and Metallurgy and the National Institute for Metallurgy. Mineraalbereiding Bydraes word verlang tot die Simposium oor Onlangse Vordering met Mineraalbereiding in Suid-Afrika wat gesamentlik deur die Suid- Afrikaanse Instituut vir Mynbou en Metallurgie en die Nasionale Instituut vir Metallurgie gereel gaan word. Rock mechanics The Sixteenth Symposium on Rock Mechanics is to be held at the University of Minnesota from 22nd to 24th September, 1975. The Symposium is the official Symposium for 1975 of the International Society for Rock Mechanics (I.S.R.M.), and the Council for I.S.R.M., consisting of members from 25 countries, will meet during the Symposium. Powder metallurgy The annual meeting on powder metallurgy organized by The Metals Society is this year to be held at the Stratford Hilton Hotel, Stratford-upon-Avon (the notification did not include the date of the meeting). Vacation School The South African Institute of Mining and Metallurgy has great pleasure in announcing its intention of holding a vacation school on the topic of electric-furnace melting. NIM reports Report no. 1681 The determination of sulphur and phosphorus in chromite. Report no. 1687 The viscosities and electrical conductivities of slags associated with the production of high-carbon ferromanganese alloys.

Jan 3, 1975

By S. Gqebe, A. Lewis, M. Rodriguez-Pascual

"Gravitational sedimentation of suspensions in various precipitation processes is hindered by colloidal stability. This is due to the high surface charge of the suspension and results in strong attraction/interaction between the ions on the particle surface and counter-ions in solution. Moreover, this strong interaction results in a charge build-up that renders the suspension stable. In order to induce gravitational sedimentation of these particles, a redistribution of ions close to the particle surface is required. We therefore sought to redistribute ions close to the particle surface by applying a magnetic field. This results in the reduction of interparticle electrostatic repulsive forces and a subsequent increase in the zeta potential of a suspension. For the purpose of this study, a copper sulphide suspension was used. Copper sulphide particles were exposed to a range of field strengths for set exposure times and their zeta potential was measured before and after exposure. All particles had an initial zeta potential value equal to or less than –40 mV prior to magnetic field exposure. A significant increase in zeta potential was observed, with values reaching a maximum of –16.5 mV when exposed to a 2 T field strength for 40 minutes. This is due to Lorentz ion shifts resulting from the Lorentz force exerted by the magnetic field on the particle surface. IntroductionMetal sulphide precipitation is a process for treating industrial waste streams with high residual concentration of mixed metal ions and acid mine drainage. This process has been reported to achieve higher metal removal compared with the industrially prevalent lime precipitation, due to the sparingly soluble nature of the metal sulphide precipitates formed. However, precipitation is governed by high levels of supersaturation which favour the formation of fine particles (Lewis, 2010). Consequently, some of the metal sulphide fines formed exhibit slow settling dynamics and thus tend to remain suspended in solution."

Jan 1, 2016

By G. P. Dyke

The MRMR classification system was developed specifically for mining applications, namely caving operations, and is one of three rock mass classification systems used in the South African mining industry today. Increased usage of the MRMR classification system has raised concerns that it does not adequately address the role played by discontinuities, veins and cemented joints in a jointed rock mass. To address these concerns, Laubscher and Jakubec introduced the In-Situ Rock Mass Classification System (IRMR) in the year 2000. Although the IRMR system is more applicable to a jointed rock mass than the MRMR system, a quantitative comparison of the MRMR and IRMR classification systems indicates that there is not a significant difference between the resultant rock mass rating values derived from the two classification systems.

Jan 1, 2008

By G. P. Dyke

The MRMR Classification System was developed specifically for mining applications, namely caving operations, and is one of three rock mass classification systems used in the South African mining industry today. Increased usage of the MRMR Classification System has raised concerns that it does not adequately address the role played by discontinuities, veins and cemented joints in a jointed rock mass. To address these concerns, Laubscher and Jakubec introduced the In-Situ Rock Mass Classification System (IRMR) in the year 2000. Although the IRMR System is more applicable to a jointed rock mass than the MRMR System, a quantitative comparison of the MRMR and IRMR Classification Systems indicates that there is not a significant difference between the resultant rock mass rating values derived from the two Classification Systems.

Jan 1, 2008

By D. J. Adams, R. G. Gürtunca

In situ measurements and numerical modeling based on elastic theory showed that backfill stresses are considerably higher than originally thought. This has led to a change in understanding of rockmass behaviour. After describing previous work on the behaviour of the rockmass, this paper discusses possible reasons for the high stresses measured in backfil, and identifies the rockmass mechanisms possibly generating these stresses. It is concluded that the joints and the geological stratigraphy can lead to increased elastic convergence, and that the inelastic behaviour of the rockmass is also partly responsible for the increased closure measured in backfill. The use of an in situ modulus is suggested as an interim solution until a new computer model that allows for joints, different layers, and inelastic closures becomes available.

Jan 1, 1991

By W. J. Kotzé

Die derde colloquium van die Spesialiste-afdeling van die SAIMM is op 19 November 1980by die Universiteit van Pretoria gehou en is deur sowat 40 mense bygewoon. Dr J. P. Hugo tree as Voorsitter op en heet al die aanwesiges welkom, en stel elke spreker om die beurt aan die vergadering voor.

Jan 1, 1981

The comments by Mr Chaston were constructive and much appreciated. Considering firstly the recovery of cassiterite from fine deslimed material. A size distribution analysis shows that 58 per cent of cassiterite in Union Tin flotation concentrate reports in the minus 15 micron (quartz) size range. This is achieved at a recovery of 67 per cent and concentrate grade of 42,6 per cent. It is of interest to note that at Altenberg in East Germany 85 per cent of the tin in deslimed minus 43 micron material is recovered into a 14 to 16 per cent Sn concentrate using para-tolyl arsonic acid as collector. Reconcentration of this material is then carried out using two shaking table stages which recover 53 per cent of the tin in a 50 per cent Sn concentrate. Flotation was resorted to after recovery rates of 35 per cent and concentrate grade of 30 per cent had been achieved in a 275 ton per day plant comprising 130 tables. Tests on tabling of deslimed minus 43 micron material have not been carried out at Union Tin. The cost of equipment actually associated with cassiterite flotation amounts to about R60 000. The

By M. Cortie, L. Iorio

The amount of nitrogen contained in an austenitic stainless steel affects its properties significantly. The maximum content of nitrogen feasible in a range of experimental low-nickel austenitic stainless steels containing significant additions of copper is evaluated The nitrogen content is calculated based on published interaction coefficients, and by use of the FACT thermodynamic computer program and database. The differences between the two methods of prediction can be attributed to inaccuracies in the published interaction coefficients. The calculated nitrogen contents of some experimental alloys are compared with the actual nitrogen contents obtained when the alloys were produced in an induction furnace. The actual nitrogen contents obtained were higher than those predicted by either method, and this is believed to be due to a super saturation of nitrogen occurring in the melt, which was not relieved during the short period in which the charge was molten. It was evident that the experimental alloys can contain between 0,25 and 0,40 per cent nitrogen (depending on temperature, composition, and nitrogen pressure) when melted in a sealed induction furnace, and this is more than adequate for the purpose of forming and stabilizing the austenite phase.

Jan 1, 1994

By R. G. B. Pickering, H. H. Haase

Few innovations in the South African gold mining industry could have a more significant impact on improving profitability than non-explosive methods of mining. The far-reaching benefits of this approach are explained and the progress made through development work funded by the industry is described. Three methods are considered: impact ripping, sloting with abrasive waterjets and diamond saws, and breaking from drilled holes with waterguns and electric pulses. Of these methods, impact ripping is the most advanced and requires only minor refinements before production applications can be initiated. Although this method, based on current performance, is expected to yield considerably increased profits, it is predicted that it could perform several times better than at present with further development. The other methods of rockbreaking also show potential. Waterguns and electric rockbreaking would be attractive in unfractured rock for difficult geological conditions, and for confined areas such as gullies and development ends. Methods based on sloting could be combined with any of the other methods to enhance their effectiveness and thus yield further improvements in profitability; also, they could be used to advantage in specific applications. Al the discussed methods, therefore, deserve to be developed further.

Jan 1, 1991