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By B. Kruger

After the milling and flotation of the platinum bearing ore, the flotation concentrate is electrically smelted in 6-in-line electric arc furnaces and the resulting furnace matte treated in Peirce Smith converters to remove the iron. The iron-free (less than 1% Fe) converter matte is granulated and sent to the base metals and precious metals refineries for further processing. During the smelting and converting processes two distinct gas-strength gas streams are produced: ?The Peirce Smith converter off-gas contains 4%?9% SO2which is treated in a conventional sulphuric acid plant to produce 94% H2SO4. ?The electric furnace off-gas contains 0.9% SO2which was (until September 2002) vented through a 91- metre high stack to atmosphere. In October 2002 Impala Platinum commissioned a SULFACID® plant at its smelter in Rustenburg, which recovers the SO2from the electric furnace off-gasses into a weak sulphuric acid solution. The SULFACID® technology utilizes wet activated carbon to oxidize the SO2toSO3. The SO3reacts with the water on the catalyst and is washed off the catalyst bed as a sulphuric acid solution with up to 13 wt. H2SO4. The plant operates at 60ºC and at atmospheric pressure. The SULFACID® technology is widely used in the pigment industry. This is, however, the first application of the technology on electric furnace off-gas. Keywords: SO2, sulphuric acid, electric furnace, off-gas, SULFACID®

Jan 1, 2004

By R. Singh, A. K. Dhawan, M. Dixit, H. Dev

ABSTRACT: The modulus of deformation of rock mass is an important engineering parameter required for the design of foundation of hydraulic structure and to study the interaction of rock mass and the structure at the foundation support. Different equipment and techniques are used to arrive at the design modulus value. Since any error in the estimation of modulus values results in multiplication of its effects in the analysis, it is necessary to know about the reliability of testing equipment and procedures. In the present study modulus values obtained by different in-situ equipment at different project sites have been compared. KURZFASSUNG: Der Verformungsmodul von der Felsenmasse ist technisch ein wichtiger Parameter, den man zur Konstuktion des Grunds fuer die Hydro – Tektonik, benoetigt um auch die gegenseitige Beeinflussung der Felsenmasse und der Tektonik am Traggrund zu betrachten. Verschiedene Geraete und Methoden werden angewandt, um den Ausfuehrungsmodul -Wert zu erreichen. Es ist erforderlich, die Zuverlaessigkeit der Pruefeinrichtung sowie des Verfahrens zu kennen, da irgend ein Fehler in der Abschaetzung von Modulwerten in der Analyse zu einer Vervielfachung ihrer Einwirkung fuehrt. In der vorligenden Arbeit werden die Modulwerte gewonnen aus unterschiedlichen Einrichtungen an Ort und Stelle and verschiedenen Projekt -Stellen mit einander verglichen. SOMMAIRE: Le module de deformation d’une roche est un parametre important pour la conception et realisation des ouvrages hydrauliques ainsi que pour etudier l’interaction de la roche et de la structure d’appuis de base. De divers equipments et techniques sont employes pour determiner la valeur de ce module de conception. Puisque l’effet d’une erreur d’evaluation du module devient multiplie dans l’analyse, il est necessaire de savoir la fiabilite des equipments et des methods qu’on ulilise. Dans cette etude, on a compare les valeurs des modules obtenues en employant les equipments in-situ aux sites differents de projets.

Jan 1, 2003

By H. Gercek, M. Genis

In this paper, the effects of dynamic loads on the geometry of the failure zone occurring around underground openings, excavated in deep and massive rock masses, have been investigated. Following an elasto-plastic stress analysis of a two-dimensional underground opening under static conditions, dynamic loads have been applied. In the static and dynamic analyses, FLAC2D computer program has been utilized. Maximum ground acceleration value is selected as an input parameter. An index determining the relative size of the yield zone around the opening has been used for comparison of instabilities. In diesem Bericht wurden die Auswirkungen von dynamischen Lasten, auf die Geometrie der Bruchzone in der Umgebung von Untertagehohlräumen, die in tiefen und massiven Gebirge aufgefahren wurden, untersucht. Nach einer elasto-plastischen Spannungsanalyse eines zwei-dimensionalen Untertagehohlraumes unter statischen Beanspruchungen, wurden dynamische Lasten aufgebracht. Für die statischen und dynamischen Analysen wurde das FLAC2D Computer Programm verwendet. Die maximale Bodenbeschleunigung wurde als Eingabe Parameter gewählt. Zum Vergleichen der Unstabilitäten wurde ein Index verwendet, der die relative Grösse der Bruchzone in der Umgebung des Hohlraumes bestimmt. Dans ce papier, l’influence des chargements dynamique sur la géométrie de la zone en rupture observée autour des cavités profondes excavées dans des massifs rocheux ont été étudiées. Des chargements dynamiques ont été appliqués, dans le cas d’une modélisation bi-dimensionnelle de l’excavation d’une cavité profonde, sur la base d’une analyse élastoplastiques des contraintes en conditions statiques. Le code de calcul FLAC2D a été utilisé pour les analyses statiques et dynamiques. La valeur maximale de l’accélération du sol est choisie comme paramètre d’entrée. Un indice déterminant la taille relative de la zone sollicitée autour de la cavité a été utilisé pour comparer les différentes instabilités.

Jan 1, 2003

By F. Hees, A. H. Bracken, L. I. Boshoff

"Biological cementation of the Mandena heavy mineral sand deposit in Madagascar was causing difficulty in dredge mining and hence in planning and control of production rates. An investigation was initiated to better evaluate the geotechnical properties of the orebody by defining the distribution and geotechnical properties of the cemented strata, in order to generate a site-specific geotechnical model for the deposit. The geotechnical characterization was developed by an integrated approach using several ground investigation techniques such as piezocone (CPTu) testing, geotechnical drilling, standard penetration testing (SPT), as well as laboratory testing. The final outcomes of the investigation included a 3D geotechnical model showing the distribution and extent of the cemented areas, as well as the typical geotechnical parameter ranges associated with each of the defined geotechnical units. The interpretations developed were incorporated into the mine and production planning to ultimately optimize operational planning and control.IntroductionQIT Madagascar Minerals (QMM) is a heavy mineral sand mining operation at Mandena, near Fort Dauphin in Madagascar. During the final planning and commissioning stages of the project, the need to fully characterize the unusual geotechnical conditions was identified and a geotechnical investigation became necessary.Nature of the problemDuring the commissioning phase it was found that mining production was being hampered by biologically cemented/indurated layers encountered within the sands. Closer inspection of the indurated horizons in the dredging face revealed that these layers contain a high loading of bacteria and fungi. It appears that the bacteria produce an extracellular (outside the cell) polysaccharide (i.e. sugar and carbon salts), which form a gelling biofilm to trap nutrients. There are a number of different bacteria. The fungi, on the other hand, produce a network of fibrous strands that bind the sand grains together. Thus both bacteria and fungi probably contribute to the ‘apparent cohesive’ strength or binding of the indurated sand (Lynn, 2008)."

Jan 1, 2017

By T. A. Silva, A. C. Bragança

Lime has been added to the iron ore slurry transported by the Samarco pipeline since its operation start-up in 1977.Initially, internal corrosion was the main concern therefore the reagent was used only for pH correction. Over the last ten years, though, transport of more complex slurries demanded a significantly higher dosage of lime to guarantee adequate rheology control. Several other reagents have been tested for the same purpose yet none has proven to be as effective regarding technical performance, environmental impact and cost. However, an alternative was sought so that the slurry rheology could still be controlled in case lime addition became impracticable. The objective of this paper is to present a technical solution for this matter, which takes into account environmental aspects. It consists of adding soda for pH correction and an organic coagulant as a rheology modifier. The latter is a quaternary ammonium salt which affected the slurry transport properties in the same manner as lime when tested in a laboratory. It showed no plug formation and allowed solid particles to settle, forming a loose sediment after rest. These results indicate a low probability of plug occurrence in the pipeline and the formation of a readily reslurryable sediment upon shutdown of the pumping system. Industrial tests should be performed in order to validate the laboratory results.

Jan 1, 2007

By M. Rudolph, R. Tolosana-Delgado, E. Schach, M. Buchmanna, G. van den Boogaart, U. Peuker

The multidimensional characterisation of processes based on various particle properties is a key requirement for a detailed prediction on certain process streams. To access the relevant particle properties (e.g. particle size, particle density and mineral content) automated mineralogy (i.e. Mineral Liberation Analyser) is applied. The kernel density estimation is used to transfer the received discrete particle data into continuous distributions without the necessity of binning the information and the related loss of information. From these continuous distributions, multidimensional separation curves are estimated. The uncertainty of these representations is tracked via bootstrap resampling. For the evaluation of the separation efficiency of the multidimensional separation curves, the statistical entropy is calculated. The statistical entropy represents a local (for each property combination) as well as a global (for the investigated property range) measure of separation efficiency and can be weighted with various property distributions (e.g. mass or mineral mass distribution) to allow for a comparison of different parameter settings and processes. With the help of a case study of a dry magnetic separation of a cassiterite bearing skarn ore from the Erzgebirge (Germany), the methodology is presented and the results are discussed in detail. Keywords: Multidimensional, magnetic separation, kernel density estimation, mineral liberation, statistical entropy

Jan 1, 2020

By Dick Stacey

Many open pit mines are now being mined at very significant depths, often at depths far greater than was originally planned. Even deeper open pits are also being planned, to depths that would be considered deep by underground standards. The heights of the resulting rock slopes are usually beyond the current experience and knowledge base. The exceptions are, perhaps, some very high and steep natural rock slopes. These natural rock slopes are also assuming greater significance owing to pressures of infrastructure development and consequent exposure of such infrastructure to the hazards of slope failure and landslides. Developments in road and rail infrastructure are also resulting in higher rock cuttings. Present understanding of the mechanisms of slope behaviour and failure for high slopes, and for slopes subjected to high in situ stress conditions, appears to be lacking. If the mechanisms of slope behaviour are not well understood, the validity of commonly applied methods of analysis of the stability of such slopes may be questionable. The papers in this specialist International Symposium, including papers on mechanisms and monitoring techniques, and case studies will contribute to the understanding of these issues. The Symposium has attracted good international participation, from both the attendance and authorship points of view. We are very grateful to all presenters and delegates for taking timeout of their very busy schedules to come and share their knowledge and we hope that all will benefit from this event. Thanks are due to the Organising Committee and to the members of our International Advisory Panel for the ideas, the contacts and the badgering, and to the Secretariat of the South African Institute of Mining and Metallurgy for the organisation.

Jan 1, 2006

By Peter N. Calder, Alan Bauer

The complexity of modem open pit load-haul-dump systems is described, and the need for realistic working models is pointed out. Both standard and probabilistic simulation procedures are discussed, probabilistic simulation being indicated as the more powerful and practical technique. Acquisition of the necessary pit operating data required for simulator construction and general modelling procedures are described. Finally, results from a typical open pit simulator are used to indicate the scope of the technique.

Jan 1, 2014

By H. C. Voges

An account is given of the tests being conducted by Iscor on the following processes for the beneficiation of coal fines: froth flotation, gravity separation, heavy-medium separation, and pneumatic and column flotation. The coals used in the tests came from the Durnacol, Tshikondeni, Grootegeluk, and Hlobane collieries. The problems involved in the dewatering of fine products are stressed. From a theoretical study of the efficiencies that should be possible for a hypothetical South African coal, it is concluded that future fines-beneficiation plants in South Africa may use standard heavy-medium cyclones for coal down to 1 mm in size, fines heavy-medium separation for the 1 mm to 450 µm fraction, and column or pneumatic flotation for the minus 450 µm fines.

Jan 1, 1991

Performance testing is often used by project owners and financiers to provide protection from, or assessment of, technical aspects of project design, procurement, construction and commissioning. The performance tests can range from comprehensive performance warranties relating to process performance and production in the case of lump sum turn key (LSTK) projects to less onerous demonstration tests for cost reimbursable contracts. This paper will discuss performance testing from both the contractor's and owner's perspectives and focuses on: ? when performance tests are required, ? what type of performance test/warranty is optimum for each type of project, and ? how project performance should be evaluated. The requirement for performance testing can be driven by the project financiers, particularly in the case of smaller resource development companies. In such cases, differentiation between owner's risk and contractor's risk can become contentious. At the other end of the spectrum, larger mining houses may choose to heavily influence the engineering and design process with the contractor supplying services on a reimbursable basis. In that case, the performance testing process is often limited to demonstration tests that validate performance for the owner's corporate governance requirements. This paper was prepared due to the lack of published benchmarking of performance testing and the resultant differences in expectations between a contractor and a project owner that often surface late in the contract negotiation process. The paper provides a checklist of requirements for both the owner and the contractor that may be used to provide `common purpose' early in the contract negotiation process.

Jan 1, 2007

By J. Grobler, J. Zietsman

"Understanding the influence of feed material mineral assemblage on spiral separation is paramount for the successful and consistent operation of a spiral plant. Plant stability is required to maintain high recovery of valuable heavy minerals (VHM). Standard material analysis methods used in the heavy mineral industry to evaluate spiral separation behaviour are unable to quantify performance differences in the case of large variations in feed assemblage. This study illustrates a systematic approach to evaluate spiral separation performance. This technique was applied on a four-stage spiral plant. The performance information was used in a circuit simulation to clearly illustrate the importance of correct setting of the spiral splitter position and resulting spiral mass loading to ensure optimal circuit stability and maximum VHM recovery.IntroductionHeavy mineral sands deposits generally consist of naturally fine-grained, free-flowing sand due to the way in which the deposit was formed. The size of the heavy minerals market is roughly 8 Mt/a of zircon and titanium combined (Iluka, 2013). If an average combined feed grade of 5% zircon and titanium and an average combined overall product recovery of 80% are assumed, the resulting run-of-mine feed tons that would require primary spiral beneficiation is 200 Mt/a. The number of spirals required for the processing of this material, assuming 6500 operating hours per annum, an average of 2 t/h per start, and the same number of rougher spirals as other duty spirals, is over 30 000 spirals for the heavy mineral sands business alone. These numbers clearly illustrate the importance of the spiral in the heavy mineral industry.The aim of a spiral plant in the primary processing value chain of a heavy mineral process is to reject non-valuable quartz (a light mineral) from various valuable heavy minerals (VHM). The product from the spiral plant is a heavy mineral concentrate that has a reasonable grade (more than 90% heavy minerals) at a reasonable heavy mineral recovery (greater than 90%). This benchmark is fairly easy to achieve if all the mineral particles are well liberated (as in the case free-flowing sand), the feed is properly deslimed (-45 µm fraction removed to less than 5% of the solids mass), and the spirals are fed within design solids concentration (water to solids ratio) and design spiral load (dry tons per hour per start)."

Jan 1, 2017

By Neal Harries

The monitoring of rock slopes is a common procedure in the management of hazards associated with slope instability. Slope stability radar has become widely accepted as the state-of-the-art method for management of hazards associated with unstable slopes in open pit mines. This is confirmed by the rapid adoption of the technology since inception in mid 2003, with over 70 GroundProbe slope stability radars now in use at open pit operations throughout the World. The use of a monitoring system such as slope radar to identify slope hazards is only part of the solution to minimise the consequences associated with slope instability. The presence of the hazard must also be effectively communicated to the mine personnel, so that the correct response to the hazard can be enacted, and the risk mitigated to an acceptable level. In some surface mines, due to the geotechnical characteristics of the rock mass, hazards can develop rapidly; with slopes progressing from stability to ultimate collapse in just hours. In these situations, it is vital that efficient systems are developed to evacuate the area of the pit affected. Such a system has been developed by GroundProbe in South Africa, with the vital driving force for the project being provided by the Anglo Platinum Mogalakwena mine operation based at Mokopane. The mine based development of the system was perceived as an essential aspect in the development of the successful system. From an early stage, the mine provided essential input on both hardware and software developments to allow the system to be rapidly integrated into the mining operation. This paper describes the pit evacuation alarm system that was developed and discussed the benefits obtained from a mine based development program.

Jan 1, 2008

By N. C. Gay

The quantitative evaluation of the performance of fill materials placed in gold mine stopes is achieved by (i) measurement of the in-situ load- displacement, or stress-strain, characteristics of the materials; (ii) an objective comparison between the observed fill performance and that predicted from suitable computer modelling techniques; and (iii) objectively comparing conditions in backfilled and conventional stopes. Considerable problems have been experienced with the development of sufficiently robust instrumentation which can be installed within filled pad- docks and give reliable information over a long period of time. However, at most mines where backfill performance is being monitored, it has been possible to correlate stress measurements within the filled paddocks with strain measurements adjacent to the paddocks. The resultant stress-strain curves agree relatively well with those determined in the laboratory. Measurements in the hangingwall strata of filled and unfilled stopes indicate that the placement of fill does reduce the amount of inelastic convergence due to bed separation. Moreover, in some stopes, the rate of convergence with respect to face advance does reduce to that of the theoretical elastic convergence. Quantification of changes in the conditions at the stope face due to placement of fill has proved difficult. Observations indicate that, provided the fill is placed close to the face (- 5 m), and adequate temporary face support is used, conditions in filled panels are superior. In addition, in filled panels the damage caused by a rockburst in the stope and, particularly, in gullies is generally much less than would be expected in an unfilled stope. To quantify these improvements, parameters such as stope height, face advance and the frequency of falls of ground are being monitored.

Jan 1, 1988

By D. Bessinger, H. Kotzé, J. Beukes

Keywords: Pyrometallurgy, furnace, ilmenite, smelting, Ticor Ticor SA began with a detailed feasibility study in 1995. The Hillendale mine (situated between Richards Bay and Empangeni) and Mineral Separation Plant were approved in 2000. The smelter, just outside Empangeni, consists of two 36 MW DC arc furnaces that were commissioned in 2003. Experiences gained during the initial commissioning of the furnaces proved valuable in later commissioning work, as shown by the increase in ramp-up rates. The capacity of the plant is 250 kt/a TiO2 slag and 145 kt/a of pig iron.

Jan 1, 2006

Limestone formations in the United States can be subject to relatively high horizontal stresses due to the existence of tectonic loading of the limestone strata. Underground limestone mines use the room-and-pillar method, in which 12- to 18-m-wide rooms are typically excavated. The stability of these excavations can be compromised by the horizontal stress, resulting in a rockfall hazard. Rockfalls are the cause of 15% of all reportable injuries in underground limestone mines. Horizontal stress related damage can occur in the form of guttering along one or more sides of an excavation, roof beam buckling or oval shaped roof falls, with the long axis perpendicular to the major horizontal stress. Numerical analyses show that the pillar layout and orientation of the mine workings have an effect on the horizontal stress distribution within the roof. The effects of high horizontal stresses can be mitigated by orientating the heading development direction parallel to the maximum horizontal stress, reducing the number of cross-cuts and offsetting the cross-cuts to limit the potential lateral extent of horizontal stress related roof falls. The modeling approach described in this paper can be used as a tool to evaluate potential roof failure and optimize the stability of room and pillar layouts.

Jan 1, 2008

By K. A. Moxham

The ARM 1100 was described in a paper presented at the 6th International Symposium on Mine Mechanization and Automation in September 2001. It started operation underground at Rowland Shaft in early 2002. This paper covers the results of those trials that resulted in more than 1 100square metres of UG2 being mined.

Jan 1, 2004

By E. J. Magri, D. M. Hawkins

This paper deals with an experimental programme carried out with a gold analyser in the period June to September 1979 at Loraine Gold Mines. The results were found to be reproducible, with no overall or conditional bias when the measurements were compared with those obtained from chip samples. The standard error of estimation of a 3 m reef exposure, which was the sampling interval, can be reduced by a factor of 2,5 if the complete stretch is scanned, rather than the taking of one chip sample in its centre. Complete statistical and computational procedures were developed for the fitting of the normal-Iognormal model to observed analyser data and for the determination of the most likely gold grade for a particular analyser measurement. (This corection procedure is necessary since a significant number of negative analyser measurements can be observed.) Panel averages of uncorrected scans showed a small conditional bias relative to those of corrected scans. However, uncorrected panel averages can be used for on-the-spot decisions regarding whole panels. For standard calculations of ore reserves, use should be made of corrected scans. Under reasonable assumptions, the use of the detector in the selective mining of low-grade narrow reefs such as the Basal Reef at Loraine Gold Mines, when compared with the conventional chip-sampling method, can result in a saving of as high as R40 million in present-money terms over the life of a project. The difference could be even larger in a highly variable reef like the B Reef at Loraine Gold Mines.

Jan 1, 1987

By H. B. Prinsloo

Change management and training initiatives in remote rural settings in Africa are generally difficult to implement successfully due to factors such as varying levels of education, multiple nationalities and languages as well as cultures in one workplace. The challenge has always been the ability to implement change management and training initiatives that will have an impact despite these differences. Essentially this requires that the change and training interventions employed are applicable and should work well with a wide range of individuals sitting in one room ? in practice this can vary from semi-literate workers to engineers with PhDs. In this paper we will share the theory behind behaviour-based change management and training and present a case study that reviews an actual supply chain improvement and sustainability implementation at a Zambian copper mine. The case study explains the results achieved as well as the interventions employed to achieve these results in a multidimensional organizational environment. This paper is relevant to delegates who are faced with implementing changes or training in a similar mining environment. Keywords change management, behaviour-based training, learning style, P2P process.

Oct 1, 2013

By J. B. A. Solar Menéndez, M. A. Martínez Fidalgo, L. A. Alvarez-Santullano

1. ANTECEDENTS This present communication refers to the results of the research project entitled "Training in the correct use of chemical oxygen self rescue apparatus and also an analysis of apparatus autonomy", carried out under the auspices of the Specific Collaboration Agreement signed between the Industry Council of the Principality of Asturias (Spain) and INSALUD (National Silicosis Institute, Spain). The antecedents of this project lie in work undertaken by the National Silicosis Institute aimed at optimising efficiency in the use of chemical oxygen self rescuers through improvements in worker training. To be precise, by means of Agreements drawn up between the above-mentioned parties, a simulator was designed and incorporated as the basis of a training station within the " Fundación Barredo" of the Industry Council of the Principality of Asturias. This has been operative since the year 2001 and, up to the present, 2300 Asturian coal mine workers have been trained there. What prompted this activity was the observation of various errors in the use of the self rescuers, deriving from their innate characteristics, especially with respect to the sensation of discomfort - the high temperature and humidity of the breathed oxygen, resistance and inconvenience - and limited autonomy. It was precisely this insight that, in critical situations, lack of familiarity with the conditions of discomfort likely to be experienced during the evacuation process might lead to rejection of the equipment, with fatal consequences, that has justified the setting up of this training and simulation centre. The centre is able to provide all mine workers with the necessary training, and experience of the characteristic sensations experienced when using such equipment (Fig.. 1).

Jan 1, 2003

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 'average' (sic) Bantu mine workers is 3.0 l/min. What do the authors mean by 'average'? 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'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 'average' 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 'average' recruits. Thirdly, it seems to me that the authors are perhaps a little uncritical in their acceptance of the '50 per cent of maximum oxygen intake' 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 'optimum' levels of productivity under conditions of high muscular activity and considerable psychological stress is a lot more complicated than would appear from the authors' 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 'optimum' 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 'The mixture (of fine, medium-sized and bigger rocks) was considered to be representative of an average underground rock sample'. 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'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