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A method is proposed for the evaluation of the influence of grout prestressing systems on the support resistance offered by timber packs. It is shown that, in order not to reduce the load-carrying capacity of timber packs, grout prestressing systems need to be at least as stiff as a single timber rise. The method was used to establish strength specifications for the grout prestressing systems to be used under non-seismic and seismic conditions. For non-seismic requirements, the 24-hour grout strength needs to be at least 1,7 MPa, and the 7-day grout strength 4,9 MPa. The investigation showed that the proposed strength specification is realistic in the light of current grout-strength capabilities. For seismic requirements, the grout strength needs to be at least 4 MPa and 8 MPa to prevent extensive damage to the grout during seismic events with a peak velocity of 1m/s 3 m/s respectively.

Jan 1, 1996

By D. P. Roberts

This investigation aimed to simulate the experiments performed by Nic Gay (Gay, N.C.1976. Fracture growth around openings in large blocks of rock subjected to uniaxial and biaxial compression. International journal of Rock Mechanics and Minining Sciences and Geomechical Abstracts, vol. 13. pp. 231-243) on fracture growth around openings in blocks of rock subjected to uniaxial and biaxial compression, using the Elfen discrete element code. The results of the physical experiments indicated a number of trends that were successfully replicated in the numerical simulations, including crushing ahead of the face, the formation of a sub-vertical tensile fracture at centre-span, the formation of groups of fractures originating from the crushed face zone, the formation of large corner-to-corner fractures which precede sample failure, and linking of slot corner and sample corner fractures leading to sample failure. In addition, other features were apparent that were not reported by Gay. It is believed that these took the form of conjugate shear fractures (as reported by Gay in a previous paper) and other features that may have been altered or inhibited by the presence of pre-existing structure in the physical samples. It was found that the samples, though nominally made up of the same rock type, must have had significantly differing properties. The presence of pre-existing structures may have contributed to this discrepancy. Strain measurements from the physical experiments were reasonably well matched, except where the gauge lay directly in the path of advancing fractures.

Jan 1, 2012

By J. O. Claassen

"SynopsisMining value chains are dynamic systems and should be managed according to systemic flow-based principles. This includes a detailed focus on the impact of variable geological conditions on material flow, product quality, and production cost, visibility of the total mining system to operators and managers, as well as the synchronization of resources and activities in downstream processes. Thirty mining operations across the African continent were studied to establish to what extent systemic flowbased principles are applied in day-to-day operations. The study indicated that although most mining operations have identified the relevant geoprocessing variables, only a small number apply this information in a flow-based management approach. Most mining operators do not focus on developing a clear flow view of the mining value chain and on making it visible to operators and managers to enable them to optimally set and reset operations. Daily synchronization of geoprocessing variables is limited to a small number of variables, e.g. synchronizing ore hardness with drilling or milling requirements, in less than 30% of the operations evaluated. Operations where these principles have been adopted reported a noteworthy improvement in performance. The study indicates that notable potential exists in most of the operations evaluated to implement flowbased management principles, including geometallurgical principles. This can significantly improve value chain performance without exorbitant capital layouts and enhance ROCE. IntroductionObjective of the studyThe study seeks to establish to what extent systemic flow-based principles have been adopted in the southern African mining industry and the implications thereof. Specific attention is given to the importance of defining and managing geoprocessing dependencies (geological variables directly impacting mining and plant performance – the geometallurgical approach), establishing a flow view of the mining system, which typically includes a dashboard of the flow of ore/product quality and cost from the mining face to the customer, and limiting the impact of dependencies through synchronization of activities and resources, e.g. ensuring that a continuous miner does not wait for a roofbolter, or that reagent addition rates are matched with a specific ore/concentrate composition."

Jan 1, 2015

The industrial relations handbook, by A. Pons. Juta (P.O. Box 14373, Kenwyn 7790). 1989. "'"250 pp. Looseleaf binder. R180 + GST. Industrial laser materials processing. World Business Publications Ltd (4th Floor, Britannia House, 960 High Road, London N12 9RY, England). 1989. 180 pp. £310. Mining 1990. Longmans, Financial Times International Year Books, 1989. 592 pp. £90.00. Innovations in materials processing using aqueous, co/oid and surface chemistry, by F.M. Doyle, S. Raghavan, P. Somasundaran, and G.W. Waren (eds.). 300 pp. $125. Light metals 1989, by P.G. Camp bel (ed.). No. of pp. not available. $150. Process control and automation in extractive metalurgy, by R. Partelpoeg and D.C. Himmesoete. 225 $98. Process mineralogy VIl, by D.J. Carson and A.H. Vassiliou (eds.). 4oopp. $150. Super plasticity and super plastic forming, by C.H. Hamilton and N.E. Paton (eds.). 700 pp. $140. Supera/oys 1988, by S. Reichman, D. Duhl, G. Maurer, S. Antolovich, and C. Lund (eds.). 880pp. $99. Surface modification technologies, by T.S. Sudarshan and D.G. Bhat (eds.). 305 pp. $49. World survey of nonferous smelters, by J .C. Taylor and H.R. Traulsen (eds.). 365 pp. $90. Second Parsons International Turbine Conference. London, The Institute of Metals, 1989.270pp. £40. Mineral processing in the United Kingdom. London, Institution of Mining and Metalurgy, 1989. £25. Today's technology for the mining and metalurgical industries. London, Institution of Mining and Metalurgy, 1989. 623 pp. £60. 1989/1990 E&MJ international directory of mining. Chicago, Mining Information Services (P .0. Box 6500, Chicago, IL 60680, USA). 620 pp. US$95. Advances in project scheduling, edited by R. Stowinski and J. Weglarz. Amsterdam, Elsevier, 1989. 540 pp. Dfl. 270. Proceedings of the 3rd International Conference on Molten Slags and Fluxes. London, Institute of Metals, 1989. 335 pp. £38. Brochure on industrial screens. Obtainable from Philippe Lavernhe, Johnson Filtration Systems S.A., Z.I. Availes-en-Chatelerault, 86538 Naintre, France. 16 pp. Free. Numerical techniques, edited by P. Spiling. London, The Institute of Metals, 1989. 226 pp. £25. Phase diagrams of ternary iron aloys, Part 2, by V. Raghavan. New Delhi, Indian Institute of Metals, 1988. 360 pp. £95 (from the Institute of Metals, London). cas publications These publications are available from the Centre for Resource Studies, Queen's University, Kingston, Ontario K7L 3N6, Canada. Economic aspects of gold exploration: How much is too much, by B.W. Mackenzie and M. Dogget. 30 pp. $10.00. Mineral exploration and mine development potential in Ontario: Economic guidelines for government policy, by B.W. Mackenzie, M. Bilodeau, and M. Dogget. 180 pp. $25.00. Economic potential of base metal and gold mining in Newfoundland: Assessing the impact of regional developmentpolicy options, by B.W. Mackenzie, M. Bilodeau, and M. Dogget. 188 pp. $25.00. Publications of the AusIMM The folowing publications are available from The Australasian Institute of Mining and Metalurgy, P. O. Box 122, Parkvile, Vic 3052, Australia. Prepayment is required with al orders. The AusIMM 1989 Annual Conference 1989. $A 50. Mineral fuel alternatives and the greenhouse efect. July 1989. A$ 35. NQ gold '89. Apr. 1989. $A 50. Second Large Open Pit Mining Conference. Apr. 1989. $A 50. Explo '88. Nov. 1988. $A45. Mineral deposits of New Zealand, edited by Dr D. Kear. Monograph 13. 244 pp. $A 60. Field geologists' manual, compiled by D.A. Berkman. 3rd edition. 1989. : 350pp. $A45. The rocks speak. Essays in geology-some personal responses of a wiling listener, by Haddon F. King. 300pp. $A45.

Jan 1, 1990

By D. C. Krige

The estimation of the tonnage and grade of payable ore in a mine and the correct policy of selective mining based on such estimates, is of vital importance to the mining engineer it is surprising, therefore, that more attention has not been devoted on the Witwatersrand to the scientific improvement of mine valuation methods. At present these methods consist almost entirely of the application of simple arithmetic and empirical formulae guided by practical experience, and ignore the many advantages to be gained from a careful statistical analysis of the behaviour of the gold values. The science of statistics has expanded rapidly during the last two decades and its value as a powerful and indispensable tool is now recognized not only by research workers and scientists but also, ever-increasingly, by the commercial and industrial world. This being the case it is noteworthy that in a mining field such as the Rand with its highly developed and advanced mining methods, singularly little attention has been paid to the analysis of mine valuation problems on a modern statistical basis. This omission is even more striking when cognizance is taken of the wealth of sampling data concerning the gold ore which is available and of the far-reaching decisions and deductions constantly being based on such data. Some contributions have however been made from time to time towards the application of statistics to mine valuation on the Rand (References Nos. 7, 8, 9, 11, and 12), but none of these have been generally applied in practice and a systematic practical approach based on clearly deemed fundamental concepts still appears to be lacking. The object of this paper is, therefore, to define these statistical concepts and to indicate briefly the lines along which statistical methods can be applied profitability in solving some of the existing problems and in improving the general standard of mine valuation on the Rand For this purpose a knowledge of mathematical statistics is essential, but as this paper is primarily intended to provide the mine valuator with a practical introduction to statistical application in his field, the mathematics is confined to a short annexure, together with references from which details can be obtained.

Jan 1, 1994

By C. Musingwini, M. Mohutsiwa

"SynopsisCapital cost estimates are important in decisions on whether a project will be approved, mothballed, or abandoned. In South Africa, junior coal miners do not have extensive databases of historical projects from which to estimate capital costs. The purpose of this paper is to establish formulae that can be used for estimating capital costs of developing coal mines in a coal-producing country, using South Africa as a case study. The costs are estimated to an error of magnitude level of -30% to +50%, which is suitable for a concept study level, using a parametric estimation technique. The study uses data from completed coal mining projects from selected coal-producing countries. Three formulae are developed and presented for estimating capital costs of underground bord and pillar, surface shovel and truck, and dragline operations.IntroductionCapital cost estimates play a critical role in deciding whether projects will proceed, be delayed, or abandoned. It is therefore important that capital cost estimates are carried out accurately as determined by the estimation guidelines based on the level of estimation conducted (Shafiee and Topal, 2012). The lack of literature on estimation of capital costs in many coal mining countries is adversely affecting junior coal miners, since they do not have an extensive database of historical projects on which to base estimations. In South Africa, the difficulty in estimating capital costs is attributable to lack of publicly available data on completed South African mining projects (Hall, 2013)."

Jan 1, 2015

By Y. J. Cao

The purpose of this study was to investigate the flotation behaviour of unburned carbon in a cyclonic-static microbubble flotation column (FCSMC). The ash sample, collected from a power station in Guangdong province of China, was characterized by size analysis, X-ray diffraction, contact angle measurements, and X-ray fluorescence. The effect of the column flotation operating variables on the removal of unburned carbon from the fly ash was systematically studied. The feasibility of separating unburned carbon and ash was determined from the removal rate of unburned carbon (RUC) and loss on ignition (LOI). Within the range studied, the optimum diesel oil dosage was 1200 g/t, abies oil dosage was 600 g/t, pulp density was 20 per cent, superficial gas velocity was 1.4 cm/s, and circulating pressure was 0.20 MPa. The results indicate that the FCSMC technique is effective in removing the unburned carbon from the fly ash, which can be attributed to the generation of microbubbles and the continuous cyclonic circulation method. Under the optimized conditions, a cleaning ash with 2.13 per cent LOI and 94.21 per cent RUC was obtained.

Jan 1, 2012

By Kathryn C. Sole, Owen Tinkler

"Although the first large-scale application of copper recovery by solvent extraction (SX) took place in Zambia in the early 1970s, it is only in the last decade that this technology has become widely employed in this part of the world and is now a mainstay unit operation in most copper hydrometallurgical flowsheets. The mineralogy of the ores in the African Copper Belt, and hence the characteristics of the African leach liquors, differ significantly from those in Chile and the south-western USA, where copper SX has had a long and successful history. These differences provide operators, metallurgists, reagent vendors and engineers with many challenges: new approaches are needed to adapt this technology for successful implementation in this region. This paper examines typical operating practice in the African Copper Belt, discusses differences compared with other parts of the world and looks at some of the challenges and opportunities presented by these flowsheets. INTRODUCTION Following the success of the Rancher’s Bluebird and Bagdad solvent extraction and electrowinning (SX–EW) operations in Arizona in the late 1960s, the Tailings Leach Plant at Chingola, Zambia became the first large-scale copper SX plant in the world, commissioned in 1974. Despite the equipment design now being outdated, this plant still continues to operate successfully, indicating the versatility and adaptability of this technology. Today, there are some 75 copper SX operations worldwide with cathode production above 10 kt/a. The top ten producers currently account for some 40% of the global 4.3 Mt/a SX–EW copper production. South America (predominantly Chile and Peru) is the largest copper cathode-producing region, with annual production of some 2 Mt. The Central African Copper Belt (Zambia and the Democratic Republic of Congo (DRC)) is second, with cathode production of 1.2 Mt/a and North America (USA and Mexico) third, producing close to 0.8 Mt/a Cu (Cytec data, 2014). The remaining 0.35 Mt/a comes from all other regions combined (referred to as “Rest-of-World”). Current and future operations in Zambia and the DRC are summarised in Figure 1. The industry in this region is characterised by a large number of small (3 to 20 kt/a) plants, mainly Chinese-owned, and a few very large (>200 kt/a) operations, owned by major multinational corporations. This paper examines typical operating practice in the African Copper Belt, discusses the differences compared with other parts of the world and looks at some of the challenges presented by the conditions, as well as innovations in flowsheets, reagents and operating conditions that have been introduced in these circuits."

Jan 1, 2015

By S. Burks

This paper develops the themes explained at the previous SAIMM Platinum conference by Whittle and Burks1. Optimization techniques can be used to significantly increase the value of mining businesses by enabling better long- term planning decisions. Open pit and underground mine design, mine scheduling, cut-off grade and blending, stockpiling, and the linking of these to flexible elements of the metallurgical recovery processes are all evaluated together. Transport or sale of intermediate products and the requirements of the product metal markets can also be considered. Experience shows that net present value (NPV) can potentially be increased by 5-35 per cent or more, usually even before the expenditure of significant amounts of project capital. The case studies presented include: ? An existing operation with multiple open pits and PGM concentrators linked to offsite downstream processing facilities, and with infrastructure constraints for which the scheduling of current operations and the potential for expansion were investigated ? An existing operation with an integrated portfolio of mines, concentrators, smelter and refinery, for which the various possible sources of ore for processing were prioritized to match the downstream process plant constraints and the product markets ? An underground operation in Zimbabwe for which the optimum mining width was calculated and expansion plans were evaluated ? An underground mine with many separate mining sections, for which a revised schedule was developed aiming to keep the shaft system and processing plant at capacity with the highest net value material available at any time throughout the life of mine. In the concluding section of the paper, a few brief notes are included suggesting how the strategic recommendations from enterprise optimization studies may be implemented by the Owner?s team.

Jan 1, 2012

By O. S. Tinkler, K. C. Sole

"Although the first large-scale application of copper recovery by solvent extraction took place in Zambia in the early 1970s, it is only in the last decade that this technology has become widely employed in this part of the world and is now a mainstay unit operation in copper hydrometallurgical flow sheets. The mineralogy of the ores of the African Copperbelt, and hence the characteristics of African leach liquors, differs significantly from those in Chile and the southwestern USA, where copper solvent extraction has had a long and successful history. These differences provide operators, metallurgists, reagent vendors, and engineers with many challenges: new approaches are needed to adapt solvent-extraction technology for successful implementation in this region. This paper examines typical operating practice in the African Copperbelt, discusses differences compared with other parts of the world, and looks at some of the challenges and opportunities presented by these flow sheets. IntroductionFollowing the success of the Rancher’s Bluebird and Bagdad solvent extraction and electrowinning (SX–EW) operations in Arizona in the late 1960s, the Tailings Leach Plant at Chingola, Zambia, became the first large-scale copper SX plant in the world, commissioned in 1974. Despite the equipment design now being outdated, this plant still continues to operate successfully, indicating the versatility and adaptability of this technology. Today, there are some 75 copper SX operations worldwide with cathode production above 10 kt/a. The top ten producers currently account for about 40% of the global 4.3 Mt/a SX–EW copper production. South America (predominantly Chile and Peru) is the largest copper cathodeproducing region, with annual production of some 2 Mt. The Central African Copperbelt (Zambia and the Democratic Republic of Congo (DRC)) is second, with cathode production of 1.2 Mt/a, and North America (USA and Mexico) third, producing close to 0.8 Mt/a Cu (Solvay Cytec data, 2014). The remaining 0.35 Mt/a comes from all other regions combined (referred to as ‘Rest-of-World’)."

Jan 1, 2016

By M. -B. Kime

This study applies attainable region analysis to optimise cobalt recovery from oxidised ores via reductive leaching with sulphur dioxide and sulphuric acid. The attainable region framework enables systematic visualisation of trade-offs between cobalt yield and sulphur dioxide loss, guiding reactor network design beyond conventional mass balance modelling. Experimental column leaching trials, supported by validation runs, were conducted under controlled flow and reagent conditions. Kinetic parameters for cobalt dissolution and sulphur dioxide consumption were used to simulate reactor trajectories and construct attainable region envelopes. To ensure hydrodynamic realism, residence time distribution tests confirmed partial plug flow behaviour with dispersion effects, justifying the use of hybrid reactor models in the attainable region simulations. The results revealed that increasing recirculation ratios improves cobalt yield while reducing sulphur dioxide losses, with attainable efficiencies exceeding 90% cobalt recovery and < 20% sulphur dioxide loss. Importantly, the study proposes practical reactor network configurations for future implementation, including staged percolation columns with intermediate mixing zones, oscillatory flow reactors, and modular fluidised bed systems. These designs offer scalable pathways to translate attainable region-based optimisations into industrial practice. Compared to traditional modelling, attainable region analysis provides a geometric decision support tool that captures multi-objective trade-offs and reactor interactions, offering novel insights for continuous leaching system design. This work advances the application of attainable region methodology in minerals engineering by bridging theoretical optimisation with practical reactor design, supporting sustainable cobalt recovery from both primary ores and recycled feedstocks.

Mar 30, 2026

By D. Weijie, S. Kai, Y. Hu, X. Ning, M. Shiyi, W. Junpeng, Z. Guihong, L. Xianjie

Flotation is one of the most important processes in the copper production industry. The copper grade in the concentrate is a pivotal indicator of the flotation process performance. However, it is difficult to achieve real-time measurement through hardware sensors. Based on the production data provided by an industrial operation, a novel soft sensor based on multi-layer perceptron (MLP) is proposed for effective monitoring of this pivotal indicator. The proposed soft sensor uses the nonnegative garrote (NNG) to perform global variable selection for MLP, while a local search (LS) approach is incorporated to improve the model presented by NNG. Simulation results show that the proposed algorithm has higher prediction accuracy and better model simplicity than other algorithms. Furthermore, the variables selected are consistent with the field experience, and the developed model can provide reference of feedback control for the optimisation of the process. Keywords: Flotation process of copper ore, nonnegative garrote, local search, soft sensor, multi-layer perceptron

Jan 1, 2020

By D. Orynbassar, N. Madani

This work addresses the problem of geostatistical simulation of cross-correlated variables by factorization approaches in the case when the sampling pattern is unequal. A solution is presented, based on a Co-Gibbs sampler algorithm, by which the missing values can be imputed. In this algorithm, a heterotopic simple cokriging approach is introduced to take into account the cross-dependency of the undersampled variable with the secondary variable that is more available over the entire region. A real gold deposit is employed to test the algorithm. The imputation results are compared with other Gibbs sampler techniques for which simple cokriging and simple kriging are used. The results show that heterotopic simple cokriging outperforms the other two techniques. The imputed values are then employed for the purpose of resource estimation by using principal component analysis (PCA) as a factorization technique, and the output compared with traditional factorization approaches where the heterotopic part of the data is removed. Comparison of the results of these two techniques shows that the latter leads to substantial losses of important information in the case of an unequal sampling pattern, while the former is capable of reproducing better recovery functions.

Aug 1, 2021

"This study examines the problems faced by open pit mine superintendents who make choices about how to direct their materials, either to the waste dump or to the mill. The paper explores the effects of introducing a 10% sampling error and a 0.9-times to 1.1-times sampling bias on positively skewed distributions for precious and base metals, negatively skewed distributions in the case of bulk commodities, and normal distributions as is the case for coal deposits. Parent distributions for each commodity were created on a 25 x 25 m grid using transformations of gold, iron ore, and coal data-sets, spatially based on a nonconditional Gaussian simulation. Ordinary kriging of grades for the three commodities into a 10 x 10 m grid provided the reference case against which the distributions with the sampling error and sampling bias for the commodities were compared. Imposing cut-off grades on the actual-versus-estimated scatterplots of the three commodities allowed the distributions to be classified into components of waste, dilution, ore, and lost ore. Ordinary kriging of values for each deposit type acted as the reference data-set against which the effects and influence of 10% sampling error and 0.9-times to 1.1-times sampling bias are measured in each deposit type. Indications are that the influence of error and bias is not as significant in gold deposits as it is in iron ore and coal deposits, where the introduction of small amounts of error and bias can severely affect the deposit value.IntroductionThe effects of poor sampling and the financial implications for mining companies, traders in mineral assets, and sellers of metal as dore or commodities is documented in a number of studies, the most notable of which is that by Carasco (2004). He examined the financial impact of poor sampling practices in the Chilean copper industry and found that finacial losses due to poor sampling amounted to hundreds of millions of dollars over the life of a mining operation. Holmes (2004) examined the effects of correct sampling and measurement as the foundations of metallurgical balances, and found that revenues from the sales of large iron ore shipments may be profoundly affected by poor sampling practices. In South Africa the way in which sampling of in situ gold-bearing reefs affects the mine call factor has been an ongoing study since the disparity between the estimation of gold in the reef and the actual gold bullion produced was noted by early investigators such as Beringer (1938), Jackson (1946), Sichel (1947), Harrison (1952), and a number of others."

Jan 1, 2017

Dr Hanekom I would like to thank Dr Hanekom for a very valuable -contribution; it summarizes careful statistical test work which was an omission from the original paper. Minor manipulative details, the application of a finer measuring graticule and the reproducibility of the procedure are described and the author accepts with gratitude this ready-made answer to the first and second points of Dr Finkelstein&apos;s comments. Mr Williamson The author is indebted to Mr Williamson for historical background to early experiments with captive bubbles and it is conceded that the original paper described another avenue to an old flotation goal. The field of application is restricted and we would not work with all the material illustrated by Klassen and Mokrousov.1 The particles in Figure 74(a) are far too large and irregular; material in Figures (b) through (d) could be employed for semi-quantitative work in spite of obvious disadvantages; Figure 74(f) represents ideal conditions. We have studied this mineral-collector association in the size range given and results were satisfactory. For larger pick-up values than that illustrated an induction period of more than 0.01 second was required (actually 90 seconds for a maximum bubble load at pH 7.2 with 25 g/t oleic acid!). REFERENCE 1. KLASSEN,V. I. ANDMOKROUSOV,V. A., &apos;An Introduction to the Theory of Flotation,&apos; Butterworths, London, 128, Figure 74, (1963). Mr Slander and Mr Kooij Researchworkers in a practical mineral development laboratory may well ask what contribution yet another micro-technique can make to the problems of large scale ore flotation. The obvious answer is that there can be little or no direct translation of results obtained with a static system comprising air bubble and pure mineral concentrate to a dynamic multicomponent operation. However, for the rapid study of one mineral or variable some small scale apparatus must be employed. In the Anglo American Research Laboratory, the described semi-quantitative pick-up technique has filled a niche and requirement. For ourselves, the system represents a definite advance over the contact angle approach in that samples of minerals conventionally prepared in laboratory or plant may be used, which is a desired step nearer flotation. We bracket this pick-up apparatus with the Hallimond tube1,2 and evidence is now to hand that pick-up curves may often be related to flotation recoveries obtained from this tube with pure mineral samples and from the Fuerstenau glass cell3 with the total ore at low pulp densities. We would not wish to push the comparison of pick-up results past this stage for there is much published development work relating the Hallimond and Fuerstenau equipment to flotation on a larger scale. At the Anglo American Research Laboratory for example, a test in a Fuerstenau cell is often the final integrated step in laboratory investigations into the TORCO process. As these contributors rightly point out, pick-up tests can offer nothing towards the determination of optimum reagent dosage for large scale flotation. This is the function of bench-type flotation cells with up to 2 kg batches of ore. At this level, collector performance and consumption and physical properties of the froth are more comparable with large scale operation. The pick-up cell, Hallimond tube and Fuerstenau cell are essentially equipment from which the effect of control parameters can be derived. For the assessment of collector behaviour, the pick-up approach is rapid and economic and we offer here a pick-up contribution towards the flotation of Witwatersrand uraninite with anionic sulphonate collectors (Fig. 1). A large crystal of the local mineral was not available for contact angle measurements and owing to its low concentration in Witwatersrand gold-bearing reef, a small sample was laboriously obtained by tabling, superpanning and heavy medium separation. The pick-up values of a sized portion were determined by the described procedure in the presence of nine petroleum sulphonate collectors. Responses fell into two categories; "normal" curves (dotted lines) and a group of collectors which were very active at low concentration but showed depression of pick-up at the higher levels. The similarity in form of curves for collectors 1 and 3 was apparent and reagent 3 was found to be simply a diluent of 1. Otherwise, collector performance could not be related to either sulphonate content or molecular weight of the active constituent. However, reagent 2 gave the best performance in a bench flotation cell with regard to overall uranium distribution but, as predicted, reagent 1 yielded the best grades. Later pick-up tests with a similar class of collector have suggested that depression at high reagent concentrations may be due to "bubble armouring" whereby an hydrophilic air-liquid interface is produced which rejects mineral attachment. Prolonged investigations with the same mineral sample have not been required except for the study of uraninite which lasted for more than a year. Variation in pick-up response could not be detected over this period during which the mineral was stored under distilled water. The only visible change was a small efflorescence of lead sulphate, readily removed and decanted off after stirring with a glass rod in the sample tube. In its main role as a "trouble-shooter", the pick-up method is applied to fresh mineral samples taken from a flotation plant and soon discarded or from a current run in the ore-dressing laboratory. After production of a concentrate, a solvent cycle, as described in the original paper, may be required to remove heavy organics or other contaminants as when a sample has been taken from circuits containing detergents, grease or return flotation solutions. This solvent cycle will not remove chemisorbed collectors and we prefer not to work with minerals from flotation tailings or with pick-up cell discards. It has been thought preferable to answer the contributors&apos; other apprehensions with regard to sample preparation, activators, depressants and the physical properties of reagents in another paper on offer to this Journal. It covers pick-up investigations relating to the flotation of nickeliferous pyrrhotite at two Anglo American Corporation Mines, which approach seemed the correct orientation for a reply to another contributor to this paper.

By M. Royle, A. Bloem, R. Uken

Rock mass damage induced by mining increases the fracture frequency and joint aperture width in the pit walls and rock mass behind open pit mine slopes. The depth and intensity of this mechanical damage relative to the pre-mining state is not well understood and yet is a major factor in the development of slope stability models and operational guidelines. The induced damage can be partitioned into domains or zones. The blast damage zone is essentially a ‘free flow’ rock mass volume, which transitions quite rapidly into the excavation damage zone, which extends beyond that. In both zones, transient high in situ water pressures are often linked to unstable slope conditions. Whereas rock damage can enhance passive depressurisation in the rock mass, high infiltration rates on the other hand, as one could expect during rainstorm events, will decrease slope stability within the dilated pit rock mass, especially in the blast damage zone-excavation damage zone, by increasing pore pressures for short periods of time. Ice jacking and freshet are additional factors to consider in (sub) arctic environments and can be exacerbated by unfavorable rock fabric orientation. On a local scale, brittle deformation damage zones, in the form of faults, can contribute to slope instability, or enhanced stability because of slope depressurisation, depending on their location and orientation relative to the pit shape and the water sources. In this study, the shapes of the damage zones and their anticipated impact on infiltration and/or passive depressurisation are considered for different pit morphologies, rock mass conditions, in situ stress, and hydrogeological settings. Some unusual hydrological situations, like mining towards rivers and lakes and the potential effects on pore pressures, are also considered. This investigation has resulted in the development of a method to adjust initial hydraulic conductivity values used to estimate transient pore pressure conditions found in rock masses exposed in different pit morphologies and stress regimes as well as discontinuities’ orientation relative to open faces within the open pit mine. The changes in K values and pore pressures can then be used to determine hydrogeological influence more accurately on future pit slope stability.

Sep 1, 2025

By M. Wu, X. Zhao

This paper presents an integrated pipeline transport system for thickened coal sludge, which combines pretreatment and pipeline transport with combustion techniques of thickened coal sludge. The pipeline can transport thickened coal sludge with a sufficiently high solids content (about72%?77%) and high apparent viscosity (about 1 000Pa?S?3,000 Pa?S) directly by pipeline having neither use for water nor an addition agent. The transport distance can be as high as 1 000 metres. In particular, the operating principles, key equipment and technical parameters of this integrated system are examined in this paper. The integrated system effectively causes no pollution to the environment because it is completely sealed, and conserves energy over traditional conveyer designs. Keywords: pipeline transport; integrated system; circulating fluidized bed boiler; thickened coal sludge; high solids content

Jan 1, 2007

By J. N. Van der Merwe

Due to the approaching depletion of reserves in the Witbank Coalfield, and the fact that the Waterberg Coalfield is as yet under developed, there is increasing pressure to extend the lives of the operating coal mines in the Witbank Coalfield. One potential source of coal is the old pillars, often small and at shallow depth, that were not left with secondary extraction in mind. At face value, some of these pillars appear to be suitable for secondary mining due to their high safety factors. However, it is known that over time, these pillars have scaled and the current sizes are smaller than the as-mined dimensions. It is also known that at shallow depth, the overburden is often less likely to fail during secondary mining, resulting in high abutment loads on the unmined pillars. The paper proposes a systematic method to pre-evaluate those old pillars for the possibility of stooping. The method consists of elements of fundamental methods and newly developed technology. In essence, it revolves around using empirical methods to estimate current pillar dimensions, followed by numerical modelling to investigate the probability of progressive pillar failure and then fundamental methods to determine the limits of applicability of the numerical model.

Jan 1, 2012

By L. Naude, J. Cloete, S. Engelbrecht

The results of an investigation evaluating whether an industrial plant, currently operating using sodium isobutyl xanthate (SIBX) as primary collector for sulphide minerals (mainly chalocopyrite), could adapt to operate using an alternate primary thiol collector without compromising plant and metallurgical performance. Initial laboratory scale flotation tests identified commercial dithiophosphate (DTP)-based and thionocarbamate (TC)-based collectors, that when blended, showed potential to replace the incumbent SIBX primary PGM collector. Industrial plant trail results show that there was no deterioration in recovery of 4E PGMs, even at a lower concentrate grade when operating the plant on the identified (DTP + TC)-based collector blend compared to SIBX. The effect on Cr2O3 content in the final concentrate was also found to be negligible. The (DTP + DTC)-based collector blend also showed promise in terms of plant adaptability in accommodating a new primary specialty collector blend. These observations highlighted the potential of replacing xanthate primary collectors with alternate thiol collector blends for PGM flotation. Keywords: PGM, xanthate replacement, specialty collector, sodium iso-butyl xanthate (SIBX), dithiophosphates (DTP), dithiocarbamates (DTC)

Jan 1, 2020

By Richard Peaker, Jens Lichter, Alexander V. Potapov

The recent combination of Computational Fluid Dynamics (CFD) and Discrete Element Modeling (DEM) can provide considerable insight into the performance of flotation cells. One area of interest from a fundamental equipment design perspective has been the influence of flotation cell size and the inflow rate on the metallurgical performance of the cell. One of the specific design objectives when increasing the size of flotation cells, or increasing the feed flow to the flotation cell, is to ensure that the feed stream flowing into the cell does not have an opportunity to bypass the mechanism. This paper describes the initial modeling efforts to quantify the inter-relationship of cell size, inflow rates, and feed and discharge box placement, on the retention time distribution of solids in the flotation cell, and the fraction of particles that bypass the mechanism on a size by size basis.

Jan 1, 2007