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By I. Bock

Selective Blast Mining (SBM) makes use of milli-second sequential blasting technology to separate the valuable reef material from waste rock in the blasting operation at stope faces in the mining of tabular ore bodies such as exist in the gold and platinum mines in South Africa. The waste rock is cast blast to the back of the stoping area, and the reef material is fractured and deposited close to the stope face. Only the reef material is transported to the surface. A simplified economic model is presented to evaluate the economic benefits of SBM. Although premature, in that adequate experimental demonstration of the validity of the model has not yet been possible, the model is presented since it indicates substantial benefits in the case of narrow reef gold mines. It is suggested that many marginal mines should seriously consider SBM. Benefits can also be realised in platinum mines, but a lot more experimental work is necessary to establish cost parameters more reliably. Some practical experience in the use of SBM in the mining of the UG2 reef is presented.

Jan 1, 1998

By B. J. Madden

Over 206 million tons of hard coal were mined in South African collieries in 1996. Some 132.5 millions tons came from underground operations and approximately 120 million tons came from bord-and-pillar workings resulting in between 100 000 and 150 000pillars being formed. Coal pillar design remains a significant feature of South African mining. This paper reviews South African coal pillar design procedures in the light of 90 pillar collapses that have occurred since 1904. It shows that, while the current pillar strength formula is still valid within the original empirical range of Salamon1,cognisance must be taken of local conditions. Current South African coal pillar research is attempting to account for the variations in local conditions with the emphasis on the effect of discontinuities and pillar deterioration. It is suggested that a more holistic approach to pillar design be adopted to include a design methodology that examines the stability of the roof, pillar and floor of the underground workings. Using this approach, deviations from the empirical database used by Salamon and Munro will be incorporated into the design methodology resulting in more stable underground workings.

Jan 1, 1998

By D. S. van Vuuren

Over the last 60 years many different processes were conceived to reduce the cost of titanium produced by the Kroll process. However, success eluded all previous efforts, which were consequently terminated in periods of economic downturn. Recently, the grow thin demand for titanium and the high cost of producing the metal again sparked renewed attempts in various parts of the world to replace the antiquated Kroll process with a more efficient route. The different options to produce titanium are reviewed, classified and evaluated in terms of the fundamentals underlying the technologies, and it is shown that the options considered to be the most likely to replace the Kroll process, are continuous processes to reduce TiCl4 metallo-thermically to titanium powder. Of these, continuous magnesio-thermic reduction of TiCl4 would conceptually result in the lowest-cost and highest-value product. However, when considering by-product salt removal from the titanium product and recycling of the salt as well, sodio-thermic reduction of TiCl4 is better.

Jan 1, 2009

By B. Simser

Rockbursting around underground excavations continues to be a core risk for many deep mining operations. Numerous advancements in mine design, preconditioning, monitoring, mining equipment, exclusion zones, and ground support have significantly lowered the risk to mine workers. As mining continues in deeper, more challenging environments, a multitiered approach to rockburst risk mitigation, starting with mine design, is required. Both the overall mine sequence, for example, avoiding converging mining fronts, and local design “stick handling” can play an important role in risk reduction. Rockburst case studies dating back to the late 1990s up until 2024 are used to highlight risk factors and risk mitigation (tactical and strategic). Examples from several deep hard rock mines are used, generally in high horizontal stress fields (k ratios 1.5 to 2), and strong brittle rock (> 200 MPa unconfined compressive strength). Mining induced stresses as well as high in situ stress due to depth are discussed. The context is Canadian mining, which typically has highly mechanised operations, large openings and equipment. Examples from a narrow vein mine and shaft sinking are also given because neither environment is simple to mechanise, highlighting the need for other risk mitigations. A “sieve” analysis based on mine incident reports is used to show how a multi-tiered risk management plan can lower exposure to violent ground failures. A few incidents still make their way through the “sieve,” indicating a need for further improvements. Thoughts on future/ current developments, and their strategic importance are given. Ground support is the last line of defence. The proliferation of multiple styles of yielding tendons and support systems has made many choices available to rock engineering professionals. Despite the increased availability of dynamic ground support components, there are still difficulties getting clean load transfer to bolts, determining support demand, monitoring loss of capacity over time/mining, and evaluating true system capacity. Virgin development in deep high stress brittle rock can result in high strainburst exposure prior to any stoping operations. The mining process must reduce worker exposure to unsupported rockmasses. Successful preconditioning in a shaft sinking operation, the use of high early strength shotcrete, and mechanised equipment are also discussed.

Nov 24, 2025

By G. D. Buson

Driefontein Consolidated Limited has a proud history in the South African gold mining industry dating back to March 1945 with the formation of the West Driefontein Gold Mining Company. The reclamation gold plant at West Driefontein was originally built as a uranium recovery plant in 1970. With the collapse of the uranium oxide yellow cake market, the uranium plant was closed in 1988and successfully converted into a gold plant, recovering gold from repulped tailings dams1. The West Driefontein Reclaim plant utilized milling, leaching, conventional rotary vacuum filtration and cementation to recover the gold at a rate of 200,000 dry tons per month. The No. 1 tailings dam (at a head grade of 0.8 Au g/t) began to near the end of its life during 1996, and the next slimes dams to be treated, the No. 2tailings dam (at a lower head grade of 0.56 Au g/t) was found too marginal for reprocessing using the filtration technology. Alternate technologies were investigated, particularly the carbon-in-pulp (CIP) plant based on the Anglo-American Corporation (AAC) pump-cell technology at the Vaal Reefs Exploration and Mining Company?s East gold plant which was operating profitably at lower head grades2. The AAC pump-cell technology is based on the carousel mode of operation2. The suitability of CIP technology for the West Driefontein Reclaim plant was investigated using a pilot plant pump-cell supplied by Kemix The data gathered were utilized in sizing a full scale AAC pump-cell plant. This plant was motivated, built and commissioned on the 22nd of November 1996. Incorporating 6 eighty cubic metre AAC pump-cells. The West Driefontein Reclaim plant initially treated repulped slimes dam material. A subsequent change of feed material to current arisings (from the main gold plant) occurred in1997 in order to convert mills for waste rock treatment. Currently the reclaim plant treats a combination of current arisings and waste rock (milled at the reclaim site). The new CIP plant replaced twenty-seven rotary vacuum filters. A comparison between the filters and CIP in terms of operating costs was undertaken, as well as a performance analysis of the CIP plant to determine its flexibility in terms of variation of the throughput, pulp density, gold input, leaching efficiency prior to CIP, and the rate of carbon movement.

Jan 1, 1999

By Org de Wet

This paper summarises the strategy for selection between a two module coal plant incorporating large, but less equipment, and a three module coal plant with more but smaller equipment. The two options were evaluated in terms of three main categories: ? Size ? size of the equipment and the effect on the process efficiency as well as the difference in physical dimensions of the plant to accommodate the larger equipment; ? Cost ? capital savings between a two and a three module plant, processing the same ROM (run-of-mine) tons per hour (t/hr); and ? Practicality ? in terms of constructability of the plant, safety of using larger equipment and maintainability of the equipment. Decisions that were taken to reduce the risk associated with size, cost and practicality on the chosen option of a two module plant will be highlighted.

Jan 1, 2006

By X. W. Pan

It has been found that the MnO content of a slag decreases sharply when direct current is applied to a 1T1£tal-Slagsystem consisting of liquid Mn-Si-Ccsat metals and MnO-SiO2-CaO-AI203 slag in graphite crucibles. This paper reports a preliminary investigation into the electrochemical effects of direct current on the metal-slag system, the silicon content of the metals, and the MnO content of the slag. The results show that, when a direct current of 7 A is maintained, the MnO content of a metal containing 10 to 11 per cent silicon by weight is reduced rapidly from 26,5 to 17,2 per cent by weight. This reduction seems to proceed further when the process is continued. When the direct current and the voltage are kept constant at TA and 4 V respectively, the MnO content of a metal containing 1 to 2 per cent silicon by weight is reduced to 1 from 25 per cent by weight, which results in a manganese yield of 96 per cent.

Jan 1, 1995

By A. P. Squelch

The question of what stress condition exists in the hangingwall of tabular stopes remains topical and largely unanswered. Limited field data exist to quantify the situation and provide calibration for investigative computer modelling exercises. Work conducted in1989 and 1990 under a Chamber of Mines Research Organization (now the CSIR: Division of Mining Technology) programme of research into the behaviour and benefits of backfill may assist with this situation. The original work was motivated by the premise that the improved hangingwall stability in backfilled panels (identified by rockfall accident analyses) is due to a change in the hangingwall stress regime. Current, largely theoretical, studies into mechanisms of stope hangingwall behaviour and support interaction could benefit from considering these data. Keywords: Backfill, horizontal stress, stope hangingwall, hangingwall stability, support interaction.

Jan 1, 2002

By A. Feather

Avmin have developed a flowsheet for the refining of copper, nickel and cobalt from Nkomati concentrates. Cobalt is recovered from calcium-saturated solution using Cyanex® 272. Nickel is subsequently extracted using versatic acid. The loaded organic is stripped using spent electrolyte, producing advance electrolyte for recovery of nickel by electrowinning. Cobalt was recovered with >99.5% extraction efficiency, reducing cobalt from 1.8 g/l to <10 mg/l. The cobalt/nickel ratio in the cobalt product solution was >1500. Nickel solvent extraction was optimized to recover 99%, reducing the nickel concentration from 32 g/l to <0.3 g/l, while minimizing calcium deportment to the nickel electrowinning circuit.

Jan 1, 2002

By H. Jang, Y. Kawamura

Unplanned dilution and ore loss directly influence not only the productivity of underground stopes, but also the profitability of the entire mining process. Stope dilution is a result of complex interactions between a number of factors, and cannot be predicted prior to mining. In this study, unplanned dilution and ore loss prediction models were established using multiple linear and nonlinear regression analysis (MLRA and MNRA), as well as an artificial neural network (ANN) method based on 1067 datasets with ten causative factors from three underground longhole stoping mines in Western Australia. Models were established for individual mines, as well as a general model that includes all of the mine data-sets. The correlation coefficient (R) was used to evaluate the methods, and the values for MLRA, MNRA, and ANN compared with the general model were 0.419, 0.438, and 0.719, respectively. Considering that the current unplanned dilution and ore loss prediction for the mines investigated yielded an R of 0.088, the ANN model results are noteworthy. The proposed ANN model can be used directly as a practical tool to predict unplanned dilution and ore loss in mines, which will not only enhance productivity, but will also be beneficial for stope planning and design.

Jan 1, 2015

By Chandrakala Kari, S. Mohan Rao, Gajanan Kapure, K. S. Raju

High carbon ferrochrome production process is energy intensive, consumes approximately 3300-3400 kWh per ton of metal produced. This amounts to ~ 34% of the total ferrochrome production cost. The power costs in India are almost 4 times greater than the leading ferrochrome producing countries like South Africa. Hence there is a need to look for alternative sources of energy. In ferrochrome making process large volumes of high concentration CO gas (~ 85%V) is developed at ~400-5000C, which if combusted within furnace represents high potential for significant electrical energy savings. In a typical heat in the state-of-the-art submerged arc furnace, about 34 kmol of CO gas is generated per ton of ferrochrome metal, which, if post combusted to CO2, represents 7620 MJ of energy. Post combustion of the evolving CO (and H2) gas to CO2 can be achieved by providing additional oxygen before the generated CO gas leaves the furnace. In this paper, a concept of post combustion in submerged arc furnace as potential source of significant electrical energy saving in ferro-chrome making process has been explored. The prospects and limitations of the same are discussed. The value of this paper lies in its attempt to explore the post combustion application to submerged arc furnace with an objective of significant reduction in electrical energy consumption in ferrochrome production process.

Jan 1, 2007

By R. M. Franz

This paper considers potential risks to the health of workers in ultra-deep mines, including barotrauma, physiological effects and toxicity of airborne pollutants. Relevant previous research is reviewed, including work by the Chamber of Mines Research Organization and the Deep Mine Cooperative Research Programme, and recommendations are offered for prospectively limiting pressure-related health risks.

Jan 1, 2005

In exploiting the ultra-deep, narrow reef ore bodies of the Witwatersrand, the ventilation and cooling systems within the stopes play a critical role because of high concentrations of active workers. This paper examines the heat, ventilation and cooling effects of a number of different stoping layouts for narrow reef mining in ultra-deep operations in very hot rock. The stope ventilation and cooling needs are driven primarily by the difference between the air temperature and that of the rock front being excavated. These needs depend on the face utilization, geometry, face advance (rate and direction), layout, backfill, use of water and machinery1,2,3. Detailed studies of different stoping configurations have been undertaken for mining operations extending to depths of 5000m below surface, where virgin rock temperatures approach 70°C. Extensive work has been completed with regard to evaluating ventilation and cooling requirements to maintain air reject temperatures of 28°C wet-bulb and better. This knowledge is being used to determine overall cooling requirements, reduce operational costs and maximize the efficiency of cooling systems. These issues are important when considering both the local and regional air conditioning systems and the most effective application of in-stope chilled water.

Jan 1, 2001

By F. T. Cawood

Monitoring of the slopes of surface mines can prevent loss of life, loss of equipment, loss of production and possibly the loss of the mine. The effectiveness of such monitoring depends on the extent to which slopes give adequate advanced warning before failing, and on the ability of the monitoring system to detect such warning. In this paper an overview is given of slope monitoring requirements, from both the geotechnical and survey points of view, as well as the types of equipment and instrumentation that are available. Legal issues relevant to slope monitoring are also dealt with. It is concluded that conventional geotechnical and survey instrumentation will continue to have their place in slope monitoring. However, the slope monitoring scene has changed substantially in recent years. A real and volume-based monitoring equipment is now available and this has provided, and will continue to provide, the means to improve safety, and to enhance productivity in mining. Its benefit to slope management is substantial. In the near future it is expected that data obtained from such equipment will add a much needed new dimension to slope engineering, and be used to improve slope designs and to optimize slope angles.

Jan 1, 2006

By N. Singh

Merensky Reef is mined extensively within the Bushveld Complex. In previously mined-out areas on the Merensky Reef horizon there are pillars, potholes and remnants that have not been mined. These unmined blocks of ground on the Merensky Reef horizon can influence the mining of the underlying UG2 Reef. The extent of the influence will depend on the size of unmined ground and the middling between the two reef horizons. This paper quantifies the influence of partially extracted Merensky Reef on mining of the UG2 Reef, and aims to provide recommendations for mining strategies, as well as regional and local support to achieve efficient and safe extraction of the UG2 Reef, for various middlings beneath the Merensky Reef horizon. In some cases it was found that relatively shallow UG2 Reef mining could encounter conditions similar to those experienced in deep and ultra-deep mining environments.

Jan 1, 2005

By B. Samanta

A quality characteristic analysed through construction of the Shewhart control chart is required to be normally distributed. In mining applications, this assumption is often violated as many quality characteristics follow skewed or lognormal distribution. In this paper, two methods were investigated using a heuristic approach for setting up the control limits for a skewed population. Based on these approaches a Mode chart, and a Weighted Variance (WV) control charts were constructed. The performance of the proposed methods was compared with the normal based Shewhart method through a case study conducted in a surface mine supplying iron ore to a steel plant. A simulation study was also conducted to evaluate the effectiveness of the proposed methods over the Shewhart method. The study revealed that the Shewhart control charts generated more out of control alarms compared with the Mode and Weighted Variance control charts for a skewed population of Fe%. The simulation results also revealed that for extremely high skewed population, the WV control chart and Mode control chart provided higher probability of coverage than the Shewhart method; although the detection rate (probability of detection) of out of control condition for these methods was slightly reduced compared with Shewhart method.

Jan 1, 2004

Council for 1999/2000 President M.H. Rogers President Elect Dr L.A. Cramer Vice Presidents Senior A.A.B. Douglas Immediate Past President J.R. Dixon Junior S.J. Ramokgopa Honorary Treasurer J.A. Cruise

Jan 1, 2000

By P. S. G. Leon

One of the most difficult areas in concession contracts in resource-rich developing countries is achieving an equitable balance between the interests of investors, host states and, increasingly, mine and near mine communities. While some countries in the Andean region have resorted to outright or creeping expropriation of natural resource contracts under the guise of resource nationalism, others such as the Democratic Republic of the Congo (DRC), have claimed international best practice in the review (and setting aside) of important concession contracts.

Jan 1, 2011

By J. C. van Dyk

The objectives of this study were firstly to characterize and quantify the inorganic material in the Secunda gasification feedstock. Secondly, the effect of washing on coal properties and sulphur content was investigated. Coal from a single source and a coal blend from 6 different mines were tested. Composite samples were visually sorted by a geologist in the groups containing roof, floor, C-shale, pyrite, carbonates and siltstone material. Inorganic mineral types from the single source and coal blends were characterized separately. Characterization results indicate that the average mineral matter distribution (mass %) of the coal tested was as follows: carbonates (6%), carbon-shale (19%), pyrite (12%), roof (18%), floor (46%) and siltstone (22%). The roof, floor, pyrite, carbon-shale, carbonates and siltstone in the single source and coal blend have similar chemical properties and characteristics, except for the ash melting temperatures of pyrite and kaolinite in the siltstone. By implementing selective mining and increasing mining management practices, the percentage discard in the run of mine coal can be significantly reduced, by up to 45%, if the mining of roof and floor material can be avoided. No significant impact of mining practices on sulphur content is expected in this case due to the low concentrations of sulphur in the roof and floor material. In summary, selective mining practices will probably result in almost45% decrease in the discard content in the run of mine to gasification, an increase in the carbon content from 55.0% to 58% (air dry basis) and a decrease in sulphur content from 1.1% to 0.9% (air dry basis). It is clear from this study that the main source of sulphur is not in the high ash-content mineral types (e.g. floor and roof), but in situ in the coal structure. Keywords: inorganic material, effect of washing, roof, floor, pyrite, C-shale, carbonates and siltstone

Jan 1, 2005

By L. Forsbacka, M. Nakamoto, L. Holappa

Viscosity of the slag is one of the central parameters when producing FeCr in submerged arc furnaces. It contributes to smelting behaviour and reduction kinetics of chromite ore as well as to the Cr recovery by influencing the separation of dispersed metal droplets from the slag. A typical FeCr process slag contains 5-10pct chromium oxides, CrO and CrO1.5. The neural network computation was applied to the evaluation of viscosity for slags containing chromium oxides, and the prediction of viscosity in FeCr process slag was conducted. The main results in this estimation were that the chromium oxides in FeCr process slag lower its viscosity, and that the effect of CrO on the viscosity decrease is greater than that of CrO1.5.

Jan 1, 2007