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By J. A. L. Napier

Computer programs which rely on the assumption of linear, elastic rockmass behaviour have been used routinely for many years in the South African mining industry to determine the stresses arising in the vicinity of mining excavations. A description is given of the theoretical background and novel solution techniques used in the recently developed MINSIM-D boundary element program. Features of the program include the ability to analyse multiple interacting reef planes at arbitrary orientation to one another, slippage on fault planes and the effects of backfill placement in mined areas. Incremental mining sequences can be modelled, and digitizer and front-end routines have been written to assist in the capture of mining outlines and general problem specifications. A brief indication is given of design problems for which MINSIM-D is appropriate, as well as some future extensions of the system.

Jan 1, 1987

By W. C. Joughin

A risk evaluation model has been developed that enables the quantification of expected injuries and economic losses resulting from rockfalls associated with a support system in a given geotechnical environment, which is described in Part I (Joughin et al., 2011b). Part II presents the validation of the risk evaluation model. Underground mapping of joints and rockfalls was carried out to provide data for field calibration of the model. This survey was limited to small rockfalls, due to the relatively short period of mapping. Therefore the model was also correlated with rockfall and rockfall injury data collected by mine personnel. The analyses showed that the model provides a reasonable estimate of the expected frequency and size of rockfalls and the frequency of rockfall injuries, but further work is required to enhance the model. Three case studies are presented, which show the benefits of improved support systems from both economic and safety perspectives. This work has demonstrated that the risk evaluation model and the software developed are immediately useful, but further work is required to develop and improve the tools.

Jan 1, 2012

Copper cyanide is a common component of cyanide-treatable precious metal ores. The copper concentration in production heaps can be predicted from laboratory column tests, but the exact correlation is not necessarily intuitive. Generally, heap leach operators like to keep copper concentrations in solution below 300?500 ppm and may note problems with gold recovery and cyanide consumption when copper concentrations exceed this amount. There are several methods of copper removal from cyanide solutions including ion exchange; direct electrowinning; acidification, volatilization, and recovery (AVR); and sulphide precipitation such as the sulphidization, acidification, recycling, and thickening (SART) process. SART involves acidification with addition of soluble sulphide, separation of the resulting copper sulphide precipitate, and addition of lime to re-establish alkalinity prior to returning the solution to the leaching process, recovering both copper and cyanide as valuable products. In principle SART is very simple. Yet some SART plants that have been built may have been unnecessarily complex. This paper explores the basics of SART and makes the case for a simple plant design as applied to the heap leaching circuit.

Jan 1, 2012

By W. J. Jordaan

The ability of soils to retain and hold cations is called the cation exchange capacity (CEC). Adsorbed cations, however, can be replaced by other cations through the process of cation exchange. Heavy mineral deposits contain a significant portion of slimes including the very fine clay minerals. In most circuits the slimes fraction hampers efficiency and has to be removed during early stages of the process. Being a nonvaluable process stream, the processing of the slimes is a costly exercise. In thickening applications it might be possible to manipulate the ability of clay minerals to retain and hold positively charged cations in order to optimize flocculation and therefore reduce flocculation costs. The CEC value of the slimes could be a measure of this possibility. To investigate this hypothesis, different slimes samples were characterized for size, chemical composition and clay minerals present. The CEC value of each sample was determined and explained in terms of the mineral phases present. Settling tests were conducted and an attempt was made to explain the CEC characteristics of the clay minerals in terms of settling rate. The scope of this investigation was to test the hypothesis and should not be seen as an in-depth study of the subject matter. A greater number of samples and detailed analyses to identify and quantify minerals and phases present would be required to investigate further the relationships between clay minerals in the deposit, CEC and settling rates. Location and geological setting Exxaro KZN Sands is mining a heavy minerals deposit at Hillendale mine located at Richards Bay, South Africa. The orebody consist of a dune some 8 km inland from the coast to the north of eSikhawini. A geological synopsis undertaken by Botha1 concluded that the Hillendale mining area represents a coastal dune sequence that accumulated north of the Tugela River. The northward movement of sediment by long shore drift currents result in a high sand budget on the beaches north of the river youth and is the dominant contributing factor to the accretion of the coastline and development of parallel dune systems along the coastal zone in this area. Beach swash zone processes and enrichment of the fine sand fraction occurs during wind transport off the beach by ascending parabolic dunes that form the coastal barrier dunes. This process results in heavy mineral concentration on the windward dune face and localized enrichment parallel to the dune forms. The aeolian sedimentary facies processes result in the primary concentration of higher grades in the upper silt-enriched reddish brown horizons of the profile. The synopsis by Botha1 further showed that an additional component of heavy mineral concentration can be ascribed to the post-depositional relative enrichment of heavy minerals due to weathering. Therefore, it is likely that the Hillendale orebody protolith was pedogenically weathered to form the homogeneous, silt-enriched, clayey reddish brown to dark red, palaeosol profile that grades downwards into yellowish brown, less clay-enriched sand. Slimes characterization Samples The Hillendale orebody was divided into geochemically discretized zones based on the concentration of ilmenite and other specific minerals and/or phases. Six composite samples were made up from exploration samples taken from Zone 9, Zone 11 and Zone 12. The red and orange horizons within these composite samples were separated and test samples were prepared to conduct test work and analyses. The test samples were submitted for preparation and analysis to characterize the slimes properties. Each test sample was deslimed at 45 µm representing the slimes fraction (-45 µm) and dried at 40°C. The -45 µm slimes samples were then split to conduct size analysis, chemical analysis, XRD and to determine the CEC. Size analysis The size distribution of the composite samples is shown in Table I. The size analysis shows that there is a difference in size distribution between the orange and red horizons of each zone. The orange horizons contain less 850 µ material as well as less slimes (-45 µm). The red horizons contain yore slimes (-45 µm). The size distribution of the slimes fraction (-45 µm) was determined using Malvern size analysis. The cumulative particle size distribution of the slimes is shown in Figure 1. The red horizons of the different zones show similar size distributions. The orange horizons show some differences. However, there is a difference in size distributions between the red and orange horizons.

Jan 1, 2007

By M. M. Hajdasinski

The internal rate of return (IRR) is one of the most popular project evaluation criteria in the mineral industry, as well as in other industrial sectors. Analysis of its assumptions reveals, however, that this criterion does not function in the way it is supposed to. The search for a new criterion that would reflect the true rate of return (TRR) of an investment project or the true borrowing rate (TBR) of a borrowing project has led to the development of several approaches, yielding, for the same project, generally different values of the interest rate in question. Two of those approaches have been selected as the most representative and practical. Each has been presented in two variants, and subsequently analysed. As a result, it is shown that the various approaches to the TRR/TBR are all consistent with the net present value (NPV) criterion, and that each can serve as an independent project evaluation instrument, provided its assumptions can be regarded in a given situation as realistic enough.

Jan 1, 1987

By D. Vogt

"Rock has been cut in the process of mining since before the invention of explosives. Today, we seek to return to cutting to reap the benefits of continuous operations for South African underground hard-rock mines, to improve speed of access to the orebody, and to improve the efficiency of mining operations.Development of new technology fits within a framework of engineering knowledge. By understanding the characteristics of the rock, the tools we use to cut it with, and the history of mining and rock cutting, we can see the genesis of the road-header, the longwall, and the continuous miner, all drag bit cutters. They have emerged as the solutions of choice for underground mining of softer materials such as coal and potash. In hard rock, the challenges are the forces required to break the rock, and the wear of the tools caused by the rock’s abrasiveness. Only disc cutters currently handle the challenges, and even then, often not economically. New materials like thermally stable diamond composite will help, as will combinations of mechanical cutters and other methods such as high-pressure water or high temperatures.It is not clear what will emerge as the consensus technique for hardrock cutting. Experience teaches that development is expensive and the market is small. Will mining companies partner with equipment developers to make the technological leap? Or will the solution come from a systems approach, not considered here?IntroductionBlasting is the dominant method of breaking rock for the purposes of mining. When used underground, blasting is part of a batch process. If rock can be cut rather than blasted, mining can become continuous, leading to process and efficiency improvements.Coal produced from underground mines is now predominantly excavated using mechanical means, but underground hard rock is still broken primarily by explosives.This paper traces the history of rock cutting, reviews the main physical processes that are or could be used, and comments on the future. It is written from the perspective of narrow-stope hard-rock mining typical of South African gold and platinum mines."

Jan 1, 2016

One of the key issues facing gold producers is the management of cyanide and the implementation of the International Cyanide Management Code. Many operations now use cyanide destruction processes to ensure that the material being discharged to the tailings dam is compliant with regulatory requirements and the International Cyanide Management Code. One of the problems for operations is the quantification of both cyanide species and their reaction products throughout the leach and destruction circuits. Therefore methods have been developed utilizing high performance liquid chromatography (HPLC) to measure free cyanide, cyanide complexes of metals such as copper and iron, and other species formed from reactions in leaching and cyanide destruction, including cyanate, thiocyanate, and sulphur species (eg. sulphite, thiosulphate and sulphate). This enables a complete mass balance for cyanide and sulphur in both leaching and cyanide destruction. This paper outlines the methodology which has been developed and discusses the application of these methods in the fundamental research currently being conducted on the impact of sulphide minerals in cyanidation and cyanide destruction chemistry.

Jan 1, 2009

By P. Goosen

The paper presents a basic summary of the approach to hydraulic scale-model tests as may typically be applicable to slurry flow situations. A case study is presented illustrating how hydraulic scale-model tests can be of significant benefit in evaluating the performance of novel or unproven slurry handling equipment. In this case the equipment tested was a fan-shaped expansion piece used to spread the discharge from a launder over the full width of a dewatering screen. The tests showed that the device did indeed distribute the slurry flow both in terms of volume and solids mass, but not perfectly uniformly. Unfortunately the equipment was not taken beyond the model test phase. The scale-model test approach did, however, prove to be very useful as it is considered to have provided a good indication of the expected performance of the full-size unit. Significantly, this was achieved at very low cost compared to the cost of installing the device into the proposed plant and having to later change it out for an alternative or live with the less than optimal performance. The paper illustrates the value that can derive from applying hydraulic scale-model testing techniques to evaluating the performance of new or unusual slurry handling equipment. There is particular value in situations that do not lend themselves to numerical modelling.

Jan 1, 2007

By A. J. Hofmann, G. P. R. van der Merwe, J. E. W. Holm

"A new approach is proposed to perform relativistic comparisons between alternative operational risk management solutions by taking into account the impact of each operational activity on overall system performance. A specific case study, to which this new approach is applied, involves the deployment of safety systems in underground mining operations. Conflicting objectives to be satisfied are the minimization of risk to human lives and the minimization of production losses. As the focus in this case is primarily on the mitigation of risk, the approach that was applied is referred to as activity-based risk (ABR) analysis. Existing development process and risk management methods used in the South African mining environment were analysed by means of observations, a case study, technical documentation, and literature review. It was evident from this analysis that a discontinuity existed between the acquisition and operational phases in terms of the management of safety risk in the acquisition of electronic safety equipment when viewed from a full lifecycle perspective. This discontinuity could be addressed by defining a risk perspective in the system development phase by employing ABR in the preliminary design phase of a system’s engineering life-cycle. The focus of the ABR system development process is to find the functional definition and configuration of safety equipment that addresses both safety and productivity when taking into account human performance variability. In doing so, a balance between productivity and safety is found in a relativistic sense. IntroductionIn any system life-cycle, two major phases exist, namely system acquisition and operation (including maintenance). A distinction is made between acquisition and procurement, where acquisition includes system development and integration as specific engineering activities. In the development phase of a new system, conceptual design, preliminary design, and detail design phases follow in this order to define a complete system, after which the system is put into production and implemented in an operational environment—these activities chronologically define system acquisition in the context of this paper. It is not uncommon that differences exist between the risk management perspective during acquisition of a system and risk management perspective during operation, where nontechnical aspects are often ignored during acquisition, but are then encountered and found to be problematic during operation (Leveson, 2012). These differences also exist in the mining industry."

Jan 1, 2017

By R. L. Castro

Currently, in several caving operations, the spacing between the drawpoints is determined by consulting Laubscher's design guide (Laubscher 1994, 2000), a methodology based on the gravity flow characteristics of the caved rock. Laubscher's methodology is based upon the height of interaction between adjacent flow zones, but does not allow calculation of primary recovery for a given layout. In this paper the authors present a technical and economic methodology based on the flow that occurs near the drawpoint and the associated development costs to estimate the optimal spacing. The flow model at the drawpoint was validated at the El Teniente mine, which extracts coarse caved rock. To validate the flow model, small-scale simulations using drawpoint clusters were conducted and results compared to extracted grades, marker recovery, and drill holes to determine ore remnants that are part of the production control programme at the mine. The results indicate that primary recovery depends on the height of interaction, which varies with the friction angle of the caved rock and the spacing between adjacent drawpoints. Primary recovery estimations indicate values from 85 per cent to 97 per cent depending on the drawpoint spacing used. Extrapolations were then conducted to estimate the primary recovery for different drawpoint configurations planned to be used in the New Mine Level of the mine. The results indicate that the optimal drawpoint spacing is 32 m x 20 m with a through length of 18 m. The methodology developed may be used to estimate optimal drawpoint spacing for block caving mines under different metal prices and mine cost conditions.

Jan 1, 2012

By K. Richardson

Although the De Beers group has a long history of placer mining on land, the group only became actively involved in deep water marine diamond exploration and mining in1983 with the formation of De Beers Marine. Full-scale commercial mining commenced around 1991. Since then, the group marine mining capability has grown into a formidable fleet of 8 large deep water (>70 m) mining vessels, as well as other special purpose geo-survey platforms. Marine diamond production by the group is expected to be just short of 1 million carats in 2006. DeBeers operates across the entire value-chain spectrum from geology and geo-survey, through sampling to mining, and finally ore processing into high value concentrate. Supporting these operations involves significant service activities such as maintenance, security, logistics and environmental management. Specific challenges exist in terms of developing or acquiring appropriate technology for marine mining. These challenges have resulted in DeBeers operating extensive in-house R&D and projects departments, as well as drawing extensively from technology partners. An array of computational and test facilities are also available to support R&D and projects activities. Hydro transport in various guises is key to the current approaches to marine mining and ore processing. Use is made of airlift and centrifugal pumping for hydraulic hoisting of very coarse gravel, while splitters, launders, dewatering, elutriators, jet-pumps, centrifugal pumps, dense medium circuits, pipeline systems, and instrumentation for coarse abrasive particles are used extensively in the ore processing plant.

Jan 1, 2007

By E. L. Thyse, P. Bepswa

The Western Cape Mineral Processing Facility (WCMPF) is a collaborative educational initiative between the Department of Process Engineering at the University of Stellenbosch and the Chemical Engineering Departments at the University of Cape Town and the Cape Peninsula University of Technology. The primary objective of the WCMPF is to facilitate the education, development and graduation of suitably qualified engineering graduates and diplomats for the mining and mineral processing industries. In recent years the WCMPF has embarked on a number of initiatives aimed at improving the quality of mineral processing education which include, more importantly the introduction of novel ?end to end? or ?integrated? practicals. The practicals are developed around a specific mineral theme or route, which more than often includes the development of several new pilot plant practicals demonstrating key unit operations or processes in the selected mineral theme or route. The most recent mineral processing pilot plant practical programme is developed around the beneficiation of heavy mineral sands. The programme consist of the following developed pilotplant practicals: the online electrostatic separation of free flowing mineral sands using a Roche Mining Carrara high tension roll separator incorporating a Blue Cube Systems MQi in-line mineral quantifier; the production of titania-rich slag and pig iron from the smelting of ilmenite and anthracite in a 60 kW direct current (DC) plasma arc furnace as well as the mineralogical characterization of the feed and products; the continuous closed-circuit ball milling and screen classification of titania-rich slag. This paper illustrates the important role of a well-designed heavy mineral sands beneficiation pilot plant practical programme in facilitating the education and development of suitably qualified personnel for the mining and mineral process industries.

Jan 1, 2007

With the advent of the First World Conference on Sampling and Blending (WCSB1) in Denmark in 2003 and the subsequent biannual meetings, together with other sampling conferences held on a regular basis, the central tenets of sound sampling practice and theory are spreading throughout the minerals industry. End-users and project houses, or groups who execute the projects, are all now better-informed about the principles of ?correct? sampling and preparation. To support this, many large mining companies now have their own in-house champion who will advise and ensure that the supply of sampling equipment is correct in terms of design and application, which further contributes to improved metallurgical accounting. The presence of a sampling champion also ensures that consistent and acceptable standards in regard to sampling practice are maintained throughout the group. This has, in turn, placed a greater degree of responsibility on the shoulders of sampling equipment suppliers, in terms of their equipment designs and product offerings, as well as applications knowledge for effective installation of equipment on client plants. This paper attempts to highlight the significant challenges that sampling equipment manufacturers often face with regard to complying with the newly understood requirements of best practice and sampling equipment design. Manufacturers invariably face issues with end-users or project houses, including project cost control, restricted headroom for samplers in plant layouts, and a lack of knowledge in certain quarters. These all have a potentially negative effect on the final outcome of a proposed sampling solution or implemented project. In reality, what is intended by all parties and what is ultimately installed are at times very different, with undesirable consequences for all concerned. Against this challenging background, there are, however, a number of instances where intent and implementation are complementary, with very satisfactory results. Keywords sampling, mechanical samplers, design, installation, sampling theory.

Jan 1, 2014

By M. Timusk

"The working environment for ground support installation in mines has improved during the last 20–30 years, with more mechanized equipment for installation of ground support elements such as bolts, cable bolts, and screens. Ground support installation productivity has, however, not followed the same development curve, remaining more or less constant. In some cases, for example the mechanized installation of bolts, productivity has even dropped. One reason for this is that modern mechanized bolt rigs are complex. In this paper we evaluate manual and mechanized ground support systems, propose a way to measure the productivity of bolt rigs, and make relevant comparisons between different mines and equipment. Some productivity measures for rock reinforcement are suggested, using productivity results from eight case study mines.IntroductionTo improve safety for operators and equipment underground, ground support systems (bolts, screens, etc.) are installed in mines to stabilize the rock mass (Hoek, Kaiser, and Bawden, 1995). Important questions to ask when selecting a ground support system include where ground stability problems are located, why they have occurred, how problems should be addressed, and when and how the ground support system should be installed (Hadjigeorgiou and Potvin, 2011). The performance of bolting and screening operations in underground mines is important for both safety and productivity reasons. With greater mine depths and an increasing focus on safety, ground support has become a significant bottleneck in the production process of many mines.Many factors play a role in establishing safe and stable underground structures. Equally, there are several factors to consider in productivity, including the mining method, organization, logistics, mechanization level, and procedures. Today, most mines in Scandinavia have changed from manual to mechanized bolting, as this improves operator safety and arguably boosts net capacity. Internationally, however, manual installation of bolts remains common, with some claiming that manual installation is more productive (Bawden, 2011)."

Jan 1, 2016

By M. J. Kahn

A new Scramble has hit the African continent. This Scramble has many drivers: the 1978 Deng Xiao Ping liberalizations in China; the 1989 collapse of the Soviet empire; the ICT revolution; the ease of global communications. The underlying dynamic is the end of the bipolar world of the Cold War and its replacement with multipolarity. According to HSBC (2011), in 2050 China will be the world?s largest economy, with India number 3 and Brazil number 7. Russia will be 15th (below its old rival, Turkey). South Africa maybe ranked 30th, yet has been invited to join the exclusive (BRIC) club. One has to ask, why? It is sad to note how low South Africa is assessed to be?currently it is around number 24 in the world; the reason for the fall is that the HSBC model includes population growth, and it is in this domain that South Africa is a loser, being constrained by the impact of HIV/AIDS on its life expectancy. The original four BRIC nations include the factory of the world (China), the garden of the world (Brazil), the gas station of the world (Russia), and the back office of the world (India). South Africa comes to the club both as jeweller of the world and as gatekeeper. China, Brazil, and Russia all have considerable expertise in mining exploration, extraction, and processing.

Jan 1, 2011

By H. W. J. P. Neomagus, J. R. Bunt, T. S. Mthombo, C. A. Strydom

"Low-cost calcium lignosulphonate (CL), which is a byproduct of the wood pulping industry, was investigated as a potential binder during laboratoryscale pelletization of inertinite-rich high-ash coal fines from the Highveld Coalfield of South Africa. Coal-binder mixtures containing between 1 and 15% calcium lignosulphonate were prepared, pressed, and ultimate, proximate, porosity, XRD, and XRF analyses obtained. It was found that increased pressure during pelletization results in increased attractive forces, due to increased interparticle contact areas. FTIR analysis showed that chemical interactions occur between coal fines and the binder, as evidenced by the formation of new C-O ether-type bonds. The presence of moisture during pelletization enhanced surfactant activity of the binder. Chemical interactions between the coal and the binder seem to be mainly electrostatic, driven by Ca2+ from the calcium lignosulphonate, which may act as a bridge between the anionic parts of the binder and the surface of the coal. IntroductionCoal has over the years remained South Africa’s major energy source, with over 90% of the country’s electricity being produced via coal-fired processes (Arndt et al., 2016). Sasol’s coal conversion technology alone provides more than 40% of South Africa’s liquid fuel requirements (van Dyk, Keyser, and Coertzen, 2006). The production of high-grade coal requires the processing of run-of-mine (ROM) resources by a combination of processes which include crushing, screening, and washing (Radloff, Kirsten, and Anderson, 2003). These processes result in the generation of coal fines (< 0.5 mm) which, until recently, have been discarded into slimes dams (le Roux, Campbell, and Smit, 2012). Several issues are associated with slimes dams, among which are the costs of transportation of these fines from the place of origin to the discard point (often a considerable distance), and the potential environmental effects due to seepage of toxic materials into surrounding ecosystems (Clausen, 1973).Consequently, utilization of these coal fines is an area of great interest. Mechanical densification of fine coal by means of pelletization and/or briquetting to larger sizes for use in technologies that require lump coal, such as chain-grate stokers and fixed-bed gasifiers, has been shown not only to reduce environmental risks (Mangena et al., 2004), but also to significantly reduce storage and transportation costs (Mani et al., 2001). Pelletization is the process by which solid particles are consolidated into uniform, usually hard, impact-resistant agglomerates, rendering them useful as a fuel with sufficient calorific value for domestic and industrial utilization (Finney, Sharifi, and Swithenbank, 2009)."

Dec 1, 2018

By G. M. Wright

We are only as good as we are perceived to be by others and, whilst there is every opportunity to revise and polish our written works, there are no second chances with a spoken presentation. At every level, conferences and seminars have been metaphorical graveyards for many an academic reputation.

Jan 1, 1990

By M. K. Matthews

The use of backfill has important environmental control implications which, although frequently overlooked, can be both beneficial and problematical. Where backfill is widely used, the reduction in stope heat load and improved air utilization influence the overall mine ventilation and refrigeration requirements significantly. A programme of work examining in detail all the environmental consequences of backfilling is currently underway at the Environmental Engineering Laboratory of the Research Organization of the Chamber of Mines. This paper gives an overview of the work and presents some findings. In so doing, the environmental implications to be considered when backfilling are highlighted.

Jan 1, 1988

By P. De Kock

Strategic mine planning is concerned with the decisions that determine the value of the business, while tactical planning deals with the tasks to realize that value. When tasked with formulating a strategic mine plan, the mining engineer often turns to commercially available software. However, these software packages have limited applicability to the RBM situation. Adopting a simpler, back to basics approach founded on a deep understanding of the economics of the orebody has the advantage of providing a clear logic to guide tactical planning. By creating a coherency between strategic mine planning, and tactical planning the likelihood of successfully executing the plans and attaining the value promised by the strategic plan is increased. This paper describes the reasons why RBM embarked on a strategic mine planning process, the rationale of choosing the process, and the process itself.

Jan 1, 2007

By John Freer

On 25th November, 1983, nearly forty members of The South African Institute of Mining and Metallurgy, together with Doris Gardner and Judith Money from Kelvin House, travelled by luxury motor coach to Secunda, there to visit the coal-mining and conversion operations of Sasol Limited.

Jan 1, 1984