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By M. van Schoor

The bulk of the world?s platinum production originates from the Merensky and UG2 reefs within the Bushveld Complex, South Africa. Both the Merensky and UG2 reefs are disrupted by faults, dykes, potholes and iron-rich ultramafic pegmatite bodies (IRUPs)?features that impact negatively on production, planning and safety. It is therefore advantageous to know of their presence and geometry ahead of mining. To date, no geophysical technique has been successfully applied to the routine mapping of mine-scale potholes and IRUPs. These disruptive features may vary from a few metres to several tens of metres in diameter. In this paper the applicability of in-mine electrical resistance tomography (ERT) to map potholes and other disruptions to the continuity of the Merensky and UG2 reefs ahead of mining is demonstrated using two case studies.

Jan 1, 2005

By P. J. Bartlett

Premier Diamond Mine exploits a kimberlite orebody using cave mining methods. A drilling level is established at the base of a block of ore to effect undercutting that leads to caving of the overlying ore. A second level is developed some 15 metres below the undercutting level to allow extraction of the ore once it has caved. As much as 45 per cent of the rock is removed on the extraction level creating a series of pillars. Undercutting creates abutment stresses, as high as 3 times the virgin stress, which affect the rock mass to a distance of 20 metres from the undercut face on the undercut level and on the extraction level 15 metres below. If the extraction level is completely developed prior to undercutting, where stress levels exceed 20 percent of the rock mass strength, extensive rock mass and support damage occurs as the undercut passes overhead. Rock mass damage takes the form of movement along existing joints and minor shear failure through intact rock. Support damage takes the form of cracking in rigid concrete linings. Where induced stresses exceed 50 per cent of the rock mass strength it is often impractical to keep excavations on the extraction level open. Rock mass damage takes the form of extensive failure of the rock in shear which evidences itself as propagation of the fracture zone around tunnels and footwall heave. Support damage results in destruction of shotcrete linings and concrete footwalls. As the interbolt support fails, badly fractured rock ravels around the steel tendons. Observation and monitoring at Premier Mine and on other cave mines has shown that induced stress levels and consequent damage are a function of :?the extraction ratio on the undercut and extraction level prior to undercutting ?the shape of the undercut face ?the rate of undercut advance ?the distance of leads and lags between adjacent tunnels on the undercut level. To ensure the stability of excavations, all of the above parameters must be carefully planned and the planned mining sequence rigidly enforced. The minimum of development is completed on the extraction level prior to the undercut passing overhead. Required development is then rapidly completed once the area has been de-stressed. Support is installed in three phases: ?Rockbolts are installed as soon as excavations are developed ?Wire mesh, steel tendon straps and a layer of shotcrete sufficient to protect the mesh and straps from damage by blasting and LHD loading is installed as soon as practical thereafter. Inevitably the shotcrete lining has to be replaced once the undercut has passed overhead.. ?Rigid shotcrete linings and concreted footwalls are completed only after the undercut has passed overhead and the area has been de-stressed.

Jan 1, 2000

By G. B. Quaye

The deep level gold mining environment is characterized by high stresses that give rise to intense mining induced fracturing of the rock mass surrounding the stopes. In a geologically disturbed region where the intensity of mining induced stress fracturing is high, the degree of faulting and/or the frequency of other geological features such as joints may pose serious strata control problems. Unfavourable intersection of these discontinuities namely, faults, joints and mining induced stress fractures tend to divide the immediate hangingwall into unstable keyblocks which, if not supported, may result in extensive falls of ground. Effective support strategies therefore demand detailed investigation of the predominant inclinations and orientations of these discontinuities. The orientations and inclinations of these discontinuities surrounding a deep level stope have been measured. The results are projected onto the lower hemisphere of a stereographic net to determine the factors that contribute to the falls of ground in the stope. The analyses reveal that unfavourable intersection of these discontinuities divides the immediate hangingwall into unstable wedges that may become dislodged between support units.

Jan 1, 1998

By J. Pelders, F. Magweregwede, S. M. Rupprecht

Increased depths of conventional gold and platinum mines, longer travelling times as working places move further from the shaft, and ancillary activities taking place in the mining cycle reduce the useable time spent at them workface. Current shift lengths of 8 hours 20 minutes may no longer be adequate ton complete required mining activities.The impact of mineworker commuting times on shift work is also not well understood. The aim of this research was to draft a framework to optimize shift cycles in order to maximize productivity, health, safety, and wellness in the South African mining sector. The framework was informed by a review of the literature, case studies at a local gold mine and platinum mine, and a workshop with industry experts. The findings indicate potential advantages of extended shift lengths and continuous operations, such as improved productivity, asset utilization, and employee morale. However, concerns included fatigue and the associated safety hazards, particularly when working longer shifts, night shifts, and numerous consecutive shifts. Job demands, personal factors, and commuting times are further considerations when scheduling shifts. The ideal shift system for the mining sector should holistically consider and balance operational requirements, health and safety, and employees’ and their families’ requirements, and suit the unique needs of each operation. Changes in shift cycles will require a structured change management process, which involves all stakeholders, and could help to enhance the viability of the South African mining sector.

Aug 1, 2021

The extraction of minerals and coal at greater depth, employing higher-powered machinery to improve production levels, imposes an increased burden on the ability of a ventilation system to maintain an acceptable mine climate. Hence, mechanical mine cooling systems are often adopted, which can be expensive in terms of both their associated capital and operating costs. Consequently, in order to optimize the total mining costs, it is essential to provide the mine operator with a method with which to determine the most cost effective and efficient mine cooling system. In a previous paper1a novel energy analysis employing the concept of exergy was proposed and applied to cooling systems applied to two conceptual model mines, representative of UK deep coal operations, and their resultant subsurface thermal environ-mental conditions predicted. This paper presents an analysis of the results obtained from the application of this novel technique to assess the performance of various cooling systems applied to a current UK colliery that is experiencing climatic problems due to its depth and highly mechanized production and development workings. To perform this analysis, ventilation and climatic data collected at the case study mine were used to construct balanced mine ventilation and climatic network models to replicate the subsurface environment. Where air conditions exceeded specified climatic limits within identified climatically control zones, mechanical mine cooling systems were employed. A number of cooling system configurations were applied to these model to investigate the potential to satisfactorily regulate the thermal environment. The heat energy transferred out of the air stream by the various cooling methods was absorbed using a variety of chilled water systems, which were designed to operate at various water flow rates and temperatures. Models of various cooling system were developed and applied to control the underground climate within this mine network to within pre-set climatic limits. The results of a comparative analysis of the energy transfers that were produced by the application of the different cooling systems are presented in the form of exergy performance indices. The results produced by simulation models constructed to represent chilled water distribution networks to supply the various air coolers, are designed and balanced. The results of the exergy analyses applied to the operation of the various chilled water pipe networks are discussed and used to assess the exergetic performance of the application of each proposed cooling system to the mine ventilation network.

Jan 1, 2004

By S. Bellec

A leaching model for gold ore that takes into account the impact of cyanide and oxygen concentrations as well as gold surface exposure on leaching performance is developed. Cyanide consumption is estimated by an empirical model that is a function of ore particles size distribution as well as cyanide, copper and sulphur concentrations. The proposed model has been validated by data from laboratory leaching tests on the Sleeping Giant gold mine ore. Keywords: gold leaching, modelling, exposure surface.

Jan 1, 2009

By J. Betzhold

Knowing more about an orebody makes it easier to exploit it profitably. Many orebodies are made up of different rock types, alteration zones or mineralogical ensembles: oxides versus sulphides or facies with different metallurgical properties for example. Being able to model the spatial layout of these different facies is vital to good mine planning and management. Kriging cannot be used to generate numerical models of orebodies with complex geometric patterns because it gives too smooth an image. Over-smoothing has the meaning of changing the natural selectivity. Conditional simulations are required to do this kind of model respecting the natural variability: honouring the natural selectivity, dilution and ore loss. Standard geostatistical simulations cannot duplicate many of the complex spatial relationships seen in the earth sciences, such as differently orientated facies, sets of conjugate veins or ore types where certain facies cannot touch. After a presentation of the case study, it will be shown why traditional methods for simulating indicators like the sequential indicator simulations, or the truncated gaussian method, cannot be used to simulate it. Plurigaussian simulations are then introduced and shown to be more powerful than the previous methods in their range of application. This is confirmed by the case study treated; a Chilean copper deposit, for which the plurigaussian simulations are seen to respect the different orientations of the individual facies as well as honouring the facies seen in drill holes, and respecting the proportion of each facies even if this varies in space (e.g. increases or decreases with depth). Key words: geostatistics, indicators, conditional simulation, plurigaussian method, copper variability.

Jan 1, 2000

By I. Alp

Application of magnetic separation was investigated for the enrichment of colemanite ores by removing the magnetic gangue fraction. The detailed XRD analysis of the ore has indicated that the gangue fraction is composed predominantly of the iron-bearing silicates such as smectite and, to a lesser extent, illite. Magnetic susceptibility measurements of the colemanite and gangue samples have proved that colemanite is diamagnetic in character whereas gangue fraction is weakly paramagnetic to allow the removal of this fraction by magnetic separation. Magnetic separation of the crushed and sized ore samples (-5 mm +75 µm) was performed using a high intensity permanent magnetic separator. Under the test conditions a colemanite concentrate (41.29 wt.% B2O3) was found to be produced from the crushed ore (30.76 wt.% B2O3) at a recovery of 96.76%. These findings suggest that magnetic separation has great potential as an alternative process for the production of a concentrate of commercially sufficient grade.

Jan 1, 2009

By T. Kagogo, M. Neser, C. Knobbs, E. Gerryts

"Contrary to the way it is often portrayed, the average organization or company is far from being a cold, calculating machine. It is actually a highly emotive place where interaction with people is a fundamental part of its ability to perform satisfactorily.The company, through its employers, expects employees, including new graduates, to have the ability to cope adequately with this emotive environment. The graduate is frequently unable to meet this expectation because he/she has not been developed to do so. Technical knowledge is his only asset. This deficiency manifests itself in leadership shortcomings, both intrapersonal and interpersonal. Further analysis reveals a deficiency in three elements of leadership - self-awareness, oral communication, and an ability to work cooperatively in teams.To address these three elements of leadership, Sasol Coal, a subsidiary of the big petrochemical company in South Africa, sponsored a leadership programme at the University of Pretoria for their final-year bursary students in the faculty of Engineering. This programme, the Sasol Engineering and Leadership Academy (SELA), consisted of a number of interventions designed to address the three areas of self-awareness, oral communication, and cooperative behaviour in teams. These interventions varied from an intrapersonal nature to interpersonal aspects. Psychometric assessments were followed by experiential modules dealing with the three constructs.SELA was evaluated at the end of the year. The results showed a positive shift in the main constructs of self-awareness, communications, and cooperation. This was measured quantitatively and qualitatively. Conclusions were drawn and recommendations for improving the programme were proposed."

Jan 1, 2014

By C. Knobbs

Contrary to the way it is often portrayed, the average organization or company is far from being a cold, calculating machine. It is actually a highly emotive place where interaction with people is a fundamental part of its ability to perform satisfactorily. The company, through its employers, expects employees, including new graduates, to have the ability to cope adequately with this emotive environment. The graduate is frequently unable to meet this expectation because he/she has not been developed to do so. Technical knowledge is his only asset. This deficiency manifests itself in leadership shortcomings, both intrapersonal and interpersonal. Further analysis reveals a deficiency in three elements of leadership ? self-awareness, oral communication, and an ability to work cooperatively in teams. To address these three elements of leadership, Sasol Coal, a subsidiary of the big petrochemical company in South Africa, sponsored a leadership programme at the University of Pretoria for their final-year bursary students in the faculty of Engineering. This programme, the Sasol Engineering and Leadership Academy (SELA), consisted of a number of interventions designed to address the three areas of self-awareness, oral communication, and cooperative behaviour in teams. These interventions varied from an intrapersonal nature to interpersonal aspects. Psychometric assessments were followed by experiential modules dealing with the three constructs. SELA was evaluated at the end of the year. The results showed a positive shift in the main constructs of self-awareness, communications, and cooperation. This was measured quantitatively and qualitatively. Conclusions were drawn and recommendations for improving the programme were proposed.

Jan 1, 2014

The relationship between neural network (NN) performance and the parameters that form the architecture of the neural network is complicated. This paper studies an issue that is still controversial—the effect of the number of neurons and number of hidden layers on NN performance. This paper tests if the above parameters affect network performance when the NN is trained according to the quick stop strategy. It was determined that the number of neurons did not have any effect on the NN performance for a single layer or a double layer network. It was also found that the training error and calibration error could be poor indicators of the prediction correlation coefficient.

Jan 1, 2003

By A. H. Mokken

Failed attempts at amalgamation of a gold/osmiridium concentrate, recovered behind pebble mill liners during re-lining, led to the discovery that the gold particles were coated and that nitric acid only could remove the coatings. Following this treatment amalgamation was rapid and resulted in a complete recovery of the gold that otherwise would have been lost in plant residues. Investigations into the nature and formation of the coatings led to the realization that the coatings were impregnations of harder elements, associated with the gold during grinding and driven into the softer gold surface by high pressure, impact and attrition. It was further realized that this phenomenon could be part of gold ore milling, world-wide. With these thoughts in mind the question is asked whether concentration down to micron sizes prior to cyanidation, should not play a greater role in gold recovery.

Jan 1, 1999

By C. Birch

"A mineral resource royalty is payment to the holder of mineral rights for the utilization of the mineral resource. In South Africa, this payment is made to the State as holder of the mineral rights (The Mineral and Petroleum Resources Royalty Act of 2008). The principle purpose of this research paper is to identify if the State is benefitting from the mineral resource royalty by considering its impact on seven individual Witwatersrand gold mines.For this study, a simple financial optimiser model was created in Microsoft Excel that links the ore flow, block listing and the cash flow (excluding or including the cost of the mineral resource royalty). Mixed integer linear programing (the Excel Solver function) is utilised to optimise either profit or NPV (at 9% and 12%) by adjusting the cut-off grade.The impact on each of the seven mines mine was different but overall R7.9 billion is estimated to be paid in mineral resource royalty over their expected remaining lives. Due to the cost of the mineral resource royalty and increasing the cut-off grades, the total revenue decreases by R10 billion. A significant portion of this lost revenue would have been paid to the State in the forms of other taxation including company income tax which decreases by R2.8 billion. It is recommended that an industry wide investigation be conducted to determine if the resource royalty is adding to the State’s revenue, or destroying value including premature job losses. IntroductionTaxation of mining companies has become a very topical subject in the context of the postapartheid South African economy. There have been increasing calls for equitable re-distribution of mineral asset wealth for the benefit of all South African citizens and not just to an elite few. As part of the Mineral and Petroleum Resources Development Act (MRDPA) of 2002, the Mineral and Petroleum Resources Royalty Act of 2008 was introduced and came into effect in 2010 (South African Revenue Services, 2008). A mineral royalty is payment to the holder of mineral rights for the utilization of the mineral resource. In the case where the holder of the mineral right is the State, then this payment is made to the State (Cawood, 1999). Studies on the potential impact of the mineral resource royalty on the minerals industry have been conducted during the formulation of the Act and subesquently. These include Cawood and Macfarlane (2003), who suggested a cap of no more than 3% (Cawood and Macfarlane, 2003), as well as Cawood (2011), who predicted rising cut-off grades and thus reducing mineral reserves. In 2013, Grobler completed a Masters in the Faculty of Economic and Management Sciences at the University of Pretoria and concluded that the impact of the mineral resource royalty on the economy is positive. She stated that the royalty has caused operating expenses to increase, but this does not appear to be significant. Furthermore, she stated that the royalty has not affected the way the mining industry operates (Grobler, 2014)."

Jan 1, 2016

By T. Tholana

South Africa hosts some of the world?s largest known resources and reserves of minerals that are strategically important to the global economy. The country?s mining industry contributes significantly to the national economy in terms of gross domestic product, export earnings, corporate tax receipts, remuneration earnings, and employment. Platinum, gold, and coal are significant minerals because they make the largest individual contributions to these economic indicators. Several factors impact the cash cost performance of operations that mine these minerals, thus affecting the future sustainability of these operations, which are generally ?price-takers?. It is therefore important that the cash cost performance of operations for these key minerals is analysed. Commercially available industry cost curves can be used for such analysis. However, some companies may not be able to afford to purchase these curves. This paper presents a simple Microsoft Excel® algorithm for constructing the curves. It also demonstrates how the constructed industry curves were used to analyse the cash cost performance of South African mining operations for the three selected minerals for the period 2007 to 2011, which included the 2008 global financial crisis. The analysis revealed that the operations were affected by several global and local factors during the review period. The work reported in this paper is part of an MSc research study at the University of the Witwatersrand. Keywords cost curve algorithm, economies of scale, cash cost performance

Jun 1, 2013

By S. Sekhar, S. Bhargava, A. K. Godugu, J. L. Porathur

Cemented backfilling has enabled underground hard rock mines to extract orebodies more safely with improved ore recovery. It is important to estimate the minimum required strength parameters for a backfill mix by optimizing the binder percentage to enable cost-effective and safe stoping operations. We conducted three-dimensional numerical modelling to study the effect of various stoping parameters on the stability of a free-standing backfill wall. A Mohr-Coulomb material model was used for the backfill material and the rock-fill interface. A strength reduction technique, excluding friction angle, was employed to arrive at a minimum stable strength value for the backfill. For a given combination of strength values, the stability state of the backfill wall could be demarcated using a displacement and yield zone tracking method. The numerical modelling results are compared to some earlier theoretical models. From the simulations, a predictive equation is developed to predict the required strength parameters for a backfill mix to ensure a stable free-standing wall. Examples are given of the successful use of the predictive equation at some underground hard rock mine sites in India.

May 2, 2022

By I. L. Follington

This paper describes the research and development programme to develop a prototype underground auger mining system aimed at developing and demonstrating an underground auger mining system able to provide economic access to thinner (<1.8 m) coal reserves of South Africa. Data concerning the performance of modern coal augers under South African coal mining conditions were gained from a proven surface auger which operated across a range of coal types. These data were analysed and considered in conjunction with historical information regarding previous attempts at building underground augers dating back to the 1950s. Drawing on these data a prototype underground auger mining system, the BryDet BUA 600 underground coal recovery auger, was designed and manufactured by the BryDet Development Corporation in collaboration with Eskom and Cutting Edge Technology Pty Ltd with support from Anglo Coal and the Ingwe Coal Corporation Ltd. The prototype BryDet BUA 600 underground coal recovery auger commenced trials in March 2000 at the Matla Mine near Witbank in South Africa. The initial trials were undertaken in an open cut to facilitate the commissioning and training associated with a prototype mining machine. A total of 30 holes was augered in the box cut before the machine moved underground. The prototype BUA 600 first achieved the target penetration depth of 80 m in its third hole. The prototype BUA 600 is a new underground mining system which has passed early testing with ?flying colours? and could provide access to extensive underground coal reserves unmineable by conventional mining techniques both in South Africa and elsewhere around the world.

Jan 1, 2001

The 105th Annual General Meeting of The South African Institute of Mining and Metallurgy was held in the J.C. Lemmer Auditorium, SA National Museum of Military History, 22Erlswold Way, Saxonwold, Johannesburg on Thursday, 8thAugust, 2002. Welcome The President extended a special welcome to the guests and representatives of our sister institutes and other associations. Also to recipients of awards, senior members of industry, Honorary Life Fellows, Past-presidents, our Members and other guests, among them the following: Mzolisi Diliza, Chief Executive, Chamber of Mines of South Africa Dawie van Wyk and Rod Tucker, Vice-presidents, The Geological Society of South Africa Vaughan Townsend, President, Institute of Certificated Mechanical and Electrical Engineers, South Africa Karel Landman, President, Institute of Mine Surveyors of South Africa Frik Grobbelaar, South African Colliery Managers? Association Pierre Ballot, President, South African Institute of Electrical Engineers Trueman Goba, President, South African Institution of Civil Engineers

Jan 1, 2002

By S. Schutte, J. Pelders

Worker participation in equipment development can result in improved user acceptance and product quality. This paper focuses on worker engagement in equipment development processes in the South African minerals sector. Qualitative data was gathered during interviews with original equipment manufacturers (OEMs) and industry experts. A lack of inclusion in equipment design from workers from all organizational levels in mines was reported. Meanwhile, the historical context and workplace culture of the mining industry (including leadership, trust, training, performance, and remuneration factors) were evident barriers to the implementation of new technology. Worker engagement processes should include securing management commitment, creating multidisciplinary teams, effective facilitation, shared understanding of needs, training and development, and iterative design. Human-centred design approaches and independent platforms for engagement on equipment design requirements are recommended.

Feb 2, 2021

By Dechun Lou, Benjamin Ravary, Merete Tangstad, Stein Wasbø, Sean Gaal

The melting phenomena of manganese ore, slag and alloys were studied in an experimental sessile drop furnace. Particles of approximately 20-60mg were placed on graphite substrates and then heated at a constant rate of 5°C/min up to 1830°C in a controlled gas atmosphere of Ar or CO. The shape of the particle was photographed with a digital video camera every second. It was observed that the melting behaviour can vary significantly, with some particles exhibiting a large softening/melting range. Selected samples were sectioned and then analysed with EPMA. The implications of the results on understanding industrial furnace operations are discussed.

Jan 1, 2007

By B. J. Buys

Rock bolt integrity is a critical issue for the mining industry because of its influence on the safety of mining operations. Guided ultrasonic wave testing of the defects associated with resin-anchored rock bolts was investigated. Axisymmetrical and three-dimensional finite element models were built, one of a partially encapsulated bolt and the other of a bolt with a simulated local corrosion crack. Experimental bolts were then installed in a testing block and typical responses were compared to finite element models of different defect scenarios. Encouraging results were obtained for the smaller axisymmetrical and three-dimensional finite element models, as well as during the experimental investigation. It is recommended that software with energy-absorbing elements should be utilized to consider higher frequencies and longer bolts. Once the integrity of models such as these has been established, the models could in principle be used to train neural networks for use in commercial equipment to determine the integrity of the installed bolt.

Jan 1, 2009