Research Outputs (Mining Engineering)

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For information on accessing School of Mining Engineering Research Articles content please contact : Salome Potgieter by email : salome.potgieter@wits.ac.za or Tel : 011 717 1961

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120 years of excellence in service to Mining.
(The Southern African Institute of Mining and Metallurgy., 2017-04) Musingwini, C.
The Wits School of Mining Engineering, which is celebrating 120 years of service to the mining industry, is the seed from which the University of the Witwatersrand grew, and is now the largest mining school in the English-speaking world.
Advancing international collaboration through the Global Mineral Professionals Alliance (GMPA).
(The Southern African Institute of Mining and Metallurgy., 2017-03) Musingwini, C.
Extract from Editorial: The GMPA is currently composed of six sister institutes: the Australasian Institute of Mining and Metallurgy (AusIMM), the Canadian Institute of Mining, Metallurgy and Petroleum (CIM), the Institute of Materials, Mining and Metallurgy (IOM3), the SAIMM, the Society for Mining, Metallurgy and Exploration Inc. (SME), and the Instituto de Ingenieros de Minas del Peru (IIMP).
The brighter side of career cyclically in the mining professions in South Africa.
(The Southern African Institute of Mining and Metallurgy., 2017-02) Musingwini, C.
Extract from Editorial: Mining professionals are generally in the fields of mining engineering, mineral processing, metallurgy, geology, and surveying. In order to enter a profession in the mining industry and follow an engineering career, a good mathematics and science education is required when exiting the high school system.
Cokriging for optimal mineral resource estimates in mining operations.
(The Southern African Institute of Mining and Metallurgy., 2014) Minnitt, R.C.A.; Deutsch, C.V.
Cokriging uses a sparsely sampled, but accurate and precise primary dataset, together with a more abundant secondary data-set, for example grades in a polymetallic orebody, containing both error and bias, to provide improved results compared to estimation with the primary data alone, as well as filtering the error and mitigating the effects of conditional bias. The method described here may also be applied in polymetallic orebodies and in other cases where the primary and secondary data could be collocated, and one of the data-sets need not be biased, unreliable, etc. An artificially created reference data-set of 512 lognormally distributed precious metal grades sampled at 25×25 m intervals constitutes the primary data-set. A secondary data-set on a 10×10 m grid comprising 3200 samples drawn from the reference data-set includes 30 per cent error and 1.5 multiplicative bias on each measurement. The primary and secondary non-collocated data-sets are statistically described and compared to the reference data-set. Variograms based on the primary data-set are modelled and used in the kriging of 10×10 m blocks using the 25×25 m and 50×50 m data grids for comparison against the results of the cokriged estimation. A linear model of coregionalization (LMC) is established using the primary and secondary data-sets and cokriging using both data-sets is shown to be a significant improvement over kriging with the primary data-set alone. The effects of the error and bias are filtered and removed during the cokriging estimation procedure. Thus cokriging using the more abundant secondary data, even though it contains error and bias, significantly improves the estimation of recoverable reserves.
Design principles for optimizing an established survey slope monitoring system.
(The Southern African Institute of Mining and Metallurgy., 2014) Mphathiwa, N.; Cawood, F.T.
When slope angles are designed during open pit optimization, there is a risk factor applied in steepening the slopes. The steepening of slope angles has implications for the safety and economics of the mining operation. The steeper the slope angles, the greater the probability of slope failure. Although a slope failure will result in added costs, the challenge is to compile an accurate cost-benefit exercise optimizing the economic benefits of the project without exposing mine workers and equipment to unacceptable risk of rockfalls. A balance between the safety of the operation and the economics of the investment is therefore required. The ideal situation is to have a slope monitoring system that will predict slope failure by detecting any ground movement before the actual failure occurs. This early warning will allow the risk factor to be applied with a high degree of confidence, knowing that the risk will be adequately mitigated. The objective of this paper is to provide guidelines on how to design an optimal survey slope monitoring system. It is the authors' view that for a survey monitoring system to yield desirable results, it should adhere to survey principles such as working from the whole to part and consistently cross-checking. The case study used is Jwaneng Mine, and the design strategy outlined can be used as a guideline for developing a new slope monitoring system or to optimize an existing one.
Determination of stable spans in UG2 excavations.
(The Southern African Institute of Mining and Metallurgy., 2018-05) Watson, B.P.; Gerber, R.
The hangingwall of the UG2 Reef is characterized by stratification in the form of thin and weakly cohesive chromitite stringers that can vary in number and height above a stope. These stringers, in conjunction with shallow-dipping thrust faulting, endemic across the platinum-bearing reefs of the Bushveld Complex, affect the maximum span that can be safely mined. The paper describes the research that was carried out to determine the interaction of support with the rock mass in both conventional and mechanized workings, and provides insights into stable span determination where excavations are intersected by a shallow-dipping thrust structure. Four important issues are highlighted. 1. Mine pole and pack support has a greater influence on stability than span in the context of the studied database for conventional mines. 2. Shallow-dipping discontinuities are a dominant feature in stability analyses. 3. The height of the vertical tensile zone does not restrict the fallout height if persistent shallow-dipping structures are present. 4. In the context of the numerical modelling shown in the paper, a span of 6 m is safe when 1.8 m long, full-column resin bolts are used at a support resistance of 48 kN/m2, regardless of the k-ratio or height of the triplets (intersections must be dealt with separately). Several leading practices have been developed in recent years to identify and timeously support hazardous structures.
Development of a computer-aided application using Lane's algorithm to optimize cut-off grade.
(The Southern African Institute of Mining and Metallurgy., 2016-11) Githiria, J.; Musingwini, C.; Muriuki, J.
The maximization of net present value (NPV) is a primary objective in open pit mine planning processes. In an attempt to meet this objective, cut-off grades are considered in all the stages of mining. There are three stages involved in resource extraction, namely mining, processing, and refining/marketing, which are all defined in Lane's approach. Using Lane's approach, the economics involved in each stage are identified independently and interact to provide an optimum cut-off grade. A hypothetical block model is used to illustrate how a computer application (Cut-off Grade Optimiser) that was developed in this study is used in the optimization of cut-off grades using Lane's algorithm. This paper analyses the application of Lane's approach for a single element in cut-off grade optimization as applied in the calculation of the optimum cut-off grade through a computer-Aided application. Although Lane's approach is not complex it is not widely applied to maximize the NPV of mining operations as the iterative calculations can be lengthy. The computer application developed in this study shows how Lane's algorithm combined with a linear programming function can optimize cut-off grade with regard to the complex situations faced by mining operations. The application saves users from performing otherwise lengthy, iterative calculations.
Empirical correlation of mineral commodity prices with exchange-traded mining stock prices.
(The Southern African Institute of Mining and Metallurgy., 2011-07) Nangolo, C.; Musingwini, C.
Mineral commodity prices comprise one of the key criteria in the selection of mining stocks. We contend that of the three principal elements of mineral commodity prices, spot price, forward price and long-term price, one has a greater impact on the share valuation processes used by investors. This research paper examines the extent to which each of these elements influences the valuation process. The intention is to provide investors in mining stocks with a greater understanding of how fluctuations of commodity prices over time affect the prices of the mining stocks they hold, or intend to sell or buy. Three mineral commodities, gold, silver, and copper, were used as case studies, since market data on these commodities is readily available in the public domain. Nine market indices covering all three mineral commodities were selected. These are based on clearly defined criteria with the intention of eliminating ambiguity and to test for correlation with the three sets of mineral commodity prices. Nine mining companies, which were not the primary drivers of the relevant indices employed in the study, were used to validate the results obtained from the indices in order to avoid duplication of the same correlation during cross-checking. Each commodity price was adjusted for operating costs. For each market index, an average operating cost was calculated from the companies comprising its basket, while each company's annual operating costs were used for the stocks of the individual companies examined. The data was collected for the period January 2004 to October 2010. This period was further split up into three sub-periods to account for the Global Financial Crisis (GFC) period that started in mid-2008. We conclude that mining stock prices are correlated with mineral commodity prices, but with spot and forward prices exhibiting stronger correlations than long-term price. This finding should be useful for evaluation purposes. Where cash flow methodologies such as discounted cash flow or earnings per share are used to value ordinary shares and commodity prices are required to estimate future cash flows, the findings suggest that spot prices should be used as opposed to long-term prices. The work reported in this paper is part of a current MSc research study at the University of the Witwatersrand.
Estimating cost of equity in project discount rates: comparison of the Capital Asset Pricing Model and Gordon's Wealth Growth Model.
(The Southern African Institute of Mining and Metallurgy., 2016-03) Nhleko, A.S.; Musingwini, C.
Since the Global Financial Crisis (GFC) in mid-2008, capital has been more difficult to access. Mining projects must contend with projects from other industries for scarce capital. A decision to invest available capital in mineral projects requires that valuation be conducted to assess the expected return on the projects. The discounted cash flow (DCF) analysis is generally applied for the valuation of mining projects, whereby future cash flows are discounted to present value using an appropriate discount rate. The discount rate significantly affects the outcome of a valuation. Economic and finance theory provides tools to calculate discount rates. The discount rate must account for factors such as the risk and stage of development of the mineral project; hence the appropriate discount rate to utilize in a project is often a subject of debate. The discount rate is the weighted sum of the cost of debt and equity. There are several methods for determining the cost of equity. This study considers the commonly applied Capital Asset Pricing Model (CAPM) and Gordon's Wealth Growth Model because of their simplicity and availability of parameters required to estimate the cost of equity. This study explores how differences in the cost of equity obtained by these two methods can be explained for a mining environment. Data for empirical analysis were collected from the I-Net Bridge, McGregor BFA, and Bloomberg databases. It was found that Gordon's Wealth Growth Model provides better estimates of the cost of equity compared to the CAPM under depressed market conditions. Therefore, this research recommends that Gordon's Wealth Growth Model be used to estimate the discount rates for mining projects during periods of depressed market conditions.
Estimating mine planning software utilization for decision-making strategies in the South African gold mining sector.
(The Southern African Institute of Mining and Metallurgy., 2015-02) Genc, B.; Musingwini, C.; Celik, T.
This paper discusses a new methodology for defining and measuring mine planning software utilization in the South African gold mining sector within an evolving data-set framework. An initial data-set showing the mine planning software providers, their corresponding software solutions, as well as the software capabilities and information on the number of licences was collected and compiled in 2012 in an online database for software utilized in the South African mining industry. Details of the database development and implementation were published in the Journal of the Southern African Institute of Mining and Metallurgy in 2013. In 2014 the data-set was updated with additional and new information. Using the 2012 and 2014 timestamps, a methodology for estimating the software utilization was developed. In this methodology, the three variables of commodity, functionality, and time factor were used to define and measure the software utilization in order to ultimately inform decision-making strategies for optimal software utilization. Using six different functionalities, namely Geological Data Management, Geological Modelling and Resource Estimation, Design and Layout, Scheduling, Financial Valuation, and Optimization, utilization in the gold sector was measured. This paper presents the methodology employed for measuring the mine planning software utilization. The methodology is useful for stakeholders reviewing existing software combinations or intending to purchase new software in the near future and who want to estimate the comparative attractiveness of a certain software package. These stakeholders include mining companies, consulting companies, educational institutions, and software providers. The work presented in this paper is part of a PhD research study in the School of Mining Engineering at the University of the Witwatersrand.
First cycle experience of a business process re-engineering programme at Shabanie Mine.
(The Southern African Institute of Mining and Metallurgy., 2005-04) Musingwini, C.; Muzoriwa, C.; Phuti, D.; Mbirikira, D.
In the past ten to fifteen years, many organizations have applied business process re-engineering (BPR) to significantly improve their business competitiveness or stave off closures. The mining industry in Southern Africa is no exception and documented examples can be drawn from South Africa. Although the concept is superficially simple, its application has been marked by a high failure rate of about 70 per cent because it has been generally misunderstood. Shabanie mine, a chrysotile asbestos fibre producer in Zimbabwe took cognisance of this fact by cautiously embarking on a modular BPR programme in October of 2002. A year was used as a complete cycle or module for re-evaluation of the programme. Shabanie mine adopted BPR as part of management efforts to remain competitive amid serious threats to operational viability. These threats included hyper-inflation driven rising production costs, a declining world asbestos market and a possibility that Russia could take over the shrinking world asbestos market by dumping low-priced asbestos fibre. The only competitive advantage that the mine had was the high quality of its long-fibre chrysotile asbestos. The major BPR thrust was therefore to redesign processes for improved productivity and ultimately achieve a lower cost per ton of final asbestos fibre product. In addition, corporate culture change and cost-saving were also factored into the programme. This paper discusses the implementation experience of the BPR programme at the mine. The main BPR beneficial highlights are improved productivity, sizeable cost-savings, positive corporate culture change and identification of secondary projects. One of the lessons learnt from this programme is that mining companies will have to deal with the HIV/AIDS pandemic if they are to sustain high levels of productivity into the future.
A forward-looking Young Professionals Council (YPC).
(The Southern African Institute of Mining and Metallurgy., 2017-04) Musingwini, C.
Extract from Editorial: The holistic development of young professionals is critical for the future of our Institute and the industry. The SAIMM’s mentoring programme, which connects young professionals with experienced practitioners in a one-to-one mentoring relationship, is in its second year of existence. Our programme has matched 82 protégés to 64 mentors. This is a truly global programme because the registered participants are from different countries including the UK and USA. This programme allows young professionals to build connections and develop into future leaders of our mining industry.
Just-in-time development model for a sub-level caving underground mine in Zimbabwe.
(The Southern African Institute of Mining and Metallurgy., 2003-04) Musingwini, C.; Minnitt, R.C.A.; Phuti, D.; Makwara, F.
Traditionally, mineral reserves management at most underground mines in Zimbabwe focus on maintaining large mineral reserves so that the time between development and production is as long as possible. Historical data at Shabanie mine, a Zimbabwean sub-level caving underground mining operation, confirms this practice. However, the high cost of underground development means that the luxury of large buffer mineral reserves cannot be justified. Furthermore significant increases in the costs of production, exacerbated by the current unfavourable economic climate, make the wisdom of extending development workings well ahead of use questionable. Poor ground conditions at Shabanie mine, mean that some development ends have to be re-mined two or three times due to partial or complete closure between the time they are mined and the time they are utilized. In order to reduce the inordinately high support costs associated with closure of development ends a new 'Just-in-time' (JIT) approach that provides development ends as and when they are needed, has been adopted. Accordingly a model to determine an appropriate 'just-in-time' rate of development has been created. The JIT development model indicated that the mine could reduce development rates from 330 m/month in 2001, to 160 m/month in 2002 and achieve savings of about 50% on annual support costs, but still assure customers of a long-term product supply. The mine accepted the model in November 2001 and began implementing it in 2002. Results of the implementation will be reviewed in 2003.
The last 100 days in the office of the SAIMM presidency.
(The Southern African Institute of Mining and Metallurgy., 2017-08) Musingwini, C.
Extract from Editorial: In the SAIMM we have a rich tradition of leadership succession. Before one becomes President, one must have served at least two years on the SAIMM Council, followed by a year of co-option as an Office Bearer before successively becoming Junior Vice-President, Senior Vice-President, President-Elect, and President; After the term as President, one becomes Immediate Past-President and finally retires back onto Council as a Past President.
Mine of the future - A mining CEO's perspective.
(The Southern African Institute of Mining and Metallurgy., 2017-05) Musingwini, C.
Extract from Editorial: The mining CEO of the future will be a strategist capable of navigating complex integrated stakeholder management, forging sustainable win-win partnerships, and enforcing regulatory adherence and good governance. Such a CEO is likely to succeed as he or she can enlist the support of shareholders, governments, employees, and communities that are increasingly, and rightfully, demanding to share in the benefits of the resources mined in their jurisdictions.
Mine Planning and Equipment Selection (MPES 2015).
(The Southern African Institute of Mining and Metallurgy., 2016-03) Musingwini, C.
Extract from Comment: The Southern African Institute of Mining and Metallurgy (SAIMM) hosted the 23rd International Symposium on Mine Planning and Equipment Selection (MPES 2015) at the Sandton Convention Centre in Johannesburg from 9 to 11 November 2015. This was the first time that South Africa has hosted the MPES in its 25-year history. This conference’s theme was ‘Smart Innovation in Mining’ in order to recognize technological innovations and new ideas that are required to prepare the industry for the mine of the future.
Modelling open pit shovel-truck systems using the Machine Repair Model.
(The Southern African Institute of Mining and Metallurgy., 2007-08) Krause, A.; Musingwini, C.
Shovel-truck systems for loading and hauling material in open pit mines are now routinely analysed using simulation models or off-the-shelf simulation software packages, which can be very expensive for once-off or occasional use. The simulation models invariably produce different estimations of fleet sizes due to their differing estimations of cycle time. No single model or package can accurately estimate the required fleet size because the fleet operating parameters are characteristically random and dynamic. In order to improve confidence in sizing the fleet for a mining project, at least two estimation models should be used. This paper demonstrates that the Machine Repair Model can be modified and used as a model for estimating truck fleet size in an open pit shovel-truck system. The modified Machine Repair Model is first applied to a virtual open pit mine case study. The results compare favourably to output from other estimation models using the same input parameters for the virtual mine. The modified Machine Repair Model is further applied to an existing open pit coal operation, the Kwagga Section of Optimum Colliery as a case study. Again the results confirm those obtained from the virtual mine case study. It is concluded that the Machine Repair Model can be an affordable model compared to off-the-shelf generic software because it is easily modelled in Microsoft Excel, a software platform that most mines already use. This paper reports part of the work of a MSc research study submitted to the University of Witwatersrand, Johannesburg, South Africa.
The modern mining professional - A mining CEO's perspective.
(The Southern African Institute of Mining and Metallurgy., 2017-06) Musingwini, C.
Extract from Editorial: Lower commodity prices compounded by low productivity continue to be challenges that severely affect the global competiveness of the country’s mining industry. These challenges require us as an industry to continuously explore effective cost-containing strategies. It is therefore imperative that we regularly optimize and build flexibility into our business systems, respond to these challenges, and leverage the role of new technology and mechanization into our production processes so that we can mine more safely and productively.
Multi-seam mining of the deep Waterberg resources.
(The Southern African Institute of Mining and Metallurgy., 2016-11) Chabedi, C.K.; Zvarivadza, T.
This paper discusses the difficulties associated with the potential exploitation of the deep multi-seam resources east of the Daarby fault in the Waterberg coalfield. The resources occur at a depth greater than 250 m and the thickness of the coal is roughly 110 m, but the top 50 m comprises coal intercalated with shale and the bottom 60 m contains five seams with sandstone and shale partings. Various factors affecting multiple seam mining at these great depths are discussed with reference to lessons learned from local and international experience on multi-seam mining. Field geological and geotechnical data was utilized to assess the stability of the roof of the seams. There is no specific rock mass rating for the Waterberg area, therefore approximate coal mine roof rating (CMRR) values were used to propose appropriate support strategies. Analysis of Multiple Seam Stability (AMSS) was used to analyse the strength of the parting or interburden between the various seams, the mining sequence, and the interaction between the various seams. The research indicated that it is possible to mine seams with a low CMRR at high mining rates using longwall mining, although support for gateroads is expected to be expensive, time-consuming and onerous to install, and will impact gateroad development rates. It will not be possible to simultaneously mine zones in close proximity and failure of the interburden is predicted, thus dangerous mining conditions are anticipated. However, it will be possible to mine just two of the eleven zones using longwall mining.
The NDP vision 2030-does the SAIMM have a role to play?
(The Southern African Institute of Mining and Metallurgy., 2017-01) Musingwini, C.
Extract from Editorial: We are making our contribution to socio-economic transformation in a number of ways. Our Scholarship Trust Fund ensures that we continue to assist undergraduate students from poor backgrounds to obtain a university education in mining and metallurgy-related fields, thus contributing towards poverty reduction.

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