School of Mining Engineering (ETDs)
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Item Quantification of uncertainty associated with 4E assay results from reverse circulation sampling of the middlegroup seams at Tharisa mine(University of the Witwatersrand, Johannesburg, 2024) Ramusi, Matlala MaryAgnesThis research explores the sources of discrepancy between platinum, palladium, rhodium and gold (4E) g/t in Reverse Circulation (RC) drilling samples and Diamond Drillhole (DDH) samples, ultimately defining the applicability of RC drilling on the narrow seams of the Bushveld Middle Group at Tharisa Mine. The research also quantifies the sampling and analytical uncertainty associated with the 4E g/t grades in RC samples through measurement and statistical approach. Twin-hole drilling is used where RC holes are drilled within a 10m radius of the DDH to understand and to demonstrate the difference between the seam intersections of RC sampling in relation to DDH. Sampling uncertainty was quantified by using replicate samples. Analytical method uncertainty was quantified by using Quality Assurance Quality Control (QAQC) data, blank samples, certified reference materials (CRMs) and duplicate samples. Two-way laboratory diamond drillholes (DDH) check samples and two-way laboratory RC check samples were used to determine the accuracy and repeatability of the analytical methods. The research identified two main sources of uncertainty in the 4E analyses; • Sampling method errors as the highest contributor to the uncertainty in the 4E assay results. • The difference in the analytical methods contributes to the difference in the 4E grades in RC and DDH. The identified issues can be resolved by re-designing the sampling method and procedures under the guidance of Theory of Sampling (TOS) principles. Analytical methods and procedures need to be improved for accurate reporting of assay results.Item Analysing the progress of skills development necessary for mineral beneficiation in the gold mining industry: a case study of harmony gold’s Moab khotsong mine(University of the Witwatersrand, Johannesburg, 2024) Nengwenani, Shumani Maemu; Mtegha, H.The mining industry of South Africa is a cornerstone of the country’s economy, having contributed over 8% to the national gross domestic product in 2022. The mining industry has been responsible for major economic growth and job creation due to its mineral resource abundance. However, the socio-economic impact of this industry on communities has fallen short of expectations. The objective of the South African beneficiation strategy is to transform the country’s mineral wealth into competitive economic advantage through the promotion of economic diversification, industrialization, and job creation. The aim of this research is to determine progress made by the mining sector in skills training and development necessary for local mineral beneficiation, particularly in the gold mining industry. This is training provided through the achievement of formal qualifications such as a National Certificate in Jewellery Manufacturing, a Diploma in Jewellery design and Manufacture, as well as through the accumulation of skills such as jewellery processing, wax carving for jewellery, die stamping for jewellery, industrial design for jewellery, and jewellery evaluation. The reaserch also includes a critical reviews the company’s training initiatives within the context of the beneficiation skills pipeline, the National Skills Development Strategy, and the sector skills plan, which are all key elements of the National Growth Plan and the relevant Sector and Training Authorities. Harmony Gold company has shown commitment to socio-economic objectives through the implementation of numerous beneficiation projects, such as the Musuku Beneficiation Systems, the Harmony Jewellery School, the Oro-Maska Project, and the SARM project. While these initiations did not have long-term success, they indicate the company’s willingness to play a role in promoting skills transfer and in mineral beneficiation. The short-term success of these initiatives also highlights the complexities involved, underlining the need for proper planning, proper resource allocation, as well as the need for constant and consistent stakeholder engagement. A significant finding of this research is the identification of a skills gap, especially in areas crucial for mineral beneficiation. Despite existing efforts and policy frameworks like the Skills Development Act 97 of 1998, the remains a need for more targeted training and skills development programs. The existing skills gap must be addressed to maximize the mining sector’s contribution to national development objectives.Item Evaluation of the Performance of the BlastLogic Software in Predicting Blasting Fragmentation Distribution in Surface Mines(University of the Witwatersrand, Johannesburg, 2024) Munkombwe, Milton; Uludag, ErhanSurface mining is a crucial aspect of the mining industry, and one of the most significant factors that affect profitability and efficiency in mining operations is fragmentation. The traditional approach to fragmentation in surface mines involves the use of explosives, which generates a particular fragmentation profile that may not always be targeted size. The objective of this study was to evaluate the performance of the BlastLogic software in predicting fragmentation distribution in surface mines. This was in comparison with Swebrec, Kuz-Ram and Split-Desktop fragmentation results. Drill pattern designs are created (burden, spacing and hole position) in other design parameter software e.g., Maptek Vulcan, and Micro-station. These patterns are optimised in the BlastLogic software package. It uses advanced algorithms and models to simulate and predict the effects of different blasting parameters on fragmentation. The study was conducted on 5 surface mines. These were Mogalakwena Platinum Mine, Kolomela Iron Ore Mine, Sishen Iron Ore Mine, Isibonelo Colliery, and Navigation Colliery. The study involved collecting data on the existing fragmentation profile in the mine and the geological characteristics of the ore body. The data was then used to evaluate the performance of the BlastLogic software in predicting fragmentation distribution. The blasting parameters used to achieve this were blast hole diameter, burden and spacing, powder factor and geotechnical factors such as the geology of the rock to be blasted. By accurately predicting the fragmentation size, engineers and blasting experts can design the blast parameters, such as hole diameter, spacing, and powder factor, more precisely. This allows for better control over the size distribution of the blasted material. Also, knowing the expected fragmentation size allows for the selection of an appropriate amount of iii explosive energy. Using too much energy can lead to excessive fracturing and finer fragmentation, while too little energy can result in larger rock fragments. Proper energy management helps achieve the desired size distribution. The findings of this research demonstrated that the predicted fragmentation distribution created by using BlastLogic software is more effective and profitable than the conventional method. The predicted fragmentation size reduced the amount of oversized material generated during blasting, thereby improving the recovery rate of valuable minerals. The results showed that there were less than 15% of fines produced, with an insignificant amount of oversized material less than 5% for all surface mines under study. In conclusion, the study evaluated the use of BlastLogic software in predicting fragmentation distribution. The study further highlighted the results of vibration and overpressure results obtained from these improved designs from BlastLogic. It was evident that BlastLogic software is a valuable tool for improving the efficiency and profitability of mining operations. The software offered a more accurate and reliable method of predicting and improving blasting fragmentation distribution for surface mines.Item Geostatistical Modelling of Floor and Roof Hazard Data in the Highveld Coalfield – A New Denmark Colliery Case Study(University of the Witwatersrand, Johannesburg, 2024) Hall, QuintinNew Denmark Colliery (NDC) is an underground coal mine located between Standerton and Bethal in the Mpumalanga province of South Africa. Due to the nature of the coal seam and the mining method in the research study area, mining operations are in constant contact with floor and roof lithologies which introduce operational challenges. To mitigate these challenges floor and roof hazard plans are used for operational planning purposes. Existing floor and roof hazard plans are deficient of both sound theoretical and procedural formality in their construction. This lack of formality in the hazard modelling was most concerning. The research establishes a methodology for the generation of meaningful floor and roof hazard plans from empirical and theoretical applications to both interpreted and measured variables relevant to the floor and roof hazards encountered. This methodology; developed for easy operational implementation, is supported by a formal system of procedures that allow for continuous updating, validation and monitoring. The quantitative and qualitative hazard data available in the study area required bridging. For this, the author introduces the concept of applying scorecards to the hybrid data and develops the scoring logic to convert the hybrid hazard information to numeric values, usable in quantitative analyses. The estimation software in place at NDC is limited to inverse distance weighting (IDW). The research therefore sought to determine whether the application of this classical technique would suffice for the creation of hazard plans. IDW, ordinary kriging and conditional sequential Gaussian simulation were applied to measured structural variables. The estimation results were visually compared. This would then confirm the suitability of applying IDW to the research data. The research takes a turn when the hazard scorecard numbers become the focus of the research as opposed to the structural variables. Floor and Roof hazard scores are individually classified, respectively representing either iv “competent”, “moderately competent” or “incompetent” floor conditions and “normal”,” cautionary” or “high risk” roof conditions. An innovative method of defining hazard indicators sets is introduced. IDW estimation is applied to each hazard indicator set. Results are interpreted, and inflection points on the slopes of the cumulative distribution plots of the estimates are used to identify cut-off values to clearly distinguish the hazard conditions mentioned. Resulting in updated Floor Hazard and Roof Hazard Plans for NDC aligned to a formal analytical process and estimation methodology. With this in place, the research goals were accomplished through the construction and validation of reliable and easily implementable floor and roof hazard plans. Procedures for applying hazard scorecards to newly drilled boreholes and for updating the hazard models appear in the Appendices.Item Quantification of the benefits of pumpable emulsion explosives in narrow reef gold mines(University of the Witwatersrand, Johannesburg, 2024) Chosi, Ramphele LordwickPumpable emulsion explosives usage is gaining ground in South African underground narrow reef mining following its wide application on the surface and underground massive mining. Following the advancement in the narrow reef, this research sought to quantify the benefits of pumpable emulsion explosives in narrow reef stopes of gold mines under non-trial conditions on three key performance areas (KPA) of cost of explosives, blasting efficiency and post-blast conditions. The study adopted both qualitative and quantitative methodological approaches where historical and primary data was collected at the identified underground shafts of Ya Rona and Hlanganani. Historical data included planned targets and achieved results before and after the introduction of pumpable emulsion explosives at the shafts. The primary data was gathered through a total of 33 underground observations at the two shafts. The analysis of three KPAs was done through corresponding KPIs of explosives cost, face advance, powder factor, fragmentation distribution, and hangingwall overbreak. The cost of explosives KPA analysis indicated that pumpable emulsion was cost-effective when compared to cartridge explosives and the planned target. The blasting efficiency KPA was analysed through three KPIs, namely, face advance, powder factor, and fragmentation. The primary data analysis showed that the pumpable emulsion explosives were capable of achieving the mine’s required face advance at both shafts, and the historical data analysis showed that pumpable emulsion explosives performed better at the Ya Rona shaft and poorly at the Hlanganani shaft. The pumpable emulsion explosives powder factor calculated iii from the underground measurements can be lower or higher than the corresponding planned powder factor due to in-situ site conditions. Blast fragmentation analysed images showed that pumpable emulsion explosives can achieve the mine expected range fragmentation size or be below as indicated by the two image analysis programmes used and the Kuz-Ram estimation. Post-blast conditions were analysed using the hangingwall overbreak which cautiously showed that emulsion explosives have the potential to negatively impact the panel's post-blast condition due to non-adherence to the blast design parameters and the influence of the geological conditions. The research KPAs of cost of explosives, blasting efficiency and post blast conditions through the respective KPIs have indicated that emulsion explosives could achieve blast outcomes that were within the mine target. The analysis of the cost of explosives, face advance and powder factor KPIs conclusively showed the positive outcome pumpable emulsion explosives could have in narrow reef mines; though the powder factor showed dependence on other factors. The analysis of hangingwall overbreak KPI revealed a possible negative impact, while the analysis of the fragmentation KPI yielded an inconclusive outcome. Based on the results, the study proved the effectiveness of pumpable emulsion in narrow reef stope mining under non-trial operational conditions. It also quantified the benefits of pumpable emulsion explosives in narrow reef gold mines. Notwithstanding, it is recommended that further research on fragmentation analysis using different analysis methods and more research on the extent of the hangingwall damage when pumpable emulsion explosives are used should be conducted.Item A Review of the Stope Support System at Impala Bafokeng North Shaft Owing to Stope Closure at Shallow Mining Depths(University of the Witwatersrand, Johannesburg, 2024) Walsh, Trevor; Stacey, ThomasImpala Bafokeng’s North Shaft is a shallow platinum mine on the western limb of the Bushveld Igneous Complex. Shallow mines experience very little horizontal stress which leads to a support issue of the tensile zone. North Shaft relies heavily on mine pole support due to the requirements for a stiff support system. Elongate support failure in the deeper parts of the mine have occurred due to a change in the loading environment. The support failure has resulted in inadequate support resistance in the back areas and some large falls of ground. In this research report the Hybrid Section stope closure rate was measured. The closure does not appear to be linked to a detachment of a hangingwall parting. The ground penetrating radar scans and borehole data correlate with the observations. The falls of ground are structure related and occur in the back areas of the panel after the elongate support had failed. The footwall material is weaker than the hangingwall material and the pillar punches into the footwall. The footwall fractures and tensile cracks in the panel footwall indicate that the stresses are forced to move horizontally due to the footwall 4 parting plane. The footwall thrusts into the panel causing the high closure observed. The combination of a shorter panel length and pencil sticks would provide adequate support for the high closure rates observed.Item Support Design for Wide Stoping Heights Resulting from Footwall Lifting of Previously Mined Merensky Panels(University of the Witwatersrand, Johannesburg, 2024) Tati, Buntu BantuThis research report is based on project work conducted at Impala Platinum Mine No. 20 Shaft. The purpose of the project was to provide suitable support and an extraction sequence to mine a mineralized zone in the footwall of previously mined Merensky Reef stopes. An estimated 1.4 kt of ore was available at an average grade of 1.75 g/t (68 000 ounces) at this shaft. A geotechnical investigation was done to gain an understanding of the footwall Pegmatoid mineralization as well as the structural characteristics of the rockmass. A footwall lifting method needed to be developed that incorporated a support system that was based on sound design principles. A tendon and cement pack support system was determined through both a deterministic and a probabilistic key block approach. The support design was limited to local pane support and did not include pillar behaviour. Cable anchors were the selected replacement units for timber elongates removed by the footwall extraction method. A cable anchor length greater than the anticipated fall- out height of 1.77 m was required. The analysis showed that the support length had a much smaller effect on rock fall-out results than the support spacing. Cable anchors spaced 1.5 m x 2.0 m with a length of 2.5 m were determined to be the optimal support configuration for stability. Despite this finding, only 3.5 m long cable anchors were readily available at the No 20 Shaft and were subsequently used in the trial. The Trench and Retreat Mining Method was used in the trial over three months. During this period, a proof of concept was developed for the support and extraction method. Various recommendations are provided in this report to enhance the methods and better optimise extraction in the long term.Item The relationship between human factors and technology adoption at Sishen Mine(University of the Witwatersrand, Johannesburg, 2024) Seabela, Mogaleadi; Twala, PontshoMining of raw materials and minerals started centuries ago in South Africa. Mining methods, then, were very primitive and labour-intensive with the use of slaves in some instances. With industrial revolution came the development of other industries and supply chain process between industries which gave rise to human civilization and improvement of people’s livelihoods. The mining industry progressed as an adopter of technology with operations moving from mechanisation to digitisation. People however remained an integral part of the industry and in the case of South Africa, that is going to be the case for the foreseeable future. South Africa has a high unemployment rate and the mining industry employs approximately half a million people and Sishen Mine employs about 10 000 people. Given the role of mining in the country, it is important that adoption of technology and digital revolution take into consideration human factors in order to be successful. Some of the challenges the mining industry is faced with that requires the adoption of technology, include safety of employees, depleting orebodies and declining commodity qualities, rising input costs, supply chain constraints and macro-economic factors such as competitive commodity markets. To address some of these challenges, the mining industry is adopting technology and there has been significant benefits realised in the safety of mines. Sishen Mine strives towards zero harm and achievement of hundred percent overall equipment efficiency in order to remain sustainable. With technology, there has been some progress in reducing fatalities but there are still significant safety incidents taking place even in areas where technology was implemented to prevent such incidents. The aim of this research was to investigate the impact of human factors on the adoption of technology at Sishen Mine. The objectives of the research were to identify benefits and challenges to adoption of technology and investigate factors that support and/or hinder technology adoption. Another objective was to establish the gaps in the implementation of technology in consideration of the impact human factors have on adoption of technology. Literature studies on mining technology, human factors and how they affect adoption of technology was conducted and found that human factors play a crucial role in the success of technology adoption. Several technologies employed at Sishen Mine were studied and their OEMs interviewed to share the benefits of these technologies and how they performed at Sishen Mine. Mine employees were also interviewed to share their personal experiences of technology in their work. It was found that human factors do have an impact on technology adoption. Key findings were that the benefits of technology were fairly understood and some of the challenges to adoption of technology at Sishen Mine related to human factors. The results showed that there were gaps in the capability of the technologies under study and the benefits realised in Sishen Mine. Some of the gaps included lack of understanding of how the technology worked and inadequate buy-in from end-users due to fear of job losses and inadequate engagement of all stakeholders. It is recommended that human factors are considered during technology implementation for successful technology adoption. This must be supported by adopting the design thinking approach to problem-solving wherein all stakeholders will be engaged on the technology solution before it is implemented. This will drive buy-in and address the human factors that may hinder the adoption of technology. Another recommendation is that a thorough management of change process be employed to cover technology implementation and adoption from the start of the process to the support provided by OEMs post installation, in order to ensure full adoption and integration into the operating model.Item Impact of secondary rock-breaking equipment availability on mining plan in block cave mining(University of the Witwatersrand, Johannesburg, 2024) Nyarela, Martin SphiweBlock caving is one of the massive mining methods that has become increasingly popular due to its low operating cost, improved safety, and high production output. The low operational cost is attributable to minimal blasting, which is only focused on secondary rock-breaking activities. Once caved, the material flows continually and is loaded from the drawpoint to the tipping areas using LHDs and other means, such as scraper winches. Different rock fragmentations register in the drawpoint as loading continues. The sizes range from fine to medium fragmentation and the undesirable oversized rocks that cause hang-ups and blockages. Blockages and hang-ups disturb the flow of material, which negatively impacts compliance with the mining plan and draw control schedule. The hang-ups are treated with secondary rock-breaking equipment to make drawpoints available for loading. However, if the mechanical availability of rock-breaking equipment is low, drawpoints remain idle beyond acceptable limits. Additionally, factors such as the availability of experienced miners to address challenging hang-ups, in instances where treated hang- ups remain unresolved as a result of treatment failure, and the prioritisation of adjacent draw points for loading to restore macro material flow, especially in cases of high hang- ups, can significantly contribute to longer idle periods as well. In this regard, this research aimed to understand the impact that secondary rock-breaking equipment has on the mining plan at the PMC block cave. The research conducted an empirical study of the Secondary Breaking Unit, which forms part of the Mining Operations responsible for all secondary rock-breaking activities at the Palabora Mining Company (PMC). The secondary rock-breaking equipment types that this study investigated include the Medium Reach Rigs, Water Cannons, and Mobile Rock-Breakers. A 52-week data obtained from PMC was used for this study, covering iv the period from January to December 2021. The data pertain to secondary rock- breaking equipment availability and utilisation, cave availability, loading compliance, downtime contribution factors, and in-situ grade. The correlation and regression analysis methods were used for the analyses of data to answer the research questions. In this study, the copper content derived from the mined tonnes and in-situ grade was used as a proxy for the mining plan and it excludes uncontrollable factors such as recovery, pricing, and exchange rates. Firstly, the study sought to determine whether the PMC’s Lift 1 block cave is behaving as predicted and it was concluded that it is. Secondly, the study sought to determine if there is a relationship between the mining plan, using the deviation from the mining plan, and cave availability and loading compliance respectively. It was established that the correlation between the deviation from the mining plan and cave availability was not strong enough whereas the correlation between the deviation from the mining plan and loading compliance was strong enough to derive a predictive equation which was validated. Thirdly, the research sought to establish the minimum acceptable rock-breaking equipment availability at PMC. It was found that the minimum acceptable availability was cautiously 60% based on the historical data. Fourthly, the research sought to determine the research strategy that can improve the rock-breaking equipment availability from the low of 42% in 2021 to at least 60%. The mine’s target availability is 65%. To achieve this, categories of downtime for MRR, MBR and WC with high impact were identified using the Pareto principle. The maintenance overrun downtime category which was one of those with a high-impact downtime was found to be common in all three equipment types with a combined duration of 10 695 hours or 44.4 days per operational equipment per year. In this regard, the Schedule Maintenance strategy was suggested.Item Open pit optimisation using monte carlo simulation: a case study of kolomela mine(University of the Witwatersrand, Johannesburg, 2024) Nkambule, Sthembile; Tholana, TinasheIron ore grade and price are among the input variables in the open pit optimisation process. Kumba Iron Ore (KIO) uses the widely used deterministic approach whereby average input variables are used to determine open pit limits. This approach assumes that the estimated variables are known with certainty. However, the input variables are associated with uncertainty. For example, the grade of a mineral deposit is estimated by interpolating relatively limited data from exploration drilling results. This means that the estimated grade is not entirely a true representation of the entire mineral deposit. This can be a significant source of uncertainty. Also, iron ore prices have proven to be highly variable in the past years which can also be a significant source of uncertainty. If uncertainty of these two variables is not well understood and quantified, this can result in sub optimal or overly estimated pit limits. The effect of not understanding uncertainty can lead to poor decisions that can result in loss of revenues or additional cost and thus can impact the net present value (NPV) and life of a mine (LOM) of a mineral project. KIO, like all mining companies, is increasingly concerned with the effects of risk on NPV because of the chosen final pit shells. The aim of this research was to model the uncertainty of iron ore price and grade associated with open pit optimisation. Isatis software was used to produce ten realisations of the case study orebody and Monte Carlo Simulation was used to model iron ore prices. The economic block values of the ten block model realisations were calculated using four prices which were P75, P50, P25 and P5. The ‘P’ in P75, P50, P25 and P5 refers to probability of exceeding a certain iron ore price point. A P50 value is a median value, which means that it is expected that 50% of the time, the iron ore price will be above the P50 value, and 50% of the time, it will be below the P50 value as simulated from @Risk software. Forty pit shells and high-level schedules were then generated using Deswik Pseudoflow. NPVs of the forty pit shells were determined and were compared to the NPV of the deterministic pit shell. The study showed that there are benefits in doing probabilistic iron ore grade estimation as opposed to deterministic estimation. The highest difference in ore tonnages between the deterministic block model and the simulated block models was 15%. The probabilistic pit shell with the highest ore tonnages had lower strip iv ratios and an additional year of mining. This resulted in the pit shell producing the highest NPV. Results of the study also showed that iron ore price has a huge impact on NPV. The P5 price ($170.89/t), which was the highest price with a low probability, produced bigger pit shells and higher NPVs. The P75 price ($70.84/t) which was the lowest price with higher probability, produced smaller pit shells and lower NPVs when compared to NPV of the deterministic pit shell produced at $78.5/t. The study interpolated NPVs of the probabilistic pit shells and showed that KIO deterministic pit shell was planned at P71. This shows that KIO is very conservative in their mine planning. It is recommended that probabilistic pit optimisation be done for all pits at Kolomela Mine. In addition to iron ore grade and price, it is recommended that uncertainty of all pit optimisation input parameters be modelled. It is also recommended that the methodology demonstrated in this study be used also at Sishen Mine. Finally, it is recommended that KIO should implement this methodology annually before their medium-term planning process to assess uncertainty during pit optimisation.