School of Mining Engineering (ETDs)
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Item Key block theory for the miner: a novel simplified method for determining block removability(University of the Witwatersrand, Johannesburg, 2024) Van Rooyen , Christiaan; Stacey, T.R.Rock falls driven by gravity cause the most injuries and deaths in the South African underground mines. Discontinuities such as joints define most rocks that are free to fall. Key block theory describes how to decide if a rock defined by joints can move into an excavated space. Key block analysis requires complex calculations and many iterations to reach such a decision. The complexity of applying key block theory restricts its routine use. Although there are several methods that address some of the shortcomings of key block theory, none address the complexity of its underlying calculations. The main drive of this research project was to find a method to judge rock block removability that is simple enough to enable the routine application of key block theory in mining. The new gravitational removability theorem described in this report satisfied the need for simplicity. A comparison between the gravitational removability method and the edge vector method on many generated blocks yielded a fair correlation in terms of removability, but less so in terms of non-removability. The definition and application of a set of calibrating geometric conditions in conjunction with the gravitational removability method resulted in a perfect accounting of all the synthetic blocks. The gravitational removability method proved effective in identifying rotational removability as well. This research report presents the new gravitational removability theorem, equations to calculate the gravitational removability number and a set of geometric conditions that allows the judgement of removability of a block with no, or minimal calculation.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 A critical investigation into the creation of special economic zones in South African mining areas(University of the Witwatersrand, Johannesburg, 2024) Phambane, Maureen; Leeuw, PasekaThe Bushveld Complex (BC) hosts the largest known deposits of platinum group metals (PGM) bearing ore in the world, divided into the Eastern Limb, Western Limb and Northern Limb. The three largest PGM producers include Sibanye Stillwater, Impala Platinum and Anglo-American Platinum and they have operations spread around the BC. With this endowment, the opportunity exists for South Africa to not only be just a producer country and exporter of the PGM but also be involved in several secondary and tertiary PGM activities by establishing business clusters around mining areas. The objectives of this research study were to assess the nature of the local Special Economic Zones (SEZ) landscape, including a detailed overview of the Bojanala and Fetakgomo-Tubatse SEZs on the western and eastern limbs respectively, and to develop a viability matrix to assess which of the two SEZs, namely Bojanala and Fetakgomo-Tubatse, is likely to succeed based on the socio-economic profile, sector analysis, education level and spatial linkages. The research sought to answer whether the Special Economic Zone model implemented in South Africa is adequate to enable successful SEZ operation in the BC and whether the current spatial linkages in the BC are sufficient to support the existence of a PGM SEZ. The research design is a case study, and the qualitative research methodology was chosen as the most appropriate. The data used involved desktop study from research papers, books, journal articles, conference papers, documents from government agencies, websites, annual reports, news articles, web blogs and published statistics from research organisations. A thematic analysis was used to interpret the literature reviews, case studies, and other secondary data cited in the study. The results indicated that the Fetakgomo-Tubatse SEZ has a high viable potential to succeed as an SEZ because it scored higher in the viability matrix, even though it scored lower on the spatial linkages and sector analysis. The likelihood of success of the Fetakgomo-Tubatse SEZ over the Bojanala SEZ was mainly driven by the value proposition offered and the regional education level assessment where it was found that the Fetakgomo-Tubatse municipality has a bigger population size and a larger iii [OFFICIAL][OFFICIAL] number of people with matric (30% of the population) and post-matric (4% of the population) qualifications. That is, it is likely to provide local labour with the qualifications and skills required in the SEZ. Furthermore, both SEZs have been successful in acquiring funding from companies that want to locate in the zones, so it could be argued that both of them will be in a position to promote business clustering in the area if the right ingredients such as government intervention, presence of small and medium enterprise, and integration of internal and external markets are in place. The study further supports the view that industrial policies have a role to play in changing and addressing market failures to encourage economic growth. However, these development efforts need to be based on the assessment of the implementation landscape of the SEZ to ensure its success. Lastly, it is acknowledged that the robustness of this study could be improved by conducting interviews with SEZ operators in South Africa, the Department of Trade, Industry and Competition SEZ Lead, North West Development Corporation (NWDC) and Limpopo Economic Development Agency (LEDA). The NWDC and LEDA are development agencies tasked with the development of the Bojalana and Fetakgomo- Tubatse SEZs respectively. Insights could also be gained by focusing on group discussions and interviewing community leaders, business forums, and traditional leaders in affected regions.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 Large-Scale Mining and Artisanal and Small-Scale Mining Partnerships for Sustainable Socio-Economic Development in Zimbabwe(University of the Witwatersrand, Johannesburg, 2024) Tsoriyo, Vincent; Mutemeri, NelliaThe study focuses on the partnership between Large-Scale Mining (LSM) and Artisanal and Small-Scale Mining (ASM) as a pathway to address the challenges of informal ASM in mineral-rich communities. It highlights the collaboration between Pickstone-Peerless Mine (PPGM) and ASM operators under the Bluestreak Mining Cooperative (BMC) in the Chegutu district of Zimbabwe, with the goal of formalizing ASM activities to benefit local communities and the broader economy. The research seeks to provide empirical evidence and a practical model for such partnerships, which are lacking in documentation, particularly in the context of Zimbabwe. The partnership model is proposed to increase the socio- economic impact of ASM and allow the government to efficiently harness economic gains from mineral resources. Using qualitative and quantitative methods, the study assesses stakeholder perspectives and the partnership's socio-economic significance, advocating for LSM-ASM partnerships to formalize ASM operations and citing benefits like improved control, coexistence, and mutual advantages. While the PPGM-BMC collaboration has made progress in formalizing ASM and enhancing environmental and social responsibilities, further enhancements are needed for sustained community impact. Recommendations include alternative extraction methods, rehabilitation plans, and long-term sustainability plans, with future research directions exploring economic models for low-free-gold ores and LSM-ASM partnerships' role in transitioning away from mercury use, ultimately promoting sustainable mining practices and improving ASM community livelihoods.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.