Electronic Theses and Dissertations (Masters)

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Optimisation of fragmentation at south deep gold fields mine: a case study
(2020) Nong, Matsobane
A fundamental aspect of an efficient mining operation is the steady movement of material throughout the mine system; particularly the flow of ore from the upstream excavation point to the downstream processing or stockpile site(s). This can be achieved by attaining an optimal fragmentation size from drilling and blasting suitable for subsequent mining process such as loading, hauling and crushing. Drilling and blasting are the first fragmentation process and is currently the most economical technique of fragmenting hard and competent rock especially for deep-level mines where operational costs are high. The aim of this research is to analyse and optimise fragmentation to improve the oreflow efficiency at South Deep Mine in South Africa. The mine experiences coarse fragmentation that cannot pass through 300mm by 300mm grizzlies. As such, secondary blasting is often done to reduce the size of boulders either in the stopes or on top of the grizzly which leads to a reduction in productivity. Although coarse fragmentation is reported in the stopes and on top of grizzlies, the plant is reporting fine fragmentation that is not suitable for the ball mill. This results in reduced gold recoveries. To get a better understanding of the fragmentation size distribution achieved, fifty-one images of the muckpile from five stopes were analysed using the Split-Desktop software. The analysis showed an overall F80 passing of 287.48mm, which is less than the 300mm grizzly size implying that the fragmentation size achieved is adequate. However, looking at the overall particle size, the Rosin-Rammler distribution was found to be 0.80. This infers an inconsistent fragmentation where the mine produces both coarse and fine fragmentation size. The AEGIS Underground drill and blast software was used to analyse the drill and blast design patterns. The analysis showed that the design toe spacing varies from about 0.5m to 7.5m in the same blast. Due to the software’s limitations, the break model analysis was only run for toe spacing between 2m and 7.5m. This showed that there is no overlap between blastholes which may be the source of the coarse fragmentation size. Fine fragment size may be as a result of blastholes which are close together, i.e. 0.5m. Although not tested, the impact of blasting stresses emanating from primary stopes may result in fractures in secondary stopes which will have a greater impact on the propagation of the shock wave and high-pressure gases between the blastholes and consequently the fragmentation distribution size. It is recommended that the mine change their drill and blast pattern. The mine must change from 76mm blasthole diameters and introduce a larger blasthole diameter of 89mm blasthole diameter. Not only will this diameter improve drilling accuracies but will reduce the fragmentation size distribution. It is also recommended that the mine maintains a ring burden of 2m throughout despite an increase in the blasthole diameter. For the first design, the toe spacing must also be 2m followed by increments of 0.5m per blast until a suitable fragmentation distribution size is achieved. After which, the toe spacing must be kept constant. It is important that South Deep Mine continually evaluate the fragmentation size distribution achieved from each blast for optimisation purposes. Therefore, a blast management system is important.
A comparison of various modelling techniques to optimise production rate on a platinum mining project
(2021) Dreyer, Jaco
Every business aims to create an optimal economic value for its shareholders. The production rate is one of the critical drivers of value in the mining business. Several approaches have been developed to determine the production rate for mining operations. This study applied three approaches for determining production rate, namely the tonnage-based, microeconomic and marginal-analysis modelling methods. These methods were applied on a platinum project, and the production rate results from the three methods were used to determine the life of mine (LOM) production profiles, capital expenditure (CAPEX) and operational expenditure (OPEX). These results were then used as inputs into a discounted cash flow (DCF) model. The DCF model results were compared and analysed to determine a production rate determination method that results in an optimum production output rate for the project. The study revealed that the tonnage-based modelling technique resulted in the highest production rate of 410-kilo tonnes per month (ktpm), the highest CAPEX of USD957.24 million, the lowest OPEX of USD75.37 per mined tonne, the highest net present value (NPV) of USD63.12 million and the highest internal rate of return (IRR) of 12.85% over a 40-year LOM. The microeconomic modelling technique ranked second with a production rate of 270 ktpm, CAPEX of USD 726.24 million, OPEX of USD 76.68 per mined tonne, NPV of USD 3.46 million and IRR of 10.17%. The marginal-analysis modelling technique ranked last with a production rate of 230 ktpm, CAPEX of USD 658.76 million, OPEX of USD 77.83 per mined tonne, NPV of USD -10.69 million and the lowest IRR of 9.47%. Mineral Resource tonnage-based modelling may be further investigated in other commodities other than platinum or other multi-element/polymetallic mineral deposits in line with the South African mining industry. This will result in the formulation of industry-specific calibration in the South African mining industry
The underrepresentation of technical women in executive and board of directors’ roles in the ten largest listed mining companies in South Africa
(2022) Zulu, Noluthando
As with many technical industries, mining is dominated by men. It is well established that the industry has struggled with the attraction and retention of female talent. While women have made significant inroads in the industry, technical women (defined here as women who come from a geology, engineering, metallurgical, etc background) are underrepresented in the most senior decision-making roles of major mining companies. The purpose of the study was to explore this phenomenon, examining the executive committee and board composition of the 10 largest mining companies listed on the Johannesburg Stock Exchange and interviewing 30 technical women who have worked for, or currently work for, these organisations. The results demonstrate that technical women seldom advance from operations to the boardroom and, typically, play a support function while men make core mining and technical decisions. The study also finds that many technical women move into nontechnical roles for a number of reasons. Further, while attraction of women to the industry continues to rise, the studied companies are struggling to retain technical female talent. The study further highlights the significance of government intervention concerning the inclusion and advancement of women in mining. It also emphasises the need for continued policy development and concludes with recommendations on how mining companies can drive both the inclusion of women in mining as well as their corporate advancement.
Support Design Approach for Crusher Chambers: A Case Study of Palabora Mining Company
(University of the Witwatersrand, Johannesburg, 2023-01) Masole, Nyeleti Venus; Stacey, T.R.
This report project aimed to design a support system for crusher chambers at Palabora. The research project focused mainly on the two crusher chambers (12m wide by 25m high and 61m long) planned for the Lift 2 project as part of the ore handling system. The main research questions that the researcher sought to answer were; what are the differences between Lift 1 & Lift 2 in rock mass characterisation, classification and the ground control district?; how suitable is the Lift 1 crusher chamber support system for Lift 2?; what could be support requirements for Lift 2 crusher chambers in terms of empirical, analytical and numerical design methods and what are the recommended support design approaches for Lift 2 crusher chambers? The methodology used to design support for the Lift 2 crusher chambers was based on determining the expected failure mode first and then selecting suitable design methods to cater for the extent of failure. This study combined empirical and analytical methods to determine the failure mode and required support system. The results were then validated using Finite Element Method numerical modelling software called RS2 (Phase 2) from RocScience. Research findings revealed that the ground control district, classification and characterisation of rock masses differ slightly between Lift 1 and Lift 2. Jointing in dolerite dykes (DOL) was slightly dense in Lift 2 compared to Lift 1 and was associated with increased mining depth. Furthermore, the Lift 1 crusher chamber support system was found to be suitable for Lift 2 but must incorporate dynamic support. Unwedge (RocScience) analysis simulated wedge type of failure in the crusher chamber walls. The empirical and analytical design approach proposed cable bolt lengths of between 6m and 9 m and 3-4 m for roof bolts with bolt spacing of 1.4 m and 1.0 m respectively. The simulation results using RS2 confirmed that the cable bolt length and spacing were appropriate. The recommended support system was expected to provide sufficient support to the crusher chamber in terms of controlling rock mass deformation and yielding. The general conclusion was that the design approach selected for crusher chambers must be able to adequately represent rock mass behaviour and the support required to maintain long-term stability.
Verifying the Quality and Performance of Grout Using Sensor Technology
(University of the Witwatersrand, Johannesburg, 2023-10) Hadebe, Menzi Bright; Mitra, Rudrajit
Underground mines systematically install ground support to stabilize excavations and provide safe working environments. Support units, such as rock bolts and cables, are commonly filled with cementitious grout to effectively prevent corrosion, maintain bonding behaviour between the support unit and grout, and enhance the load transfer between the grout and surrounding rock mass. The grouting process is however time consuming and labour-intensive, which leads to haphazard installations. These substandard grout installations are only observed after rock fall instabilities occur when the quality and extent of grouting inside a support hole are exposed and can be observed. The need to monitor grout installations increased (provide assurance) but remained a challenge due to the invisibility of grout inside the support hole. The invisibility of the grout column inside the support hole renders the routine quality control inspections of installed support units ineffective. This ineffectiveness of quality control inspections has led to a growing need to monitor grout installations with smart technologies to provide quality assurance of full-column grouting. In its current state, grout technology in the mining industry can only measure the extent of grout inside a support hole directly after installation (limited battery life). It cannot measure the loss of grouting material into near borehole fractures, shrinkage, quality of grout inside the support hole or its impact on support performance. These factors are critical to the success of an effective support system and pose a significant safety risk when overlooked. This research report will describe how grout sensor technology data was recorded and used to verify the extent and quality of cementitious grout inside support hole installations at laboratory and deep-level mine study sites. Grout sensor technology, in practice, utilizes several grout sensors placed at predetermined positions along a support unit with a receiver attached to the collar of the support hole. Electrical resistivity data from each sensor is collected using a grout detector. Depending on the position of each grout sensor, the extent of grout inside a support hole can be confirmed, hence eliminating the need for speculative and ineffective visual observations. The non-destructive verification and prediction of the quality and performance of grout inside support holes using sensor technology forms an invaluable strata control tool that can be used to identify sub-standard grouting operations and significantly improve safety at underground mines. This novel and innovative technology is a mining industry first.
The Impact of Digital Technology in South African Coal Mining: A Financial Performance Analysis of Anglo Coal American, Bhp Billiton and Glencore
(University of the Witwatersrand, Johannesburg, 2023-10-27) Maluleke, Reply; Neingo, Paskalia; Marshall, Tania R.
Digital technology, typically, refers to electronic tools, resources, devices and systems that store, generate and process information rapidly. Digital technology and innovation are among the initiatives that can assist mining companies to realise productive, efficient, profitable and sustainable mines. As such, the mining industry is taking steps towards digital technology and innovations that have evolved in recent years. The objective of this report was to discuss the financial impact of digital technology of the selected South African thermal coal mining companies namely Anglo American Coal Division now operating as Thungela Resources, Glencore, and South32, previously spun out of BHP Billiton and now operating as Seriti Resources. Coal mines were selected for analysis, due to their importance with respect to energy generation in South Africa. Industry cost curves over the period 2013-2019 were constructed as part of the financial analyses to show the trend of the selected companies’ unit costs. The research also used other financial analysis methods such as operating profit, profitability ratios, Economic Value Add and Du Pont analysis to analyse the performance of these companies. There appeared to be no production and unit cost improvement directly linked with investment in digital technology, as breakdowns, commodity prices, depletion of reserves, selling of operations, mine closures, high contracting prices, inflations and other factors also affected these parameters. Results for Anglo Coal and South32 did not indicate consistent good or improved financial results in all the financial analysis methods post the investment years in digital technology, in contrast to Glencore’s results which did. Glencore also invested more capital in digital technology as compared to Anglo Coal and South32. It is suggested that this may be one reason for its success. Consequently, it is recommended that companies looking to invest in digital technology follow the example of Glencore and invest as much capital as possible in this venture in order to maximise its potential.
Pit Optimisation of Vondeling Quarry by Understanding Geotechnical Parameters Determined at Zoutkloof Quarry
(University of the Witwatersrand, Johannesburg, 2023-11) Mukwevho, Tshinanne Matty; Pillay, Ohveshlan
The purpose of the study was to investigate the geotechnical parameters at Zoutkloof quarry and how they affect stability and the mine planning process. The geological features of Zoutkloof and Vondeling are similar, hence the lessons learned while mining Zoutkloof quarry can be used when mining Vondeling quarry. Zoutkloof quarry has already reached its limits and is no longer operational. It is important that mine planning considers the critical geotechnical parameters. The main reason for this consideration is to keep slope walls stable, employees and equipment safe, and to continue mining the ore in an economical manner. The methodology of the research incorporated highlighting the literature in the public domain on geotechnical considerations in open pit mining. Evaluating geotechnical parameters such as groundwater, rock mass strength, slope angle and monitoring; and additionally, showed scheduling of mining blocks from 2007 to 2008 formed part of methodology in the research. The results analysis indicated that the strategies implemented to control groundwater were successful to keep the production benches dry and walls stable. Good understanding of the discontinuities and the rock mass strength enabled the quarry to be divided into ground control districts. Kinematics analysis for possible failures was done and the results showed that there was no probability of failure on planar mode. However, there were minor possibility that failure can occur on wedge and toppling mode. Yearly mining scheduling was completed, focusing on tonnage and quality requirements. During this period, Zoutkloof had minimum waste mined and the quarry had narrowed significantly which required the operational team to work within mine design specifications to maintain safety and slope angles. Some resources had to be compromised as it was not practical to exploit them safely. The research concluded its findings as successful because Zoutkloof quarry was mined completely with approximately 10 slope failures that resulted with no injuries to employees or damage to equipment. The factors of safety (FOS) were evaluated to be well above one and slopes remained stable until mining ceased. The research also made recommendations that can be implemented while the Pretoria Portland Cement (PPC) continue to mine Vondeling quarry to aid same success as Zoutkloof while being cost effective.
Slope Failure Prediction at Husab Open Pit Mine in Namibia
(University of the Witwatersrand, Johannesburg, 2023-12) Thikusho, Christine Runguro; Watson, Bryan P.
The study is focused on Domain D at Husab Mine in Namibia. The purpose of the study was to improve prediction of pending slope failures for planar and wedge configurations. Planar and wedge failures are similar in that little strain is required to initiate failure. Slope monitoring systems such as ground based radars, interferometric synthetic aperture radar and prisms were reviewed from the available literature. The data from the mine’s satellite monitoring data and the ground-based radar instruments was analysed. Slope prediction methods were used to back-analyse the failures, to determine if failure prediction times were possible. A case study was incorporated from the neighbouring Rössing Uranium mine, to supplement the data. The data utilised for the study was downloaded from the slope monitoring instruments on the mine i.e., the interferometric synthetic aperture radar, ground-based radar and tension crack data. The following slope failure predictive tools were investigated; the strain deformation approach; the inverse velocity method; the slope gradient method; the acceleration and velocity approach; and Displacement/Time plots. The back-analysis work done proves that the following slope failure predictive methods were able to predict failure at least 3 days before failure: velocity, cumulative displacement and inverse velocity. It appears that the Husab mine failure mechanism is not as brittle as previously assumed and failures are not necessarily instantaneous. Therefore, failures should be identified early, and the necessary risk mitigation measures implemented proactively. The ability of back analysing large volumes of stored data is important in the study of failure prediction.
Geometallurgical influence of clays on the Jwaneng kimberlite value chain
(2024) Nkgakile, Naomi
Geometallurgy is a cross- disciplinary function that provides a better understanding of the ore characteristics impacting the treatability of the material. Optimal treatment of the material is enabled by understanding variability in the ore body. Having this understanding leads to flexibility when planning mining mixes. The present investigation of the Jwaneng DK2 deposit’s geometallurgical responses demonstrate that various rock lithologies impact the treatability of the Jwaneng kimberlites. The plan t is therefore hindered from achieving design capacity as a result of its treatability constraints. The volcaniclastic kimberlite, which is a majority- treated lithology at Jwaneng Mine, contains the highest volumes of smectite clays. These clays cause settling challenges resulting in higher consumption of processing materials. To allow for informed strategic planning, all vital treatability information on the clayrich kimberlites needs to be collected. The clay occurrence can then be incorporated into the creation of the geometallurgy model. Then the completed geometallurgical model can be utilised as a predictive tool for planning
Improving open pit mine economics through ultimate pit slope optimization: case study of Pickstone-Peerless mine
(2024) Nyamande, Pardon
In most open pit mining operations the need to create stable pit slopes and the influence of the overall pit slope on the economics of such an operation is highly appreciated. Despite such knowledge many open pit mines are designed with little or no geotechnical investigations being carried out so as to come up with an optimized pit slope in line with site specific conditions. This can lead to under or over estimating pit slope angles. Conservative (too gentle) slopes result in high stripping ratios therefore a high operating cost. Slopes too steep may result in slope failures, which may lead to high operating costs or premature mine closure. This project emphasises the importance of geotechnical investigations not only for safety reasons but for economic reasons as well. A case study of Pickstone Peerless mine was used. Geotechnical data was gathered through core logging and face mapping of the existing pit. The data gathered was then used for stability analysis employing empirical, kinematics, limit equilibrium and numerical modelling. Rocscience software packages were used for numerical based analysis. From the results obtained it was concluded that it is possible to steepen the current 52o overall pit slope angle of the Peerless pit by 1o without compromising stability at both bench and regional scales. This will be possible provided adequate slope management practices are put in place and adhered to. The steeper slope would have saved the mine more than 2,681,110 m3 of waste stripping, translating to in excess of $12,064,995.00 (USD) in financial savings for the existing pit. The steeper angle applicable to the current pit may not be appropriate to the pit extensions. Further geotechnical evaluations should be done on suitably positioned and spaced boreholes in the area of the extension, to verify the stability of steeper slopes in that area. The analysis done as part of this project was used to show that the current pit can be deepened by 5 m without a push back.
The incorporation of unmanned aerial vehicles in a slope stability monitoring system: a Rössing uranium mine case study
(2024) Shanyengana, Olga Ndapewoshali
Slope stability monitoring is a safety critical input in the Slope and Dump Management Plan (SDMP) at Rössing Uranium Limited (RUL) mine. The SDMP was adopted to satisfy the requirements of the D3 standard – management of slope geotechnical hazard at the operation. Through this standard, RUL aims to provide an injury-free and safe working environment for the operation. This is achieved by proactive identification and management of slope risks and instabilities onsite. This research is a case study of the incorporation of unmanned aerial vehicle (UAV) technology into the slope stability monitoring system (SSM) at RUL, towards conformance to the D3 standard. The study highlights the safety benefits gained by removing personnel from hazardous areas and substituting them with UAVs. The utilisation of UAV data in geotechnical processes such as; the final wall assessment, crack detection and monitoring, as well as dump advancement rate calculations are also discussed. The study further investigated the use of UAVs for SSM prism inspections and proposes the incorporation of UAVs into the trigger action response plan (TARP). A concept of UAV modification for prism-cleaning operations has been developed through this research, to alleviate the challenges of prism loss in inaccessible areas due to dust accumulation on the prism surfaces.
Utilising interferometric synthetic aperture radar and ground-based radar data to predict time to failure and to calibrate numerical models on an opencast coal mine
(2024) Strydom, Jacques
Accurate time failure predictions and improved geotechnical certainty in an opencast mine will lead to tremendous safety and economic benefits. This study utilises interferometric synthetic aperture radar and ground-based radar data to conduct a back analysis on slope failures that have occurred in an opencast coal mine in South Africa. Time to failure predictions was done utilising the inverse velocity technique, while the effect of different data smoothing techniques on the accuracy of the failure predictions was evaluated. Additionally, ground-based radar data was used to calibrate a finite element numerical model to improve geotechnical certainty. Time to failure predictions based on satellite monitoring data was less accurate than predicted in the literature, but satisfactory results were obtained from ground-based radar data. This study confirms that displacement measurement from ground-based radars may be used to optimise the strength parameters of finite element numerical models. To improve the accuracy of time to failure predictions from satellite monitoring data, it was proposed that a satellite constellation with a shorter data acquisition time must be utilised. By having access to more frequent data acquisitions and by identifying the most active points within the failure zone of a slope, it is expected that the accuracy of the time to failure predictions can be improved.
A critical investigation into the creation of special economic zones in South African mining areas
(University of the Witwatersrand, Johannesburg, 2024) Phambane, Maureen; Leeuw, Paseka
The 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.
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 MaryAgnes
This 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.
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.
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, Quintin
New 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.
Quantification of the benefits of pumpable emulsion explosives in narrow reef gold mines
(University of the Witwatersrand, Johannesburg, 2024) Chosi, Ramphele Lordwick
Pumpable 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.
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, Erhan
Surface 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.
An assessment of the Angolan mineral taxation regime: considerations for possible improvements on government´s revenue
(University of the Witwatersrand, Johannesburg, 2024) Africano, N´djamila Hilifavale Borges; Mtegha, Hudson
Angola is host to 36 of the 51 critical minerals in the world and ranks third in mineral exports, totalling over USD 1 billion in 2020, and third in diamond production; Botswana and South Africa hold the top two slots, respectively. These untapped opportunities make the Angolan mining industry an excellent place to invest despite the mining industry contributing less than 1% to GDP and has yet to become a driver of economic diversification. In June 2022, Angola joined the EITI, bringing a welcome improvement in the transparency of the sector´s governance and reform, intended to attract new investors. The study evaluates the effectiveness of the Angolan mineral fiscal system as a tool for maximising revenue for the benefit of its citizens and securing investment (local and foreign) to promote linkages and broad-based national growth and development. Four objectives were examined in this study: (i) Conduct a situational analysis of the current fiscal regime through a comparative analysis of headline rates in regional and international countries; (ii) Qualitative evaluation of the effectiveness and efficiency of the mineral fiscal regime; (iii) Analyse the tax revenues raised by the mining industry between 2011-2021; (iv) Make possible recommendations to improve the current mining tax regime. The study employed a descriptive survey design with a qualitative and quantitative approach for data collection and analysis. The main findings include: (i); Angola's political economy setting resembles that of a hegemonic government characterised by an institutionalised one-party regime whereby the implications on the mineral fiscal regime are multifaceted, affecting investment, regulation, revenue sharing, and sustainability; (ii) Both mineral royalty and corporate income tax rates, are within regional and international norms and have consistently contributed a significant share of the government's direct tax revenues over the last eleven years; (iii) Prevailing fiscal regime can be improved through a combination of tax instruments such as resource rent-tax or profit-based royalty with a basic ad valorem tax system; (iv) However, Angola’s primary challenges point to a possible absence of enforcement and compliance mechanisms for both the mining code iii and the sector fiscal framework, as well as the need to strengthen government agency capacity to oversee and gather fiscal contributions from the sector. In light of these findings, it is recommended to (i) Improve the sector's mining code and fiscal legislative framework and enforce it; (ii) Conduct a study to analyse the effects of all government taxes (direct tax, indirect tax and non-tax instruments and tax incentives) on both the industry and the government´s treasury; and (iii) Conduct further studies on the proposed optimal mineral fiscal regime. Finally, an effective, efficient, and transparent mineral fiscal system can only exist first and foremost through intentional collaboration and alignment of objectives among the sector’s stakeholders.
Assessing the Challlenges in the Valuation of Early-Stage Secondary Diamond Deposits
(University of the Witwatersrand, Johannesburg, 2024) Ganda, Nair da Conceição de Oliveira Gavião; Marshall, Tania R.
Diamond mining is a fundamentally important part of the economy in many countries. Globally, some of these countries are home to early-stage alluvial diamond projects that attract significant interest from investors. Often, these investors need to understand the project’s value to make informed decisions. However, valuing early-stage alluvial projects is a complex and challenging process. This research report identifies and assesses the challenges associated with the valuation of early-stage alluvial projects through a case study of a project in Angola. For the case study, a valuation exercise was conducted using both the Cost Approach and the Market Approach. The research identified challenges specific to the Cost Approach, such as data availability and compliance with internationally recognised Resources and Reserves reporting codes. Likewise, challenges specific to the Market Approach included estimating current commodity prices and checking the performance of alluvial diamond properties on an applicable stock exchange. Additionally, it became clear that complications related to both approaches, such as experience and resource estimation methodologies, need to be addressed before a final valuation range can be determined. Although there are several difficulties, the valuation of early-stage alluvial projects is still possible. Nonetheless, these challenges impact the accuracy, consistency, and interpretation of the valuation results. Therefore, becoming familiar with these challenges and the recommendations made in the report will help valuators avoid potential pitfalls and contribute significantly to the field by guiding more informed decision-making in the valuation of early-stage alluvial diamond projects.