School of Mining Engineering (ETDs)
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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.Item Investigation of long-hole stope performance at south deep gold mine(University of the Witwatersrand, Johannesburg, 2024) Ncube, Musawenkosi GreciousSouth Deep Gold Mine is located 45km south west of Johannesburg within the gold-rich Witwatersrand Basin. The reefs at the mine occur within an economically significant stratigraphic bundle containing Ventersdorp Contact Reef (VCR) and Upper Elsburg conglomerate units. Long-hole stopping (LHS) is the primary method of mining and accounts for over 60% of the gold produced at the mine. It is, therefore, critical that the stopes meet the required production output for the designed mine lifespan at efficient stope turnaround times. However, mine data suggests that ore production from LHS has been erratic and has significantly affected the mine’s ability to produce to its installed capacity. The reduction in productivity and utilization is an area requiring research and this project investigated LHS performance at the mine to understand factors that influence stope turnaround time. Three research questions guided the study intending to improve LHS performance: • What is the influence of geological environments on LHS performance; • How do design aspects at South Deep affect LHS performance; and • How do current drilling and blasting practices affect LHS performance? To answer the research questions, the research adopted a stepwise process of categorising mining environments, analysing stope data files on Deswik software, developing predictive models on Python and MS Excel, informing excavation design, and finally reviewing drilling and blasting practices at the mine. These steps helped in leveraging the intersection that exists between geological environments, technical design aspects as well as operating tactics at the mine. iii The findings from the research questions led to the emergence of two themes. The first theme corresponding to the influence of geological environments and design aspects relates to the application of engineering principles in the mining environment, within the jurisdiction of the mining engineer / mine planner. The second theme, corresponding to drilling and blasting practices, relates to operational excellence, within the jurisdiction of the miner. The success of LHS performance hinges on the interplay and balance of these two themes. The major findings of the research indicated that deviation from set standards and malfunctioning components compromised drilling accuracy while wrongly charged holes (over-charged/under-charged) compromised blasting efficiency. They further showed that conventional and de-stress cut environment stopes were the most susceptible to over-break. Severe over-break was found on Secondary and Sequential stopes, predominantly on hanging walls and footwalls. Hanging walls and footwalls with hydraulic radius (HR) values above 6.0 (mine standard) also showed high susceptibility to over-break. In the process of analysing the results, the research developed a multi-variate model to predict the behaviour of the relationship between LHS performance and HR. It also created a matrix that informs how the mine may manage over-break. The research concluded by giving a set of recommendations for improving LHS performance, the chief of which emphasised the importance of strict supervision of drilling and blasting practices underground, measuring drilling against quality and quantity metrics as well as aiming for designing stopes with HR values below 6.0. It further recommended the adoption of the stoping scenario matrix developed, the improvement of the integrity of backfilling as well as the automation of the drilling and charging processes.Item A holistic approach to the design of two tonnes temporary support systems (nets, mechanical props, hooks and roof bolt face plates)(University of the Witwatersrand, Johannesburg, 2024) Modika, MosesIn 2019, Thembelani Mine experienced a high number of injuries caused by Falls of Ground (FOGs) in the face area. To address this issue, safety nets with a capacity of two tonnes were urgently introduced. The two tonnes safety nets were intended to hold FOGs with a maximum mass of 1.78 tonnes, thereby providing a factor of safety of 1.1. However, in 2020 a FOG accident occurred during a drilling shift when a rock with a mass of 1.65 tonnes fell, leading to the death of an employee. The square headboard mechanical props with headboard dimensions of 130 mm x 130 mm, which were supposed to hold the safety net, were pulled out by the FOG, thereby allowing the safety net to collapse with the FOG. The slipping out of the square headboard mechanical props was due to a smaller headboard surface area of 130 mm x 130 mm in contact with hangingwall and a pretensioned load of 0.86 tonnes to 1.43 tonnes which could not sustain a falling rock with a mass of 1.65 tonnes. As a result, the square headboard props were immediately replaced with T-shaped Grease box mechanical props with average pretension load of 2.23 tonnes, larger and longer headboards of 370 mm x 100 mm to increase resistance to slipping out. The T-shaped Grease box mechanical props come with 16 mm flexible G-hooks attached to the headboards. The T-shaped Grease box mechanical props were tested at a drop test facility together with two tonnes Rock- stop safety nets and found to be able to hold two tonnes mass when installed at a standard spacing of 1.5 m x 1.5 m. This indicated that components of the temporary support systems other than the two tonnes Rock-stop safety net were not considered during the roll out. These components include 12 mm diameter flexible G-hooks, roof bolt face plates with a thickness of 4.5 mm, and square headboard mechanical props with welded 12 mm U-hooks and headboard dimensions of 130 mm x 130 mm. Therefore, it was decided to conduct a study to test the temporary support systems holistically using installation scenarios as practiced at Thembelani Mine as opposed to testing each of the constituents of the systems individually. The aim of the tests was to assess if all components fulfil the requirements of the two tonnes temporary support systems from system test point of view. iv While conducting the study, it was found that the safety nets were introduced without considering all aspects of the temporary support systems, such as safety net deflection parameters, hooks, mechanical props, and roof bolt face plates. Moreover, it is necessary to maintain a safe working height within a specific stoping width, which is the vertical distance between the footwall and the safety net in the hangingwall after holding a falling rock. This is to ensure that the employee underneath the net does not get struck by the FOG which deflected with the safety net. The study aimed to identify the items that did not meet the two tonnes systems' requirements and recommend improvements to ensure they function as expected. The study was conducted at available drop test facilities such as NCM and Videx, simulating the installation scenarios as practiced at Thembelani Mine. The study revealed that the two tonnes Rock-stop safety nets, along with 6 mm face plates, 14 mm Carbon steel S-hooks, or 14.5 mm Spring steel G-hooks, fulfilled the requirements for the two tonnes systems. The two tonnes Rock-stop safety nets and T-shaped Grease box mechanical props with flexible 16 mm G- hooks also fulfilled the two tonnes’ requirements. The study determined that the systems that fulfilled the two tonnes’ requirements were effective for all stopes at Thembelani Mine with heights of 1.2 m and 1.4 m and flat excavation ends with a height of 3.2 m, with deflection limits of 0.35 m, 0.55 m and 1.3 m respectively. In 2022, an alternative to the safety nets, the MINAX 80/3 Blast-on Mesh (BOM) with 8 mm blast-on cable, was introduced. The BOM underwent a similar study to the Rock-stop safety net, and the drop tests showed that the deflections obtained with the BOM in various scenarios as installed at Thembelani Mine were all above 0.35 m but less than 0.55 m. Hence, BOM can be used in stopes and flat excavations with heights of 1.4 m and 3.2 m, respectively.Item Investigating the influence of burden response on fragmentation at Sishen Mine(University of the Witwatersrand, Johannesburg, 2024) Moabelo, Matshidiso Tlou; Non, Matsobane; Tholana, TinasheSishen Mine is an iron ore mine based in the Northern Cape, 280 km north- west of Kimberley. The iron ore is extracted through means of drilling and blasting which utilises explosives to fragment the rock. This method of rock breakage requires blastholes to be assigned a delay timing. At Sishen Mine this is done through burden response. The mine has a set of timing guidelines that indicate the burden response range for each geological domain. The main focus of the study was on the waste and ore domains, which are blasted using the same burden response of between 12 ms/m to 18 ms/m. The aim of the study was to investigate the relationship between burden response and fragmentation and whether these timing guidelines for the ore domain result in the mine’s preferred fragmentation size of between 230 mm and 1400 mm where X80 is 600 mm. The study also aimed to investigate the impacts of fragmentation on loading rates and to measure the DMS ROM lump to fine ratio during and after determining the optimal burden response for the ore domain. The investigation was done from March 2022 to December 2023. It was carried out on 18 blocks in the North and South Mine pits. The research found that in the ore domain, fragmentation sizes increase with faster burden response. The fastest burden response used in the study was 14 ms/m and yielded X80 of 354.63 mm. Furthermore, Powergel Eco 35 explosive product resulted in coarser fragmentation in the ore domain compared to Innovex EGA. It was also found that loading rates reduced with increasing fragmentation size. The DMS ROM lump to fine ratio improved during the duration of the investigation. In 2021, the average lump to fine ratio was 77.74% which increased by 1.69% to 79.43% in 2022 and by 3.76% to 81.50% in 2023 indicating that a faster burden response improved lump to fine ratio. Ore blocks should be blasted with a burden response faster than 14 ms/m and waste blocks with a burden response range of 16 iv ms/m to 18 ms/m. However, more studies should be conducted on burden responses faster than 14 ms/m. Powergel Eco 35 should be used to charge ore blocks over Innovex EGA. Sishen Mine should consider including inter- hole delay timing on the timing guidelines.Item Analysis of factors affecting rehabilitation of abandoned mines in South Africa: cases on asbestos projects(University of the Witwatersrand, Johannesburg, 2024) Meyerowitz, Reuben BenjaminAsbestos was once mined in South Africa using traditional methods. Unfortunately, the exploitation of asbestos severely impacted both workers and the surrounding communities. In 2008, the government stopped asbestos mining and designated the abandoned mines as Derelict and Ownerless (D&O) Mines. This was done to mitigate the serious health and safety risks associated with asbestos mining. The aim of the programme was also to address the negative environmental impacts caused by abandoned mines on local areas and social environments. Since 2009, the MINTEK’s D&O programme has rehabilitated 38 mines. However, the rehabilitation of these mines has been affected by various factors that have impacted the Derelict and Ownerless mining projects. This study aims to identify and understand the factors that affect abandoned mine projects in South Africa. The study also aims to provide a comprehensive analysis of the identified impacts and provide recommendations to ensure the successful implementation of the D&O projects. The study used a mixed-method approach to collect both quantitative and qualitative data. The methodology involved data collection from various sources such as recorded reports, financial statements, spreadsheets, engineer reports, project progress reports, construction programs, and document analysis. The study focused on 32 asbestos mining projects in four provinces, namely Northern Cape, Limpopo, KwaZulu Natal, and Mpumalanga, which were used as case studies. The rehabilitation of abandoned asbestos mines is a challenging task that requires collaboration, innovation, and concerted efforts. The factors affecting the implementation of the rehabilitation projects include slow decision-making by the contractors before and during construction, internal challenges faced by the contractors, time delays in material and stock deliveries, community resistance, specific project team experience, influence of external stakeholders and others. These can be categorized into six areas, namely, technical, economic, management, psychological, political and legislative. The study has revealed that all factors identified in the research have a direct impact on rehabilitation projects and contribute to failures in meeting targets in terms of costs and time. In conclusion, the analysis of technical, economic, psychological, and political factors in the rehabilitation of abandoned mines iv in South Africa also highlighted the interconnected nature of these considerations. As such, resolving these factors collectively will enhance the success and sustainability of mine rehabilitation projects. The recommendations from the study include improvements in contract management, ensuring project monitoring and evaluation that encompasses progress monitoring, data management and reporting, and the establishment of performance matrices. The other areas of intervention include policy and legal reforms to define the requirements and objectives of rehabilitation projects. Stakeholder engagement and capacity building are also key elements that have a major influence on the successful implementation of rehabilitation projects. By prioritizing factors and addressing these bottlenecks, the risks associated with asbestos rehabilitation can be mitigated to foster resilient and empowered communities that actively participate and benefit from the restoration processes.Item Impact of the mining charter on socio-economic development and mining investment attractiveness in South Africa(University of the Witwatersrand, Johannesburg, 2024) Meela, Princess Makone; Mutemeri, NelliaThe purpose of this study was to review the impact of the Mining Charter on socio- economic development and mining investment attractiveness in South Africa. The impact on socio-economic development was assessed by reviewing government compliance reports and Minerals Council of South Africa publications. The analysis of exploration budgets as a percentage of country Gross Domestic Product (GDP) was used to gauge the investment attractiveness of South Africa’s mining industry. A qualitative description was also conducted on mining codes and mineral policies of Canada, Australia, Brazil, Chile and five African countries (Ghana, Botswana, Tanzania, DRC, Zambia) to understand how these countries utilise natural resources to advance socio-economic developments. The study concluded that the Mining Charter has a positive impact on socio-economic development in South Africa. The research further revealed that globally, South Africa ranks relatively low in its exploration expenditure in terms of both absolute exploration budget and percentage of exploration budget to GDP. Findings of the international benchmarking study are that the requirements of elements of the Mining Charter are similar to other socio- economic development interventions observed in the assessed mining jurisdictions. The requirement of ownership of mining companies by local people is restricted to South Africa and the DRC. In Canada there is limited sharing-holding/profit-sharing for the benefit of the community where there is an agreement in place between the mining company and such community. These agreements are not imposed by law or mining policy. The research finding regarding the ownership element is significant in that it links to the problem statement of the research study wherein the requirement of ownership of mining companies by citizens (“black people”) is reportedly one of the main hindrances of mining investments in South Africa, as singled out by some of the iii mining executives. The recommendation from the study is that the South African Government should enforce empowerment deals where all shareholders are treated equally in terms of contributions and participation in the managing of a mining company. In line with other mining jurisdictions particularly in Africa, direct state participation could be considered as an option for meaningful economic participation of the South African Government, for the benefit of all South Africans.Item Developing a work management system to create an integrated and optimal short-term planning process at South Deep Mine(University of the Witwatersrand, Johannesburg, 2024) Maleka, ManuelThis research was conducted at South Deep Mine, an underground trackless gold mine located within the Modderfontein Farm in the Westonaria District, Southwest of Johannesburg. The aim of this study was to develop a work management system to create an integrated and optimal short-term planning process at South Deep Mine. The study employed both quantitative and qualitative research methods to achieve its objectives. Most of the data was obtained through an online survey which targeted individuals employed within the mine technical services department. The problem being addressed in this research is the challenge associated with manual data capturing during planning sessions. This research is driven by a desire to improve work efficiency and mine productivity at South Deep Mine through the application of innovative planning and reporting tools. Literature review presented the importance of innovation and effective planning in mining operations, indicating the role of integrated work management systems in modernized underground mining environments. Work Management Systems investigated were Deswik and MineRP software and Syncromine reporting system. The results reflected that Deswik and Syncromine are used throughout the industry with some benefits such as the ability to produce integrated production reports and the reliability in data handling. However, data analysis revealed shortcomings in existing work management systems, particularly in addressing real-time data and promoting automation. The aims of this research were achieved through the development of a systemized planning protocol. The study highlighted the need for an iv integrated approach to address short-term planning challenges. Future studies include the adoption of user-friendly software tailored with site specific requirements and the development of models covering all aspects of the mining value chain.Item Application of Data Analysis and Machine Learning to Develop a Maintenance Strategy for Load-Haul-Dump (LHD) Machines at Booysendal Mine(University of the Witwatersrand, Johannesburg, 2024) Malambule, Thulani Mduduzi; Mabala, Mahlomola Isaac; Nwaila, GlenThis report focuses on applying data analysis and machine learning to develop a maintenance strategy for load-haul-dump (LHD) equipment at Northam Platinum’s Booysendal underground mine. This operation predominantly relies on trackless mobile machinery, with a significant emphasis on LHD machines. The mine maintains daily records of mechanical equipment breakdowns. However, Booysendal's reliance on a reactive “run-to-failure” maintenance system has led to operations outside a predefined maintenance plan. The objective of this research was to apply data analytics to understand trends in the dataset and extract meaningful insights regarding LHD breakdowns. It aimed to develop a predictive maintenance model for LHD machines using appropriate machine learning models. Lastly, to design a data-driven maintenance strategy based on insights from data analysis and machine learning (ML). The hydraulic system and transmission components were found to contribute 80% towards downtime. The K-Nearest Neighbours (KNN) regressor was chosen as the best regression model, achieving the lowest Root Mean Square Error (RMSE) of 2.02, while the Support Vector Machines (SVM) classifier was selected as the best classification model with the highest accuracy of 60%. Recommendations on how the predictive models could be improved were highlighted. Finally, a hybrid maintenance strategy is proposed for proactive optimisation. The strategy entails integrating predictive analytics, real time condition monitoring and threshold-based alerts to enable proactive maintenance actions. The proactive actions include ensuring availability of critical spares and conscientizing LHD operators on failures related to bad operating practises.Item The feasibility of Witwatersrand gold tailing as an alternative in cement manufacturing as a possible contributor to the circular economy(University of the Witwatersrand, Johannesburg, 2024) Maipushi, Mmatseleng Sophy; Mulopo, Jean; Nyembwe, AlainThroughout mining history, there have been growing concerns about tailing storage facilities. Concerns include the vast space tailings occupy, and their mismanagement resulting in environmental impact and health implications. Tailings form the highest percentage of material remaining post extraction of mineral, which subsequently requires a deposition site. Only a small percentage of tailings is used in backfill filling in underground operations. The study investigated the viability of gold tailings as an alternative in cement manufacturing and in doing so contribute to the circular economy. The framework of this study used the Witwatersrand Supergroup gold tailings from the Klerksdorp area in North-West Province, South Africa. The mineralogical, chemical, and physical properties of the Witwatersrand gold tailings were investigated and compared to the Ordinary Portland cement and Hexi gold tailings in Shandong Province, China. The Witwatersrand gold tailings in this study had a noticeably lower calcium oxide content (0.98%) than what is required in cement manufacture (63.68%). The aluminosilicate minerals were reasonably high (above 70%) resulting in a pozzolanic nature, which implies that a certain percentage of the gold tailings can be used as supplementary cementitious material in the production of cement mortar. The study also explored ways of reducing or eliminating the identified hazardous substances such as cyanide and radioactive elements. The concentration of uranium radioactivity in Klerksdorp gold tailings is 931.6 Bq /kg above the regulatory limit of 500 Bq/kg for uranium in cement manufacturing. The uranium radioactivity iii concentration can be reduced by incorporating a process of uranium extraction during gold extraction operations. Additionally, the South African policy on the valorisation of mining waste which only recognizes the retreatment of tailings under the Environmental Authorization under the National Environmental Management Act No. 107 of 1998 should be amended by including the use of mining wastes in other sectors of the economy through the circular economy framework.