School of Mining Engineering (ETDs)
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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.Item The relationship between human factors and technology adoption at Sishen Mine(University of the Witwatersrand, Johannesburg, 2024) Seabela, Mogaleadi; Twala, PontshoMining of raw materials and minerals started centuries ago in South Africa. Mining methods, then, were very primitive and labour-intensive with the use of slaves in some instances. With industrial revolution came the development of other industries and supply chain process between industries which gave rise to human civilization and improvement of people’s livelihoods. The mining industry progressed as an adopter of technology with operations moving from mechanisation to digitisation. People however remained an integral part of the industry and in the case of South Africa, that is going to be the case for the foreseeable future. South Africa has a high unemployment rate and the mining industry employs approximately half a million people and Sishen Mine employs about 10 000 people. Given the role of mining in the country, it is important that adoption of technology and digital revolution take into consideration human factors in order to be successful. Some of the challenges the mining industry is faced with that requires the adoption of technology, include safety of employees, depleting orebodies and declining commodity qualities, rising input costs, supply chain constraints and macro-economic factors such as competitive commodity markets. To address some of these challenges, the mining industry is adopting technology and there has been significant benefits realised in the safety of mines. Sishen Mine strives towards zero harm and achievement of hundred percent overall equipment efficiency in order to remain sustainable. With technology, there has been some progress in reducing fatalities but there are still significant safety incidents taking place even in areas where technology was implemented to prevent such incidents. The aim of this research was to investigate the impact of human factors on the adoption of technology at Sishen Mine. The objectives of the research were to identify benefits and challenges to adoption of technology and investigate factors that support and/or hinder technology adoption. Another objective was to establish the gaps in the implementation of technology in consideration of the impact human factors have on adoption of technology. Literature studies on mining technology, human factors and how they affect adoption of technology was conducted and found that human factors play a crucial role in the success of technology adoption. Several technologies employed at Sishen Mine were studied and their OEMs interviewed to share the benefits of these technologies and how they performed at Sishen Mine. Mine employees were also interviewed to share their personal experiences of technology in their work. It was found that human factors do have an impact on technology adoption. Key findings were that the benefits of technology were fairly understood and some of the challenges to adoption of technology at Sishen Mine related to human factors. The results showed that there were gaps in the capability of the technologies under study and the benefits realised in Sishen Mine. Some of the gaps included lack of understanding of how the technology worked and inadequate buy-in from end-users due to fear of job losses and inadequate engagement of all stakeholders. It is recommended that human factors are considered during technology implementation for successful technology adoption. This must be supported by adopting the design thinking approach to problem-solving wherein all stakeholders will be engaged on the technology solution before it is implemented. This will drive buy-in and address the human factors that may hinder the adoption of technology. Another recommendation is that a thorough management of change process be employed to cover technology implementation and adoption from the start of the process to the support provided by OEMs post installation, in order to ensure full adoption and integration into the operating model.Item Impact of secondary rock-breaking equipment availability on mining plan in block cave mining(University of the Witwatersrand, Johannesburg, 2024) Pedro, MartinaIn 2018, the Angolan economy was ranked the third largest in sub-Saharan Africa, behind Nigeria and South Africa. This performance is mainly driven by oil production, which represents 50% of the country’s Gross Domestic Product, 95% of its exports, and more than 70% of government revenue, while diamonds represent only 5% of Angola’s exports. The Angolan Government has already invested US$ 260 million into the National Geology Plan (PLANAGEO), which concluded the geophysical aerial survey of the country’s mineral and geological potential in October 2023, putting the country in a better position for future investment. According to the African Diamond Council, it was reported in the Kimberley Process Certification System Statistics in 2021 that the diamond industry in Angola represented almost 1.2 billion Euros, with the contribution to the Gross Domestic Products at 1.6%, making Angolan diamonds the second most important export commodity. The socio-economic impact of the diamond sector has improved from 2016 to 2022, of which a value of US$ 29.58 million was contributed to the areas of education, health, sport, environment, culture, et cetera in local and surrounding communities through the Brilhante Foundation. The diamond mining industry in Angola was regulated by the Diamond Law enacted in 1994. Presently, Angola’s mining industry is subject to state regulation stipulated in the Angolan constitution—Law No. 31/11 of September 2011 (the Mining Code)—and various additional statutory and regulatory acts. In the past five years, under the newly appointed government of 2017, the 2018 Mining Code was amended. This report aimed to investigate whether Angola had fully developed its diamond mining sector to maximise revenue from the industry while also iv attracting more investors and generating socio-economic benefits for everyone, including its citizens. The methodology used in this research was a qualitative research approach. This involved the collection of primary data by interviewing experts in the diamond mining industry, and secondary data that relied on desktop studies of published and unpublished data from books, journals, abstracts, statistical data, and reports from the government gazette. The research findings unequivocally affirmed a positive response to this inquiry. The construction of the Saurimo Diamond Pole in the Lunda Sul Province—featuring seven fully operational polishing factories including Kothari, Stardiam, Kapu Gems, and the KGK factory—has generated employment opportunities and had a positive socio-economic impact within the region. The CEFOLAD Diamond training centre is currently equipping Angolan citizens with the necessary skills and tools to make meaningful contributions to the growth and sustainability of future generations. Angola is the sixth-largest diamond producer globally and is known for its high-quality gemstones. The annual production of rough diamond exports in Angola was 9.396 million carats, with an average of US$ 163 per carat and a gross revenue of US$ 1.56 billion in 2023. The Angola diamond industry employed 200 000 individuals in 2020. The Luele mine was inaugurated on November 10, 2023, in Lunda Sul Province, Angola, and it is expected to contribute an additional 5–7 million carats to the annual diamond sector. The mine currently employs 1 300 Angolan nationals. Based on the findings of this report, it is recommended that more geological investigation needs to be done in areas with visible geological potential in order to enhance and find new deposits which will eventually increase diamond production.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.