Faculty of Engineering and the Built Environment (ETDs)

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Back analysis of previously stooped Panels to improve the safety and productivity of future stooping operations at new Denmark colliery
(University of the Witwatersrand, Johannesburg, 2024) Gonsalves, Ricardo
New Denmark Colliery (NDC) is a Seriti-owned underground coal mine in the Mpumalanga Province. It started stooping operations towards the end of 2018 and has since stooped 50 panels safely across all three of its shafts. NDC selected the NEVID method, which is known for its safety and success in neighbouring mines. Initially stooping panels in the 1100 block, NDC encountered challenges due to narrow panel spans, leading to limited goafing and heightened abutment stresses on surrounding pillars and infrastructure. This necessitated additional support for strategic pillars to ensure long-term stability. To address these challenges, comprehensive research was conducted, which included back-analysis of stooped panels and numerical modelling. Findings revealed that goafing was influenced more by horizontal stress concentrators, such as geological structures than panel spans. Goafing at NDC has primarily been defined by low-angle shear failures, which only extend a couple of metres into the immediate sandstone roof. This is known as partial goafing, which typically results in high abutment stresses. Since complete goafing is unlikely due to the depth below surface and the competent roof material, the high abutment stresses needed to be managed by increasing the width of the barrier pillars between panels and leaving a sufficient number of stopper pillars at the end of a stooped panel. Numerical modelling was used to validate NDC's current design strategy of stooping panels and to determine the width of new barrier pillars. The derived strategy includes an increase in barrier pillar width and stand-off distances, to ensure the long-term stability of main developments. iv The current stooping strategy which was informed by comprehensive research and modelling, has proven effective in both safety and stability.
Investigating the flow of information in a surface iron ore mining operation
(University of the Witwatersrand, Johannesburg, 2024) Loeto Levious, Sekwati
As one of the most advanced iron ore mining operations Sishen Mine has many processes and systems. As an Anglo-American flagship operation, Sishen Mine has implemented many new systems and processes to improve its effectiveness and efficiency. This increased the number of resources (equipment, infrastructure and people). Over the last 10 years, Sishen Mine has doubled the number of employees and resources. The increase in resources, especially employees, processes and systems, has made it difficult for information to flow across the mine. The research aimed to determine the factors that contribute to the issue of gaps in the flow of information. A literature review was done on the current structure of information flow at Sishen Mine and some key discoveries were made. It was found that in a mining operation, there are three main core departments: engineering, mining operation and technical service. These departments depend on each other as the mine value chain is interlinked. The importance of information flow “enabling organisation structure”, communication structure and systems that will be able to enable efficient communication was emphasised. Ten participants across the mine were interviewed to get more details on the research question. The participants had many different views on the research question and as a result, a variety of ideas were discussed. Some of the ideas were linked to what was already discovered during the literature review. Unintegration of KPIs, technical and communication systems, and processes were among the highest contributors to miscommunication between individuals, sections and departments. The mine communication structure was also found not to be centralised and as a result, information flows are divergent. The lack of an integrative culture between individuals resulted in certain professionals having a silo mentality and thus being reluctant to share information. It is envisaged that the Centralised and Integrative System (CAIS) will be able to close the existing gaps in the information flow by focusing on centralising and integrating all critical systems and processes within Sishen Mine.
Navigating the Underground: Assessing Vision-Based SLAM Methods in Simulated Subterranean Scenarios
(University of the Witwatersrand, Johannesburg, 2024) Steenkamp, Dani¨el Johannes; Celik, Turgay
This dissertation explores the viability of vision-based localization methods in subterranean environments, employing a variety of feature extraction techniques including traditional methods and advanced deep learning approaches. A unique dataset was generated using an autonomous exploration UAV within a simulated subterranean environment. This dataset served as the testing ground for evaluating various feature extraction methods. The ORB-SLAM3 was modified to integrate these methods, adapting its feature extraction module to accommodate alternative approaches while retaining its core pose optimization and backend components. The study includes detailed experiments and analyses of different sensor configurations and feature extraction methods, providing insights into their applicability and performance in subterranean settings.
Analysing Test-Driven Development Adherence in Open-Source Projects Using Test-to-Code Traceability Links
(University of the Witwatersrand, Johannesburg, 2024) Kirui, Gerald Kipruto; Levitt, Stephen
Several studies have been conducted to determine the impact of Test-Driven Develop- ment (TDD) on software quality. Many studies utilise test-to-code traceability tools and strategies to detect TDD adherence as part of their methodology. However, most test-to-code traceability tools rely on filename-based matching algorithms, which suffer from low recall; therefore, most TDD detection methods are not accurate. This study aims to assess the effectiveness of a statement-based matching algorithm over a filename-based one and whether it can be used to detect the TDD adherence of a software project. The filename-based and statement-based matching algorithms are implemented in Python. To evaluate these algorithms, 500 tests from sixteen Java projects (encompassing frameworks, libraries, and tools for data processing, testing, and web services) are used. These projects range in size from 5,115 lines of code (LoC) to 378,167 LoC. This evaluation helps in understanding the performance of the algorithms through their weighted F1-scores. A mathematical function is created from first principles to correlate method coverage and time deltas with the test-with-development (TWD) adherence of a project. Thereafter, 100 Java projects are used to demonstrate the utility of this function. The results show that the statement-based matching algorithm, with a weighted F1-score of 0.771 and a 95% confidence interval of [0.741, 0.786], is more accurate than the filename-based matching algorithm, with a weighted F1-score of 0.218 and a 95% confidence interval of [0.193, 0.246]. Additionally, the results show that the relative TWD adherence of eleven projects is found to be highly correlated with TDD scores from surveys (rs = 0.723 and p-value = 0.012), and the method coverage of eighteen projects is found to be highly correlated with code coverage obtained from Codecov (rs = 0.744 and p-value = 0.0003). The literature review reveals that no studies have explored the correlation between TDD adherence and the development step size in software projects. An investigation is conducted using a statement-based test-to-code traceability tool and relative TWD adherence values to determine if TDD projects have smaller development steps compared to non-TDD projects. The study finds no significant correlation between median production method churn and relative TWD adherence of projects in all but one out of eight cases.
Physical layer of Security with NOMA in mixed RF/FSO systems
(University of the Witwatersrand, Johannesburg, 2024) Osman, Amani Alged Fetaha; Takawira, Fambirai; Moualeu, Jules
The ever-increasing demand for spectrum resources, driven by the surge in high data tra c poses a signi cant challenge to the e ciency of wireless communication systems. In response, non-orthogonal multiple access (NOMA) has been proposed as a pivotal technique designed to address the spectral challenges inherent to tra- ditional multiple access schemes. NOMA, through its ability to allow multiple users to share the same time-frequency resources non-orthogonally, represents a promising avenue for improving spectral e ciency (SE). To further improve connectivity and enhance e ciency, NOMA can seamlessly be integrated with multiple-input-multiple-output (MIMO) systems. MIMO, a cor- nerstone technology in modern wireless communication, utilizes multiple antennas at both the transmitter and receiver to exploit spatial diversity, thereby achieving substantial gains in terms of capacity and reliability. The integration of MIMO with NOMA not only addresses the escalating demand for connectivity but also unlocks the potential for massive connectivity and enhanced spectral e ciency in wireless networks. However, the distribution of radio resources within the MIMO- NOMA framework brings forth security challenges owing to the intrinsic charac- teristics of wireless transmissions. In this regards, this thesis tackles the security aspect of MIMO-NOMA systems from an information theoretic viewpoint. The information theoretic security or physical layer security (PLS) e ectively mitigates vulnerabilities stemming from eavesdropping and interception, thereby fortifying the overall security of wireless communication in the present case of MIMO-NOMA systems. Another challenge that requires some attention is ensuring reliability over long distances. Although the radio frequency (RF) spectrum band is recognized for its reliability in diverse weather conditions, its inherent nature renders it sus- ceptible to security concerns. To address the imperative for secure long-distance communications, it is essential to explore innovative solutions that harness the inherent reliability of the RF spectrum while concurrently mitigating its vulner- abilities through enhanced security measures. Integrating technologies such as free-space optical (FSO) communication, acknowledged for its secure transmission capabilities, along with the implementation of advanced security protocols stands as a promising solution to achieving reliability and security in long-distance com- munications. In this work, PLS of a MIMO-NOMA based system in a mixed RF-FSO com- munications is investigated. Additionally, this thesis delves into the injection of vi arti cial noise (AN) in an e ort to explore other features of the proposed sys- tem from a PLS perspective. The last part of the work investigates the secrecy performance of the proposed system in the presence of multiple colluding and non- colluding eavesdroppers. To this end, the statistical properties are examined by deriving the statistical characteristics of the underlying system model, which will subsequently be used to establish both the analytical and asymptotic frameworks for evaluating secrecy performance measures. Finally, Monte Carlo simulations are adopted to validate the accuracy of our proposed mathematical derivations.
Prospects of gibbsite-rich laterite as a source of aluminosilicates in geopolymerisation
(University of the Witwatersrand, Johannesburg, 2024) Gilayeneh, Victor Saye; Nwaubani, Sunday; Otieno, Mike
Laterite, an iron-rich soil widely found in the tropical and subtropical regions of the world, has shown promise for the development of eco-friendly construction materials through geopolymerisation. However, this material varies greatly in composition based on location, prevailing climate conditions, and even in depth within a given lateritic profile. The top layer of most lateritic profiles is usually low in kaolinite but rich in aluminium or iron hydroxide minerals. Despite these variations, research on the use of laterite in geopolymerisation has predominantly focused on materials rich in kaolinite. Therefore, this study explores the potential of aluminium-rich laterite as a source of aluminosilicates in geopolymerisation. In this study, the reaction kinetics, setting times, flow behaviour, strength development, phase composition, and pore structure of geopolymer derived from aluminous laterite were examined. This study also considered both calcined and uncalcined laterite as well as the influence of calcium minerals, namely calcium carbonate (CaCO3) and Portland cement, which replaced 40% of the laterite. In addition, the influence of the laterite’s properties on the performance of the derived geopolymer was also examined. The flow behaviour of the paste was found to be influenced by the viscosity of the activating solution, while the setting times and heat of reaction varied according to the type of laterite and the presence of calcium carbonate or Portland cement, which reduced the setting times and accelerated the rate of heat liberation within the first hour of the isothermal calorimetry test. The geopolymer mix based on calcined laterite displayed the highest amount of heat liberated, while its uncalcined laterite counterpart showed the lowest. All mixes within the calcined laterite series exhibited higher compressive strength than those in the uncalcined series, but only the calcined laterite mixes containing calcium minerals achieved structural strength. The uncalcined laterite mixes experienced strength regressions, with samples of the uncalcined laterite mix containing calcium carbonate developing cracks and subsequently disintegrating. The phase assemblage, porosity and pore structure were also influenced by the type of laterite and the presence of calcium carbonate or Portland cement. However, the presence of calcium carbonate also led to severe efflorescence and subflorescence, which negatively impacted the porosity and structural integrity. Also, the dissolution of gibbsite initiated the development of unstable phases in the uncalcined laterite mixes within the geopolymer and hybrid categories. Conversely, in the absence of activators, especially sodium hydroxide, as demonstrated in the binary mix containing uncalcined laterite, the dissolution of gibbsite is inhibited, resulting in the formation of stable phases.
The removal of diclofenac, cypermethrin, ibuprofen and naproxen from wastewater using advanced membrane technology
(University of the Witwatersrand, Johannesburg, 2024) Ngwamba, Pamela Nadia; Biyela, Precious
In recent years, emerging contaminants (ECs) such as pharmaceuticals, personal care products, endocrine-disrupting compounds, industrial additives, pesticides, nanomaterials, surfactant retardants, surfactants, and their metabolites and transformation products have been widely detected in both wastewater and water bodies. These compounds originate from a diverse range of point and non-point sources, consistently introducing them into wastewater and directly and/or indirectly introducing them to water bodies and the broader environment. The ECs have garnered attention due to their potential environmental impact and potential to induce adverse health effects. Conventional wastewater treatment processes are often not adequate to efficiently remove these compounds, thus leading to residual concentrations entering aquatic ecosystems and eventually, reaching drinking water systems. Although extensive research has been done over the past decade, there is limited literature covering the effects of long-term exposure to ECs, especially their metabolites and by-products, their fate, and toxicity levels. Consequently, additional research is imperative to establish limits and facilitate the regulation of these ECs. Advanced treatment methods, including ozonation, activated carbon filters, and membranes, have proven effective in eliminating ECs from wastewater. It must be noted that the efficiency of these advanced processes varies significantly. Despite extensive testing of various technologies, limitations still exist. Although most of the advanced treatments are highly effective, none of them have the ability to remove a mixture of ECs effectively. This variation is attributed to the nature of the compounds (e.g., hydrophobicity/hydrophilicity and solubility) and operational parameters like temperature, hydraulic retention time, and solids retention time. Nanocomposite membranes have been identified as a viable technology for the removal of ECs from wastewater due to their unique properties and enhanced performance when compared to conventional membranes. They are highly selective and efficient, additionally, they can be designed to specifically remove ECs such as pharmaceuticals, pesticides, and endocrine disruptors. Furthermore, they show greater antifouling properties, reducing the accumulation of contaminants on the membrane surface and extending the lifespan of the membrane, thereby lowering maintenance costs and improving operational efficiency. The aims and objectives of the research report were to compile a comprehensive literature review that highlights the importance of removing ECs from the environment; prepare and characterise four different flat-sheet membranes using polyvinylidene fluoride (PVDF) and imidazolium-based polymeric ionic liquids (PILs) and testing the membranes to determine the retention time and effectiveness of the prepared membranes in removing four different iv pharmaceutical products which are diclofenac, cypermethrin, ibuprofen, and naproxen. The hypothesis assumed that the imidazolium-based PILS/PVDF flat sheet membranes would yield a removal efficiency greater than 90%. This expectation was achieved, and all the membranes achieved a removal efficiency greater than 90%. Various studies have shown that nanocomposite membranes yield high removal rates. The synthesised membranes had better features than PVDF alone. The PVDF alone was found to have the largest pore size and the least retention time, although the removal efficiency was high. The blended membranes lead to higher porosity and retention times. They had smaller pore sizes as compared to plain PVDF; hence, the retention time was increasing. The higher the concentration of the imidazolium, the lower the contact angle measured; this is an indication of a more hydrophilic membrane surface. Hydrophilic membranes are less prone to fouling. The method investigated in this report is simple and can be easily reproduced. Based on the findings of this research report, the methods employed are precise, accurate, highly sensitive, and rapid.
Unlocking Sustainability: An Exploration of the Potential for Food Waste Conversion into Energy and Value-Added Products for Effective Landfill Diversion in South Africa
(University of the Witwatersrand, Johannesburg, 2024) Pereira, Gabriel Philip Alves; Fitchett, Anne
This research report examines the potential for transforming food waste into energy and value-added products as a sustainable strategy for diverting waste from landfills in South Africa. The study uses a social cost-benefit framework to evaluate various waste conversion technologies, including anaerobic digestion, aerobic composting, vermicomposting, and black soldier fly larvae, within South Africa's unique socio- economic and environmental landscape. The study combines quantitative waste composition analyses with technology evaluations, revealing significant landfilling costs and underscoring the economic and environmental urgency of strategic food waste diversion. Highlighting gate fees' critical role, the findings advocate adjusting these fees to incentivise sustainable waste management practices. Notably, Black Soldier Fly larvae and Vermicomposting technologies emerge as dual-benefit strategies for waste reduction and resource recovery. The report calls for policy and infrastructure advancements to enable the broad adoption of these technologies, emphasising their importance in achieving sustainability and economic objectives.
The use of integrated project delivery (ipd) to reduce construction claims in South African mining capital projects
(University of the Witwatersrand, Johannesburg, 2024) Shoniwa, Kuda John; Saghatforous, Ehsan; Laryea, Samuel
The current traditional Design-Bid-Build (DBB) method on capital projects, results in adversarial relationships, insufficient collaboration, poorly defined scopes of work, inadequate designs, unsatisfactory upfront planning, and diminished integration. This often leads to various changes to planned or agreed contractor scope, schedule, cost or quality during construction resulting in numerous and expensive construction claims for additional costs and time which can be reduced by incorporating Integrated Project Delivery (IPD) benefits. In this research, reference to construction claim means a request by contractor for additional cost or extension of time during construction due to changes in planned or agreed scope, schedule, cost or quality. This research study explores the use of IPD benefits to reduce construction claims in South African mining capital projects, contracted under the traditional DBB method. The research question for this study is therefore, “How can IPD benefits be incorporated into the traditional Design-Bid-Build method so as to reduce construction claims in South African mining capital projects?”. The researcher utilised literature review, survey and focus groups, as mixed research methods. Meta-synthesis, questionnaires and interviews were employed, as data collection techniques. Qualitative analysis incorporating descriptive and pattern coding and quantitative analysis were used for data analysis. In answering the research question, a literature review meta-synthesis identified 28 major causes of construction claims including: changes in design and scope, unclear risk allocation, unclear design documents and specifications, inadequate planning and poor communication. Furthermore, 17 benefits of IPD essential to reducing construction claims were identified and included: early involvement of key participants, collaboration, joint decision making, and open communication. The findings show that there is an opportunity to use aspects of IPD and infusing them into the traditional Design-Bid-Build project delivery method to reduce construction claims. IPD benefits present an opportunity to minimize changes later in the projects which in turn assists in reducing construction claims. By understanding the root causes of construction claims and reviewing the effectiveness and deficiencies of current practices used to reduce the claims, a framework that uses identified IPD benefits as remedies to causes of construction claims in capital projects can be developed. The researcher then developed a framework incorporating IPD benefits into the traditional DBB method for South African mining capital projects, to reduce construction claims. This framework will enable project stakeholders to collaborate and integrate early to deliver quality, within budget and on-time projects so that beneficial use of the assets can commence and generate value for stakeholders. Learnings from this research will promote the required changes in behaviour and attitudes in the construction industry which can lead in the direction of full IPD implementation in the future.
An Investigation Into The Propulsive Force Generation Of Multiple Flapping Surfaces
(University of the Witwatersrand, Johannesburg, 2024) Mabvuu, Never; Ho, Weihua
The aerodynamic performance of flapping NACA0012 airfoils was analyzed through numerical simulation, focusing on the effects of stagger, gap, phase difference, and the number of airfoils. The simulation was conducted under specific conditions: 𝑈∞ = 0.2𝑚/𝑠, f=2Hz, 𝛼0=200, C=0.04m, St=0.2 and Re= 8000). The problem was modeled in ANSYS Fluent using a transient viscous approach with absolute velocity formulation, employing the pressure-based coupled solver (PBCS). PRESTO! interpolation and second-order upwind discretization were applied for pressure, momentum, intermittency, turbulent kinetic energy, and specific dissipation rate. Mesh validation and independence studies confirmed that the results were driven by the physics setup, independent of mesh configuration. It was discovered that small stagger and gap at φ=1800 is not good for thrust production as the airfoils produced thrust less than a single airfoil with ∆Ctav = -0.94. However, lift production is increased and ∆Clav =1.2. At larger spacing ∆Ct, ∆Cl and η generally become constant. One of the worst performing cases (X=1.0C;Y=0.5C; ϕ= 1800 ) was improved by making the aft airfoil lead ( φ= -450 ). This explains why insects alter φ or frequency depending on the situation and flight requirements. The most effective X-Y- ϕ were found to be the ones at which flow separation is suppressed. For the 4 airfoils cases the fore pair performed better than the aft pair for the small spacing case. When spacing was increased the aft pair performed better than the aft pair.

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