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Masters Degrees (Civil Engineering)

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    Optimising pulp and paper mill sludge through alternate end of life pathways: enabling the transition towards circularity within the pulp and paper industry.
    (2022) Omarjee, Yusuf Faizel.; Trois, Cristina.; Mahdjoub, Noredine Loeid.
    Globally the pulp and paper industry (PPI) is regarded as one of the most polluting industries in terms of land, air and water pollution, requiring large quantities of process waters. PPI’s process fibres of different origins i.e. virgin fibres, recycled fibres and non-wood fibres. The source of fibre and manufacturing processes employed determines the quantities and composition of wastes generated. Currently most PPIs, globally follow a linear economic model in which wastes generated are landfilled and is not sustainable as we strive towards a shared goal of carbon neutrality. Limited renewable natural resources and landfill airspace are facing increased demands with the latter being non-renewable. Common waste management methods of pulp and paper mill sludge (PPMS) include incineration prior to landfilling, and by enabling a transition towards a circular economy will facilitate the addition of economic value to ‘wastes’ generated. Adopting circularity facilitates the utilisation of alternate pathways by maximising the benefits posed by such resources, simultaneously reducing quantities of waste requiring landfilling. Increased levels of sustainability can be achieved through mitigating the everincreasing demands placed on limited natural resources through reuse and recycling efforts. This research which was a desktop study focused on alternate waste management approaches on PPMS, exploring of alternate end-of-life pathways facilitating landfill diversion, and increase circularity within the PPI. The pathways explored are relevant globally and within a South African context such as the use of PPMS as a soil conditioner and compost, conversion into an energy pellet, anaerobic digestibility, reuse within the pulp and paper industry and mineral based products and as a landfill cover material. They could be used proactively in anticipation of extreme climatic conditions posed by climate change in efforts of reducing our vulnerability to such risks. Circularity within the PPI will allow for the conservation resources like water, soils and wood. Results from this study highlighted the viability of sustainable integrated waste management of the PPI. Pathways explored allow for the PPI shifting away from the cradle-to-grave and towards a cradle-to-cradle approach of the PPI’s wastes. The results also displayed great potential in integrated waste management systems with benefits posed to economic, social and environmental spheres.
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    Stabilisation of base course materials with nanoemulsions.
    (2022) Okem, Eche Samuel.; Mostafa, Mostafa Hassan.
    The province of KwaZulu-Natal, like many geographical locations in South Africa and around the globe, lacks quality materials suitable for pavement construction. Pavement engineers are aware of the dangers of utilising substandard materials in building roadways due to their susceptibility to several forms of distress. Aside from the unrestrained emission of carbon compounds to the atmosphere and the high cost associated with hauling standard materials to the construction site, the continuous depletion of these natural materials results in distortion of the environment. Several techniques are employed to enhance substandard construction materials using traditional and non-traditional stabilisers; however, many researchers have proven the latter's effectiveness at improving marginal paving materials over the former. The use of nanotechnological products, including nano polymers and nano-modified emulsions on South African pavements, is still at the experimental stage; however, numerous research studies using this technology are promising and could lead to the ultimate transformation of pavement structures that will satisfy the current environmental demands. Nanoemulsions can be formed using emulsifying agents to break down larger droplets of one liquid into smaller, more uniformly dispersed droplets throughout another liquid. This study aims to improve the performance of a substandard base course material with nanoemulsions. The study also seeks to provide a long-lasting wearing course for unsurfaced roads in South Africa and across the globe. In this current study, two stabilisers designated as nano A and B were obtained from two manufacturers in South Africa. The stabilisers were mixed by mass at 0,7% - 1,5% with the soil sample, and the results indicate an optimum content at 1% and 1,2% for nano A and B, respectively. The impact of the stabilisers on the material was evaluated through California bearing ratio, unconfined compressive strength, and indirect tensile strength tests. Analysis of the experimental results reveals that nano A and B significantly improved the bearing strength of the material by as much as 53% and 92%. Significant improvements were also noted in the results of unconfined compressive strength and indirect tensile strength. Evaluation of the effect of rapid and 28-day curing conditions on the specimens yields similar results. Nano B also showed great potential by creating a hydrophobic effect in the soil matrix. These enhancements would prevent moisture damage in the stabilised layer and ensure the construction of quality roads.
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    The feasibility of a network materials utilization plan, with an emphasis on upcycling of material.
    (2022) Naicker, Salome.; Mostafa, Mohamed Mostafa Hassan .
    In most countries, the road network is under the jurisdiction of an agency that is state-owned. Road agencies have the responsibility for the management, maintenance and development of the network through careful management of resources taking into consideration the financial obligation to manage public funds. Kasim et al. (2005) quantify that the cost to manage materials can range from 30-80% of the total construction costs. Because these costs are so high, they can determine the winning bidder. This gives rise to the need for the agency to reuse materials to their full potential and ensures the optimal salvage value of each material. The fall back design approach is to down cycle materials by recycling the existing pavement layers into lower-value layers. This design approach becomes questionable when the road agencies have a responsibility to optimally reuse the agency’s current assets. Due consideration of the financial obligation to manage public funds underpins the need to upcycle. Materials from the existing layer and materials required from external sources are managed in the Materials Utilisation Plan. The aim of the research is to investigate the opportunities of upcycling in a Materials Utilisation Plan. The objective of the research is to determine the factors influencing the specification of upcycling in the design of a Materials Utilisation Plan, to assess the effect of the identified factors and to produce a set of recommendations when implementing upcycling in a road upgrade project/program. Competitive tendering is the procurement process followed by potential design consultants, whereby the consultants, bid against each other to win a tender. The efficiency of the tendered resource becomes a major influential factor when competitive tendering is adopted. The consequence of such an environment is reduced rates and reduced hours with no additional capacity for any additional design improvements as described by Messner et al. (2018). The design for upcycling is the process of applying engineering judgment to assess the existing materials and determine its function in the new pavement. The use of engineering judgement is pinned on relevant design experience, the lack of adequate design experience to facilitate upcycling was a recurring theme throughout the research. The reliance on the catalogue design for pavements was emphasized as a major disbenefit to upcycling. Planning is the process of forethought into the project requirements. At the planning stage, key decisions are made. The design philosophy and design strategy is developed to meet the objective of the clients. The type of contract implementation is influenced by the decisions made at the planning stage. Technology advancement is the application of new, more accurate or more efficient use of scientific methods or equipment to improve on previous methods. The use of nanomaterial and nanotechnology in pavement design is gaining momentum. Design engineers are still to respond to the advancement in technology so that the industry can progress in the various methods of upcycling. There is a fundamental mismatch between the knowledge learned at tertiary level and what is being implemented in the industry. The data collected indicated a gap in knowledge relating to upcycling of materials, stemming from tertiary level education. The gap in knowledge was based on the undergraduate syllabus not including current industry practices. Upcycling is a fundamental concept and must be engrained at the tertiary level so that graduates can rely on the knowledge gained to enhance and improve on methods of upcycling. Exposure at tertiary levels promotes further research in the field.
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    Application of multi-criteria decision analysis integrated with GIS and air pollution model inputs for schools site selection.
    (2019) Abera, Yared Getachew.; Kumarasamy, Muthukrishnavellaisamy.
    Schools site selection is an essential process which needs knowledge of different fields. The process involves scientific justification, judgment and a finding of suitable land, which consider financial, social, ecological and political perspectives, that limit conflicts and supports agreement among the decision makers. Lack of scientific analysis may negatively impact on the economy, health, and safety of the public. However, reports revealed that finding of school location managed without utilization of scientific analysis thus prompted the development of schools in unsuitable areas and caused pupils to face several problems such as long walking distance, heavy traffic, presentation to sound and air pollution (Bukhari et al., 2010). Addis Ababa is the largest city in Ethiopia, and the city needs additional schools to meet the minimum pupil section ratio as per the national standard to improve education excellence (CGAAEB, 2018). Currently, most of the existing schools placed in the central part of the city; thus such scientific analysis is vital to give insight for the decision makers and planners to improve the site selection process for new schools, to provide a fair distribution of education access and utilizing a limited available resource. Nowadays, the application of GIS and Remote sensing datasets widely used to support the site selection process. In this study GIS integrated with MCDA and Remote Sensing, techniques have been used to select suitable school locations. MCDA is a tool that devoted to improving the decision-making process using various qualitative and quantitative criteria goals or objectives of a contradictory nature. This study attempts to use an air pollution model integrated with Remote Sensing, Geographical Information System (GIS) for Multi-Criteria Decision Analysis (MCDA) to identify optimal sites for new schools. The MCDA was done using Analytical hierarchy process (AHP), which classify criterions in hierarchical level and assigns a relative weight to each criteria using pairwise comparison. The selected criteria in this study decompose into three main groups, namely Economy, Accessibility, and Environmental Safety. Besides, Landsat 8 OLI/TRIS satellite image was used to quantify the annual mean concentration of Particulate matter with diameter 10 μm (PM10) for Environmental safety criteria. Subsequently, using Weight overlay tool, the criteria maps combined based on their relative influence, which is obtained from AHP to produce the final map, and the map reclassified as not suitable, less suitable, suitable and most suitable, using Arc GIS 10.4 reclassify tool. The resulting map of the annual mean concentration of PM10 shows that the concentration amounts on airports, factories, and road structures are high. The criteria weights obtained are 54%, 30% and 16% for Economy, Environmental Safety, and Accessibility respectively. The ultimate suitability map shows that 3.89% of the study area is most suitable, 57.47% is suitable, 38.48% is less suitable, and 0.08% is unsuitable, the most suitable areas laid on the city’s north-east and south-east part, which are away from existing schools. Therefore, this study successfully suitability model has been used to allocate an optimal place for new schools to be built in Addis Ababa capital using GIS integrated MCDA with Air pollution model input.
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    The optimisation of baffle arrangements for minimal sediment washout in standard stormwater sumps.
    (2022) Paideya, Leshalen.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishnavellaisamy.
    Sediment in stormwater drainage systems is a matter of great concern due to its ability to collect within stormwater pipes to form blockages. Furthermore, sediments transport harmful pollutants, depositing them in stormwater discharge areas and disturbing the ecology of those areas. Standard stormwater sumps are a reliable and cost-effective solution to trap and retain sediment within stormwater drainage systems for manual removal. However, under high flowrate and fine sediment conditions, the effectiveness of standard sumps drastically decreases. A solution to this issue is the installation of baffles that can be retrofitted into the standard sump as a method of reducing flow velocities to allow sediments to settle to the sump bed. An aspect of this solution, as equally important as sediment trapping, is the prevention of sediment washout. During a storm event, sediment previously trapped in a stormwater sump can be washed out before the routine cleaning period. Therefore, it is paramount to ensure that the baffle arrangement effectively prevents the resuspension and washout of sediment already present in a standard sump. This dissertation investigates the use of baffle arrangements to minimise sediment washout in standard sumps and determine a baffle arrangement that will provide the best sediment retention results while remaining a feasible and practical solution in a real-world context. Three baffle arrangements, consisting of a combination of solid and semi-porous baffle plates of varying dimensions placed in different orientations, were chosen for this investigation based on their previous success with sediment trapping. The primary methodology of this research compared the effectiveness of these baffle arrangements in minimising sediment washout by comparing them to a control setup with no baffles, using a simple mass-balance process. Additional experimentation involved using an Acoustic Doppler Velocimeter (ADV) to develop flow velocity fields to motivate the observations made in the mass-balance tests. All baffle arrangements performed better than the control setup, with the least effective of the three designs improving sediment retention efficiency by 22% and the most effective by 71.5% under the worst-case condition. These results were then dimensionally analysed to determine the results of such testing under real-world conditions. The results of this analysis were also promising, with the best baffle arrangement achieving retained effluent concentrations of up to 0.4 kg/m3 when calibrated for typical standard sump dimensions and peak flowrate.
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    Non-linear finite element analysis on single-headed anchor under shear loading in concrete compared to predictive design models.
    (2023) Muledy, Mayembe.; Drosopoulos, Georgios A.; Olalusi, Oladimeji Benedict.; Mcleod, Christina Helen.
    In recent years, advances in technology-aided design tools have made the construction of complex structures increasingly easier. Consequently, there is growing research interest in using different fastening techniques to understand how components of an engineering structure connect to ensure resilient designs. For instance, depending on the installation methods, the construction industry uses a variety of anchorage systems, such as cast-in-place anchors and post-in-place anchors. Previous studies have predominantly focused on understating the behavior of concrete anchors subjected to shear loading utilizing Finite Element Analysis (FEA) explicit dynamic solver. However, there is scanty evidence of work that analyzed the concrete behavior of a single cast-in-place headed anchor subjected to shear loading using an FEA static solver. Understanding the nonlinear behavior of a single concrete-headed anchor under loading and the consequent failure loads associated with concrete edge breakout depends heavily on the type of analysis. This dissertation examines the nonlinear behavior of a single concrete-headed anchor using a concrete model that was created using solid 65 element in Ansys static structural. The proposed model accuracy is validated by comparing numerical study results to experimental test results. However, the impact of the anchors in-group is not taken into account in this study because it solely addresses single-headed anchors loaded in shear. In addition, this study evaluated uncertainties and bias based on i) the Concrete Capacity Design (CCD) model, ii) the European standard (EN1994-2:2009), iii) the analytical predictive models from Anderson and Meinheit (2006), and iv) the Grosser model (2006). While the first two are drawn from the codes, the second two are derived from literature on anchorage with concrete edge breakout failure. The study employed statistical analysis and linear correlation to examine the uncertainties and biases of each predictive model. Overall, the failure loads derived from the numerical study were higher than the loads obtained from the findings of experimental test results. Nevertheless, in some instances, results obtained from numerical analysis were much lower than the experimental test results. This exception points to several assumptions made regarding the constitutive materials law of concrete and steel anchors. The statistical analysis and model uncertainties quantification of each predictive model indicates that the Grosser model is the most excellent predictor of concrete breakout capacity of single-headed anchor subject to shear loading, followed by Anderson and Meinheit (2006), EN2, and CCD.
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    An assessment of the strength and durability characteristics of recycled plastic pavers.
    (2022) Maharaj, Kiash.; McLeod, Christina Helen.; Friedrich, Elena.
    The generation of waste is reaching record highs and displays a consistent uptrend over the last decade, and despite high generation rates, landfilling is still the dominant disposal method for waste in South Africa. However, these materials may have potential for reuse in several applications, and industries are considering their viability. One such industry is the construction and engineering industry, which has seen an increase in research into the application of waste materials. This study explores the use of HDPE, PP, and glass waste as an alternative material for making concrete pavers. The study uses local waste materials to assess the density, durability, and mechanical strengths of the resulting paver, called Eco-pavers, and compares them to regular concrete pavers for accuracy. The pavers are made of a 50/50 blend of recycled plastic and glass aggregate, which has not been widely studied as a replacement for cement or stone aggregate. The Eco-pavers demonstrate a low water absorption rate of 0.28%, compared to the 4.5% of concrete pavers. After immersion testing in various chemicals over a 180-day period, the pavers show no signs of degradation either structurally or visually. The Eco-pavers are suitable for use as impermeable pavers, as they did not allow any infiltration during the permeability test. The flexural strength assessment resulted in an average breaking stress of 7.9 MPa, which is greater than the prescribed minimum. However, the pavers' average compressive strength is 12.47 MPa, which is below the minimum criterion of 35 MPa for pavers, and therefore needs improvement. In summary, this study explored the use of recycled plastic and glass waste in manufacturing Eco-pavers as an alternative to traditional concrete pavers. The resulting pavers demonstrated low water absorption, chemical resistance, and impermeability, making them suitable for impermeable applications. However, the compressive strength of the pavers needs improvement. While their short-term use is unlikely to release microplastics, further research is needed to determine their long-term impact.
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    Investigating uncertainties in shear resistance prediction of beams without stirrups.
    (2023) David, Abayomi Bolarinwa.; Olalusi, Oladimeji Benedict.
    Optimizing a model’s performance should keep the functionality within the confines of safety and economy; deviation from these calls for a reliability investigation of such models. In a bit to optimize shear models for simplicity, safety functionality and economic performance have been an issue of a trade-off as the overestimation or underestimation of the model's intended purpose may occur. Overestimating the shear resistance of flexural members raises safety concerns since it might lead to unsafe design practices that ultimately cause the entire structure to collapse. In the same manner, underestimating the shear resistance may give rise to uneconomical designs. In this research, the predictions of various code-based & authorial shear resistance models in terms of their structural performance were assessed through the model uncertainties. According to Gino et al. (2017), identifying and quantifying the uncertainty related to a specific model is of high relevance to structural safety verification in the course of reliability assessment. Uncertainties related to models adequately capture the inconsistency of models’ performance across varied structural conditions. Hence, the extent of conservatism demonstrated by shear models of beams without stirrups is investigated towards structural reliability assessment and calibration. A database of 784 experimental beams without shear reinforcements compiled by Reineck et al. (2013), consisting of beams with varying geometrical properties was investigated in this study. Analyses conducted in this study include a mean values analysis (best-estimate prediction without any form of bias) and a deterministic design value analysis (inclusion of partial safety factor or reduction factor and characteristic material properties). Shear values derived from mean value analysis are used as the input parameter to determine the uncertainty of each model for the same structural condition. Supervised machine learning models based on the architecture of the Artificial Neural Networks, Support Vector Machine, Decision Tree Regressor and Random Forest were also used for shear resistance predictions. Model uncertainty was also derived for machine learning predictive shear models. A comparative analysis between the experimental shear resistance and all considered predictive model was done. Statistical characterization of each model factor in terms of the bias, standard deviation, coefficient of variation and skewness was carried out to evaluate the model’s performance in order to adopt a general probabilistic model for subsequent reliability evaluation. Sensitivity analysis of model uncertainty to parametric variation of input parameters was also carried out with the measured value of correlation. The provision of a carefully calibrated partial factor for model uncertainties that will take into account the uncertainty associated with shear methods is the most efficient management of the reliability performance for any resistance method. To this end, the calibration of a partial factor of safety according to EN 1992-4 was done for models with poor performance in terms of uncertainty performance indexes such as sensitivity to model parameters, a large degree of variability in shear prediction and significant bias in prediction.
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    Modelling the Agulhas Ocean Current: with a focus on the related shallow water hydrodynamics in and around the Durban Bay, South Africa.
    (2021) Naidoo, Kemira.; Pringle, Justin James.; Stretch, Derek Dewey.; De Graaff, Reimer.
    The Agulhas Ocean Current is a powerful and persistent western boundary current that flows along the continental shelf edge off the eastern coast of South Africa in a southerly direction. In addition to the tide- and wind-induced currents, the Agulhas Current influences the nearshore currents in Durban Bay, for example, the Durban Eddy. eThekwini Municipality and Deltares proposed that Durban be used as a pilot study to investigate the capabilities of developing a Delft3D Flexible Mesh (D-Flow FM) model that integrates the combined forcing of ocean currents, tide and wind in a coastal model domain, which once successfully achieved, is to be integrated within eThekwini’s Forecast Early Warning System. The aim of this study is to use D-Flow FM to accurately model the Agulhas Current and analyse its effects on the nearshore waters of Durban. Output from global ocean models, such as the NEMO models operated by E.U. Copernicus Marine Service Information (CMEMS) in the Global Reanalysis Multi-Model Ensemble Product (GREP), include the Agulhas Current but are not suitable for coastal applications due to their relatively coarse resolution and absence of tidal forcing. For this reason, model output from the GREP was downscaled to a coastal scale using a D-Flow FM model of KZN with appropriate boundary conditions and evaluating the use of a new Delft3D nudging technique. The final D-Flow FM model that was developed applied a relatively high-resolution grid on top of the continental shelf. A stable ocean current was simulated by forcing the model with a full set of 3D ocean boundary conditions, including currents, salinity, temperature, sea surface anomalies. In addition, the model was forced with tide and wind. Model tests showed that the nudging technique was not required when applying a suitable model extent. Realistic currents seem to develop along the edge of the shelf in the D-Flow FM model as observed from literature and measurements. The final coastal model output was compared with Acoustic Doppler Current Profiler (ADCP) data from ACEP (African Coelacanth Ecosystem Program) and data from a SADCO (Southern African Data Centre for Oceanography) database off Durban. The results of the D-Flow FM coastal model correlated better with these measurements when statistically compared to data from the GREP. The D-Flow FM coastal model was used to reproduce the Durban Eddy and analyse its modelled characteristics. The modelled duration of the eddy was between 8 to 10 days, which included the formation and dissipation of the eddy. A monthly average in agreement with previous observational studies of 1.66 eddies was seen from model outputs, with the reversal of currents along the Durban coast whenever an eddy was present.
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    Data-driven multiscale homogenization for composite materials.
    (2021) Eze, Chukwuemeka Charles.; Drosopoulos, Georgios A.
    No abstract available.
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    Feasibility of run-of-river hydropower for rural and agricultural productivity in South Africa.
    (2021) Makalima., Lazola Qhawe Mfundo.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishna Vellaisamy.
    The Southern African Community Development (SADC) intends to increase its irrigated area to increase the agricultural productivity of the land. Run-of-river hydropower systems present an attractive solution of providing energy where it is not feasible for alternative energy sources and extend the grid infrastructure to improve the livelihood of rural communities and increase agricultural productivity. The site geographical location and topography of power plants have made it impossible to guarantee fixed costs from suppliers and manufacturers, leading researchers to develop formulae that predict the cost behavioural tendencies of the electro-mechanical components of the power plant as a function of hydropower parameter inputs and other costs. Hydropower systems are very site-specific as they are affected by their geographical location and the site's topography. The difficulties from suppliers and manufacturers in failing to guarantee fixed costs have resulted in designers using developed formulae to determine the scheme's costs. This investigation aimed to develop a model that would allow designers to determine whether run-of-river hydropower would be feasible or not for a specific location in South Africa. This was achieved through a pre-feasibility model based on a '3 Pillar Concept' of social, environmental, and economic test for sustainability, which according to research, has 49 sustainability indicators for run-of-river hydropower systems measured directly or indirectly. The Levelised Cost of Electricity (LCOE) from hydropower was used to determine the economic feasibility of hydropower systems. From previous research, LCOE evaluation for small hydropower projects in developing countries ranged between 0.02USD/kWh and 0.10USD/kWh, making small scale hydropower systems very cost competitive for electricity generation to the grid or schemes for off-grid rural electrification. Run-of-River hydropower systems are classified as small hydropower systems and generate from 1MW to 20MW. The projects demonstrated in this report were Micro and Mini hydropower systems which are significantly larger than Pico hydropower systems. The sites selected for the study are U2H014 located downstream of Albert Falls dam, U3H005 downstream of the Hazelmere dam, U2H052 downstream of Inanda dam, and V1H002 downstream of Woodstock dam. The potential power of the available energy was quantified using available streamflow data. Flow duration curves were developed from streamflow data and were used to develop power duration curves for the hydropower plants. LCOE for the investigated sites ranged between 0.02USD/kWh and 0.10USD/kWh. The power duration curves showed that the smallest power plant was U3H005 and generated 48kW. The groundwater pumping requirements for rural and agricultural productivity is found to be 31.1kW. Results obtained at sites U2H014 and V1H002 were 238kW and 314kW, respectively. The smallest power plant could generate enough power for rural and agricultural productivity with power savings that could be sold to the grid or power the community. The results obtained at the sites were positive and acceptable.
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    Smoothed particle hydrodynamics (SPH) modelling of nearshore breaking waves.
    (2021) Mahomedy, Ayesha.; Stretch, Derek Dewey.; Pringle, Justin James.
    Breaking waves drive sediment transport in the nearshore zone of coastal regions and directly govern beach transformation. Accurate coastal modelling of breaking waves is essential to predict sediment transport accurately. Efficient and sustainable management of natural coastal systems and urban coastal developments relies on accurate sediment transport predictions. This study proposes a mesh-free, Lagrangian, smoothed particle hydrodynamics (SPH) model to simulate nearshore breaking waves in two-dimensions. This study emphasises using SPH to evaluate the wave field parameters (local velocities, vorticities, and shear stresses) that can be used to predict coastal phenomena, namely sediment transport in nearshore, wave-driven environments. This study showed that a two-dimensional SPH model could replicate the free surface of nearshore breaking waves and accurately predict the flow characteristics beneath breaking waves. However, the accuracy of the results can vary depending on the position of the breaking wave in the surf zone. Furthermore, SPH applications must choose between accuracy and computational efficiency. The key SPH calibration parameters identified were the artificial viscosity coefficient (α), the dimensionless smoothing length ratio (hSPH/dp), and the particle resolution (H/dp). Extensive comparative analysis was performed between simulated results and measured data to obtain suitable parameter values for a plunging solitary wave. A suitable choice of α=0.1, hSPH/dp=3, and H/dp=90 were selected based on the results. Furthermore, the results suggested that a suitable choice of model parameters depends on the viscosity treatment method (artificial/sub-particle scale viscosity approach) and the type of wave breaking simulated (plunging/spilling). Thus, α=0.1, hSPH/dp=3, and H/dp=90 were only deemed suitable when the standard SPH artificial viscosity approach is used to simulate breaking plunging and spilling waves on beach slopes milder than 1/10. The model sensitivity to α, hSPH/dp, and H/dp was also investigated based on the numerical wave energy dissipation and simulated wave surface of a plunging solitary wave in the space and time domain. When α was above or below the ideal value of 0.1 for a given hSPH/dp and H/dp, the numerical wave energy dissipation and wave height at breaking did not match the measured data. The choice of α was strongly related to H/dp, and a reduced α became more appropriate for a lower H/dp. The results also showed that the model was less sensitive to hSPH than the choice of α and H/dp in terms of the model performance. However, when hSPH/dp was less than 1, for any given α and H/dp, the numerical wave energy dissipation and wave height at breaking were under-predicted. The choice of H/dp was of principal importance and influenced the choice of the other model parameters. When H/dp was below the ideal value of 90, for any given α and hSPH/dp, the numerical wave energy dissipation and wave height at breaking did not match the measured data. Additionally, the breaking wave shape was poorly simulated. However, H/dp=90 becomes computationally expensive when simulating breaking waves in large numerical domains or with relative wave heights significantly less than 0.6. Hence, the available computing power limits the choice of H/dp. The performance of a two-dimensional SPH model was assessed by analysing the simulated flow field under several breaking waves. The local velocities, vorticities, and bed shear stresses were evaluated beneath two plunging solitary waves and a spilling solitary wave. Generally, the characteristics of the simulated flow field were fairly accurate during wave shoaling and wave breaking, less accurate during wave run-up, and inaccurate during wave run-down. The results also hinted at obliquely descending eddies occurring under the breaking plunging waves. However, the three-dimensional eddy structure beneath the breaking waves could not be investigated due to the limited two-dimensional nature of the model setup used in this study. A well-calibrated SPH wave and hydrodynamic model is an important coastal engineering tool. Thus, this study can serve as a physically based framework for using a two-dimensional SPH model to investigate coastal engineering problems that include wave-structure interactions, wave-run up on beach slopes and sediment transport in the surf zone over a wide range of scales and wave conditions.
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    Optimizing rainwater harvesting systems in the eThekwini Municipality: a case study of a public school.
    (2021) Maharaj, Praval.; Friedrich, Elena.
    Rainwater harvesting (RWH) provides a unique perspective for water conservation, especially when considering the South African water crisis. Harvested rainwater could potentially be used for activities like toilet flushing, thereby reducing the strain on municipal supply networks. However, the economic and environmental feasibility of such systems needs to be assessed in relation to their water-saving benefits. Therefore, this research aimed to uncover the viability of two types of RWH systems implemented at a school (Duffs Road Primary). The assessment and design of the two systems (pumped and gravity-fed) were performed providing insight into system optimization in the economic and ecological settings. Water harvestings, municipal cost savings, and municipal carbon emission reductions were key aspects of each system's performance. Economic considerations included capital costs and return periods, while the environmental aspects encompassed system carbon footprints (assembly and operation) and carbon emission reduction periods. Life cycle assessments (LCAs) of the system components were also incorporated into the research, acting as an extension of the environmental feasibility analysis. The LCAs were performed using a software-modelling program called SimaPro. It was found that the gravity-fed system outperformed the pumped system in both economic and environmental contexts. Although the pumped system garnered higher harvestings and municipal savings and was also deemed economically feasible with a return period of under 6 years, the presence of pumps made the system ecologically inviable. On the other hand, the gravity-fed system would allow for yearly benefits of 452.48 kL in water savings, R27 850.94 in municipal cost savings, and 185.11 kg CO2 in municipal carbon emission savings. Including the fact that the return period would be less than 5 years and the period to reduce the system carbon footprint at just over 10 years, the system displayed both economic and environmental viability (from a global warming perspective). Besides the gravity-fed system costing less, it would also eliminate environmental emissions that would usually be generated from pump operation. Furthermore, energy usage and costs associated with pump operation would also be non-existent. However, the construction/production of the components of the gravity-fed RWH systems would always result in environmental burdens as assessed using the SimaPro software. Hence, recommendations for alternate materials that are more environmentally friendly may be possible for future endeavours.
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    Modelling the effects of soil variability on stability analysis of natural slopes in Durban.
    (2021) Arbee, Khadija Mohsin.; Aneke, Frank Ikechukwu.; Mostafa, Mohamed Mostafa Hassan.
    Slope failure occurs due to various factors, one of the most significant being that of soil variability in a slope and associated geological threats such as unconsolidated soils, settlement, groundwater seepage and infiltration. The analysis of slope stability should incorporate and analyse the interactions between slope configuration, shear strength resistance, pore-water pressure and water conditions of a slope. This study focuses on the causal effects and slope stability of two natural slopes in Durban, KwaZulu-Natal. Large parts of the study area are underlain to great and varying depths by problem soils, namely the Berea Red Sands. These are dune soils, deposited by ancient wind activity, that are found parallel to the east coast of Durban. The Berea Red “sands” vary greatly in soil type ranging from fine grained sands to silts and clays. Those of looser consistency are known to undergo significant settlement under loading, and also with water interaction. The clay and silt varieties are known to exhibit heave under the same circumstances. In some cases, liquefaction of Berea sands may occur due to the loss of soil structure upon water introduction into the soil mass. The aim of this research is to formulate and compare the stability of the two slopes under different water conditions in the form of Factors of Safety and Probabilities of Failure, using RocScience© software. Site investigations were conducted to classify and collect soils, which were then put through rigorous laboratory testing. The results from testing were applied where possible to the modelling software and a host of important findings were made. The liquefaction potential of poorly graded, uniform Berea sands was observed first-hand on site, in the laboratory and again during slope stability analyses. As anticipated, the slope stability of both sites proved to increase reaching “optimum” conditions due to the positive effects of matric suction. Upon increasing water conditions further or saturating the slope, increasing incidences of failure and instability occurred due to the loss of matric suction and cohesion. This instability can also be attributed to the proven decrease in shear strength properties of the soil, cohesion and internal friction, leading to loss of shear strength in the slope. The positive effects of matric suction were further proven when the slope of Site A that considered matric suction (in the form of an air entry value), exhibited a slightly higher FOS and improved slope stability than the one without. The results and conclusions of this research project prove the importance of investigating a soils variability and the subsequent slope reaction under varying moisture conditions. These are key factors to consider prior to civil construction on problem soils, so as to mitigate major failures and the consequences thereof.
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    Mixing and turbulence in floating flexible photobioreactors.
    (2021) Naidoo, Kélan.; Stretch, Derek Dewey.; Pringle, Justin James.
    Renewable energy initiatives aim to advance global efforts toward a sustainable bioeconomy. The power generation industry is the most crucial sector requiring strategic planning to achieve economic and environmental sustainability. Biodiesel production utilising microalgae as a feedstock yields a ± 400% larger production range compared to traditional feedstocks. Floating flexible photobioreactors (FPBs) aim to provide largescale microalgae enclosures and promote biofuel production's commercial application. FPBs are placed off-shore, where they naturally accelerate microalgae growth by harnessing wave energy, sunlight, waste carbon dioxide and wastewater discharge (as a nutrient source). Microalgae production requires explicit physical and chemical conditions to achieve optimal growth rates. In this study, a physical FPB model is constructed within a laboratory wave flume where the change in the internal fluid motion within the FPB is observed under an idealised wave pressure constriction. Under the influence of an idealised wave, the flexible tube experiences a reduction and expansion in its crosssectional area, which deforms the internal fluid flow. The fluid’s flow structure is analysed using particle image velocimetry (PIV). PIVlab was used to analyse the data. The fluid moves backwards (or towards constriction) when placed under direct tube constriction; however, under unrestricted tube expansion, the fluid is propelled forward in the original direction of the idealised wave, in the form of a bulge wave. Relative to the constriction, the fluid moves negatively on the left-hand side of the peak and positively on the righthand side. Regions of strong shear in which there was a rapid change in the velocity were identified as potential mixing zones.
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    Alternative binder materials for rigid pavements – an investigation into the structural and sustainability effects of partial cement replacement with pulp and paper mill waste ash in concrete pavements.
    (2021) Pillay, Deveshan Loganathan.; Mostafa, Mohamed Mostafa Hassan.; Olalusi, Oladimeji Benedict.
    Abstract available in PDF.
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    Development of an automation model for leakage reduction and energy harnessing through optimised placement and setting of pressure reducing valves and pump as turbine placement in water distribution networks.
    (2021) Pillay, Ethan.; Adu, Joy Tuoyo.; Kumarasamy, Muthukrishna Vellaisamy.
    Water leakage is of paramount interest in South Africa. Due to the increasing population density access to drinking water will be scarcer, as much of the water produced is lost through leakages. South Africa’s non-revenue water (NRW) accounts for approximately 30% of the total water supply, with leakages accounting for more than 70% of NRW in a network. Water leakage losses are defined as water lost during transportation to the consumer from the water source. Reducing leakage losses in existing networks is a major task for engineers, as replacing pipes is costly. There is a direct relationship between the pressure in a water distribution network (WDN) and the network’s leakage losses. Network pressure is affected by many factors such as consumer demand, nodal elevation differences and network characteristics. The easiest and most cost-efficient method of pressure reduction in existing WDNs is through efficient pressure management. Developing methods to reduce the excess network pressure will reduce the leakage losses in the network. There is currently little research that incorporates optimising pressure-reducing valve (PRV) placement to regulate network pressure and reduce leakage losses. Furthermore, the use of pumps operating as turbines (PATs) to harness energy in WDNs has not been fully explored. Literature gaps encompass optimising and automating these processes and creating an algorithm applicable to complex WDNs. This dissertation presents a new optimisation model aimed at minimising network leakage losses within a WDN by determining the optimal placement and setting of additional PRVs. Energy generation from excess pressure is a secondary benefit and by-product of pressure reduction and can be harnessed by replacing PRVs with PATs. Replacing PRVs with PATs to harness renewable energy from the WDN is also incorporated into the new optimisation model. Automation of the model has been achieved using MATLAB and EPANET. The objectives of this study are to create a mathematical model to optimise the placement and setting of additional PRVs within a WDN, following all hydraulic, mathematical, and linear constraints. The model must determine which PATs can feasibly replace PRVs within a WDN to generate electricity and the PAT’s potential power output and potential gross margin. The mathematical model must be automated using MATLAB and EPANET. The newly created objective function is made up of two stages to account for the multiple objectives. The model has been applied to two real-world networks: the Cornubia Integrated Human Settlement Development Phase 2A- Zone 1 network and the Pat Marshal Housing Project. The proposed methodology’s ability to reduce network pressures, reduce associated leakage losses, and generate energy has been demonstrated. The network leakage losses minimisation accounts for the hydraulic characteristics and constraints of each WDN in the form of mass continuity equation constraints at the nodes, momentum balance constraints along the pipes, network constraints, and pressure reducing equipment constraints. Five successful additional PRVs have been optimally placed and set within the Cornubia WDN, achieving a 12.8011% leakage rate reduction. Two successful additional PRVs have been optimally placed and set within the Pat Marshal WDN, achieving a 27.907% leakage rate reduction. The model has determined that nine of the 36 PRVs in the Cornubia WDN can be feasibly replaced by PATs to harness 135.48 kW of energy, equivalent to a Mini-hydropower plant, with a 948.67 MWh per annum output. One PAT can feasibly replace a PRV in the Pat Marshal WDN to harness 24.55 kW of energy, equivalent to a Micro-hydropower plant, with a 131.6 MWh per annum output. The energy produced could be sold to realise gross margins of approximately R920 211.17 and R127 662.30 per annum for the Cornubia and Pat Marshal WDNs, respectively. The results obtained from the newly proposed method are positive, significantly reducing the leakage rate in both networks. The excess pressure from the networks can be efficiently harnessed to generate renewable energy to be utilised or sold.
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    The impacts of climate change in relation to plastic waste on the Umgeni River system.
    (2021) Khan, Muhammad.; Trois, Cristina.
    The use of plastics and plastic by-products have become so profusely common in everyday life of society that the issues attached to its recycling, disposal and preventing contamination to our soils, rivers and oceans have become a global concern. The amounts of plastic waste in the form of macro- and micro-plastics have reached a level of threat to our rivers and oceans' waters, posing detrimental impacts on our aquatic life, as the marine species are mistaking the plastic debris wastes for food and subsequently affecting human health. Plastic waste in the marine environment is a rising global concern, and it is connected to various environmental and socio-economic consequences. Plastic debris found in marine environments primarily originates from land-based sources, and it is estimated that annually 4 – 12 million tonnes of improperly managed plastic waste enter the marine environment. This research focuses on plastic waste along the Umgeni river before it reaches the ocean. This research proposes undertaking a study at the Umgeni river system to monitor the amounts and characterisation of waste retained at the litter boom system and provides suggestions of optimised locations for the placement of litter booms to maximise the collection and removal of plastic waste. Furthermore, it looks at the valorisation of plastic waste using the WROSE model.
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    Sustainable electronic waste management at the University of Kwa-Zulu Natal: developing an integrated waste management plan using the W.R.O.S.E model.
    (2022) Govender, Mayuren.; Trois, Cristina.
    Electronic waste (e-waste) is the fastest growing waste stream in the world and is increasing exponentially, this growth poses a significant problem in the current waste management systems. The current waste management systems, worldwide, are not designed to manage ewaste, and therefore most of the e-waste is mismanaged. E-waste is the most valuable waste stream, as it contains a high concentration of precious metals (as compared to primary minerals), however, it has a significant concentration of toxic material. The mismanagement of e-waste can have disastrous effects on both human health and the environment. This study focused on improving the e-waste management of the University of Kwa-Zulu Natal (UKZN). UKZN was selected because Universities are considered the frontier for research and development, and often establish higher standards for social responsibility and environmental conservancy than other institutions. The objectives were to firstly investigate the current e-waste management practices, to determine the appropriate strategies that were used to create an integrated waste management plan (IWMP). The required data for the study was obtained using a structured questionnaire, as it allowed for both the qualitative and quantitative data to be collected at once. The questionnaires were distributed across all five campuses and the data was collected. The analysed data established that UKZN generates a significant volume of e-waste, and the respondents confirmed that UKZN did not have an e-waste management plan and rather ewaste was treated as ordinary waste. Positive feedback from the respondents suggests that they would be accepting of an e-waste management plan. The IWMP was designed based on the potential volume, composition, and expected quality of the waste stream. The strategies employed were evaluated to ensure economic, environmental, and social sustainability, in both the short term and long term. The IWMP was designed to help create a circular economy and to ensure that e-waste is managed sustainably, and the resources are conserved. The study concluded by demonstrating that it was possible to manage e-waste sustainably, thereby not endangering either human health or the environment while still being economically feasible.
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    Assessment of heavy metal contamination in soils around Krugersdorp mining area, Johannesburg, South Africa.
    (2020) Mkhize, Thabani Armstrong.; Friedrich, Elena.
    The mining industry remains a driving force of the South African economy, making a significant contribution to economic activity, job creation and foreign exchange earnings. However, in the process of mining and mineral production, millions of tons of waste are produced making this sector the potential source of air, soil and water pollution. There are more than 270 waste dumps known as tailing dams in the Witwatersrand Basin alone, covering 400 square kilometres in surface area (Oelofse et al., 2007, Rosner, 1999). Poor management of these tailing dams and waste rock dumps lead to uncontrolled release of acid mine drainage that in some cases cause soil degradation and water contamination around these sites. The aim of this study was to assess pollution levels of As, Cd, Cu, Cr, Pb, Hg, Ni and Zn in soils from the mining area of Krugersdorp and to compare them with the South African and international standards. The geo-accumulation index (Igeo), the single ecological risk factor (Er), and potential risk index were calculated to assess the degree of contamination by these metals in soils. Thirty one soil samples were collected from eleven different sites around the Krugersdorp area. Twenty three were collected from the Krugersdorp Game Reserve, four from private farmland, two from Mintails Gold Mine and two from Rand Uranium Mine. All collected samples were properly marked and identified by their sampling locations using a Global Positioning System (GPS). Samples were acid digested using microwave oven according to U.S EPA 3052B protocols and analysed for arsenic (As), cadmium (Cd), copper (Cu), chromium (Cr), lead (Pb), mercury (Hg), nickel (Ni) and zinc (Zn) with Inductively Coupled Plasma – Optical Emission Spectrometry technique (ICP-OES). The concentration levels of heavy metals in soils were in the range of 4.1-155.5 mg/kg for As, 0.1-0.7 mg/kg for Cd, 13.4-119.1 mg/kg for Cu, 54.0-147.0 mg/kg for Cr, 0.02-1.36 mg/kg for Hg, 24.1-168.9 mg/kg for Ni, 5.5-82.5 mg/kg for Pb, and 12.5-641.0 mg/kg for Zn. Three sampled sites (KS7, KS8 and KS10) recorded high contamination levels by heavy metal compared with the relevant South African standard and other international standrads. The geo-accumulation index assessment revealed that the soils vary between uncontaminated to the extreme pollution soil category. The ecological risk factor (Er ) mean values of As, Cd, Cr, Pb and Zn revealed low ecological risk to soils, while values for Cu and Hg indicated moderate ecological risk. Ni values indicate a considerable ecological risk. The potential ecological risk index (RI) values of three sites (KS1, KS5, and KS9) indicated low ecological risk. RI values for KS3, KS6 and KS11showded that these sites posed moderate ecological risk. Considerable ecological risk was displayed by sites KS2, KS4 and KS8, while RI values of site KS7 and 10 displayed very high ecological risk. These results indicate that the anthropogenic mining activities have polluted the area with heavy metals. As a result a series of recommendation are forwarded in order to rehabilitate the quality of the soils affected.