The status of the Baynespruit bacteriological water quality is very alarming - E-coli concentrations have far exceeded the allowable limit of both local and international guidelines for more than a decade, namely 2000-2010. Concentrations of indicator bacteria have been recorded as high as 2419000 cfu/100 ml, whereas guideline levels of E-coli for recreational contact are about 130 cfu/100 ml. In this study, statistical analyses were carried out on data from two sampling points to clarify the seasonal changes and the variability of the pollution. Cross-correlation analyses showed that there was no significant correlation between E-coli concentrations and rainfall in the uMsunduzi catchment. There was also only a weak correlation between the two sampling points which suggests the existence of unregulated sources of pathogenic water pollution between the sampling locations that are independent of the effect that rainfall has on dilution and dispersion of pollution. The data indicates that the population living along the Baynespruit has about a 2% risk of contracting gastrointestinal illness as a result of the pollution in the stream. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

It is very unfortunate that despite laws that require adequate incorporation and integration of environmental concerns at all phases of the economic developmental projects in Zambia, the research findings of this dissertation show that they are not applied well. The dissertation consists of six chapters. The Introduction (Chapter One) gives a general overview of Zambia, its geographical position in relation to other African countries, its macro and micro economic policies and its economic needs for a sound transport infrastructure. It also gives a rationale for the Monze-Zimba road rehabilitation project. Chapter Two reviews and states existing policies, legal, strategies and the institutional framework for environmental management and protection in Zambia. It also states and identifies key institutions involved in administering the various environmental laws/regulations and briefly refers to applicable International Conventions. Chapter Three gives a descriptive overview of baseline information - particularly within the catchment area of the road - regarding the biophysical, socioeconomic and cultural environments. The baseline studies provide insights into the normal background environmental variability such that appropriate monitoring programmes can be designed. It is now abundantly and evidently clear that the despoiling of the environment has negative repercussions on the health and wellbeing, culture and economic opportunities of humans. Chapter Four, therefore, provides in-depth discussions of each of the major impacts identified, their nature and scale and appropriate practical measures for their mitigation. The measures are incorporated into an Environmental Management Plan. Chapter Five addresses the environmental monitoring of the impacts resulting from the activities of the road. The Conclusion (Chapter Six) gives substantiated opinions on the overall findings of the research. Recommendations are given to the government of Zambia and all stakeholders on the best ways that environmental issues should be handled at all levels of society. / Thesis (M.Sc.Eng.)-University of Durban-Westville, 2001.

Waste is commonly disposed in landfills, this result in the formation of leachate which needs to be treated to acceptable standards before being discharged to the environment. High concentrations of pollutants, particularly ammonia, in the landfill leachate are persistent even after the closure of the landfill and it requires ad hoc treatment. Treated leachate can still be characterized by high concentrations of nitrates, which exceeds the discharge standards. This phenomenon is observed in the Mariannhill landfill site in Durban, where leachate is nitrified in a Sequencing batch reactor and produces effluent with over 1000 mg/l (Trois et al, 2010a). Denitrification can be used to remove nitrate concentrations, this process occurs under anoxic conditions in the presence of an external carbon source. Denitrification treatment methods utilize chemicals such as methanol and ethanol as carbon sources, but the large scale application of these chemicals is often uneconomical. This research aims at identifying the cost effective treatment system for bio-denitrification that utilizes commercial garden refuse (CGR raw and lightly composted for 10 weeks “CGR 10”) as carbon sources. The feasibility checks for applying these substrates were based on the efficiency and kinetics of nitrate removal over a short and long-term period, thus providing the estimates for operational procedures. Initial characterization tests, batch and column tests were performed in the lab towards achieving the aim of this research. All batch tests achieved 100% of nitrate removal, but CGR raw was faster than CGR 10 with a time difference of 16% and 20% for batches at 100 and 500 mg/L, respectively. The significant difference in the kinetic removal efficiency was observed in batch tests at 2000 mg/L, where CGR raw was about 18 times faster than CGR 10 and about 2 times faster than that of CGR raw at 500 mg/L. Thus, the kinetics of nitrate removal in CGR raw at 2000 mg/L was suspected to be due to chemical reaction other than biological reaction. In the second set of batch tests the kinetics of nitrate removal for CGR raw was about 3 times that of CGR 10. The column tests, which were operated as continuous flow reactor did not achieve full denitrification due to high flow rate applied. First set of column tests (columns A) used previously used substrates to treat synthetic nitrate solution (500 and 2000 mg/L). Second set of column tests (columns B) used fresh substrates to treat pre-treated landfill leachate with nitrate concentration of about 2000 mg/L. CGR 10 achieved better removal efficiency than CGR raw when treating synthetic solution. Whereas, CGR raw achieved better nitrate removal when treating pre-treated landfill leachate. Decrease in flow rate improved the removal efficiency of the substrates. Dilution of nitrified leachate to about 500 mg/L could improve the efficiency of the substrates. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2011.

The amount of greenhouse gases (GHG) emitted due to waste management in the cities of developing countries is predicted to rise considerably in the near future; however, these countries have a series of problems in accounting and reporting these gases. This study investigated GHG emissions from the municipal waste sector in South Africa. In particular, the eThekwini Municipality is researched in detail and current emissions as well as further projections have been calculated. This research has to be placed in the wider context where developing countries (including South Africa) do not have binding emission reduction targets, but many of them publish different greenhouse gas emissions data which have been accounted and reported in different ways. Results from the first stages of this research showed that for South Africa, inventories at national and municipal level are the most important tools in the process of accounting and reporting greenhouse gases from waste. However, discrepancies in the methodology used are a concern. This is a challenging issue for developing countries, especially African ones, since higher accuracy methods are more data intensive. Therefore, the development of local emission factors for the different waste management processes is important as it encourages a common, unified approach. In the accounting of GHG from waste at municipal level, emission factors, based on a life cycle approach, are used with increased frequency. However, these factors have been calculated for many developed countries of the Northern Hemisphere and are generally lacking for developing countries. The second part of this research showed how such factors have been developed for waste processes used in this country. For the collection and transport of municipal waste in South Africa, the average diesel consumption is around 5 dm3 (litres) per tonne of wet waste and the associated GHG emissions are about 15 kg CO2 equivalents (CO2 e). Depending on the type of landfill, the GHG emissions from the landfilling of waste have been calculated to range from -145 to 1 016 kg CO2 e per tonne of wet waste, when taking into account carbon storage, and from 441 to 2 532 kg CO2 e per tonne of wet waste, when carbon storage is left out. The highest emission factor per unit of wet waste is for landfill sites without landfill gas collection and these are the dominant waste disposal facilities in South Africa. The emission factors developed for the different recyclables in the country showed savings varying from -290 kg CO2 e (glass) to – 19 111 kg CO2 e (metals - Al) per tonne of recyclable. They also illustrated that there is variability, with energy intensive materials like metals having higher GHG savings in South Africa as compared to other countries. This study also showed that composting of garden waste is a net GHG emitter, releasing 172 and 186 kg CO2 e per tonne of wet garden waste for aerated dome composting and turned windrow composting, respectively. By using the emission factors developed, the GHG emissions from municipal waste in the eThekwini Municipality were calculated and showed that for the year 2012 net savings of -161 780 tonnes CO2 e were achieved. This is mainly due to the landfill gas to electricity clean development mechanism (CDM) projects and due to recycling in the municipality. In the absence of landfill gas (LFG) collection and utilisation systems, which is typical for the majority of South African landfills, important GHG emission from the anaerobic degradation of waste are recorded. In the near future (year 2014) the closure of one of the three local landfill sites and the re-directioning of the majority of waste to another landfill sites which does not have LFG collection and utilisation, will cause an increase of GHG emissions to 294 670 tonnes CO2 e. An increase in recycling and the introduction of anaerobic digestion and composting has the potential to reduce these emissions as shown for the year 2020. However, only the introduction of a LFG to electricity system will result in the highest possible overall GHG savings from waste management in the municipality. In the absence of the Clean Development Mechanism and the associated financial arrangements, these systems have to be financed locally and might present a financial challenge to the municipality. Therefore, the second intervention which will make a difference by lowering GHG emissions from waste management would be to increase recycling in general and in particular the recycling of paper and metals. Since there is no direct competition for carbon, in addition to recycling, anaerobic digestion can be introduced and this combination will achieve increased savings in the future. If anaerobic digestion is not possible, composting in addition to recycling will also lead to savings, albeit not as high as with anaerobic digestion. The results presented in this study show that life cycle based GHG emission factors for waste and their use can support a unified approach to accounting of GHG and better decision-making for municipalities in the local context. They can give valuable input for the planning and development of future waste management strategies and they can help optimise current municipal solid waste management. / Ph.D. University of KwaZulu-Natal, Durban 2013.

The optimisation of the decision of when to replace water distribution mains is a complex task. There are numerous drivers in the decision making process (informed by financial data, performance data and water quality data) and hundreds of variables and performance indicators that can be considered when trying to reach an optimised decision. Most of the assets under consideration are buried and the internal and external pipe conditions are not easily assessable, forcing the Utility to rely on the available direct and indirect variables from which conclusions on the reliability of the mains are to be inferred. The cost of mains replacement is relatively low but the assessment cost, if carried out can be relatively high. The total value of a metropolitan distribution network typically runs into billions of rands but the impact of an individual pipe failure is generally low. The distribution network is comprised of many different pipe materials and components, of different pressure classes, made by different manufacturers, installed by numerous contractors with different skill levels under differing quality control regimens over many years. To add to this complexity, various parts of the network are operated at different static pressures and varying velocities. Some sections of the network are isolated more often than others and at times there can be large pressure surges that the network is subjected to by either the Utility or Consumer. These pressure surges are known to have a marked detrimental effect on the network. False markers also exist that can give rise to totally incorrect decisions and therefore performance data cannot be accepted at face value and needs to be scrutinised and cleansed to increase its reliability prior to being utilised in decision making process. This important step has been missed by much of the research carried out to date. In the Durban context, a further complication is caused by consumers tampering with the water mains and also not reporting leaks. This has a negative effect on the performance of the water main that can cause it to be flagged for replacement, but its replacement will not result in an increase in performance if the social issues are not resolved first. The aim of this research is to make recommendations on the methodology to be employed to improve network performance and thereby delay the point at which the water mains are to be replaced for as long as possible. These recommended activities will be carried out to remove false markers and improve upon the quality and reliability of the data available on the network performance. A further output is to make recommendations regarding the minimum data that can be reasonably collected and analysed in order to determine an optimised result. The recommendation of which mains should be targeted for replacement should result in the highest benefit for the utility as well as the consumers. By implication, this will result lowest long term capital and operational expenditure and thus the lowest long term tariffs charged to the consumers whilst complying with the water quality criteria and service level targets. / Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, Durban, 2012.

Thesis (MScEng)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Connections are a vitally important part of any structural framework. Thisstatement may seem obvious, yet it is surprisinghow often insufficient attention is given to the design of this essential aspect of steelwork projects. This thesis concentrates on developing a specification for designing steel connections with the main emphasis on the practical and economical design of typical connections. The design methods of the specification are developed according to the new South African design code which is currently in draft form, namely SANS10162:Code of Practice for the Structural Use of Steel: Part 1: Limit States Design of hot-rolled steelwork - 2002. An object-oriented framework and associated graphical user interface for designing the connections are developed and implemented. The primary objectives of the implemented framework are: • Being generic in the sensethat it allows for easy addition of additional connection types, • To implement the design paradigm of the South African code, without fixing specific parameter values programmatically in the implementation and • To build on an existing architecture that allows for structural analysis,structural steel member design and distributed collaboration in the design process. / AFRIKAANSE OPSOMMING: Verbindings vorm In uiters belangrike deel van enige staal struktuur. Alhoewel hierdie stelling dalk vanselfsprekend mag wees, is dit egter verbasend hoe selde voldoende aandag aan die ontwerp van hierdie essensiëleaspek van staalwerk projekte gegee word. Hierdie tesis konsentreer op die ontwikkeling van In spesifikasievir die ontwerp van staal verbindings met die oog op praktiese en ekonomiese ontwerp van tipiese verbindings. Hierdie ontwerpmetodes isgebasseer op die nuwe Suid Afrikaanse ontwerpkode wat tans in proef-vorm is, naamlik SANS 10162: Gebruikskode vir Stoa/bouwerk: Dee/I: Grenstoestandontwerp vir warmgewa/ste staa/werk - 2002. In Objek orienteerde raamwerk en In geassosieerde grafiese gebruikerskoppelvlak word ontwikkel en geimplimenteer. Die primêre mikpunte van hierdie geimplimenteerde raamwerk is: • Om generies te wees in die sin dat dit die byvoeging van addisionele verbinding tipes toelaat, • Om die paradigma van die Suid Afrikaanse kode te implimenteer sonder om enige waardes van spesifieke parameters programmaties vas te lê, en • Om dit op In bestaande argitektuur te bou wat strukturele analise, strukturele ontwerp en verspreide samewerking in die ontwerpproses toelaat.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2002. / 198 leaves double sided printed, preliminary pages i-xx and numberd pages 1-1-12-6.Includes bibliography. List of tables, figures and appendices and acronyms. Scanned with a HP Scanjet 8250 Scanner to pdf format (OCR). / ENGLISH ABSTRACT: In this study the numerical short wave model SWAN is evaluated for application to a selected coastal region in South Africa. The aim of this study was to evaluate the degree of accuracy with which SWAN can simulate prototype nearshore wave spectra and wave parameters (e.g. wave height, mean wave direction and mean wave period) for an Algoa Bay field case. Algoa Bay represents a typical deep, sheltered embayment on the South African south coast, which is exposed to high-energy swell. Sensitivity analyses on various wave-related processes were also done, with the aim of establishing the dominant physical processes and appropriate model setup for the Algoa Bay field case. With the dominant wave-related processes and appropriate model setup for the Algoa Bay field case established, selected final runs were performed to determine the degree of accuracy with which SWAN can simulate prototype conditions, by comparing its results with available field recordings. This study comprises a review of the SWAN evaluation work conducted to date by others, an overview of South African coastal conditions, and numerical model simulations. The model simulations, which represent the main focus of this study, were conducted for a selection of available offshore wave conditions (at 85 m water depth) observed during the Algoa Bay field case and were compared to available nearshore observations (at 17 m water depth). Environmental conditions of waves, wind and currents were included in these simulations. The study focuses on model application and sensitivity analysis, rather than model development, and includes evaluation of all relevant processes, without focussing on any specific model aspect. The results of this study show that SWAN simulations correlated well with observations at the nearshore station in Algoa Bay, both in wave spectral shape and its associated parameters. Dominant processes identified for the field case were depth-induced refraction, bottom friction and directional spreading. This finding agrees with those of previous evaluations of SWAN and previous modelling experience by others. It is shown that high-energy swell is relatively more sensitive to the choices of model setup than wind sea. Based on the simulation results of high-energy swell, it is concluded that the calculation of depth-induced refraction in SWAN seem to contain a degree of inaccuracy. It is also concluded that the findings of this study could be used as a guideline to SWAN modelling studies along the South African south coast. / AFRIKAANSE OPSOMMING: In hierdie studie word die toepassingsmoontlikhede van die numeriese kortgolf model SWAN vir 'n geselekteerde gedeelde van die Suid-Afrikaanse kuslyn beoordeel. Die doel van hierdie studie is om die vlak van akkuraatheid waarmee SWAN prototipe golfspektra en golfparameters (bv. golfhoogte, gemiddelde golfrigting en gemiddelde golfperiode) in die vlakwater kan simuleer te beoordeel, vir 'n Algoabaai gevallestudie. Algoabaai verteenwoordig 'n tipiese diep, beskermde baai aan die Suid-Afrikaanse kuslyn, wat blootgestel is aan hoe-energie deining. Sensitiwiteitstoetse is ook uitgevoer vir verskillende golfprosesse, met die doel om die dominante fisiese prosesse en gepaste modelopstelling vir die Algoabaai gevallestudie te vind. Nadat die dominante golfprosesse geidentifiseer is, en die toepaslike modelopstelling gevind is, is finale simulasies uitgevoer vir geselekteerde gevalle om die mate van akkuraatheid te bepaal waarmee SWAN prototipe kondisies kan simuleer, deur simulasie resultate met beskikbare veldmetings te vergelyk. Hierdie studie bestaan uit 'n samevatting van die evaluasiewerk verrig op SWAN deur andere, 'n samevatting van golf-, wind- en stroomtoestande aan die Suid-Afrikaanse kus en numeriese modelsimulasies. Die modelsimulasies, wat die hooffokus van hierdie studie is, is uitgevoer vir 'n seleksie van beskikbare diepsee golftoestande (in 85 m waterdiepte) uit die Algoabaai gevallestudie en is vergelyk met beskikbare vlakwater metings (in 17 m waterdiepte). Omgewingstoestande van golwe, wind en seestrome is ingesluit in hierdie simulasies. Die studie fokus op modeltoepassing en sensitiwiteits-analise, eerder as modelontwikkeling, en behels die beoordeeling van alle toepaslike modelprosesse, sonder om te fokus op enige spesifieke model aspek. Die resultate van hierdie studie toon aan dat die SWAN simulasies goed korrileer met vlakwater meetings in Algoabaai, vir beide golfspektraalvorm en verwante golfparameters. Bodemrefraksie, bodemwrywing en rigtingsspreiding is geidentifiseer as dominante modelprosesse. Hierdie resultaat kom ooreen met bevindings van vroeere beoordeling van SWAN en modelleer-ervaring deur andere. Dit word aangetoon dat hoe-energie deining relatief meer sensitief is vir modelopstelling as wind-see. Gebasseer op resultate van simulasie met hoe-energie deining, word die gevolgtrekking gemaak dat die berekening van bodemrefraksie in SWAN 'n mate van onakkuraatheid toon. Die gevolgtrekking word ook gemaak dat die resultate van hierdie studie as riglyn gebruik kan word vir modelleerwerk met SWAN aan die Suid-Afrikaanse suidkus.

Thesis (MScEng (Civil Engineering))--Stellenbosch University, 2008. / Doubly symmetric I-section columns are often utilised in portal frame construction. The sheeting (or cladding) is carried by sheeting rails connected to the outer flange of these columns. Although it is common practice to include the sheeting rails in the longitudinal bracing system, by connecting the sheeting rail to the cross-bracing, designers must be wary because the connection between column and sheeting rail will not prevent twisting of the columns cross-section. It has been shown ([11], [12], [17]), that by including this eccentric restraint into the bracing of the column, that a torsional-flexural buckling mode of failure can occur when the column is subjected to axial load only. It was seen that this phenomenon is provided for in BS 5950 [18], but is not present in many other design codes of practice, in spite of this phenomenon being relatively well known. In some cases the compression resistance of a column can be significantly reduced when compared to that of a flexural buckled configuration. Previous work performed by Helwig and Yura [15] proposed specific column to sheeting rail connections which would allow for the sheeting rails to be used as elastic torsional braces and effectively rigid lateral braces. However, it is the objective of this investigation to determine if it is possible to include the eccentric sheeting rails into the bracing system, even when using a relatively simple cleat connection with only two bolts onto the sheeting rail. The objective of the research was investigated by conducting experimental tests coupled with a series of detailed finite element analyses. The purpose of the experimental set-up was to investigate the behaviour of a column laterally supported on one flange by a continuous sheeting rail and to compare it to the behaviour of a column laterally supported on both flanges by means of fly-braces (“kneebraces”). The behaviour of the columns, as determined by the experimental tests, was validated by the finite element analyses. The evident conclusion that can be drawn is that, for the case of a continuous sheeting rail, connected to column simply by two bolts and a cleat, that sufficient torsional restraint is provided to the column to prevent torsional-flexural buckling from being critical. This result is helpful, as it means that the buckling capacity of a column can be increased four-fold by enforcing the second flexural buckling mode instead of the first mode through utilising a continuous sheeting rail connected to a cross-bracing system as longitudinal bracing on the columns. This can be achieved without the need to provide any specific detailing to the column to sheeting rail connection. It is however, recommended that further experimental work be conducted on varying lengths of column in order to further validate the results of this work.

Thesis (MScEng)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Fibre reinforced concrete (FRC) transforms concrete from a characteristically brittle material to one with a post-crack tensile residual capacity. Its application in industry has varied over the past of which the tensile properties have generally been used in the form of crack mitigation. More recently, the introduction of steel fibres has broadened this scope to structural applications in which the resisting tensile stresses that develop within a steel FRC (SFRC) element can be rather significant. This thesis reviews the existing practices and design models associated with SFRC and the suitability of its implementation as the sole form of reinforcement in in-situ cast flat slab systems. As a material SFRC is dependent on a number of factors which include the fibre type and volume, fibre distributions, element size, as well as the support and applied load conditions. Thus, its performance can be considered rather variable in comparison to conventional concrete should the incorrect practices be implemented. In order to adequately define the material characteristics, it is necessary to use test procedures that accurately reflect on the intended structural application. As a result a number of test procedures have been developed. In addition to this, the post-crack material performance is associated with a non-linear behaviour. This attribute makes the design of structural SFRC elements rather difficult. In an attempt to simplify this, existing design models define stress-strain or stress-crack width relations in which assumptions are made regarding the cross-sectional stress distribution at specified load states. This thesis takes on two parts in defining the suitability of SFRC as the sole form of reinforcement in flat slab systems. The first is a theoretical investigation regarding the micro and macro scale material performance of SFRC, the practices that exist in defining the material properties and its application in structural systems (particularly suspended slab systems), and a breakdown of the existing design models applicable to strain softening deflection hardening SFRC materials. The second part is an experimental program in which the fresh state and hardened state material properties of specified SFRC mix designs defined through flow and beam testing respectively. These properties are then implemented in the design and construction of full scale flexural and punching shear test slabs in an attempt to verify the theory applied. The investigation reveals that the use of SFRC significantly improves the ductility of concrete systems in the post-crack state through fibre crack bridging. This ductility can result in deflection hardening of flat slab systems in which the redistribution of stresses increases the load carrying capacity once cracking has taken place. However, the performance of large scale test specimens is significantly influenced by the construction practices implemented in which the material variability increases as a result of non-uniform fibre distributions. The results indicate that the load prediction models applied have potential to adequately predict the ultimate failure loads of SFRC flat slab systems but however cannot account for possible non-uniform fibre distributions which could result in premature failure of the system. / AFRIKAANSE OPSOMMING: Vesel versterkte beton (VVB) verander beton van die kenmerkende uiters bros material na ‘n material met ‘n residuele post-kraak trekkapasiteit. Die toepassing daarvan in die bedryf het in die verlede gewissel en die trek eienskappe is oor die algemeen gebruik vir kraak vermindering. Meer onlangs het die bekenstelling van staal vesel hierdie omvang verbreed na die strukturele toepassings waar trekspannings wat ‘n VVB element kan weerstaan noemenswaardig kan wees. Hierdie tesis ondersoek bestaande praktyke en ontwerpmodelle met die oog op staalvesel versterkte beton (SVVB) en die geskiktheid van die implementering daarvan as die enigste vorm van bekisting in in-situ gegiete plat blad stelsels. As ‘n materiaal, is SVVB afhanklik van ‘n aantal faktore wat die tipe vesel en volume, vesel verspreiding, element grootte, sowel as die randvoorwaardes tipe aangewende las insluit. As gevolg hiervan, kan die gedrag van SVVB, wat korrek geïmplimenteer word, as redelik varieerbaar beskou word wanneer dit met konvensionele beton vergelyk word. Ten einde die materiaaleienskappe voldoende te definieer, is dit noodsaaklik dat prosedures wat die strukturele toepassing akuraat voorstel, getoets word en daarom is ‘n aantal toets prosedures ontwikkel. Verder het die post-kraak materiaalgedrag ‘n nie-lineêre verband wat struktuurontwerp met SVVB redelik moeilik maak. Om dit te vereenvoudig, definieer bestaande ontwerpmodelle spanning-vervorming of spanning-kraakwydte verhoudings waarin aannames gemaak word ten opsigte van die spanningsverdeling oor ‘n snit, gegewe sekere lastoestande. Hierdie studie bestaan uit twee dele wat die geskiktheid van SVVB as die enigste vorm van bikisting in plat blad stelsels definieer. Die eerste deel bestaan uit ‘n teoretiese ondersoek wat handel oor die mikro- en makro-skaal materiaalgedrag van SVVB, die praktyke wat bestaan om die materiaaleienskappe en toepassing in strukturele sisteme (spesifiek opgelegde blad stelsels) te definieer, en ‘n uiteensetting van die bestaande ontwerpmodelle wat van toepassing is vir defleksie as gevolg van vervormingsversagting wat SVVB material verhard. Die tweede deel bestaan uit ‘n eksperimentele program waarin die materiaaleienskappe van gespesifiseerde SVVB meng-ontwerpe in die vars toestand en in die verharde toestand gedefinieer word deur middel van vloei- en balktoetse onderskeidelik. Hierdie eienskappe word dan toegepas vir die ontwerp en konstruksie van volskaalse buig- en ponsskuif toetsblaaie ten einde die modelle en teorie wat toegepas is, te bevestig. Die ondersoek toon dat die gebruik van SVVB die duktiliteit van beton sisteme noemenswaardig verbeter in die post-kraak toestand deur kraak oorbrugging. Hierdie duktiliteit kan defleksie verharding van plat blad stelsels veroorsaak waarin die herverdeling van spannings, nadat kraking plaasgevind het, die lasdraende kapasiteit verhoog. Die gedrag van die grootskaalse toetsmonsters word egter noemenswaardig beïnvloed deur die konstruksiemetodes wat geïmplementeer word waarin die materialveranderlikheid toeneem as ‘n gevolg van nie-uniforme vesel verdelings. Die resultate dui daarop dat die modelle wat toegepas is om die laste te voorspel, die potensiaal het om die grens falingslas van SVVB plat blad stelsel voldoende te voorspel, maar neem nie moontlike nie-uniforme veselverdelings wat kan lei tot vroeë faling van die stelsel in ag nie.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2006. / In many part of the world, but especially in Africa, land degradation leads to severe soil erosion and high sediment yields. Mathematical models and empirical methods can be used to simulate the sediment yields. In many cases spatial and temporal data are however limited in the large catchments often found in Africa. A model should be able to simulate the long-term hydrology and sediment yields for sub-catchments and should be physically based as far as possible. In this thesis several models were evaluated and the agrohydrological model of the University of Kwa- Zulu-Natal (ACRU) was applied on two large catchments with limited data in Kenya. The key aim of the thesis was to assess the applicability of the ACRU modelling system for sediment yield prediction in large catchments under conditions of limited data availability. Two catchments in Kenya which drain into Lake Victoria were selected for this research: Nyando (3562 km2) and Nzoia River (13692 km2). Lake Victoria, with a surface area of 68000 km2 and an adjoining catchment of around 184200 km2, is the second largest fresh water lake in the world and the largest in the tropics. The Lake Victoria Basin area is increasingly being used for domestic, agricultural and industrial purposes by the three riparian countries Kenya, Tanzania and Uganda. About 21 million people (year 2000) rely primarily on subsistence agricultural and pastoral production for their livelihoods. But pervasive poverty has hindered sustainable use of the land resources and there has already been considerable land degradation. There has also been expansion of the increasing on-site erosion (overland flow) and reducing buffering capacity of the natural vegetation in wetlands and in the riparian zones (Hansen, Walsh, 2000). A regional assessment identified the Nyando River Basin and Nzoia River Basin as major sources of sediment flow into Lake Victoria on the Kenyan side of the Lake. Accelerated run off sheet erosion over much of the Nyando catchment area has led to severe rill, gully and stream bank erosion in lower parts of the river basin (Swallow, 2000). The ACRU model is a hydrological model using daily time steps with the Modified Universal Soil Loss Equation (MUSLE, Williams, 1975) module to simulate soil erosion. The MUSLE sediment yield module uses factors that characterize physical conditions on the surface of a catchment as input information. Data required for the model include: sub-catchment daily rainfall, historical flow records, general catchment topographical information, meteorological information, land use and cover, soil characteristics, sediment yield data, etc. The model used daily time steps for a 55 years record for the period 1950 to 2004. During calibration it was found that the sediment yield is overestimated which was expected since the model is a soil erosion model (based on MUSLE). The model was calibrated in each catchment against observed sediment load data, but this data were limited. Verification of the model was carried out by using satellite images and independent sediment load data when available. Scenario analysis was carried out by changing land use in the model to investigate how soil erosion could be reduced. Grassland to replace subsistence farming was found most effective, but irrigated sugarcane was also investigated. The model was found to be very effective in indicating which sub-catchments contribute most of the sediment yield. Under limiting data conditions it was found that it is very important to calibrate the model against field data. The most sensitive parameters affecting the sediment yield were found to be: a) Hydrological: • Daily rainfall spatial distribution of rain gauge • Time of concentration • Mean annual precipitation • Minimum and maximum temperature • Monthly evaporation b) Soil and catchment characteristics: • Number of sub-catchments making up catchment in model • Catchment slope and slope length, steepness factor • Land cover • Crop coefficient • Soil texture class and depths • Soil erodibility factor