Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2008. / Thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Civil Engineering at the University of Stellenbosch. / ENGLISH ABSTRACT: The logical scheduling of activities in an engineering project currently relies heavily on the experience and intuition of the persons responsible for the schedule. In large projects the complexity of the schedule far exceeds the capacity of human intuition, and systematic techniques are required to compute a consistent sequence of activities. In this study a simple model of the engineering process is described. Based on certain specified relationships between components of the model, a consistent sequence of activities is determined in the form of a logical step schedule. The problem of resource constraints receives special attention. Engineering projects are often executed with limited resources and determining the impact of such restrictions on the logical step schedule is important. This study investigates activityshifting strategies to find a near-optimal sequence of activities that guarantees consistent evolution of deliverables while resolving resource conflicts within the context of logical step schedules. / AFRIKAANSE OPSOMMING: Die logiese skedulering van aktiwiteite in ‘n ingenieursprojek steun swaar op die ondervinding en intuisie van die persone wat verantwoordelik is vir die skedule. In groot projekte is die kompleksiteit van die skedule veel hoër as die kapasiteit van die menslike intuisie, en sistematiese tegnieke word benodig om ‘n konsekwente volgorde van aktiwiteite te bereken. In hierdie studie word ‘n eenvoudige model van die ingenieursproses beskryf. Gebasseer op sommige relasies tussen komponente van die model, kan ‘n konsekwente volgorde van aktiwiteite bepaal word in die vorm van ‘n logiese stap-skedule. Die probleem van beperkte hulpbronne ontvang spesiale aandag. Ingenieursprojekte word dikwels uitgevoer met beperkte hulpbronne en dit is belangrik om die impak daarvan op die logiese stap-skedule te bepaal. Die studie ondersoek die gebruik van aktiwiteit-skuiwende strategieë om ‘n nabyoptimale volgorde van aktiwiteite te vind wat konsekwente ontwikkeling van die projekprodukte waarborg, terwyl hulpbron konflikte opgelos word binne die konteks van ‘n logiese stap-skedule.

Thesis (MEng)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The processes of monitoring, modelling and managing the water quality of a catchmerit system including all its unique complexities and interrelationships requires an innovative tool or set of tools to help water managers with their decision making. Numerous methods and tools have been developed to analyse and model the real world. However, many of these tools require a fair degree of technical expertise and training to operate correctly and their output may have to be translated or converted to meaningful information for decision-making using a further set of analytical and graphical display tools. A more appropriate technique for management would be to combine all these functions into a single system. The objective of this research was to develop one such tool, an integrated water quality information system (WQIS). A review of the literature revealed that there has been extensive research and development of tools for the management of individual aspects of water resource distribution, augmentation and quality. However, these tools have rarely been integrated into a comprehensive information system offering decision support to a wide variety of river users and managers. Many of the literature sources also noted that a process of interactive development and integration (i.e. including the intended users in the decision of which components to include, the interface design and the graphical display and output) was vital to ensuring the information system becomes an integral part of the users routine work and decision-making. The WQIS was developed using the recommendations from numerous knowledgeable persons in response to questionnaires, interviews and a prototype demonstration. It includes the results of hydrodynamic river and reservoir simulations and the ability to perform operational river scenario testing. However, the development process is continual and always evolving based on the current or local requirements of water managers. These further developments and research needs are discussed in more detail in the conclusion. / AFRIKAANSE OPSOMMING: Die proses om die waterkwaliteit van 'n opvanggebied, met al die unieke kompleksiteite en onderlinge verhoudings van so 'n stelsel te monitor, modelleer en bestuur, vereis 'n innoverende instrument om waterbestuurders te ondersteun in hul besluitnemings. Talle instrumente en metodes vir die ontleding en modellering van die werklikheid is reeds ontwikkel. Die gebruik van hierdie instrumente vereis gewoonlik 'n redelike mate van tegniese kundigheid en opleiding. Dit mag verder nodig wees om die uitvoer van sulke instrumente te vertaal en/of om te skakel na betekenisvolle inligting vir besluitneming deur die gebruik van bykomende analitiese en grafiese vertoon instrumente. 'n Meer toepaslike bestuurstegniek sou wees om al die funksies in 'n enkele stelsel te kombineer. Die doel van hierdie navorsing was om een so 'n instrument, naamlik 'n geïntegreerde waterkwaliteit inligtingstelsel (WQIS), te ontwikkel. 'n Hersiening van bestaande literatuur het getoon dat daar omvattende navorsing en ontwikkeling van instrumente gedoen is vir die bestuur van individuele aspekte van waterbronverspreiding, waterbronaanvulling en waterkwaliteit. Integrasie van hierdie instrumente, in 'n uitgebreide stelsel wat besluitnemingsondersteuning aan 'n verskeidenheid riviergebruikers en bestuurders bied, kom egter selde voor. Verskeie literatuurbronne het ook aangedui dat 'n proses van interaktiewe ontwikkeling en integrasie (m.a.w. in agname van die voorgenome gebruikers se behoeftes in die kense van komponente, die gebruiker raakvlak ontwerp en grafiese vertoon instrumente en uitvoer) noodsaaklik is om te verseker dat die inigtingstelsel 'n integrale deel word van die gebruiker se daaglikse roetine en besluitnemingsproses. Die WQIS is ontwikkel deur gebruikmaking van die insette en aanbevelings van verskeie kenners in reaksie op vraelyste, onderhoude en 'n demonstrasie van 'n prototype. Dit sluit in die resultate van hidro-dinamiese rivier en dam simulasies en die vermoë om operasionele rivier scenario ontledings uit te voer. Die ontwikkeling is egter 'n deurlopende proses, gebaseer op huidige of plaaslike behoeftes van waterbestuurders. Hierdie verdere ontwikkelings- en navorsingsbehoeftes word meer breedvoerig in die gevolgtrekkings bespreek.

Thesis (MEng)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Peak mornmg traffic-flow data were obtained from video footage of three representative freeway sections on the Nl and N2 westbound towards Cape Town. Flow, speed, and density measurements were made from the footage with the aid of a stopwatch. Many researchers (2-12) have originated and developed models to describe the relationships between traffic flow characteristics (speed, flow, and density) on freeways. In this report, a number of these models have been investigated with data obtained from South African freeways. The ability of each model to predict flow parameters over the entire range of data was evaluated with the aid of statistical methods. The tests were performed by regressing average speed vs. average density. Flow-density and speed-flow relationships were derived through application of the steady-state equation (2.6). In each case, a final model was chosen through visual inspection that consisted of two separate curves, one for the uncongested flow regime and one for the congested flow regime. Furthermore, speed-flow relationships were examined for individual lanes and compared to relationships established for average lanes. The models were also compared to models obtained from overseas studies (1,16,19) as well as from studies done locally (17). A secondary objective of this study is to investigate the performance of existing freeway facilities through application of the relevant models to the traffic-flow data of a particular facility. The current peak-morning performance of the N2 freeway section is investigated in terms of travel-time and travel cost. The particular study section consists of three lanes, the right hand lane being an HOY lane dedicated to taxis and buses. Different hypothetical cases are investigated. The first hypothetical case is an investigation into the traffic situation on the freeway section without the influence of the HOY lane. The second hypothetical case investigates the traffic situation on the section with perfect operation of the HOY lane. The current performance of the N2 section is compared to the performance of each of the hypothetical cases. / AFRIKAANSE OPSOMMING: Oggend-spits verkeersvloei data is verkry vanaf drie verteenwoordigende seksies op die Nl en N2 deurpaaie naby Kaapstad met die gebruik van 'n video kamera. Vloei, spoed, end digtheid opnames is gemaak met behulp van 'n stophorlosie. Verskeie navorsers (2-12) het modelle gepostuleer en ontwikkelom die verhoudings tussen verkeersvloei eienskappe (spoed, volume, en digtheid) op deurpaaie te beskryf. In hierdie verslag word 'n aantal van hierdie modelle ondersoek met data wat verkry is van Suid-Afrikaanse deurpaaie. Die vermoë van elke model om vloei eienskappe oor die hele bestek van die data te voorspel is geëvalueer met behulp van statistiese metodes. Statistiese toetse behels 'n regressie analise van gemiddelde spoed teenoor gemiddelde digtheid. Volume-digtheid en spoed-volume verwantskappe is direk afgelei vanaf Vergelyking 2.6. Vir elke geval is 'n finale model m.b.v. visuele inspeksie gekies wat bestaan het uit twee afsonderlike kurwes, een kurwe vir die vryvloei regime en 'n ander kurwe vir hoë-digtheid toestande. Verder word spoedvolume verwantskappe vir afsonderlike deurpad-lane ondersoek en vergelyk met verwantskappe wat verkry is vir gemiddelde lane. Die modelle word ook vergelyk met modelle wat verkry is vanaf oorsese studies (1,16,19), sowel as met modelle wat plaaslik verkry is (17). 'n Sekondêre doel van hierdie studie is om die prestasie van bestaande deurpadfasiliteite te ondersoek deur die verskillende modelle aan te wend tot die verkeersvloei data van 'n betrokke fasiliteit. Die prestasie van die N2 deurpad seksie gedurende oggend-spits verkeer is ondersoek in terme van reistyd en ryskoste. Die betrokke seksie bestaan uit drie lane, waarvan die regter laan gereserveer is vir busse en taxis. Verskeie hipoteses is ook ondersoek. Die eerste hipotese is 'n ondersoek na die verkeers-vloei kondisie op die seksie sonder die invloed van die bus- en taxi-laan. Die tweede hipotese ondersoek die seksie met perfekte werking van die bus- en taxilaan. Die huidige prestasie van die N2 seksie is vergelyk met die prestasie van elk van die hipoteses.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The scour process of unlined spillways is an important research topic of value in engineering practice. In South Africa numerous unlined spillway dams have experienced severe erosion. This led, in some cases, to the costly concrete lining of spillways for erosion protection. On the other hand, the erosion of unlined spillways can lead to damage to, and even failure of dams and consequently can affect public safety, properties, infrastructure and the environment. In this regard, methods to predict erosion of unlined spillways are therefore needed as tools in the risk management and design of existing unlined spillways as well as future spillway structures. The prediction of the rock scouring process is challenging and empirical formulas have been established to predict incipient conditions for scour. These empirical methods however do not predict the rate of scour or the ultimate equilibrium rock scour. The key objective in this study was to investigate the applicability of a non-cohesive two-dimensional (2D) sediment transport hydrodynamic mathematical model to simulate unlined spillway scour. A physical model flume test was set up to simulate rock scour represented by uniformly sized polyethylene cubes. The flume slope and discharge were varied in the different test scenarios. The 2D mathematical model correctly predicted the extent and location of scour as observed in the laboratory tests. Temporal changes in the scour formation were also predicted with reliability. This was achieved by only calibrating the hydraulic roughness of the 2D model, and by specifying the ”rock ” particle settling velocity and material density. The simulation results were satisfactory, providing an accurate and detailed erosion prediction. From this, the mathematical modelling was validated by using a field case study. The results obtained with the mathematical model were promising for non-cohesive cases and could be applied to field prototype cases if the rock joint structure is known. This would typically apply in fault zones, where the joints would give an idea of the rock size to be used in the mathematical model. In general, where jointed rock is more massive and acts ”cohesive ”, rock parameters describing critical scour conditions for the rock in terms of stream power are required to be built into the mathematical models. / AFRIKAANSE OPSOMMING: Die uitskuringsproses van onbelynde oorlope is ’n belangrike navorsingsonderwerp in die ingenieurspraktyk. In Suid-Afrika word ernstige erosie in baie onbelynde oorlope van damme ondervind. In sommige gevalle het dit gelei tot die duur belyning van oorlope met beton, om die oorlope te beskerm. Aan die anderkant kan die erosie van onbelynde oorlope lei tot groot skade en selfs tot die faling van ’n dam. Dit kan weer lei tot skade aan eiendom, infrastruktuur en die omgewing, en die publiek in die gevaar stel. Daarom is dit nodig dat daar besin word oor metodes om erosie in onbelynde oorlope te voorspel, sodat die risiko bestuur kan word en om te sorg vir die beter ontwerp van onbelynde oorlope in die toekoms. Dit is moeilik om die uitskuringsproses te voorspel, maar empiriese formules is bestaan om die aanvang van uitskuring te voorspel. Hierdie empiriese metodes voorspel egter nie die snelheid waarteen die uitskuring sal plaasvind of die uiteindelike mate waartoe dit sal gebeur nie. Die hoofdoelwit van hierdie studie was om die toepasbaarheid van ’n nie- kohesie, twee-dimensionele (2D) hidrodinamiese wiskundige model te ondersoek, om sodoende die uitskuring van onbelynde oorlope te simuleer. ’n Fisiese model om die uitskuring van rots te simuleer is ook gebou. Die rots is deur polietileen blokkies van dieselfde grootte gemodelleer. Verskillende kanaalhellings en deurstromings is in verskillende toetse gebruik. Die 2D wiskundige model het volgens die waarnemings in laboratorium toetse, die mate en ligging van die uitskuring korrek voorspel. Veranderinge wat met verloop van tyd in die uitskuring formasie plaasgevind het, is ook betroubaar voorspel. Dit is gedoen deur die hidrouliese ruheid van die 2D model te kalibreer en deur te spesifiseer hoe vinnig die ”rots ” deeljies afsak en wat die digtheid van die materiaal is. Die uitslag van die simulasie was bevredigend en het die erosie akkuraat en in detail voorspel. Die wiskundige modellering is gevalideer deur middel van ’n gevallestudie. Die uitslae wat met die wiskundige model verkry is, is belowend, en geld vir nie-kohesie gevalle. Dit kan op prototipe gevalle in die veld toegepas word as die rots se naatstruktuur bekend is. Dit kan toegepas word in foutsones waar die nate ’n aanduiding sal gee van die grootte van ”rotse ” wat in die wiskundige model gebruik moet word. Maar as die rots baie groot is en die kohesie goed is, is dit nodig om meer parameters betreffende uitskuringstoestande gekoppel aan stroomdrywing, in die wiskundige model te gebruik.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The primary aim of this study was to evaluate, calibrate and verify the SDF run-off coefficients at a quaternary catchment level in the C5 secondary drainage region (SDF basin 9) and other selected SDF basins in South Africa by establishing the catchment parameters and SDF/probability distribution-ratios. The probability distribution-ratios were based on the comparison between the flood peaks estimated by the SDF method and statistical analyses of observed flow data. These quaternary run-off coefficients were then compared with the existing regional SDF run-off coefficients, whilst the run-off coefficient adjustment factors as proposed by Van Bladeren (2005) were also evaluated. It was evident from this study that the calibrated run-off coefficients obtained are spread around those of Alexander (2003), but were generally lower in magnitude. The adjusted run-off coefficients (Van Bladeren, 2005) had a tendency to decrease in magnitude with increasing recurrence interval, whilst some of the adjusted run-off coefficients exceeded unity. The extent to which the original SDF method overestimated the magnitude and frequency of flood peaks varied form basin to basin, with the SDF/probability distribution-ratios the highest in the Highveld and southern coastal regions with summer convective precipitation. In these regions the flood peak-ratios were occasionally different by up to a factor of 3 or even more. The southern coastal regions with winter orographic/frontal precipitation demonstrated the best flood peak-ratios, varying from 0.78 to 1.63. The adjusted SDF method results (Van Bladeren, 2005) were only better in 26% of all the basins under consideration when compared to those estimated by the original SDF method. On average, the adjusted SDF/probability distribution-ratios varied between 0.30 and 6.58, which is unacceptable. The calibrated version of the SDF method proved to be the most accurate in all the basins under consideration. On average, the calibrated SDF/probability distribution-ratios varied between 0.85 and 1.15, whilst at some basins and individual return periods, less accurate results were evident. Verification tests were conducted in catchments not considered during the calibration process with a view to establish whether the calibrated run-off coefficients are predictable and to confirm that the method is reliable. The verification results showed that the calibrated/verified SDF method is the most accurate and similar trends were evident in all the basins under consideration. On average, the verified SDF/probability distribution-ratios varied between 0.82 and 1.19, except in SDF basins 6 and 21 where the 5 to 20-year return period flood peaks were overestimated by 41% and 56% respectively, which is still conservative. The secondary aim of this study was to develop a customised, user-friendly Design Flood Estimation Tool (DFET) in a Microsoft Office Excel/Visual Basic for Applications environment in order to assess the use and applicability of the various design flood estimation methods. The developed DFET will provide designers with a software tool for the rapid investigation and evaluation of alternative design flood estimation methods either at a regional or site specific scale. The focus user group of the application will comprises of engineering technicians, engineering technologist and engineers employed at civil engineering consultants, not necessarily specialists in the field of flood hydrology. The DFET processed all the catchment, meteorological (precipitation) and hydrological (observed flows) data used as input for the various design flood estimation methods. / AFRIKAANSE OPSOMMING: Die primêre doelwit van die studie was om die SDF-afloopkoëffisiënte op ‘n kwartinêre opvangsgebiedvlak in die C5-sekondêre dreineringsgebied (SDFopvangsgebied 9) en ander gekose SDF-opvangsgebiede in Suid-Afrika te evalueer, te kalibreer en te verifieer deur die opvangsgebiedparameters en SDF/waarskynlikheidsverspreiding-verhoudings vas te stel. Dié waarskynlikheidsverspreiding-verhoudings was gebaseer op die vergelyking tussen die vloedpieke soos beraam deur die SDF-metode en statistiese analises van waargenome vloeidata. Dié kwartinêre afloopkoëffisiënte is met die bestaande streeksgebonde SDF-afloopkoëffisiënte vergelyk, terwyl die afloopkoëffisiënt-aanpassingsfaktore soos voorgestel deur Van Bladeren (2005) ook geëvalueer is. Dit het duidelik uit die studie geblyk dat die gekalibreerde afloopkoëffisiënte verspreid rondom die van Alexander (2003) is, maar in die algemeen laer in omvang. Die aangepaste afloopkoëffisiënte (Van Bladeren, 2005) was geneig om af te neem in grootte met ‘n toename in die herhalingsperiode, terwyl sommige afloopkoëffisiënte ‘n waarde van 1 oorskry het. Die omvang waartoe die oorspronklike SDF metode die grootte en herhaalperiode van vloedpieke oorskat het, wissel van opvangsgebied tot opvangsgebied, met die SDF/waarskynlikheidsverspreiding-verhoudings die hoogste in die Hoëveld en suidelike kusstreke gekenmerk deur konveksie-somerreënval. In hierdie streke het die vloedpiekverhoudings gereeld verskil tot en met ‘n faktor van 3 of selfs meer. Die suidelike kusstreke met kenmerkende ortografiese/frontale winterreënval het oor die beste vloedpiekverhoudings beskik wat gewissel het tussen 0.78 en 1.63. Die resultate van die aangepaste SDF-metode (Van Bladeren, 2005) was slegs in 26% van al die opvangsgebiede beter as die beramings van die oorspronklike SDF-metode. Die aangepaste SDF/waarskynlikheidsverspreiding-verhoudings het, met verwysing na gemiddeldes, tussen 0.30 en 6.58 gewissel, wat onaanvaarbaar is. Die gekalibreerde weergawe van die SDF-metode was die mees akkurate metode in al die opvangsgebiede van belang. Die gekalibreerde SDF/waarskynlikheidsverspreiding-verhoudings het, met verwysing na gemiddeldes, tussen 0.85 en 1.15 gewissel, terwyl die resultate van sommige opvangsgebiede en individuele herhalingsperiodes minder akkuraat was. Verifikasietoetse is uitgevoer in die opvangsgebiede wat nie tydens die kalibrasieproses gebruik was nie om vas te stel of die gekalibreerde afloopkoëffisiënte voorspelbaar is en om te bevestig dat die metode betroubaar is. Die verifikasieresultate het getoon dat die gekalibreerde/geverifieerde SDFmetode die mees akkurate metode is en dat soortgelyke tendense duidelik was in al die relevante opvangsgebiede. Die geverifieerde SDF/waarskynlikheidsverspreiding-verhoudings het, met verwysing na gemiddeldes, tussen 0.82 en 1.19 gewissel, behalwe in SDF-opvangsgebiede 6 en 21 waar die 5- en 20-jaar herhalingsperiode-vloedpieke onderskeidelik met 41% en 56% oorskat is, wat steeds konserwatief is. Die sekondêre doelwit van die studie was om ‘n gebruikersvriendelike “Design Flood Estimation Tool” (DFET) in ‘n Microsoft Office Excel/Visual Basic for Applications omgewing te ontwikkel om die gebruik en toepaslikheid van die verskeie ontwerpvloedberamingsmetodes te bepaal. Die DFET sal ontwerpers voorsien van ‘n sagtewareprogram om alternatiewe ontwerpvloedberamingsmetodes op streek- of plaaslike skaal te ondersoek en te evalueer. Die fokus-gebruikersgroep vir die toepassing van die program sal bestaan uit ingenieurstegnici, ingenieurstegnoloë en ingenieurs werksaam by raadgewende siviele ingenieurs, nie noodwendig vakkundiges in die veld van hidrologie nie. Die DFET was gebruik om al die opvangsgebied-, meteorologiese (reënval) en hidrologiese (waargenome vloeie) data vir die verskeie ontwerpvloedberamingsmetodes te verwerk.

Thesis (MScEng (Civil Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Waterborne sewage system design and expansion objectives are often focused on minimising initial investment while increasing system capacity and meeting hydraulic requirements. Although these objectives make good sense in the short term, the solutions obtained might not represent the optimal cost-effective solution to the complete useful life of the system. Maintenance and operation of any system can have a significant impact on the life-cycle cost. The costing process needs to be better understood, which include maintenance and operation criteria in the design of a sewer system. Together with increasing public awareness regarding global warming and environmental degradation, environmental impact, or carbon cost, is also an important factor in decisionmaking for municipal authorities. This results in a multiplicity of different objectives, which can complicate the decisions faced by waterborne sewage utilities. Human settlement and migration is seen as the starting point of expansion problems. An investigation was conducted into the current growth prediction models for municipal areas in order to determine their impact on future planning and to assess similarities between the models available. This information was used as a platform to develop a new method incorporating indirect costs into models for planning waterborne sewage systems. The need to balance competing objectives such as minimum cost, optimal reliability, and minimum environmental impact was identified. Different models were developed to define the necessary criteria, thus minimising initial investment, operating cost and environmental impact, while meeting hydraulic constraints. A non-dominated sorting genetic algorithm (NSGA-II) was applied to certain waterborne sewage system (WSS) scenarios that simulated the evolutionary processes of genetic selection, crossover, and mutation to find a number of suitable solutions that balance all of the given objectives. Stakeholders could in future apply optimisation results derived in this thesis in the decision making process to find a solution that best fits their concerns and priorities. Different models for each of the above-mentioned objectives were installed into a multi-objective NSGA and applied to a hypothetical baseline sewer system problem. The results show that the triple-objective optimisation approach supplies the best solution to the problem. This approach is currently not applied in practice due to its inherent complexities. However, in the future this approach may become the norm. / AFRIKAANSE OPSOMMING: Spoelafvoering rioolstelsel ontwerp en uitbreiding doelwitte is dikwels gefokus op die vermindering van aanvanklike belegging, terwyl dit die verhoging van stelsel kapasiteit insluit en ook voldoen aan hidrouliese vereistes. Alhoewel hierdie doelwitte goeie sin maak in die kort termyn, sal die oplossings verkry dikwels nie die optimale koste-effektiewe oplossing van die volledige nuttige lewensduur van die stelsel verteenwoordig nie. Bedryf en instandhouding van 'n stelsel kan 'n beduidende impak op die lewensiklus-koste hê, en die kostebepalings proses moet beter verstaan word en die nodige kriteria ingesluit word in die ontwerp van 'n rioolstelsel. Saam met 'n toenemende openbare bewustheid oor aardverwarming en die agteruitgang van die omgewing, is omgewingsimpak, of koolstof koste, 'n belangrike faktor in besluitneming vir munisipale owerhede. As gevolg hiervan, kan die diversiteit van die verskillende doelwitte die besluite wat munisipale besluitnemers in die gesig staar verder bemoeilik. Menslike vestiging en migrasie is gesien as die beginpunt van die uitbreiding probleem. 'n Ondersoek na die huidige groeivoorspelling modelle vir munisipale gebiede is van stapel gestuur om hul impak op die toekomstige beplanning te bepaal, en ook om die ooreenkomstes tussen die modelle wat beskikbaar is te asesseer. Hierdie inligting is gebruik as 'n platform om ‘n nuwe metode te ontwikkel wat indirekte kostes inkorporeer in die modelle vir die beplanning van spoelafvoer rioolstelsels. Die behoefte is geïdentifiseer om meedingende doelwitte soos minimale aanvanklike koste, optimale betroubaarheid en minimum invloed op die omgewing te balanseer. Verskillende modelle is ontwikkel om die bogenoemde kriteria te definiëer, in die strewe na die minimaliseering van aanvanklike belegging, bedryfskoste en omgewingsimpak, terwyl onderhewig aan hidrouliese beperkinge. ‘n Nie-gedomineerde sorteering genetiese algoritme (NSGA-II), istoegepas op sekere spoelafvoering rioolstelsel moontlikhede wat gesimuleerde evolusionêre prosesse van genetiese seleksie, oorplasing, en mutasie gebruik om 'n aantal gepaste oplossings te balanseer met inagname van al die gegewe doelwitte. Belanghebbendes kan in die toekoms gebruik maak van die resultate afgelei in hierdie tesis in besluitnemings prosesse om die bes-passende oplossing vir hul bekommernisse en prioriteite te vind. Verskillende modelle vir elk van die bogenoemde doelwitte is geïnstalleer in die nie-gedomineerde sorteering genetiese algoritme en toegepas op 'n hipotetiese basislyn rioolstelsel probleem. Die resultate toon dat die drie-objektief optimalisering benadering die beste oplossing vir die probleem lewer. Hierdie benadering word tans nie in die praktyk toegepas nie, as gevolg van sy inherente kompleksiteite. Desnieteenstaande, kan hierdie benadering in die toekoms die norm word.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The expected peak water demand in a water distribution system (WDS) is an important consideration for WDS design purposes. In South Africa the most common method of estimating peak demand is by multiplying the average demand by a dimensionless peak factor. A peak factor is the ratio between the maximum flow rate (which refers to the largest volume of flow to be received during a relatively short time period, say , expressed as the average volume per unit time), and the average flow rate over an extended time period. The magnitude of the peak factor will vary, for a given daily water demand pattern, depending on the chosen value of . The design guidelines available give no clear indication of the time intervals most appropriate for different peak factor applications. It is therefore important to gain a better understanding regarding the effect of on the derived peak factor. A probability based end-use model was constructed as part of this study to derive diurnal residential indoor water demand patterns on a temporal scale of one second. These stochastically derived water demand patterns were subsequently used to calculate peak factors for different values of , varying from one second to one hour. The end-use model derived the water demand patterns by aggregating the synthesised end-use events of six residential indoor end-uses of water in terms of the water volume required, duration and the time of occurrence of each event. The probability distributions describing the end-use model parameters were derived from actual end-use measurements that had previously been collected in a noteworthy North-American end-use project (Mayer et al., 1999). The original comprehensive database, which included water measurements from both indoor and outdoor end-uses, was purchased for use in this project. A single execution of the end-use model resulted in the synthesised diurnal water demand pattern for a single household. The estimated water demand pattern for simultaneous water demand by groups of households was obtained by adding individual iterations of the end-use model, considering group sizes of between one and 2 000 households in the process. A total of 99 500 model executions were performed, which were statistically aggregated by applying the Monte Carlo method and forming 4 950 unique water demand scenarios representing 29 different household group sizes. For each of the 4 950 water demand scenarios, a set of peak factors was derived for eight selected values. The end-use model presented in this study yielded realistic indoor water demand estimations when compared to publications from literature. In agreement with existing knowledge, as expected, an inverse relationship was evident between the magnitude of the peak factors and . The peak factors across all time intervals were also found to be inversely related to the number of households, which agreed with other publications from literature. As the number of households increased, the degree to which the peak factor was affected by the time intervals decreased. This study explicitly demonstrated the effect of time intervals on peak factors. The results of this study could act as the basis for the derivation of a practical design guideline for estimating peak indoor flows in a WDS, and the work could be extended in future to include outdoor water demand and sensitivity to WDS pressure. / AFRIKAANSE OPSOMMING: Die verwagte water spitsaanvraag is ‘n belangrike oorweging in die ontwerp van ‘n waterverspreidingsnetwerk. Die mees algemene metode in Suid Afrika om spitsaanvraag te bereken is deur die gemiddelde wateraanvraag te vermeningvuldig met ‘n dimensielose spitsfaktor. ‘n Spitsfaktor is die verhouding tussen die maksimum watervloei tempo (wat verwys na die grootste volume water wat ontvang sal word tydens ‘n relatiewe kort tydsinterval, , uitgedruk as die gemiddelde volume per tyd eenheid), en die gemiddelde watervloei tempo gedurende ‘n verlengde tydsinterval. Die grootte van die spitsfaktor sal varieer vir ‘n gegewe daaglikse vloeipatroon, afhangende van die verkose waarde. Die beskikbare ontwerpsriglyne is onduidelik oor watter tydsintervalle meer geskik is vir die verskillende spitsfaktor toepassings. Daarom is dit belangrik om ‘n beter begrip te verkry ten opsigte van die effek van op die verkrygde spitsfaktor. ‘n Waarskynliksheidsgebaseerde eindverbruik model is opgestel om deel te vorm van hierdie studie, om daaglikse residensiële binnenshuise wateraanvraag patrone af te lei op ‘n temporale skaal van een sekonde. Die stogasties afgeleide wateraanvraag patrone is daarna gebruik om die verskeie spitsfaktore te bereken vir verskillende waardes van , wat varieer vanaf een sekonde tot een uur. Die eindverbruik model stel die daaglikse vloeipatroon van een huis saam deur die eindeverbruik gebeure van ses residensiële binnenshuise eindverbruike saam te voeg in terme van the vereiste water volume en die tyd van voorkoms van elke gebeurtenis. Die waarskynliksheids distribusie wat die eindverbruik model parameters omskryf is verkry van werklike gemete eindverbruik waardes, wat voorheen in ‘n beduidende Noord-Amerikaanse eindverbruik projek (Mayer et al. 1999) versamel is. Die oorspronklike en omvattende databasis, wat gemete waardes van binnenshuis en buite water verbruik ingesluit het, is aangekoop vir gebruik gedurende hierdie projek. ‘n Enkele uitvoering van die eindverbruik model stel gevolglik ‘n daaglikse wateraanvraag patroon saam vir ‘n elkele huishouding. Die wateraanvraag patroon vir gelyktydige water verbruik deur groepe huishoudings is verkry deur individuele iterasies van die eindverbruik model statisties bymekaar te tel met die Monte Carlo metode, terwyl groep groottes van tussen een en 2 000 huishoudings in die proses oorweeg is. ‘n Totaal van 99 500 model uitvoerings is gedoen, wat saamgevoeg is om 4 950 unieke watervraag scenarios voor te stel, wat verteenwoordigend is van 29 verskillende huishouding groep groottes. Vir elkeen van die 4 950 watervraag senarios, is ‘n stel spitsfaktore afgelei vir agt verkose waardes. Die eindverbruik model aangebied in hierdie studie lewer ‘n realistiese binnenshuise wateraanvraag skatting, wanneer dit vergelyk word met verslae in die literatuur. Ooreenkomstig met bestaande kennis is ‘n sterk inverse verhouding sigbaar tussen die grootte van die spitsfaktore en . Dit is ook gevind dat die spitsfaktore oor al die tydsintervalle ‘n inverse verband toon tot die aantal huishoudings, wat ooreenstemmend is met ander publikasies in die literatuur. Soos die aantal huishoudings toeneem, het die mate waartoe die spitsfaktor geaffekteer is deur die tydsintervalle afgeneem. Hierdie studie toon duidelik die effek van tydsintervalle op spitsfaktore. Die resultaat van hierdie studie kan dien as basis om praktiese ontwerpsriglyne te verkry in die skatting van binnenshuise spitsvloei in ‘n waterverspreidingsnetwerk, gegewe dat die werk in die toekoms uitgebrei kan word om ook buitenshuise waterverbruik in te sluit, asook sensitiwiteit tot druk in die waterverspreidingsnetwerk.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Plastic shrinkage cracking (PSC) is the cracking caused by the early age shrinkage of concrete within the first few hours after the concrete has been cast. It results in unsightly surface cracks that serve as pathways whereby corroding agents can penetrate the concrete which shortens the expected service life of a structure. PSC is primarily a problem at large exposed concrete surfaces for example bridge decks and slabs placed in environmental conditions with high evaporation rates. Most precautionary measures for PSC are externally applied and aimed to reduce the water loss through evaporation. The addition of a low dosage of polymeric fibres to conventional concrete is an internal preventative measure which has been shown to reduce PSC. The mechanisms involved with PSC in conventional and low volume fibre reinforced concrete (LV-FRC) are however not clearly understood. This lack of knowledge and guidance leads to neglect and ineffective use of preventative measures. The objective of this study is to provide the fundamental understanding of the phenomena of PSC. To achieve the objective, an in depth background study and experiments were conducted on fresh conventional concrete and LV-FRC. The three essential mechanisms required for PSC are: 1→ Capillary pressure build-up between the particles of the concrete is the source of shrinkage. 2→ Air entry into a concrete initiates cracking. 3→ Restraint of the concrete is required for crack forming. The experiments showed the following significant findings for conventional and LV-FRC: PSC is only possible once all the bleeding water at the surface has evaporated and once air entry has occurred. The critical period where the majority of the PSC occurs is between the initial and final set of concrete. Any preventative measure for PSC is most effective during this period. The bleeding characteristics of a mix have a significant influence on PSC. Adding a low volume of polymeric fibres to concrete reduces PSC due to the added resistance that fibres give to crack widening, which increases significantly from the start of the critical period. The fundamental knowledge gained from this study can be utilized to develop a practical model for the design and prevention of PSC in conventional concrete and LV-FRC. / AFRIKAANSE OPSOMMING: Plastiese krimp krake (PSK) is die krake wat gevorm word a.g.v. die vroeë krimping van beton binne die eerste paar ure nadat die beton gegiet is. Dit veroorsaak onooglike oppervlak krake wat dien as kanale waardeur korrosie agente die beton kan binnedring om so die dienstydperk van die struktuur te verkort. Dit is hoofsaaklik ʼn probleem by groot blootgestelde beton oppervlaktes soos brug dekke en blaaie wat gegiet is in klimaat kondisies met hoë verdamping tempo’s. Meeste voorsorgmaatreëls vir PSK word ekstern aangewend en beperk die water verlies as gevolg van verdamping. Die byvoeging van ʼn lae volume polimeriese vesels is ʼn interne voorsorgmaatreël wat bekend is om PSK te verminder. Die meganismes betrokke ten opsigte van PSK in gewone beton en lae volume vesel versterkte beton (LV-VVB) is vaag. Die vaagheid en tekort aan riglyne lei tot nalatigheid en oneffektiewe aanwending van voorsorgmaatreëls. Die doel van die studie is om die fundamentele kennis oor die fenomeen van PSK te gee. Om die doel te bereik is ʼn indiepte agtergrond studie en eksperimente uitgevoer op gewone beton en LV-VVB. Die drie meganismes benodig vir PSK is: 1→ Kapillêre druk tussen die deeltjies van die beton is die hoof bron van krimping. 2→ Lugindringing in die beton wat krake inisieer. 3→ Inklemming van die beton is noodsaaklik vir kraakvorming. Die eksperimente het die volgende noemenswaardige bevindinge opgelewer: PSK is slegs moontlik indien al die bloeiwater van die beton oppervlakte verdamp het en indien lug die beton ingedring het. Die kritiese periode waar die meerderheid van die PSK plaasvind is tussen die aanvanklike en finale set van die beton. Enige voorsorgmaatreël vir PSK is mees effektief gedurende die periode. Die bloei eienskappe van ʼn meng het ʼn noemenswaardige effek op die PSK. Die byvoeging van ʼn lae volume polimeriese vesels tot beton verminder die PSK deur die addisionele weerstand wat die vesels bied teen die toename in kraakwydte. Die weerstand vergroot noemenswaardig vanaf die begin van die kritiese periode. Die fundamentele kennis wat in die studie opgedoen is, kan gebruik word vir die ontwikkeling van ʼn praktiese model vir die ontwerp en verhoed van PSK in gewone beton en LV-VVB.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The Tubular Track (TT) railway system is a twin beam modular railway system consisting of two reinforced concrete (RC) beams on which steel rails are continuously supported. The beams are linked with galvanised steel gauge tie bars and continuously supported by soil foundations, and can be used to replace conventional sleeper and ballast railway support. The TT railway system has in the past been analysed with various analysis methods, but were found to obtain con icting results. The con icting results means that one of the analysis methods used for the analysis and design of TT railway sections is either an underestimation or overestimation of section displacements, forces, and stresses; or both methods could even be incorrect. The main emphasis of this investigation is therefore to develop and verify static and dynamic analysis methods and modeling techniques which can be used to simulate the TT railway system accurately. The results and models of the previous analyses are not explicitly investigated in this dissertation, but serve as a motivation for this investigation. The TT system is supported by several soil strata providing vertical support, but geometrically modeling the subgrade strata in the analysis models adds a high level of complexity, and is not feasible for general analysis where soil conditions are mostly unknown. The elastic foundation theory is therefore used to accurately simulate the interaction between beam and foundation and therefore su ciently simpli es the analysis models. Simpli cation of a subgrade foundation by simulating a soil sti ness supporting the TT beam is investigated and analysed by comparing nite element analysis (FEA) results of various soil models using parameters of four known soil formations currently in use at TT railway sections. The FEA of the subgrade formations indicates that there is a linear relationship between the modulus of subgrade reaction for a square plate bearing test and a rectangular, in nitely long plate representing the subgrade support for the TT beams. A square plate bearing test can therefore be performed on site and modi ed to represent the actual subgrade support sti ness of the TT railway structure, whereafter it can be used for the analysis and design of the TT system using one of the proposed analysis methods. The analysis models used range from simple theoretical models based on elastic foundation principles, to two-dimensional (2D) beam elements, and ultimately to complex three-dimensional (3D) solid nite element models. The models used for the analyses are the Single and Double Beam elastic foundation, PROKON 2D beams, ABAQUS 2D beams and ABAQUS 3D solid element models. The alternative analysis methods considered should provide a clear indication of which analysis methods are accurate and feasible for design of the TT system. An in-situ reference model with known de ections and design parameters speci c to a TT railway section is used to analyse the di erent analysis methods' accuracy and validity. The Double Beam, ABAQUS 2D and ABAQUS 3D models were found to provide very similar displacements, bending moments and shear forces for a static analysis, whereas the PROKON and Single Beam models provide unsatisfactory results. The PROKON beam model underestimates the bending moments and shear forces in the rail, and overestimates bending moments and shear forces in the RC beam by a considerably margin. This result can lead to the underdesigning of the rail which could possibly force the RC beam to be subjected to larger maximum bending moments and shear forces than for what it was originally designed for, thereby nullifying or possibly even exceeding the amount for which it was overdesigned. This e ectively accelerates material fatigue, which might be the possible cause of the small cracks in the RC beams which have been found on some TT railway sections, which is currently being investigated. A graphical user interface of the Double Beam method is provided for quick and e cient analysis. Empirical methods used to simulate the dynamic nature of a railway system are often used in the industry to simplify the dynamic loading by determining a dynamic amplitude factor (DAF) to be applied to a static load. An implicit dynamic FEA is therefore performed to obtain the DAF for the reference section, which is subsequently used for the comparison with in-situ de ection results. The results of dynamic analysis validates the proposed empirical analysis method, as the displacements obtained were very similar to actual eld test results, thereby also verifying the accuracy of the proposed analysis methods. The sensitivity of the TT system to design parameters is also investigated to indicate to which parameters the design is sensitive to and where small variations of these parameters require due consideration for future and analysis of the TT railway system. / AFRIKAANSE OPSOMMING: Die Tubular Track (TT) spoorweg stelsel is 'n dubbel balk modulêre treinspoor sisteem bestaande uit twee gewapende beton balke waarop staal spore voortdurend ondersteun word. Die balke word gekoppel deur gegalvaniseerde staal stawe vir laterale styfheid en word deurlopend ondersteun deur grond fondamente, en kan gebruik word om konvensionele dwarslêer en ballast spoorweg ondersteuning te vervang. Die TT spoorweg stelsel was in die verlede met verskeie analiseringsmetodes ontleed, maar het teenstrydige resultate gewerf. Die teenstrydige resultate beteken dat een van die analise metodes wat gebruik word vir die analisering en ontwerp van TT spoorweg seksies 'n onderskatting of oorskatting van verplasings, kragte, en spannings is; of beide metodes kan selfs verkeerd wees. Die hoofklem van hierdie ondersoek is dus die ontwikkeling en veri kasie van statiese en dinamiese analitiese metodes en modellering tegnieke wat gebruik kan word om die TT spoorweg stelsel akkuraat te simuleer. Die resultate en modelle van die vorige ontledings word nie uitdruklik in hierdie proefskrif ondersoek nie, maar dien as 'n motivering van hierdie ondersoek. Die TT stelsel word ondersteun deur verskeie grond strata wat vertikale ondersteuning verskaf, maar meetkundige modellering van die grond strata in die ontledingsmodelle veroorsaak 'n hoë vlak van kompleksiteit wat nie bruikbaar is vir algemene analises waar grondeienskappe meestal onbekend is. Die elastiese fondament teorie word daarom gebruik om die interaksie tussen die balk en die fondament akkuraat te simuleer, en vereenvoudig dus die analitiese modelle voldoende. Vereenvoudiging van 'n grond fondament deur 'n grond styfheid ondersteuning van die TT balk te simuleer is ondersoek en ontleed deur die resultate van eindige element analises van verskillende grond modelle te vergelyk. Bekende ontwerp parameters van vier bekend grondformasies wat tans gebruik word by TT spoorweg seksies word vir hierdie analises gebruik. Die eindige element analises van die grondformasies dui daarop aan dat daar 'n lineêre verwantskap tussen die modulus van grond reaksie vir 'n vierkantige plaat dratoets en 'n reghoekige, oneindige lang plaat dratoets bestaan. 'n Vierkantige plaat dratoets kan dus op terrein uitgevoer en aangepas word om die werklike styfheid van die grond ondersteuning van die TT spoorweg sisteem voor te stel. Die analitiese modelle wat gebruik word wissel van eenvoudige teoretiese modelle wat gebaseer is op elastiese fondament beginsels, twee-dimensionele (2D) balk elemente, asook komplekse driedimensionele (3D) soliede eindige element modelle. Die modelle wat gebruik is vir die ondersoek is die Enkel en Dubbel Balk elastiese fondament, PROKON 2D balke, ABAQUS 2D balke en ABAQUS 3D soliede element modelle. Hierdie reeks bied 'n duidelike aanduiding watter analiseringsmetodes akkuraat en haalbaar is vir die ontwerp van die TT stelsel. 'n In-situ verwysingsmodel met bekende de eksies en ontwerp parameters wat spesi ek is vir 'n TT spoorweg seksie word gebruik om die akkuraatheid en geldigheid van die verskillende analitiese metodes te analiseer. Die Dubbel Balk, ABAQUS 2D en ABAQUS 3D modelle verkry baie soortgelyke verplasings, buigmomente en skuifkragte vir 'n statiese analise, terwyl die PROKON en Enkel Balk modelle onbevredigende resultate verkry. Die PROKON model onderskat die maksimum buigmomente en skuifkragte in die staal spoor, en oorskat buigmomente en skuifkragte in die gewapende beton balk. Hierdie resultaat kan moontlik lei tot die onderontwerp van die staal spoor en dwing moontlik vir die gewapende beton balk om blootgestel te word aan groter buigmomente en skuifkragte as vir wat dit oorspronklik ontwerp is, en verontagsaam sodoende moontlik die kragte waarvoor dit oorontwerp is. Dit versnel e ektief materiaal vermoeiing, wat die moontlike oorsaak is van die klein krake wat gevind is in die gewapende beton balke op sommige TT spoorweg seksies wat tans ondersoek word. 'n Gra ese gebruikerskoppelvlak van die Dubbel Balk model is verskaf vir vinnige en doeltre ende ontleding. Empiriese metodes om die dinamiese aard van 'n spoorweg-stelsel te simuleer word dikwels gebruik in die bedryf om dinamiese belasting te vereenvoudig deur middel van die gebruik van 'n dinamiese amplitude faktor (DAF) wat op 'n statiese belasting aangewend word. 'n Implisiete dinamiese eindige element analise word dus uitgevoer om die DAF te ondersoek, wat daarna gebruik word vir die vergelyking met die in-situ de eksie resultate van die in-situ verwysingsmodel. Die resultate van die dinamiese analise bevestig dat die voorgestelde empiriese analise metode gebruik kan word, omdat die verplasings wat verkry baie soortgelyk was aan werklike veld toets resultate, en daardeur ook die veri ëring van die akkuraatheid van die voorgestelde analise metodes bewerkstellig. Die sensitiwiteit van die TT stelsel vir ontwerp parameters word ook ondersoek om aan te dui watter parameters die ontwerp voor sensitief is, en waar klein variasie in hierdie ontwerp parameters behoorlike oorweging vereis vir die toekomstige analisering en ontwerp van die TT spoorweg stelsel.

Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: On the 9th September 2009, the 178 m Panamanian bulk carrier, the Seli One, ran aground off the coast of Blouberg in Table Bay, South Africa. Due to failed salvage attempts, the vessel has remained stranded approximately 500 m off the Blouberg beachfront. Since the vessel ran aground, a gradual change in the Blouberg beach shape in the lee of the wreck has been observed. The local coastline, which has traditionally been fairly uniform, has assumed a curved shape, with significant sediment accretion being observed in the wave shadow of the wreck. Initially, the Seli One wreck remained intact. However, during a storm on the 4th September 2011, the vessel split up into three separate pieces. The impact that the wreck is having on the local wave, current and sediment transport dynamics remains undefined. This lack of knowledge results in significant risks, relating to shoreline stability and beach amenity. The objective is this study was therefore the determination of the long-term impact of the Seli One shipwreck on the Blouberg beachfront. A review of existing literature has indicated that no empirical relationships are available which could be used to calculate the impact of a shipwreck on nearby coastal processes. Numerous methods are available which can be used to determine the net longshore transport rates, but these cannot be used to quantify the impacts of shipwrecks on the local sediment transport regime. Numerical models were therefore used to determine the impact of the Seli One shipwreck. Through the analysis of simulation results, it was concluded that, as expected, the shipwreck has resulted in a significant reduction in the net longshore sediment transport rate in her lee, resulting in sediment deposition in this area. It was further concluded that the vessel does not result in the complete blockage of longshore sediment transport, and that sediment is able to periodically pass through the lee of the vessel. The simulated beach salient on the 3rd July 2011 was compared to results of a beach survey, performed on the same date specifically for this study. The simulated accretion of approximately 27 m in the lee of the shipwreck agrees well with the measured salient. It has been shown that approximately 75% of the salient accretion occurred within the first two months of the vessel’s arrival. Furthermore, shoreline erosion on the northern side of the salient resulting directly from the shipwreck has been shown to be approximately 15 m. This too occurs relatively rapidly, within approximately two months of the vessels arrival. Following the initial impact of the wreck in its intact configuration, the long-term potential impact of the vessel in its broken-up configuration was determined. This included the assumption that the vessel does not undergo any additional breaking-up, and remains in its three-piece configuration indefinitely. This has shown that the salient width resulting from the shipwreck is reduced to approximately 20 m, compared to the initial 27 m. However, shoreline erosion on the northern side of the wreck has increased from approximately 15 m initially to approximately 18 m in the long-term, which is caused by the continuous sedimentation between the vessel and the beach. A two-dimensional coupled wave, current and sediment transport model has been developed and has shown that the wave shelter resulting from the Seli One results in the formation of a submerged salient between the vessel and the shoreline. It was found that shipwrecks have the potential of significantly altering local longshore sediment transport characteristics in general. Depending on local conditions, this may pose serious risks, both in terms of jeopardizing local seaside infrastructure, as well as creating dangerous swimming conditions. Considering the impact that a shipwreck can have on local shoreline changes, with special regard to the rate at which these shoreline changes can occur, it is recommended that the results obtained from the current study be used to estimate the impact of potential future shipwreck scenarios in Table Bay. / AFRIKAANSE OPSOMMING: Op die 9de September 2009 het die 178 m lange Panamese vragskip, die Seli Een, aan die kus van Bloubergstrand in Tafelbaai, Suid Afrika, gestrand. Weens mislukte reddingspogings, het die skip ongeveer 500 m van die kuslyn gestrande gebly. Sedertdien, is ‘n geleidelike verandering in die vorm van Bloubergstrand se kuslyn waargeneem. Die kuslyn, wat tradisioneel redelik uniform en reguit was, het onlangs ‘n aansienlike geboë vorm aangeneem, met ‘n beduidende hoeveelheid sand wat in die skip se lykant neerset. Aanvanklik het die Seli Een wrak ongeskonde gebly, maar tydens ‘n storm op die 4de September 2011, het die skip in drie afsonderlike stukke opgebreek. Die impak wat die wrak op die golf, strome en sediment vervoer dinamika het,bly ongedefinieërd. Hierdie gebrek aan kennis veroorsaak ‘n aansienlike hoeveelheid risiko’s met spesifieke betrekking tot kuslyn stabiliteit en strand gerief. Die doel van hierdie studie was dus om die langtermyn-impak van die Seli Een skeepswrak op Bloubergstrand te bepaal. 'n Hersiening van bestaande literatuur het aangedui dat geen empiriese verhoudings beskikbaar is wat gebruik kan word om die impak van 'n skeepswrak op die nabygeleë kustelike prosesse te bereken nie, maar wel versekeie metodes wat gebruik kan word om die netto langsstroom sediment vervoer te bepaal. Hierdie verhoudings kan egter nie gebruik word om die impak van ‘n skeepswrak op die sediment vervoer meganisme te kwantifiseer nie, dus is numeriese modelle gebruik om die impak van die Seli Een skeepswrak te bepaal. Die skeepswrak het ‘n aansienlike vermindering in the netto langsstroom sediment vervoer veroorsaak, wat tot die afsetting van sediment in hierdie gebied lei. Dit is ook verder bepaal dat die Seli Een nie die volledige verstopping van langsstroom sedimentvervoer veroorsaak nie, maar dat sediment van tyd tot tyd in staat is om deur die lykant van die skeepswrak te beweeg. Die gesimuleerde strand aanwas van die 3de Julie 2011 is vergelyk met resultate van ‘n strand-opmeting, wat uitgevoer is op dieselfde datum, spesifiek vir hierdie studie. Die gesimuleerde aanwas, van ongeveer 27 m in die lykant van die skeepswrak, stem saam met die gemete aanwas. Ongeveer 75% van die aanwas het binne twee maande van die aankoms van die Seli Een plaasgevind. Verder is dit getoon dat aan die noordelike kant van die aanwas, ongeveer 15 m van die kuslyn weggespoel het as gevolg van die Seli Een. Na die aanvanklike impak van die wrak in sy ongeskonde konfugirasie, is die potensiële langtermyn impak van die skip in sy opgebreekte konfugirasie bepaal. Dit sluit die aanname in dat die skip nie enige bykomende breke ondergaan nie, en in sy drie-stuk konfigurasie bly. Dit het getoon dat die breedte van die aanwas, wat veroorsaak is deur die skip, verminder tot ongeveer 20 m in vergelyking met die aanvanklike 27 m. Verder is dit getoon dat die erosie aan die noordelike kant van die Seli Een vermeerder het van die aanvanklike 15 m na ongeveerder 18 m in die langtermyn. Die oorsaak hiervaan is die aaneenlopende sedimentasie tussen die wrak en die strand. 'n Twee-dimensionele gekoppelde golf, stroom en sediment vervoer model is ontwikkel en het getoon dat die golf skuiling, as gevolg van die Seli Een, sedimentasie tussen die skip en die kuslyn veroorsaak. Daar is gevind dat skeepswrakke die potensiaal het om aansienlike veranderinge aan die nabygeleë langstroom sediment vervoer stelsel te veroorsaak. Afhangende van die plaaslike omstandighede, kan hierdie ernstige risiko’s veroorsaak, beide in terme van die gevaar vir plaaslike kustelike infrastruktuur, sowel as die generasie van gevaarlike swem toestande. Met inagneming van die impak wat 'n skeepswrak op plaaslike kuslyn veranderinge kan hê, met spesiale verwysing na die tempo waarteen hierdie kuslyn veranderinge kan plaasvind, word dit aanbeveel dat die resultate wat verkryg is vanuit die huidige studie, gebruik word om die impak van moontlike, toekomstige skeepswrakke in Tafelbaai te bepaal.