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Conceptual solutions to minimise the effects of cobbles on the sand-bypassing system at the Port of Ngqura

dc.contributor.advisorTheron, Andre Karlen_ZA
dc.contributor.authorSchmidt, Niklaen_ZA
dc.contributor.otherStellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.en_ZA
dc.date.accessioned2016-12-22T13:11:03Z
dc.date.available2016-12-22T13:11:03Z
dc.date.issued2016-12
dc.identifier.urihttp://hdl.handle.net/10019.1/100063
dc.descriptionThesis (MEng)--Stellenbosch University, 2016.en_ZA
dc.description.abstractENGLISH ABSTRACT: The Port of Ngqura constructed two breakwaters to create safe anchorage for vessels at berth. These coastal structures obstructed the natural movement of sand alongshore. A fixed sand-bypassing system was installed to transport the obstructed sand from the up-drift to the down-drift side of the Port. The system failed to reach the design rate; leading to major sand accretion against the western breakwater. The main problem was the presence of coarse material causing an obstruction at the jet pumps that prevents further bypassing of the material, located in the sandtrap. The system was designed to handle particles with a diameter of 150 mm, but it was the presence of particles larger than 150 mm that particularly created a problem. Two alternative fixed sand-bypassing systems, the Nerang river and Tweed river bypassing schemes, were investigated to determine if similar problems arose and if lessons could be learned for application at the Port of Ngqura. To find a solution to this challenge, it was necessary to determine where these particles originated from in the first part of the study. It was found that the coarse material originated from mainly three sources: temporary construction works required for the construction of the bypassing system, the rock revetment behind the sand-bypassing jetty, as well as from natural sources. While the origin and properties of the first two sources were known, further investigation was required to determine the source of the natural coarse material. The objectives of this part of the study were to gain a better understanding of the principles of sediment transport and particle motion as well as to investigate the origin, volume and properties of the natural source. The Swartkops river was found to be the main source of coarse material for the western section of Algoa Bay, with an estimated mean annual volume of 150 m3. Using the findings gained in this first part of the study, five viable solutions were conceived to prevent the obstruction at the jet pump intakes. All five solutions are considered viable solutions to the current problem at hand, but some were deemed more viable than others. For some of the conceptual solutions to function to their full potential, modifications were also required at the revetment and sandtrap. The sandtrap modifications included the removal of all the coarse material currently located in the sandtrap. For the revetment modifications, the armour layer at a certain section should be reconstructed and units that do not meet the requirements should be replaced. The study concludes that each proposed solution together with the required sandtrap and revetment modifications can serve as a potential solution to achieve the design bypassing rate of the fixed sand-bypassing system at the Port of Ngqura. The conceptual solution that proved the most promising, however, is the pile-and-mesh structure due to the relatively small impact that this proposed solution would have on the surrounding coastline, the low maintenance required, and high capacity of the structure.en_ZA
dc.description.abstractAFRIKAANSE OPSOMMING: Die Hawe van Ngqura het ’n sandverbyvoering-sisteem geïnstalleer om die sand wat deur die hawe se breekwaters geblokkeer word, van die opwaartse kant na die afwaartse kant te vervoer. Ná die eerste paar jaar het die sisteem nie die teiken volume bereik nie, wat gelei het tot ’n sandopbouing teen die westerse breekwater. Daar is verskeie redes hoekom die sisteem nie die teiken volumes bereik het nie, maar een probleem het herhaaldelik voorgekom. Die sisteem was oorspronklik ontwerp om sediment kleiner as 150 mm te verwyder, maar daar is steeds sediment met kleiner diameters in die vanggat teenwoordig. Die probleem was die teenwoordigheid van growwe sediment om die inlaat van die jet pomp, wat veroorsaak het dat die pompe nie verder kon funksioneer nie. Deur deeglike ondersoek is dit bepaal dat die growwe sediment afkomstig is van die tydlike strukture wat benodig was vir die konstruksie van die sisteem, die rotsbeskutting, asook natuurlike bronne. Vir die eerste twee bronne genoem was die oorsprong en eienskappe bekend, maar oor die laasgenoemde bron was daar meer inligting nodig. Die doelwit van die studie was om te bepaal wat die natuurlike bron was, die volume wat dit verskaf, asook die metode wat dit vervoer word. Daar is gevind dat die Swartkopsrivier die hoofbron in die gedeelte van Algoa Baai is, en dat daar ’n jaarlikse volume van 150 m3 gelewer word. Die literatuurstudie is hoofsaaklik gebaseer op die manier waarop growwe sediment in die kusstelsel beweeg en dit dan te vergelyk met kleiner sediment soos sand. Die diepte tot waar die growwe sediment in die kusstelsel beweeg, is ook bepaal. Met die bogenoemde inligting was dit moontlik om konseptuele oplossings te vind om die blokkasie by die inlaat te vermei. Vyf konseptuele oplossings is ontwerp om te verhoed dat die pompe in die toekoms geblokkeer word. Elke oplossing is gebaseer op ’n spesifieke beginsel vir growwe sedimentvervoer wat gelei het na die algemene idee. Die ligging, ontwerp, installasie, kapasiteit en bekommernisse van elke oplossing word deeglik verduidelik in die literatuurstudie. Verskeie van die konseptuele oplossings het veranderinge benodig aan die rotsbeskutting en vanggat voor die oplossing behoorlik kon funksioneer. By die vanggat was dit nodig om al die growwe materiaal wat tans teenwoordig is, behoorlik te verwyder. Vir die rotsbeskutting is die hoof- en onderlaag herontwerp om te verhoed dat die eenhede in die lae kan beweeg. Dit kan dus geargumenteer word dat elke voorgestelde oplossing kan dien as ’n oplossing vir die probleem om ten einde die teiken verbyvoering te bereik by die Hawe van Ngqura.af_ZA
dc.format.extent119 pages : illustrationsen_ZA
dc.language.isoen_ZAen_ZA
dc.publisherStellenbosch : Stellenbosch Universityen_ZA
dc.subjectSand bypassing -- System analysisen_ZA
dc.subjectSediment transporten_ZA
dc.subjectJet pumpsen_ZA
dc.subjectUCTDen_ZA
dc.titleConceptual solutions to minimise the effects of cobbles on the sand-bypassing system at the Port of Ngquraen_ZA
dc.typeThesisen_ZA
dc.description.versionMasters
dc.rights.holderStellenbosch Universityen_ZA


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