Thesis ((MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: When constructing a submarine pipeline, construction teams must work in the hostile environment in the ocean known as the surf zone. The surf zone is the area along a shoreline stretching between the first evident point of wave breaking and the beach line. In order to ensure that the pipeline is shielded from the imposing forces within the surf zone, engineers use a burial technique which leaves the pipeline length in the surf zone buried underneath the active seabed once construction is finished. Thus a temporary surf zone trench is dredged and protected by an open-ended cofferdam built using iron sheet piles. As a result of the incoming wave climate and the surf zone currents created by this wave climate, sedimentation in and around the trench becomes problematic. In this study alternative geometric layouts for the open-ended cofferdam protecting the surf zone trench are investigated, attempting to minimize the sediment build-up in and around the trench. This was done by using both a 3D qualitative physical model conducted at the CSIR in Stellenbosch, and numerical model using MIKE developed by DHI. However, this study only considers sediment build-up and not structural integrity and constructability of the cofferdam designs. Combining the observations of both the physical- and numerical models, a conclusion was drawn that a structure built perpendicular to the shoreline with a 45oextended arm built from the upstream edge of the cofferdam wall, is the most effective. No dimensions are given as the cofferdam design will change depending on the site specific characteristics. Also an increase in structure length will result in the mouth of the structure being located outside the active sediment zone, which leads to a longer period of time before the pipeline pathway is compromised by sediment. / AFRIKAANSE OPSOMMING: Tydens die konstruksie van 'n onderwaterse pyplyn, moet konstruksie spanne in 'n gevaarlike gedeelte van die see werk naamlik die brandersone. Die brandersone kan gedefinieer word as die area tussen die eerste punt waar branders breek en die strandlyn. Om die pyplyn te beskerm teen die kragte wat branders op dit uitoefen, gebruik ingenieurs 'n installasietegniek waar hul die brandersone seksie van die pyplyn onder die aktiewe seebodem begrawe. Om die tegniek te bewerkstellig, grawe kontrakteurs 'n sloot deur die brandersone en beskerm dit met 'n tydelike struktuur bekend as 'n kofferdam. As gevolg van die inkomende branders en die strome wat deur die branders aangedryf word, kan die opbou van sediment in, en rondom die sloot in die brandersone problematies word. Hierdie studie ondersoek alternatiewe uitlegte vir die tydelike kofferdam struktuur met die oog daarop om die opbou van sediment in, en rondom die struktuur te verminder. Die doel was nagestreef deur gebruik te maak van beide 'n 3-dimensionele fisiese model, gebou en gebruik by die WNNR in Stellenbosch, en 'n numeriese model wat op MIKE, ontwikkel deur DHI gedoen was. Let wel die studie het slegs die sediment beweging in die nabye area van die tydelike kofferdam struktuur in ag geneem en nie die praktiese implimentering en strukturele integriteit van die struktuur nie. Deur die observasies van beide die fisiese- en numeriese modelering in ag te neem, is die volgende gevolgtrekkings gemaak. 'n Struktuur wat loodreg met die strandlyn gebou is en met 'n 45o arm wat na die stroom-op kant toe uitstrek, was die mees effektiewe een. Geen dimensies is deurgegee nie aangesien die ontwerp sal verskil afhangende van die spesifieke area waar die projek aangepak word. Daar is ook gesien dat indien die struktuur langer gemaak word, sal die kontrakteur langer tyd h^e voordat daar sediment probleme in die brander sone sloot ondervind sal word.

As obras de desvio de rios para a construção de barragens, embora tenham caráter provisório, são de estrema importância, pois definem como o empreendimento será executado, garantindo segurança à sua construção, dentro de riscos calculados, devendo no entanto ser o mais econômica possível. As estruturas de desvio devem se encaixar no arranjo das estruturas permanentes, podendo ser utilizadas como tal. Este trabalho tem o intuito de apresentar as principais estruturas utilizadas em esquemas de desvio de rios e caracterizar sua utilização e aplicabilidade. Sempre que possível foram apresentados esquemas utilizados na prática ou previstos em projeto, para melhor exemplificar e caracterizar as diversas estruturas e as possíveis soluções para desvio de rios. / Diversion works for dam construction are temporary. Nevertheless, they are extremely important, since they define how the construction is going to be made, and assuring its safety, within calculated risks. But, they have to be as economical as possible. The diversion structures must fit the global arrangement of the project, being in some cases be used as permanent structures. This document has the objective of present the main diversion structures used in diversion works schemes, as well as characterize their utilization and applicability. Whenever possible, it was presented examples of schemes either already used or just previewed on design, to better characterize and exemplify the many structures and possible solutions for river diversion.

As obras de desvio de rios para a construção de barragens, embora tenham caráter provisório, são de estrema importância, pois definem como o empreendimento será executado, garantindo segurança à sua construção, dentro de riscos calculados, devendo no entanto ser o mais econômica possível. As estruturas de desvio devem se encaixar no arranjo das estruturas permanentes, podendo ser utilizadas como tal. Este trabalho tem o intuito de apresentar as principais estruturas utilizadas em esquemas de desvio de rios e caracterizar sua utilização e aplicabilidade. Sempre que possível foram apresentados esquemas utilizados na prática ou previstos em projeto, para melhor exemplificar e caracterizar as diversas estruturas e as possíveis soluções para desvio de rios. / Diversion works for dam construction are temporary. Nevertheless, they are extremely important, since they define how the construction is going to be made, and assuring its safety, within calculated risks. But, they have to be as economical as possible. The diversion structures must fit the global arrangement of the project, being in some cases be used as permanent structures. This document has the objective of present the main diversion structures used in diversion works schemes, as well as characterize their utilization and applicability. Whenever possible, it was presented examples of schemes either already used or just previewed on design, to better characterize and exemplify the many structures and possible solutions for river diversion.

Stockholm lider idag av omfattande bostadsbrist och ständigt ökande befolkningsmängd. För att möta detta ökande behov av bostäder i Stockholm finns en nödvändighet i att utforska nya vägar till att åstadkomma detta. Här finns en unik möjlighet till en förtätning av staden genom att utnyttja Stockholms stora vattenarealer för att bygga flytande bostäder. Som alternativ till den traditionella byggkonsten ämnar examensarbetet till att demonstrera de kvaliteter som finns med att bo på vatten genom att utforma ett attraktivt bostadsområde med flytande konstruktion. Projektet illustreras i det tidigare hamnområdet vid Liljeholmskajen i Årstadals hamn, Stockholm. För att åstadkomma detta utförs fallstudier på olika typer av flytande konstruktioner som finns på den svenska marknaden för att fastställa de bästa konstruktionslösningarna som leder till färdiga förslagshandlingar. Resultatet visar att ett flytande bostadsområde är genomförbart med dagens teknik som ett sätt att förtäta staden. Vidare utredningar måste dock göras för att i framtiden legalisera och förenkla lagstiftningen kring denna typ av boende. / Present day, Stockholm suffers from a significant lack of dwellings and the population in the county is ever increasing. To meet this escalating demand for residences it is essential to explore new paths of accomplishing this. Here lies a unique opportunity for densification of the city by taking advantage of Stockholm’s grand water areal to build floating residences. This essay aims to demonstrate an alternative to the traditional arts of building construction by presenting the qualities of living on water in a proposition for a floating residential area. The project is displayed as placed in an old industrial port - Liljeholmskajen - in Årstadal, Stockholm. To achieve this, case studies are made on different types of floating constructions on the Swedish market to establish the best constructional solutions, which have led to complete concept drawings. The result illustrates that a floating residential area is achievable with today’s technology as a method of dealing with the densification of cities. Further investigations are necessary to legalize and simplify the legislation of this type of living

The aim of this thesis is to undertake simplified design and assessment of cofferdam under vertical surcharge in the form of virtual project. Cofferdam constructed on the sea shore must be able to withstand all loads to enable construction of cut and cover tunnel. As a part of the design it is required to assess ground conditions and it is necessary to review feasibility of the structure on the sea. The construction will be described in construction phases and graphically demonstrated in construction sequence drawing. Because the structure is designed for life time of five years, temperature load on struts is studied in the thesis and further considered in structural analysis. Furthermore, it is required to compare analytical models from GEO5 and PLAXIS. Horizontal frame is analysed separately in Scia Engineer. Structural members – cofferdam wall, waler beam and strut are checked in this thesis. For the design of the cofferdam wall second order theory is considered. All mentioned requirements were accomplished with help of corresponding Eurocodes, books and technical advice. Results of this work are feasible and it was possible to design all members to enable construction of the cut and cover tunnel. The phasing was designed such that deformation of the cofferdam is minimalized and use of machinery is limited to machines on temporary platforms. Comparison of two different analytical models showed that different soil modelling has great effect on internal forces, even though the shape of the bending curve is very similar, values obtained from PLAXIS software are much higher. Assessment of the structural members is done according to Eurocode 3, and horizontal frame is checked also against disproportionate collapse.