University of Twente Student Theses


Creating a decision support matrix for the design of a submerged floating tunnel

Lent, E.G. van (2017) Creating a decision support matrix for the design of a submerged floating tunnel.

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Abstract:During the design phase of a submerged floating tunnel not a limited amount for research time is available. This could leave some SFT types not thoroughly being investigated and can result in neglecting a possible good solution for a certain problem. To solve this problem a decisions support matrix has been created. This matrix gives a clear overview between the differences of the four SFT types. The decision support matrix has been made by performing a literature study and numerical modelling. The literature study showed that the advantages and limitations of different design solutions for SFTs could be divided into general, SFT specific and SFT type specific advantages and limitations. It became clear that SFTs advantages are that they cannot be seen above water and could be a solution for crossing longer and deeper waters than has been done before. The elliptical or rectangular cross section shape seems to be preferable. Likewise the most common materials used for cross section underwater are concrete and steel or a combination of both. For the different SFT types the difference in foundations played the most important role towards the advantages and disadvantages of every SFT type. For the numerical analyses four reference designs have been modelled. Before these reference designs could be modelled the loads on the designs and the requirements of the design should be determined. The loads can be divided in permanent, variable and accidental loads. The permanent and variable loads are always affecting the SFTs and therefore the SFTs should be designed to withstand these loads. The accidental loads are loads that hopefully do not occur, but the SFT should be able to withstand them in case of an accident. All loads have been determined and calculated so they could be used for the modelling of the reference designs. Following the requirements were calculated. The requirements are a maximum tension in the cross sections of 2 N/mm2 and a maximum displacement of 1/300 of the SFTs length. Also the tension in the cables could not surpass the maximum tension steel cables can absorb and the pressure-bearing-poles could not exceed a tension of 355 N/mm2. With the loads and requirements determined the reference designs could be modelled. When the reference designs met the requirements the accidental loads were applied to see what SFT types were able to withstand these loads. The found results were used to create the decision support matrix. After the decision support matrix was created, it could be used to assess what SFT type would be suitable for the Unkapani tunnel project. The outcome was that the pressure-bearing-pole type would be the most adequate solution. When the dept increases the tethered SFT would become more adequate. In the end the created decision support matrix seems like a good tool to get a first impression of the characteristics form the four SFT types and give a clear overview what SFT type could be a preferable during certain circumstances. Although the matrix could be expanded more by also compare the SFT types in case of a submarine collision and a seismic event. After the decision support matrix has been used to determine what SFT type should be used, the specific SFT should be designed from scratch. Since the reference designs only goal were to compare the four SFT types.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
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