Dynamic behaviour of tunnel elements during the immersion process: A study to the influence of swell waves and wind waves on the immersion system

Dynamic behaviour of tunnel elements during the immersion process: A study to the influence of swell waves and wind waves on the immersion system

Nagel, G.W.

Vrijling, J.K. (mentor)
Bakker, K.J. (mentor)
Metrikine, A.V. (mentor)
Huijsmans, R.H.M. (mentor)
De Groot, D. (mentor)

Civil Engineering and Geosciences

Hydraulic Engineering

2011-02-07

Immersion of tunnels is an often used technique in rivers and canals. The transport of tunnel elements can be done under offshore conditions, but immersing the elements under these conditions is not common practise. The tunnel elements of the Busan-Geoje Fixed Link in South Korea were immersed in such a situation. During this process, several loads act on the element and the equipment, such as current and wave loads. Wave loads consist of relatively long waves (swell waves) and short waves (wind waves). The wave induced motions of the tunnel element are restricted during immersion due to serviceability limit state conditions. In this study, the influence of swell and wind waves on the immersion configuration is analysed. In order to solve this problem, equations of motion are composed and solved to analyse the dynamic behaviour. In the first step, the natural frequencies of the configuration are determined, and in the next step the total response is analysed. The latter is given in response amplitude operators, that represent the ratio between motion of the tunnel element and height of the wave per frequency. Using this methodology, locating the resonance peaks in the graphs is straightforward. Rough estimations of added mass and damping values cause some uncertainty in the results. One of the findings is that some natural frequencies of the configuration are close to the frequency of swell waves. Especially the frequency of the rotation of the tunnel element is close to the frequency of swell waves. The influence of wind waves on the forces in the immersion cables is negligible. Large motions of the element and high forces in the cables may be expected during resonance. This should be avoided by adjusting the immersion configuration, for example by decreasing the cross section of the floaters. This will result in larger natural periods. The main conclusion is that the influence of swell waves on the forces in the cables is significantly larger than the influence of wind waves.

immersed tunnel
dynamics
swell

http://resolver.tudelft.nl/uuid:47bf3b22-3450-4f72-8c45-57e5d4e17321

2011-02-09

Student theses

master thesis

(c) 2011 Nagel, G.W.