Climate changes within the last century caused and are still causing rising sea water levels. This has imminent consequences for the coastal protection systems worldwide and also in Germany. Adaptations of the dike structures to the new situation are needed, but the standard methods often entail environmental problems. The two mostly used methods and their drawbacks are: (i) closed revetments to enforce the dike structure which leads to sealing of the soil and (ii) heightening of dikes which has a high space requirement and, therefore, a high impact on the environment. An improved approach for the protection of embankments and dikes against sea waves is the use of porous and bonded revetments. This type of structure combines the advantages of bonded revetments (high stability) and of rubble layers (high permeability). Especially the high porosity allows for a quick resettlement of marine flora and fauna. Despite their relevance, highly porous revetments are poorly understood in terms of the processes associated with the interaction of waves, structure and foundation, thus hindering a wider application of this type of structure. The present thesis should, therefore, give a more detailed overview of the effects of a porous, bonded revetment on said processes. A systematic analysis of the literature was performed to identify all processes involved in the interaction as well as possible knowledge gaps in former research studies. Furthermore, the data from large-scale tests which were performed prior to the dissertation in the Large Wave Flume (GWK) in Hannover were analysed further to describe the processes precisely and to carefully plan the additional numerical simulations. The numerical simulations with the CFDmodel COBRAS-UC (VARANS – Volume averaged Reynolds averaged Navier-Stokes) were used to extend the range of the tested conditions of the GWK-tests including different slope steepnesses and wave conditions. Based on the extended data set, prediction formulae for the hydrodynamic processes were developed. The analyses showed several general and specific findings for the porous, bonded revetments. First of all, the importance of the wave set-up on the structure is often underestimated. This parameter is mostly considered for beaches and structures with flatter slopes. But for steeper structures like the porous bonded revetment considered in this study, a distinct effect of the wave set-up especially on the wave run-up and run-down was also determined. Furthermore, the effect of the porous bonded revetment and its thickness on the hydrodynamic processes such as wave reflection, wave run-up/run-down and the corresponding velocities is described. Moreover, the effect of the wave set-up is present in the sand foundation, where especially the location of the maximum set-up in the sand is noteworthy.
Prediction Formulae for Processes on and in Porous Bonded Revetments - An Experimental and Numerical Study -
Bemessungsformeln für Prozesse auf und in porösen verklammerten Deckerken - Eine experimentelle und numerische Studie -
2013
Miscellaneous
Electronic Resource
English
DDC: | 627 |
British Library Conference Proceedings | 1997
|Numerical Simulation of Rip-Rap Revetments in Tidal Areas
HENRY – Federal Waterways Engineering and Research Institute (BAW) | 2014
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