Print Email Facebook Twitter Retarding the breaching process of dikes Title Retarding the breaching process of dikes Author Lemmens, D. (Van Oord Marine Ingenuity, Rotterdam) Bisschop, F. (TU Delft Offshore and Dredging Engineering) Visser, P.J. (TU Delft Rivers, Ports, Waterways and Dredging Engineering) van Rhee, C. (TU Delft Offshore and Dredging Engineering) Date 2016 Abstract Dikes constructed from sand generally have a sand core and clay layers on the slopes and the crest to protect the core against erosion. In extreme hydraulic conditions, several failure mechanisms can lead to destruction of the clay layers, exposing the sand core to water. When water overtops the dike and the protective cover of the land-side slope or the crest fails, water flows over the core and erodes the sand. The dike starts to breach, and eventually the land behind the dike is flooded. The rate at which the dimensions of the breach grow influences the rate of inundation of the polder. Reduction of the inundation rate may be achieved by retarding the breaching process. This may reduce the number of casualties, resulting in increasing safety for the inhabitants. In order to achieve, for instance, a safety level ten times higher, mortality has to decrease by a factor of 10. The breaching process can be retarded by reducing the erosion velocity of the sand core. Experiments were executed to investigate the effect on the erosion velocity of adding bentonite to sand. The results of these experiments showed a significant reduction of the permeability and erosion velocity of the sand–bentonite mixtures compared with those of pure sand. The effect of adding bentonite on the breaching process was investigated by applying the Bres model (breach erosion in sand dikes model) to a sand dike tested in a large-scale field experiment (Zwin'94). It was found that adding a small percentage of bentonite reduces the rate of breach growth and the inundation rate in the polder. For the Zwin’94 dike it was determined that 5·4% of bentonite is sufficient to reduce the inundation rate below a threshold value of 0·5 m/h, leading to a significant increase in safety. Subject failure/granular materials/sea defences To reference this document use: http://resolver.tudelft.nl/uuid:bd0aeefe-89ad-4884-8f3f-49b60811fc7a DOI https://doi.org/10.1680/jmaen.2015.20 Embargo date 2017-05-23 ISSN 1741-7597 Source Proceedings of the Institution of Civil Engineers - Maritime Engineering, 169 (3), 99-114 Part of collection Institutional Repository Document type journal article Rights © 2016 D. Lemmens, F. Bisschop, P.J. Visser, C. van Rhee Files PDF jmaen.2015.20.pdf 1.17 MB Close viewer /islandora/object/uuid:bd0aeefe-89ad-4884-8f3f-49b60811fc7a/datastream/OBJ/view