University of Twente Student Theses
The effect of a foreland on the piping assessment results for river dikes : A comparison between the rule of Sellmeijer and D-Geo Flow software for a piping assessment of river dikes with a foreland.
Couwenberg, F.J.R. (2021) The effect of a foreland on the piping assessment results for river dikes : A comparison between the rule of Sellmeijer and D-Geo Flow software for a piping assessment of river dikes with a foreland.
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| Abstract: | Piping or backwards erosion is an important failure mechanism within the safety assessment of the Dutch dikes. The failure mechanism occurs by high water levels, which causes a channel(pipe) under the dike due to the strong seepage flow. For the assessment of this failure mechanism the adjusted rule of Sellmeijer is prescribed to calculate the failure probability of the dikes. However, the adjusted rule of Sellmeijer and several other changes in the safety assessment has led to higher failure probabilities. As a result more dike sections fail to comply with the norms. More advanced piping assessment methods such as the D-Geo Flow software of Deltares can refine this failure probabilities. The presence of foreland with poorly permeable top layer has a dampening effect on the failure mechanism of piping. The rule of Sellmeijer and D-Geo Flow software have a different approach towards the inclusion of a foreland in the assessment of piping. Therefore it is expected that these differences lead to different outcomes for the piping assessment. In the rule of Sellmeijer formula the foreland is included by an extension of the seepage length. In D-Geo Flow the entire groundwater flow through the foreland is modelled. For researching the influence of the foreland on the different outcomes between both methods, a standard dike configuration with a foreland is generated. With this standard dike configuration the influence of different parameters on the results of both methods is analysed. The researched parameters are: the foreland length, the conductivity of the piping sensitive layer, the conductivity of the foreland top layer and the thickness of the piping sensitive layer. The results show that D-Geo Flow in general provides more optimistic outcomes than the rule of Sellmeijer. However, this is not the case for low foreland top layer conductivities, there the rule of Sellmeijer is less conservative. The differences are the largest for small piping sensitive layers and long forelands. In further research it is recommended to research the d70 parameters as well in order to improve the results for the conductivity of the piping sensitive layer. Besides that it would be useful to research the effect of the differences between both methods on the failure probability for practical examples. With this the added value of an assessment with D-Geo Flow could be further confirmed. |
| Item Type: | Essay (Bachelor) |
| Faculty: | ET: Engineering Technology |
| Programme: | Civil Engineering BSc (56952) |
| Link to this item: | https://purl.utwente.nl/essays/85765 |
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