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Setting up and testing a method to determine the influence of animal burrowing on failure probability of dike trajectories in the Netherlands
Veltkamp, T.J. (2025) Setting up and testing a method to determine the influence of animal burrowing on failure probability of dike trajectories in the Netherlands.
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| Abstract: | The Netherlands has a proactive approach to dike safety, by assessing dikes with the BOI methodology. This methodology allows engineers and government workers to assess whether a dike is safe or not through failure mechanisms. The way to do this is clear, but one thing is not taken into account. How to deal with animal burrowing? The main problem with animal burrowing is that animals destroy the protective clay cover layer, which prevents water from freely flowing into the sand core of certain dikes and also prevents water from eroding the dike from below. This research aimed to develop and evaluate a methodology to integrate the influence of animal burrowing into the BOI framework and quantify its effect on the probability of dike failure. In order to achieve this, the influence of animal burrowing is assessed for each selected failure mechanisms, macrostability, microstability, and piping. After this, the failure mechanisms are coupled in four burrowing scenarios. At the outer toe of the dike, the outer slope of the dike, the inner slope of the dike, and in the inner toe or ditch. The chance of occurring for each scenario can be multiplied by the resulting failure probability to combine with the regular calculation to a new failure probability. For example: P(burrow)=X and P(no burrow)=1-x To test the methodology, a dike traject of 28.9 km divided over 153 cross sections, based on macro-stability calculations, was assessed on animal burrowing. To do this, a tool was created that automates the adjustments to the parameters of the failure mechanisms and calculates the new failure probability or safety factor. This tool uses D-stability calculations and schematization to determine parameters such as cover layer thickness and hydraulic conditions for other failure mechanisms. For the initial test, a burrow 0.5 meters under high water level with a length of 10 meters was used on the outer dike slope, a 5 meter length burrow at the inner slope and a 1 meter deep burrow was used at the toes. Each of these burrows is a unique scenario. Due to these burrows, out of the 153 cross sections, 3 failed in macrostability, 11 in piping, and 22 in microstability due to outer slope burrowing. The failure probability of macrostability changed between a factor of 1 and 103 , with outliers of a factor 106 , and the failure probability of the piping changed within the same range with outliers of 1010. Analysis also indicated potential impacts on inner slope stability; however, some would say that it fails once it penetrates below the phreatic line. These results do not mean that the entire dike trajectory gets rejected on the norm, however several sections do get rejected by the norm. The advice is to look at section level and not on trajectory level for animal burrowing. The sensitivity analysis showed interesting results where if the end of the burrow remains below 50% of the dike base, all except two dikes remain safe with animal burrowing. However, once the end of the burrow reaches 75% of the dike base is reached, half of the affected dikes start to fail to meet their required individual cross-section failure probability. For large dikes, dike base > 50m, this means that they are unlikely to fail to animal burrowing. With these results, this research successfully developed and demonstrated a methodology for embedding animal burrowing into the BOI methodology. The main question remains what is the probability that animals will burrow in a dike. |
| Item Type: | Essay (Master) |
| Faculty: | ET: Engineering Technology |
| Subject: | 56 civil engineering |
| Programme: | Civil Engineering and Management MSc (60026) |
| Link to this item: | https://purl.utwente.nl/essays/106505 |
| Export this item as: | BibTeX EndNote HTML Citation Reference Manager |
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