Levees provide an ideal natural habitat for beavers and other animals. However, their burrowing activities could significantly compromise dike integrity. Animal burrowing influences water pressures within flood protection embankments and weakens the soil layers, contributing to potential breaches. It is unknown/not thought through how these animal burrows should be included in the current national regulations/guidances on designing and examining the failure probability of levees (BOI). This due to the lack of knowledge on the full extent of the underground burrow systems within dikes and their impact on water pressures. Burrow entrances are readily observable along the slopes.
Witteveen+Bos started already with a method on how to model an animal burrow in 2D, including its impact on the cross-section failure probability on overtopping and slip circles. However, an (probabilistic) investigation is needed where the distribution of tunnels and chambers varies in 3D, so that the impact of animal burrows on trajectory-level is being investigated. This will be done for the dike reinforcement Zwolle-Olst.
Assignment
This project aims to evaluate the impact of animal burrowing on dike stability. Firstly, an extensive literature review will be conducted to identify the common locations and patterns of beaver burrowing activities. Next, the research will investigate the properties, geometry, and distribution of animal burrows to create a probabilistic framework to account for the weakened or damaged zones. The proposed methodology involves assessing the influence of animal burrows on water pressure and soil deformation within embankments during rainfall and high tide events using the finite element method (FEM). Various scenarios for the internal distribution of tunnels and chambers will be explored, which leads to an estimate of updated failure probability due to burrowing in 3D/trajectory-level. The findings will provide insights into the influence of animal burrowing on dike safety and offer recommendations for future analysis in similar cases.
Fig. 1: Beaver from excavated burrow in Hedel. Source: Rivierenland Water Board.
Learning goals:
- Collecting references on animal burrowing activities within dikes (especially 3D information, such as the burrow tunnel system)
- Formulating a systematic approach to represent chambers and tunnels within a dike, and especially the geometry of the 3D tunnel system.
- Incorporating damaged/weakened zones due to beaver burrowing within an FEM framework.
- Formulating an approach to incorporate the impact of animal burrows in the length effect factor (N) of dike trajectory failure probability.
- Investigating how the spatial variability of damaged/weakened zones impacts the failure probability of the dike trajectory.
Supervision
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