In the Netherlands dikes protect land from flooding by the numerous rivers flowing through. Since the introduction of a new method of dike assement and design (WBI2017/OI2014) dikes in the Netherlands are designed with higher volumes of overflow. The methods and models to asses macro-instability and micro-instability were designed for dikes with low volumes of wave overflow, which means the effect of wave overflow on macro and macro-instability is partly unknown. This leads to conservative designs. Especially in sandy dikes high saturation leads to a strong loss in strength, because of two reasons:
- Dike saturation due to overflow can occur quite quickly in, as water can infilitrate into the dike core easily. Clay dikes are less permeable thans sandy dikes.
- Once slope instability occurs sandy dikes are very sensitive to erosion due to overflow.
Assignment
Possible directions:
- Understanding the interaction between dike saturation and wave overtopping (geohydrology)
- How much water will infiltrate the dike and how much saturation will occur.
- Which aspect affect dike satuarion
- Probabilistic assessment of wave overtopping, macro stability and micro stability
- What is de probality
- What is the probability of failure?
- Modelling residual strength after initial mechanisms (macro stability/Micro Stability)
- How much residual strength is left after the initial failure of the slope?
Fig. 1: Finite element analysis of dike deformation after the occurrence of a primary failure surface.
Learning goals:
- Understanding dike and water level conditions where micro- and macro-instability interact
- Developing a systematic approach to represent micro-instability failure after slip surfaces (or damages) due to macro-instability has formed within an FEM framework
- Evaluating the residual strength of dikes
- Assessing the risk of dike failure due to micro-instability after macro-instability has already occurred
