Residual dike strength after macro-instability - WTI 2017

The residual strength of dikes after an initial slip failure was investigated by considering the effect of erosion due to wave overtopping. The negative effect of erosion can be taken into account by an extra margin of 1.5 m of (crest) width for clay dikes, apart from the currently used spatial margins for secondary slip surface failures. The 1.5 m is recommended for existing clay dikes up to 1 I/s/m. For 10 I/s/m the margin for clay dikes increases rapidly (up to 7.9 m) and given the large uncertainties in this study it is not recommended to extend the margin for 10 I/s/m situations. It is recommended not to take into account residual strength for sand dikes overtopped by more than 0.1 I/s/m.