EROSION AND OVERTOPPING OF A GRASS DIKE LARGE SCALE MODEL TESTS

G.M. Smith, J.W.W. Seijffert, J.W. van der Meer

Abstract


A comprehensive test series at full-scale was performed on a grass dike to obtain quantitative information on the wave loading, erosion rate, residual strength and overtopping under design storm conditions. The purpose was to establish design and assessment criteria for this type of dike, which exists in many places in The Netherlands. The particular dike tested exhibited, in general, a considerable resistance to erosion. However, such a non-homogeneous surface is subject to weak spots which can erode very quickly. The most critical region, where the wave loading is the highest, has been identified. The residual strength of the underlying layer of clay is defined as the time it takes for erosion to progress through the entire layer and expose the sand core of the dike. For the dike tested, the residual strength of the 0.8 m thick clay layer is estimated to be 10 hours under design conditions. Measurements of the average overtopping rate and the volumes per overtopping wave were compared to existing formulae, developed from the results of small-scale tests. The comparison was favourable, indicating that scale effects are not substantial for these quantities.

Keywords


dike; grass dike; erosion; overtopping; model test

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