STABILITY OF PLACED BLOCK REVETMENTS IN THE WAVE RUN-UP ZONE

Abstract

Placed block revetments are constructed to withstand the wave forces on dikes, especially in regions where rip rap is not locally available, such as the Netherlands. The blocks are placed adjacent to each other on a filter layer to form a relatively closed and smooth surface, which is easy to walk on. The present research is about the stability of block revetments under wave attack. It focusses on the stability in the run-up zone (above the stil water level, SWL) and compares this with the stability in the wave impact zone (below SWL). To obtain practical design formulae both small-scale and large-scale tests have been analysed, in combination with theoretical considerations based on the leakage length theory. Two types of hydraulic load are considered: a wave front that rushes up the slope (like a bore), and high velocity flow in the run-up and run-down. The later is especially an issue for revetments in which blocks are sticking out among adjacent blocks due to lack of maintenaince.