The effect of wave grouping on on-shore structures

Abstract

This paper represents a contribution to the current discussion on whether model tests in waves should be carried out with waves which are, both in time and frequency domaine, reproduced in accordance with field records (and thus conserving the succession of the waves) or whether irregular waves generated solely in accordance with an energy spectrum obtained from field data can be used. To investigate the importance of the succession of waves to the impact on coastal structures, run-up/down on permeable and impermeable slopes and stability of dolos armour were investigated in model tests by using three different wave patterns. A significant influence of the succession of waves is demonstrated. A jump in wave height seems to be a very important wave pattern which should be included in the analysis of wave grouping. Also the importance of wave period and wave steepness to the relative run-up/down and to the stability of dolos armour is shown. A proposal to establish a set of universal graphs for the stability of dolos blocks (or any other “interlocking” blocks) is made.