Toe structure stability of rubble mound breakwaters

Abstract

In this report an analysis of data from a series of tests is presented on the stability of the toe structure of rubble mound breakwaters. The existing knowledge on toe stability and the influence of all governing parameters in the existing knowledge is reviewed. The tests which were performed for the present research are treated extensively. The main governing parameters, which determine toe stability in rubble mound breakwaters, are: Significant wave height : Hs Nominal stone diameter : Dn50 Stone mass density : ρ s Depth above the toe : ht Damage level : Nod Parameters investigated which appeared to have no significant influence are: the fictitious wave steepness sop and the width of the toe structure bt. The choice of the governing parameters, the definition of damage levels for the design of the toe structure and the way they are made dimensionless are motivated. The results from the present tests are compared with existing design formula. With the selected parameters two formulas have been derived from the available test data. One describes toe stability using the shallow water significant wave height Hs the other uses the shallow water 2% wave height H2%. The formulas are compared with existing test results and their range of application is given.