Stability of a single top layer of cubes
datasetposted on 30.06.2013, 00:00 by R.V. (Robin) Van Buchem
All conclusions in this thesis have been based on model tests, in which the cubes were placed by hand and placed in a stretching bond (half-steensverband). In total eighteen tests were performed in the wave flume of the Fluid Mechanics Laboratory of the Faculty of Civil Engineering and Geosciences. Two different slopes were tested together with three different packing densities and three different wave steepness. It was found that the gentler slope did not contribute to the stability in this setting using a stretching bond. In fact the model failed earlier than the model with a steeper slope in most cases. The best results were found using a slope of cotα = 1.5. Secondly, the influence of the packing density showed varying failure mechanism. When applying a large packing density (np = 0.20) the damage occurred below SWL. Contrary to small packing densities (np = 0.35) where damage occurred higher than SWL. It was found that, from the tested packing densities, a packing density of 0.28 gives the best results for both slopes. This conclusion is conform the findings of previous tests [Van Gent et al, 1999]. During these tests an optimum packing density of np = 0.25 – 0.30 was found. Although the cubes were placed randomly in the tests of Van Gent. In this study the cubes were placed in a stretching bond. Finally it was found that a wave steepness of s0p = 0.04-0.05 causes minimum stability for the armour layer. The tests with a single armour layer of cubes placed in a stretching bond indicated that high stability numbers (Hs/ΔDn) can be reached before failure occurs (Nod > 0.2). the tests show that stability numbers as high as 4.5 can be realized before Nod > 0.2 is reached.