EXPERIMENTAL STUDY ON STABILITY OF ARTIFICIAL REEFS WITH HIGH CROWN HEIGHT

Abstract

 There are few research cases of stability of high-top artificial reef although there are some previous studies in the case of coated blocks. In the case of high top artificial reef whose crown height is as high as the design high tide level, wave power caused by the impact of waves and flow caused by wave breaking and return flow on the dyke are thought to affect the stability of the dyke. Therefore, it is unclear whether stability can be evaluated by a desk study such as Hudson’s formula because of complicated wave/flow field compared to general breakwaters and artificial reefs.

 In this study, two-dimensional hydraulic model experiment was conducted to analyze the damaged patterns of the high-top artificial reef, which have very few cases of study, and to examine the stability of the dyke stability. The results shows that (1)there is a risk that the stability of the block could be impaired due to the damage on the offshore shoulder of the rubble mound, although the focus is on the required block mass in the desk study of stability of offshore wave-dissipating facilities, (2)although the damage patterns of the high-top artificial reef was damaged by both pushing and pulling waves, it was often damaged by the pulling waves, and necessary mass of the block was larger than the required mass calculated by Hudson’s formula, (3)in case of installing high-top artificial reef by random stacking of blocks, radial type blocks may be more stable than legged shaft type blocks, (4)considering this experiment and previous studies, the most dangerous condition for the stability of artificial reef is when the crown height and the tide level are equivalent.