Hydraulic Stability of Randomly-Placed Rakuna-IV for Rubble Mound Breakwaters in Case of Non-breaking and Non-overtopping Waves Using Physical Models
In recent years, very large concrete blocks have been used for many coastal protection works, especially rubble mound breakwaters in deep-water areas. These concrete blocks have been being modified and improved in order to be well adapted to different wave conditions and to meet the increasing and diverse demands of the construction of deep-water ports and coastal protection works. Along with the structural integrity, the hydraulic stability of concrete blocks has also been considered an important issue for rubble mound breakwaters. Recently, there have been various severe failures of many breakwaters covered by the complex form of slender concrete blocks without reinforcement, which caused by the breakage and failure of these blocks when the stresses exceed the strength or mechanical durability of the material, especially when the concrete blocks rock, rotate and collide under wave impacts – which is known as rocking mechanism. This is a common phenomenon in case of double-layer and randomly-placed slender concrete blocks for the protection of rubble mound breakwaters.
As a general development trend in the world, Rakuna-IV is a new type of Japanese concrete block, which was invented by Nikken Kogaku in 2007 and has been applied to many breakwaters and coastal protection works. So far, no research has been made on the hydraulic stability as well as the structural integrity of concrete blocks in case of random placement and non-breaking waves for rubble mound breakwaters. This is an urgent practical issue when in most cases, especially in deep water, the concrete blocks for breakwaters are usually placed randomly during construction. This paper focuses on some results of the study on hydraulic stability of Rakuna-IV blocks in case of non-overtopping, non-breaking waves and random placement, using physical models.
Keywordsconcrete armour unit CAU rubble mound breakwater Rakuna-IV hydraulic stability physical model
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