11. For the above reasons, the dolos armor unit should economically 

 satisfy the armoring needs for many breakwater applications. Yet other CAU 

 shapes, such as the accropode and the tetrapod, may be more efficient in 

 certain circumstances. Although this report focuses on dolos design, it is 

 not the intention of the author to promote dolosse as the only rubble -mound 

 armoring solution. But the methods discussed herein provide a framework for 

 both designing slender concrete armor and comparing competing armor shapes. 



Obstacles to Development of Comprehensive CAU Design Methods 



12. After several breakwaters sustained massive and unexpected armor 

 unit breakage and subsequent armor layer unraveling during the 1960 's and 

 1970' s, new techniques for CAU hydrodynamic and structural design began 

 appearing in the literature. But comprehensive CAU design methodologies have 

 been slow to develop because of three primary factors: 



a. The multitude of different armor unit shapes spreads design 

 development efforts too thin. 



b. The structural and hydrodynamic physics are complex. 



c. The CAU design problem is unlike both typical coastal rubble - 

 mound design and conventional structure design. 



The following paragraphs discuss these items individually. 



Too many CAU shapes 



13 . The CAU engineering problem is so complex that formulation of a 

 viable design solution requires international research coordination, both for 

 technical reasons and because of funding limitations. But the large number of 

 different CAU shapes in use has limited worldwide research coordination, 

 resulting in sporadic progress in concrete armor unit design technology. The 

 fact that many of the armor unit shapes are proprietary has also restricted 

 coordinated research. Recent coordinated research concerning the dolos unit, 

 as described in this report, has resulted in the development of advanced 

 design methods. 



Complex physics 



14. The physics of the CAU design problem are complex in several 

 respects. First, the very nearshore waves and the highly turbulent breaking 

 or broken wave, as it flows into and runs up the face of a breakwater, are not 

 presently analytically solvable. Second, the randomly placed armor units 



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