NAMI RINGS 



Rings 



Filter 

 SECTION 



Nami ring revetment, Little Girl Point, Mich. 



Prototype Installation : 



Little Girl Point Park, Lake Superior, Gogebic County, Michigan. 

 Rings placed directly on filter cloth on 4- inch- thick sand bedding. 



Revetment slope 1 on 2. 



Design wave breaking 6.5 feet high, 5.5-second period. 



Construction completed in September 1974. 



Rings cost $8 each, revetment cost $1.50 per square foot 



(Moffatt and Nichol). 



Total project cost estimated at $18,860 for 300-foot- long revetment 



or $62.86 per foot (Brater, Armstrong and McGill, 1974). 



Wave Tank Tests : 



Nami rings tested at scales of 1:12.8, 1:14.7, and 1:18.6 in a 

 3- by 3- by 120- foot- long wave tank. 



Revetment slope was 1 on 2. 



These tests showed the rings were stable for a wave equivalent 

 to a prototype breaking height of 6.5 feet and a 5-second period 

 (Raichlew, 1973). 



Design Factors : 



Zero-damage wave height: 6.5 feet (model tests). 



Wave runup: 0.6 to 0.7 compared to smooth slope (estimated). 



Wave reflection: Moderate (estimated). 



Remarks : 



Rings are 1 foot high with a 2. 5- foot outer diameter, a wall thickness 

 of 3 feet, and weight of 265 pounds. 



Rings opening up to trap littoral drift, reduce uplift pressure, and 

 reduce runup. 



Backfilling rings would increase stability. 



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