010 

 009 

 008 

 0.07 

 006 

 005 



fb' 



II II 





















Test Condition 

 Symbol Bag Length Bog Diameter Bag Fill Water Depth 



. 20' 13" 100% 4.5' 



X ?(V 13" 9 5% 4.5' 









J x 































•A X 



(/ X 













A 



20' 



13" 





90% 





4.5' 





> 



/ % 









— 

























































ft/ / 



X 

















A 



i 



i 



X 



X 



X 





X 





* 



/ X 

















X 





• 



X 

 X 









'x 





• M ■ Total Mooring Line Load in Pounds 

 H : • Incident Wave Height in Feet 

 L w ■ Incident Wavelength in Feet 

 y * Specific Weight of Water in Lbs./Cu.ft. 

 B • Frontal Width of Breakwater in Feet 

 d ■ Depth of Water in Feet 



Mooring Line Force Parameter, Md/yBH.L 



Figure 176. Mooring line force versus wave steepness for water-filled, 

 cylindrical bag floating breakwater (after Ripken, 1960b). 



b. Three-Dimensional Experimental and Field Studies. Wiegel (1959b), 

 Wiegel, Shen, and Wright (1960), Shen (1961), and Wiegel, Shen, and Cumming 

 (1962) conducted laboratory studies in a three-dimensional wave basin to 

 investigate attenuation and mooring characteristics of specially constructed 

 mattresses, 10 feet by 10 feet by 4 inches, to be used as a portable floating 

 breakwater. The advantage of such a structure is that it could be transported 

 to the site as a collapsed form in a roll, then unrolled, lashed to other sec- 

 tions, moored, and filled with seawater. The wave basin used in the study 

 was 64 feet wide (a sufficient width to remove any boundary effects from the 

 vicinity of the prototype-size bags). Uniform periodic waves were generated, 

 and the heights were measured both in front of and behind the mattresses. 

 The mattresses were fabricated with a material of specific gravity slightly 

 greater than 1, so plastic tubes were attached to the mattresses and filled 

 with air. The proportions of the volumes of the air-filled tubes and water- 

 filled mattresses were such that the system hovered in the water with its top 

 surface barely at the Stillwater level. 



Three different water depths (8, 16, and 24 inches) were used in the wave 

 basin, and either one, two, or three layers of mattresses were used with each 

 water depth. Because of the dynamic characteristics of the fluid in the mat- 

 tresses, a single mattress in 8 inches of water was found to be only a little 

 more effective than the same bag in deeper water. Since the ratio of water 

 depth-to-wavelength, d/L, is greater for a triple bag in 24 inches of water 

 than for a single bag in 8 inches of water; however, the single bag is rela- 

 tively more efficient than the triple bag. One phenomenon was evident in all 

 the tests: a multiple peak trough relationship existed between the ratio of 

 transmitted wave height-to-incident wave height, H t /H^, and the relative 

 breakwater width, L/W (Fig. 177). Laboratory observations indicated that 



236 



