I . I 1 . I 



1 11 iM in u>t*ri"i i i»i (Rj.f 





Figure 26. Articulated armor unit revetment (photo 

 courtesy of Marine Modules Inc.). 



flexibility is required, timber wales have been used. Permeable- type 

 concrete groins have been built in the past that permitted the passage of 

 sand through the structure but are not used at present. In low wave climates 

 grout-filled bags are also used as an installation convenience; the bags, 

 usually plastic, deteriorate leaving the small concrete shapes as protection 

 of the groins. 



d. Jetties and Breakwaters. In exposed locations, jetties and break- 

 waters are generally some variation of a rubble-mound structure containing 

 concrete either as a binding material to hold rock together or as separate 

 elements of breakwaters having a heavy weight as well as energy absorption 

 characteristics. Some types of jetties are illustrated in Figures 28 and 

 29. In less severe exposures, both cellular steel and concrete caissons 

 have been used. In low wave climates grout filled bags are used. 



Where rock armor units in adequate quantities or size are not econom- 

 ically available, concrete armor units are used. Also, concrete sheet 

 piles are sometimes used as core for jetties. Figure 30 illustrates the 

 use of Quadripod armor units on the rubble-mound jetty at Santa Cruz, 

 California. Figure 29 illustrates the use of the more recently developed 

 dolos armor unit where 374- and 383-kilonewton (42 and 43 ton) dolosse were 



51 



