tests*, conducted at WES in 1958, revealed that two layers of randomly placed 

 tribars on the head and one layer of uniformly placed tribars on the trunk 

 were the best methods of rehabilitating the storm damaged structure. A survey 

 in 1975 revealed extensive tribar breakage, and later it was found that the 

 toe buttressing stone recommended for placement at the toe of the one layer of 

 uniformly placed tribars had not been incorporated into the construction 

 specifications. It was surmised that in the absence of these buttressing 

 stones the tribar toe slid on the hard bottom which resulted in an en masse 

 slippage and breakage of several tribars. This area was rehabilitated with 

 two layers of randomly placed 11-ton dolosse onslope and through the use of 

 special placement of the toe dolosse. This latter work was also model-tested 

 at WES.** 



11. A repair similar in design to that used on Nawiliwili in 1959 was 

 completed on the Hilo Harbor Breakwater, Hawaii, Hawaii (Figure 2), in 1981. 

 One layer of uniformly placed 7.5-ton tribars was placed on the sea-side slope 

 of the breakwater between sta 11+00 and sta 20+00. Based on knowledge gained 

 through the failure of the Nawiliwili tribar section, a row of 8- to 12-ton 

 buttressing stone was incorporated into the toe repair. No design guidance is 

 presently available to aid in sizing the buttressing stone for an incident 

 wave environment, and no model tests were conducted. For this reason, close 

 monitoring of the repair work should be carried out after storm events. Thus, 

 POD and the Corps as a whole will gain from prototype experience which can be 

 used to complement the data acquired during the experimental model tests on 

 toe buttressing stone design proposed to be carried out under this work unit. 



12. Haleiwa Harbor, located on the north side of the Island of Oahu, 

 Hawaii (Figure 3), was modified in 1975 by the addition of a revetted mole and 

 two stub breakwaters. Subsequent to this time, repairs were required on the 

 80-ft breakwater due to a slippage failure of the primary armor stone. Close 

 inspection of the structure revealed that the bedding and berm had been 



* R. A. Jackson, R. Y. Hudson, and J. G. Housley. 1960 (Feb). "Design 

 for Rubble-Mound Breakwater Repairs, Nawiliwili Harbor, Nawiliwili, 

 Hawaii," Miscellaneous Paper No. 2-377, US Army Engineer Waterways 

 Experiment Station, Vicksburg, Miss. 

 ** D. D. Davidson. 1978 (Jan). "Stability Tests of Nawiliwili Breakwater 

 Repair," Miscellaneous Paper H-78-4, US Army Engineer Waterways Experi- 

 ment Station, Vicksburg, Miss. 



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