The structure was rebuilt and retested with the following results: 



Step 



H mo ,H 



Cumulative Number of Stones Displaced 



Lakeside 



Harbor Side 



1 



15.6 



1 



10 



2 



17.2 



1 



18 



3 



18.6 



2 



25 



4 



19.9 



3 



28 



5 



21.0 



4 



30 



6 



22.4 



8 



33 



7 



23.1 



8 



33 



A comparison of the tabulated damages and the after-testing photos 

 (Photos 6 and 7 after the initial test and Photos 8 and 9 after the repeat test) 

 show the structure exhibited a higher level of movement in the repeat test. 

 Results of this type are not necessarily unusual and generally reflect random 

 differences in building that occur from one model structure to another and 

 from one section to another in the prototype breakwater. Model damage 

 patterns appear consistent with the prototype, with most of the damage 

 occurring on the harbor side. 



The threshold of instability is generally defined as the point at which 

 2-3 percent of the armor units are displaced from their original areas. The 

 3-ft-wide model section required about 450 and 200 armor stones on the 

 lakeside and harbor side, respectively. Thus, displacement of more than 12 

 lakeside or more than 6 harbor-side armor units could be considered the onset 

 of instability. Following this logic, Plan 1A1 would be considered stable for 

 wave heights through 19.9 ft on the first test and a wave height somewhat less 

 than 15.6 ft on the second test. 



Rationale for Plan 1A2 



A review of prototype photos revealed that, in some areas of the structure, 

 armor stones were placed more randomly than they were in Plan 1A1. 

 Therefore, it was decided that additional stability tests should be conducted 

 with this more random configuration to quantify its effects. Thus, Plan 1A2 

 (Photos 10-12) was conceived. Plan 1A2 was identical to Plan 1A1, except 

 that the armor was placed in a totally random manner. 



Stability tests of Plan 1A2 



Stability test results for Plan 1A2 were as follows: 



Chapter 3 Tests and Results 



