stability Tests 



27. Thirty plans were tested for 90-deg wave attack (wave direc- 

 tion 1), and two of these were also tested at a 67.5-deg angle (wave direc- 

 tion 2). The sponsor initially stated that the existing underwater slopes 

 would not be dressed, nor would material be removed to make better seating for 

 the dolos overlay and/or toe. (It was planned to lay the dolosse on whatever 

 slope and material presently exist.) This limited the initial design alterna- 

 tives to special toe placement, varying geometry, and area of coverage (this 

 alternative was somewhat limited due to cost). After the initial design al- 

 ternatives were found to be inadequate, trenching and buttressing were tried 

 with improved results. The abbreviated hydrograph (Table 1) was used for ini- 

 tial testing, and damage to the test structures was determined by observation. 

 Details of the plans tested and general results follow. 



Development of stable sections 

 for a 90-deg angle of wave attack 



28. Plan 1 (Plate 6 and Photos 7-10) was constructed with the toe of 

 the rehabilitation dolos 98 ft from the outer edge of the cap. A total of 

 177 dolosse were used. Damage to the structure was severe, and the entire 

 toe area was displaced. Damage originated at the toe, and as the toe units 

 were displaced the units upslope unraveled. The dolosse flukes extended 

 above the still water level (swl) at the toe of the rehabilitation area for 

 all water depths. Therefore, it was decided that the toe of the dolos would 

 have to be placed in deeper water to remove it from the high wave energy 

 region around the swl. Photos 11-14 show the structure after testing. 



29. Plan 2 (Plate 7 and Photos 15-18) was constructed with the toe of 

 the rehabilitation dolos 160 ft from the outer edge of the cap. A total of 

 381 dolosse were used. The toe units in the left (shoreward) transition and 

 central areas were stable; however, there was severe damage to the toe units 

 in the right (seaward) transition area. The damage was occurring at the swl, 

 and as the water depth was increased the damaged area moved upslope. Because 

 of the geometry of the breakwater (i.e., the dogleg), wave energy is concen- 

 trated in this area and problems were expected in this region. Photos 19-21 

 show the structure after testing. 



30. Plan 2A (Plate 7 and Photos 22-23) was the same as Plan 2, except 

 that the toe units in the seaward transition area were placed with their 



14 



