12 



The 200- to 2,000-lb toe and crest stone showed significantly improved 

 stability relative to the 200- to 1,000-lb stone used in previous plans. As 

 would be expected, a few of the smaller stones still were displaced. 



Plan 4R (Figure 7) was a rebuild of Plan 4. It was tested using the 16-step 

 storm (Table 5) at the -8.6-ft mlt toe condition to verify the stability response 

 of the concrete blocks. 



Test results at the +4-ft swl verified the movement observed during tests of 

 the previous plan, i.e., there was a slight seaward slippage of the toe blocks, 

 which allowed the next five rows of blocks above them to pack downslope. A 

 small amount of additional slippage of the seaward blocks was observed during 

 the +7.0- and +9.5-ft swl's. The +14-ft swl displaced four blocks downslope 

 during step 16 (Table 5 at the -8.6-ft mlt toe condition (Photos 15 and 16)). A 

 comparison of Photos 13 and 14 with 15 and 16 shows the repeat test pro- 

 duced results similar to the original; however, three more seaward blocks were 

 displaced. The structure did not fail; however, any displacement is cause for 

 concern with a one-layer armor system. Therefore, as with Plan 4, stability of 

 the concrete blocks is rated only marginally acceptable. The 200- to 2,000-lb 

 shore-side crest and toe stone performed similar to Plan 4; i.e., a few smaller 

 stones were displaced, but the overall stability of this material was good. 



Plan 5 (Figure 8) was similar to Plan 4 except it was assumed that the 

 erosion depth in front of the structure was 5 ft less (sea bottom was raised 

 from -8.6 ft mlt to -3.6 ft mlt). Also, the upper toe elevation was raised from 

 -5.0 ft mlt to -3.6 ft mlt. Plan 5 was subjected to the same 24-step test as 

 Plan 1 (Table 1). Testing at the +4-ft swl produced no movement of the con- 

 crete blocks. A few of the smaller 200- to 2,000-lb shore-side crest stones 

 were displaced. Two additional crest stones were displaced during continued 

 testing at the +7-, +9.5-, and +14-ft swls. No movement of the concrete 

 blocks could be detected at any of the swl's. Photos 17 and 18 show the 

 structure after wave attack. 



Plan 5R (Figure 8) was a rebuild of Plan 5. It was tested to verify the 

 stability response of the concrete blocks for the -3.6-ft erosion depth. Plan 5R 

 was subjected to the 16-step test listed in Table 6. Results verified the out- 

 come of the initial test, i. e., no movement of the concrete blocks was detected 

 at any of the swl's until the final step of the test was reached. The 10-sec, 

 13.2-ft waves at the +14-ft swl (step 16, Table 6) displaced one block from the 

 seaward face (Photos 19-21). Also, a few of the smaller 200- to 2,000-lb 

 shore-side crest stones were displaced at the +4- and +7-ft swl's. 



Plan 6 (Figure 9 and Photos 22-24) was similar to Plans 4, 4R, 5, and 5R, 

 except armoring was provided by 6.0-ton concrete blocks, 3.0-ft thick, 5.25-ft 

 wide, and 5.25-ft long (Figure 10). The blocks were uniformly placed with 

 their least dimension perpendicular to the slope. A 1.0-ft-long, 0.25-ft-wide 

 and 3.0-ft-deep indentation was formed in each side of each block (Figure 10). 

 The indentations served to increase the porosity of the block cover layer and 

 reduce the buildup of pressures beneath the blocks. It was also felt that the 



Chapter 3 Tests and Results 



