^40. The structure was subjected to the 36 different water level-wave 

 condition combinations shown in Table 1 and the corresponding wave pressures 

 were recorded. A test duration of 30 sec was used, as discussed previously, 

 and the number of representative waves for which pressures were observed 

 ranged from 7 to 12 depending on the wave period. Results of the shock pres- 

 sure tests are given in Table 2. Figure 9 shows one of the more severe break- 

 ing waves impinging on the vertical seawall at an swl of 8.6 ft msl. 



41. One of the most noticeable characteristics of these data is the 

 variability in shock pressures for identical incident waves. The range be- 

 tween the minimum and maximum shock pressures, especially for the more severe 

 water level-wave conditions, was large. In order to provide a graphical pre- 

 sentation of the wave pressure profile for each of the 36 conditions, a repre- 

 sentative wave was chosen from the 7 to 12 available waves and plotted as 

 shown in Plates 8-25. These figures indicate, with few exceptions, that 

 maximum shock pressures occurred near the still-water level. The greatest 

 pressures occurred at +6.9 and +8.6 ft swl with wave periods of 12 and 14 sec. 



42. As expected, secondary pressures were much lower than the corre- 

 sponding shock pressures and there was less variability in the secondary pres- 

 sures for identical waves. Because of this consistency, the 7 to 12 secondary 

 pressures measured at each location, for each set of conditions, were averaged 

 and these data are presented in Table 3. The durations of the secondary pres- 

 sures were also relatively consistent at approximately 2.5 sec (prototype). 



Plan R4S2 Test Results 



43. Pressure transducers were mounted in the recurved seawall at ele- 

 vations of +22.0, +20.0, +18.0, +16.0, +14.0, +12.0, +10.0, +8.0, +1.0, -1.5, 

 and -4.0 ft msl. A profile sketch of this seawall and its 11 transducers 

 locations is shown in Figure 4. 



44. This structure was subjected to the same wave conditions used for 

 testing the vertical seawall, and test results are included in Table 4. Fig- 

 ure 10 shows a l4-sec, 11.4-ft wave impinging on the structure at an swl of 

 +8.6 ft. 



45. When compared with the corresponding shock pressures measured on 

 the vertical wall, the magnitudes of shock pressures were substantially less 

 with the recurved wall. Also, shock pressures recorded for consecutive waves 



23 



