of the same conditions appeared to be less variable. Again, representative 

 waves were chosen for plotting typical pressure distribution profiles. These 

 profiles are shown in Plates 26-41. Those wave conditions for which there is 

 no pressure distribution profile yielded negligible pressure records. The 

 profiles indicate that maximum shock pressures occurred in two particular 

 areas on the face of the seawall. One of these areas was near the swl, as had 

 been observed with testing of Plan R4S1. The other region where maximum shock 

 pressures occurred was near the top of the wall, in the area of the smaller 

 radius of curvature. Again, the greatest shock pressures were observed at 

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



46. Results indicate that the recurved seawall did not significantly 

 alter the magnitudes of durations of the secondary pressures when compared 

 with results of the vertical seawall. Typical secondary pressures for the 

 more extreme conditions were approximately 5.0 psi or less with durations of 

 approximately 2.5 sec (prototype). The average values for the secondary pres- 

 sures on the recurved seawall are listed in Table 5. 



Plan R4S3 Test Results 



47. After pressure tests had been performed and analyzed for Plans R4S1 

 and R4S2, the most severe water level-wave condition combinations had been 

 established; therefore, upon initiation of tests with the modified recurved 

 seawall, some of the less severe conditions were eliminated from the testing 

 sequence. Also, pressures on the cutoff wall were not measured with 



Plan R4S3, as it was assumed that these pressures would not be significantly 

 changed by modifications to the top of the seawall. It was also assumed that 

 forces might be quite large on the underside of the 2-ft overhang, due to the 

 role of the overhang in blocking wave runup along the face of the seawall. 

 Therefore, a transducer was mounted vertically in the overhang section. Fig- 

 ure 5 is a profile sketch of the seawall and transducer locations. A view of 

 the instrumented face of the modified recurved seawall is shown in Figure 1 1 . 



48. Results of this test series are presented in Table 6 and Plates 42- 

 52. These results indicate no significant change in the intensity or duration 

 of wave pressures on the seawall face, when compared with corresponding mea- 

 surements from Plan R4S2. However, the vertical transducer mentioned above 

 did record some relatively large shock pressures, the greatest being 75.25 psi 



26 



