PART IV: WAVE-INDUCED PRESSURES INVESTIGATION 



31. After completion of the overtopping study, wave pressure tests were 

 performed using the Phase II seawall geometry (model scale 1:19). The purpose 

 of these tests was to obtain pressure data necessary to determine wave-induced 

 forces and moments to which the wall would be subjected under certain storm 

 conditions. Ultimately, this information will be used in the completion of a 

 seawall and foundation design which can withstand expected wave forces and 

 ensure stability against overturning and/or sliding. 



32. Wave pressures were measured using miniature semiconductor pressure 

 transducers, each equipped with a silicon diaphragm and a 4-arm strain gage 

 bridge. Pressure measurements were calibrated and recorded using a DEC Micro- 

 VAX I computer. Typical time-histories of measured wave pressures (Figure 12) 

 indicate that as a wave approaches and strikes the face of the seawall, in 

 many cases, it causes an initial shock pressure of large magnitude and short 

 duration immediately followed by a secondary (or surge) pressure of lesser 

 magnitude and longer duration. Based on experiments conducted with a vertical 



PT53X1 CHI 



0.2 0.4 



TIME, SEC 



Figure 12. Typical wave pressure time-history 



28 



