a. Minikin Method ; Breaking Wave Forces « Minikin (1955, 1963) developed 

 a design procedure based on observations of full-scale breakwaters and the 

 results of Bagnold's study. Minikin's method can give wave forces that are 

 extremely high, as much as 15 to 18 times those calculated for nonbreaking 

 waves. Therefore, the following procedures should be used with caution and 

 only until a more accurate method of calculation is found. 



The maximum pressure assumed to act at the SWL is given by 



■m 



. 101w^^(D + d,) 



(7-85) 



where p^ is the maximum dynamic pressure, Hi^ is the breaker height, d 

 is the depth at the toe of the wall, D is the depth one wavelength in front 

 of the wall, and Lr, is the wavelength in water of depth D . The 

 distribution of dynamic pressure is shown in Figure 7-99. The pressure 

 decreases parabolically from p^ at the SWL to zero at a distance of % /2 

 above and below the SWL. The force represented by the area under the dynamic 

 pressure distribution is 



R = 



m 



P H, 



^m b 



(7-86) 



i.e., the force resulting from dynamic component of pressure and the over- 

 turning moment about the toe is 



"^ (7-87) 



M = R d = 



m m s 



i,e., the moment resulting from the dynamic component of pressure. The hydro- 

 static contribution to the force and overturning moment must be added to the 

 results obtained from equations (7-86) and (7-87) to determine total force and 

 overturning moment. 



SWL 





■>,^^^,^^' "Dynamic Component 

 \ Hydrostatic Component 



X 



Combined Total 



w{ds+^) 



Figure 7-99. Minikin wave pressure diagram. 



7-181 



