(b) If the nearshore slope is 1:100 (m = 0.01), the maximum breaker 

 heights must be recomputed using the procedure of Section 7.122. 

 For a 6-second wave on a 0.01 slope the results of an analysis 

 similar to the preceding gives, 



Hfc = 6.3 ft. (d;, - 7.7ft.>d,), 



p = 6,050 Ibs./ft? , (T = 6 sec.) 



and 



R^ = 12,700 Ibs./ft. 



The resulting maximum pressure is about the same as for the wall 

 on a 1:20 sloping beach (p = 6,075 Ibs./ft.^); however, the 

 dynamic force is less against the wall on a 1:100 slope than 

 against the wall on a 1:20 slope, because the maximum possible 

 breaker height reaching the wall is lower on a flatter slope. 



************************************* 



7.332 Wall On a Rubble Foundation , The dynamic component of breaking 

 wave force on a vertical wall built on a rubble substructure can be esti- 

 mated with either Equation 7-76 or Figure 7-76. The procedure for calcu- 

 lating forces and moments is similar to that outlined in the example 

 problem of the preceding section. However, the ratio dg/D is used 

 instead of the nearshore slope when using Figure 7-76. Minikin's equa- 

 tion was originally derived for breakwaters of this type. For expensive 

 structures, hydraulic models should be used to evaluate forces. 



7.333 Wall of Low Height . When the top of a structure is lower than 

 the crest of the design breaker, the dynamic and hydrostatic components 

 of wave force and overturning moment can be corrected by using Figures 

 7-77 and 7-78. Figure 7-77 is a Minikin force reduction factor to be 

 applied to the dynamic component of the breaking wave force equation, 



R' = r R . (7-82) 



Figure 7-78 gives a dimensionless moment reduction factor a for use in 

 the equation 



K = d,R^ - (d. + a) (1-rjR^, (7-83) 



K = Rm Em (d.+a)-a]. (7-84) 



7-152 



