where F and F^ are the wave force when the crest and trough are at the 



structure respectively, and w is the specific weight of the water 



(64 pounds per cubic foot (10,000 newtons per cubic meter) for seawater) . 

 Therefore, 



F^ = 1.14(wd2) = 1.14(64)(10)2 



= 7,300 pounds per foot (106,500 newtons per meter) 



and 



F^ = 0.38(wd2) = 0.38(64)(10)2 



= 2,400 pounds per foot (35,000 newtons per meter) 



Similarly, from SPM Figure 7-71, the maximum and minimum overturning irfoments 

 are 



M^ = 0.64(wd^) = 0.64(64)(10)3 



= 41,000 foot-pounds per foot (182,400 newton meters per meter) 



M^ = O.lKwd^) = 0.11(64)(10)^ 



= 7,000 foot-pounds per foot (31,100 newton meters per meter) 



where M and M^ are the overturning moments caused by the waves when the 

 crest and trough are at the structure. 



To determine the distribution of force along the groin, the appropriate 

 cnoidal wave profile must be found. Calculate 



h 32.2 



and 



I = 0.78 

 d 



which is the limiting value of H/d. From SPM Figure 2.11 for the calcu- 

 lated values of T /g/d and H/d, find the value of k^ = 1 - 10" ^^. From 

 SPM Figure 2-12 with k^ = 1 - 10"^'^, find 



^ = 240 

 d 



The wavelength, L, is therefore 



L^ = 240 4^= 240(10)^ 3Q^^^0 

 L = 175 feet (53.3 meters) 



12 



