Plates D-7to D-11 incl. - Graphic determination of the weight of cap stone 



in terms of wave height, side slope and slope 

 coefficient K' . 



These curves are graphic solutions of the Iribarren formula as modified 

 by Hudson for the determination of the side and end slopes and the weight 

 of cap stone, at those slopes, required to withstand various wave heights. 

 This modified formula is 



W - K' Y^ s3 S^ u3 h3 



(U COS a- sina)3 (Sj. - Sf)3 

 where W - weight of s tone in pounds 



K' ■ slope coefficient - see plate D-12 



Y„ ■ specific weight of fresh water 



Sf m specific gravity of the water (in sea water Sf ■ 1.03) 



Sj. s specific gravity of the stone 



U = effective coefficient - stone on stone s 1.09 



H 3 wave height at the structure 



a the angle the sea side slope makes with the horizontal 



In fresh water the formula reduces to 



i.3K' Sr h3 



W 



(U COS a -sin a )3 (Sj. - l)3 

 In ocean water it reduces to 



^ , 80.7 K' Sr h3 



(U cos a- sina)3 (S^. - 1.03)3 



The curves of plate D-12 show the variation of K' in the basic 

 equation with d/L and a . 



An example of the use of these curves follows! 



Given a breakwater founded in 30 feet of sea water under waves with a 

 height of 10 feet and a length of 200 feet at the structure composed of quarry 

 stone having a specific gravity of 2.6^, from Plate D-9, W/K' for a side 

 slope of 1 on 1,5 is 1.2^ X 106. From Plate D-12 with d/L s 0,l5 and a 

 slope of 1 on 1.5, K' equals 0.018, Therefore the size cap stone required 

 is 1.25 X 106 X 0.018 3 22,500 pounds or 11.2 tons. 



D"3h 



