and weichts of individual stones above the water surface. Ills result for 

 the cslculation of the weight of cap rock, in wide use for sorae vears, is 



r 



(cos a - sin a) (S - l)""' 



09) 



whei-e 3 = specific gravitv of the rock 



a = the angle the slope malces with the horizontal 



(A slope is usually referred to as l/cot a) 

 II = wave height (in feet) 

 W = weight of stone (in tons) 



K = 3J1 erapiricallj deterinLned coefficient for all 

 unevaluated variables 

 * I1..68 X 10~^i- for natural rubble 

 = 5.93 X 10-^t for artificial blocks 



This equation hoi-rever, is not diriiensionaIl.ly homogeneous and has been Liodified 

 by Hudson, using the sano assur.-otions an-i force diagram as Iribarren to 

 obtain 



3 3 3 



W = iL^--J_ ^ (1^0) 



((J. cos a - sin a)"" (3 - S-)"^ 



in which the additional syiabols are: 



Y - unit weight of fresh water 



S„ = specific gravity of the fluid in which the breala-rater 

 is located 

 |jL = effective coefficient or fric+.ion rock on rock, 



ir 1.09. 



K' = a variable dinensionless eirpirically deterniined 

 coefficient, values of wliich as deterroined by 

 Hudson are plotted in Figure 12, Appendix D> 



the equivalent values from equation (39) are 



K' =» 0,015 for natural rubble 



K' = 0.019 for artificial blocks. 



^23. The Equations for the Iffeight of Above Surface Stones . - Equation 

 (I|.0) may be reduced to 



88.3 K' 3 :I-I^ 



W = ^—:r ^ (III) 



(1.09 cos a - sin a)-^ (3 - 1,03)-^ 



113 



