'■"'k 



%D(U 



("d) 



[S^(H/H^-1)] 



(14) 



where 



7oD(H/H.) = damage experienced by a particular armor type from an 



incident wave height H , given a design wave height H^ 



7oD(Hj) = level of incipient damage detectable in the model tests 



which identifies the damage trend for a particular armor type 

 (i.e. when H/H^ = 1) 



S = an empirical coefficient fit to the scale model test results 

 for a particular armor unit type 



61. A higher S coefficient means that an armor unit type experiences 

 higher damage levels for the same increase in H . Table 3 gives the values 



Table 3 

 Coefficients for Analytical Prediction of Breakwater Damage 





Armor 

 Unit Type 



Wave 

 Condition 



Nonbreaking 



3.0 



Sr 



Data Source 



Quarrystone 



6.95 



Jackson (1968a) 



(rough) 











Quarrystone 



Breaking 



2.0 



3.65 



Carver and 

 Dubose (1985) 



Quadripods 



Nonbreaking 



3.0 



6.00 



Jackson (1968a) 



Tribars 



Nonbreaking 



3.0 



4.87 



Jackson (1968a) 



Dolosse 



Nonbreaking 



2.0 



1.68 



Carver and 

 Dubose (1985) 



Dolosse 



Breaking 



2.0 



3.55 



Carver and 

 Dubose (1985) 



for ^D(H. ) and S found for the armor unit types which have been tested 

 at WES. These coefficients may be used with caution in Equation 14 to pre- 

 dict breakwater damage. The variation in ^D(H,) between armor unit types 

 reflects improvements in the accuracy of damage measurements as well as dam- 

 age trends which may be related to armor unit characteristics. One or more 

 statistical outliers representing more severe damage than predicted by Equa- 

 tion 14 (presumed to have been caused by weaknesses other than hydraulic sta- 

 bility) were excluded from the analysis of data for each armor type. The dam- 

 age predicted by Equation 14 at selected levels of design wave exceedance and 

 the associated upper 95 percent statistical confidence limit are presented in 



39 



