Chapter 2 

 INCIPIENT STABILITY OF BREAKWATER ARMOR UNITS 



2.1 Armor Stability Equations 



Extensive research on breakwater armor stability has produced many 

 empirical stability models. PIANC (1976) provides a summary of early stability 

 models based on regular wave experiments. PIANC (1992) provides a discussion of 

 more recent irregular-wave-based models. The most widely known empirical stability 

 model was developed by Hudson (1958, 1959), following the pioneering work of 

 Iribarren (1938) and is typically seen in the following form 



Y H^ 



W = 2-— (2.1) 



K^{S^-\f cotQ 



where 



W = weight of armor unit 



Yo = specific weight of armor unit material 



H = design wave height at structure toe 



Kq = tabulated empirical stability coefficient 



Sa = specific gravity of armor unit material 



6 = seaside angle of armor slope relative to horizontal 



6 



