period r„. Van der Meer noted that 5 = 2 in Equation 3. 1 provides a good estimate of 

 the initiation of damage and that failure occurred when 5 = 8 for structure slopes of 

 1V:1.5H and 1V:2.0H, where failure was defined as exposure of the underlayer through 

 a hole D„5o in diameter. Van der Meer used test durations of 1,000 and 3,000 average 

 wave periods. Virtually all of his tests were performed with nonbreaking waves. Van 

 der Meer performed eight tests with depth limited waves and eight more where perhaps 

 only the highest waves in the distribution were depth limited. Based on these data, he 

 proposed breaking-wave-induced stability after N^^ waves could be determined by the 

 following equations. 



For plunging waves: 





H,^ 





2% 



= 1.4 (6.2) P 



^nSO 



and for surging waves: 





^2.. 



= 1.4P-'''3 



^nSO 



N 



--0.5 



L (3.7) 





\/coteC (3.8) 



where 



i?2% = wave height exceeded by 2 percent of waves in wave height 



probability distribution, where Van der Meer assumed Hj^^ = 1.4 //, 

 to obtain Equations 3.7 and 3.8 from his formulations for 

 nonbreaking waves at toe of structure 



A = (5g - 1) with S„ = specific gravity of armor unit 



P = permeability coefficient 



6 = structure slope angle 



47 



