The correlation coefficients for Equation 6.2 were r = 0.99 for all three series. Equation 

 6.2 indicates E/S°'^ is approximately constant. This implies that the average shape of 

 the eroded area remains approximately constant during damage progression. Figure 6.3 

 and Equation 6.3 suggest that the variability of eroded depth increases rapidly with 

 damage and becomes approximately constant at 5 = 4. The variability in eroded depth 

 decreases somewhat as the damage approaches the failure level of the armor layer. 



The eroded length L along the slope depicted in Figures 5.15, 5.17, 5.22, 

 5.23, 5.26, and 5.27 is analyzed in the following. The mean eroded length ^ is simply 

 defined as ^ = 2A^ Id^, corresponding to a triangular shape. The normalized eroded 

 length Z = 4 /^„5o is then given by X = IS IE, as shown in Equation 5.5. From the 

 measured values of 5 and E, the corresponding values of L are calculated to examine 

 the variation of L during damage progression. Figure 6.4 shows all calculated values of 

 L for the three series against the corresponding values of S. Figure 6.4 also shows the 

 following relationship derived from Equations 6.2 and 5.5 



Z =^A■M ■ <«■'*) 



The correlation coefficients for Equation 6.4 were r = 0.98 for Series A' and r = 0.99 for 

 Series B' and C. As an example of the use of Equation 6.4, for 5^ = 13 at failure for 

 Series A', Equations 6.2 and 6.4 yield ^'^ 1.7 and L = 16, implying the average 

 damaged profile at failure extends 16 stone diameters along the slope. For the model 

 structure with D„^q = 3.64 cm shown in Figures 4.2 and 4.3, this damage extent 



113 



