*************** 



EXAMPLE PROBLEM 2************** 



GIVEN: Rubble-mound breakwater with quarrystone for armor; cot e = 2.5; 

 cot 3 = 80; dg = 18 feet (5.5 meters); H^ = 6 feet (1.8 meters); T = 5 

 seconds; kp = 2 feet (0.61 meter); h^ = 13 feet (4 meters). 



FIND: Wave runup (use one of the flow charts in Figs. 2, 3, or 4). 



SOLUTION : Since the structure is a quarrystone rubble mound, use the flow 

 chart in Figure 3 as follows: 



h -, „ h 



c 13 c 



(a) -T— = To" = 0.72 (i.e., -r— < 0.75; therefore, this structure 



s s 



has a low core) . 



d d 



(b) Hf= ^= 3 (i.e., "yes," ~r >- '^') ■ 



o o 



(c) Structure slope is cot 6 = 2.5 (i.e., "yes," cot 6 is between 

 1 . 5 and 5 ) . 



(d) Therefore, determine R/H' from Appendix E. 



d 



(e) For TjT - 2» use Figure E-1. 



o 



H^ 6 



(f) r— = y = 3. (This value is smaller than that used in Fig. E-1; 



T 



the smaller value indicates a larger stone size for a given wave height, 

 which would further reduce the runup from that given in Fig. E-1; thus, 

 runup predicted from Fig. E-1 may be considered conservative, i.e., as 

 larger or larger than the actual runup to be expected.) 



H' 



(g) -°~= = 0.00745. 



gT2 (32.2) (5)2 



D 



(h) From Figure E-1, with cot 6 = 2.5, -^ = 0.80. 



o 

 (i) From Figure 3, scale effect is k = 1.06. 



(j) Finally, from Figure 3, 



R = (0.8) (6) (1.06) 



R = 5.1 feet (1.6 meters) . 



14 



