Table 8. Values of r for a quarrystone 



rubble mound (after Jackson, 1968a) 



d s /H' 



%/*r 



Slope (cot 0) 



r 



5.0 



2.7 



1.5 (interpolated) 

 2.25 



0.52 

 0.51 



5.0 



2.45 



1.5 (interpolated) 

 2.25 



0.48 

 0.48 



Savage's data have a rather wide range of r values, with the high- 

 est values for the steepest structure slopes. The observed runup values 

 for the steep slopes are probably influenced by the rather short hori- 

 zontal distance along the SWL between the vertical end wall and the 

 structure slope. Flatter slopes have progressively smaller r values. 



A reversal in trends of the plotted lines in Figures 31 and 32 may 

 be a result of water particle motion differences for breaking and non- 

 breaking waves (on the structure) and also of differences between stand- 

 ing wave and surging wave effects for varying structure slopes. 



A value of r «0.50 to 0.55 appears conservative for a rubble-mound 

 structure (such as that tested by Jackson, 1968a) with the top of the 

 core approximately at the SWL. Lesser values of r appear justified, 

 usually, for a structure with low core height, such as tested by Hudson 

 (1958); a very steep structure slope (e.g., 1 on 1.25) may nevertheless 

 have high r values. Variations in H^/k^ will also affect the selec- 

 tion of an r value. A porous structure with an impermeable backing, 

 such as that used by Savage (1958), has considerable variance, with r 

 values ranging from r «0.87 for a 1 on 0.5 slope to t* 0.4 for a 1 on 

 10 slope. 



(2) Impermeable Structures . Test conditions of quarrystone 

 revetment runup experiments discussed here are given in Table 9. Cross- 

 sectional diagrams are shown in Figure 33. 



Saville (1962) conducted runup tests in a large wave tank with a 

 depth of 4.57 meters (Fig. 33). He tested riprap on a 1 on 1.5 slope 

 sited on a horizontal tank bottom. Armor layers of both one- and 

 three-stone thicknesses on a concrete slope were tested. Instability 

 problems on an impermeable base would be appreciable, particularly for 

 a layer one stone thick. Although Saville gives results for both armor 

 unit conditions, only the results for the layer three stones thick are 

 given here. Relative depth varied from approximately dg/H^ = 5.0 to 

 dg/Hp = 10.0, plus a few points at larger values; relative roughness 

 or stone size varied from H^/k r = 3.0 (at d^/H^ = 5.0) to U^/k p = 1.0 

 (at dg/H^ = 15.0). Saville's data, when compared to the smooth-slope 

 curves presented earlier, have values of r (averaged for several 

 values of wave steepness) as given in Table 10. 



73 



