Table 7 



Design Stone | 



Period 

 Sec 



10-Year Water Level 



50-Year Water Level 



100-Year Water Level 



Ht 

 ft 



ft 



W 

 tons 



ft 



ft 



W 

 tons 



ft 



Ft 



W 

 Tons 



3.5 



13.1 



10.6 



7.7 



14.3 



11.5 



10.1 



14.7 



11.9 



11.0 



4.5 



13.1 



10.6 



7.7 



143 



11.5 



10.1 



14.7 



11.9 



11.0 



5.5 



13.9 



11.3 



9.4 



14.3 



11.5 



10.1 



14.7 



11.9 



11.0 



6.5 



15.7 



12.7 



13.3 



16.5 



13.4 



15.7 



17.1 



13.8 



17.2 



7.5 



16.4 



13.2 



15.2 



17.9 



14.5 



19.8 



17.8 



14.4 



19.7 



8.5 



17.9 



14.5 



20.0 



18.6 



15.1 



22.4 



19.2 



15.5 



24.6 



9.5 



18.3 



14.8 



21.2 



19.6 



15.8 



26.0 



20.2 



16.3 



28.6 



10.5 



186 



15.1 



224 



20.3 



16.4 



29.2 



206 



16.7 



30.3 



11.5 



19.1 



15.5 



244 



20.9 



16.9 



31.7 



21.0 



17.0 



32.0 



12.5 



19.3 



15.6 



25.0 



20.9 



16.9 



31.7 



21.6 



17.4 



34.8 

 1 1 



Where breaking did not occur seaward of the groin for the 1 7.4-, 19.0-, and 

 19.6-ft depths, shoaling and refraction coefficients were calculated assuming 

 straight and parallel bottom contours and using three directions of incidence — 

 45 deg (from the northeast), 1 08 deg (slightly south of due east and the direction 

 of largest wave from WIS Station 72), and 135 deg (from the southeast). Similar 

 to the //„,.„ -to-///o procedure used for breaking waves, the transformed non- 

 breaking waves were converted to an H„Sor use in Equation 4 along with Kq = 

 2.8 and cot^ = 2.0 for nonbreaking waves and structure side slopes of 1 :2. 



Physical model tests have been conducted to characterize rubble-mound 

 structure damage for exposure to waves larger than the design height. These 

 relationships can be consulted to estimate the amount of potential damage that 

 may occur if stones smaller than that specified by the design wave are used. 

 SPM (1984) provides a table relating wave-height ratio to percent damage. The 

 wave-height ratio is the wave height corresponding to some damage D over the 

 zero-damage wave height (///, = 0). Percent damage is defined as the volume of 

 armor units displaced from the structure between the center line of the structure 

 crest width to one zero-damage wave height (///)= 0) below the still-water level 

 per unit length of structure. 



Solving Equation 4 for //and forming a ratio for two wave heights result in 

 Equation 5. To determine the damage level, let H, be the zero-damage (design) 

 wave height corresponding to the zero-damage (design) weight W,. The quantity 

 H: is the smaller wave height for which zero damage occurs and gives the weight 

 of the available stone, W^. The //////^ ratio for specific damage levels is found in 

 SPM (1984). Equation 5 can then be solved for W: given the zero-damage 

 weight Wi and percent damage wave-height ratio. The stone weight 



Chapter 4 Structure Design 



45 



