ANSWERS: 



Weight of boulders needed per 1,000 square feet of revetment surface area: 



(^h 



l,000^ft2 = C (1,000) = C.F. y—j^'- wHl, 000/2, 000) 



= 0.55 (730/165)^/^(165) (-|^^ ) 



= 74.5 tons per 1,000 square feet. 



Weight of quarrystone riprap needed per 1,000 square feet of revetment 

 surface area: 



_S£iSg^. 0.43 (730/165)^/^165) (i^) ■ 

 = 58.2 tons per 1,000 square feet.. 



Conventional two layers of overlay have about the same zero-damage 

 wave height stability as the 100-percent overlay. Therefore, a conven- 

 tional two- layer overlay W50 = 730 pounds. From Figure 7: 



C.F. = 0.95 quarrystone riptap for two layers 



C.F. = 1.15 boulders for two layers 



Quarrystone .^^^.1/3 .^ . 



riprap weight = 0.95 ^^ 165 ^^^^^^j 



= 128,7 tons per 1,000 square feet. 



Boulder weight = 1.15 (gi)''S65 (MOO) 



= 155.8 tons per 1,000 square feet. 



SUMMARY: 



Overlay Overlay W^q for Overlay 



(lb) 



zero-damage Hg = 5 ft (tons per 1,000 ft^) 



730 



74.5 



730 



58.2 



730 



155.8 



730 



128.7 



100-percent boulders 



100-percent quarrystone riprap 



Boulders 



Quarrystone riprap, two layers 



If unit prices for boulders and conventional quarrystone riprap are avail- 

 able, an economic comparison can be made. 



34 



