Wi5 max = 0-75 ^^q rrdn (7-137) 



Wi5 mln = 0-31 W50 min (7-138) 



If stone is placed above water, the layer thickness is 



. ^50 min V' 

 r = 2.1 I -^^^^^ ) , or 0.3 m (12 in.) minimum (7-139) 



If stone is placed below water, 



/% rrrinV/^ 

 V = 3.2 (-^i^^ J , or 0.5 m (18 in.) minimum (7-140) 



to account for inaccuracy in placement. 



Equations (7-133) through (7-138) are used by choosing a layer thickness 

 for a type of placement, then calculating the dg for W^ ^^j (d^ mtn^ ^^^ 



for W^p. ^fi^j^ (d^ max^ ' ^'^^ local boundary shear should be calculated using 



d^ max ' ^^^ design shear should be calculated using d^ ^^ . If the design 



shear matches or exceeds the local boundary shear, the layer thickness and 

 stone sizes are correct. 



For uniform stone, d„ is uniform so that the same value is used for 

 calculating the local boundary and design shears. In the special case where 

 the velocity is known within 3 meters of the surface of the revetment, the 

 local boundary shear equation for velocities near the revetment surface can be 

 used with y set equal to dg . This gives 



'b^T 



^5.75 log^Q 30 



Setting this equal to the armor stone design shear, and solving the result 

 for V gives 



or 



V . 5.73 (0.020)"^ los,„ 30 C2s,'/^ f^^)"' fl- ^^ ^."' 



7-252 



