I am looking at designing countermeasures for scour at a vertical wall bridge abutment. I am looking at the equations in Hec 23 and I am a little confused. There are 2 equations to determine the required D50 of the rip rap. If the Froude number is less than 0.8 then this equation is to be used:
D50/y = (k/(Ss-1))*(v^2/gy)
if the froude number is greater than 0.8 then this equation is used:
D50/y = (k/(Ss-1))*(v^2/gy)^0.14
These 2 equations give very different results because of the ^0.14. The only variable that changes is the k variable. Does this make sense? Should the equation for a Fr # less than 0.8 be raised to a power as well? I know the above equations are confusing in this format. To get a better view look here:
The equation and info is listed on page 303 of the pdf.
Any help or insight would be greatly appreciated. Thanks in advance
D50/y = (k/(Ss-1))*(v^2/gy)
if the froude number is greater than 0.8 then this equation is used:
D50/y = (k/(Ss-1))*(v^2/gy)^0.14
These 2 equations give very different results because of the ^0.14. The only variable that changes is the k variable. Does this make sense? Should the equation for a Fr # less than 0.8 be raised to a power as well? I know the above equations are confusing in this format. To get a better view look here:
The equation and info is listed on page 303 of the pdf.
Any help or insight would be greatly appreciated. Thanks in advance