Ground cover for sewer pipe 2

[lKobRal]

Hydrauliс Design of Storm Sewers says that ground cover for sewer pipe should count like this: surface elevation minus invert elevation minus pipe diameter.
So, is ground cover a difference of surface elevation and top of the pipe, or difference of surface elevation and invert elevation? If second is right, why do we subtract the diameter of pipe?

 

[cvg]

H is the cover over the pipe

 

[lKobRal]

Thanks a lot, it seems that there is a mistake in the book.

 

[BridgeSmith]

Actually, I think the book is correct, ignoring the pipe wall thickness. If the invert elevation is say, 100' and the surface elevation is 110' and the pipe diameter is 2', then 110' - 100' - 2' = 8' = the distance from the top of the pipe to the surface = cover.

 

[lKobRal]

Thanks, now I got it.
Here in Russia, we take ground cover not for top of the pipe, but for invert level, and it confused me a little.

 

[robyengIT]

You can download a manual explaining everything at American concrete pipe association (ACPA)

 

[dhengr]

lKobRal:
Be careful with your Russian definition of ‘ground cover.’ By your definition, you could have a 48” dia. pipe which had 6” or a foot of ‘ground cover,’ but otherwise was barely properly bedded. The major portion of the pipe would still be 3.5’ or 3’ above the grade. In the U.S. we are usually thinking in terms of soil covering to protect against freezing and/or protection with respect to loads superimposed over the pipe, such as truck axle loadings, etc.