Rankine vs Coulomb Failure envelope

[steve7498]

As for the Rankine method (where the active failure plane behind the wall = 45+phi/2), can someone please explain to me (or at least point me in the right direction) how you would derive the failure plane angle for the Coulomb method?

 

[Doctormo]

NCMA Design Manual or Keystone Walls Design Manual

You should be able to find one on internet. It is a monster formula.

If you wanted to "derive" it then have fun with math.

 

[killswitchengage]

I should point out that active earth pressure angle is 45-phi/2

 

[PEinc]

It depends on whether you measure for from the vertical or horizontal.

http://www.PeirceEngineering.com