Using coefficient of friction to back into wall friction angle

[JStructsteel]

Using the coefficient of friction, is there any way to back into the wall friction angle? This is for AASHTO

Say COF=0.31, can I arc tan(.31)2/3 to get a wall friction angle of 25.83 degrees?

 

[EireChch]

Yes but it all depends on what portion of arc tan you take. 2/3, 3/4 there is a variation in the numbers.

And just report phi to an integer. No decimals

 

[JStructsteel]

Thanks, I think AASHTO 9th edition limits the Phi angle to 2/3?