Angle of friction for backfill soils

[kellez]

Hello everyone, I am designing a cantilever reinforced concrete retaining wall and I need to determine the angle of friction of backfill soil.
Since this is not an insitu soil how am I supposed to determine the angle of friction of the backfilled soil since i am not able to get samples to carry tests on?

 

[kellez]

Yes i can, however i am limited to what is available locally otherwise we get increased cost due to transportation.