Angle of Repose vs Angle of Internal Friction

[CABaker]

I'm working on a grain storage/retaining wall problem. I'm dropping soya and canola from approximately 65' above ground level and designing a retaining wall at several locations.

What I'm looking for is a good reference for the angle of repose, angle of internal friction, and the effect of the discharge "flattening out" of the grain. The idea here is I can save on the wall if the difference between the angle of repose and internal friction is different.

Any suggestions?

 

[civilperson]

No, the angles are similar and I would design to the flattest angle for safety.

 

[dgillette]

Here's a question for other geotechs, rather than an answer: If the grain is being dropped from a great height, does that compact it against the walls of a relatively rigid container, similar to compaction of fill against a wall?

A number of people have developed numerical models and probably lab data that show that pressures quite a bit higher than Ko can occur near the top of the fill because of the compaction. (Notably, Duncan, Williams, Sehn, and Seed "Estimation Earth Pressures due to Compaction" [sic] in the Dec '91 ASCE JGE, with Erratum in March '92, and discussion and closure in July '93.)

I don't know anything about canola (same as rapeseed?) seeds, but as a one-time farm laborer, I do know that soybeans, being rounded and smooth, have a pretty darned low angle of repose, which allows a few spilled bushels to spread over a large area of barn floor. I believe that would go along with a pretty darned low angle of internal friction (and zero cohesion unless they are compacted pretty tight). As civilperson correctly states, they are not exactly the same thing, but pretty close.

Have you tried the ag engineering literature? Is there an ag engineering forum on Eng-Tips?

Maybe you could do some dry/drained triaxial shear tests with 4" diameter specimens.

Best regards,
DRG

 

[BigH]

Actually, I ran across a site once that had all this information for various grains - will try to find it again.

 

[cvg]

see links below for angle of repose and other useful data on storage

http://www.extension.umn.edu/specializations/cropsystems/M1080-FS.pdf

http://www.oznet.ksu.edu/library/ageng2/mf2362.pdf

http://www.oznet.ksu.edu/library/ageng2/mf2363.pdf

http://www.extension.iastate.edu/obrien/news/Grain+Storage.htm

 

[dicksewerrat]

I have seen many "temp' storage facilities at grain elevator sights. I'd search temp. grain storage for vendors and looka t what is now available.

Richard A. Cornelius, P.E.

http://WWW.amlinereast.com