Angle of Internal Friction of Crushed Stone 3

[AjaxBE]

Hi everyone,
I am looking for friction angle of Crushed stone. The crushed stone was used in two layers as a foundation support for oil tanks. The first layer has a gradation of crushed stone between 20 to 31.5mm. The second layer has a gradation of the crushed stone between 8 to 16mm. The crushed stone were well compacted.

Could anyone advise me which friction angle for the two layer I should use for modeling? Thanks.

 

[fattdad]

40 degrees, maybe a little higher. . .

(Tell me you're not doing bearing capacity though as these two little sublayers are trivial compared to the bulb of shear that extends WAY below the thickness of some subbase materials.)

f-d

¡papá gordo ain’t no madre flaca!

 

[BigH]

 

[AjaxBE]

I am analyzing the stability of the edge of the tank.

Don't you think 40 deg is too small? If the crushed stone is well compacted, it can be high, but may be maximum is 50deg. What do you think?

 

[dgillette]

Not all crushed rock is created equal. Crushed unweathered granite from Idaho Springs CO is rather different from crushed "limerock" (local term) from Brooksville FL.

 

[fattdad]

If your experience dictates that 40 degrees is too small, then use your experience. If you are asking me (who provided the recommendation to use 40 degrees) whether 40 degrees is too small, then my answer is, "No."

f-d

¡papá gordo ain’t no madre flaca!

 

[BigH]

If you are doing the stability of the edge of the tank, why not give us the complete details as to the site strata - tank sitting on X ft of crushed stone (with the thin layer of bitumen sand from your other thread) overlying Y ft of firm clay overlying Zft of soft clay - etc. Seeing the big picture. Does the tank have a ringwall? . . . or just sitting on a granular tank pad that extends A ft beyond the edge of the tank. If the tank is on a desiccated crust of clay you might want to search for Bjerrum's paper on a tank edge failure - given in London's 1957 ISSFME Conf - very good paper and still relevant.

 

[Mccoy]

The presentation I'm attaching is a good generic source for crushed stones, by Mike Duncan, the specific case like Bigh says must of course be given due consideration

 

[six06]

Is the link GOOD?

I am not able to download the paper

 

[Mccoy]

I just tried and I can't myself. Going to give it a 2nd try

 

[Mccoy]

Still no luck, I'm going to check if I can trace the link where I downloaded it

 

[six06]

Ok, thanks, that would be a good reference to have!

 

[Mccoy]

Friction Angles for Sand, Gravel and Rockfill
by J. Michael Duncan

Notes of a lecture presented at the
Kenneth L. Lee Memorial Seminar
Long Beach, California
April 28, 2004

Can't locate it any longer on the web

I'm going to attach temporarily the document to one of those sharing sites.
The presentation was freely available online, to my knowledge there are no copyrights but if anyone knows otherwise I'll refrain.

 

[Mccoy]

Sorry for the delate, the file should be available at the following link:

http://FastFreeFileHosting.com/file/43193/Duncan-Friction-20Angles-pdf.html

 

[howardoark]

I had a 12-inch direct shear test done (at low confining pressure) on 3/4-inch minus clean crushed rock - it came out 68 degrees, so I'd say 40 degrees is probably low.

thanks for that Duncan paper