Friction angle for loose crushed stone?

[SteelPE]

I was wondering what the angle of friction would be for a loose crushed stone. I am looking at designing a wall that will retain this material and I can’t seem to find the information in my textbooks or on this site.

 

[ishvaaag]

AASHTO ASD 1992 Table 5.5.5.B (was still at my lap when you were asking)

Mass concrete on clean gravel, friction factor 0.55 to 0.60, Friction angle, delta, 29 to 31 deg.

On crushed stone may be better. Concrete on clean sound rock gets the maximum friction factor in the table, 0.70, and 35 deg for delta.

 

[SteelPE]

What I am looking for is what I would call the angle of internal friction. This way I can calculate the active pressure acting on the wall and appropriately size the footing and stem of the wall.

 

[fattdad]

Call it 35 degrees and see how that looks. I'm sure if it was placed above the critical state, you'd be closer to 4o degrees, but you said loose.

f-d

¡papá gordo ain’t no madre flaca!

 

[ishvaaag]

Crushed stone I think 40 to even 55 angle of internal friction or more but codes for construction (never?) allow to go as high. I think the higher value I have seen as acceptable for calculations is 40 to 41. AASHTO and others, again, I think to remember, limited the angle for non coherent backfills to 34 deg angle of inner friction.

 

[msucog]

keep in mind that loose crushed stone will settle and has pretty substantial voids (so adjacent soil may wash in to it). for the settlement of say #57 stone, i use 1" per 1' of loose #57 stone as an estimate. i'd use caution when trying to assign phi to any poorly compacted materials.

 

[Ron]

Agree with fattdad...that's the range you need to be in.

 

[DRC1]

For crushed stone I typically use 40 degrees. Generally crushed stone requires little compactive effort.

 

[SteelPE]

Just so that everyone is aware, this material is being stored behind a cantilever concrete wall. It is not being used as backfill. There will be no other soil infiltration into this material.

 

[DRC1]

May want to consider impact from dumping if appropriate. Also what about water drainage. The stone will drain only if the water has a place to go.

 

[fattdad]

. . . don't forget your weep holes.

f-d

¡papá gordo ain’t no madre flaca!