Angle of Repose/Friction Angle - Standard Tests? 2

[HDGolden]

I need to find angle of repose values for wet and dry sand. So far, I've found friction angle values for dry sand which should be equal to angle of repose. (I found a reference from 1919 but would like something newer). I need to put these in a report along with recommendation that we test for exact angle of repose of on-site soils. Is there a standard testing method (eg ASTM) for angle of repose? Does anyone know where I can find the friction angle for wet sand?

 

[moe333]

There is an angle of repose test from the Bureau of Reclamation (USBR 5380). This is for dry sand.

Friction angle for wet sand should be evaluated with correlations from insitu methods (SPT, CPT, etc.), or can be evaluated with lab tests for sand that is to be placed and compacted at a particlar density as a fill (Direct shear, Simple shear, Triax., etc.). The sample would be compacted to the target density and moisture, then sheared saturated.

 

[dirtsqueezer]

Isn't the angle of repose the angle the soil makes with the normal when it's in a stockpile? Can't you just look at a stockpile and measure with something like a Brunton compass? Or were you looking for something else?

 

[fattdad]

The friction angle of wet and dry sand is the same value, although the presence of water can affect the effective stress and affect the shear strength.

If you take a stockpile of dry sand and pour water into the top, the slope angle may flatten, but this is not related to a change in the friction angle. Rather it's related to pore pressure changes as a water head is established in the center of the stockpile that creates a horizontal flow gradient, which may in turn cause the "quick" condition.

Just a few comments.

f-d

¡papá gordo ain’t no madre flaca!

 

[DRC1]

The angle of repose is not the friction angle. In thoery it should be like many thigs in soil mechanics, theory does not always hold up. Most friction angles are quoted as effective, which is the drained response.

 

[MRM]

The angle of repose, for an oven dry specimen, is a decent indication of the effective friction angle at the loosest state only (relative density = 0%).

Add any moisture to to the specimen (to make it a moist, unsaturated sand) and all bets are off as fattdad mentioned. You're no longer dealing with the drained response; you're dealing with an undrained response; capillarity and "apparent cohesion." Inudate the sand cone specimen with water and you get the "quick" condition he also mentioned.

ASTM's former angle of repose test method has been pulled. There may be other test specs out there, however, as Moe333 says.