Fill Materials Suitablity

[ONENGINEER]

Can GW-GM or GW-GC materials be used for a structural fill under foundations. The materials are comprised of 63% gravel (angular), 26% sand and 11% fines? This is for a two-level building construction and if an be used we do not need to import crushed aggregate. Thank you for your feedback.

 

[aeoliantexan]

I would expect this material to have a fairly high value of internal friction (Phi), probably between 34 and 38 degrees depending on the angularity of the particles. If it is a GW-GM, the cohesion will be nearly zero. If a GW-GC, it coud have pretty good cohesion depending on the placement water content and future water content and drainage conditions. Permeability could be low or moderately high depending on the gradation. I expect it will be fairly low.

This would be a good bearing material for spread footings, especially with a few feet of embedment. If the underlying soil is water-sensitive, you need to know about the permeability or cover it with impermeable soil and grade for good drainage.

 

[Ron]

Looks like pretty good material. Compact it and build on it.

 

[dik]

Try to limit the amount passing 200 a bit... generally less than about 8%, else it could become frost heave susceptable...

Dik

 

[ONENGINEER]

Dik

How can we reduce the fine contents from the materials in the field. Does it mean to wash them??

Thank for all the useful comments.

 

[dik]

Just be aware that this can be an issue and design accordingly. In my fill material, where there are standard specifications for a particular material, like Granular 'A' or whatever, I have created another material "Washed Granular 'A'" if the amount of fines is too large... else use another material or consider frost susceptability.

Dik

 

[Ron]

If you need to reduce the fines, add clean sand to "dilute".

 

[cvg]

blending or washing on-site is problematic, might be better to import better material or live with what you have or deepen your foundations to eliminate the fill

 

[fattdad]

frost heave for foundation is only relavent if the footing is above the frost depth. I'd consider this an unnecessary concern.

make sure you have the appropriate Proctor when you test compaction. The presence of oversize materials should require a Method C Proctor and if there is oversize beying the Method C, you'll need an oversize correction for the lab curve. During placement you'll also need a sieve in the field to assess whether the actual presence of oversize material is consistent with the lab curve. If not, you'll need to do an oversize corrction for the field test.

I'd think this is fine material. That said compaction control with oversize corrections can lead to problems if the well-intentioned are not experienced.

f-d

¡papá gordo ain’t no madre flaca!