You'd have to encapsulate it in some separation geotextile.

He has all the virtues I dislike and none of the vices I admire. - Winston Churchill, Sir (1874-1965)

f-d

ípapß gordo ainÆt no madre flaca!

I assume that you are referring to clean gravel, if so rather to compact, I would say you need to vibrate it to interlock the particles. Are you placing this under the foundations? How thick is this layer? Groundwater present? f-d confinement’s suggestion is also something to consider.

If this backfill is the result of sieving to get near single size gradation, treat it as if it was marbles. Needs confinement.

the specification would be to not use it

thank you for your answers
just to clarify ; its to be placed below S.O.G. above foundations , its deep though 4 meters (about 13 feet).
is there a quotation on the issue from ASTM ??

Why 4 metres?

Dik

If you have to overexcavate 4 m, you may need some temporary shoring if you don’t have space to slope/bench the excavation...Perhaps a structural slab option may be also be considered...

Thank you for this
the back-filling is 4 meters not the excavations because the natural ground level is very low at that area , and a basement option has been declined.
The Consultant advised to to fill it as 20cm layers , but since the back-filling depth is very high , he agreed to 50cm layers, but with compaction.
now i don't believe it is needed since its clean gravel, i don't see how such material can cause settlement.is compaction really needed?
i've searched high and low for compaction of clean gravel in us codes , but didn't find anything , that's why i've turned to you guys ..

I have some very good and some very grim stories of clean (& cleanish) gravel and cobble fill.
My first reaction is ... Self Compacting aggregate is a Fairy Tale.
When it works - Great, but the fable has now gained some strength.
When it doesn't - Sometimes great pain, usually now a Compaction Grouting repair.

I do not allow any more than 12" (1/3 m) of clean fill under Anything, unless specifically compacted and usually stabilized by confinement (see above for fabrics or within a solid container, like stiff soil or concrete).
My biggest problem has been the belief in the Self Compacting aggregate Fairy Tale by municipal and large organization (private & government) engineers, who write so much of the specifications.

perhaps a cellular concrete fill might be easier and cheaper and far better than trying to compact 4 meters of subgrade material (gravel or other material) in order to support a slab

http://www.structuremag.org/?p=7776

If you're filling a low area, it is probably best to compact engineered fill and use a perimeter drainage system... and you can construct on the compact engineered fill. Far better than constructing on clean granular crush.

Dik