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Single Size Aggregate as Backfill

Single Size Aggregate as Backfill

Single Size Aggregate as Backfill

as the subject suggests , i want to know what are the specifications for using single size as back-fill material under structure i.e. a building, Do we really need to compact it or not ,isn't washing it sufficient ??
a quotation would be really appreciated.

RE: Single Size Aggregate as Backfill

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)


ípapß gordo ainÆt no madre flaca!

RE: Single Size Aggregate as Backfill

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.

RE: Single Size Aggregate as Backfill

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

RE: Single Size Aggregate as Backfill

the specification would be to not use it

RE: Single Size Aggregate as Backfill

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 ??

RE: Single Size Aggregate as Backfill

Why 4 metres?


RE: Single Size Aggregate as Backfill

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...

RE: Single Size Aggregate as Backfill

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 ..

RE: Single Size Aggregate as Backfill

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.

RE: Single Size Aggregate as Backfill

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


RE: Single Size Aggregate as Backfill

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.


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