Utility trench backfill - gravel over sand

[RabitPete]

Any issues with using gravel on top of sand while backfilling utility trenches containing PVC pipes? Would a geotex between sand/gravel be useful or is it overkill?

 

[dik]

The sand is for bedding only and once placed, the gravel will not significantly migrate into the sand under or around the pipe.

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-Dik

 

[cvg]

sand may migrate into the gravel. it also allows water to accumulate or flow through the trench. i would not use gravel for trench backfill unless you add cement

 

[RabitPete]

To clarify things, the reason I specified sand + gravel is because trench is crossing concrete pavement. So the trench gets filled with sand first, and then entire area gets gravel/crushed rock before the slab is poured. Slab is subject to heavy vehicular traffic (loading dock area).

 

[EireChch]

I think its overkill to recommend adding cement to gravel backfill. its routinely done around the world with no issues.

 

[cvg]

around these parts gravel is not used however 1 sack CLSM is fairly common for utility trench backfill

 

[1503-44]

If you do, the gravel should be protected from water intrusion to avoid washout.

 

[geotechguy1]

It depends on what you mean by 'gravel'. If you use a well graded gravel sand wont migrate into it (and permeability might actually be quite low).