how deep a layer for a plate compactor

rooftrussman · Mar 26, 2008

I just got a plate compactor, not quite a tractor but seems almost as heavy, and wondering how deep a layer of compactible fill one can compact. It's a Bomag 4.5 HP more or less and claims 20" depth compactibility (is this a word). Is this realistic? I'm thinking 8 or 10" because I don't have too much to do but think that may still be too much. I never quite trust the specs especially if I don't know anything about the equipment and have no experience. Thanks

RPK · Mar 26, 2008

On larger projects in our area most site engineers specify to compact fill in 12" lifts. Using a large vibratory roller. I would think that using a small plate compactor, 6" lifts would be about right.

john_bud · Mar 26, 2008

Did a guys foundation after the walls were poured. We did 4-6" layers.

Depends on the soil too. Much better to be too thin that too thick!

jb

Egon · Mar 27, 2008

It will depend on the type of material being compacted. With granular material the depth will be greater. Clay type soils the depth will be much less. This type of packer is not really recommended for clay soils.

Farmwithjunk · Mar 27, 2008

Egon said:
It will depend on the type of material being compacted. With granular material the depth will be greater. Clay type soils the depth will be much less. This type of packer is not really recommended for clay soils.

There's the answer! I'm an estimator for a general contractor. I read endless volumes of specs on projects we're bidding. Almost all require 6" to NO MORE than 12" "lifts" when compacting, again, depending on what material is being addressed. Also to be considered is the percentage of moisture in the material. Extremely dry fill typically does not compact well.

builder2 · Mar 27, 2008

With clay soils and any other fill material here in Michigan the general rule of thumb is to compact in 6" lifts. Many of the local contractors here will use a bank run sand unless another material is specified. They will also try to talk you out of the 6"lifts and say 12" is good enough (it is not).
There are compaction testing tools that reads out in psi that will give the rate of compaction. Here is a link to one.

Testing Soil Compaction | Gempler's

Good luck,

Paul

brandoro · Mar 27, 2008

I filled a 20 X 40 swimming pool with jack pine sand (fairly fine sand with a little bit of clay in it) I was spreading about 6" lifts then going over it with the plate compactor. That worked well. I never tried going deeper so can't say if it might have still worked but I know 6" will pack down hard enough that the front tires with a full bucket of damp sand barely leave a mark. The material being damp is important too, if it gets too dry you just chase it around.
On another job I filled an area with clay and found the plate compactor nearly useless on that material. Did better idling the tractor back and forth with a full bucket. Good thing it was a small area and compaction wasn't too great an issue.

rooftrussman · Mar 27, 2008

Thanks for the feedback. Sounds like I should use (what they call it around here is crusher run) a fine almost like rockdust. It's going to be trucked in material so I'll be sure to ask before I get too much.

Builder · Mar 27, 2008

rooftrussman said:
Thanks for the feedback. Sounds like I should use (what they call it around here is crusher run) a fine almost like rockdust. It's going to be trucked in material so I'll be sure to ask before I get too much.

Different compactors are used for different jobs. For fill around a foundation or trench work, we use a jumping jack tamper. For wide flat stone areas, like sidewalks or concrete floor prep, we use a plate tamper. I never try to compact more than 8-12" depending on the material.