Clay Compaction 1

[VanEngineer]

Does anyone have an idea what the compaction factor is for clay once it is taken from a stockpile, hauled by trucks and compacted on site at 95% standard proctor? I need to know what increase in volume due to compaction I need to account for.
Thanks

 

[Shwenkerbean]

In many clay materials, you can often expect no swell or shrink. If the material has been placed into a stockpile with no major voids, I would expect a 1:1 volumetric comparison. It just depends on how tight that the stockpile was constructed.

If you need to figure out truck counts, I would assume 14 CY bank for you average road legal truck. Clays tend to have a high moisture content and therefore can be very heavy.

 

[civilperson]

20-30% shrink in volume from stockpile to compacted fill for glacial till, loessal silty clays and some other mixes found in midwest states.

 

[civilman72]

No shrink/swell for clay??

The "clay" we have in Colorado has high variations of shrink/swell factors. I'm not a geotech, but to say you should not expect any swell or shrink would be VERY misleading to any engineers working in my location.

I've recently had a site where the clays had a 30% swell factor, but that was from in-situ soil. Assuming you are grabbing this material from an existing stockpile, you should not have to worry about the swell factor, but would agree that you should definitely expect some shrinkage when you compact it to 95%.

Due to the fact that all soils are different, I would recommend that you have a geotech engineer give you the shrink/swell factor for this soil (they do it all the time), or else you're simply going to be making assumptions, and you could be WAY off on your truck load calcs if you're hauling a lot of dirt.

 

[fattdad]

I just can't think of a case where the soil in a truck would "swell" in volume after it's compacted in the fill. I can think of many cases where the soil swells in a natural setting or where it may swell after being placed as compacted fill.

One item to include in this discussion is why there is clay being trucked to the job site? If I was paying for fill to be delivered to the site, I'd want some bank run material (i.e., silty/clayey sand, etc.) rather than something that's potentially hard to use with a low subgrade support value - maybe that's just me. . . .

When going cut to fill, the truck shrinkage factor (again to me) just isn't relavent. The density from the cut v. the density in the fill is often about the same (or within a few percent).

f-d

¡papá gordo ain’t no madre flaca!

 

[nelson51]

When reading your post you pose a two part question from an excavators perspective. Number one, anytime you haul material in a truck you loose volume due to voids, especially when dealing with clays. We typically deal with clays that have a PI of 30 to 50, and we will allow a minimum of 20% loss in trucking to account for the large voids we encounter. On the jobsite, we usually encounter a 20 to 30% loss in volume when the material is compacted. For instance, if the required compacted fill on a jobsite (clay) is 10,000 cubic yards, we will add 50% to that volume to account for loss in trucking and compaction. This would yield approximatley 750-20 cubic yard trailer loads.
Hope this helps.

 

[dirtsqueezer]

I'm not going to run the numbers, but I have a habit of testing stockpiles before I test compaction in place. For for sand or gravel I usually get around 75-80% MDD . I can think of only one site like this, and I believe there was more silt than clay. I didn't test the stockpile on that job. Best of luck.