Moisture content Clay 3

[DOUGDOUGHNUT]

I am an Supervisor Engineer where the Contractor has placed the road sub-base onto the sub-grade, it was proof rolled and passed. Then down came the rain the since then the road has started moving under a load, wittnessed when the construction traffic drove on it.

Would it be sensible to expose the subgrade to the sun to dry out and then re-compact the clay. I am trying to avoid the additional cost of stabilisation.

The contractor has now asked me what the maximum and minimum % that would be acceptable for the moisture to vary from the OMC.

My understanding of the optimum moisture content in clays was that it is the moisture content that will produce the best compaction.

Could there be any problems with using the OMC this highly reactive clay?

Thanks

 

[boffintech]

Rjeffery, you wrote, "Still ASTM (I believe) requires that a sandcone test method be run to confirm every 'n' test done by the nuclear method."

I can't find this reference in ASTM. Do you have a reference for this? Another guy at my office claims this as well but he can’t find a reference.

 

[BigH]

I doubt ASTM says this directly in the standards - ASTM provides testing methods - not how to interpret or apply them.

 

[boffintech]

It like a corp of engineers requirement maybe?

 

[BigH]

Perhaps . . . you can visit the Army Corps of Engineers Engineering Manual site at:

http://www.usace.army.mil/net/usace-docs/eng-manuals

Two manuals come to mind: EM 1110-2-1911, Sept 1995 titled "Construction Control for Earth and Rock-fill Dams" and EM 1110-2-2300, July 2004 titled "General Design and Construction Considerations for Earth and Rock-fill Dams".

In the former, they state: "The nuclear method is not permitted for primary control, but is used to supplement direct methods." (viz., water balloon or sand cone) The latter confirms this in the Corps works.

 

[Grouser]

Re the non-nuc requirement, I believe FAA also calls for it or at least a correlation.

What happened to DOUGDOUGHNUT? He started this thread and then disappeared. Since his post was 6 months ago, I assume the situation has been resolved and he can report back the results to the forum.

I'm wondering if construction traffic might be the heaviest loading the roadbed ever receives and therefore minor displacement caused by it might be acceptable and no further remediation is necessary.

I've failed clay subgrade that passed the nuc density test because it was pumping. I've also seen techs report 75% compaction on sand because the nuc said so.