Questionable Modified Proctor test
Questionable Modified Proctor test
(OP)
I had a contractor using a backfill material that was tested using the modified proctor method yielding an optimum water content of 6.8% and max dry unit weight of 21.28kN/m3. They recently "retested" the backfill material getting a new corrected wc of 10.7% and max dry unit weight of 19.94 kN/m3. Thats a pretty drastic change in optimum wc and a drop in the max dry unit weight on the same material in my opinion. I am now getitng compaction test results with many coming above 100%, which itself not a huge deal, but several have been above 102% and even 103%. I am questioning these results now and while I am not concerned with the values around 100% I am worried that any test that resulted in a 95% to 97% percent compaction are not "true" values and may be lower than the specification requirement of 95% compaction. Thoughts?





RE: Questionable Modified Proctor test
RE: Questionable Modified Proctor test
Thats of course if it is possible, maybe concrete has been poured on top or whatever. If that is the case you might be best letting sleeping dogs ly!
If additional fill has been placed, then excavating down to maybe 1.5m and preforming some Nukes might be an option.
Even if the "true" values were 90% they may have gained density over time due to additional fill on top providing a surcharge or dissipation of porewater pressure (if wetter than optimum).
If more than 1.5m of fill has been placed, again let sleeping dogs ly....Its only going to be marginally below the true 95% value (hopefully) and will that have much of an effect.
RE: Questionable Modified Proctor test
All the compaction test results were recorded wiht the nuclear denso.
RE: Questionable Modified Proctor test
Dik
RE: Questionable Modified Proctor test
RE: Questionable Modified Proctor test
RE: Questionable Modified Proctor test
Soils as you have described can vary in their Proctor value rather easily because of variations in the particle sizes at any location.
Depending on the area to be tested, multiple Proctor tests might be required.
RE: Questionable Modified Proctor test
My first thought would be that the Mod. density of the material varies more than was anticipated, be it due to variable gravel content or otherwise. I would get a couple of extra tests run and use an average Mod. if possible.
All the best,
Mike
RE: Questionable Modified Proctor test
RE: Questionable Modified Proctor test
RE: Questionable Modified Proctor test
Assuming you work mostly in glacial till and residual soils, you probably have sharply peaked Modified Proctor curves, high unit weights and little room for moisture ranges. Let me know if I'm off base....I'm doing some writing and still have time to change a few things if necessary!