questionable proctor results

[danyul]

I have a soil with a LL=181 PL=136 PI=45

some type of volcanic ash... we are running a proctor and getting some unexpected results.

pt1 max den=29.5pcf m%=146
pt2 max den=35.5pcf m%=128
pt3 max den=32.5pcf m%=118

the field moisture was 180%+ so we have been drying it running the tests along the way.

so according to this the max dry dens is around 35.9pcf and m% 131.5

is that reasonable? im gonna keep drying it out and see what happens.

 

[Ron]

Why are you running a Proctor on this type of material? With the low unit weight, I'm not surprised at the moisture content.

Are you actually going to compact this material? And if so, what is the application. I would bet that the material is highly unstable.

 

[danyul]

well im not going to use it anymore... im just curious if it is even possible to have these results

 

[TDAA]

Yes, it is possible, with the right material. But wow, that is some nasty stuff, and talk about an affinity for water.

 

[BigH]

. . . worse - after you've compacted it - and it dries out; fluffy fluff time! Loess soil we had in Northwest China had this "fluffy" characteristic.

 

[Ron]

BigH...where have ya been? Glad you're back.

 

[fattdad]

But wow, that is some nasty stuff, and talk about an affinity for water.

I'm not sure that's how I'd look at it. I'd more likley say, "Talk about some low specific gravity!"

f-d

¡papá gordo ain’t no madre flaca!

 

[TDAA]

f-d,

He is only a couple pounds off the zero air voids curve, with a SpG of 2.6, at pt2.

I was more referring to the LL=181 PL=136 PI=45. This stuff can take on water.

 

[fattdad]

I got a Gs of 2.2 at the mid point. The moisture content for the wet point is most suspect. It would be a Gs of 1.6 for this wet point, so I figure the actual compaction moisture content was not captured.

¡papá gordo ain’t no madre flaca!

 

[dgillette]

Wow. My initial reaction was that these results are just crazy and messed up. However, I notice that Wopt is fairly close to the PL. This is usually the way it is for more typical soils, for reasons I believe have to do with the ability of the soil to be kneaded, but still have some air voids. Therefore, this wild Wopt appears to make sense after all.

Any idea about the mineralogy? Shrink and swell? Seems like MH is always weird, and this is well below the A line.

Keep us posted as you find out more about it.

DRG

 

[danyul]

Ok sorry guys... I think I have to chaulk this up to lab error. After I got those results I asked them to keep drying the soil and pound some proctors alog the way...

I don't have the exact numbers in front of me but... The max dry den laity kept going up as it got drier. Last I saw was around 55% moisture with a max dy den if around 60ish. Still not great material but now as bad as initial readings.

Th odd part is that it compacts well at those high moistures (100+) so the lab guys didn't see anything wrong.

The specific gravity does seem low as well.

I'm gonna keep drying it out.

 

[TDAA]

The highest OMC soil that I have worked with was around 45%, and that was some weird silt in Nottoway Co. VA. The limits were nowhere near what you have, though.

I was looking at the break you have in the curve points, and comparing to the PL, as dgillette did, so things looked like they were making sense. Do you have a gradation on the material as well? Curious to see that.

f-d, how did you get Gs from that info?

 

[fattdad]

f-d, how did you get Gs from that info?

For any given dry density there is a saturation moisture content. This is dependent on specific gravity of the soil grains. It wouldn't surprise me if the saturation moisture content (when you are in the 125% range) is close to 100. So, you can calculate the specific gravity required to get that density (i.e., cause you claimed saturation).

You can do this for 90 or 95 percent saturation too. Typically the optimum moisture content is 90 to 95 percent saturation. Greater as you slide down wet side of the moisture-density relationship.

I'm in Virginia, but never seen dry densities below 85 pcf. In Panama, I had a project where the maximum dry density was about 60 pcf - volcanic in origin.

f-d

¡papá gordo ain’t no madre flaca!

 

[SirAl]

Looks like bentonitic material. Difficult material to test - may require longer soaking time for each point.

 

[TDAA]

Thanks f-d, I was expecting that is what you did, but knew you were making an assumption. That is where I was contemplating your numbers.

 

[letrab]

How much of this stuff is available. It sounds like it has potential for use as a hydrophilic waterstop if available in significant quantities.

 

[danyul]

update:
m% Dryden
76.6 38.3
53.2 44.4
40.1 50.2
32.3 52.2

giving specific gravity around 1.1 and still no max dry den. but at least we are back into a more "normal" range. like i said earlier the soil compacts well at very high moisture and was not muddy or mushy at all. just by looking at it you cant tell it is half water.

the lab did do a cbr at the high moisture because they thought they knew the max dry den... and "letrab" you may be right... they couldnt "jack" the sample out of the cbr after soak. there is a "limitless" supply of this stuff on the big island of hawaii.

 

[fattdad]

Oh wait, this is Hawaii? Field Trip!

f-d

¡papá gordo ain’t no madre flaca!