Are these soil test numbers extreme?

[criznell]

I'm trying to get edge and center lift numbers from a third party soils test report with Volflo 1.5. The numbers from the report are very high. It seems Volflo will not work with numbers outside of the USCS Plasticity Chart.

Are these numbers even possible? If so could anyone point me toward Edge/Center lift formula's?

0-4 ft sandy clay LL=65 PL=46
4-10 ft sandy clay LL=110 PL=78
10-20ft clay LL=105 PL=76

 

[fattdad]

The numbers are within reason. That said, local knowledge is critical to the correct answer.

I googled the software and it seems you are solving some unsaturated moisture migration problem. I'm not quite sure how Atterberg limits relate to unsaturated moisture movement or characteristic moisture curve relationships.

f-d

¡papá gordo ain’t no madre flaca!

 

[woofar]

After 30 years in the game, and having done countless thousands of atterberg limits tests I have never even heard of such high plastic limits, much less ever seeing them for myself. Are you sure those second figures are PL(Plastic Limit). If they were PI(Plasticity Index) then they would make sense. Assuming they are PI, that would give you PLs of 19,32 and 29 respectively. Plastic Limits above 30 are uncommon, though not rare. Plastic Limits above 40 are extremely rare and should be rigorously checked by repeat testing from different operators. As for higher than that, well you should never say never, especially when talking about soils, but I would only believe such results if I saw them done myself.

What is the Linear Shrinkage(LS) for this material? As a general rule of thumb the PI should be around twice the LS. This relationship varies between 1.6 to 2.4 depending on the reactivity of the material.

 

[BigH]

Just recently did some tests on a Saprolite from Indonesia - LL abut 65, PL at 47 for PI of 18. Also LL 85; PL 50 and PI 35. Done by a reputable Expatriate lab. The types of clay minerals play the part. Of course, in Ontario, we never saw anything much over 15 to 20 for PI.

 

[woofar]

Hi BigH,

I'd like to know more about the saprolite. The highest plastic limit I have encountered is bentonite, LL ranging from 500 to 600, PL ranging from 38 to 45. I have heard of a bentonite with an LL of 750 and a PL of 48. Other high results I have seen have been in Kaolin type clays with an LL range of 100 to 350 and a PL range of 32 to 40.

How much testing did the lab do? In my lab I am immediately suspicious of any PL above 30. My response to such results, much to the chagrin of my techs, is to split out 6 or 8 samples and farm them out to some of our sister labs which I use as a proficiency program, I don't charge the client <grin>.

Also was there any hydrometer analysis done on the material? For those results to be true there must be a very substantial silt content in the material.

I am more than willing to be proved wrong but my gut feeling tells that those results just cannot be correct.

I have a knowledge base of 25 sister labs to call on so I will contact them and see if anyone can add anything about saprolite or any other material with an extremely high PL. I will report any significant findings back here in this thread.