swell test

[slabongrade]

Geotech report says 8.5" to 9.5" potential swell from a PI of 32. If the test involves compacting the sample beyond it's in situ
density, then soaking it to measure swell - it would seem an erroneous value of swell (9.0% in this case).

TXDOT uses an excel spreadsheet where the initial moisture state, LL, PI, and minus #40 are input for each 2 foot depth of soil.
That is what we use, and PI's of 32 would normally have a PVR of about 2.5".
I understand sulfates in the soil can cause big problems, but this report doesn't mention sulfates. It does, however
suggest removing top 10 feet and moisture conditioning with their lab onsite to monitor everything. This is near Fort Worth Texas area.

What say ye fellow geotechies?

Thanks

 

[killswitchengage]

I will try to do my best . It seems to me that PI 32 % is pretty low for a swelling clay, usually high values of PI indicates possible swelling problems. In any event , if you guys are looking to use that piece of land without removing soil, you could try and understand the mineralogical nature of the clay and add something like lime to greatly diminish its activities . You could also try vertical drains coupled with embankment loading to accelerate consolidation beyond the sigma'p of the clay . Or maybe remove 5 foot of the land and use another soil improving technique