how to estimate swelling pressure

[ohyeh]

I am dealing with expansive soils now.

If I only have testing results on natural moisture content, Atterberg Limits, and Clay fractions from disturbed soil samples collected from test pits, is there a way to figure out soil swelling pressure and amount of heave?

Any help will be appreciated.

 

[Jalthi]

I think you cannot quanitfy swelling pressure or amount of heave with those tests. Atterberg limits is a gneral indicator of whether heaving would be an issue or not. For quanitification, you may want to do one of the following tests: ASTM D4829 (Expansion Index) , ASTM D4546 (Swell Potential).

 

[SirAl]

Some textbooks provide empirical equations using basic indice values to predict Cc values for preliminary designs/estimates. I pulled an old university textbook off the self ... Holtz and Kovacs - 'Intro to Geotechnical Engineering' and found a number of formuli. I also found a chart in the same book providing a range of expansion. Personally, I wouldn't put a lot of stock in these other than to get a cursory idea of what I might be dealing with.

 

[TDAA]

What are the limits and -#200 out of curiosity?

I would not want to guess that pressure to hang my license on. The soil could swell 0.1% to over 25%, it might not. If it does, you can get swell pressures that could range from 2,000 psf to 35,000 psf+.

You need an "undisturbed" sample to run tests on. This assumes it is the standard of practice for your area, if it is not, then you likely do not have a true expansive soil problem.

ASCE tried to put together a terrible publication for expansive soils. Having worked in VA, the standard practice was to run limits at 2.5 feet. In CO, I have drilled 35 to 45 feet for proper pier design.