Expansive soils

[Okiryu]

Are there any references for how to calculate forces/pressures exerted by expansive soils? I just curious to know how much non-expansive material may be required on top of an expansive clay in order to place a slab-on-grade. Or also check pressures exerted to a wall backfilled with expansive soils. Thanks!!

 

[Ron]

This is usually a site-specific, tested parameter. Generalizations won't do much for you.

Have the material tested.

 

[Okiryu]

Ron, I do have expansion potential values based on volume percentage from CBR testing. Can I use this info to calculate soil expansion forces? If so, how? I am not sure how to estimate these forces, but I am assuming that soil density may be involved.

Also, what are the site-specific tests that you are referring to?

 

[oldestguy]

Do a search for "expansive soil tests". There should be help there.

 

[Okiryu]

OG, I have been checking expansion potential based on CBR testing. There is an specific test for checking expansion potential, but do you think that expansion potential from CBT testing can be used as well?

 

[oldestguy]

One of our members did quite a lot of input on this subject back a few years.

Thread 261-85083

Also see if you can find:
Williams, AAB, Transactions , South African Institution of Civil Engineers, Vol 8, No. 6 1958

attached is a chart that may be of use.

 

[Okiryu]

OG thanks as always. Noted that minerology is very important to know. I will start my research about the minerology of my local clays.

 

[killswitchengage]

hello
Why would you use a CBR test for such an issue ? i would recommend an oedometer test which may help get a rough estimate of the expansive pressure.
In any case , mineralogy is important as you can significantly improve the performance of the clay by adding chemical products .

 

[Okiryu]

CBR test results can directly give the swell potential (%) so I used it to have an idea of my soil conditions. My understanding is that swell potential can be verified using the consolidation test apparatus but our local operators are not familiar with this procedure. Fortunately, we do not have too many cases of expansive soils issues in my area, but happened to have a site where the CBR swell potential higher numbers (around 2%) and wanted to check further on this.