Expansive soil volume change predictions

[cphi]

Has a study on the accuracy of expansive soil volume change predicted by any or all of the many analysis methods been published? Also, if any of you care to, please provide your comments on the accuracy of the analysis methods you are familiar with. Thank you.

 

[Focht3]

None of them are terribly accurate. In my view, this is an area of real need for research.

Frankly, most of my predictions are intended to bracket the problem - mostly to the high side. Yet the process still leaves me uneasy at times -



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[ashjun]

Hi,
I have not come across independent research papers on the volume change predictions only; much of the focus may perhaps be on the soil structure interaction whilst using these soils. Perhaps you could search papers on those terms and then extract the numbers that you are looking for in their preliminary investigation.
(e.g. Laboratory and field studies of response of structures to heave of expansive clay; Geotechnique Vol 48, No. 1, pp. 103-121).
Note: this is a very general topic and there may be lots of others.

Regards

 

[BigH]

Look up some of the other threads on expansive soils. Many of these give some good references to begin your search.

 

[dirtguy4]

Check out Fredlund and Rahardjo's book, "Soil Mechanics For Unsaturated Soils" 1993. Chapters 12 to 14 outline the type of tests and give examples for predicting heave for expansive soils. They recommend oedometer testing procedures and the important parameters of interest for evaluating heave are:

1. Initial Void Ratio
2. Swelling Index
3. Corrected swelling pressure

All of these parameters can be obtained from a free swell or a constant volume oedometer/consolidation test.

The swell predictions outlined in Fredlund's text are very well researched and from my experience are very representative to field conditions. Hope this helps.

 

[Focht3]

The funny thing is that Del Fredlund and Bob Lytton are friends - yet Bob thinks swell tests are mostly worthless. (He has a point - many aren't run properly, but I think 'worthless' is a bit over the top.) I've run a lot of them myself, and reviewed thousands more. "Prediction" of swell is more of providing an upper-bound estimate of risk, not a foreknowledge that we can estimate the percent swell within 30% of the actual value.



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"

 

[dirtguy4]

I agree that predicting heave from the oedometer test is a little tricky. Corrections should be made for sample disturbance, etc. Determining the proper swelling index and corrected swelling pressure can have substantial effects on predictions of total heave. I used to think that my heave predictions were always on the high side, but after a main water line broke and saturated the clay subgrade of a local building, I now wonder if my heave prediction may be a little on the low side. I found a pretty good research paper that parallels my findings in northern Alberta. "The prediction of total heave of a slab-on-grade floor on Regina clay" - R.T. Yoshida, Canadian Geotechnical Journal, 20: 69-81, 1983". I am a little partial to Del's work, he's a Saskatchewan farm boy such as myself.

 

[Bubba1234]

Hello,
Can anyone help me, I'm new to this site. I was wondering if there is a ASTM or other test for an disturbed soil for determining if a soil is expansive.
I'm from WV, and swelling clays are not normally a problem, but we have a situation here that has caused a "hump" in one of our roads. It's not that deep, but I would like to know for sure before we excavate.
Thanks,

 

[Focht3]

Start a new thread - you will get responses that way...



Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See faq158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"