Use of moisture content test results

[MCC1966]

Usually in geotechnical reports we conduct moisture contents an samples across the investigated depth and evaluate these numbers in parallel with the results of Atterberg's limit and hence we can know the existing state of the soil; e.g, about plastic limit (PL), lower than PL ,at liquid limit and so on.
-What is the major ultimate use of knowing this state.
-Is there any other use of the moisture content results

Sorry if my questions seem very fundamental

 

[dgillette]

1. Trafficability: Unless it's near or below PL, you won't be able to drive on it with a scraper.

2. Wetting/drying of borrow material required for compaction: Optimum moisture for std. Proctor is generally close to PL, so do you need to sprinkle it, or blend it with other material, or disc it repeatedly under the summer sun to dry it?

3. Remolded shear strength: Correlates reasonably well with liquidity index. (Peak strength does not correlate as well.)

4. General sense of what the soil will act like in excavation.

5. Liquefaction potential for low-plasticity clays and silts.

There are probably more that I haven't thought of.

DRG

 

[cap4000]

I always like to know all the limits in particular the liquid limit. That is the moisture content percentage at which the soil becomes like "quasi fluid". I do a lot of retaining walls, underpininng and shoring jobs. These tests are also cheap to have done. Nice Thread.

 

[oldestguy]

More? yes.

Combined with LL you can estimate compressibility and settlements, at least approximately, without running consolidation tests.

This is useful especially if you keep records of past lab work for soils in the area.

 

[jdmm]

For fine grained soils with a PI of 20 or more the moisture content can be used to estimate Cc/1+e0 for settlement analysis. This is the primary use. If the moisture content is lower than the PL then the soil should be overconsolidated but this can be better determined using the undrained shear strength (Su/p') and the method of Schmertmann or the electronic cone using the method of Mayne. Using the moisture content and the OCR I have estimated with good success the settlement of preloads and fills.

 

[DRC1]

This is a classic example of why you need not only moisture contents, but a complete geotechnical program for any sizable project. zseveral years ago we cotracted to replace a bridge in stages with a cast in place culvert and steel sheet piling for water and soil retention. To maintain traffic, the work was to be done in stages. Because of the low cost of the project, $300,000; it was decided that only soil borings were needed with out any testing. The borings showed a sand overlying a silt. We buil the first of six stages. As we withdrew the sheets, the culvrt sank 6 inches and the wall sank 9 inches. We were shut down for many months as the state investigated the problem nd redesigned the bridge to be founded on piles. When the work resumed we had to remove the previous stage. during the course of the rework I was able to retrive a reasonably undisturbed sample and have tested. the silt was a low to medium placticity silt with a LL near the natural water content. The test cost me $25 to run. As soon as I got the results I knew that the soil had lost all its strength during sheet extraction. The job started at $300,000 and because everybody felt they could save money by not doing any testing, the job closed out at $3,000,000.

 

[BigH]

What's the old adage - "You pay for it now, or pay for it later - but you will pay!"

 

[fattdad]

I use field moisture contents to compare to optimum moisture content and also to compare to the liquid limit (providing it's not a senitive marine clay). For the latter, natural moisture contents below the liquid limit imply (for what that's worth) some measure of pre-consolidation). For the case that you have the natural moisture content of a soil below the water table, you can also take a stab at solving the weight-volume relationships. This, however is a problem with fine-grained soils that may not be fully saturated even though they're below the water table elevation.

 

[dgillette]

Big H - Usually when you pay later there are interest and service charges! Better to pay for it up front.

 

[BigH]

Might want to look up a paper written by C. Riddell. It has some good points on moisture contents.

http://www.dawsonfoundationrepair.com/under_slab_technical.htm