suction and bulk density

[Wahab2020]

Hi everyone. I'm new to geotechnical engineering. I am a little puzzled about the relationship between suction which is a negative pore pressure and bulk density. I am trying to calculate the effect of weight on a sensor at 500mm below a clay with suction 10KPA and bulk density of 1.8mg/m3. Any assistance will be highly appreciated.

cheers

 

[MTNClimber]

The firms that I worked for typically used 1D swell/consolidation testing with only a small amount of soil suction testing. So my extent of using soil suction testing is limited. But in general, the soil suction is used to help estimate soil heave, which I have a lot of experience with just from the thousands of 1D swell/consolidation tests I've assigned and reviewed.

As soil dries out and shrinks as a large mass it becomes more dense (increasing its bulk density). On jobs where you know by experience that there are highly expansive soils present, you can actually tell how expansive a sample is by how heavy it feels before you open the cap to look at the soil. Conversely, you can feel how much lighter the samples feel after a site has mitigated for expansive soils.

So if you have two samples of an expansive soil with the same mineralogy, typically the denser the soil equates to a higher expansion potential.

Edit: I forgot to address your question! In my experience, we don't actually reduce the overburden pressure to be adjusted for soil suction.