Soil Compaction 1

[Jess537]

I know that soil compacted at 95% does not mean there will be 5% settlement just based on experience. But how do I explain it to someone inexperienced?

Please help me understand it better!

Thanks

 

[darthsoilsguy2]

show them how people figure out expected settlement... perhaps scroll through this link i just googled

http://epa.ohio.gov/portals/34/document/guidance/gd_660_chapter_6.pdf

... if they want to review it in more critical detail, awesome.... if they don't, they'll at least walk away understanding that there must be more to it.

how to get people to understand things is different for everybody. i suppose i would focus on getting them to understand that the Proctor is just a reference level of compaction that we all just decided on. We could write a new ASTM and call it the Stupid-Proctor. Each lift gets 1 blow per lift for a total of 3 blows. It is pretty easy to imagine that 105% compaction of the Stupid-Proctor will have more settlement than if the soil was compacted to 95% Standard Proctor.... Better-Compacted soils settle less than Worse-Compacted soils, but that doesn't mean we can fill in the blanks for things we haven't tried to learn.

Another concept i've brought up with technicians to keep them on their toes.. Ask them what the moisture content of a pure glass of water is. Usually they'll immediately say 100%. The answer is Infinity %.

 

[Ron]

Use a weight-volume relationship example to show that your have a change in the void ratio with changes in compaction.

 

[LRJ]

Another concept i've brought up with technicians to keep them on their toes.. Ask them what the moisture content of a pure glass of water is. Usually they'll immediately say 100%. The answer is Infinity %.

If the sample volume changes with water content then you normalise with respect to wet mass rather than dry mass. As such, 100 % is correct.

You might come across this in geotechnics/mining if you encounter coal: coal water contents are normalised by wet mass rather than dry mass.

 

[darthsoilsguy2]

LRJ, the moisture content test specified in the Proctor testing ASTM only allows for 1 calculation. (Weight of Water)/(Weight of Soil) x 100%. it's not really a percentage "content" but a ratio that is described in percentage of the 1:1 ratio.

i'm sure there must be a standardized test out there for characterizing the amount of water in something that would let a full glass of water be 100%.

 

[fattdad]

once they understand critical state soil mechanics, they'll get it!

f-d

ípapß gordo ainÆt no madre flaca!

 

[Jess537]

Thank you for all your responses!

 

[Ron]

f-d, ya think?!

 

[oldestguy]

Hey Guys:

What's the plan? Might as well answer him in Latin or Pig Latin.
Even this OG is mystified by all these strange undefined words.

 

[Riggly]

95% compaction, is really a comparison of the soil density based on a given density achieved in a soil mass where a specified amount of energy/effort is applied (modified or standard proctor), and at a moisture content. It does not mean that at 100% there soil cannot compact any further. The more energy applied, the denser the soil will get provided there is still more space for the soil particles to pack together. That is why the modified proctor results in higher dry densities than the standard proctor -more energy is applied. And even with the modified, there is still voids for further compaction if a higher energy level under the appropriate moisture can be applied. Therefore, while it is true that higher % compaction reduces the tendency for further settlement, it is not measure of the total settlement that can be achieved in soil.