How to calculate compactive energy??

[VIRANGA]

I want to make different compactive energy and take relationship between some properties. So I thought to make different compactive energy by changing rammer weight, height of drop, no of bowls , no of layers. How do I calculate compactive energy as a one value from using one combination . ( one combination mean- (2.5kg,30cm , 27 , 3), (4.5kg,30cm,27,3),(2.5kg,45cm,27,3)..........).

 

[Ron]

Why? Those are laboratory standards, established for decades. If you vary the standard in the lab, you will not have a proper basis of comparison for the soils you are compacting. The laboratory energy is intended only as a relative indicator for field compaction. The laboratory energy and the field compaction energy will be different.

 

[VIRANGA]

No I want to know what happence if we change the compactive energy???

 

[Ron]

You will get either less or more compaction on your curve, neither of which means anything outside the standard method.

 

[geotechguy1]

I wonder, how many pieces of compaction equipment used in practice apply energy to the soil equal to, less than, or greater than the energy applied in a standard proctor or modified proctor test? Has anyone bothered to check?

In my area it seems that geotechs often recommend 'compact to 98% SPMDD within 2% of optimum' in 200mm lifts. And then the results come back 6% dry of optimum and 98%. Some will say, re-do the proctor. They re-do the proctor with a sample dug out from the location where the test was performed. The proctor comes back. Same as before.

What energy is a standard proctor equivalent to? A 100 lb plate tamper? 1000 lb plate tamper? What about a 15 ton roller? What if you're compacting it with D-11 cats and 797 haul trucks? How many passes?

In 1930 whatever when these tests were developed, what compaction equipment were they using and how does that compare to what is being used today?

 

[Ron]

geotechguy1.....a bit of historical context first....
The moisture-density relationship (Proctor) was developed in the 1920's by R.R. Proctor, who was with the Bureau of Public Roads, a US Government agency.

Originally there was only the "standard" Proctor. That was because the equipment was relatively rudimentary and the compactive effort variable. The test was developed as a "standard", not necessarily meant to mimick the compactive effort in the field, but to provide a standard method of laboratory testing so that one could assess variations in the soil, moreso than to assess variations in compactive effort. The selected laboratory compactive effort for the test was done in an effort to approximate probable compactive effort in the field, but knowing that it would be variable depending on equipment.

One reason for this standardization of a test method is that you might have one piece of compaction equipment doing all the compaction on the site, but you might have a variety of soils that would be encountered across that same site due to the inherent nature of soil variability. With a standardized laboratory test with which to compare the field effort you could quickly assess if you were getting similar compaction across various soil types.

As equipment became better by its evolutionary design, the "modified" Proctor was developed, again to approximate the compactive effort in the field, but moreso to assess soil variations while attempting to achieve comparable compaction in all.

 

[Okiryu]

VIRANGA, if you are doing research about compaction related stuff, I would suggest to reasearch for compressibility for different compaction degrees in the field...

 

[oldestguy]

On this general subject I rarely had to make some form of reduced acceptance to the usual 95%, 98% of some Proctor (standard or modified) lab density, just to keep the job going. This usually involved compacted fill for parking lots and a few roadways. What I then specified was that the compacted dry density of the fill had to be equal to or more than the dry density of the same undisturbed material where it is acceptable for supporting the pavement (and of course its traffic load). For cohesive soils this generally was found at about 85 percent of the Proctor lab density. The clients frequently were large department store giants and the results always worked as to how the pavement then performed. We did some loaded truck proof type tests to verify proper base course thickness at both areas, compacted fill and the undisturbed areas.