Is compaction more than 100% in soil acceptable or not?

[pankaj857]

I am working now for an project of oil & gas industry. Here we are doing river sand fillig activity in layers of 200 mm. The sand was already tested in laboratory and the result is MDD=1.75gm/cc & OMC=9.70%. On working site in situ we are doing compaction of river sand layer by 10MT Vibro roller and carrying out compaction test by core cutter method. On site Moisture content is average=7% or 8%. But sometimes resulting compaction is achieved more than 100% i.e. 101%,103%. Is that acceptable or not?

 

[Mad Mike]

Think about what you're using the sand for and how the added density might be a bad thing. Heavy compaction of the layer will decrease the permeability of the sand but will increase the layer strength and stiffness.

In most instances, your compaction in excess of 100% would be acceptable.

All the best,
Mike

 

[Ron]

As long as the compaction percentage stays below about 105%, it is fine. When it goes up to the 105% range, it indicates you're likely working in a material that is different than your Proctor material. Run field check points if you suspect you are off the Proctor curve for that material.

 

[fattdad]

yes, it's acceptable.

Then again, it's up to you to use the correct Proctor value!

f-d

ípapß gordo ainÆt no madre flaca!

 

[BigH]

First off, anyone who tells you that the OMC is 9.70 % is blowing smoke . . . 2 decimal places? Get real.

Yes, you can get compaction greater than 100%. Look at curves (textbooks) showing the compaction curve for Standard Proctor vs Modified Proctor vs Field Roller Compaction. Ron is right in that order of 105% or so of the standard Proctor may be a maximum - and your compaction curve is likely pretty flat anyway.

Mad Mike hit the nail on the head about river sands - you really should be using relative density rather than compaction (another error in the standard compaction - is the loss of water by drainage once you get to higher moisture contents - you can see the water oozing out the bottom of the mould - giving non-homogeneous moisture contents throughout the sample.

 

[EireChch]

Is the core cutter method the right method in sand? I typically use sand replacement test or Nuclear Gauge Testing.

 

[BigH]

Core cutter in sand - not my choice. Either of the two you suggested or a rubber balloon method.

 

[cvg]

suggest that if this is a large enough project, conduct a test fill and then approve a method spec. no need for extensive testing

 

[oldestguy]

Your statement "The sand was already tested in laboratory" shows you need some "education" as to control of a job by testing. Sure that one test might mean something for some of the job, but it is wishful thinking that one test can control a whole job. Along with the "precision" commented on, most jobs never need or fit a mold like this. Be prepared for on the job lab testing. Also, is there always a need for high percentage compaction? Not usually, especially if no testing is done on natural on-site material yet that also is used for support, etc.

 

[mikeofBelAir]

I would ask, "100% of what" There are different tests for maximum density; none give an "absolute" answer, but are relative to the energy applied. You are not alone....MANY people thing 100% density is a absolute maximum number; it is not.

 

[geojosh84]

Proctors on dead sand are a pain but cheaper than min/max density needed for relative density. Depending on how clean the sand is min/max maybe required if you're required to follow the astm (D698/1557).

For field testing I'd go with sand cone or nuclear guage... gauge will be best on a larger site.

To tack on to Bigh and oldest, use common sense...

Think about the test method versus the magnitude of compaction. Sub 105% is normal but most jobs will have numerous soils that don't fit just one curve

 

[geotechengineer1]

>The sand was already tested in laboratory and the result is MDD=1.75gm/cc & OMC=9.70

Is this the Maximum Dry Density or is it the Standard Proctor Maximum Dry Density? If it's the Standard Proctor Maximum dry density and you're driving loaded 797 haul trucks over it (extreme example), the SPMDD might not be appropriate. In theory there's a family of curves for dry denstiy and moisture content for a given soil where with higher energy the curve drifts up and to the left (higher peak dry density and lower OMC).

It could be that the compactive effort being applied is substantially higher than the test used to get the MDD.

It could be a change of material and a new proctor is needed.

At any rate, I suspect if you've made a fuss about it the person recording the test results will in future never report any values over 100% and simply revise them downards because doing otherwise might result in some angry engineer breathing down his neck and making life difficult.

 

[cvg]

On working site in situ we are doing compaction of river sand layer by 10MT Vibro roller and carrying out compaction test by core cutter method

core cutter method is not appropriate for sand, especially where it is on the dry side and is typically used for clay. suggest using nuke gage and a sand cone for every 10 gage tests