Determine compaction for midlifts

[ryudo575]

Dear All,

Our project has been using nukes to obtain our density readings. Our standard probe depth is 150mm.

A layer of fill, total thickness is 350mm height. We have been testing 150mm depth from top of this layer. My question is, is it possible to determine or give an indication of the density(qualitative or quantitative) for the bottom 200mm without digging pads and doing a nuke test?


Thank you.

 

[Ron]

If you are testing in granular material, I wouldn't worry about it. The upper material is likely representative of the lower material (since your depth is not great at all relative to reasonable compaction equipment influence).

If you are testing in clayey or well graded calcareous material, I would expect some bridging. Many nuclear gages have probes that can be extended to 300mm, so you could do that, keeping in mind that you are then averaging the compaction over that entire depth.

If you cannot use a greater probe depth, your only choice is to excavate to the required depth and test, consider a proofrolling technique that will give a reasonable assurance of compaction at the depth you desire.

 

[ryudo575]

Thanks Ron.

Yes, bridging is expected to occur. Especially since the construction method is to place 1st lift at 200mm and the 2nd at 150mm. However, our verification manager still request 1st lift testing. Consistent construction methodology does not provide enough validation that the first 200mm is well compacted. Proof rolling has been offered as verification however was not accepted. Basically, they are willing to accept as long as I can prove the consistency of the construction methodology with some technical info.

In actual fact, lift 1 testing has been performed, however geotech records have reported testing layer all lift 2 which is incorrect and has given me a massive headache to deal with. Which is why I'm looking for methods of midlift testing without have to dig and nuke.

I'm now looking to compare peak wet densities of similar lift 1 material placed elsewhere along our project. So far it seems to be going ok.

Update in the future.

Cheers.

 

[Ron]

ryudo...go back to the testing lab and have them retest at no cost since they screwed up the locations.

 

[ryudo575]

Ron, it's a delicate situation. I have asked many times to change but they refuse too.

Anyways, the matter has been resolved, though in a less technical manner.

Cheers

 

[Ron]

ryudo75...glad to hear it is resolved; however, there is no reason for a testing laboratory to refuse to retest something they screwed up. Withhold payment until they agree to do it.