Is there a way to test the field density of a gravel-filled layer? 2

[Promdi86]

This is still related to my earlier thread about the Island road thing. Also, can the compaction % be measured accurately if the course is mostly 2-4inch aggregates with coral sand as its filler?

Thanks again.

 

[Ron]

Field density is not the big issue...lab density is. Most of the standardized tests for moisture density relationships (Proctor test in the US) limit the material in the test to 3/4". While a replacement method can be used for material graded from the top size to dust, if the material is significantly gap graded that will not work.

If there is a crusher available, that's one option. If not, I ask again...why do you need a subbase?

 

[PEinc]

I suppose you could do a non-standard, super-sized, sand cone density test in the field as long as there are not voids between the large aggregate pieces. However, as Ron said, what lab density test can you relate it to?

http://www.PeirceEngineering.com

 

[oldestguy]

I have done this for pea gravel fill.
I level the site, dig a hole maybe 2 feet across and sufficiently deep to cover the whole layer thickness leaving sides undisturbed.

The line the hole with a strong, yet very flexible plastic something line two layers of the stuff you get from the dry cleaners.
Fill with water to the top.

Measure all your weights and get our answer.

 

[PEinc]

But again, how do we determine the % compaction? We need some lab testing for comparison.

http://www.PeirceEngineering.com

 

[BigH]

Might I suggest that he carry out a test section - check "settlements" with each pass - up to, say, 10 passes. Plot the "settlement" vs pass number and determine the number of passes where, say, only 10% more "settlement" will occur. Then use a criteria of achieving this "settlement" in the normal compaction operations.

This is one way of doing it with rock fill placement.

 

[dBasement]

The test described previously is the "water replacement test". It is an ASTM test I believe. When I did that testing for a dam job, we had a heavy steel ring fabricated about 6 feet in diameter placed onto the test area. Our rock was significantly larger, so the size of the ring for the material that you have described can be significantly smaller. We dug the gravel out from inside the ring with a mini-excavator. Hopefully you have a means to weigh a large mass like that. Anyway, fill a large, sturdy container with the material that comes out of the hole and weigh it (after obtaining a tare weight of course). Then the volume of the hole is determined by laying out the poly sheet and securing it with the ring. Fill it with water to get the volume.

To determine the maximum density, you need to use something like that same container, but this time compact the material in lifts into the container using a plate tamper and determine the maximum weight after a few trials. You have to be careful to ensure that the voids at the top of the last lift are roughly the same by volume as the protrusions sticking out of the top of the container.

Also, I think it is vitally important to have me come over and conduct the test utilizing my vast array of experience with it...you did say it was a coral island in the Pacific right?

 

[Promdi86]

I thank all of you guys for your input on this matter. I've spent some time to check if there is any standard that covers the testing of any rock particle bigger than 3/4", making Ron and PEinc correct in asking how field density test results could be related to any laboratory values since none of the ASTM or AASHTO standards. Im thinking of something similar to BigH's suggestion, also manipulating the cobble layer's thickness and ratio of cobbles to sand.

I appreciate any suggestions that you guys might have to further simplify the procedure, and I shall post the results of the field test to let you guys analyze the result