RELATIVE COMPACTION ON FDT

[saiya]

We are testing for compaction lahar (volcanic ash) using field density test.

MDD = 1.67 gm/cc
OMC = 13.77%

We had results giving 148% compaction!
Resulting to a in-situ dry density of 2.46gm/cc
(AS HARD AS CONCRETE!)

Obviously, something is wrong already.

CAN YOU PLEASE ADVISE A MAXIMUM CRITERIA OF ACCEPTANCE FOR RELATIVE COMPACTION?
Does 115% sound reasonable?

Thanks!

 

[Ron]

I typically start looking at the Moisture-Density relationship being out of range if the relative compaction exceeds about 105%.

Run a moisture-density relationship on a couple of specimens and see if they plot on the original curve. If not, you have a material change and need to do a new Moisture-Density relationship curve.

 

[saiya]

We also had problems with the base coarse material.

MDD: 2.27 gm/cc
OMC: 8.30%

Specific Gravity = 2.98

CAN YOU RECOMMEND A CUT OFF TOO?

NOTE: STANDARD PROCTOR TEST was used to get the MDD and OMC.

 

[Ron]

The standard Proctor could be the problem. In granular materials, the compactive effort put forth by modern compaction equipment can easily exceed the standard Proctor effort.

If you are using vibratory compaction equipment and your material has less than 10 or 15 percent fines, I would use the Modified Proctor.

 

[dgillette]

Is this sort of volcanic ash prone to particle breakdown during compaction?