David:
I cannot vouch for the accuracy of this device, but I saw it recently and it
caught my interest. It purports to work by comparing the pressure wave
amplitude to some preset value. I believe it gives "GO/NO-GO" results, not
quantitative ones.
http://www.geneq.com/catalog/en/soil_compaction_meter.html
Is entry into the trench (by humans) a problem? I assume it is or any
in-situ density method would be OK, sand cone, nuclear density, water
balloon, etc. If someone can go in the trench, have you considered
something like the Humboldt GeoGauge. Again, I have no first hand
experience, but I am given to understand that the "output" is the resilient
soil modulus, which should be capable of correlation with the density (of a
particular material). There is no excavation required, but the operator
will have to go in the trench.
I think there have been some studies done on this latter device by either
the FHWA or New York DOT.
http://www.hmc-hsi.com/newest/hmc_catalog/Compaction/compaction.html
If you use either of these, I would be very interested in your opinion of
their practical application and accuracy. The latter really interests me,
since it seems one could base quality control directly on soil modulus,
which is a lot more meaningful than trying to do this indirectly through
density.
Regards, Mike
Michael R. Bleakney, P. Eng.
Geotechnical Engineer
New Brunswick Department of Transportation
Design Branch
PO Box 6000
Fredericton, NB
E3B 5H1
Canada
Phone: (506)453-2674
Fax: (506)457-6714
E-mail: [log in to unmask]
-----Original Message-----
From: David Hughes [mailto:[log in to unmask]]
Sent: Thursday, February 08, 2001 11:53 AM
To: [log in to unmask]
Subject: compaction of trench backfill
Has anyone any ideas on how to measure the compaction of backfill in a
trench? I would like to monitor density with depth during compaction.
The measurement needs to be carried out in a non destructive way (ie no
excavation after compaction)
I'm thinking along the lines of pressure cells or strain coils.
Any other ideas? Is the dynamic measurement of surface compaction reliable!
thanks
David
---------------------------------------------------------------------
Dr David Hughes CEng
School of Civil Engineering
Queen's University Belfast
Belfast BT7 1NN
N Ireland
ph +44 (0)28 90 274014
fax +44 (0)28 90 663754
----------------------------------------------------------------------
|