Checking of Degree of compaction using Light Drop weight Tester" 3

[dgsarath]

Hi

There is an equipment called "Light Drop weight Tester" , "Light Weight Deflectometer" from "HMP LFG" for the use of soil compaction monitoring, testing of foundation backfil and for determination of "soil bearing capacity", according to the manufacturer.

If any of you have used it,

1 can you please say whether the same equipment can be used for checking the degree of compaction of soil embankments.
2 Don't we need to do laboratory MDD values for calculation of Degree of compaction.

Kind regards.

 

[dik]

I used to use a sledge hammer... dropping it from a height of 3' or so... about waist level and let the handle slide through my fingers as a rough guide for compaction... likely a similar sort of device.

Dik

 

[BigH]

Dgsarath - the normal way, as you say, is to carry out compaction testing with the use of the Proctor maximum dry density (or, in case of clean granular soil, relative density testing) - but there is a push in some quarters to use deflection or penetration resistances or soil modulus as a measure of the embankment fill's "worth".
See for example:
FHWA/IN/JTRP-2010/27 - google this

https://ceprofs.civil.tamu.edu/briaud/Compaction_lecture.pdf

 

[Ron]

Since the deflectometer is an "indirect" test method with respect to compaction, it has to be correlated to something direct such as the sand cone, drive sleeve or even a nuke gage. Further it is soil specific (deflection response in clayey, silty or sandy soils will vary), and to some degree, site specific.

There have been many attempts over the years to supplant the traditional in-place density test methods. A few that come to mind....Corps of Engineers Penetrometer, Portable Dynamic Cone Penetrometer, various electrical resistance methods, etc. All required some level of correlation to traditional methods and were most accurate when site correlated.

There's always a need for innovative methods for materials testing, just be careful that the method you use has accuracy, repeatability and reliability.

....and yes, the laboratory moisture-density relationship should still be done.

 

[aeoliantexan]

Many of us have used some type of tool (static penetrometer, dynamic penetrometer, probe rod, shovel, thumb) to assess the uniformity and strength of a body of compacted fill as a supplement and guide to relative compaction testing. In my opinion, the risk of using such a tool instead of density testing is that the soil may be very strong at the present water content but weak if it becomes nearly saturated in the future. Specifying relative compaction is a way to limit the ability of the soil to absorb additional water.

 

[EireChch]

http://www.accurate.net.nz/soil/clegg.htm

Check this out. This is a Clegg hammer which we use to test backfill in foundations. It's a weight dropped from a set height. It is dropped 4 times with the forth reading being your(Clegg Impact Value)CIV. Usually we aim for a CIV of 21 for structural back fill. The CIV can be correlated to CBR and degree of compaction. Can't remember off the top of my head what the DoC is maybe 95-98% compaction. It is a widely accepted method of testing in NZ.