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aayjaber (Structural) (OP)
29 Jun 09 3:01
Is it possible to reach 95% compaction with a vibrating plate? The compaction area is has to reach for big machines. Is it possible to have several runs on thin layers and achieve what big machine can do?
ishvaaag (Structural)
29 Jun 09 4:05
Have checked
Moving the Earth, the workbook of Excavation 4th Ed
Nichols, Day
McGraw Hill 1999

doesn't make specific statement of what the kinds of small tampers and vibrators can get in terms of compaction, but says in the section that a compaction meter by MBW can measure the degree of compaction attained, "say 95 percent of optimum density". For the Vibrating Plate Tamper (not the "Frog", which is smaller) says "Compaction maybe obtained for some distance around the plate, by vibratory settling"; and further in the text a chart for compaction selection is given, where the recommended equipment for compaction is selected on the sole basis of the kind of soil to be compacted. Vibratory plates are only recommended for non cohesive soils up to a maximum mix of clay of 50% clay. This is the same range recommended for static rollers. For the contrary range, 100% clay to a mix with 50% sand, rammers and rammer plates are recommended. For mixes of sands and clays in-between, rammers with extension plates and vibratory rollers are recommended.

 
GeoPaveTraffic (Geotechnical)
29 Jun 09 7:58
Yes 95% can be obtained with a vibrating plate type compactor.  You will need thin lifts and the material will need to be very close to optimum moisture content.
BigH (Geotechnical)
29 Jun 09 9:19
and, to add to GeoPaveTraffic's post - - - a lot of time!
fattdad (Geotechnical)
29 Jun 09 12:59
Just to push-back a little on GTP's post:  The "optimum moisture content" when using thin lifts and a vibratory plate, may not coincide with the optimum moisture content determined by ASTM D-698, Standard Proctor.

So, I agree, you'll have to be very close to "optimum", but I think the only way you can identify the optimum moisture content is to do a test pad.

f-d

¡papá gordo ain't no madre flaca!

cvg (Civil/Environmental)
29 Jun 09 13:23
since you have not given the type or size of equipment, depth of fill or type of material, desired fill placement rate nor have you confirmed if this is standard or modified proctor, I guess the answer is a qualified sure, why not.
GeoPaveTraffic (Geotechnical)
29 Jun 09 17:01
I agree with fattdad, the optimum moisture content does vary with the amount of energy being put into the material with lower optimum's for higher engergy.
msucog (Civil/Environmental)
29 Jun 09 20:14
for sands in 4 inch lifts with lots of time then sure...for much else, good luck.
Ron (Structural)
29 Jun 09 20:21
Agree with above...but also, depends on the material.  If clayey or silty sand.....you'll spend a LOT of time as BigH noted.  If clean sand....not so much!
BigH (Geotechnical)
29 Jun 09 23:11
To set the record, it is universally understood that "an" optimum moisture content is energy driven.  In other words, OMCvp is higher (likely) than OMCstd which, in turn, is higher than OMCmod which is greater than OMC15tvib.  It is obvious that 95% compaction relates to either Standard Proctor (D698) or Modified Proctor (D1557) (or, for the Brits, light tamping and heavy tamping respectively). 95% compaction, then can be achieved over a range of moisture contents (compared to the standard or modified proctors).  Obviously, for your plate compactor you should be attempting to achieve "optimum" plate which isn't the reference standard optimum - as this will give you the maximum density that can be achieved.  You will need to confirm that the OMCvp is within the range of the moisture contents that, when achieved, can produce something which gives a dry density above your limits.  This likely is achievable.  The need to minimize the loose lift thicknesses is to be able to impart as much energy as possible into the material - the thicker the lift the less energy throughout the whole lift. Too, there is also the fact that overlying lifts will cause additional compaction in lower lifts - although with vibrating plate, not much.  As fattdad says, a trial pad is the only way to be sure - but not, in my view, to determine necessarily the optimum moisture content but that the method will provide 95% of the referenced compaction at the moisture content you have - if not, then you would have to dry or wet the soil to see if you can achieve better compaction - or adjust the lift thickness.   
aayjaber (Structural) (OP)
29 Jun 09 23:37
The material to be compacted is mainly (80%) serpentine rock at various stages in its weathering. The material ranges in size from very fine spoils resulting from grading and drilling piers to gravel that ranges from 1/4" to 4". No top soil with organic material will be allowed in the mix.

The plan is to spread almost 4" layers at a time, water it and pass over few times by the plate vibrator, the machine I have in mind is (6057 lbs. of force). The compacted material will always have to be wet to mitigate the risk from the naturally Air Borne Asbestos.   
iandig (Civil/Environmental)
2 Jul 09 4:53
There is a very good book by Parsons which covers all the research work he did when he worked for the UK's Transport Reasearch Laboratory. This book includes all the papers he wrote and was involved in and stretches from the 40's up to the 90's when he finally retired. The work he did was then used in the SHW to develope table 6/4 which provides clear guidance on the depth of layer, number of passes etc... for pretty much every type of fill material you can think of, in conjunction with most (not however the High Engery Impact Comapction/Dynamic Rolling) that the industry has available. You can download, for free, a copy of series 600 from the SHW by taking the following link :
http://www.standardsforhighways.co.uk/mchw/vol1/pdfs/series_0600.pdf
Although this won't provide the research papers used to develope the table, it does set out the level of compaction 'expected'. The process to use this will be to look at Table 6/2 and pick out the most similar grading to what you have, then look up this class in Table 6/1, this will then indicate the 'compaction method' which can be looked up in Table 6/4.
The basis of the research work was to measure the performance of the compaction plant and the end-performance of the material (in consideration of the proposed end-use). This was then used to develope the material class system, appropriate testing and outline specification limits. Therefore by following this procedure in reverse, the discussion of which is the appropriate method of laboratory compaction needed to identify the correct MDD for checking % compaction is dealt with as the method specified in Table 6/4 was derived from full scale compaction trials in a research environment. Very useful where you have a single-sized material that will not behave like a 'nice simple clay'.
BigH (Geotechnical)
2 Jul 09 9:56
Thanks Ian . . cookcook

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