Transcript Compaction Process in the Field Dr. Talat Bader C

Compaction Process in the
Field
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Dr. Talat Bader
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Field Compaction
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DUMPING
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DOZING
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SCARIFYING
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PICKING
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STONES
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WATERING
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Quality Assurance
water content
Water contents must be closely monitored
during field compaction.
o If the soil gets too wet, it will be impossible to
compact.
o If the soil is too dry, it will be difficult to
compact.
o Since it is easier to add than remove water, it
is best to maintain water contents on the dry
side of optimal during field compaction.
Water content can be measured
instantaneously using nuclear density
probes.
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Determine the Water Content
(in Field)
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Optimum Moisture Content
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2.0
( Mg 3/ m )
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Line of
optimums
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OMC
Dry density
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Water content w (%)
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Holtz and Kovacs, 1981
Determine the Water Content
(in Field)
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Control
Check Point Method
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(1) Relative compaction
100%
( Mg 3/ m )
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Line of
optimums
(2) Water content (dry
side or wet side)
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90% R.C.
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Dry density
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Increase B
compactio
n energy
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Water content w (%)
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Note:
the
engineering
properties may be different
between
the
compacted
sample at the dry side and
at the wet side.
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Holtz and Kovacs, 1981
Holtz and Kovacs, 1981
Check Point Method
Destructive Methods
(Cont.)
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Check Point Method
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( Mg 3/ m )
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Dry density
Sometimes,
the
laboratory
maximum density may not be known
exactly. It is not uncommon,
especially in highway construction,
for a series of laboratory
compaction tests to be conducted
on “representative” samples of the
borrow materials for the highway.
If the soils at the site are highly
variable,
there
will
be
no
laboratory results to be compared
with. It is time consuming and
expensive to conduct a new
compaction curve. The alternative
is to implement a field check point,
or 1 point Proctor test.
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Water content w (%)
Field check point X (it should be on the dry side of optimum)
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COMPACTING
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SLOPES
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COMPACTION ON
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CORNERS
COMPACTION NEAR
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FINAL
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Estimating Performance of
Compacted Soils
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Quality Assurance
Sampling in the field
The fill is sampled at random
Monitoring the compaction process should look for systematic
errors
Dry unit weights of the compacted soil are measured to
make sure that they are exceed the minimum acceptable
values
To assure that the entire fill is compacted above the minimal
density requirements
 The average density measured should be well above the
minimum required
 Statistical methods can be used for this purpose.
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Sampling rates:
 Large fills: about 1 sampling per (1000-2000 m2)/lift.
 Small fills (< 1000m2): 2 or 3 samples / lift
 Fill with lateral dimensions of 100m by 100m, one would expect
to take 5 - 10 sample measurements per lift.
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Definitions
Relative Compaction R should not be confused with
relative density Dr because they are not the same
Relative Compaction R
 fd
R
( do ) max
Relative Density Dr
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e max  e min
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d  (d ) min
(d ) max L
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(d ) max  (d ) min
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Dr 
X 100
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 df = Field Unit Weight
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 do = Optimum Unit Weight
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Relative Compaction (R or R.C.)
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Relative compaction or percent compaction
R.C. 
d filed
d max laboratory
 100%
Correlation between relative compaction (R.C.) and
the relative density Dr
R.C.  80  0.2Dr
It is a statistical
result based on 47
soil samples.
As Dr = 0, R.C. is 80
Typical required R.C. = 90% ~ 95%
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Determine the Relative Compaction in
the Field
Where and When
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Select the test site.
It should be representative or
compacted lift and borrow material.
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typical
of
the
Typical specifications call for a new field test for
every 1000 to 3000 m2,
Or when the borrow material changes significantly.
It is also advisable to make the field test at least
one or maybe two compacted lifts below the already
compacted ground surface, especially when sheepsfoot
rollers are used or in granular soils.
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Field control tests, measuring the dry density
and water content in the field can either be
destructive or nondestructive.
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Method
Holtz and Kovacs, 1981
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Statistical Evaluation
A median density is subjected to assure overall
behavior of fill
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A limit of variation is permitted
usually 3-5% less than median.
No more than 4-5% of the total tests on
project below the limit.
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 % Tests
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Limit
 Reject
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Actual Median of all tests
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 Densities
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unneeded
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 % Compaction
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Question Time
Thank you
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Dr. Talat Bader
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