Experiment No. 5
SOIL COMPACTION TEST
Scope
This method describes the procedure for determining the relationship between the moisture content and
the resulting dry densities when the soil is compacted in the laboratory as specified.
Apparatus
1. Cylindrical metal mold with an internal diameter of 101.6 mm, height of 116.43 mm, and having a
volume of 943.3 cu.m., with a detachable mold collar about 63.5 mm high and 101.6 mm in
diameter.
2. Metal rammer with a diameter face of 50.8 mm and weighs 24.4 N. with a suitable means of
controlling its drop.
3. Balances, one with a capacity of 20 kg and sensitive to 1 gram and another with 1000 grams
capacity and sensitive to 0.01 gram
4. Oven with temperature control
5. Drying cans
6. Straight edge
7. Large mixing pan
8. Scoop
9. No. 4 sieve
10. Graduated cylinder
11. Tools or suitable mechanical device for extruding the compacted sample with water
12. Sprayer or any suitable device for thoroughly mixing soil sample with water
Procedure
1. Weigh the empty cylindrical metal mold (with the base but without the collar)
2. Obtain a 2.73 kg representative sample from the thoroughly mixed portion of the air-dried material
passing the No. 4 sieve.
3. Place a portion of a sample in the mold to form a 50.8 to 76.2 mm layer then compact it with 25
uniformly distributed blows of the rammer, with a 457.2 mm free drop. To insure uniform
distributions of blows rotate slightly either mold or rammer between each drop.
4. Repeat the procedure with a second and third layer, adjusting the free drop of the rammer to 457.2
mm. The soil surface should be higher than the lid of the mold after compaction of the last layer.
5. Remove the collar and trim off the soil even with the top of the mold with the straight edge (Fig.7).
Weigh the mold and the compacted soil sample.
6. Remove the soil from the mold and slice vertically through the center. Obtain a representative
sample of approximately 100 grams from one of the cut faces, for water content determination.
7. Break up the soil, which is removed from the mold, remix with the original sample. Add sufficient
water to raise its water content approximately 3 percent and repeat Steps 3 to 6 for each increment
of water added until the soil becomes very wet and sticky or when there is a substantial decrease in
the weight of the compacted soil, (5 or 6 determinations may be necessary).
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Calculation
For each test, the water content of the compacted soil is calculated as follows:
w=
where:
W1 − W 2
× 100%
W2
w = water content, %
W1 = weight of wet soil, grams
W 2 = weight of dry soil, grams
The wet density of the compacted soil can be calculated as:
γ wet =
where:
W
V
γ wet = wet density of compacted sample, gm/cm3
W = weight of the compacted soil in the mold, gm
V = volume of the mold (943.3 cm3)
The dry density of the compacted soil is calculated as follows:
γ dry =
where:
γ wet
1+ w
γ dry = dry density of sample, gm/cm2
w = water content, %
Determine the water content and corresponding dry density of the compacted soil. For each
determination, plot as ordinate the dry density and as abscissa the corresponding water contents.
Connect the plotted points with a smooth line. Generally the curve is parabolic in form.
The water content corresponding to the vertex of the curve is the optimum water content and the dry
density at optimum moisture content is the maximum dry density of the soil.
Questions
1.
2.
3.
4.
5.
6.
What are the effects of water on the unit weight of soils?
what factors affect the compaction of soils?
How many data points are necessary to construct a standard compaction curve?
Why is it important for the final level of compacted soil to be just above the mold body?
How do you select the water content for the five samples in the compaction test?
Will you obtain the same optimum water content and maximum density for the standard and
modified compaction tests? How do you expect the values to be different?
45
Diameter = 114.3 mm
63.5 mm
Diameter =
101.6 mm
116.43 mm
(a)
Drop = 304.8 mm
Weight of Hammer = 24.4 N
50.8 mm
(b)
FIGURE 6
Standard Proctor Test Equipment: (a) Mold; (b) Hammer
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FIGURE 7 After filling the mold completely, strike off the excess soil with a straightedge.
Effect of Compaction Effort
The compaction energy per unit volume, E, used for the Proctor test can be given as
E=
number
of blows
per layer
x
number
of
layers
x
weight of
hammer
x
height of
drop of
hammer
volume of mold
If the compaction effort per unit volume of soil is changed, the moisture-unit weight curve will also
change. This can be demonstrated with the aid of Figure 8.
47
20
Sandy Clay
Liquid Limit = 31
Line of Optimum
Dry Unit Weight, γd (kN/m3)
19
Plastic Limit = 26
50 blows/ layer
Zero-air-void
Curve
(Gs = 2.7)
4
18
30
blows/layer
3
25 blows/layer
17
2
20 blows/layer
1
16
15
10
12
14
16
18
20
22
24
Moisture Content, w
FIGURE 8
Effect of Compaction Energy on the Compaction of a Sandy Clay
Figure 8, shows that, for sands, the dry unit weight has a general tendency first to decrease as moisture
content increases and then to increase to a maximum value with further increase of moisture. The
initial decrease of dry unit weight with increase of moisture content can be attributed to a capillary
tension effect. At lower moisture contents, the capillary tension in the pore water inhibits the tendency
of the soil particles to move around and be densely compacted.
48
18.9
18.5
Dry Unit Weight, γd(kN/m3)
Sandy Silt
18.0
Silty Clay
17.5
Highly Plastic Clay
17.0
Well- Graded Sand
16.5
Poorly Graded
Sand
16.0
5
15.7
15
10
20
Moisture Content, w (%)
Dry Unit
Typical Compaction Curves for Five Different Soils (ASTM D698)
Dry Unit
FIGURE 9
Moisture Content
(b)
Moisture Content
(a)
]
49
Dry Unit
Dry Unit
Moisture Content
(d)
Moisture Content
(c)
FIGURE 10
Various Types of Compaction Curves Encountered in Soils
Type a compaction curves are the ones that have a single peak. This type of curve is generally
found in soils that have a liquid limit between 30 and 70. Curve type b is a one and one-half peak
curve, and curve type c is a double peak curve. Compaction curves of types b and c can be found in
soils that have a liquid limit less than about 30. Compaction curves of type d are ones that do not have
a definite peak. They are termed odd-shaped. Soils with a liquid limit greater than about 70 may
exhibit compaction curves of type c or d. Soils that produce c- and d-type curves are not very
common.
TABLE 8 Specification for Standard Proctor test (Based on ASTM Test Designation 698-91)
Item
Diameter of mold
Volume of mold
Weight of hammer
Height of hammer drop
Number of hammer blows per
layer of soil
Number of layers of compaction
Energy of compaction
Soil to be used
Method A
101.6 mm
943.3 cm3
24.4 N
304.8 mm
Method B
101.6 mm
943.3 cm3
24.4 N
304.8 mm
Method C
152.4 mm
2124 cm3
24.4 N
304.8 mm
25
25
56
3
591.3 KN-m/m3
Portion passing
No.4 (4.57 mm)
sieve. May be used
if 20 % or less by
weight of material
is retained on No. 4
sieve.
3
591.3 KN-m/m3
Portion passing 9.5
mm sieve. May be
used if soil retained
on No. 4 sieve is
more than 20%, and
20 % or less by
weight retained on
9.5 mm sieve.
3
591.3 KN-m/m3
Portion passing 19
mm sieve. May be
used if more than
20%,by weight of
material retained on
9.5 mm sieve, and
less than 30% by
weight retained on
19 mm sieve.
50
TABLE 9 Specifications for Modified Proctor test (based on ASTM Test Designation 1557-91)
Item
Method A
Method B
Method C
Diameter of mold
Volume of mold
Weight of hammer
Height of hammer drop
Number of hammer blows per
layer of soil
Number of layers of compaction
Energy of compaction
Soil to be used
101.6 mm
943.3 cm3
44.5 N
457.2 mm
101.6 mm
943.3 cm3
44.5 N
457.2 mm
152.4 mm
2124 cm3
44.5 N
457.2 mm
25
25
56
5
2696 KN-m/m3
Portion passing
No.4 (4.57 mm)
sieve. May be used
if 20 % or less by
weight of material
is retained on No. 4
sieve
5
2696 KN-m/m3
Portion passing 9.5
mm sieve. May be
used if soil retained
on No. 4 sieve is
more than 20%, and
20 % or less by
weight is retained
on 9.5 mm sieve
5
2696 KN-m/m3
Portion passing 19
mm sieve. May be
used if more than
20%,by weight of
material retained on
9.5 mm sieve, and
less than 30% by
weight retained on
19 mm sieve
51
PRELIMINARY DATA SHEET
Name: ________________________________________
Course/Section: ________________________________
Group No._________________________
Date: _____________________________
Experiment No. 5
SOIL COMPACTION TEST
Trial No.
1
2
3
4
5
Weight of compacted soil + mold (grams)
Volume of water used (ml)
Weight of can (grams)
Weight of wet soil + can (grams)
Weight of dry soil + can (grams)
Moisture loss (grams)
Moisture content (%)
Weight of wet soil (grams)
Weight of dry soil (grams)
Wet unit weight (grams/cm3)
Dry unit weight (grams/cm3)
Weight of mold (grams)
Maximum dry density (grams/cm3)
Optimum Moisture Content (%)
___________________________
Student’s Signature
___________________________
Instructor’s Signature
52
FINAL DATA SHEET
Name: ________________________________________
Course/Section: ________________________________
Group No._________________________
Date: _____________________________
Experiment No. 5
SOIL COMPACTION TEST
Trial No.
1
Weight of compacted soil + mold (grams)
Volume of water used (ml)
Weight of can (grams)
Weight of wet soil + can (grams)
Weight of dry soil + can (grams)
Moisture loss (grams)
Moisture content (%)
Weight of wet soil (grams)
Weight of dry soil (grams)
Wet unit weight (grams/cm3)
Dry unit weight (grams/cm3)
Weight of mold (grams)
Maximum dry density (grams/cm3)
Optimum Moisture Content (%)
___________________________
Student’s Signature
53
2
3
4
5