FACULTY OF ENGINEERING TECHNOLOGY
DEPARTMENT OF CIVIL ENGINEERING TECHNOLOGY
ENGINEERING TECHNOLOGY GEOTECHNIC LABORATORY
(MAKMAL TEKNOLOGI KEJURUTERAAN GEOTEKNIK)
LABORATORY REPORT
COURSE CODE AND NAMA
KOD DAN NAMA KURSUS
EXPERIMENT NO.
BNP 20903 / SOIL MECHANIC AND FOUNDATION
E4
NO. UJIKAJI
EXPERIMENT TITLE
PROCTOR COMPACTION TEST
TAJUK UJIKAJI
DATE OF EXPERIMENT
TARIKH UJIKAJI
GROUP NO.
NO. KUMPULAN
24 APRIL 2022 (SUNDAY)
NAME
7
MATRIX NO.
1. LAAWANYA A/P MANIMARAN
CN200067
2. HANIS SUFI BINTI MOHAMAD ADAM
AN200056
3. SHAREENA SIAN ANAK INNIT
CN200017
4. KOGULA CHEILVEAN A/L
THAMILSELVAN
5. AININ SOFIYA BINTI MOHAMMAD
FAIZAL
CN200162
CN200102
LECTURER / INSTRUCTOR
1. Ts.Dr. TUAN NOOR HASANAH BINTI TUAN ISMAIL
PENSYARAH / INSTRUKTUR
2. PROF. Dr. CHAN CHEE MING
RECEIVED DATE AND STAMP
TOTAL MARK (FROM RUBRIC
ASSESSMENT)
JUMLAH MARKAH (DARI RUBRIK
PENILAIAN)
8 MAY 2022 (SUNDAY)
STUDENT CODE OF ETHICS
DEPARTMENT OF CIVIL ENGINEERING TECHNOLOGY
FACULTY OF ENGINEERING TECHNOLOGY
I hereby declare that I have prepared this report with my own efforts. I also admit to not accept or
provide any assistance in preparing this report and anything that is in it is true.
1) Group Leader
Name
Matrix No.
:
:
Laawanya
LAAWANYA A/P MANIMARAN
CN200067
2) Group Member 1
Name
:
Matrix No.
:
Hanis Sufi
HANIS SUFI BINTI MOHAMAD ADAM
AN200056
3) Group Member 2
Name
:
Matrix No.
:
Shareena Sian
SHAREENA SIAN ANAK INNIT
CN200017
4) Group Member 3
Name
:
Matrix No.
:
Kogula
KOGULA CHEILVEAN A/L THAMILSELVAN
CN200162
5) Group Member 4
Name
:
Matrix No.
:
Ainin Sofiya
AININ SOFIYA BINTI MOHAMAD FAIZAL
CN200102
Faculty of Engineering Technology
Universiti Tun Hussein Onn Malaysia
Pagoh, Johor, Malaysia.
Sem.2 Ses.2021/2022
BNP20903 SOIL MECHANICS AND FOUNDATION
LABORATORY RUBRIC ASSESSMENT (LAB REPORT)
CLO 3
Organize geotechnical as well as geo-environmental laboratory and in-situ measurements with practical considerations (PO5, SK3, SK4,
SK6, SP1, SP3, SP7 – Modern Tool Usage)
Level of Achievement
Elements
Very Week (1)
Weak (2)
Modest (3)
Background
information is
accurate, but
irrelevant or too
disjointed to make
relevance clear
Background
information is
overly narrow or
overly general (only
partially relevant).
Good (4)
Excellent (5)
Level
Weight
Score
P2
2
/10
SP1-SK3 (Engineering fundamentals) – 10%
Introduction/
Theoretical
Background
(Briefly explain)
Background
information is
missing or
contains major
inaccuracies.
Background
information may
contain minor
omissions or
inaccuracies that do
not detract from the
major point.
The introduction is
thorough and wellwritten, and it provides
all of the necessary
background principles
for the experiment.
- Most materials and
equipment are listed.
- Procedure contains
most steps.
- Most safety
precaution of the test
are listed.
- All Materials and
equipment are correctly
stated.
- Procedure is complete
and easy to follow.
- Safety precaution of the
test well explain.
P4
3
/15
- All data are
documented and
graphed, and but
minor analysis is
incorrect.
- Data fully utilized
and sufficient to test
theory.
- Appropriate use of
visuals, pictures or
other graphics to
display data and
results.
- All data are
documented, graphed
and analyzed well.
- Additional data
collection designed to
answer questions and
test ideas.
- Creative and highly
technical use of visuals,
pictures or other
graphics to display and
explain fine points of
data and results.
P4
4
/20
P4
4
/20
P3
3
/15
P3
2
/10
P5
2
/10
SP1-SK6 (Engineering Technologies) – 15%
Demonstrate
- No materials and - Some materials
- Materials and
familiarity with the
equipment are
and equipment are
equipment are
experiment.
listed.
listed, with minor
listed.
(in term of
- Procedure and
error.
- Procedure is
procedure, safety and safety precaution - Poorly explained /
missing steps and
precaution)
sections are
indecipherable.
difficult to follow.
missing.
SP3 (Depth of analysis) – 20%
Measurement/
Data/ Analysis
- All data are
missing or
incorrect and no
analysis.
- No use of theory
to interpret data.
No idea what to
do with data.
- No visuals,
pictures or other
graphics to
display data.
- Most data are
- Most data are
missing or
documented and
incorrect and not
graphed. Mostly
analyze well.
analysis is
- Minimal use of
incomplete or
theory to interpret
incorrect.
observation/data
- Limited use of
- Inadequate use of
theory to interpret
visuals, pictures or observation/data
other graphics to
- Inadequate use of
display data and
visuals, pictures or
result.
other graphics to
display data/result.
SP1-SK4 (Specialist knowledge) – 25%
Comprehensive
Discussion and
Conclusion
(Able to relate
findings to the
theory/standard or
real application)
Respond to Q&A
(Display
understanding)
- Incomplete or
- Limited discussion - Some of the results - Almost all the results - All significant trends
incorrect trend
of the results;
have been correctly
have been correctly
and data comparisons
interpretation and indicating a lack
interpreted and
interpreted and
have been correctly
data comparison
of understanding
discussed; however,
discussed; only
interpreted and
indicating a lack
of results.
there is still a partial minor improvements
discussed, and a good
of understanding
but incomplete
are required.
understanding of the
of results
understanding of
results has been
the results.
conveyed.
Unable to
Minimum ability
Limited ability to
Able to respond and
Able to respond and
respond and
to answer and
answer and
answer constructively answer constructively at
answer to the
sometimes do not
sometimes do not
most of the time.
all times with relevant
question
match the
match the question.
references
accordingly.
question.
SP7 (Interdependence) – 20%
Use of Sources
(citations and
references)
>>include standard
used
Format and
Organization
- 0 external
reference cited
or not relevant.
- Bibliography is
missing or
contains major
inaccuracies.
- 1-2 external
- 3-4 external
references cited.
reference cited.
- Very poor
- Bibliography is
citation and
incomplete or
bibliography
citations are
format with many inconsistent.
mistakes.
- Appears to have - Disorganized.
no direction, with Section/
subtopics
paragraphs not
appearing
well integrated.
disjointed.
- The required
- Few or no topic
information is
sentences, with
difficult to locate
poorly
within the report.
constructed
- Inconsistent
paragraph.
formatting.
- 5 external
- More than FIVE
references cited.
external references
- Bibliography mostly cited.
complete or
- Citation and
citations are
bibliography are
consistent.
written in
appropriately format
and matches in-test
references.
- Not organized well. - Clear organization,
- Clear organization.
Mostly section/
but not all sections
Paragraphs complete,
paragraphs is not in
/paragraphs follow in
yet concise with strong
a logical order.
a logical order.
topic sentences
- Occasionally
- Occasionally lacking
indicating the focus of
lacking topic
topic sentences.
each paragraph.
sentences.
- Formatting mostly
- Transitions tie sections
- Inconsistent
consistent.
together, as well as an
formatting.
adjacent paragraph.
- Formatting consistent
throughout.
Total Marks
/100
1.0
OBJECTIVE
i.
To determine the relationships between moisture content and dry
density of soil by standard proctor compaction test.
ii.
To determine the optimum moisture content at which the given soil
type will become most dense and achieve its maximum dry density.
2.0 INTRODUCTION
Proctor (1933) developed a laboratory compaction test procedure to
determine the maximum dry density of compaction of soils for a given
compactive effort depends on the amount of water in the soil during compaction.
This test is referred to as the Standard Proctor Compaction Test and is based
on the compaction of the soil fracture passing No. 4 sieve. The purpose of
laboratory compaction test is to determine the proper amount of water at which
the weight of the soil grains in a unit volume of the compacted is maximum, the
amount of water is thus called the Optimum Moisture Content (OMC), which can
be used for specification of field compaction.
Compaction of soil increases the density, shear strength, stiffness, bearing
capacity, thus reducing the voids, settlement and permeability. The results of
this are useful in the stability of field problems like earthen dams, embankments,
roads and airfield. In such compacted in the field is controlled by the value of
the OMC determined by laboratory compaction test. The compaction energy to
be given by a compaction unit is also controlled by the maximum dry density
determined in the laboratory. In other words, the laboratory compaction tests
results are used to write the compaction specification for field compaction of the
soil.
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
1
3.0 THEORY
Compaction of soil the process by which the solid particles are packed more
closely together by mechanical means, thus increasing the dry density,
Markwick, 1994. It is achieved through the reduction of the air voids in the soil.
At low moisture content, the soil grain is surrounded by a thin film of water,
which tends to keep the grains apart even when compacted. In addition of more
water, up to certain point, more air to be expelled during compaction. At the
point, soil grains become as closely packed together as they can, that is at the
dry density is at its maximum. When the amount of water exceeds the required
to achieve this condition, the excess water begin to push particles apart, so the
dry density reduced.
The moisture content at which the greatest value of dry density achieved for the
given compaction effort is the optimum moisture content, (OMC), and the
corresponding dry density is the maximum dry density (𝜌𝑑) as shown in Figure
3.1.
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
2
Zero-air void line (100% saturation line)
Figure 3.1: Relationship between dry density (𝝆𝒅) against moisture content
(w) for difference types of soil.
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
3
4.0
TEST EQUIPMENTS
SPECIAL EQUIPMENT:
1. Cylindrical metal mould, internal dimensions 105mm diameter and 115.5mm high.
(fitted with a detachable and removable extension collar.
2. Standard proctor hammer with 50mm diameter face weighing 2.5kg, sliding
freely in a tube which controls the height of drop to 300mm
3. Measuring cylinder; 200ml or 500ml (plastic)
4. Sieve no. 4 and receiver.
Extension collar
Pins to form catch for collar
Cylindrical mould
Base plate
Standard proctor
hammer (weight 2.5kg)
Figure 4.1: Proctor compaction mould and hammer
GENERAL EQUIPMENT:
1. Large metal tray
2. Balance of capacity 10kg, and sensitivity up to 0.1g.
3. Balance of capacity of 500g, and sensitivity up to 0.01g.
4. Jacking apparatus for extracting compacted material from mould.
5. Small tools: palette knife, steel-straight edge, 300mm long, steel rule,
scoop or garden trowel
6. Drying oven, 105°C and other equipment for moisture content determination.
7. Distilled water.
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
4
5.0 PROCEDURE
1. Took about ± 3kg of oven-dried soil sample that the had passing through sieve no. 4
(4. 75mm)
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
5
2. - Added 8% of watered to 3kg of soil sample and mixed well.
- Left the mixed to mature for few minutes.
3. - Verify the mould, base plate, extension collar and hammer have been used were those
that conform to bs 1377.
- Clean and grease gently the inside surface of the mould, and the base plate.
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
6
4. - Poured the moist soil in three equal layers.
- Compact each layer uniformly by applying 27 blows of the hammer dropping from the
controlled height of the 300mm
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
7
5. Repeated for the second- and third-layers compaction, the soil should not more than 6mm
above the mould body.
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
8
6.0
PRECAUTIONS
1. Adequate period is allowed to mature the soil after it is mixed with water.
2. The rammer blows should be uniformly distributed over the surface with
spatula before next layer is placed
3. To avoid stratification each compacted layer should be scratched with
spatula before next layer is placed.
4. At the end of compaction test, the soil should not penetrate more than 5mm into the
collar.
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
9
7.0
CALCULATIONS
1. Calculate the internal volume of the mould (V)mm3 using:
2. Calculate the bulk density, ρ of each compacted specimen from the equation:
3. Calculate moisture content, wn (%) for each compacted specimen.
4. Calculate corresponding dry density, ρd
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
10
5. Calculate dry unit weight
6. Determine zero air void unit weight
The maximum theoretical dry unit weight of a compacted soil at a given
moisture content will occur when there is no air left in the void spaces of the
compacted soil. This can be given by:
Since the values of 𝛾𝑤 and 𝐺𝑠 will be known, several values of w (%) can be assumed
and 𝛾𝑠𝑎𝑣 can be calculated.
7. Plot of graph dry density, ρd against moisture content, wn. Draw a smooth
curve through the points.
From the graph, determine the maximum dry unit weight compaction, 𝛾𝑑(𝑚𝑎𝑥).
Also determine the optimum moisture content (OMC), which is the moisture
content corresponding to 𝛾𝑑(𝑚𝑎𝑥). On the same graph, plot 𝛾𝑠𝑎𝑣 versus
w(%).
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
11
8.0
DATA ANALYSIS (result and calculation)
(a)
Show example of calculation
(b)
Graph - Plot of graph dry density, ρd against moisture content, wn. Draw
a smooth curve through the points.
(c)
From the graph, determine the maximum dry unit weight compaction,
𝛾𝑑(𝑚𝑎𝑥). Also, determine the optimum moisture content (OMC)
corresponding to maximum dry density,
𝛾𝑑(𝑚𝑎𝑥).
(d)
In the same graph, plot 𝛾𝑠𝑎𝑣 versus w (%).
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
12
8.1 DATA SHEET
No. of layer :3
A: TEST CRITERIA
Soil Description :
Rammer mass :
2.5 kg
Kaolin
Blows per layer :
No. of separate
Sample Preparation :
27
batch : 3
Air dried and riffled
B: DENSITY CALCULATION (VOLUME OF CYLINDER = 0.90 cm3
Measurement No.
(1)
(2)
(3)
(4)
(5)
Mass of cylinder mould = m1 (kg)
4.241
4.241
4.241
4.241
4.241
Mass of Cylinder mould + moist soil
= m2 (kg)
5.863
5.939
6.040
5.991
5.952
Soil mass, m3 = m1 – m2(kg)
1.622
1.689
1.799
1.750
1.711
Bulk density, 𝜌𝑏(g/cm3)
1.802
1.887
1.999
1.944
1.901
Dry density
1.514
1.547
1.599
1.484
1.419
Unit weight
17.68
18.41
19.61
19.08
18.65
Dry unit weight
14.86
15.09
15.69
14.56
13.92
Zero air void unit weight
17.29
16.42
15.64
14.27
13.68
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
13
C: MOISTURE CONTENT
(% water = 15% = 450ml)
Measurement No. 1
(1)
Mass of can = m1 (g)
20.0
Mass of can + moist soil = m2 (g)
57.0
Soil mass, m3 =m1 – m2 (g)
37.0
Mass of dry soil + container = m4(g)
51.2
Moisture content, w (%),
19%
(% water = 4% = 120ml)
Measurement No. 2
(1)
Mass of can = m1 (g)
25.0
Mass of can + moist soil = m2 (g)
69.0
Soil mass, m3 =m1 – m2 (g)
44.0
Mass of dry soil + container = m4(g)
61.0
Moisture content, w (%),
22%
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
14
(% water = 4% = 120ml)
Measurement No. 3
(1)
Mass of can = m1 (g)
21.0
Mass of can + moist soil = m2 (g)
49.0
Soil mass, m3 =m1 – m2 (g)
28.0
Mass of dry soil + container = m4(g)
43.4
Moisture content, w (%),
25%
(% water = 4% = 120ml)
Measurement No. 4
(1)
Mass of can = m1 (g)
25.0
Mass of can + moist soil = m2 (g)
81.0
Soil mass, m3 =m1 – m2 (g)
56.0
Mass of dry soil + container = m4(g)
67.8
Moisture content, w (%),
31%
(% water = 4% = 120ml)
Measurement No. 5
(1)
Mass of can = m1 (g)
20.0
Mass of can + moist soil = m2 (g)
71.0
Soil mass, m3 =m1 – m2 (g)
51.0
Mass of dry soil + container = m4(g)
58.0
Moisture content, w (%),
34%
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
15
D: DRY DENSITY CALCULATION (USE ACTUAL VOLUME OF CYLINDER)
Measurement No.
(1)
(2)
(3)
(4)
(5)
Dry density, ρd
1.514
1.547
1.599
1.484
1.419
i.
Example of calculation (B) – Soil Mass
Soil mass, m3 = m1 – m2(kg)
m1 = 4.241 kg
m2 = 5.863 kg
m3 = 4.241kg – 5.863kg
= 1.622kg
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
16
ii. Example of calculation (B) - the bulk density, ρ
𝜌=
=
𝑚2 −𝑚1
𝑣
5.863 − 4.241
0.90
= 1.802
𝑔
𝑐𝑚3
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
17
iii. Example of calculation (C) - moisture content, wn (%)
𝑤𝑛 =
=
𝑚4 −𝑚5
𝑚5 −𝑚3
× 100%
57.0 −51.2
51.2 − 20.0
× 100%
= 19%
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
18
iv. Example of calculation (D) - corresponding dry density, ρd
Where,
𝜌 = 𝐵𝑢𝑙𝑘 𝐷𝑒𝑛𝑠𝑖𝑡𝑦 𝑔/𝑐𝑚3
w (%) = 𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 (%)
𝜌𝑑 =
1.802
19%
1 + 100%
= 1.514
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
19
v. Example of calculation (B) – unit weight, 𝜸
𝑚𝑔
𝛾=
𝑣
Where,
𝑚 = 𝑠𝑜𝑖𝑙 𝑚𝑎𝑠𝑠
𝑔 = 9.81
𝑣 = 𝑣𝑜𝑙𝑢𝑚𝑒 𝑜𝑓 𝑐𝑦𝑙𝑖𝑛𝑑𝑟𝑖𝑐𝑎𝑙 𝑚𝑜𝑢𝑙𝑑
𝛾=
(1.622)(9.81)
0.90
= 17.68
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
20
vi. Example of calculation (B) - dry unit weight,
𝛾
𝛾𝑑
= 𝑢𝑛𝑖𝑡 𝑤𝑒𝑖𝑔ℎ𝑡
w (%) = 𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 (%)
17.68
𝛾𝑑 =
19%
1 + 100%
= 14.86
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
21
vii. Example of calculation (B) - zero air void unit weight
The maximum theoretical dry unit weight of a compacted soil at a given
moisture content will occur when there is no air left in the void spaces of the
compacted soil. This can be given by:
𝛾𝑤 = 9.81
𝐺𝑠 = 2.65
w (%) = 𝑀𝑜𝑖𝑠𝑡𝑢𝑟𝑒 𝐶𝑜𝑛𝑡𝑒𝑛𝑡 (%)
𝛾𝑠𝑎𝑣 =
9.81
19%
1
+
100
2.65
= 17.29
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
22
E: PLOTTING OF DRY DENSITY AGAINST MOISTURE CONTENT WITH AIR VOIDS
LINE AT 0%, 5% AND 10%. USE PROPER GRAPH PAPER
Measurement No.
(1)
(2)
(3)
(4)
(5)
Dry density, ρd
1.514
1.547
1.599
1.484
1.419
19%
22%
25%
31%
34%
17.29
16.42
15.64
14.27
13.68
Moisture content, w
(%),
Zero air void unit
weight
Graph dry density against moisture content with air voids line at 0%, 5%
and 10%
1.65
max.dry density = 1.6 g/cm3
1.6
25%, 1.599
22%, 1.547
19%, 1.514
1.5
31%, 1.484
1.45
optimum moisture content = 25%
Dry density, ρd
1.55
1.4
1.35
1.3
1.25
34%, 1.419
Dry Density vs Moisture
Content
1.2
0%
5%
10%
15%
20%
25%
30%
35%
40%
Moisture content, w (%)
Figure 1: Dry Density Vs Moisture Content
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
23
Graph zero air void unit weight against moisture content with air voids
line at 0%, 5% and 10%
20
25%, 15.64
18
Zero Air Void Unit Weight
16
14
12
10
zero air void unit weight
8
6
4
2
0
0%
5%
10%
15%
20%
25%
30%
35%
40%
Moisture content, w (%)
Figure 2: Zero Air Voids Curve
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
24
Graph dry density and zero air void unit weight against moisture content
with air voids line at 0%, 5% and 10%
20
18
16
Dry density, ρd
14
34%, 13.68
12
Dry density, ρd
10
Zero Air Void Unit Weight
8
6
4
2
34%, 1.419
0
0%
5%
10%
15%
20%
25%
30%
35%
40%
Moisture content, w (%)
Figure 3: Showing the Zero air voids curve and the Dry Density vs Moisture content
LAB EXPERIMENT 4
STANDARD PROCTOR COMPACTION TEST
25
9.0 DISCUSSION
During construction, compaction is essential to increase the shear strength, decrease
the compressibility, decrease its permeability and minimize long-term settlement in the
soil. It is difficult to check those objectives directly therefore they are checked indirectly
by finding the optimum moisture content and dry unit density.
By finding the optimum moisture content and maximum dry density, this allows civil
engineers to gauge the soils strength. When soils close to 0% moisture content, the soil
becomes stiff and offers more resistance to compaction. This is due to the voids of soil
particles that are completely filled with air, making the water content 0%. The soil can
only be compacted when water is added, because the water lubricates the particles
making compaction easier. The soil mass becomes more workable and the particles
have closer packing. To add, the dry density of soil increases with an increase in the
water content till the optimum water content in reached.
As more water is added and the water content becomes larger than the optimum
values, the void spaces become filled with water so further compaction is not possible.
Beyond this point, the dry density decreases as shown in Figure 1. The points at which
this begins to happen is described as the optimum moisture content and the maximum
dry unit weight. In this test the Optimum Moisture Content and dry unit weight were
found to be 25% saturation and 1.6 g/cm3 . For any given water content and soil solids,
the zero-air-voids dry unit weight represents the best possible compaction. As shown in
the Figure 3 the actual compaction curve was below the zero voids curve which is an
expected result.
For a given soil and water content the best possible compaction is represented by the
zero-air-voids curve on Chart 3. The actual compaction curve will always be below it.
Compaction of soil increases the density, shear strength, bearing capacity, thus reducing
the voids, settlement and permeability. Hence the optimum moisture content and the
maximum dry density are useful in the stability of field problems like earthen dams,
embankments, roads and airfields. Compaction in the field is controlled by the value of
the optimum moisture content determined by laboratory compaction test. In other words,
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the laboratory compaction tests results are used to write the compaction specifications
for field compaction of the soil.
The sources of error that normally occur during the test is:
i.
Water may not have been thoroughly absorbed into the dry soil. As a precaution an
adequate period should be allowed to mature the soil after it is mixed with water.
ii.
Each layer of soil may not have been the same depth into the collar of the mould as a
precaution proper care should be taken to make sure that each layer is nearly equal
in weight. To avoid stratification each compacted layer should be scratched with
spatula before next layer is placed.
iii.
Human error in operating the hand rammer, it is impossible to apply the same
compaction energy to each layer. A possible precaution that could be taken is to
ensure that the same person applies the blows to each layer. Another will be to
ensure the rammer blows are uniformly distributed over the surface.
iv.
Moisture from ungloved hands when handling the soil can also contribute to the
changes of moisture content of the soil.
Improvements for the test:
i.
More accurate results could be obtained if the manual compacting hammer was
replaced with a mechanical arm along with using a fixed height and fixed force to
uniformly compact the sample.
ii.
Wearing gloves and using spatula when scooping the soil specimen into the can or
during mixing process of soil with water.
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10.0
CONCLUSION
To conclude, the dry density of the soil increases with an increase in the water
content till the optimum water content in reached. At that stage, the air voids attain
approximately a constant volume. With further increase in water content, the air voids
do not decrease, but the total voids (air plus water) increase and the dry density
decreases. Thus, the higher dry density is achieved up to the optimum water content
due to forcing air voids out from the soil voids. After the optimum water content is
reached, it becomes more difficult to force air out and to further reduce the air voids.
The effect of water content on the compaction of soil can also be explained
with the help of electrical double layer theory. At low water content, the forces of
attraction in the adsorbed water layer are large, and there is more resistance to
movement of the particles. As the water content is increased, the electrical double
layer expands and the inter-particle repulsive forces increase. The particles easily
slide over one another and are closely packed. This results in higher dry density.
Next, the compaction of soil increases with the increase in amount of
compactive effort. With increase in compactive effort, the optimum water content
required for compaction also decreases. At a water content less than the optimum,
the effect of increased compaction is more predominant. At a water content more
than the optimum, the volume of air voids become almost constant and the effect of
increased compaction on soil is not significant.
It may be mentioned that the maximum dry density does not go on increasing
with an increase in the compactive effort. For a certain increase in the compactive
effort, the increase in the dry density becomes smaller and smaller. Finally, a stage is
reached beyond which there is no further increase in the dry density with an increase
in the compactive effort.
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11.0 QUESTIONS
1. What principles and process involved in soil compaction?
The objective of compaction is to achieve maximum possible dry density of the
compacted soil. The water content used for compaction controls the dry density
achieved. When water is added to the soil during compaction, it acts as a softening
agent in the soil particles. The soil particles slip over each other and move into a
densely packed position. The dry unit weight after compaction first increases as the
moisture content increases. When the moisture content is gradually increased and
the same compaction effort, the weight of the soil solids in a unit volume gradually
increases. Beyond a certain moisture content, any increase in the moisture content
tends to reduce the dry unit weight. This phenomenon occurs because the water
takes up the spaces that would have been occupied by solid particles. The moisture
content at which the maximum dry density (MDD) is attained is generally referred to
as the optimum moisture content (OMC).
2. Why does the dry unit weight of the moist soil first increase with an increase in
moisture content and then decrease?
If we add moisture little by little and check the dry density, we can see a decreasing
increment. On one occasion all the voids fill with moisture. If we keep adding
moisture after that also what happen is moisture try to displace soil particles. But soil
particles are far denser than water particles. Therefore, with adding excessive water
amount we can see a gradual decrement of dry density. So, at particular moisture
content we can obtain the maximum dry density in the experiment.
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3. How compaction process can be accomplished in the field?
There are several methods used to compact soil. All methods involve a static and/or
dynamic force along with manipulation of the soil. Static force uses the pressure of a
weight to physically and continuously compact soil. Manipulation, such as kneading
or shearing the soil in alternating movements, can compact soil at greater depths. In
conjunction with pressure and manipulation, dynamic force can be applied by adding
a vibrating mechanism. Vibratory compaction methods use different amplitudes (the
amount of movement on an axis) and frequencies (the speed of the movement) to
apply force in alternating directions, usually by the use of a rotating weight, to deliver
rapids blows to the surface. This rearranges the soil particles so compaction not only
occurs at the top layers but also in the deeper layers of the soil.
4. In soil compaction test, if a test result exceeds 100%, should engineers accept the
result?
For soil compaction tests, the dry density obtained from compaction carried out in –
situ by vibrating roller/vibrating plate is compared with the maximum dry density
conducted in laboratories using 2.5kg rammer of compaction with similar soils.
Essentially, the in – situ compaction is compared with the compacting effort of using
2.5kg (or 4.5kg) rammer in laboratories. In case the compaction test results indicate
values exceeding 100%, it only means that the in – situ compaction is more than that
being carried out in laboratories which is treated as the basic criterion for satisfactory
degree of soil compaction. Therefore, the soil results are acceptable in case
compaction test results are over 100%.
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REFERENCE
1. Compaction of Soil: Definition, Principle and Effect | Soil Engineering. (2018,
February
16).
Soil
Management
India.
https://www.soilmanagementindia.com/soil/soil-compaction/compaction-of-soildefinition-principle-and-effect-soilengineering/13769#:~:text=The%20principle%20of%20compaction%20was
2. In soil compaction test, if a test result exceeds 100%, should engineers accept the
result? (n.d.). Www.engineeringcivil.com. https://www.engineeringcivil.com/in-soilcompaction-test-if-a-test-result-exceeds-100-should-engineers-accept-theresult.html
3. Soil Compaction: Methods, Meaning, and Effects. (2020, July 17). Mintek
Resources.
https://mintekresources.com/soil-compaction-methods-meaning-
effects/
4. Soil Compaction. (n.d.). https://people.utm.my/nzurairahetty/files/2020/02/4.-SoilCompaction-Laboratory-Week-5.pdf
5. Beck, K. (2020, December 22). How to calculate unit weight. Sciencing. Retrieved
May 7, 2022, from https://sciencing.com/calculate-unit-weight-8085575.html
6. Why do we need to know the soil moisture content of soil? Van Walt News. (2018,
September
27).
Retrieved
May
8, 2022,
from https://www.vanwalt.com/news/2015/04/08/why-do-we-need-to-know-thesoil-moisture-content-of-soil/
7. Water
content
(W). Geoengineer.org.
(n.d.).
Retrieved
May
8, 2022,
from https://www.geoengineer.org/education/laboratory-testing/water-contentw#:~:text=The%20water%20content%20(w)%2C,to%20zero%20(dry%20soil).
8. Mishra, G. (2021, May 14). Factors affecting compaction of soil - effect on
different
soil
types.
The
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Retrieved
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from https://theconstructor.org/geotechnical/factors-affecting-compaction-ofsoils/5311/?amp=1
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