COMPACTION TEST
[Document subtitle]
OCTOBER 24, 2023
UNIVERSITY OF COLORADO DENVER
Geotechnical Engineering I
Table of Contents
1.
COMPACTION TEST (STANDARD AASHTO) ........................................................................................... 2
1.1
OBJECTIVE ..................................................................................................................................... 2
1.2
TEST PURPOSES ............................................................................................................................. 2
1.3
APPARATUS ................................................................................................................................... 3
1.4
PROCEDURE .................................................................................................................................. 3
1.5
PRECAUTIONS ............................................................................................................................... 4
1.6
FACTORS AFFECTING THE RESULTS OF COMPACTION TEST ......................................................... 5
1.7
OBSERVATIONS AND CALCULATIONS ........................................................................................... 5
1.8
RESULTS......................................................................................................................................... 6
1
1.
COMPACTION TEST (STANDARD AASHTO)
1.1
OBJECTIVE
The purpose of this standard compaction test is to determine the soil's moisture density relationship for
a certain compactive effort.
1.2
TEST PURPOSES
Compaction is a form of mechanical stabilization in which mechanical energy, also called compactive
effort, is applied to a mass of soil in order to make it denser. Dynamic load, static load, vibration, and
tamping are all viable options for generating the necessary mechanical energy. When soil is compacted,
the particles are pushed around and the air volume is decreased.
There are three (03), significant impacts caused by soil compaction's increase in density:
1. The soil's shear strength increase
2. Decrease in the future settlement,
3. Decrease in the Permeability
All construction projects must consider these three consequences. The advantages, as a whole, tend to
amplify as the degree of compacting rises. Soil compaction is a cost-effective and straightforward method
for enhancing soil quality.
The estimation of compaction level can be derived from the density of the soil, which is commonly
referred to as its dry unit weight. In order to enhance the density of arid soil by compaction, it is advisable
to introduce a certain quantity of water to each distinct soil type individually. Water functions as a
lubricating agent, facilitating the densification of soil particles through increased compaction. Put simply,
there exists an optimal level of moisture that allows for the driest density to be achieved with the least
amount of compaction work. The moisture level and dry density might be conceptualized as the "Optimal
Moisture Content" and "Maximum Dry Density," respectively.
Conducting laboratory compaction tests on representative samples obtained from the construction site is
a customary procedure within the construction industry. These studies aim to ascertain the Optimal
Moisture Content and Maximum Dry Density, which are crucial parameters for building projects. The
determination of design shear strength, future settlement resistance, and permeability necessitates the
utilization of Maximum Dry Density by the designer. The soil is subsequently compressed in the field to
achieve an equivalent Maximum Dry Density (or percentage) as was achieved during laboratory testing.
The verification of the Maximum Dry Density (or a proportion thereof) can be achieved by the utilization
of in-situ soil density testing.
2
There exist two distinct methodologies for establishing the correlation between moisture content and
density:
1. The AASHO Standard Proctored Exam.
2. Exam in a modified Proctor (AASHO-like)
1.3
APPARATUS
1. The height, internal diameter, and volume of a compaction mould measuring 4.58 inches, 4 inches,
and 0.30 cubic feet, respectively.
2. A common compaction rammer (weighing 5.5 lbs and dropping 12 inches)
3. Moisture tins
4. Big spoon for stirring
5. Large spoon for mixing
6. Knife for trimming
7. Steel straight edge
8. Oven for drying
9. Scales for weighing (Least count = 0.01 gram)
10. Scales for weighing (Least count = 1.0 gram)
1.4
PROCEDURE
1. Gather a sample of dirt that passes the U.S. No. 4 sieve and has been air-dried to a weight of around
3 kilograms. If you must break up the material, do so in a method that causes as little stress as possible
on the soil particles.
2. After determining the soil sample's dry weight through analysis, add water until the desired
consistency is reached. Sandier soils should have around 7% water added to them compared to the
dry weight, whereas clayier soils should have about 10% water added to them relative to the dry
weight. To hasten the soil's development, it's best to keep it in a sealed container for 20 hours, during
which time a hermetic atmosphere can be maintained.
3. When compared to the collar and the base plate, the compaction mould must be lighter.
4. It is necessary to take a measurement of the compaction mold's volume. Join the mold's collar and
base plate together.
5. The standard compaction method should be used during the soil compaction process. The compaction
procedure should be carried out in three uniform layers, with 25 blows from a 5.5-pound rammer
dropped from a height of 12 inches landing on each layer. It is crucial to make sure the effects
permeate all levels equally. Soil should be used to fill the mould, with a small excess of about 14 inch
that may be removed when the collar is taken off.
3
6. Be careful when taking off the collar and the bottom plate. Use a straight edge to strike the top and
bottom of the cylinder of compacted earth. Extra soil should be added to the crushed specimen if
there are any gaps inside.
7. First, you need to get rid of the mould growing on the outside, and then you may weigh it to within a
gramme.
8. To determine the soil's moisture content, we need to remove the cylinder of soil from the mould,
divide it, and then remove a sample.
9. The presented material needs to be separated into particles small enough to fit through a No. 4 sieve.
Additionally, 2 percent of the sample's starting weight in water should be added. After reaching a
peak value as indicated by wet weights, the process should be restarted and replicated until two
slightly lower compressed weights are achieved.
10. The following day, take the water content samples that were dried in the oven and bring them to the
lab for analysis. This will allow for precise measurement of water content in each sample.
11. The purpose of this research was to provide a visual representation of the saturation curve, often
known as the zero air void line.
1.5
PRECAUTIONS
1. Blows should be delivered consistently throughout all soil levels.
2. Do not add dirt to fill in the mould if the last compacted layer did not reach over the collar joint. Try
the test again and again.
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1.6
FACTORS AFFECTING THE RESULTS OF COMPACTION TEST
Several factors will determine how much of a compact may be achieved:
i.
Soil type (sandy or clay), texture (fine or coarse), and adaptability
ii.
Compaction-time water content
iii.
Environmental, topographical, and stratigraphic features of the site
iv.
Both the plant's characteristics and the amount of work put in to compact the soil are factors.
1.7
OBSERVATIONS AND CALCULATIONS
Water Content Determination
Sample No
1
2
3
4
5
Moisture cup no.
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
Mass of cup + wet soil (g)
43
53
38
46
35
36
54
47
49
48
Mass of cup + dry soil (g)
39
48
34
42
31
33
45
41
41
41
Mass of water, Mw (g)
4
5
4
4
4
3
9
6
8
7
Mass of cup (g)
11
11
11
12
12
12
12
11
11
11
Mass of dry soil, Ms (g)
28
37
23
30
19
21
33
30
30
30
Water content, w (%)
14.29
13.33
21.05
14.29
27.27
13.51 17.39
20.00 26.67
23.33
Unit weight determination
Water Content , w(%) average
Mass of soil + mold (kg)
Mass of mold (kg)
Mass of soil in mold (kg)
Mass of soil in mold (lb)
Wet unit weight (lb/ft3)
Dry unit weight (lb/ft3)
13.90
15.36
17.67
23.64
25.00
3.76
3.82
3.945
3.92
3.9
1.989
1.989
1.989
1.989
1.989
1.771
1.831
1.956
1.931
1.911
3.904
4.037
4.312
4.257
4.213
117.130
121.099
129.366
127.712
126.390
102.837
104.972
109.940
103.297
101.112
5
RESULTS
Dry unit weight (lb/ft3)
1.8
111.000
110.000
109.000
108.000
107.000
106.000
105.000
104.000
103.000
102.000
101.000
100.000
0.00
5.00
10.00
15.00
20.00
25.00
30.00
Water Content (%)
Maximum dry unit weight = γdmax. = 110 (lb/ft3)
Optimum Moisture Content = OMC = 18%
Note: The optimum moisture content (OMC) is defined as the moisture level at which the dry
unit weight or dry density are both maximised.
6