SOIL CLASSIFICATION – Soil 1 (Coarse-grained soil)
1.1 Objectives
Students are required to determine the particle size distribution of a coarse-grained soil
(Soil 1) by carrying out a sieve analysis and a sedimentation test (hydrometer analysis).
The results obtain from these tests are then used to classify Soil 1 according to the
Unified Soil Classification System (USCS).
1.2 Particle Size Determination (Soil 1)
The methods for particle size determination depend on the sizes of the particles.
For particles larger than coarse silt size (>0.075 mm) sieving can be used. Soil of a
known mass (approximately 200g) is shaken through a column of sieves with
progressively reducing mesh size. The mass of soil remaining on each sieve is measured.
For smaller particle sizes, the sedimentation method (hydrometer analysis) would be
used. This method makes use of Stoke’s law which relates terminal velocity of spherical
particles falling through a fluid of known viscosity to their diameter. In reality, the soil
grains are not spherical. However, for the purposes of classification the procedure is
sufficiently accurate.
1.2.1 Procedure
1.2.1.1 Sieve analysis
Record results of this test in Datasheet No 1 (attached).
1. Weigh a sample of approximately 200 gm of soil provided.
2. Assemble a series of sieves, with aperture size in descending order: 4.75 mm, 2.36
mm, 1.18 mm, 600 m, 425 m, 300 m, 150 m and 75 m.
3. Sieve the soil sample through the series of sieves, record the mass of soil retained on
each sieve, and the mass passing the finest mesh (i.e. soil retained in the pan).
4. A sedimentation test of the fine material in the pan will be performed following the
procedure described in the Australian Standard (see 1.3.1.2).
1.3.1.2 Sedimentation test
Record results of this test in Datasheet No 3 (attached).
It is important that you should familiarise yourself with the scale on the hydrometer
before commencing the test. Note that there are two types of hydrometer – one measures
the density of the suspension in g/l, and the other measures the density of the
suspension in mg/l. For this experiment, use the hydrometer graduated in g/l. Assume
that the specific gravity of the soil particles, Gs = 2.65.
1. Fill the cylinder with distilled water until about ¾ full. Place the hydrometer in the
cylinder and record the meniscus correction reading Cm. Also record the temperature
of the water.
2. Add about 20g (M0) of the fine-grained soil retained in the pan into the milk shake
container and fill with distilled water until about ¾ full. Shake the mixture in a milk
shaker for about 2 minutes.
3. Pour the suspension into the 1000 ml cylinder. Wash any fines that remain in the
container into the cylinder with distilled water. Add more distilled water into the
cylinder to make up to 1000 ml.
4. Place a stopper over top of cylinder and turn upside down about 5 times
5. Place cylinder on table and commence timing.
Take hydrometer readings at:
30 secs
1 min
2 mins
4 mins
Take hydrometer out after 4 minutes and wash with distilled water
Take last reading at 8 minutes.
1.6 Reporting of Results
1. Complete the results of testing in Datasheets 1, 2 and 3.
2. The results of the particle size determination (from both the sieve analysis and
sedimentation test) should be presented on the semi-logarithmic plot (Datasheet No
2) provided showing the percentage passing against mesh aperture.
3. Students MUST complete Tasks 1 and 2 above and present them to the
demonstrator before leaving the lab class.
4. A type written report is to be submitted within one week of the practical class. The
report should be concise and include the following:
a) Objectives of experiments;
b) Completed datasheets 1-3;
c) Present the classification of Soil 1 according to the USCS. Include the appropriate
symbols for the group;
d) A short summary of the soil properties and of how good is Soil 1 as a fill material.
1.6 Performance Criteria and Assessment Standards
The following criteria will be used in assessing the submitted lab report:
(1) Active participation and completion of the required lab tasks during the lab class. It
will include punctuality, dress code and compliance with OH&S requirements.
[15%]
(2) Adequate elaboration of objectives of the experiment, and accurate, concise
description of experimental procedures.
[10%]
(3) Clear and concise reporting and presentation of experimental results (including
clarity, neatness and correctness). Keep in mind that this is to be a type-written report
although the recorded raw data can be hand-written. I expect to see the use of MS
Excel spreadsheet and the equation editor in MS Word in preparing the report, if
this is required.
[30%]
(4) Addressing the objectives of the experiment adequately. If there were unexpected
errors in the experimental results, clear and rational explanations should be provided.
[30%]
(5) Addressing questions in the handout and conclusions of the experiments adequately.
[15%]
Soil Mechanics Laboratory Test
DATASHEET NO.1 – SIEVE ANALYSIS
1.
Particle-size Analysis (Sieving)
Sieve Analysis
Wet/dry
Original mass of sample =
AS sieve
size, mm
weight, g
(1)
g
sieve + sample
Mass Retained
Cumulative
% Cumulative
% Mass
g
(2)
g
(2)-(1)
Mass Retained, g
Mass Retained
Passing
4.750
2.360
1.180
0.600
0.425
0.300
0.150
0.075
Pan
Tester:
Date:
Time:
Soil Mechanics Laboratory Test
DATASHEET NO.2 – SIEVE ANALYSIS PLOT
200
100
75
63
37.5
26.5
13.2
19
9.5
10
4.75
6.7
2.36
1 1.18
0.425
0.6
0.3
0.212
0.1
0.01
100
0.15
0.075
AUSTRALIA STANDARD SIEVE APERTURES
0.001
0.0001
SIEVE ANALYSIS
90
80
percentage passing
70
60
50
40
30
20
10
0
SILT FRACTION
CLAY FRACTION
FINE
0.0001
0.002
MEDIUM
0.006
SAND FRACTION
COARSE
0.02
FINE
0.06
GRAVEL FRACTION
COARSE
MEDIUM
0.6
0.2
MEDIUM
FINE
2
6
Particle size, mm
Tester:
Date:
Time:
COBBLES
COARSE
20
60
200
Soil Mechanics Laboratory Test
DATASHEET NO.3 – PARTICLE SIZE DISTRIBUTION – HYDROMETER TEST
Tester:
Date:
Sample description:
Mass in suspension M0 (g)
Specific unit weight Gs
Dispersing agent correction Ca
Meniscus correction Cm
Time:
=
=
=
=
Time
(min)
Hydrometer
reading
(g/l)
Meniscus
corrected
Hydrometer
reading
(g/l)
Temp
Corrected
Hydrometer
Reading
t
0.5
Rh
R h
(C)
Rc
F1
F2
F3
Particle
size
% finer
by mass
% finer
by total
mass
D (m)
p
K
1
2
4
8
15
30
60
240
300
Rh= Rh + Cm where Rh is the hydrometer reading
Rc = Rh + Ct - Ca where temperature correction may be done using chart
Factor F1 relates to distance of falling particles (see chart)
Factor F2 relates to viscosity of fluid, soil density, fluid density (see table)
Factor F3 relates to time (see table)
D  F1  F2  F3 (m)
Gs
0.623
Rc
 100 (%)
M0
Gs  1
mass of soil remaining in pan
K  p
total mass of soil used in sieving analysis
p
Soil Mechanics Laboratory Test
DATA SHEET NO 4 – HYDROMETER CHARTS
Grams Per Liter Hydrometer Calibration
4.4
4.2
Rh1
4.0
Rh2
Factor F1
3.8
3.6
3.4
3.2
3.0
2.8
2.6
0
10
20
30
40
50
60
Hydrometer reading (g/l)
Specific Gravity Hydrometer Calibration
4.4
4.2
Rh1
Rh2
4.0
Factor F1
3.8
3.6
3.4
3.2
3.0
2.8
1000
1010
1020
Hydrometer
reading mg/l
Hydrometer
reading
1030
Soil Mechanics Laboratory Test
F3  10
t
t in mins
Temperature correction
Soil Mechanics Laboratory Test
Is soil sample obviously highly organic with odour, leaves,
twigs etc?
Classify as Pt
(Peat)
Yes
No
A sieve test is made on the entire sample and the percentage
passing the No. 200 (75 m) sieve is noted – P200
No
P200 > 50%
Coarse grained
soil
Yes
P4 Percentage passing the No. 4
(4.75 mm) sieve – P4 > 50%
Fine grained soil
No
Yes
LL > 50%
Sandy soils
SW, SP, SM or
SC
CL, ML or OL
depending on
PI = LL-PL and
LL
CH, MH or OH
depending on
PI = LL-PL and
LL
Gravelly soils
GW, GP, GM or
GC
P200 < 5%
No
Yes
Cu > 4 for gravels?
P200 > 12%
Cu > 6 for sands?
1 < Cc < 3 for both?
CH
GW
or
SW
Yes
No
Yes
GP
or
SP
No
Borderline
Dual
Symbols
Below A-line or
PI < 4%
No
Yes
Above A-line
or PI > 7%
GM or
SM
Yes
GC or
SC
No
Borderline
Dual
Symbols