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, 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 experiment
b) Completed data sheets 1-3.
c) Give 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.