SOIL CLASSIFICATION

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SOIL CLASSIFICATION
-Ms Ikmalzatul
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TWO KINDS of Soil...

• Two kinds of soil in this world
• COARSE
• FINE

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Fine-Grained vs. Coarse-Grained Soils

• U.S. Standard Sieve - No. 200
• 0.0029 inches
• 0.074 mm

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Sieve Analysis (Mechanical Analysis)

• This procedure is suitable for coarse grained
  soils
• e.g. No.10 sieve . has 10 apertures per linear
  inch

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Hydrometer Analysis

• Also called Sedimentation Analysis
• Stokes Law

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Grain Size Distribution Curves
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Soil Plasticity

• Plasticity is a property that enables a soil to
  undergo deformation without breaking.
• Clays for instance are moulded into earthen pots
  when its plastic state.
• This property is characteristic on fined grained
  soils only, in the presence of water.
• When water is replaced by some other liquid , say
  kerosene, the clay will behave as a granular
  mass.

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• Plasticity is due to clay minerals in the soils
  and is exhibited only over a specific range of
  moisture content.
• Excessive water turns the soil into a suspension
  (liquid state).
• With gradual decrease in the water content, the
  soil passes into a plastic state, then into a
  semi-solid (or semi-plastic) state and finally
  into a solid state.

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Plastic state
Semi-solid state
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• The water content at which these changes of state
  occur called limits or indices.
• Albert Atterberg, Swedish Soil Scientist
  (1846-1916)..series of tests for evaluating soil
  plasticity. He defined these limits as follows
  the liquid limit (LL) is the water content at
  which a soil passes from liquid to plastic state
  the plastic limit (PL) is the water content at
  which a soil passes from plastic to semi-solid
  state and the shrinkage limit (SL) is the water
  content at which a soil passes from semi solid
  state.

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• Further classification within fine-grained soils
  (i.e. soil that passes 200 sieve) is done based
  on soil plasticity.
• Arthur Casagrande adopted these tests for
  geotechnical engineering purposes

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Atterberg Limits

• Consistency of fine-grained soil varies in
  proportion to the water content

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Liquid Limit (LL or wL)

• Empirical Definition
• The moisture content at which a 2 mm-wide groove
  in a soil pat will close for a distance of 0.5 in
  when dropped 25 times in a standard brass cup
  falling 1 cm each time at a rate of 2 drops/sec
  in a standard liquid limit device

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Engineering Characterization of Soils
Soil Properties that Control its Engineering
Behavior
Particle Size
fine-grained
coarse-grained

• Soil Plasticity

• Particle/Grain Size Distribution
• Particle Shape

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Clay Morphology

• Scanning Electron Microscope (SEM)
• Shows that clay particles consist of stacks of
  plate-like layers

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Soil Consistency Limits

• Albert Atterberg (1846-1916) Swedish Soil
  Scientist
• .. Developed series of tests for evaluating
  consistency limits of soil (1911)
• Arthur Casagrande (1902-1981)
• Adopted these tests for geotechnical
  engineering purposes

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Arthur Casagrande (1902-1981)

• Joined Karl Terzaghi at MIT in 1926 as his
  graduate student
• Research project funded by Bureau of Public Roads
• After completion of Ph.D at MIT Casagrande
  initiated Geotechnical Engineering Program at
  Harvard
• Soil Plasticity and Soil Classification (1932)

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Casagrande Apparatus
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Casagrande Apparatus
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Casagrande Apparatus
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Liquid Limit Determination
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Plastic Limit (PL, wP)

• The moisture content at which a thread of soil
  just begins to crack and crumble when rolled to a
  diameter of 1/8 inches

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Plastic Limit (PL, wP)
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Plasticity Index ( PI, IP )

• PI LL PL
• or IPwL-wP
• Note These are water contents, but the
  percentage sign is not typically shown.

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Plasticity Chart
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USCS Classification Chart
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USCS Classification Chart
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Plasticity Chart
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THE END