2. PLASTICITY OF SOIL

Plasticity of soil :-

• Plasticity of soil is its ability to undergo deformation without Cracking on Fracturing.

Engineering Properties :-

• The main engineering properties of soil are

• Permeability :- Indicates facility with which water can flow through soils.

• Compressaibility :- Related to the deformation procedure in soil (C.L)
• Shear Strength :- Shear strength of soils is its ability to resist shars stress.

Determines:- 1.Stability of slope 2.Bearing capacity of soil. 3.Earth pressure on returning soils.

Index Properties

1. The test required for determination of engineering properties are generally elaborate and time consuming.
2. Sometimes Geotechnical engineer is interested into the rough assesment of engg properties without considering / conducting elaborate tests.

3. The properties of soils which are not of primary interest to the geotechnical engineer but which are indicative of the engg properties are called as index properties.

   A) Main index properties a) Eco grained soil - Relative density partical size b) Fine grained soil - Atterberg limits & consistency Atterberg Limits :- The Atterberg limits are a basic measure of the critical water content of the fine grained soils. Its shrinkage limit, plastic limit,and liquid limit. Plasticity of soils:-

4. a plastic soils can be moulded into various shapes when its wet.
5. Plasticity isan important index properties of fine grained soils especially clay.
6. Plasticity is due to presence of clay.

Consistency Limits:- - Consistency of soils means degree of backbone firmness of soil. - In 1991, a swedish agriculture engineer Atterberg mentioned that fine grained soil can be exist in four states.

Namely - Liquid ,Plastic, Semi-solid,and Solid state. - The water content or moisture content at which the soils charges from one state to another are known as consistency limit or Atterberg limit.

• Liquid limit:
• The water content at which the soils changes from liquid state to plastic state. OR LImit is water content at which soil.

• Liquid Limits-->Determine (A)Casagrande's apparatus (B)Cone peniration test

  • The liquid limit of soils depend upon class mineral presents.Cone Periration

has several advantages:- A. It is easier to perform. B.The method is applicable for wide range of soils. C. The results are reliable and de not depend upon the judgement of the operator.

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