Atterberg Limits( Liquid limit ,Shrinkage limit ,Plastic limit )-Consistency of soils - Civil Engineering

Monday, 2 April 2018

Atterberg Limits( Liquid limit ,Shrinkage limit ,Plastic limit )-Consistency of soils

Consistency of soils

Consistency is a term used to indicate the degree of firmness of soils.The consistency of natural soil is expressed qualitatively by terms such as soft ,stiff, very stiff and hard .Consistency of a soil can be expressed in terms
  1. Atterberg limits of soils 
  2. Unconfined compressive strength of soils.

Atterberg Limits

The consistency of a remoulded sample can be changed by changing its water content.When a saturated soil sample is allowed to dry gradually ,it passes through several stages such as liquid state ,plastic state ,semi-solid state and solid state.

Atterberg limits or consistency limits are the arbitrary limits of water content at which the soil mass passes from one state to another state.
The atterberg limits which are most useful for engineering purpose are liquid limit,plastic limit and shrinkage limits .

1) Liquid limit

Liquid limit is defined as the minimum water content at which the soil is still in the liquid state ,but has a small shearing strength against flowing.It is determined by a stander apparatus known Casagrande.

2) Plastic limit

Plastic limit is defined as the minimum water content at which a soil will just begin to crumble when rolled into a thread approximately 3 mm in diameter .

3) Shrinkage limit

Shrinkage limit is defined as the maximum water content at which a reduction in water content will not cause a decrease in the volume of a soil mass.

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