Explain Indian Standard Soil classification system.

Indian Standard classification system adopted by Bureau of Indian Standards is in many respect similar to the USCS. However, there is one basic difference in the classification of fine grained soils .The fine grained soils in ISSCS are subdivided into three categories of  low, medium and high compressibility instead of two categories of low and high compressibility in USCS.

ISSCS classify the soil into 18 group.

Coarse grained soils are subdivided into gravel and sand. The soil is termed  gravel(G) when more than 50% of course fraction is retained on 4.75 mm IS seive and termed sand (S)  if more than 50% of the coarse fraction is smaller than 4.75 mm IS seive. Course graines soils are further subdivided into 8 groups .

The fine grained soil are further divided into three sub divisions, depending upon the values of liquid limit.

Silts and Clay of low compressibility:

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Indian Standard classification system adopted by Bureau of Indian Standards is in many respect similar to the USCS. However, there is one basic difference in the classification of fine grained soils .The fine grained soils in ISSCS are subdivided into three categories of  low, medium and high compressibility instead of two categories of low and high compressibility in USCS.

ISSCS classify the soil into 18 group.

Coarse grained soils:

Coarse grained soils are subdivided into gravel and sand. The soil is termed  gravel(G) when more than 50% of course fraction is retained on 4.75 mm IS seive and termed sand (S)  if more than 50% of the coarse fraction is smaller than 4.75 mm IS seive. Course graines soils are further subdivided into 8 groups .

Fine grained soils:

The fine grained soil are further divided into three sub divisions, depending upon the values of liquid limit.

Silts and Clay of low compressibility:

These soils have a liquid limit less than 35 (represented by the symbol L).

Silts and Clay of medium compressibility:

These soils have a liquid limit greater than 35 but less than 50 (represented by symbol I).

Silt and Clay of high compressibility

These Soils have a liquid limit greater than 50 (represented by the symbol H).