As per Indian standard soil classification, identify the soil type with the following details.

Fine grained soil that more than 65% passing through 75 microns IS sieve; has liquid limit less than 35%; Atterberg limits plot below A - line.

Concept:

It is adopted by IS code. It was given by A-line Casagrande.

It uses particle size distribution for coarse soils and plasticity for fine soils.

Equation of A-line \(I_P=0.73(W_L-20)\)

where, 

W_L = Liquid Limit

P_L = Plastic Limit

I_P = Plasticity Index

Calculation:

Given:

Liquid Limit = WL < 35%

Atterberg limits plot below A - line.

Fine-grained soil with more than 65% passing through 75 microns IS sieve;

It is clear that soil is fine-grained i.e. Clay, Silt

From the above chart

If the soil is above A-line, it is clay

If the soil is below A-line, it is silt

As the soil is below A-line it is silt

and the Liquid Limit of soil = W_L < 35%

So the group symbol of the silt fraction is ML