Question

What is Coarse soil and what are its classifications?

Answer 1

Coarse soils are the soil in which 50% or more by weight of the soil particles retained on no. 200 ASTM sieve or 0.0075 mm seive .

Or the 50% or more soil particles have size greater than 0.0075 mm.

The classification of coarse grained soils are as -

Sand and Gravel .

And further well graded sand , poor graded sand , well graded gravel or poor graded gravel.

If 50% of coarse fraction particles passes through No. 4 ASTM sieve then it ais called as sand .

And if more than 50% of coarse fraction retained on No. 4 ASTM sieve it is called as gravel .

And further , if coefficient of uniformity = ( D60/D10) is greater than 6 and coefficient of curvature ( D30/D60 D10) is between 1 to 3 then it is well graded sand .

Otherwise , poor graded sand .

And if Coefficient of uniformity is greater than 4 and coefficient of curvature is between 1 and 3 , it is well graded gravel .

Else poor graded gravel.

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