Soil Classification

Soil Mechanics

1. CE6405 Soil Mechanics V.Nageshwaran , M.E., Assistant Professor, Department of Civil Engineering, UCET

2. Soil Classification

3. Indian Standard Soil Classification System Published in 1959 and Revised in 1970. Revision is based on USCS – Fine Grained Soils – Subdivided into 3 Sub-groups of Low, Medium & High Compressibility. (2 in USCS) Lab Classification Criteria for Coarse Grained Soil – Same as in the USCS. Soils are divided into three broad divisions: Coarse Grained Soil – Subdivided into 8 Basic Soil Groups – when 50 % or more of the total material by weight retained on 75 µm IS sieve. Fine Grained Soils – Subdivided into 9 Basic Soil Groups – when more than 50 % of the total material passes 75 µm IS sieve. If the soil is highly organic and contains a large percentage of organic matter and particles of decomposed vegetation, it is kept in a separate category marked as peat (Pt) Totally, 18 groups of soils: Coarse-grained soils – 8 groups Fine-grained soils – 9 groups Peat – 1 group.

4. Particle Size and Group Symbols (ISSCS)

5. Indian Standard Soil Classification System

6. Indian Standard Soil Classification System

7. Cont… According to  gradation , they are further grouped as well-graded ( W ) or poorly graded ( P ). If  fine soils  are present, they are grouped as containing silt fines ( M ) or as containing clay fines ( C ). 'A' line  in this chart is expressed as  I P  = 0.73 (W L  - 20) . Depending on the point in the chart, fine soils are divided into  clays (C) ,  silts (M) , or  organic soils (O) . The organic content is expressed as a percentage of the mass of organic matter in a given mass of soil to the mass of the dry soil solids.

8. GC