Correct Answer - Option 1 : silt (M)
Concepts:
The soils which passes through 0.075 sieves are called fine grained soils. They have very fine texture and small size particles which is difficult to identify them visually. Therefore, fine grained soils are indentified using dilatancy test. They are two types: silt and Clay.
In dilatancy test, wet soil sample is kept in palm and observe the movement of water during shaking, squeezing (by closing hand) and following criteria is used generally for classify the fine grained soil:
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Soil Type
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Observation during Dilatancy test
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Clay
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Water slowly appears and remains on the surface during shaking or water slowly disappears upon squeezing.
It shows some plasticity when water is added in it i.e. it sticks on palm. When we increase the moisture in clay, quantity of clay attached on palm increases i.e. increases the plasticity on adding the water.
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Silt
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Water quickly appears on the surface during shaking and quickly disappears upon squeezing.
It shows very less plasticity regardless of the water is added i.e. on increasing the amount of water in silt, less particles stick to palm.
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In the Indian Standard Soil Classification System (ISSCS), soils are classified into groups according to size, and the groups are further divided into coarse, medium and fine sub-groups.
The grain-size range is used as the basis for grouping soil particles into boulder, cobble, gravel, sand, silt or clay.
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Classification
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Type
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Sub Category
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Size
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Very coarse soils
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Boulder
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> 300 mm
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Cobble
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80 - 300 mm
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Coarse soils
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Gravel (G)
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Coarse
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20 - 80 mm
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Fine
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4.75 - 20 mm
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Sand (S)
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Coarse
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2 - 4.75 mm
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Medium
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0.425 - 2 mm
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Fine
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0.075 - 0.425 mm
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Fine soils
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Silt (M)
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0.002 - 0.075 mm
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Clay (C)
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< 0.002 mm
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Gravel, sand, silt, and clay are represented by group symbols G, S, M, and C respectively.
