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Field identification of soils

Methods for field identification of soils: Visual examination, Dilatancy, Toughness, Dry Strength, Organic content and Shine test.

Field identification of soils

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Methods for field identification of soil

• Visual examination
• Dilatancy
• Toughness
• Dry Strength
• Organic content
• Shine test.

Visual examination and Dilatancy

• Bigger the particles: Coarse grained
• Smaller the particles: Fine grained

Dilatancy is based on the water movement in the soil sample. Take a slightly wet soil, squeeze it in the hand

• If water disappears immediately silt
• If it takes some time for the water to disappear or if water doesn't go back then it is clay


Same sample of dilatancy test is used and dry it for a while. Try to roll it into 3mm thread then find the plastic limit.

Now after reaching to the plastic limit, try to roll it by using some extra pressure then if it can roll further , it implies the soil has more toughness.

• If we cant able to roll it or it crumbles then it indicates the low toughness
• If the thread starts to crumble below the plastic limit itself then it indicates the medium toughness.

Organic material gives a sponge feel when touched in the hand

Field identification of soils

Dry Strength

Same sample would be dried until it loses its water completely and then apply the pressure by fingers, then if it converts into powder then it implies it has low dry strength.

• If it requires strength from fingers it implies it has medium dry strength
• If it can’t be powdered with the application of strength also, it implies it has high dry strength

Shine Test

Take soil sample and cut with the knife
• If it looks shiny, then it is plastic clay

• If it has dull surface, then it is low plastic clay

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