Plasticity Index (PI) is defined as:
Choose the correct answer
PI = SL − PL (Shrinkage Limit − Plastic Limit)
PI = LL − PL (Liquid Limit − Plastic Limit)
PI = LL − SL
PI = LL/PL
Correct Answer
B. PI = LL − PL (Liquid Limit − Plastic Limit)
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PI = LL − PL (Liquid Limit minus Plastic Limit). PI represents the range of water content over which soil is plastic. High PI → highly plastic clay (e.g., montmorillonite PI > 200). Low PI → silt or sandy soil. Liquidity Index LI = (w − PL)/PI indicates current state relative to Atterberg limits.
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