Difficulty: Easy
Correct Answer: All the above
Explanation:
Introduction / Context:
Atterberg limits and derived indices describe the consistency and plasticity of cohesive soils. These parameters are widely used for classification, correlation with engineering properties, and specification compliance in earthworks and foundations.
Given Data / Assumptions:
Concept / Approach:
Definitions:
Plasticity index (PI) = LL − PL.Consistency index (Ic) = (LL − w) / PI.Liquidity index (LI) = (w − PL) / PI.Toughness index (It) = PI / If.These indices help compare soils with different Atterberg limits and evaluate field consistency relative to the plastic range.
Step-by-Step Solution:
Verification / Alternative check:
Worked examples with typical values (e.g., LL = 60, PL = 25, w = 35) confirm the indices and their ranges.
Why Other Options Are Wrong:
Each of A–D correctly states standard definitions; therefore the combined correct answer is “All the above”.
Common Pitfalls:
Using percentages without consistent units; confusing consistency index with liquidity index; misreading the flow curve slope units when computing It.
Final Answer:
All the above
Discussion & Comments