Concept check – identify the single incorrect definition: Which ONE of the following statements is incorrect regarding soil behavior terms?

Introduction / Context:
Precise terminology avoids design errors. Sensitivity, thixotropy, liquid limit, and plastic limit are frequently used in reports and specifications. Misstatements can mislead classification and performance predictions.

Given Data / Assumptions:

• Standard Atterberg limit definitions apply.
• Unconfined compression is the basis for sensitivity ratio.
• Thixotropy pertains to remolded clays at constant water content.

Concept / Approach:
Only one statement is intentionally incorrect. Liquid limit is the water content at the boundary between liquid and plastic states, not directly “liquid to solid.” The plastic limit corresponds to the boundary between plastic and semi-solid states and is practically identified using the 3 mm thread crumbling criterion. Thixotropy describes reversible strength changes over time without water content change.

Step-by-Step Solution:

Verification / Alternative check:
USCS and IS procedures (Casagrande cup or cone penetrometer) define liquid limit as liquid–plastic transition; shrinkage limit defines onset of solid behavior.

Why Other Options Are Wrong:

• Only C conflicts with standard definitions; A, B, and D are consistent with accepted usage.

Common Pitfalls:
Confusing shrinkage limit with liquid limit; overlooking that thixotropy is reversible and isothermal.

Final Answer:
Liquid limit = water content at which a soil changes directly from liquid to solid state