Which of the following statement(s) is/are true? (i) Below the shrinkage limit, the volume remains constant even as water content decreases further. (ii) Fine-grained, cohesive soils (like clays) have lesser shrinkage potential compared to coarse-grained soils.
- AOnly (i)Correct
- BOnly (ii)
- CBoth (i) and (ii)
- DNeither (i) nor (ii)
Solution
Concept
Shrinkage limit definition and soil shrinkage behavior
Formula
SL = (w - [(V - Vd) × ρw / ms]) × 100
Step-by-step solution
1. Statement (i) is correct: The shrinkage limit is the boundary water content below which soil ceases to shrink and volume remains constant. 2. Statement (ii) is incorrect: Fine-grained cohesive clays contain active clay minerals (montmorillonite, illite) with very large specific surface areas, resulting in substantial shrinkage and swelling potential compared to coarse-grained soils. 3. Coarse-grained sands and gravels undergo negligible volumetric shrinkage upon drying. 4. Thus, only statement (i) is true. Answer: A
Explanation
The shrinkage limit is defined as the maximum moisture content at which further reduction in water content causes no further reduction in the total volume of the soil mass; hence statement (i) is true. Fine-grained cohesive clays exhibit significantly higher shrinkage potential than coarse-grained soils, making statement (ii) false.
Why the other options are wrong
B) Incorrect because statement (ii) is false. C) Incorrect because statement (ii) contradicts soil physics. D) Incorrect because statement (i) is the exact fundamental definition of shrinkage limit.
Shortcut
Below Shrinkage Limit: Volume is constant. Clays have higher shrinkage potential than sands.
Common mistake
Believing coarse soils shrink more than cohesive fine-grained clays.
Correct answer: A) Only (i)