Question

28. Atterberg limits of a soil represent which of the following property at critical stages of soil behaviour

• A. Soil moisture
• B. Soil texture
• C. Soil structure
• D. Soil cohesion

Hint:

All Atterberg limits are expressed as water contents (percentages).
Liquid limit, Plastic limit, and Shrinkage limit separate the liquid, plastic, semi-solid, and solid states of cohesive soils, respectively.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept:
Atterberg limits (consistency limits) are a fundamental set of index properties established by Albert Atterberg for fine-grained soils.
Consistency refers to the relative ease with which a soil can be deformed or ruptured, which is strongly governed by the amount of water present in the soil.
As a clayey soil is mixed with varying amounts of water, it transitions through four distinct states: solid, semi-solid, plastic, and liquid.

Step 2: Detailed Explanation:
The Atterberg limits define the specific boundaries between these consistency states, and each limit is defined and measured directly as a water content (soil moisture percentage):
1. Liquid Limit (\(w_L\)): The boundary water content at which the soil transitions from a plastic state to a liquid state.
At this moisture level, the soil behaves like a viscous fluid with a negligible shear strength.
2. Plastic Limit (\(w_P\)): The boundary water content at which the soil transitions from a semi-solid state to a plastic state.
At this stage, the soil can be rolled into threads of \(3\text{ mm}\) diameter without crumbling.
3. Shrinkage Limit (\(w_S\)): The boundary water content below which any further reduction in moisture content does not cause any decrease in the bulk volume of the soil mass.
Because each of these limits represents a specific water content (mass of water divided by the mass of dry soil solids), they are fundamentally measurements of soil moisture at critical transition stages of fine-grained soil behavior.

Step 3: Final Answer:
Atterberg limits represent the soil moisture (water content) at critical stages of consistency.