Question

Soil consistency depends upon physical forces of

• A. Cohesion
• B. Adhesion
• C. Cohesion and adhesion
• D. Capillary force

Hint:

The Atterberg limits (liquid limit, plastic limit) are used to quantify soil consistency, which is determined by cohesive and adhesive forces.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Soil consistency refers to the physical behavior of soil under stress and its resistance to deformation or rupture.
It is a dynamic property that varies with soil moisture content, describing states such as hard, friable, plastic, or sticky.
Detailed Explanation:
The physical behavior of soil under mechanical stress is determined by two primary molecular forces:
- Cohesion: The electromagnetic attraction between similar soil particles (such as clay-to-clay bonding). Cohesion holds the soil particles together, providing shear strength and resistance to rupture, especially in dry or slightly moist soils.
- Adhesion: The attraction between dissimilar materials, specifically between the surfaces of soil mineral particles and water molecules. Adhesion allows water to wet and stick to soil surfaces, influencing the plasticity and stickiness of wet soils.
As moisture content changes, the relative balance between cohesive forces (between particles) and adhesive forces (between soil and water) shifts, altering soil consistency from solid to plastic and liquid states.
Therefore, soil consistency depends on both cohesion and adhesion.

Step 2: Final Answer:
Soil consistency depends on the physical forces of cohesion and adhesion, corresponding to Option (C).