Permeability MCQ with answer and solution

Concept

Permeability depends on the size of pores, not on the void ratio alone

Formula

k ∝ D10² (Hazen)

Step-by-step solution

1. Both soils have the same void ratio and specific gravity, so porosity and density are the same. 2. Clay has very small pores and sand has large pores. 3. Permeability varies with the square of the pore size, so it is very different.

Explanation

Permeability depends mainly on the size of the pores (particle size), their shape and connectivity. Soils with the same void ratio can have very different permeabilities when their pore sizes differ.

Shortcut

Same e, different grain size → different k.

Common mistake

Thinking that void ratio alone decides permeability.