Pavement Design MCQ with answer and solution

Concept

Drainage Layer in Flexible Pavement

Formula

No formula

Step-by-step solution

- Recall the function of each layer in a flexible pavement structure. - The subbase layer uses porous granular materials to facilitate drainage and protect the subgrade. - Therefore, Option A (Subbase layer) is correct.

Explanation

The subbase layer in flexible pavement is designed using porous, coarse granular materials that allow water entering the pavement structure to drain away quickly. This prevents water accumulation above the subgrade, preserving the structural integrity and strength of the road foundation.

Shortcut

Remember "Subbase = Sub-surface Water / Water Base": The Subbase is at the bottom of the pavement structure (closest to the subgrade) and acts as the drainage layer to drain away water before it weakens the subgrade.

Common mistake

Many students confuse the Base layer with the Subbase layer, incorrectly selecting Option B because they assume the main load-bearing base layer also serves as the primary drainage layer.