Permeability MCQ with answer and solution

Concept

Constant Head Permeability Test

Formula

k = (Q × L) / (A × h × t)

Step-by-step solution

1. Identify that the constant head permeability test is suitable for coarse-grained soils with high permeability. 2. Evaluate the given options: SP (poorly graded sand) is a coarse-grained soil, whereas CH and CL are fine-grained clays. 3. Select Option D (SP) as the correct answer.

Explanation

The constant head permeability test is best suited for coarse-grained soils with high permeability, such as poorly graded sand (SP). Because water flows through sandy soils quickly and easily, a measurable volume of water discharge can be collected in a short time while keeping the water pressure (head) constant. Fine-grained soils like clays (CH, CL) have very low permeability, making this test impractical for them.

Shortcut

Remember: "Constant = Coarse" (Constant head test is for Coarse-grained/sandy soils like SP, while Falling head test is for Fine-grained soils like clays/CH/CL).

Common mistake

Many students confuse the constant head test with the falling head test and incorrectly select fine-grained soils like clay (CH or CL) instead of coarse-grained soils (SP).