Question

Consider the following statements:
1. Coarse sand is more than a million times permeable than a high plasticity clay.
2. The permeability depends on the nature of soil and not on properties of liquid flowing through soil.
3. If a sample of sand and a sample of clay have the same void ratio, both samples will exhibit the same permeability.
4. Permeability of soil decreases as the effective stress acting on the soil increases.
Which of these statements are correct?

• A. 1 and 2
• B. 1 and 3
• C. 1 and 4
• D. 2 and 3

Answer 1

The correct option is C 1 and 4

c)
Coarse sand is more than million times permeable than a high plasticity clay.
$k=C{D}_s^2\frac{e^3}{(1+e)}\frac{\gamma }{\mu }$
Permeability depends upon
(i) Grain size
(ii) Properties of pore fluid
(iii) Void ratio of soil
(iv) Structural arrangement of the soil particles
(v) Entrapped air and foreign matter
(vi) Adsorbed water in clayey soils.
It means that a sample of sand and clay having same void ratio may not have same permeability due to structural arrangement of particles and adsorbed water.
Increase in effective stress causes compression of soil and rearrangement of particles. So permeability decrease.