Which of the following factors does NOT affect the permeability of soil? (i) Total volume of the soil mass (ii) Particle size (iii) Void ratio (iv) Degree of saturation
- AOnly (i)Correct
- B(i) and (ii)
- C(iii) and (iv)
- D(ii) and (iv)
Solution
Concept
Factors governing soil hydraulic conductivity and permeability
Formula
k = C × D102 × (e3 / (1 + e)) × (γw / μ)
Step-by-step solution
1. Hydraulic conductivity (permeability k) is an intensive material property of a soil-fluid system. 2. By Hazen's and Kozeny-Carman formulas, k depends on particle size (D102), void ratio (e3/(1+e)), degree of saturation, fluid unit weight, and viscosity. 3. Permeability is independent of the total bulk volume or macroscopic dimensions of the soil mass. 4. Therefore, factor (i) does not affect soil permeability. Answer: A
Explanation
The coefficient of permeability (hydraulic conductivity) of soil depends on soil particle size (k proportional to D102), void ratio, degree of saturation, permeant viscosity, and soil fabric. Because permeability is an intensive engineering material property, it does not depend on the total volume of the soil mass.
Why the other options are wrong
B) Particle size (factor ii) strongly governs pore throat diameter and permeability (k proportional to D102). C) Void ratio and saturation (factors iii and iv) heavily control flow channels. D) Both factors (ii) and (iv) directly alter permeability.
Shortcut
Permeability = Material property; independent of total soil mass volume.
Common mistake
Believing void ratio or particle size does not govern permeability.
Correct answer: A) Only (i)