# Geotechnical Engineering Questions and Answers – Factors Affecting Permeability

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This set of Geotechnical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Factors Affecting Permeability”.

1. Based on Allen Hazen experiments, permeability can be expressed as ___________
a) K=CD102
b) K=CD210
c) K=DC210
d) K=DC102

Explanation: In 1892, Allen Hazen based on his experiment on filter of sand particles between 0.1 and 3 mm, found that the permeability can be expressed as K=CD102.

2. Which of the following factors affects the permeability of soil?
a) Grain size
b) Properties of pore fluid
c) Void ratio of soils
d) All of the mentioned

Explanation: Grain size, properties of pore fluid, structural soil arrangement of soil particles, entrapped air and foreign matter and adsorbed water.

3. Physical permeability of a soil KP is related to the coefficient of permeability by the equation ___________
a) KP=kɳ
b) KP=kɳ/γW
c) KP=k/ɳ
d) KP=k γW

Explanation: In 1937, Muskat pointed out a relationship between physical permeability and Darcy’s coefficient of permeability as KP=kɳ/γW.
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4. Loudon’s experiments demonstrated the relationship between _____________
a) Permeability and specific surface
b) Permeability and grain size
d) Permeability and volume

Explanation: Loudon’s experiment demonstrated that the permeability of coarse grained soils is inversely proportional to the specific surface at a given porosity.

5. What is the constant value of a and b in Loudon’s empirical formula “log10(KSs2) = a + bn”?
a) 1 and 0
b) 1.515 and 1.365
c) 1.365 and 1.515
d) 0 and 1

Explanation: Based on his experiments, Loudon found out the value of a and b s 1.365 and 1.515 for permeability of 10°c.

6. What is the relationship between permeability and viscosity of water?
a) Directly proportional
b) Inversely proportional
c) Both are equal
d) None of the mentioned

Explanation: From Poiseuille’s law, K=Ds2 γw /ɳ
It is found that permeability is directly proportional to the unit weight of water and inversely proportional to its viscosity.

7. What is the effect of adsorbed water on the permeability of soil?
a) Structural arrangement is varied
b) Reduced degree of saturation
c) Size of the particles is diminished
d) Reduces the pore size

Explanation: The adsorbed water surrounding the fine soil particles is not free to move, and reduces the effective pore space available for the passage of water.

8. What is the approximate value, which can be taken as void ratio occupied by adsorbed water?
a) 1
b) 0
c) 0.1
d) 10

Explanation: According to approximation value after casagrande, 0.1 may be taken as the void ratio occupied by adsorbed water.

9. The effect of structural disturbance is on permeability is more in _____________
a) Fine-grained soil
b) Coarse grained soil
c) Clay soil
d) All of the mentioned

Explanation: The effect of structural disturbance on permeability is much pronounced in fine-grained soil than any other.

10. The structural arrangement of soil Particle vary depending upon ______________
a) Method of deposition and Compacting the soil mass
b) Degree of saturation
c) None of the mentioned
d) All of the mentioned

Explanation: The structural arrangement of the particle may vary, at the same void ratio, depending upon the method of deposition or compacting the soil mass.

11. How do degree of saturation effect permeability of soil?
a) By reducing the pore size
b) By entrapping air in the voids
c) Not allowing soil particles to move freely
d) By changing the void ratio

Explanation: By entrapping the air in the voids present in the soil, the permeability is greatly reduced, thus reducing the degree of saturation.

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