# Geotechnical Engineering Questions and Answers – Determination of Coefficient of Permeability

This set of Basic Geotechnical Engineering Questions and Answers focuses on “Determination of Coefficient of Permeability”.

1. Permeability can be determined by direct measurement with the help of ___________
a) Permeameter
b) Consolidation test
c) Horizontal capillary test
d) Pumping-out test

Explanation: Permeability of soil can be determined by permeameters, by allowing the water to flow through soil sample under either constant head or under variable head.

2. Which of the following formula, cannot be used for determining the permeability of soil?
a) Jacky’s formula
b) Allen Hazen’s formula
c) Kozney’s formula
d) Darcy’s formula

Explanation: In Darcy’s equation or Darcy’s law, there is no permeability constant.
q = k i A
Hence it cannot be used for finding permeability of soil.

3. Coefficient of permeability of soil can be determined by which of the following method?
a) Laboratory methods
b) Field methods
c) Indirect methods
d) All of the mentioned

Explanation: The coefficient of permeability can be determined by the following methods:
i. Laboratory method – constant head permeability and falling head permeability test
ii. Field method –pumping-out and pumping-in test
iii. Indirect methods- horizontal capillary test and consolidation test data.

4. Allen Hazen’s formula is given by which of the following equations?
a) K = 100m2
b) K = C D102
c) K = 200De2e2
d) None of the mentioned

Explanation: Allen Hazen’s formula is K=CD102, where c is constant, which is taken as approximately equal to 100 when D10 is expressed in cm.

5. The unit of coefficient of absolute permeability(K) is ____________
a) Kg/cm
b) m/s2
c) m2
d) All of the mentioned

Explanation: Since K has the dimension of area (i.e. [k] = [L2]), the unit of K is m2.
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6. Coefficient of absolute permeability (K) depends on ____________
a) Permeant
b) Properties of soil mass
c) Degree of saturation
d) All of the mentioned

Explanation: From the equation of coefficient of absolute permeability,
K = C (e3/1+e) D3
We can find that coefficient of permeability is independent of the properties of permeant (i.e. water) and it depends solely on the properties of soil mass.

7. In Terzaghi’s formula K = 200De2e2, De2 represents ____________
a) Effective grain shape
b) Void ratio
c) Effective grain size
d) Permeability

Explanation: De=effective grain size, the diameter of the sphere for which the ratio of its volume to its surface area is the same as the similar ratio for a given assemblage of soil particles.

8. K = 100Dm2, is given by which of the following formula?
a) Terzaghi’s formula
b) Kozney’s formula
c) Jacky’s formula
d) Allen Hazen’s formula

Explanation: In 1944, Jacky found out the order of magnitude of k can be obtained from all soils from the formula K= 100Dm2, where Dm denotes grain size.

9. Terzhagi’s formula can be applied for_________
a) Uniform sand
b) Clay soil
c) Coarse-grained soil
d) Fine-grained soil

Explanation: Terzaghi’s formula can be successfully applied to fairly uniform sand, which reflects the effect of grain size and void ratio.

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