# Geotechnical Engineering Questions and Answers – Constant and Falling Head Permeability Test

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This set of Geotechnical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Constant and Falling Head Permeability Test”.

1. Falling head permeability test can be used for ___________
a) Coarse-grained soil
b) Less permeable soil
c) Clayey soil
d) All of the mentioned

Explanation: Falling head test is used for relatively less permeable soils where the discharge is small.

2. Which of the following formula is used in Falling head permeability test?
a) Jacky’s formula
b) Louden’s formula
c) Darcy’s law
d) Kozney’s formula

Explanation: In falling head permeability test, Darcy’s law is used from which the rate of flow q, can be used
q = K i A.

3. In falling head permeability test apparatus, the water head at any time instant is equal to ____________
a) Difference in the water level
b) Cross-sectional area of pipe
c) Height of permeameter
d) None of the mentioned

Explanation: The head h1 and h2 at any time instant t is equal to the difference in the water level in the stand pipe and the bottom tank.
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4. In constant permeability test, the length of specimen is measured by ___________
a) Calculating the difference in water level
b) Using Piezometric tube
c) Using measuring scale
d) None of the mentioned

Explanation: In a constant head test, the length of the sample is measured by inserting piezometric tubes on top and bottom.

5. The constant head permeability test is used for ___________
a) Fine-grained soil
b) Coarse-grained soil
c) Clay soil
d) Saturated soil

Explanation: Coarse-grained soil, for which a reasonable discharge can be collected in a given time, is used in constant test.

6. The laboratory observation falling head test consist of measurements of ____________
a) h1 at an interval of t1 and h2 at an interval of t2
b) Only t1 and t2
c) None of the mentioned
d) All of the mentioned

Explanation: The laboratory measurement of falling head permeability test consists of measurement of the heads h1 and h2 at two chosen time intervals t1 and t2.

7. Which of the following tubes are used in the constant head test?
a) Inlet tube
b) Overflow tube
c) Outlet tube
d) All of the mentioned

Explanation: The constant head test apparatus consists of three tubes: the inlet tube, the overflow tube and outlet tube.

8. In falling head permeability test, change in the head at a time interval dt is denoted as ___________
a) dh
b) –dh
c) h
d) –h

Explanation: -dh is used to denote a change in a smaller time interval dt, the minus sign has been used since h decreases as t increases.

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