Geotechnical Engineering Questions and Answers – Capillary Tension, Capillary Potential and Soil Suction

Geotechnical Engineering Objective Questions

This set of Geotechnical Engineering Questions and Answers for Freshers focuses on “Capillary Tension, capillary Potential and Soil Suction”.

1. The capillary tension or capillary potential can also be called as ___________

A) Pressure deficiency
B) Pressure reduction
C) Negative pressure
D) All of the mentioned

Answer is D)
Explanation: The capillary potential is the pressure deficiency, pressure reduction or negative pressure in the pore water.

2. The maximum tensile stress of water in capillary tube is ___________

A) Proportional to the diameter of tube
B) Inversely proportional to height of capillary rise
C) Inversely proportional to the radius of meniscus
D) All of the mentioned

Answer is C)
Explanation: From the formula, (UC) max = 2Ts /R Where, (UC) max = maximum tensile stress R = radius of meniscus TS = surface tension.

3. The pF value of 2 in soil mass represent ____________

A) Soil suction of 200 cm of water
B) Suction pressure of 100 g/cm^2
C) Soil suction of 100 cm of water
D) Capillarity of 100 g/cm^2

Answer is C)
Explanation: From the relationship, pF=log10 (hc) 2 = log10 (hc) hc = 2/log10 hc = 100 cm.

4. The pressure deficiency of held water in a capillary tube is termed as ____________

A) Soil suction and suction pressure
B) Negative pressure
C) None of the mentioned
D) All of the mentioned

Answer is A)
Explanation: As the water is decreased linearly in the tube due to the suction of soil mass. The pressure deficiency is also called as soil suction or suction pressure.

5. Which one of the following factor does not affect soil suction?

A) Water content
B) Temperature
C) Plasticity index of a soil
D) Atmospheric pressure

Answer is D)
Explanation: As the atmospheric pressure, does not have any effect on water in the soil mass. It does not contribute to the affecting factor.

6. The soil suction is maximum, when angle of contact(α) is _____________

A) α=0
B) α=90
C) α=60
D) α=1

Answer is A)
Explanation: As soil suction depend on capillary height (hC) Using the formula hc=4Tscos α/γw d When α=0 hc = 4Ts/γw d, which is maximum.

7. Rise in temperature___________soil suction.

A) Decreases
B) Increases
C) Removed
D) None of the mentioned

Answer is A)
Explanation: Rise in temperature results in a decrease of surface tension (TC) and hence decrease in soil suction.

8. Capillary tension is developed in saturated soil, when ___________

A) Soil is dry
B) Water content is reduced
C) Water content is increased
D) Soil particle is large

Answer is B)
Explanation: On decreasing of water content, the menisci recede, resulting in a reduction of curvature and corresponding increase in capillary tension.

9. When do the soil suction is reduced to zero value?

A) Water content is reduced
B) Soil is oven dry
C) Dry soil is submerged
D) All of the mentioned

Answer is C)
Explanation: When a dry soil is submerged under water, meniscus is destroyed resulting in a reduction of soil suction to zero value.

10. The capillary pressure, transferred from grain to grain in soil may be also called as ____________

A) Inter granular pressure
B) Contact pressure
C) Effective pressure
D) All of the mentioned

... Answer is D)
Explanation: Inter granular or contact or effective pressure is the capillary pressure, transferred from grain to grain in soil.