250+ TOP MCQs on Well Hydraulics – Pumping In and Pumping Out Tests – 1 and Answers

Soil Mechanics Multiple Choice Questions on “Well Hydraulics – Pumping In and Pumping Out Tests – 1”.

1. The specific yield S_γ is given by _______
a) (V_wy+V)*100
b) (V_wy-V)*100
c) (V_wy/V)*100
d) (V_wy*V)*100
Answer: c
Clarification: The specific yield S_γ of an aquifer is defined as the ratio of volume of water drained by gravity V_wy to the total volume V. It is expressed as percentage. The specific yield S_γ is an indication of the water yielding capacity of an unconfined aquifer.

2. The value of specific yield depends upon the shape of the pores.
a) True
b) False
Answer: a
Clarification: The specific yield S_γ is given by,
S_γ=(V_wy/V)*100. The specific yield S_γ is proportional to the volume of water drained. This implies that the value of specific yield depends upon the shape of the pores.

3. The specific retention S_R is given by _______
a) (V_wR+V)*100
b) (V_wR-V)*100
c) (V_wR/V)*100
d) (V_wR*V)*100
Answer: c
Clarification: The specific retention S_R of an aquifer is defined as the ratio of volume of water retained V_wR to the total volume V. It is expressed as percentage.

4. The relation between porosity n, specific retention S_R, specific yield S_γ is __________
a) n= S_R-S_γ
b) n= S_R+S_γ
c) n= S_R*S_γ
d) n= S_R/S_γ
Answer: b
Clarification: The porosity n, specific retention S_R, specific yield S_γ is given by,
S_γ=(V_wγ/V)*100 and S_R=(V_wR/V)*100
V_w= V_wγ+ V_wR
But n=(V_w/V)*100
∴ n= S_R+S_γ.

5. In the storage coefficient, the unit change in the component of the head is measured in _________ to the surface.
a) normal
b) tangential
c) radial
d) inclined at 30°
Answer: a
Clarification: The storage coefficient is defined as the volume of water that an aquifer releases per unit surface area per unit change in the component of head normal to that surface.

6. The coefficient of transmissibility is defined as the rate of flow of water through a horizontal strip of unit width and full saturation height under unit hydraulic gradient.
a) True
b) False
Answer: b
Clarification: For a fully saturated soil mass of unit width extending to depth infinity, the discharge through it is known as the coefficient of transmissibility when the hydraulic gradient is unity.

7. If b is the aquifer thickness, the relationship between coefficient of transmissibility T and coefficient of permeability is ________
a) T=bk
b) T=b/k
c) T=b+k
d) T=b-k
Answer: a
Clarification: The coefficient of transmissibility T equals the coefficient of permeability k multiplied by the aquifer thickness b.
T=bk.

8. The drawdown, corresponding to a steady discharge, are observed at a number of wells in _______
a) pumping out test
b) pumping in test
c) constant head permeability test
d) falling head permeability test
Answer: a
Clarification: The permeability can be determined by pumping out test. Pumping must continue at a uniform rate for a sufficient time to approach a steady state condition.

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