250+ TOP MCQs on Well Hydraulics – Pumping In and Pumping Out Tests – 2 and Answers

Soil Mechanics Interview Questions and Answers for Freshers on “Well Hydraulics – Pumping In and Pumping Out Tests – 2”.

1. The formula for the pumping out test in an unconfined aquifer is given by _________
a) (k=frac{qπ}{1.36(H^2-h^2)}log_{10}frac{R}{r} )
b) (k=frac{q}{1.36(H^2-h^2)}log_{10}frac{R}{r} )
c) (k=frac{q}{π(H^2-h^2)}log_{10}frac{R}{r} )
d) (k=frac{q}{1.36(H^2-h^2)} )
Answer: b
Clarification: From Darcy’s law,
q=kAi
A=2πxy
(i=frac{dy}{dx} )
(q=k2πxy frac{dy}{dx} ,or, frac{dx}{x}= k2πydy)
integrating between (R,r) for x and (H,h) for y,
(int_r^R q frac{dx}{x} =2kπ∫_h^H ydy )
∴ (k=frac{q}{1.36(H^2-h^2)}log_{10}frac{R}{r} )

2. The formula for the pumping out test in an unconfined aquifer is given by _________
a) (k=frac{qπ}{1.36(H^2-h^2)}log_{10}frac{R}{r} )
b) (k=frac{q}{1.36(H^2-h^2)}log_{10}frac{R}{r} )
c) (k=frac{q}{2.72b(H-h)}log_{10}frac{R}{r} )
d) (k=frac{q}{1.36(H^2-h^2)} )
Answer: c
Clarification: From Darcy’s law,
q=kAi
A=2πxb
Where b=thickness of confined aquifer
(i=frac{dy}{dx} )
q=k2πxb (frac{dx}{x} ,or, frac{dx}{x}= k2πbdy)
integrating between (R,r) for x and (H,h) for y,
(∫_r^R q frac{dx}{x} =2kπb∫_h^H dy )
∴ (k=frac{q}{2.72b(H^2-h^2)}log_{10}frac{R}{r}. )

3. The permeability of the aquifer is ________ if the drawdown is 4m, discharge is 40litres/sec, thickness of confined aquifer is 30m and the radius of the well is 0.1m. The radius of influence is taken as 245m.
a) 36 m/day
b) 30 m/day
c) 26 m/day
d) 20 m/day
Answer: a
Clarification: Given,
Drawdown=4m
Discharge q=40litres/sec
thickness of confined aquifer b=30m
radius of the well r=0.1m
radius of influence=245m
the permeability is given by,
(k=frac{q}{2.72b(H-h)} log_{10}frac{R}{r} )
(k=frac{0.04}{(2.72*30*4)}log10frac{245}{0.1} )
∴k=36 m/day.

4. In the field determination, pumping must continue at a ________
a) uniform rate for sufficient time to approach steady state
b) non- uniform rate for sufficient time to approach steady state
c) uniform rate until just before time to approach steady state
d) non-uniform rate until just before time to approach steady state
Answer: a
Clarification: The steady state condition is the one in which the drawdown changes negligibly with time. In order to get accurate results, pumping must continue at a uniform rate for sufficient time in the field determination to approach steady state.

5. The U.S. Bureau of Reclamation (Earth manual 1960) has devised two types of pumping-in tests _________
a) open-end test and packer test
b) permeability test and radio test
c) dupin test and influence test
d) falling head and constant head permeability test
Answer: a
Clarification: The pumping-in tests includes open-end test and packer test. The falling head and constant head permeability test are also used to determine the permeability but are laboratory tests.

6. The formula for the open-end test is given by _________
a) (k=frac{q}{5.5rh} )
b) (k=frac{5.5rh}{q} )
c) (k=frac{q}{5rh} )
d) (k=frac{q}{0.5rh} )
Answer: a
Clarification: The permeability can be calculated from,
(k=frac{q}{5.5rh}) where k=permeability
q=discharge or constant rate of flow
r=radius of casing
h=differential head of water.

7. The coefficient of permeability by Packer for length greater than ten times the radius test is given by ________
a) (k=frac{q}{2πh}log_{10} frac{L}{r})
b) (k=frac{v}{2πLh}log_{10} frac{L}{r})
c) (k=frac{q}{2Lh}log_{10} frac{L}{r})
d) (k=frac{q}{2πLh}log_{10} frac{L}{r})
Answer: a
Clarification: The coefficient of permeability k for L ≥ 10r is given by,
(k=frac{q}{2πLh}log_{10} frac{L}{r})
where, q=discharge or constant rate of flow
r=radius of casing
h=differential head of water
L=length of portion of hole tested.

8. The coefficient of permeability by Packer for length in the range 10r > L ≥r test is given by ________
a) (k=frac{q}{2πh}log_{10} frac{L}{r} )
b) (k=frac{q}{2πLh}log_{10} frac{L}{r} )
c) (k=frac{q}{2Lh}log_{10} frac{L}{r} )
d) (k=frac{q}{2πLh}sinh^{-1}frac{L}{2r} )
Answer: d
Clarification: The coefficient of permeability k for 10r > L ≥r is given by,
(k=frac{q}{2πLh}sinh^{-1}frac{L}{2r} )
where, q=discharge or constant rate of flow
r=radius of casing
h=differential head of water
L=length of portion of hole tested.

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