# Geotechnical Engineering Questions and Answers – Analysis of Well Foundation

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This set of Geotechnical Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Analysis of Well Foundation”.

1. The selection of the depth of a well is based on which of the following criteria?
a) Adequate embedded length should be provided and The well should rest on strata of adequate bearing capacity
b) The perimeter of the well should be minimum
c) None of the mentioned
d) All of the mentioned

Explanation: The selection of the depth of a well is based on the following two criteria:
i) There should be the adequate embedded length of well, called the grip length below the lowest scour level.
ii) The well should be taken deep enough to rest on strata of adequate bearing capacity in relation to the load transmitted.

2. For alluvial soil, the normal scour depth can be calculated by ___________ formula.
a) Rankine’s formula
b) Lacey’s formula
c) Converse Labarre formula
d) Terzaghi’s formula

Explanation: For alluvial soil mostly met with in North Indian Rivers, the normal scour depth can be calculated by Lacey’s formula:
RL = 1.35(q2/f)1/3.

3. The grip length of well is taken as _________ below the scour level in roads.
a) ½ R
b) 1½ R
c) 1/3 R
d) 1 R

Explanation: According to the code of practice of the Indian Road Congress, the grip length is taken as 1/3 R below the scour level.
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4. For piers and abutment, the minimum depth of embedment below the scour level should be taken as _________ m.
a) 2.0
b) 1.2
c) 3
d) 1.5

Explanation: According to IRC code, it is recommended that the minimum depth of embankment below the scour level should not be less than 2.0 m for piers and abutment with arches and 1.2 m for other types of structures.

5. What are the horizontal forces that are prone to act on a well foundation?
a) Wind force
b) Earth pressure
c) Seismic force
d) All of the mentioned

Explanation: A well foundation is liable to the following horizontal forces: i) force on account of water current ii) wind forces iii) seismic forces iv) earth pressure v) centrifugal forces.

6. The analysis of well foundation is done based on the assumptions of _________
b) Lacey
c) None of the mentioned
d) All of the mentioned

Explanation: Based on the assumptions done by Banerjee and Gangopadhyay in 1960, the analysis of well foundation can be done.

7. The maximum depth of scour at the nose of pier is _______ Lacey’s value.
a) Twice
b) Thrice
c) Half
d) None of the mentioned

Explanation: The maximum depth of scour at the nose of the pier, is found to be twice the Lacey’s value of normal scour depth: R = 2RL.

8. Coefficient of horizontal soil reaction m, depends on _________
a) Shape of the area carrying load and Nature of soil
b) Skin friction
c) None of the mentioned
d) All of the mentioned

Explanation: Factor m, called the coefficient of horizontal soil reaction depends on the nature of soil, size and shape of the area which carries the load.

9. When a rigid well starts moving parallel, it transforms the soil in to __________
a) Active and passive states
b) Rigid state
c) Loose sand
d) All of the mentioned

Explanation: When a rigid soil, embedded in sand, starts moving parallel to its original position under the action of a horizontal force, it transforms the soil on one side to passive state and the other side in to active state.

10. According to Terzaghi and Peck, the ultimate bearing capacity can be determined by which of the following expression?
a) Q f = Q p + 2πRfs Df
b) Q p = πR2(Q p + 2πRfs Df)
c) Q p = 2πRfs Df
d) All of the mentioned

Explanation: According to Terzaghi and Peck, the ultimate bearing capacity can be determined from the following expression:
Q f = Q p + 2 π R fs Df
Where R = radius of well, Df = depth of well, fs = average skin friction.

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