1. What are the types of caissons that can be used as a foundation?
a) Box caissons and Open caissons
b) Closed caissons
c) None of the mentioned
d) All of the mentioned
Explanation: The caissons are of three types: i) Box caissons ii) open caissons iii) pneumatic caissons.
2. Which of the following caissons, permits excavation in dry?
a) Pneumatic caissons
b) Box caissons
c) Open caissons
d) All of the mentioned
Explanation: A pneumatic caisson has its lower end designed as a working chamber in which compressed air is forced to prevent the entry of water and thus permit excavation in dry.
3. The sinking of the dredge is uniform in which of the following, shapes of well?
a) Double-D
b) Rectangular
c) Circular
d) Dumb-well
Explanation: As the perimeter of the circle is equidistant at all points from the center of the dredge hole, the sinking is more uniform than other shapes.
4. The components that are needed to be considered in designing of a well foundation is _______
a) Shape of the well
b) Sand filing
c) Bottom plug
d) Dredge hole
Explanation: The following components of a well have to be considered in the design of a well foundation: well curb cutting edge, steining, Bottom plug and well cap.
5. A disadvantage in using circular shape of well foundation is ___________
a) Minimum perimeter
b) Skin friction is maximum
c) Diameter of well is more than required
d) Sinking is more uniform
Explanation: The disadvantage of a circular well is that in the direction parallel to the span of the bridge, the diameter of the well is much more than the minimum size required.
6. The most economical shape, of a well for the construction of large pier is _________
a) Twin circular
b) Double-D
c) Rectangular
d) Single circular
Explanation: The dredge area for a double-D shape is smaller when compared to others; hence it can be more economical than a singular circular well.
7.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.
8. 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.
9. 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.
10. 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.