1. Unequal dredging of well causes _________
a) Collapsing of well
b) Tilting
c) Open excavation
d) Maximum skin friction
Explanation: When the dredging is done unequally tilts and cannot be rectified if the well is sunk to a greater depth.
2. To counter act the tilts in the well during sinking operations, which of the following measures can be used?
a) Regulation of grabbing
b) Strutting the well
c) Pushing by jack
d) All of the mentioned
Explanation: Any of the following measures can usefully be employed to counteract the tilts in the well during sinking operations: i) regulating of grabbing ii) water jetting iii) eccentric loading iv) pulling the well vi) pushing by jacks.
3. In which of the following methods, hydraulic jack is used to counter attack the tilt in the well?
a) Pulling the well
b) Eccentric loading
c) Pushing by jack
d) Pulling the well
Explanation: In pushing by jack method, the well may be pushed by force applied by hydraulic or mechanical jack on the tilted side of the wall.
4. The essential feature of a pneumatic caissons are __________
a) Tilting can be avoided and Removing water by Compressed air
b) Skin fraction is zero
c) None of the mentioned
d) All of the mentioned
Explanation: The essential feature of a pneumatic caisson is that compressed air is used to exclude or remove water from the working chamber at the bottom.
5. The method of construction of pneumatic caisson is similar to ________
a) Box caissons
b) Open caissons
c) Rectangular caissons
d) All of the mentioned
Explanation: The method of construction of pneumatic caisson is similar to that for open caissons (well) except that the working chamber is kept air tight.
6. The working chamber of pneumatic caissons are kept airtight because ________
a) To avoid tilting
b) To remove the soil
c) To prevent water from entering the chamber
d) None of the mentioned
Explanation: In order that sub-soil water may not enter the working chamber, the pressure of air in the shaft is kept airtight.
7. The allowable pressure that is allowed inside the working chamber of pneumatic caissons is _______
a) 2 kg/cm2
b) 4 kg/cm2
c) 3.5 kg/cm2
d) 7 kg/cm2
Explanation: Normally the tolerable air pressure under which a man can work is limited to 3.5 kg/cm2 in pneumatic caissons.
8. Advantage of using pneumatic caissons are _________
a) Affords easy inspection and Process is done under control conditions
b) Sinking process is easy
c) None of the mentioned
d) All of the mentioned
Explanation: An advantage of pneumatic caisson is that the entire process of sinking well is carried out under controlled conditions and it affords easy inspection work.
9. Disadvantage of using pneumatic caissons are ________
a) Process cannot be done under control conditions
b) Sinking process is tedious
c) Inspection process is time consuming
d) All of the mentioned
Explanation: In pneumatic caissons, the sinking of pneumatic caissons are tedious, time consuming and expensive.
10. In order to assist sinking of well __________ method is used in pneumatic caissons.
a) Air pressure is reduced and Using explosive
b) Using airlocks
c) None of the mentioned
d) All of the mentioned
Explanation: In order to assist sinking process, air pressure may be reduced for a short while. Sometimes explosive may be employed in this case, it is essential to make arrangements for the immediate removal of fall fumes