1. The ___________ is made of steel sheet piles and this type of cofferdam is proved successful in unwatering large areas.
a) Suspended cofferdam
b) Cellular cofferdam
c) Dikes
d) Concrete cofferdam
Explanation: Cellular cofferdam consists of diaphragm cells or circular cells or modified circular cells or cloverleaf cells. In case of circular cofferdams with diaphragm cells, the series of arcs are connected to straight cross wall. The radius of arcs is generally made equal to the distance between the cross-walls
2. A __________ consist of timber cribs.
a) Cellular cofferdam
b) Suspended cofferdam
c) Concrete cofferdam
d) Rock-filled crib cofferdam
Explanation: A crib is a box or a cell open at the bottom and it essentially consists of a framework of horizontal timbers laid in alternate courses. The Rock-filled crib cofferdam have been employed with success on many important Jobs. The ideal set of conditions favourable for this type of cofferdam is the depth of water is about 10 meters to 20 m.
3. ___________ is to be incorporated as a part of a permanent structure which have been proved to be economical.
a) Concrete cofferdam
b) Suspended cofferdam
c) Single wall cofferdam
d) Cellular cofferdam
Explanation: Concrete cofferdams are actually small concrete dams and they have been used economically on many Jobs. The Framework usually consists of precast RCC piles and sheets. The main disadvantage of a concrete cofferdam is that it is costly.
4. __________ are the cofferdams which can be lifted, floated and placed in another position as soon as its purpose is served.
a) Dike cofferdam
b) Double wall cofferdam
c) Suspended cofferdam
d) Single wall cofferdam
Explanation: Suspended cofferdams are also known as the movable cofferdams. The suspended cofferdams may take up any forms. In one form, it consists of a hollow steel cylinder which can be used to prepare a temporary enclosed space for the construction work.
5. A _____________ is defined as a structure which is sunk through ground or water to exclude water and semi fluid material during the process of excavation of foundations.
a) Cofferdam
b) Caisson
c) Well
d) Pit
Explanation: A Caisson is a relatively large deep foundation and resembles is pile foundation in transferring the superstructure load to some desired depth. However, Caisson differs from a pile in size and in the method of construction.
6. A _______ becomes uneconomical in cases where the plan area of foundation work is small as compared to the depth of water.
a) Cofferdam
b) Caisson
c) Pile
d) Pit
Explanation: Under such circumstances, cofferdam becomes uneconomical. Hence, caisson would prove to be most suitable. At places where cofferdam cannot be Dewatered successfully, the Caissons are used
7. The _________ is suitable for caissons of Open Well type.
a) Steel
b) Timber
c) Reinforced cement concrete
d) Cast-iron
Explanation: New segments of cast iron are bolted as the caisson sinks. Cast iron is unsuitable for pneumatic caissons as there is risk of failures due to tension developed by the compressed air. The cost also works out to be more in relation to steel or RCC.
8.The __________ is suitable for caisson shoes.
a) Reinforced cement concrete
b) Cast-iron
c) Timber
d) Steel
Explanation: Reinforced cement concrete has more weight and therefore it creates difficulties in handling and floating the Caisson in the early stage of construction. Therefore it becomes economical to construct a Steel Caisson with concrete filling
9. The __________ is found to be the most suitable material for the construction of caisson.
a) Timber
b) Cast iron
c) Steel
d) RCC
Explanation: Steel is usually in the form of a double skin of Steel plating and the hollow space in then filled with cement concrete. Due to its strength and durability it is found to be most suitable material.
10. The ___________ was used as a material for the construction of caisson in the early stages of development of Caisson.
a) Steel
b) Timber
c) Cast iron
d) RCC
Explanation: In old days, Timber was the cheapest material due to its availability in abundance. But this material is now practically not adopted mainly because of its bulk and the risk of Fire.