This set of Construction and Building Materials Multiple Choice Questions & Answers (MCQs) focuses on “Cofferdam and Caisson”.
1. A _______ is defined as a temporary structure which is constructed so as to remove water and/or soil from an area and make it possible to carry on the construction work under reasonably dry conditions.
a) Cofferdam
b) Foundation
c) Caisson
d) Spillway
View Answer
Explanation: The cofferdam is generally constructed at the site of work. The cofferdam should be reasonably watertight. It may either raised on the impervious soil or may be extended to impervious strata through pervious soils. It should be noted that absolute water tightness is not desired in a cofferdam.
2. A _________ is an embankment of some material.
a) Wall
b) Intrusion
c) Dike
d) Rock-fill
View Answer
Explanation: The materials commonly employed for the construction of dike are earth, rock and sand bags. The dike are generally employed for a short duration, particularly to enable the construction of a more durable cofferdam behind them.
3. __________ is the simplest form of cofferdam.
a) Single wall cofferdam
b) Earth-fill cofferdam
c) Cellular cofferdam
d) Rock-fill cofferdam
View Answer
Explanation: Earth dikes or Earth-fill cofferdams are limited to Shallow depth of water, say about 1200 mm to 1500 mm, with a low velocity of flow. It consists of an Earth bank which is placed around the site to be enclosed.
4. ________ type of cofferdam is economical at places where rock is available in plenty.
a) Earth dikes
b) Sand-bags dikes
c) Rock-fill cofferdam
d) Single wall cofferdam
View Answer
Explanation: Rock dikes or Rock-fill cofferdams can be used for a depth of water up to about 3 metres and a suitable even in case of Swift water. The only disadvantage of this type of cofferdam is that it is not impervious.
5. In __________ type of cofferdam consists of a mixture of sand and clay which is filled in a bag and placed instead of earth or rock to form a cofferdam.
a) Cellular cofferdam
b) Earth dikes
c) Rock dikes
d) Sand-bag dikes
View Answer
Explanation: The sand-bag dykes or Sand-bag cofferdams are useful for small depth of water. The individual bags are laid in courses as in case of masonry work and the joints are filled with puddle.
6. __________ it suitable when available working space is limited and the area to be enclosed is small.
a) Single wall cofferdam
b) Double wall cofferdam
c) Dikes
d) Concrete cofferdam
View Answer
Explanation: Single wall cofferdams is suitable up to a maximum depth of water of 25 m. In this type of cofferdam, a single row of Piles is used on either side of the cofferdam. The sheet pile maybe of wood or steel. The wooden piles are generally used for depth of water up to about 10 m.
7. When the area to be enclosed is large, it becomes essential to provide the _________ construction so as to give stability to the cofferdam.
a) Single wall cofferdam
b) Cellular cofferdam
c) Double wall cofferdam
d) Suspended cofferdam
View Answer
Explanation: Double wall cofferdam was frequently used on the river Ohio in USA and hence, it derives its name as Ohio river type cofferdam. It is cheap and can be built up rapidly l. It is suitable for hard bed where there is no problem of erosion. This type of cofferdam is unsuitable for deep water.
8. __________ is useful when depth of water is about 6 metres to 10 meters.
a) Wood or steel sheeting cofferdam
b) Ohio river type cofferdam
c) Rock-filled crib cofferdam
d) Suspended cofferdam
View Answer
Explanation: For small and ordinary type of cofferdam, the wooden sheet piles are employed. But when cofferdams are large or where it is not possible to drive guide piles due to more depth of water, the steel sheet piles with suitable bracing are used for the construction of this type of cofferdam.
9. 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
View Answer
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.
10. A __________ consist of timber cribs.
a) Cellular cofferdam
b) Suspended cofferdam
c) Concrete cofferdam
d) Rock-filled crib cofferdam
View Answer
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.
11. ___________ 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
View Answer
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.
12. __________ 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
View Answer
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.
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