# Strength of Materials Questions and Answers – Dams

This set of Strength of Materials Multiple Choice Questions & Answers (MCQs) focuses on “Dams”.

1. The obstruction or a barrier built across the stream or river is called _____________
a) Barrage
b) Weir
c) Dam
d) Reservoir

Explanation: A dam may be defined as an obstruction or a barrier built across the stream or river these are artificial storage works. It retains water to create an impounding reservoir.

2. FTL Stands for ________
a) Free tank level
b) Full tank level
c) Full top level
d) Fill toe level

Explanation: It is also called a full reservoir level (FRL). It is a level up to which the water stored obviously the crest of the spillway is fixed at this level.

3. _______ is openings extending from upstream to downstream of the dam.
a) Guide banks
b) Divide voids
c) Sluices
d) Spillway

Explanation: Sluices are openings or conduits extending from upstream face of the dam to downstream face of the dam. They are used to clean the silt from the reservoir. They also decrease the peak flood in the reservoir.

4. Water stored in dam is expressed in _______
a) Mega cumec metres
b) Million cubic metres
c) Metric cumec
d) Million cusec metres

Explanation: It is the total quantity of water stored up to FRL. It includes dead storage also. It is expressed generally in thousand hectare metre or million cubic metres (Mm3).

5. MDDL Stands for ________
a) Minimum draw down level
b) Maximum draw down level
c) Million drop down level
d) Mega drop down level

Explanation: It is the lowest level up to which the reservoir is depleted from the considerations of hydropower generation. So this level is known as minimum draw down level (MDDL).
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6. _____ dam which resists are the external forces by virtue of its self weight.
a) Earthen dam
b) Storage dam
c) Detention dam
d) Gravity dam

Explanation: A gravity dam is that, which is stable against all the external forces achieved by the weight of the dam itself. This is the most permanent one and hence it is very commonly used. It may be constructed in all localities.

7. The factor of safety against overturning should not be less than ______
a) 1.8
b) 2.25
c) 1.5
d) 1.75

Explanation: In the dam section, the overturning takes place when a resultant force cuts the base of the dam downstream of the toe. The factor of safety against overturning is the ratio of the stabilizing moment to the overturning moments. The safety against overturning should not be less than 1.5.

8. In sliding failure, the co-efficient of friction varies from ________
a) 0.65 – 0.75
b) 0.8 – 0.9
c) 0.45 – 0.65
d) 0.85 – 1

Explanation: To avoid sliding, the factor of safety against the sliding should be greater than 1.
F.S = M(V-U) / €H > 1
Where M = Co-efficient of friction. It varies from 0.65 to 0.75
V = Total vertical force
U = Upward force.

9. Which of the following forces do not act on the dam?
a) Silt pressure
b) Wave pressure
c) Creep pressure
d) Uplift

Explanation: Among the above forces, creep pressure does not act on the dam. Generally on gravity dam number of forces such as water pressure, wave pressure, wind pressure, ice pressure etc. will be acting in a horizontal direction. In the same way, uplift, self weight acts in vertical direction.

10. The elementary profile of a dam is generally a ________
a) Isosceles triangle
b) Right angled triangle
c) Scalene triangle
d) Equilateral triangle

Explanation: In the absence of any other forces, the forces due to water and self weight of the dam form an elementary profile which will be in triangular section having zero top width at water level, where the pressure is zero and maximum base width is at bottom where the maximum water pressure acts.

11. _____ acts as an inspection chamber in Dams.
a) Spillway
b) Heel
c) Drainage gallery
d) Toe

Explanation: A drainage gallery is an opening in the body of a dam which runs longitudinally. It runs through the length of the dam. Generally, it is a rectangle shape with flat a semi-circular head usually 1.5 m wide and 2.5m height.

12. The minimum standard height for a construction joint is about ________
a) 1.2 m
b) 1.5 m
c) 2.1 m
d) 2.3 m

Explanation: The joints which facilitate construction of the dam to proceed in small lifts. These joints are also known as horizontal joints. A lift may be defined as the vertical distance between two consecutive construction joints. The height is about 1.5 m each.

13. Cracks developed in the body of dam section can be avoided by ________
a) Construction joints
b) Contraction joints
c) Transverse joints
d) Longitudinal joints

Explanation: Due to variation in temperature it causes contraction and expansion in masonry or concrete of the dam. It will develop fine cracks in the body of the dam. By providing contraction joints, these cracks can be avoided.

14. ______ is the over flow section or portion of the dam.
a) Heel
b) Toe
c) Spillway
d) Gallery

Explanation: A spillway is the overflow section or portion of the dam over which surplus discharge flows from reservoir to downstream face. This structure is provided in the body of the dam or near the dam or on the periphery of the reservoir.

15. _______ is the common type of spillway used in gravity dams.
a) Ogee spillway
b) Trough spillway
c) Side channel spillway
d) Emergency spillway

Explanation: An ogee spillway is very common type of spillway used in gravity dams. It consists of two parts namely ¡)ogee crest and ¡¡) a bucket. In this spillway water spills and flows over and ogee crest in the form of a rolling sheet of water. Due to this, the development of negative pressures can be avoided.

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