# Strength of Materials Questions and Answers – Trapezoidal Dam as Inclined Side Phase

This set of Strength of Materials Questions and Answers focuses on “Trapezoidal Dam as Inclined Side Phase”.

1. Calculate the eccentricity of a trapezoidal dam with a distance between the centre of gravity and point where the resultant cuts the base is 5m. The bottom width of the dam is 3m.
a) 2.5m
b) 3.5m
c) 4.5m
d) 5m

Explanation: The eccentricity (e) = Z – b/2.
Z= distance between the centre of gravity and point where the resultant cuts the base is 5m.
= 5-3/2 = 1.5m.

2. Which of the following is not a failure of retaining wall?
a) Structural slide
b) Shear sliding
c) Crushing
d) Slope pitching

Explanation: Crushing Failure is related to dams. The retaining walls are the structures constructed to store earth on one side especially in case of hill or ghat roads.

3. ________ pressure which occurs commonly in dams.
a) Passive earth pressure
b) Active earth pressure
c) Soil moisture tension
d) Wind pressure

Explanation: Active earth pressure is exerted by backfill on retaining walls. It is also called as practical pressure. It occurs commonly in dams.

4. _________ failures contribute 40% to earthen dams.
a) Seepage
b) Structural
c) Hydraulic
d) Natural

Explanation: On the basis of various investigation reports and case studies, hydraulic failures contribute about 40% of failures to earthen dams. The rest of the failures is shared by seepage failures and structural failures.

5. Which of the following filters are also known as chimney drains?
a) Horizontal filter
b) Inclined filter
c) Rock toe
d) Toe drain

Explanation: The filters which are laid across the outer slope of the impervious core are called as inclined filters. They are also known as Chimney drains. They are provided mainly to collect the seepage emerging out of the core.
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6. Zoned earthen dams are also known as ______
a) Heterogeneous dams
b) Core wall dams
c) Homogeneous dams
d) Hydraulic dam

Explanation: The dams are constructed on shallow pervious foundations in this dam section about outer zones are made fairly pervious material and the inner most zoning called “hearting” is done was fairly impervious material. It is also known as heterogeneous dam.

7. ___________ dams are built with key trenches.
a) Heterogeneous earth dam
b) Homogeneous earth dam
c) Earth Dam with Core wall
d) Rolled fill dam

Explanation: The outer zones of this dam are made of pervious material as in zoned dam. In this case, it is essentially build cut-off wall (cut-off trench) built quite deep preferably upto impervious rock layer in the foundation.

8. Line of seepage is also known as __________
b) Phreatic line
d) Hydraulic seepage line

Explanation: The line within the dam section below which there are positive hydrostatic pressures in a dam and above the line the hydrostatic pressures are negative. It gives a divide line between dry and saturated soils.

9. ____________ represents the top stream line.
a) Phreatic line
b) Hydraulic gradient line
d) Hydraulic seepage line

Explanation: Phreatic line is also called a line of seepage or saturation line. The phreatic line represents the top streamline and hence helps us in drawing the flow net.

10. The hydrostatic pressures on phreatic line are equal to____
a) Zero
b) Maximum
c) Minimum
d) Constant

Explanation: The hydrostatic pressure on phreatic line is equal to atmospheric pressure and hence equal to zero, the flow through the body of the dam below the phreatic line reduces the effective weight of the soil and thus reduces the shear strength of the soil.

11. Expand MWL?
a) Minimum water level
b) Maximum water level
c) Meagre water level
d) Most wind level

Explanation: The water level that is attained during floods is called the maximum water level. The dams and spillway sections are designed to withstand water pressure at this level.

12. ______ is the difference of Level between full reservoir level and top of the dam.
a) Net free board
b) Gross free board
c) Design free board
d) Over free board

Explanation: In dams, in order to prevent the overtopping during peak floods, a sufficient margin is provided between the full reservoir level and top of the dam. This is known as gross free board.

13. By keeping the phreatic line within the downstream toe, the ___________ can be avoided.
a) Piping
b) Gullying
c) Sloughing
d) Over topping

Explanation: If the filter at downstream side toe is choked then also the downstream too becomes saturated. In such circumstances, some erosion occurs in downstream to this causes sloughing. To avoid this phreatic line must be within the downstream toe.

14. Springs(closely coiled) are examples of _____________
a) stiffness
b) hardness
c) toughness
d) creep

Explanation: The property of a material or substance which offers resistance to bending action and measures the load required to be applied is called stiffness. It is denoted by s or k. Springs are the best examples of stiffness.

15. Perennial canals are also known as ________
a) Inundation canal
b) Productive canal
c) Feeder canal
d) Permanent canal

Explanation: The canal which is fed by a permanent source of supply is said to be a permanent Canal. It has also regulatory works. This canal is also sometimes known as a perennial canal.

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