# Irrigation Engineering Questions and Answers – Types of Spillway Gates

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This set of Irrigation Engineering Multiple Choice Questions & Answers (MCQs) focuses on “Types of Spillway Gates”.

1. In a fixed roller of a spillway gate, the rollers are attached to the __________________
a) gate
b) groove gate
c) either gate or groove gate
d) guide grooves

Explanation: Rollers are generally attached to the gate and ride in tracks on the downstream side of the groove guide. The openings between the upstream leaf plate and the sides of the pier grooves are sealed using rubber seals.

2. In the vertical Stoney spillway gate, the rollers are placed between the ______________
a) gate and u/s groove guide
b) gate and the d/s groove guide
c) u/s and d/s groove guide
d) attached to the gate and groove guides

Explanation: A train of the roller is generally placed in between the gate and the d/s guide. These rollers may be placed independent of the gate and the guide thus eliminating the axle friction but rolls vertically between the two when the gate is moved.

3. The spillway gate which when lowered cannot be seen from a distance is of the type ______________________
a) Sliding gate
b) Roller gate
c) Tainter gate
d) USBR drum gate

Explanation: The system of drum gates consists of a segment of a cylinder which may be raised or lowered into the recess made into the top of the spillway. Whenever the drum is lowered, the surface becomes coincident with the designed ogee shape of the crest.
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4. An ogee spillway of a concrete gravity dam having FRL of 328 m and MWL of 340 m is provided with vertical gates between piers erected on the spillway. The effective length of the spillway is 60 m. The discharge through the spillway when gates are opened up to the actual reservoir level of 331.0 m will be_____________
a) 850 cumecs
b) 1700 cumecs
c) 2800 cumecs
d) 1000 cumecs

Explanation: The discharge is given by the equation –
Q = Cd. A. (2gH)1/2
Where Cd is the coefficient of discharge through the orifice
A is the area of the opening = 60 x 6 =360 m2
H is the water head over the centre line of the opening = RL (331 – 328) = 3m
Q = 0.62 x 360 x (2 x 9.81 x 3)1/2 = 1700 cumecs.

5. The most common vertical lift gates in modern days is _________________
a) sliding gates
b) free-roller gates
c) stoney gates
d) fixed wheel gates

Explanation: The design and construction of free-roller gate are difficult as the rollers are not attached to the gate and the guide. Therefore, the rollers are attached to the gate. Large vertical lift gates are broken into two horizontal sections to reduce the load on the hoisting mechanism.

6. The working of Reinold’s gate is automatic.
a) True
b) False

Explanation: It is a rectangular gate fixed with rollers and it moves up and down along the upstream vertical face of the spillway. The gate is suspended by means of chains which pass over the pulleys and to the other end of the chains a counterweight is attached.

7. Which of the following gate is also called flush boards?
a) Dropping shutters
b) Tainter gates
c) Drum gates
d) Vertical lift gates

Explanation: Dropping shutters are also called permanent flush boards. They are generally used to raise the water level by 1 to 1.25 m. This type consists of shutters or plates made of steel which are hinged at the bottom.

8. Which one of the following gate is not suitable for curved crests?
a) Flush boards
b) Tainter gates
c) Drum gates
d) Vertical lift gates

Explanation: In flush boards, the shutters are hinged at the bottom and are supported by struts. Whenever the water level rises above the top of the shutters they dropdown. Hence they are not suitable for curved crests.

9. Which of the following gate works on the principle of counterweights against the water pressure?
a) Dropping shutters
b) Stop logs and needles
c) Stoney roller gate
d) Drum gates

Explanation: In dropping shutters, the shutters are hinged at the bottom and are supported by struts and these shutters can be raised or lowered from an overhead cableway or a bridge. They work on the principle of counterweights against the water pressure.

10. ________________ are used only for very minor works.
a) Dropping gates
b) Stop logs and needles
c) Rectangular gates
d) Drum gates

Explanation: A Stop log consists of wooden beams and planks placed on to one another and leakage between them is a big problem. Needles are wooden logs kept side by side and it is very difficult to handle these logs at the time of flow. Hence they are not used on any major works.

11. Which of the following gate is not suitable for smaller spillways?
a) Drum gates
c) Needles and stop logs
d) Fixed roller gates

Explanation: Drum gates are suitable for longer spans of the order of 40 m or so and medium heights of 10 m or so. The drum is enclosed on all the three sides as well as on the ends thus forming a water-tight vessel. It requires a large recess and is not suitable for small spillways.

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