Test 38 - Canal Falls, Types and Design Principles

Question 1 ప్రశ్న 1

Why are canal falls commonly required when the natural ground slope is steeper than the designed canal-bed slope?

A To increase the canal bed slope until it becomes equal to the natural ground slope everywhere B To absorb the excess difference in elevation through controlled drops while maintaining the designed canal gradient C To eliminate the need for canal banks D To make the canal flow permanently critical

Question 2 ప్రశ్న 2

The natural ground falls at 1 in 2000 while the designed canal bed falls at 1 in 5000. Over a horizontal distance of 3 km, what excess fall must approximately be absorbed by canal falls if the two profiles start at the same elevation?

A 0.30 m B 0.60 m C 0.90 m D 1.50 m

Question 3 ప్రశ్న 3

Which consideration is most appropriate when selecting the location of canal falls along a canal alignment?

A Falls should be placed at arbitrary equal distances regardless of topography B Their locations should coordinate the natural ground profile, designed canal grade, permissible earthwork, required drop and overall economy C Every fall must be located only at a village road crossing D Falls should be placed only where the canal is in its deepest cutting

Question 4 ప్రశ్న 4

What is the principal energy-dissipation mechanism in a simple vertical-drop canal fall?

A Only boundary friction along a very long horizontal canal reach B Impact and turbulent mixing of the falling jet in the downstream cistern or water cushion C Centrifugal force in a curved pipe D Seepage through the canal foundation

Question 5 ప్రశ్న 5

Which statement best describes a straight-glacis canal fall?

A Water is conveyed entirely through a buried pressure pipe B The downstream side contains a sloping glacis leading to a protected basin where a hydraulic jump may be formed C It has no raised crest and no energy-dissipation arrangement D Its only purpose is to measure sediment concentration

Question 6 ప్రశ్న 6

Why is it generally undesirable simply to adopt the steep natural ground slope as the canal-bed slope when that ground slope greatly exceeds the hydraulically designed canal slope?

A Because a steep canal slope can produce excessive velocity, erosion and unstable hydraulic conditions B Because canal water cannot flow downhill C Because discharge becomes zero on steep slopes D Because the canal bed must always be horizontal

Question 7 ప్రశ్న 7

Which description best characterizes a stepped or cascade canal fall?

A The total drop is divided into a series of smaller successive drops or steps B The entire discharge is pumped vertically upward C The fall consists only of a single vertical sheet pile D The structure contains no provision for energy dissipation

Question 8 ప్రశ్న 8

Why may a trapezoidal-notch fall be preferred in a small canal whose discharge varies substantially?

A Because its notch arrangement can provide better control of upstream depth over a range of relatively small discharges B Because it eliminates all downstream energy dissipation C Because it requires the canal to operate under pressure D Because it always gives zero afflux

Question 9 ప్రశ్న 9

What is meant by a flumed canal fall?

A A fall in which the effective waterway through the structure is contracted below the normal canal width B A fall having no crest C A fall in which the canal width is deliberately doubled D A fall constructed only in an underground tunnel

Question 10 ప్రశ్న 10

A canal carries 24 m³/s through a fall. If the adopted discharge intensity through the fall waterway is 4 m³/s per metre width, what effective waterway is required?

A 4 m B 6 m C 8 m D 12 m

Question 11 ప్రశ్న 11

For a canal fall, use the idealized crest relation Q = C L H^(3/2). If Q = 30 m³/s, C = 1.84 and crest length L = 10 m, what head H is required?

A Approximately 0.82 m B Approximately 1.00 m C Approximately 1.39 m D Approximately 2.25 m

Question 12 ప్రశ్న 12

For the fall in the previous question, the upstream total energy level is RL 105.20 m and the required total head over the crest is 1.385 m. What crest elevation follows from these supplied values?

A RL 103.815 m B RL 104.200 m C RL 105.200 m D RL 106.585 m

Question 13 ప్రశ్న 13

What is the principal hydraulic consequence of making the effective waterway of a canal fall excessively narrow?

A Velocity and required upstream head may increase, producing excessive afflux and transition losses B The discharge must become zero C The downstream canal automatically becomes wider D All energy dissipation becomes unnecessary

Question 14 ప్రశ్న 14

In canal-fall terminology, what does afflux generally mean?

A The rise of upstream water level caused by the hydraulic obstruction or contraction introduced by the structure B The fall of groundwater table due to evaporation C The vertical drop in canal bed across the fall D The sediment concentration downstream of the structure

Question 15 ప్రశ్న 15

Why are inlet and outlet transitions especially important in a flumed canal fall?

A They gradually contract and expand the flow, reducing separation, crosswaves and excessive local losses B They increase abruptness of the width change C They eliminate the need for a crest D They are provided only for architectural appearance

Question 16 ప్రశ్న 16

Water enters the hydraulic-jump portion of a glacis fall at depth y1 = 0.60 m with an incoming Froude number Fr1 = 4.0. Using y2/y1 = 0.5[sqrt(1 + 8Fr1²) - 1], what is the approximate sequent depth y2?

A 1.20 m B 2.40 m C Approximately 3.11 m D 4.80 m

Question 17 ప్రశ్న 17

A canal fall dissipates an available head of 1.5 m while passing 8 m³/s. Neglecting other losses and using ρ = 1000 kg/m³ and g = 9.81 m/s², what rate of hydraulic energy must approximately be dissipated?

A 11.77 kW B 58.86 kW C 117.72 kW D 981 kW

Question 18 ప్రశ్న 18

For a glacis fall designed to contain a hydraulic jump, what is a likely consequence if the available downstream depth is substantially smaller than the required sequent depth?

A The hydraulic jump may sweep downstream beyond the protected basin B The jump must move into the upstream canal C The incoming flow becomes subcritical before reaching the glacis D Energy dissipation becomes unnecessary

Question 19 ప్రశ్న 19

What may occur if the downstream water depth at a glacis fall is substantially greater than that required for a free hydraulic jump?

A The jump may become submerged or drowned B The canal discharge necessarily becomes zero C The downstream water disappears D The flow must become more supercritical

Question 20 ప్రశ్న 20

What is the primary function of downstream pitching, apron or other protective works below a canal fall?

A To protect the canal bed and banks against residual turbulence and scour after the main energy-dissipation region B To raise the upstream full-supply level indefinitely C To increase seepage beneath the structure D To prevent all water from entering the downstream canal

Question 21 ప్రశ్న 21

Which fall type is most directly associated with deliberate formation of a hydraulic jump as the main energy-dissipation mechanism?

A Straight-glacis fall B Simple vertical-impact fall C Pipe drop relying entirely on closed-conduit friction D A canal escape without any drop

Question 22 ప్రశ్న 22

A canal carries a small discharge that varies widely during operation, and maintaining a reasonably suitable upstream depth-discharge relationship is important. Which traditional fall type is especially associated with this requirement?

A Trapezoidal-notch fall B A completely uncontrolled steep earth chute C A plain embankment breach D A canal siphon used as a fall under every condition

Question 23 ప్రశ్న 23

When would a fall-cum-cross-regulator arrangement be particularly useful?

A When the canal requires both a controlled bed-level drop and regulation of upstream water level or discharge at approximately the same site B When no change in bed level or regulation is required C Only when the canal is permanently dry D Only when groundwater pumping is required

Question 24 ప్రశ్న 24

Which statement about crest level selection for a canal fall is most appropriate?

A It should be coordinated with the upstream full-supply or energy level, design discharge, allowable afflux and downstream conditions B It is fixed only by the colour of the masonry C It should always be above the canal banks D It is unrelated to discharge and upstream water depth

Question 25 ప్రశ్న 25

Consider the following statements about canal falls: I. They are commonly required when natural ground slope exceeds the designed canal slope. II. A flumed fall uses a contracted waterway and therefore requires suitable transitions. III. A glacis fall can use a hydraulic jump for energy dissipation. IV. Downstream protection may still be required after the principal energy-dissipation zone. Which option is correct?

A I and II only B I, II and III only C II, III and IV only D I, II, III and IV

Question 26 ప్రశ్న 26

Which combination represents the most complete hydraulic design approach for a canal fall?

A Select only the visible drop height and ignore upstream and downstream water levels B Coordinate the required drop, crest level, effective waterway, allowable afflux, transitions, energy-dissipation arrangement, hydraulic-jump or impact condition, foundation safety and downstream protection C Choose the narrowest possible waterway regardless of head loss D Design only the crest and allow the downstream bed to erode naturally

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