One Liners | GATE, PSUs 2022 | Hydraulics, Irrigation, Water Resource Engineering | part 7

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 Here is the 7th part of our notes for preparation of GATE and other examinations related to Civil Engineering.

• As compared to gravity dams, earthen dams require less skilled labor.
• The most suitable material for the central impervious core of a zoned embankment type dam is clay mixed with fine sand.
• Seepage through embankments in the earthen dam is controlled by drain trenches.
• Seepage through the foundation in an earthen dam is controlled by providing impervious cut-off.
• The flow of water after spilling over the weir crest in the chute spillway and side-channel spillway respectively are at a right angle and parallel to the weir crest.
• The discharge passing over an Ogee spillway is given by CLH^(3/2) where L is the effective length of spillway crest and H is the total head over the spillway crest including velocity head.
• The coefficient of discharge of an Ogee spillway depends on the depth of approach and upstream slop and also on downstream apron interference and downstream submergence.
• Ogee spillway is least suitable for earthen dams as compared to chute spillway, side-channel spillway, and shaft spillway.
• In the case of the non-availability of space due to topography, the most suitable spillway is the shaft spillway.
• In the case of chute spillway, the flow is usually super-critical.
• For the upstream face of an earthen dam, the most adverse condition for stability of slope is sudden draw-down.
• If there are two canals taking off from each flank of a river, then there will be two divided walls and two under-sluices.
• Generally, the weir is aligned at right angles to the direction of the main river current because, it ensures less length of the weir, gives better discharging capacity, and is economical.

• The main function of the divider wall is to separate the under-sluices from the weir proper.
• A divider wall is provided at the right angle to the axis of the weir.
• As compared to the crest of the normal portion of the weir, the crest of the under-sluice portion of the weir is kept at a lower level.
• Silt excluders are constructed on the river bed upstream of the head regulator.
• If 'h' is the ordinate of hydraulic gradient line above the top of the floor and G is the specific gravity of floor material, then the thickness of the floor is given by the formula h/(G-1).
• According to Khosla's theory, the exit gradient in the absence of a downstream cutoff is infinity.
• The minimum size of stone that will remain at rest in a channel of longitudinal slope S and hydraulic mean radius R is given by 11 RS.
• The ratio of average values of shear stress produced on the bed and the banks of a channel due to flowing water is greater than 1.
• If the critical shear stress of a channel is Tc, the average value of shear stress required to move the grain on the bank is 0.75Tc.
• A watershed canal avoids the cross drainage works.
• A canal that is aligned at right angles to the contours is called a side slope canal.
• Garret's diagrams are based on Kennedy's theory.

All information is learned through books and practical exercises.

References (Also the best books for GATE and PSU preparations):

1.  Civil Engineering Objectives by S P Gupta
2. GKP GATE 2022 Guide by GK Publishers
3. Previous 31 Years of Solved GATE Papers by Made Easy

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