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

Hello there,
How have you been!?
 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.



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