Hydraulic Structures
Dr. Shahid Ali
Classification Of Flow Type
Specific weight (w)=𝜌g
 Weir:- A weir is structurally safe streamlined wall built at a suitable
site across a river. It a low head- structure for the purpose of diverting
river water.
 A weir is built to raise the water level to the height required to divert
water into the canals commanding the area to be irrigated.
 Barrage:- If the weir is provided with the gates to raise the water
level then such a weir is called a low head diversion dam or a barrage
Barrage is French word means “Blocking or Barrier”
Weir is derived from “Were” (Frician) or “Wehr” (German)
canal
It is essential to keep the level of pond some 0.75- 1 m above the FSL.
avoid
f
Mr is mean diameter of river bed material particles in mm.
• u/s and d/s sheet piles prevent failure of weir due to undermining of the foundation.
• The intermediate sheet pile neither prevents undermining nor it alters pressure distribution
substantially to reduce uplift pressure under d/s floor. The main purpose of providing intermediate
sheet pile is create second line of defense in case of failure of either u/s or d/s sheet piles.
• The pressure under downstream floor increases as the depth of downstream sheet pile increases.
19.52
For other Barrage Bays
 Narora Weir
 This barrage across Ganges
river was completed in 1878.
 Failure of Khanki barrage
 In 1892 a large weir about 4097 ft long, divided by piers and groynes into 8 bays, was
built on sand foundation across the river Chenab at khanki
 In the floods of 1893 a portion of the weir crest in bay no. 5 sub sided in about a length
of 55 feet. Some repairs were carried out but in January, 1895 about 100 ft of the weir
crest in bay no. 1 subsided by 2 ft. in October and November of the same year further
subsidence of crest in Bay no. 1, took place.
 One of the cause of failure was piping under the structure.
 It was decide to conduct the series of experiments at civil engineering college of
Roorkee on flow of water through sand to establish the design criteria for the safe
design of weir. And to investigate causes of failure.