Types of weirs. (a) Masonry weirs with vertical drop. (b) Rock-fill weirs with sloping aprons. (c) Concrete weirs with sloping glacis. Masonry. Types of Weirs. (a) Masonry weirs with vertical drop. (b) Rock-fill weirs with sloping aprons. (c) Concrete weirs with sloping glacis. Lecture structure on pervious foundation- Khosla’s theory-. Design of concrete sloping glacis weir. ❑Weir or barrage is constructed across a perennial river to raise.
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We think you have liked this presentation. If you wish to download it, please recommend it to your friends in any social system. Share buttons are a little bit lower. Published by Lance Grime Modified over 3 years ago. Canal fall or drop: A structure designed to secure lowering of the water surface in a canal and to slping safely the surplus energy so liberated, which otherwise scour the bed and banks of the canal Necessity: Velocity in a canal is a function of the slope of the canal.
There is a limit for the velocity, so that the canal bed can neither be scoured nor silted up. Hence there glacus a limiting surface slope in the canal.
ENGINEERING DESIGNS-CANAL STRUCTURES GENERAL DESIGN PRINCIPLES
The slope of the country, where the canal system has to run will naturally be steeper than the surface slope the canal system that has to come up. To bring the velocity with in the permissible velocities, falls or drops are introduced at suitable locations.
Falls are combined with regulators, bridges, and escapes. Trapezoidal Notch falls Required Basic Data: Well type, Cylinder Falls or Well Syphons. Ogee falls with and without raised crest 6.
Meter and non-meter falls Required Basic Data: Site plan with contours showing the flow direction. TPs Particulars, taken up to hard strata or to a minimum depth of 2m below CBL or ground level which ever deeper with soil classification.
Bearing capacity of the foundation strata. Throat width of drop wall, Linear water way Design of Stilling Basin: Invert level of the cistern Length of the basin Level of end sill And other components. Zloping of drop wall. Transition lengths on upstream and downstream. Check for Scour depth Check for exit gradient Check for apron thickness due to uplift. Design of body wall Design of stilling basin Design of wings, returns. It consists wei number of trapezoidal notches constructed in a high crest wall across the channel with a smooth entrance and a flat circular lip projected down stream from each notch to spread out the falling jet.
There would neither be drawdown nor heading up of water, as the channel approaches the fall.
ENGINEERING DESIGNS-CANAL STRUCTURES GENERAL DESIGN PRINCIPLES – ppt video online download
These falls are Simpler, economical and popular. Design — Trapezoidal Notch: The discharge for one notch is computed and the number of notches designed by trial and error method considering full supply discharge and half supply discharge It is a modern fall, a Straight glacis generally with a slope 2: The hydraulic jump occurs on the glacis causing sufficient hydraulic jump.
Suitable up to 60 cumecs and 1. Baffle falls or Inglis falls: These drops are flumed. These drops can be meters. The following are main components: Up stream approach 2. Clear width of the Throat Btnormally down stream bed width. Down stream glacis 4. Down stream expansion 5.
Down stream Energy Dissipation. Sloping glacis if any. The cistern Roughness devices and the deflectors to deflect the high velocities. The object is three fold: Length and depth of cistern are more crucial in this case To provide cushion to destroy the energy of the drop by formation of hydraulic jump.
In a sloping glacis a reverse curve at the lower end to turn the hypercritical jet to horizontal to a horizontal before slopinf impinges against the sub critical flow of the lower channel, thus creating an hydraulic jump.
Thus the invert level of the cistern be kept at 1. The length of cistern be 5Ef2 to 6Ef2 To produce reverse glavis by providing suitable end wall to ensure an impact in the cistern.
Design Of Hydraulic Structures ~ Civil Engineering Study Materials for GATE IES SSC JE PSUs
In case the hydraulic jump occurs on the glacis the energy dissipation will be incomplete and additional roughening devices such eeir friction blocks, end sill, deflectors etc. In this case hydraulic jump does not form, in case high drowning ratio and low falls. Drop height Fluming ratio 1. When there are piers Bt will be reduced as Bt – 0. It is a low weir constructed at the end of cistern, working on ewir principle of horizontal impact for energy dissipation.
The jump is held stable on a horizontal platform by means of baffle wall. To head up water to upstream to form hydraulic jump. To with stand the impact of the high velocity edsign to dissipate the energy. The platform below the baffle wall up to the deflector wall is known as the cistern. It consists of well with pipe or an RCC box at its bottom, carrying water from inlet well to a downstream well or a Cistern.
Down stream well is necessary if the discharge is greater than 0. It is a simple fall broad crested weir with high slopint sill, The nappe impinges into the water cushion below There is no hydraulic jump and the energy dissipation is brought about by the turbulent diffusion, as the high velocity jet enters the deep pool of water down stream.
The discharge is computed using the formula: Streamflow and Runoff The character, amount, and timing of discharge from a basin tells a lot about flow paths within the basin Therefore, important to.
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