DESIGN OF AQUEDUCT

BATCH:G.KRISHNA REDDY (11h65a0103)S.GOPINATH REDDY(1oh61ao149)K.RAKESH KUMAR (10h61a0124)M.SHARAN TEJA (10h61a0132)K.SANTHOSH (10h61a0121)

GUIDE:Prof.

G.VENKATESHWARLU

AQUEDUCT

An aqueduct is a cross drainage structure.

Which is constructed to convey water over an obstacle, such as natural streams, valleys etc.

Aqueduct word is derived from Latin which means ‘water’ to lead.

http://www.aboutcivil.org/imajes/aqueduct.jpg

CROSS DRAINAGE WORKS

A cross drainage work is a structure carrying the discharge from a canal across a natural stream intercepting the canal.

Canal comes across obstructions like rivers, natural drains and other canals.

The various types of structures that are built to carry the canal water across the above mentioned obstructions are called cross drainage works.

Cross drainage works are unavoidable in any canal system.

In order to reduce the cross drainage works, the artificial canals are generally aligned along ridge line called watershed.

A cross drainage work is generally a costly construction and must be avoided as far as possible.

However, before the watershed is reached, the canal which takes off from the river has to cross number of drains, which move from the watershed towards river.

The number of cross drainage works may also be reduced by diverting one drain into another and by changing alignment of canal, so that it crosses below the junction of two drains.

WATERSHED LINE

It is an area of land that drains surface and subsurface runoff to a common point usually a stream, river, lake or the ocean.

Every piece of land on earth is a part of watershed because water always moves off of land to a lower point where it collects in a water body.

To use a simpler analogy, a watershed is shaped some what like a bowl that has been cut in half, the rim around the bowl would be like the watershed divide.

Watershed divides are the boundaries that define a watershed and separate adjacent watersheds

Aqueducts have been used for thousands of years to transferWater for long distances for public water supply.

Ancient structures were only open channels, but now a days they Consist of tunnels, canals, siphons or any combination of these.

Types of cross drainage works

Canal over the

drainageCanal

below the drainage

Drain through

the canal

• aqueduct• Siphon

aqueduct

• Super passage

• Canal siphon• Level

crossing• Inlets and

outlets

The canal water is taken across the drain in a trough supported on piers.

The drain water flows under the canal such that there is sufficient headway available between the H.F.L of the drainand underside of the canal trough.

The drain therefore flows at atmospheric pressure under the work.

An inspection road is provided along with trough.

SELECTION OF A SUITABLE TYPE OF CROSS DRAINAGE WORK

The relative bed levels, water levels, and discharge of the canal and the drainage are the primary factors which govern and dictate the type of cross drainage work that may prove to be most suitable at a particular place .

For example, if the bed level of the canal is sufficiently above the H.F.L of the drain, an aqueduct is first and obvious choice.

In actual field, ideal conditions may not be available and the choice depends on other factors, such as

1. Suitable canal alignment.2. Nature of available foundation.3. Position of watertable and availability of

dewatering Equipment.4. Suitability of soil for embankment.5. Permissible head loss in canal.6. Availability of funds.

TYPES OF AQUEDUCTS

Type 1

Type 2

Type 3

How does an aqueduct work?

The water was transported in concrete tunnels. The tunnels were underground if possible. Sometimes the tunnel had to go above ground.  Tunnels could be build with a shaft.  This shaft allowed them to take out dirt and lower supplies to the workers. 

tunnel 

PROPER SITE FOR DRAINGE CROSSING: The site selected for the cross drainage works should have the following main characteristics, 1. It should be such that it requires minimum disturbance regarding the approach and tail reaches of the drainage channel.

2. Suitable foundation soil should be available at reasonable depth.

3. Sufficient headway is available for the super structure of the aqueduct over the H.F.L of the natural stream.

4. Suitable existing topography, geological and hydraulic conditions for the cross drainage works at reasonable costs

LICHFIELD CANAL AQUEDUCT

It was constructed at Birmingham, England.

It was necessary to construct an aqueduct to carry the canal water over the road.

It was constructed over M6 toll motorway.

It is a navigable aqueduct

This aqueduct consist of the centre support and the parts of the 2 abutments located adjacent to the hard shoulders.

DESIGN CONSIDERATIONS

Determination of maximum flood discharge.Fixing of waterway requirements.Afflux and head loss.Fluming of the canal.Design of pucca canal trough.

DETERMINATION OF MAXIMUM FLOOD DISCHARGE

The high flood discharge for smaller drains is worked out by using empirical formulas.

For larger drains ,hydrograph analysis, rational formula etc.., are used.

FIXING OF WATERWAY REQUIREMENTS

An approximate value of required waterway for drain may be obtained by using lacey’s equation

P=4.75sqrtQ

For wide drains, the wetted perimeter may be approximately taken equal to the width of drain and hence, equal to waterway required.

The maximum permissible reduction in waterway from lacey’s perimeter is 20%

SOURCESTextbooks:• Irrigation engineering and hydraulic structures by santosh kumar garg• Irrigation water resources and water power engineering by p.n.modiWeb:• http://www.academicjournals.org• http://www.newyorkcanals.org/• wikipedia

Thank you