Diversion Head works presentation ppt.pptx

dams and hydraulic structures diversion head works

1. Unit – IV b) Diversion Head Works What is Diversion Head Works An irrigation canal takes its supplies from a river or a stream . In order to divert water from the river into canal it is necessary to construct certain works or  structures across the river and at the head of the off taking canal. These works are known as  Diversion   headworks , The canal headworks may be classified into the following two types. Storage headworks Diversion headworks

2. Diversion Head Works Diversion headworks serve to raise the water level in the river and divert the required quantity into the  canal . Function of diversion headworks : They raises the water level in the river so that the commanded area is increased They regulates the supply of water into the canal They controls the entry of silt into the canal They will provide some storage of water for a short period They reduces the fluctuations in the level supply in the river

3. Location of Diversion Headworks :- The river section at the site should be narrow and well-defined. The river should have high, well-defined, inerodible and non-submersible banks so that the cost of river training works is minimum. 3) The canals taking off from the diversion head works should be quit economical and should have a large commanded area. 4 ) There should be suitable arrangement for the diversion of river during construction. 5 ) The site should be such that the weir (or barrage) can be aligned at right angles to the direction of flow in the river. 6 ) There should be suitable locations for the undersluices , head regulator and other components of the diversion headworks 7 ) The diversion headworks should not submerge costly land and property on its upstream . 8) Good foundation should be available at the site. 9 ) The required materials of construction should be available near the site. 10 ) The site should be easily accessible by road or rail. 11 ) The overall cost of the project should be a minimum.

4. Types of diversion headworks Temporary diversion headworks Permanent diversion headworks Temporary diversion headworks Temporary diversion headworks consist of a spur or bund constructed across the river to raise the water level in the river and divert it into the canal. These bunds may be required to be constructed every year after the floods, because they may be damaged by the floods. Permanent diversion headworks Permanent diversion headworks consists of a permanent structure such as weir or barrage constructed across the river to raise the water level in the river and divert it into the canal. Most of the diversion headworks for important canal system in our country are permanent diversion headworks and the same are described in the following sections.

5. Components of diversion headworks :- Weir or Barrage Divide wall or divide groyne Fish ladder Undersluices or scouring sluices Silt excluder Canal head regulator River training works such as Marginal bunds and Guide bunds. Layout of diversion head works

6. Weir A weir is a structure constructed across a river to raise its water level and divert the eater into the canal . Types of Weir Gravity weir Non gravity weir Vertiacl drop weir Rock fill weir Concrete weirs

7. Classification of weirs According to use and function Storage weir Pick up weir Diversion weir Waste weir 2) According to control of surface flow 3) According to the design of floors 4) According to Constructional material

8. Location of Weirs A weir should be located in a stable part of the river where the river is unlikely to change its course. The weir has to be built high enough to fulfill command requirements. During high floods, the river could overtop its embankments and change its course. Therefore, a location with firm, well defined banks should be selected for the construction of the weir. Where possible, the site should have good bed conditions, such as rock outcrops. Alternatively, the weir should be kept as low as possible.

9. Component part of weir :- Weir may be masonry; rockfill or cement concrete. All weirs normally have the following components: Body wall usually with shutters; upstream rough stone or boulder pitching; upstream curtain wall crest shutters downstream curtain wall; downstream apron for channel bed . Shutter.

10. Barrage :- The only difference between a weir and a barrage is of gates, that is the flow in barrage is regulated by gates and that in weirs, by its crest height. Barrages are costlier than  weirs.

11. Component part Barrages :- 1.Upstream stone pitching for bed protection. 2.Upstream sheet pile. 3.Upstream apron. 4. Upstream sloping glacis. 5. Barrage crest. 6. RCC pier with rail/road bridge on top. 7. Gate on the crest between RCC piers. 8.Downstream glacis. 9. Downstream apron. 10. Energy dissipation devices like friction blocks, end sills etc. 11. Downstream and intermediate sheet piles. 12. Downstream stone pitching for bed protection .

12. DISADVANTAGES OF EARTH DAMS

13. Earth dams are further divided into the following types:

14. Earth dams are further divided into the following types: