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presentation : cross drainage work

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Cross drainage work-Irrigation engineering

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presentation : cross drainage work

  1. 1. Bhagwan Mahavir College of Engineering and Technology PRESENTATION ON
  2. 2. Prepared by : Ankit Gangani : 140060106055
  3. 3. OUTLINE  Introduction  Necessity of CDWs  Types of CDWs  Classification of Aqueducts & Siphon Aqueducts Selection of type of CDWs Selection Of Site How to avoid CDWs Reference
  4. 4. Introduction
  5. 5. WHAT IS CROOS DRAINAGE WORK…  when the network of main canals, branch canals, distributaries, etc.. are provided, then these canals may have to cross the natural drainages like rivers, streams, nallahs, etc. at different points.The crossing of the canals with such obstacle cannot be avoided. So, suitable structures is constructed at the crossing point for the easy flow of water of the canal and drainage in the respective directions. These structures are known as cross-drainage works.
  6. 6.  Irrigational Canals while carrying water have to cross few natural drainage streams, rivers, etc.. To cross those drainages safely by the canals, some suitable structures are required to construct. Works required to construct, to cross the drainage are called Cross Drainage Works (CDWs). At the meeting point of canals and drainages, bed levels may not be same. Depending on their bed levels, different structures are constructed and accordingly they are known by different names. WHAT IS CROSS DRAINAGE WORK..
  7. 7. NECESSITY OF CDWs
  8. 8. TYEPS OF CDWs (1) Type I (Irrigation canal passes over the drainage) (a) Aqueduct, (b) Siphon aqueduct. (2) Type II (Drainage passes over the irrigation canal) (a) Super passage, (b) Siphon super passage. (3) Type III (Drainage and canal intersection each other of the same level) (a) Level Crossing, (b) Inlet and outlet.
  9. 9.  Aqueduct The hydraulic structure in which the irrigation canal is taken over the drainage (such as river, stream etc..) is known as aqueduct. This structure is suitable when bed level of canal is above the highest flood level of drainage. In this case, the drainage water passes clearly below the canal.
  10. 10.  Siphon Aqueduct In a hydraulic structure where the canal is taken over the drainage, but the drainage water cannot pass clearly below the canal. It flows under siphonic action. So, it is known as siphon aqueduct. This structure is suitable when the bed level of canal is below the highest flood level.
  11. 11.  Super Passage The hydraulic structure in which the drainage is taken over the irrigation canal is known as super passage. The structure is suitable when the bed level of drainage is above the full supply level of the canal. The water of the canal passes clearly below the drainage.
  12. 12.  Siphon Super Passage The hydraulic structure in which the drainage is taken over the irrigation canal, but the canal water passes below the drainage under siphonic action is known as siphon super passage. This structure is suitable when the bed level of drainage is below the full supply level of the canal.
  13. 13.  Level Crossings When the bed level of canal and the stream are approximately the same and quality of water in canal and stream is not much different, the cross drainage work constructed is called level crossing where water of canal and stream is allowed to mix. With the help of regulators both in canal and stream, water is disposed through canal and stream in required quantity. Level crossing consists of following components (i) crest wall (ii) Stream regulator (iii) Canal regulator.
  14. 14.  Inlet and Outlet When irrigation canal meets a small stream or drain at same level, drain is allowed to enter the canal as in inlet. At some distance from this inlet point, a part of water is allowed to drain as outlet which eventually meets the original stream. Stone pitching is required at the inlet and outlet. The bed and banks between inlet and outlet are also protected by stone pitching. This type of CDW is called Inlet and Outlet.
  15. 15. Classification of Aqueducts & Siphon Aqueducts  Depending upon the nature of the sides of the aqueduct or siphon aqueduct it may be classified under three headings:  Type I:Sides of the aqueduct in earthen banks with complete earthen slopes. The length of culvert should be sufficient to accommodate both, water section of canal, as well as earthen banks of canal with aqueduct slope.
  16. 16. Classification of Aqueducts & Siphon Aqueducts  Type II : Sides of the aqueduct in earthen banks, with other slopes supported by masonry wall. In this case, canal continues in its earthen section over the drainage but the outer slopes of the canal banks are replaced by retaining wall, reducing the length of drainage culvert.
  17. 17. Classification of Aqueducts & Siphon Aqueducts  Type III:  Sides of the aqueduct made of concrete or masonry. Its earthen section of the canal is discontinued and canal water is carried in masonry or concrete trough, canal is generally flumed in this section.
  18. 18. SELECTION OF TYPES OF CDWs  Relative Bed Level According to the relative bed levels of the canal and the river or drainage, the type of cross drainage work are generally selected which has been discussed earlier.  The following points should be remembered while recommending the type of work, (a) The crossing should be at right angle to each other, (b) Well defined cross-section of the river or drainage should be available. (c) At the crossing point the drainage should be straight for a considerable length. (d) The width of the drainage should be narrow as far as possible.
  19. 19. Availability of Suitable Foundation  For the construction of cross drainage works suitable foundation is required. By boring test, if suitable foundation is not available, then the type of cross drainage work should be selected to site Condition.
  20. 20. Economic Consideration  The cost of construction of cross drainage works should be justified with respect to the project cost and overall benefits of the project. So, the type of works should be selected considering the economical point of view.
  21. 21. Discharge of the drainage Practically the discharge of the drainage is very uncertain in rainy season. So, the structure should be carefully selected so that it may not be destroyed due to unexpected heavy discharge of the river or drainage.
  22. 22. Construction Problems  Different types of constructional problems may arise at the site such as sub soil water, construction materials, communication, availability of land etc. So the type of works should be selected according to the site condition.  water , water table  Earthwork  Materials  Weather  Land acquisition
  23. 23. Selection of Site  1. At the site, the drainage should cross the canal alignment at right angles. Such a site provides good flow conditions and also the cost of the structure is usually a minimum.  2. The stream at the site should be stable and should have stable banks.  3. For economical design and construction of foundations, a firm and strong sub-stratum should exit below the bed of the drainage at a reasonable depth.
  24. 24. Selection of Site  4. The site should be such that long and high approaches of the canal are not required.5. The length and height of the marginal banks and guide banks for the drainage should be small.  6. In the case of an aqueduct, sufficient headway should be available between the canal trough and the high flood level of the drainage.  7. The water table at the site should not be high, because it will create dewatering problems for laying foundations.
  25. 25. Selection of Site  8. As far as possible, the site should be selected d/s of the confluence of two streams, thereby avoiding the necessity of construction of two cross-drainage works.  9. The possibility of diverting one stream into another stream upstream of the canal crossing should also be considered and adopted, if found feasible and economical.  10. A cross-drainage work should be combined with a bridge, if required. If necessary, the bridge site can be shifted to the cross-drainage work or vice versa. The cost of the combined structure is usually less. Moreover, the marginal banks and guide banks required for the river training can be used as the approaches for the village roads.
  26. 26. How to avoid CDW  Change the alignment of canals  Diverting small drainage into large drainage.
  27. 27. Reference  http://uap-bd.edu/ce/Handouts/CE-461/Doc/Chapter-9.pdf  https://theconstructor.org/water-resources/cross-drainage-works-types/12051/  http://www.idc- online.com/technical_references/pdfs/civil_engineering/Cross_Drainage_Works.pdf  http://www.aboutcivil.org/cross-drainage-works.html  http://nptel.ac.in/courses/105106114/pdfs/Unit1/1_3.pdf  http://civilpddc2013.weebly.com/uploads/2/2/5/5/22556782/14_- _cross_drainage_works.pdf  Irrigation Engineering by Dr. R P Rethaliya
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Cross drainage work-Irrigation engineering

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