Diese Präsentation wurde erfolgreich gemeldet.
Die SlideShare-Präsentation wird heruntergeladen. ×

LAND DRAINAGE- CLASSIFICATIONS, STEADY AND UNSTEADY STATE EQUATIONS

Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Nächste SlideShare
Drainage system
Drainage system
Wird geladen in …3
×

Hier ansehen

1 von 38 Anzeige
Anzeige

Weitere Verwandte Inhalte

Diashows für Sie (20)

Andere mochten auch (17)

Anzeige

Ähnlich wie LAND DRAINAGE- CLASSIFICATIONS, STEADY AND UNSTEADY STATE EQUATIONS (20)

Anzeige

Aktuellste (20)

LAND DRAINAGE- CLASSIFICATIONS, STEADY AND UNSTEADY STATE EQUATIONS

  1. 1. WELCOME NAMITHA M R ID. No: 2015664502 M.Tech. Land and Water Management Engineering TNAU
  2. 2. LAND DRAINAGE- CLASSIFICATIONS , STEADY AND UNSTEADY STATE EQUATIONS
  3. 3. CLASSIFICATION OF DRAINS DRAINS ACCORDING TO CONSTRUCTION NATURAL ARTIFICIAL ACCORDING TO FUNCTION OPEN SURFACE SEEPAGE SURFACE- CUM-SEEPAGE CLOSED/SUB- SURFACE TILE DRAINS MOLE DRAINS VERTICAL
  4. 4. A. ACCORDING TO CONSTRUCTION a) Natural drains:  Lowest valley line between 2 ridges  Naturally occurring  Eg: Drainage lines, Nallahs etc. b) Artificial drains:  Man made structures  Constructed along drainage line
  5. 5. NATURAL DRAIN ARTIFICIAL DRAIN
  6. 6. B. ACCORDING TO FUNCTION a) Open drains b) Closed/ Sub-surface drains c) Vertical drains
  7. 7. a) Open drains  1-1.5m deep  Caters the storm water  Lowers water table  Reduces sloughing of sides  Removes large quantities of surface as well as sub-surface water
  8. 8. OPEN DRAIN
  9. 9.  Open drains are of three types: Surface drains Seepage drains Surface-cum-seepage drains
  10. 10.  Surface drains:  Storm water drains  Dispose off surplus rain water and irrigation water
  11. 11.  Seepage drains:  Drain out the seepage water from the subsurface layer  Depth upto groundwater level
  12. 12.  Surface-cum-seepage drains: Serves dual purpose of seepage and storm water drain
  13. 13. b) Subsurface drains/ Closed drains  Drains laid deep in the ground and then covered  Used to lower the capillary surface and water table below ground  Provides aeration in the root zone  Two types: Tile drains and Mole drains
  14. 14.  Tile drains:  Most efficient and permanent drains  Short length pipes called tiles are laid with a grade  1-1.5m below ground surface  Tiles:- Concrete or Burnt clay  Pipes are held end to end without joining
  15. 15.  Mole drains:  Cylindrical channels below ground surface  Formed at desired depth with a grade  No lining material  Clay soils are suitable  Constructed using mole ploughs
  16. 16. Depth: 45-120 cm below ground Diameter: 7.5-15 cm Life span-10-15 yrs
  17. 17. c) Vertical Drains  Water table is controlled by pumping from a network of wells  Number of pumping points over a small area provides lasting effect of pumping in ground water decline
  18. 18. d) Bio drainage  Drainage effect produced by certain plants  Eg: Eucalyptus  Caused by withdrawal of high rate of water
  19. 19. STEADY STATE DRAINAGE EQUATIONS a) Hooghout’s equation Assumptions:- 1. Soil profile is homogeneous 2. dy/dx=i 3.Darcy’s law is valid Dupuit- Forchcheimer assumptions
  20. 20. 4. Drains are spaced evenly 5. An impermeable layer underlain the drain 6. Origin of co-ordinates is on the impermeable layer below the centre of one drain 7. Rate of replenishment of water table by irrigation rainfall is ‘R’
  21. 21. Hooghout’s equation for drain spacing:- S2 = 4K/R [H2-2hd+2Hd-h2] where, d- Depth to the impermeable layer from the drain bottom h- Height of water in the drain H-Height of water in midway between 2 drains
  22. 22. S- Drain spacing D-Distance from the impermeable layer to the maximum height of water between the drains K- Hydraulic conductivity R- Replenishment rate
  23. 23.  When drain is considered as empty:- S2 = 4KH/R [H+2d] {h= 0}  This equation is similar to ellipse equation – Luthin(1973)  Luthin has transformed the origin of coordinate system to the midpoint between the drains
  24. 24.  Ellipse equation:- y2/ (RS2/ 4K) + x2/ (S2/4) = 1 where, S/2 is the semi-major axis and S/2 √(R/K) is the semi-minor axis
  25. 25.  Hooghout’s equivalent depth:-  Hooghout’s equation considers totally horizontal movement of water towards the drains  But, when ‘d’ increases beyond a certain level, horizontal flow transforms into vertical flow
  26. 26.  This limits the application of Hooghout’s equation  Equivalent depth: Depth below the drain level which can transform the radial flow component into an equivalent horizontal flow component
  27. 27.  Equivalent depth, d’ = S/8F where, S- Spacing between drains F-Equivalence factor  In original Hooghout’s equation, d is replaced by d’
  28. 28. b) Earnst equation  Applicable to 2-layered soil  Advantage over Hooghout’s equation: The interspace between 2 drains can be either above or below the drain
  29. 29.  Earnst equation:- Total available head, h = hv + hh + hr where, hv = Head due to vertical flow hh = Head due to vertical flow hr = Head due to radial flow
  30. 30.  Vertical head, hv = qDv / Kv where, q - Discharge per unit area Dv -Thickness of the layer through which vertical flow is considered Kv - Vertical Hydraulic Conductivity
  31. 31.  Horizontal head, hh = L2q / 8KhDh where, Kh – Horizontal Hydraulic Conductivity Dh - Thickness of layer through which horizontal flow is considered L - Spacing
  32. 32.  Radial Head:- hr = (qL / πKr) ln(Dr /u) where, Kr – Radial Hydraulic Conductivity a - Geometric Factor u- Wetted Perimeter of the drain Dr – Thickness of the layer in which radial flow is considered
  33. 33. i.e, Total Head, h = [qDv / Kv]+[L2q / 8KhDh]+[(qL / πKr) ln(aDr /u)]  This is the Earnst equation in complete form
  34. 34. UNSTEADY STATE DRAINAGE EQUATIONS a) Glover Dumn equation  Assumptions:  Flow pattern is unsteady  Darcy’s law is applicable  All velocity vectors are horizontal , v = -K dy/dx  The vertical column of water bounded above by the phreatic surface and below by an impermeable layer
  35. 35.  Glover-Dumn equation is used to describe a falling water table after its sudden rise due to an instantaneous recharge
  36. 36. Drain spacing = π (Kdt /µ)½ (ln 1.16(h0 / ht))-½ where, d-Equivalent depth of soil layer below the drain level K- Hydraulic Conductivity L- Drain spacing t- Time after instantaneous rise of water table µ- Drainage porosity h0 - Initial height of water table ht – Height of water table at t=t
  37. 37. THANK YOU !!!

×