TRAINING PROGRAMME ON

1

TRAINING PROGRAMME ON ENGINEERING DESIGNS - CANAL
STRUCTURES GENERAL DESIGN PRINCIPLES
Aqueducts, Canal Syphons Escapes
BY ROUTHU SATYANARAYANACHIEF ENGINEER
(Retired.)FORMER ADVISOR, GOVERNMENT OF A.P
2
Cross Drainage Works-Aqueducts

• 1. Aqueducts
• Classified as type-I, type-II and type-
  III depending up on the arrangement of canal
  passing
• over the Stream/drain,
• Type-I Structures come under this type where the
  canal continuous over the stream with its normal
  earthen section including the banks and earthen
  slopes. The HFL of the stream shall be lower than
  the bottom level of the canal trough.
• Type-II Structures where the canal continues
  over the stream but the outer banks are replaced
  by outer walls.
• Type-III The canal banks will be discontinues
  over the stream and the canal water is carried by
  a masonry or concrete, RC C Box, Pipe of suitable
  section. The Service and inspection Tracks may be
  continuous or discontinues. Generally the canal
  section is flumed and head loss is accounted for.
  
• 2. Viaducts
• Similar to type-III aqueduct except the length of
  the structure is very large compared to the
  stream or there is no stream/drain existing in
  the valleys joining the two sides of the
  structure.
• 3. Syphon Aqueduct
• The HFL of the stream/drain will be lower than
  the under side of (bottom level) the canal trough
  . If the HFL of the stream is above the canal bed
  it is called syphoned.

3
Cross Drainage Works-Aqueducts

• 4. Under tunnel (barrel/ pipe)/ Syphon
  Aqueduct
• Stream discharge carried in the barrel if
  required by depressing stream bed level to make
  the headway below the canal. Canal section
  carried over barrel as it is with head walls to
  replace the outer slopes of canal partially/
  fully. The under tunnel flowing full under
  pressure is called syphon aqueduct.
• 5. Buttress type under tunnel
• Steam discharge carried in the barrel if required
  by depressing the stream bed level to make the
  head way below the canal and canal discharge
  carried in the flumed trough (Trapezoidal or
  rectangular). The abutments and piers raised to
  the bottom of trough in case of Trapezoidal
  shape. For continuity of inspection path, a
  bridge and for non inspection path foot bridge
  will be provided.
• 6. Super passage
• Stream discharge carried in the trough normally
  rectangular shape (1 or more bays) with vertical
  clearance over F.S.L. of canal. For continuity of
  inspection path bridge and for non inspection
  path foot bridge will be provided separately.
• 7. Canal siphon
• Canal discharge carried below the stream by
  depressing the canal bed to make the headway. For
  continuity of inspection path a bridge will be
  provided separately.

4
CD Works Level Crossings

• 8. Level Crossing
• In this type of works the drainage water and
  canal water are allowed to intermingle with each
  other .
• A Level crossing is provided when large canal and
  a huge drain approach at the same level.
• An Inlet and out let for the canal and an escape
  for the drainage or vice versa are provided.
• Perennial drainage discharge can be used in the
  canal supplies.
• 9. Inlets and Out lets
• Provided at exceptional cases.

5
Cross Drainage Works-Aqueducts

• Design Criteria
• Hydrology of the drain or stream.
• Hydraulic design of
• The stream or drain
• The hydraulic deign of the canal
• Structural Design.
• Design of sub structure
• Design of super structure

6
Cross Drainage Works-Aqueducts

• Basic Data
• Site plan with net levels at 10m intervals and
  contours and duly marking the flow direction of
  the canal and the stream.
• Hydraulic particulars of the canal
• LS of the stream covering 500m on u/s and d/s
  with levels at 10m to 20m intervals and CSs at
  centre line and at 10m, 25m, 50m, 100m, 200m,
  300m, 400m, and 500m on /s and d/s sides.
• Levels on the CS to be 3m, to 5m, in the gorge
  portion and 10m, intervals on the flanks up to
  50m beyond HFL mark on the ground.
• Catchment area plan of the seam/drain on the topo
  sheet for Catchment up to 2.5 Sq..m and the CA
  to be traversed on ground for Catchment less than
  2.5 sq..m.
• Computation of Maximum Flood Discharge (MFD) of
  the stream/drain. and the HFL/ MFL are to be
  marked on ghe LS CSs and cross checked with the
  Observed MFLs (OMFL).
• Trial Pit (TP) particulars (Bore logs) taken up
  to hard strata, for a minimum depth of 2m below
  ground level or drain bed level or canal bed
  level for shallow foundations and up o 1.33R
  below maximum scour level on the centre line of
  the structure, (and) at least one on either side
  or as decided as per the filed conditions along
  the centre line and One each on u/s and d/s side.
• Safe bearing capacity of the strata may be
  obtained and furnished.

7
Cross Drainage Works-Aqueducts

• Hydraulic data
• Canal
• Width of road way and class of IRC loading.
• Head loss provided.
• The Stream or drain
• Allowable afflux.
• Nature of bed material and value of n

8
Cross Drainage Works-Aqueducts

• I. Hydrology of the drain
• Computation of maximum flood discharge and the
  MFL
• II. Hydraulic design
• Water way/Vent way
• Vertical Clearance
• Free Board
• Crust Level of the Road way or a Bridge
• Afflux
• Depth of Scour
• Mean Depth of Scour (d)
• Maximum Depth of Scour or Designed Depth of Scour
  (D or R)
• Uplift
• Exit gradient.
• Loss of Head (Energy Loss)
• Joints
• III. Structural Design
• Super structure
• Sub structure

9
Aqueducts - Hydrology

• I. Hydrology of the Drain/Stream
• 1. Compute the designed flood of the stream from
  catchments area plan using any one of the
  empirical formulae or by the flood frequency
  method, SPF, PMF.
• 2. Compute the MFL in the stream by step by step
  method by trial and error and verify with
  observed MFL.
• 3. For drains with discharge gt 150 cumecs and
  canals with discharge gt 30 cumecs detailed study
  is to be conducted in respect of Catchment area
  and computations of HFD/SPF or PMF.

10
Aqueducts - Hydrology

• I. Hydrology of the Drain/Stream
• Formulae for computation of maximum Flood
  Discharge
• _________________________________________________
  ____________
• S.No. Type of Canal Catchment Area (CA) in
  M in Sq. Miles
• ----------------------------------------------
  --------------------------------------------------
  ----------
• Up land Areas Deltaic Tracts
• ------------------------------------------------
  --------------------------------------------------
  --------------------------------------------------
  ----
• 1. Main Canal Dickenss formula, Rye's
  formula
• Q CM 3/4 Q CM 2/3
• C1400 for CAlt1.00 C1000
• C1200 for CA1 to 30 Velocity shall not
  exceed
• 10 ft/sec
• C1060 for CA30 to 500
• --------------------------------------------------
  --------------------------------------------------
  ----------------------------
• Q7000 M1/2 for CAgt500
• Velocity in the barrel up to
• 12 to13 ft/sec
• --------------------------------------------------
  --------------------------------------------------
  ---------------------------

11
CD Works - Aqueducts

• Water way / Vent way and the Lay out
• Design the vent way of the stream/drain limiting
  the velocities in the drain, Keeping in
  view the Laceys wetted perimeter limiting the
  fluming ratio to 60 to 80 and velocitylt3m/s.
• A vent way in Masonry with RCC trough or RCC box
  with height not less than 1200mm (1500mm
  preferred)
• For smaller discharges RCC Hume pipes diameter
  no lt900mm
• Design the tail channel and the approach
  channel
• Drain transactions
• Wings and returns are provided both on u/s and
  d/s side of the stream with splays 21 but not
  flatter than 41 on the u/s and 31 but not
  flatter than 51 both on d/s side.
• Drop wall on the d/s side of the structure may be
  avoided.
• Design/Fix the canal trough limiting the fluming
  ratio not more than 70 and energy losses not
  greater than the values provided in HPs and
  velocity generally not more than 3 to 4m/s.
• Transition lengths both on the u/s and d/s side
  of the canal is fixed.
• Canal transitions 21 and 31 splay but not
  flatter than 41 and 51 on u/s and d/s
  respectively.

12
CD Works - Aqueducts

• Transition walls Transition walls to be
  provided at either ends keying 600mm in to the
  earth banks both for drain and canal.
• Compute the TELs of the canal starting from d/s
  side end of the canal transition up to u/s side
  transition of the canal (Designed canal section
  on either side) and verify that the head loss
  and the velocities are with in the permissible
  limits.
• Finalize the widths of the inspection tracks foot
  paths on either side if required.
• Design the tail channel and the approach channel
  of the stream.
• Compute the TELs in the stream limiting the
  velocities, and permissible afflux etc.
• Draw flow diagrams both for the stream and canal.
• Compute and design foundation levels considering
  scour depths.
• Compute and design the barrel and the floors of
  the stream for uplift pressure.
• Check for exit gradient.
• (cont)

13
CD Works - Aqueducts

• Lay out
• Preferably a straight reach.
• The carrier canal and the drain shall be at right
  angle crossing.
• Proper training works for the drain and suitable
  protection works like turfing, pitching and
  launching aprons etc.,
• Expansion joints, Contraction Joints and
  construction joints.

14
AqueductsHydraulic Design

• II. Hydraulic Design
• Vertical Clearance
• It is the vertical distance between the HFL of
  the stream and the under side of the canal trough
  including afflux.
• S. No. Designed flood in
  Cumecs Minimum Vertical Clearance in mm
• 1. lt
  3 450
• 2 Between 3 and 30
  600
• 3. Between 30 and
  300 900
• 4. Between 300 and 3000
  1200
• 5. 3000 and above
  1500

15
AqueductsHydraulic Design

• Free Board
• It is the vertical distance between the HFL/FSL
  to the top of embankment/TBL in case of stream
  and canal respectively.
• Crust Level of the Road way or a Bridge
• The TBL of the canal or the crust level of the
  road way or the natural ground level which ever
  is higher.
• Afflux
• It should be restricted to the value which should
  not cause serious bed scours or submergence.
• It is the rise in water level on the upstream due
  to an obstruction to the flow of drain or canal.
• It is computed using the Rational formula,
  Orifice formula or Empirical formula
• It is the vertical distance measured from HFL or
  FSL to the underside of trough, including afflux.

16
Aqueducts Hydraulic Design

• Scour
• Mean Scour Depth
• Mean scour depth is the depth (d) below HFL or
  FSL in m
• d 1.34q2 /f1/3
• Where, q Discharge per meter width with or
  without concentration of flow in cumecs, f
  Layces silt factor expressed as f 1.76 (d m
  )1/2
• dm average grain size
• Designed Scour Depth (Dor R)
• Straight reaches for individual foundations
  without floor protection
• In the vicinity of pier 2.00 d
• Near abutments 1.27 d approaches retained
• 2.00 d scour all round
• For floor protection works, for raft foundations
  and shallow foundations
• In straight reaches 1.27 d
• At moderate bends 1.50 d

17
Aqueducts Hydraulic Design

• At sever bends 1.75 d m
• At right angle bends 2.00 d
• Structures and earth work connections
• Uplift
• Uplift under floor of the barrels and under the
  u/s and d/s side floors caused by the seepage
  flow from the canal when it is running full and
  the drain is dry or vise versa may be accounted
  for the design using the Khoslas theory and the
  thickness checked for adequacy.
• Cut off walls may be provided on either ends.
• For reducing the uplift and exit gradient pucca
  floor should be provided for in the canal bed in
  adequate length u/s and d/s side with cut off
  walls at the ends.
• Exit gradient.
• The rigid structure and the flexible earth work
  shall be properly connected and checked for exit
  gradient (GE).
• GE H/d1/ (??) 1/2

18
Aqueducts Hydraulic Design

• Loss of Head (Energy Loss)
• The losses are at inlets (h1) and outlets (h2),
  at bends elbows (h3), losses due to transitions
  (h4) and losses due to skin friction (h5). The
  sum of losses (H) shall be sum of all the losses
• H h1 h2 h3 h4h5
• Joints
• Bell Mouth on U/S side
• Cut and ease waters
• Water Stops
• Bearings
• Miscellaneous works

19
Aqueducts Structural Design

• III. Structural Design
• Design Loads
• Dead Loads
• Live Loads
• Impact and Dynamic Loads
• Water Load
• Braking force
• Wind Load
• Water currents
• Centrifugal forces
• Buoyancy
• Earth pressures
• Temperature Forces
• Erection Loads.
• Seismic Loads.
• Water Pressure.

20
AqueductsStructural Design

• III. Structural Design
• Combination of Loads
• a. Canal empty and drain at low water - normal
  condition with without earth quake
• b. Canal at FSL and drain at low water - normal
  condition with without earth quake
• c. Canal empty and drain at HFL -
  normal condition without earth quake
• d. Canal at FSL and drain at HFL -
  normal condition without earth quake
• e. Construction condition without earth quake
• 1. Piers constructed without super structure and
  drain at HFL
• 2. Super structure is constructed on one side of
  pier and the drain at HFL
• Wind load should not be considered
  simultaneously with earthquake.
• The effect of earth quake force in all directions
  that is Longitudinal (L), Transverse (T), and
  Vertical (V) shall be taken into with combination
  TV or LV. 5.05.

21
Aqueducts Structural Design

• III. Structural Design
• Super Structure
• Design of RCC Slab under canal and under earth
  bank or an RCC Box
• Inspection Track To be designed for Single lane
  IRC class A Loading and Foot bridge normally
  1.5m wide on non-inspection track.
• In case of RCC box, the road way is carried over
  the box with proper entry and exit on either
  ends.
• Sub Structure.
• Design of piers under canal trough and earth bank
  or inspection track
• Design of abutments under canal trough, and
  earth banks or inspection track , by adopting TVA
  procedure, Coulombs or Rankin's theory.
• Design of abutments under service road / walk way
• Design of all retaining walls, such as returns,
  wing walls, side walls for the drain and canal
  both on the u/s and d/s side, by adopting TVA
  procedure Coulombs theory or Rankins theory.

22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
CD Works Structural Design

• Design Loads
• 1. Dead Loads 2. Live Loads 3. Impact and
  Dynamic Loads
• 4. Water Load 5.Braking force 6. Wind Load
• 7. Water currents 8. Centrifugal forces 9.
  Buoyancy
• 10. Earth pressures 11.Temperature Forces 12.
  Erection Loads.
• 13. Seismic Loads. 14. Water Pressure.
• Combination of Loads
• a. Canal empty and drain at low water - normal
  condition with without earth quake
• b. Canal at FSL and drain at low water -
  normal condition with without earth quake
• c. Canal empty and drain at HFL -
  normal condition without earth quake
• d. Canal at FSL and drain at HFL -
  normal condition without earth quake
• e. Construction condition without earth quake
• 1. Piers constructed without super structure and
  drain at HFL
• 2. Super structure is constructed on one side of
  pier and the drain at HFL

26
(No Transcript)
27
CD Works Structural Design

• Design Loads
• 1. Dead Loads 2. Live Loads 3. Impact and
  Dynamic Loads
• 4. Water Load 5.Braking force 6. Wind Load
• 7. Water currents 8. Centrifugal forces 9.
  Buoyancy
• 10. Earth pressures 11.Temperature Forces 12.
  Erection Loads.
• 13. Seismic Loads. 14. Water Pressure.
• Combination of Loads
• a. Canal empty and drain at low water - normal
  condition with without earth quake
• b. Canal at FSL and drain at low water -
  normal condition with without earth quake
• c. Canal empty and drain at HFL -
  normal condition without earth quake
• d. Canal at FSL and drain at HFL -
  normal condition without earth quake
• e. Construction condition without earth quake
• 1. Piers constructed without super structure and
  drain at HFL
• 2. Super structure is constructed on one side of
  pier and the drain at HFL

28
CD Works Canal Syphon

• Definition
• Structure, where the drain is taken over the
  canal such that the canal water runs below the
  drain either freely or under syphonic action
• When the FSL of the canal is below the under side
  of the drainage trough and canal water flows
  freely under gravity, the structure is known as
  Superpasage.
• When the canal FSL is below the under side of the
  drainage trough, so that the canal flows under
  syphonic action under the trough, the structure
  is known as Canal Syphon or a Syphon.
• Canal may be flumed for economy, subject to the
  availability of head loss in the HPs
• The drainage trough should not be flumed.
• Inspection Track can not be provided along the
  canal.
• A separate bridge/Causeway will be provided for
  inspection track.

29
Cross Drainage Works-Syphon

• Hydrology of the drain
• Computation of maximum flood discharge and the
  MFL
• Hydraulic design
• 1. Water way/Vent way
• 2. Vertical Clearance
• 3. Free Board
• 4. Crust Level of the Road way or a Bridge
• 5. Afflux
• 6. Depth of Scour
• Mean Depth of Scour (d)
• Maximum Depth of Scour or Designed Depth of Scour
  (D or R)
• 7.Uplift
• 8. Exit gradient.
• 9. Loss of Head (Energy Loss)
• 10. Joints
• Structural Design
• Super structure
• Sub structure

30
CD Works Canal Syphon

• Lay out
• Shape can be circular or rectangular.
• RCC barrel, pre cast RCC pipes, or masonry etc.,
• Syphon barrel
• Horizontal under deep bed portion with slope not
  steeper than 1 in 3 at entry and 1 in 5 at the
  exit end.
• The invert level at the entry normally be kept at
  bed level.
• The invert level at the exit end be little lower
  taking into account the loss of head.
• Transition walls with splay 31 and 41 at the
  entry and exit end.
• Stop log groove
• Trash Rack
• Miscellaneous items/works

31
CD Works Level Crossings

• Level Crossing
• Definition
• It is CD work admitting the drainage water in to
  the canal.
• In this type of works the drainage water and
  canal water are allowed to intermingle with each
  other .
• A Level crossing is provided when large canal and
  a huge drain approach at the same level.
• An Inlet and out let for the canal and an escape
  for the drainage or vice versa are provided.
• Perennial drainage discharge can be used in the
  canal supplies.
• Lay out
• Combination of all or any one of them
• Canal inlet regulator
• Drainage inlet regulator
• Canal outlet regulator
• Drainage outlet regulator

32
Cross Drainage Works- Inlets Outlets

• Inlets and outlets
• Definition
• A canal inlet is constructed when the cross
  drainage flow is small and its water may be
  absorbed into canal without causing appreciable
  rise.
• Inlets are provided in exceptional cases only.
• When the drain discharge is very negligible and
  less than 5, an inlet is provided.
• An out let or an escape shall be provided, when
  the total inlet discharge exceeds more than 15
  of the canal discharge.
• In drought prone areas or zones of scanty rain
  fall or the tail end command, the drainage water
  can be supplemented.

33
Cross Drainage Works- Escapes

• Escapes Escape Regulators See under
  controlled structures
• Escapes are safety valves for the canal system,
  provided to escape surplus water or excess water
  from the canal.
• Though the canals are regulated, excess rise in
  water level may take place at a point on the
  canal down stream as a result of entry of storm
  water, or sudden reduction in demand or closure
  of out lets down stream, or faulty water
  regulation may cause breaches, out flanking or
  dangerous leaks in the canals banks.
• Similar situation may happen in the lift
  irrigation system, when the pumping mains on the
  down stream fail suddenly.
• Hence surplus escapes are provided
• 1 To control the water levels in such situations
  and avoid damages to the system.
• 2. To empty the canal system for repair and
  maintenance.
• 3. As scouring sluices at the head reaches.

34
THANK YOU