Design of Syphon Aqueduct
AQUEDUCT
Chapter 1: Introduction 

Chapter 2: Hydraulic Particulars 
11 
Chapter 3: Selection of type of aqueduct 
12 
Chapter 4: Design of canal trough 
13 
Chapter 5: Design of drainage water way 

Chapter 6: Check for loss of head in the canal due to 

Fluming of canal water way through the 

Trough 

Chapter 7: Fixing of M.F.L of drainage 

Chapter 8: Design of side walls of canal trough 

Chapter 9: Design of bottom slab of canal trough 

Chapter 10: Design of tail channel 

Chapter 11: Design of canal transitions 

Chapter 12: Design of abutments 

Chapter 13: Design of piers 

Chapter 14: Design of wing walls 

Chapter 15: Design of return walls 

Chapter 16: Design of canal aprons 
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Design of Syphon Aqueduct 

Chapter 17: Checking the depth of foundation of 
53 
Drainage returns by scour depth 

Chapter 18: Design of inspection track 
54 
Chapter 19: Design of pier cap 

Chapter 20: Design of pile foundation 
59 
Chapter 21: Design of foundation of abutment and piers 

Chapter 22: Design of anchorage arrangements 
62 
Chapter 23: Drawings 
63 
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Design of Syphon Aqueduct
Chapter 1
Introduction
Cross Drainage Works
Definition:
A cross drainage work is a structure carrying the discharge from a natural stream across a canal intercepting the stream.
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 or vice versa are called cross drainage works.
It is generally a very costly item and should be avoided by
ï‚§Diverting one stream into another.
ï‚§Changing the alignment of the canal so that it crosses below the junction of two streams.
Types of cross drainage works
Depending upon levels and discharge, it may be of the following types:
(a) Cross drainage works carrying canal across the drainage:
the structures that fall under this type are:
1.An Aqueduct
2.Siphon Aqueduct
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Design of Syphon Aqueduct
Aqueduct:
When the HFL of the drain is sufficiently below the bottom of the canal such that the drainage water flows freely under gravity, the structures known as Aqueduct. An aqueduct is a water supply or navigable channel constructed to convey water. In modern engineering, the term is used for any system of pipes, ditches, canals, tunnels, and other structures used for this purpose. In a more restricted use, aqueduct (occasionally water bridge) applies to any bridge or viaduct that transports water instead of a path, road or railway across a gap. Large navigable aqueducts are used as transport links for boats or ships. Aqueducts must span a crossing at the same level as the watercourses on each end. The word is derived from the Latinaqua ("water") and ducere ("to lead").
ï‚§In this, canal water is carried across the drainage in a trough supported on piers.
ï‚§Bridge carrying water
ï‚§Provided when sufficient level difference is available between the canal and natural and canal bed is sufficiently higher than HFL.
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Design of Syphon Aqueduct
Classification of aqueduct and siphon aqueduct:
ïƒ˜Depending upon the nature of the sides of the aqueduct or siphon aqueduct it may be classified under three headings:
Type I:
ïƒ˜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.
ïƒ˜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.
Type II:
ïƒ˜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.
Siphon Aqueduct:
In case of the siphon Aqueduct, the HFL of the drain is much higher above the canal bed, and water runs under siphonic action through the Aqueduct barrels.
The drain bed is generally depressed and provided with pucci floors, on the upstream side, the drainage bed may be joined to the pucca floor either by a vertical drop or by glacis of 3:1. The downstrean rising slope should not be steeper than 5:1. When the canal is passed over the drain, the canal remains open for inspection throughout and the damage caused by flood is rare. However during heavy floods, the foundations are succeptible to scour or the waterway of drain may get choked due to debris, tress etc.
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Design of Syphon Aqueduct
The structures that fall under this type are:
ï‚§Super passage
ï‚§Canal siphon or called syphon only.
Super passage:
ï‚§The hydraulic structure in which the drainage is passing over the irrigation canal is known as super passage. This structure is suitable when the bed level of drainage is above the flood surface level of the canal. The water of the canal passes clearly below the drainage
ï‚§A super passage is similar to an aqueduct, except in this case the drain is over the canal.
ï‚§The FSL of the canal is lower than the underside of the trough carrying drainage water. Thus, the canal water runs under the gravity.
ï‚§Reverse of an aqueduct
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Design of Syphon Aqueduct
Canal Syphon:
ï‚§If two canals cross each other and one of the canals is siphoned under the other, then the hydraulic structure at crossing is called â€œcanal siphonâ€. For example, lower Jhelum canal
is siphoned under the
ï‚§In case of siphon the FSL of the canal is much above the bed level of the drainage trough, so that the canal runs under the siphonic action.
ï‚§The canal bed is lowered and a ramp is provided at the exit so that the trouble of silting is minimized.
ï‚§Reverse of an aqueduct siphon
ï‚§In the above two types, the inspection road cannot be provided along the canal and a separate bridge is required for roadway. For economy, the canal may be flumed but the drainage trough is never flumed.
Selection of suitable site for cross drainage works:
The factors which affect the selection of suitable type of cross drainage works are:
ïƒ˜Relative bed levels and water levels of canal and drainage
ïƒ˜Size of the canal and drainage.
ïƒ˜The following considerations are important
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Design of Syphon Aqueduct
ïƒ˜When the bed level of the canal is much above the HFL of the drainage, an aqueduct is the obvious choice.
ïƒ˜When the bed level of the drain is well above FSL of canal, super passage is provided.
ïƒ˜The necessary headway between the canal bed level and the drainage HFL can be increased by shifting the crossing to the downstream of drainage. If, however, it is not possible to change the canal alignment, a siphon aqueduct may be provided.
ïƒ˜When canal bed level is much lower, but the FSL of canal is higher than the bed level of drainage, a canal siphon is preferred.
ïƒ˜When the drainage and canal cross each other practically at same level, a level crossing may be preferred. This type of work is avoided as far as possible.
Factors which influence the choice / Selection of Cross Drainage Works
1.The considerations which govern the choice between aqueduct and siphon aqueduct are:
2.Suitable canal alignment
3.Suitable soil available for bank connections
4.Nature of available foundations
5.Permissible head loss in canal
6.Availibility of funds
Compared to an aqueduct a super passage is inferior and should be avoided whenever possible. Siphon aqueduct is preferred over siphon unless large drop in drainage bed is required.
Uses:
Historically, agricultural societies have constructed aqueducts to irrigate crops. Archimedes invented the water screw to raise water for use in irrigation of croplands.
Another use for aqueducts is to supply large cities with drinking water. Some of the Roman aqueducts still supply water to Rome today. In California, United States, three large aqueducts
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Design of Syphon Aqueduct
supply water over hundreds of miles to the Los Angeles area. Two are from the Owens River area and a third is from the Colorado River.
In more recent times, aqueducts were used for transportation purposes to allow canalbarges to cross ravines or valleys. During the Industrial Revolution of the 18th century, aqueducts were constructed as part of the boom in
In modern civil engineering projects, detailed study and analysis of open channel flow is commonly required to support flood control, irrigation systems, and large water supply systems when an aqueduct rather than a pipeline is the preferred solution.
In the past, aqueducts often had channels made of earth or other porous materials but significant amounts of water are lost through such unlined aqueducts. As water gets increasingly scarce, these canals are being lined with concrete, polymers or impermeable soil. In some cases, a new aqueduct is built alongside the old one because it cannot be shut down during construction.
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Design of Syphon Aqueduct
DESIGN STEPS:
1)Hydraulic particulars of canal & Drainage
2)Selection of type of aqueduct
3)Design of canal trough
4)Design of drainage water way
5)Check for loss of head in the canal due to fluming of canal water way Through the trough
6)Fixing the M.F.L of the drainage
7)Design of side walls of canal trough
8)Design of bottom slab of canal trough
9)Design of tail channel
10)Design of canal transitions
11)Design of abutments
12)Design of piers
13)Design of wing walls
14)Design of return walls
15)Design of aprons
16)Checking the depth of foundations of drainage returns by scour depth
17)Design of inspection track
18)Design of pier cap
19)Reinforcement in pier
20)Pier foundation
21)Design of pier foundation
22)Design of foundations of abutments and piers
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Design of Syphon Aqueduct
11
Design of Syphon Aqueduct
Selection of type of aqueduct
The above data of hydraulic particulars, a
So, whenever an aqueduct are to be actually constructed, comparative costs are to be worked out for a
In the case of a
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Design of Syphon Aqueduct

Chapter  4 

Design of canal trough 
Discharge, Q 
= 35 m3/s 
Average velocity 
= 0.83 m3/s 
Design velocity = 2% average velocity = 2*0.83=1.66 m/s 

But the maximum design velocity = 1.5 m/s 

Adopt design velocity 
= 1.5 m/s 
Q= A x v 

35= Ax1.5
A=23.3 m2
Depth of flow, y= F.S.D= F.S.L â€“ B.L=
Bottom level = Ultimate bed level of canal = 39.75
Top level = Ultimate F.S.L + 0.5 = 42.50 + 0.50 = 43.00
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Design of Syphon Aqueduct
Chapter  5
Design of drainage water way
Let us provide 3 vents of 2.5 m wide length of water way, l=3X2.50=7.5 m
Sill level of canal trough 
= 39.75 m (given) 

Thickness of bottom slab 
= 250 mm (assume) 

Thickness of wearing coat = 80 mm (assume) 

Bottom level of the canal trough = sill level thickness of wearing coat 



Thickness of bottom slab 


= 
Bottom level of slab 

= 
Average bed level of the drain 
= 38.00 
Since the M.F.L of the drain = ultimate bed level of the canal
Let us adopt depressed bed level of the drain = 37.00
Depth of water = y1 = Bottom level of the canal trough slab depressed B.L Of
Let the design velocity in the drain, V1= 3.25 m/s (assume)
Discharge in the drain, Q1 = 60 m3/s
Q1=A1 X V1, 60= A1 X 3.25
A1=18.46 m2
A1=L X y1
18.46 = L X 2.45 L = 7.54 m
Length of barrel = B+ 2X (thickness of side wall) = 12 + 2X (0.3) =12.60 m
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Design of Syphon Aqueduct
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Design of Syphon Aqueduct
Chapter  6
Check for loss of head in the canal due to fluming of canal water way through the trough
In a
However, in case of a
In aqueduct of short lengths, by limiting the velocity to twice the norm al canal velocity, the loss of head may be very s mall or almost negligible and hence it is gener ally ignored. The assumption is that the upstream water surface will in course of time assume a flatter slope to the extent required to drive the flow through the trough with that bit of extra velocity.
However, in large and longer a queducts it is not so. In order to economies in cost of the canal trough, we may be forced to increase the velocity through the trough. In addition, the length of the trough is an additional fact or. These two factors combine to indicate a significant loss of head, which will have to be p rovided for, while formulating the canal hydraulic particulars. Structures constructed ignoring this aspect will not function properly.
In the present case, to illustrate this aspect, the loss of head in the canal is comp uted.
Consider section 

Canal bed level 
= + 40.00 
Full supply level 
= +42.00 
Average velocity, V1 = 0 .83 m/s 

Velocity head 
= V12/2g = 0.832/2x9.81 = 0.037 m 
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Design of Syphon Aqueduct
Total energy line at
Consider section 

Canal width 
= 20 m 
Depth of water, y 
=F.S.L Bed level = 42.00 â€“ 40.00 = 2.00 
At
Discharge, Q = 35 m3/s
Velocity of flow, V2 = Q/a = 35/40 = 0.87 m/s
Head loss from
Head loss =
=
=0.004
On the U/S end the transition is abrupt and not smooth. So the entire eddy
Loss is taken in to consideration.
The T.E.L at
Section at the entrance of trough
Width of the canal 

= 12 m (assume) 

Depth of canal, y 
= 2 m 

A3 
= 12x2 = 24 m2 

Velocity, V3 = 
3 
=2435 
= 1.46 m/s 
There is a gradual change in c/s from
Head loss = 0.25 x ( V32 V22)/2g = 0.25 x
T.E.L at
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Design of Syphon Aqueduct
Consider section
From
This loss of head is calculated using manningâ€™s formula, using the value of 0.014 for n
Length of R.C trough = (3x 2.5) + (2x1) + (2x0.5) = 10.5 m
Sectional area in the trough A4 = 12x2 = 24 m2 

Velocity developing 
= 2435 
= 1.46 m/s 

Wetted perimeter 
= p = (2x2) + 12 = 16 m 

Hydraulic mean depth 
= R = 
4 
= 1624 
= 1.5 m 

Manningâ€™s formula, V 
= 
1 

(R)2/3 
(S)1/2 


1.46 = 
0.0141 

(1.5)2/3 (S)1/2 


S = 41101 



Head loss = S x length = 41101 
x 10.5 = 0.003 m 
T.E.L at
Neglecting the frictional loss in the exit transition the eddy loss in the transition is calculated as follows

Q = 35 m3/s 


A5 
= (B +n y) y 

Here B = 20 m, y = 2 m, n = 21 

A5 = (20 + 21 
2) 2 = 42 m2 

5 
= 4235 = 0.83 m/s 

V5 
= 
There is a gradual change in the section from
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Design of Syphon Aqueduct 
Head loss 
= 0.25 x (V42 V52)/2g = 0.25 x (1.462 0.832)/2 x 9.81= 0.018 m 
T.E.L at 

Velocity head 
= V52/2g = 0.832 / 2x 9.81 = 0.0351 m/s 
T.E.L at 

41.996 = HFL at TEE + 0.0351 

HFL at TEE = 41.961 m 

F.S.L at 
= 42.00 m 
Total loss of head = loss of head from
=TEL at
=42.037 â€“ 41.961 = 0.039 m
Total head loss from A to E = 0.004 + 0.0175 + 0.003 + 0.018 = 0.0425 The total head loss is very small. Hence it can be neglected.
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Design of Syphon Aqueduct
Chapter  7
Fixing the M.F.L of the drainage
The MFL of the drain in rear of the siphon barrel is 39.75. So, the barrel flows full under maximum flow conditions. The necessary afflux required to push through 60 m3/s with a velocity of 3.25 m/s is calculated by unwins inverted syphon formula,
Afflux, d = (1+f1 +f2 ) 22
Here v= velocity in the drain = 3.25 m/s
g= 9.81 m/s2
L = length of drain = 12.60 m
C/S area = 3 x 2.5 x 2.45 = 18.375 m2
Wetted perimeter = p = 3 x (2 x (2.5+2.45)) = 29.7 m
R= hydraulic radius = = 1829.7.375 = 0.62 m
f1= 0.0505
f2 = a (1+ 0.3 ) = 0.003 (1+ 0.3 00.1.62 ) = 0.003145 d = (1+0.505+ 0.00315 120.62.60 ) (3.225 9.813.25) = 0.85 m
M.F.L on U/S = D/S M.F.L + afflux = 39.75 + 0.85 = 40.60 m
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Design of Syphon Aqueduct
Afflux at the drop of bed
Bed level of drainage = 38.00
At crossing with canal, bed level of drainage = 37.00
Drop in the bed level = 38 â€“ 37 = 1
M.F.L of the drain = 39.75 m
Bottom level of the canal trough = 39.45 m
Afflux required = 39.75 â€“ 39.45 = 0.3 m
Here drop is 1 m then it is treating it as a drowned weir (submerged weir) For submerged weir, q = 3.54 y2 d10.5 + 1.77 d13/2
y2 = depth of water = 2.60 m q = 2 = 6011 = 5.45 m2/s
B2 = width of drainage b/w wing walls 5.45 = 3.45 (2.60) d10.5 + 1.77 d13/2
5.45 = 8.97 d10.5 + 1.77 d1 d10.5
5.45 = d10.5 (8.97+1.77 d1) 5.452 = d1 (8.97+1.77 d1)2
29.70= d1 (80.46+3.14 d12+31.75 d1)
3.14d13 + 31.75 d12 + 80.46 d1 â€“ 29.70 = 0
d1= 0.326
M.F.L over the drop = U/S M.F.L + afflux = 40.60 + 0.32 = 40.92 m
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Design of Syphon Aqueduct
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Design of Syphon Aqueduct
Chapter  8
Design of side walls of canal trough
Bottom level of the side wall = bottom level of the canal trough
Top level of the side wall = U/S F.S.L + 0.5 = 42.50 + 0.5 = 43.00
Depth of water h = U/S F.S.L â€“ Sill level = 42.50 â€“ 39.75 = 2.75 m
Let top thickness = 2 m
It is designed as a cantilever wall
of water = 10 KN/m3
Water pressure = p = x h = 10 x 2.75 = 27.5 KN/m2
Let us consider 1 m length of side wall
Total pressure, p= Area of pressure diagram x length of wall = 12 x 27.5 x 2.75 x 1 = 37.81 KN
Centre of pressure,y = â„Ž3 = 2.375 = 0.917 m
Bending moment, m = p x y = 37.81 x 0.917 =
Mu = 1.5 x 35 = 52.17
Adopting
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Design of Syphon Aqueduct
= 0.48 





D = 300 mm, 
b = 1000 mm, d1 = 40 mm, d = D  d1 

d = 300 â€“ 40 = 260 mm 



Mu, limit = 0.36 


bd2 fck (1 â€“ 0.42 

) 



=0.36 x 0.46 x 1000 x 2602 (1 â€“ 0.42 x 0.48)x20
=186.6
Mu< Mu, limit (O.K)
Design of steel reinforcement
(a)Main steel :
1)Minimum area of steel,
Ast, min = 0.12% of0.gr12oss area
=100 x 1000 x 300
=360 mm2
2)Maximum area of steel , Ast, max = 4% of gross4 area
=100 x 1000 x 300
=12,000 mm2




3) Mu1 = 0.87 fyAst d (1 â€“ 

) 












52.17 x 106 = 0.87x415x260x Ast1x 







415 

) 

(7.98 x 







555.75 = Ast1 Ast12 







1000 
260 
20 









Ast1 = 582.86 mm2 , 11947.25 mm2 







Ast1< Ast1, max 
(O.K) 







Ast1 
> Ast1, min 
(O.K) 

For Ast1 = 11947.25 mm2 










= 
0.87 
= 
0.87 
415 
11947.25 = 2.304 









0.36 

0.36 
20 
1000 
260 





=0.48
>(Not O.K)
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Design of Syphon Aqueduct



For Ast1 
= 583 mm2 




= 
0.87 415 
583 
= 0.112 










0.36 20 1000 260 





< 


(O.K) 
















Ast1 = 583 mm2 






Let us adopt 12 mm dia bars, 1 = 12 mm 





Area of one bar, A = 3.414 x 122 = 113 mm2 





Number of bars, n1 = Ast1A = 113583 = 5.16 





Spacing, S1 = 1000n1 = 193.8 mm 






Adopt 12 mm @ 180 mm C/C 

Check for shear design 



Nominal shear force, Ï„v = 
= 371000.81 260103 
= 0.145 N/mm2 


Percentage of steel provided = 100 
= 100 
583 = 0.224% 


As per IS 456 â€“ 2000 

1000 
260 




For, 
100 
= 0.224% then Ï„c = 0.81 N/mm2 

Ï„v<Ï„c 
(O.K) 




As per IS â€“ 456 â€“ 2000, For
Ï„c, max = 2.8 N/mm2
Ï„v<Ï„c, max (O.K)
Hence provide minimum shear reinforcement,
as per 

1) 
= 
0.4 
0.87
Let us adopt3.14 4 legd stirrups of 8 mm dia
Asv = 4 x 4 x 82 = 200 mm2
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Design of Syphon Aqueduct
200 
= 
0.4 
1000 

0.87 415 
Sv = 180 mm
2)0.75 X d = 0.75 x 260 = 195 mm
3)300 mm
Sv = 180 mm
Adopt 4 legd vertical stirrups @ 8 mm dia @ 150 mm C/C
Distribution steel 










Providing steel on both faces 





= 360 = 180 mm2 

1) Area of steel , Ast2 = 














2) Let us adopt dia of bar, 
2 2 = 8 
mm 






2 

Area of one bar, A 2 = 
3.14 x 82 = 50 mm2 

Number of bars, n2 
= 
Ast2 
4= 
180 
= 3.6 

Spacing, s2 = 



A= 


50= 277.7 mm 


1000 

1000 


Adopt 8mm dia @n2250 
mm C/C 


3.6 

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Design of Syphon Aqueduct
Chapter  9
Design of bottom slab of canal trough
It is designed as a continuous slab.
Let us consider 1m wide slab
Thickness of wearing coat = 8 cm
Weight of wearing coat = 1008 x 24 = 1.92 KN/m2
Thickness of slab = 25 cm
Weight of slab = 10025 x 25 = 6.25 KN/m2
Depth of water = 2.75 m
Weight of water = 2.75 x 10 = 27.5 KN/m2
Total load on the slab = 1.92 + 6.25 + 27.5
= 35 KN/m2
Effective span (l) = clear water way + effective thickness of slab


= 2.5 + 0.26 = 2.76 m 


Maximum B.M = M3 = 2 = 35 
2.76 2.76 
= 26.67 


10 

10 





Mu3 = 1.5 x M1 = 40 

Mu, limit = 0.36 

bd2 fck (1 â€“ 0.42 


) 





=0.36x0.48x (1 â€“ 0.42 x 0.48) x1000x260 x 20
=186.6
Mu3<Mu,limit (O.K)
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Design of Syphon Aqueduct
Design reinforcement
a)Main steel
1)Minimum area of steel , Ast, min0.12= 0.12% of gross area
=100 x 1000 x 300
=360 mm2
2)Maximum area of steel ,Ast, max =44% of gross area
=100 x 1000 x 300
=12,000 mm2
3) Mu3 = 0.87 fyAst d (1 â€“ 


) 
1000 
3 415 





40 x 106 = 0.87 x 415 x Ast3 x 260 x (1â€” 
) 

426.10 = Ast3 Ast32 (7.98 x 
260 20 


Ast3 = 441.66 mm2 






= 12089 mm2 






Ast3 = 442 mm2 






Ast3<Ast, max 
(O.K) 




Ast3 >Ast,min 
(O.K) 




Let us adopt 12mm dia bars, 3 = 12 mm 




Area of one bar, A 3 = 3.14 x 122 = 113 mm2 


Spacing, s3 = 1000 
= 41000 = 255.6 mm 



Adopt 12 mm dia bars @ 250 mm c/c 




n3 
3.91 



b) Distribution steels
Providing steel on both faces 
360 


Area of steel, Ast4 = 


= 
= 180 mm2 




Adopt 8mm dia @ 250 
2mm c/c.2 

Check for shear design 
35 
22.76 = 48.3 KN 





Shear force, V = 2 = 
10 10 = 0.185 N/mm2 

Nominal shear force, Ï„v 
= = 
48.3 
10 






10 
10 
10 
260 

2 

As per 
=2.8 N/mm 


Ï„v<Ï„c, max (O.K) 
100 


100 
442 





Percentage of steel, 
= 
10 

= 0.17% 





10 
10 
260 



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Design of Syphon Aqueduct
As per
Ï„c = 0.3 N/mm2
Ï„v<Ï„c (O.K)
Minimum shear reinforcement is provided.
Sv is least of 


0.4 



1) 

= 

= 









0.87 
0.4 



200 




10 
10 
10 

0.87 415 
Sv = 180 mm
2)0.75 d = 195 mm
3)300 mm
Sv = 180 mm
Adopt 4 legd vertical stirrups @ 8 mm dia @ 180 mm c/c
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Design of Syphon Aqueduct
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Design of Syphon Aqueduct
Chapter
Design of tail channel
Tail channel will be always straight, its length will be 50 to 60m on either side of roads Top level = M.F.L of drain
= 39.75m
Bottom level = bed level of the drain at crossing = 37.00m
Depth of flow, Y3 =
Let us assume velocity of flow, V = 1.5m/sec
Q = AÃ—V
60 =1.5A
A = 40m2
Slope = 12H: 1V (assume)
A = (B+ny) y
40 = (B+0.5Ã—2.75)2.75
B = 13.17m
Adopt B = 14m 



Slope of channel, 



Manningâ€™s formula, V = 1 (R)2/3 (S)1/2 

Here, V = 1.5m/sec, N = 0.015 (assume) 

A = (B+ny)y 



= (14+0.5Ã—2.75) 



A = 42.3m2 
( 
2 

Wetted perimeter, P = B+2 
.y 

= 14+2( 
( .+)2)+ 
)Ã—2.75 
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Design of Syphon Aqueduct 


= 20.15m 

R = 
= 
= 2.1m 

V = 
(R)2/3 (S)1/2 


1.5 = 

(2.1)2/3 (S)1/2 

S = 



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32 
Design of Syphon Aqueduct
Chapter  11
Design of canal transitions
Transitions are wing walls
Upstream side transitions for canal:
The bottom of foundation is same as that of the abutments. Assuming 60cm depth of concrete foundation. The top of foundation is kept at 37.00m
Top level = ultimate full supply level + 0.5m = 42.50 + 0.50 = 43.00m
Bottom level = hard soil level = 37.00m
Height of the wall = 43.00 â€“ 37.00
= 6.00m Thickness of foundation = 0.6m Top thickness = 0.5m
From top level to the ultimate bed level of the canal the front face is vertical Height of wing wall from ultimate bed
=0.4X3.25
=1.3m
Let us provide width ofwing wall @ ultimate bed level=1.75m
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Design of Syphon Aqueduct
From ultimate bed level to t op of foundation is vertical on earth phase
Height=top
Bottom width=0.4Xheight =0.4X6 =2.4m
Let us provide width of wing wall=2.5m
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Design of Syphon Aqueduct
Downstream side transition for canal:
In order to minimize the eddy losses, a suitable exit transition is necessary after the R.C trough Top level = ultimate F.S.L + 0.5m
=42.50m + 0.5m
=43.00m Bottom level = 37.00m
Thickness of foundation = 0.6m
Bottom level of foundation = 37.00 â€“ 0.6
= 36.40m Height = top level â€“ bottom level
=43 â€“ 37
=6m
Top width = 0.50m
The downstream side wing wall is sloping at 12 : 1 up to the bed level, then it is vertical
Height of wing wall from ultimate bed
Width of wing wall @ ultimate bed level=0.4Xheight
=0.4X3.25
=1.3m
Let us provide width ofwing wall @ ultimate bed level=2.125m
From ultimate bed level to top of foundation is vertical on earth phase
Height=top
Bottom width=0.4Xheight =0.4X6
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Design of Syphon Aqueduct 
=2.4m 

Let us provide width ofwing wall=2.125m 

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36 
Design of Syphon Aqueduct
Chapter
Design of abutments
Top level = bottom level of centrral tough = 39.42m
Bottom level = hard soil level = 37.00m
Bearing of canal tough = 0.5m
Top width = 2Ã— length of bearin g
= 2Ã— 0.5 = 1m
Height of wall = top level â€“ bott om level
=39.42 â€“ 37.00
=2.42m
Bottom width = 0.4 Ã— height
=0.4 Ã— 2.42
=0.968m
Adopt bottom width = 2m
Front batter = 1 in 8
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37 


Design of Syphon Aqueduct
Check for stability of abutment:
Let us consider 1m length of wall
Unit weight of RCC = 24 KN/m 3
Weigh of triangular portion 1, V1 = unit weight Ã— volume
=24 (0.5Ã—bÃ—hÃ—l)
=24 (0.5Ã—0.3Ã—2.42Ã—1)
=8.71KN
X1 = ( + 0.5) = 0.2m from point B
M1 = V1Ã—X1 = 8.71 Ã— 0.2 = 1.74
Weigh of triangular portion 2, V2 = unit weight Ã— volume
=24 (bÃ—hÃ—l)
=24 (1Ã—2.42Ã—1)
=58.08 KN
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Design of Syphon Aqueduct
X2 = (0.3 + 0.5) = 0.8m from point B
M2 = V2Ã—X2 = 58.08 Ã— 0.8 = 46.46
Weigh of triangular portion 3, V3 = unit weight Ã— volume
=24 (0.5Ã—bÃ—hÃ—l)
=24 (0.5Ã—0.7Ã—2.42Ã—1)
X3 = (0.3+1+ 31 Ã— 

= 20.32 KN 

. ) = 1.53m from point B 

M3 = V3Ã—X3 = 20.32 Ã— 1.53 = 31.15 

Reaction from canal tough, V4 = 
2 
= 35.6Ã—2.5 



2 

X4 = (0.3+ 21 Ã— . 


= 44.58 KN 
) = 0.55m from point B 
M4 = V4Ã—X4 = 44.58 Ã— 0.55 = 24.51
Total vertical force, V = V1+V2+V3+V4
=8.71+58.08+20.32+44.58
=131.69KN
Earth pressure, p = KaÎ³H
Ka = 13, Î³of earth = 20 KN/m3 p = 13 Ã—20Ã—2.42 = 16.13 KN/m2
Total pressure P = area of pressure diagram Ã— length
=( 12 Ã— 16.13 Ã—2.42 Ã—1)
=19.51KN
Y = 13 Ã— 2.42 = 0.81m
M5 = P Ã— Y
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Design of Syphon Aqueduct
=19.51 Ã— 0.81
=15.8
Overturning moment, Mo = 15.8
Net moment, M = MR â€“ MO = 103.86 â€“ 15.8 = 88.06
Lever arm, a = MV =b13188.06.69 = 0.66m2
Eccentricity, e = ( 2  a ) = ( 2 â€“ 0.66 ) = 0.34m
Max stress, Ð±max = VB ( 1 + 6eB )
= 1312.69 ( 1 + 6Ã—02.34 )
= 133 KN/m2
V 6e
Min stress, Ð±min = B ( 1 + B )
= 1312.69 ( 1  6Ã—02.34 )
=
Mr 103.86
Factor of safety against overturning = Mo = 15.8
= 6.57 > 1.5 ( ok ) Factor of safety against sliding = ÂµVP = 0.6Ã—13119.51.69 = 4.04 > 1 ( ok )
Allowable compressive stress in foundation concrete = 4 N/mm2 (for
Ð±maxis less than 4000 KN/m2 ( ok )
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Design of Syphon Aqueduct
Chapter
Design of piers
Top level = bottom level of centrral tough = 39.42m
Bottom level = hard soil level = 37.00m
Bearing of canal tough = 0.5m
Top width = 2Ã— length of bearin g
= 2Ã— 0.5 = 1m Thickness of foundation = 0.6m
Height of wall = top level â€“ bott om level
=39.42 â€“ 37.00
=2.42m
Bottom width = 0.4 Ã— height
=0.4 Ã— 2.42
=0.968m
Adopt bottom width = 2m
Front batter = 1 in 8
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41 


Design of Syphon Aqueduct
Check for stability of piers:
Width of pier = 1m
Length of pier = width of canal tough = 12m
Clear spacing between piers = 2.5m
Length of canal tough on one pier = 2.5 + 1 = 3.5m
On pier there is water pressure from 3.5m wide.
Weight of pier, V1 = unit weight Ã— volume
=(24Ã—12Ã—2.42Ã—1)
=696.96 KN
It is acting at a distance, X1 = 0.5 Ã— 12 = 6m from D
M1=V1Ã—X1 = 696.96 Ã— 6 = 4181.76
Weight of canal tough, V2 = WÃ—width of canal toughÃ—length of canal trough in consideration
=35.67Ã—12Ã—3.5
=1498.14 KN
It is acting at a distance, X2 = 0.5 Ã— 12 = 6m from D
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Design of Syphon Aqueduct
M1=V2Ã—X2 = 1498.14 Ã— 6 = 8988.84
Total vertical force, V = V1 + V2
= 696.96 + 1498.14
= 2195.11 KN
Resisting moment, MR = M1 + M2 = 4181.76 + 8988.84
= 13170.6
Weight of water =Î³w = 10KN/m3
Water pressure, p =Î³Ã—H =10Ã—2.42 = 24.2 KN/m2 




Total pressure, P = area of pressure diagram Ã— width of water way 








= ( 21 
Ã—24.2Ã—2.42) (3.5) 












= 102.5 KN 










It is acting at a distance 

= 31 . 


= . 




M3 













3 = 

âˆ’ 




Overturning moment, m 


m 







= 


Ã— 
= 


. 
Ã—o 
= 
. 




















=13170.6âˆ’â€“ 83 




Net moment , m = (mr â€“ mo) = 
= 13087.6 



Lever arm, a = 
= 
130872195.1.6 = 5.9 m 
. = . 




Eccentricity, e = ( 
2 
âˆ’ 

) = 
122 
âˆ’ 




Ïƒ max = 


+ 
6 
2= 
2195.1 


+ 
6Ã—0.1 


















= 

. 

/ 
12Ã—1 



12 




2 


Ïƒ min = 



âˆ’6 
= 219512.1 
âˆ’6Ã—012.1 
= 

. 
/ 










Factor of safety against over turning = 

= 1317083 .6 




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43 
























Design of Syphon Aqueduct
Factor of safety against sliding = 
Âµ 
= 
= 
. 

( 
) 




0.6Ã—2195102.5 
.1 


) 

2 






Allowable compressive stress in 
foundation concrete 










= 
. 

â‰¥ ( 
= 
/ 


= 
/ 
2 









Ïƒ max < 4000 KN/m2, Ïƒ min >0 (ok)
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Design of Syphon Aqueduct
Chapter â€“ 14
DESIG N OF DRAINAGE WING WALL
U/S Wing wall :
The wing wall as two portions
1)Slopping wing wall
2)Level wing wall
The slopping wing wall is slopping from top of wing wall for canal to the level o f M.F.L.
Let us assume M.F.L of drain = 41.50 m
1)Slopping wing wall :
a)Wing wall at junction of trough :
Top of wing wall (or) top level = 43.00 Top of foundation (or) bottom level = 37.00 Height = top level â€“ b ottom level
= 43  37 = 6 m Thickness of foundation = 0.6 m
Bottom level of foun dation = 37.00  0.6 = 36.40 m
Top width = 0.5 m Bottom thickness
Front batten
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Design of Syphon Aqueduct 
b) Wing wall at + 41.50 level : 

Top level = 41.50 

Bottom level = 37.00 

Thickness of foundat ion = 0.6 

Bottom level of foun dation = 37 â€“ 0.6 

= 36.40 m 

Height = top level â€“ b ottom level 

= 41.50 â€“ 37.00 

= 4.50 m 

Top width = 0.5 m 

Bottom width 

Front batten 

2) Level wing wall : 

Top level = 41.50 

Bottom level = 37.00 

Thickness of foundation = 0.6 

Bottom level of foun dation = 37 â€“ 0.6 

= 36.40 m 

Height = top level â€“ b ottom level 

= 41.50 â€“ 37.00 

= 4.50 m 

Top width = 0.5 m 

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46 
Design of Syphon Aqueduct
Bottom width
Front batten
D/S Wing wall :
The sloping wing wall is slopping from top of wing wall for canal to level of 40.50 m
1)Slopping wing wall :
a)Wing wall at junction of trough
Top of wing wall (or) top level = 43.00 Top of foundation (or) bottom level = 37.00 Height = top level â€“ b ottom level
= 43  37 = 6 m Thickness of foundat ion = 0.6 m
Bottom level of foun dation = 37.00  0.6 = 36.40 m
Top width = 0.5 m Bottom thickness
Front batten
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Design of Syphon Aqueduct
2)Level wing wall :
Top wing wall = 40.50 m Bottom level = 37.00 m Height of wall = 3.50 m
Thickness of foundation = 0.60 m Top width = 0.5 m
Bottom width Front batten = 1 in 8
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Design of Syphon Aqueduct 
Chapter 

Design of return wall 

U/S Return wall : 

Top level = 41.50 

Bottom level = 37.00 

Thickness of foundat ion = 0.6 

Bottom level of foun dation = 37 â€“ 0.6 

= 36.40 m 

Height = top level â€“ b ottom level 

= 41.50 â€“ 37.00 

= 4.50 m 

Top width = 0.5 m 

Bottom width 

Front batten 

Sri Sunflower College of Engineerin g & technology 
49 
Design of Syphon Aqueduct
D/S return wall :
Top wing wall = 40.50 m
Bottom level = 37.00 m
Height of wall = 3.50 m
Thickness of fou ndation = 0.60 m
Top width = 0.5 m
Bottom width
Front batten = 1 in 8
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50 


Design of Syphon Aqueduct
Chapter
Design of canal apron
In between the canal wings, concrete is laid as a apron to prevent water percolating by the side of the abutment exert pressure under the drainage apron. The uplift is maximum when the canal is full and drainage is empty.
In this case, the gross head causing uplift at F.S.L
Before the water creeps to the bottom of the drainage aprons, some head is lost .assuming that the canal apron is laid sloping from the top of trough slab +39.75 to a level +38.00 (ground level ) for a length of L meters, as shown in fig the vertical creep is neglected.
The canal wing upstream and downstream will be splayed such that by the time the end of apron is reached, the distance between their faces is equal to the theoretical bed width of canal,i.e.,20.00 meters. This decides the splay of canal wings.
The apron is to be laid from canal sill level to natural ground level
Gross uplift head = canal
=
=5m
Let us provide the canal apron sloping from top of the trough slab +39.75 to a level (ground level) = 38.00
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Design of Syphon Aqueduct
Let us provide 60cm thick mass concrete for drainage floor
Thickness = residual
0.6 = residual
Residual head =0.84m
Net uplift head = gross uplift head
=
=4.16
Let us assume exit gradient
GE= 1 inâ„Ž4 = Â¼1
=4
Therefore L = 17m
Length of apron(L)=17m.
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Design of Syphon Aqueduct
Chapter
Checking the depth of foundation of drainage returns by scour depth
Upstream side
Maximum flood discharge = 60 m3/sec
Maximum flood level = 40.94m
Length of apron retaining wall = 14m (assume) Discharge per meter length of apron retaining wall q = 60/14 = 4.3m2/sec
Depth of scour = 1.374 (q2/f)1/3
=1.374 ((4.3)2/1)1/3
=3.562m
The foundations of returns and apron retaining wall are to be taken down to
However the foundations have been taken down to +36.40 and are quite safe.
On D/s side also, the foundations are taken down to +36.40 and as the distance between the returns is also more or less same . The foundations adopted are safe.
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Design of Syphon Aqueduct
Chapter
INSPECTION TRACK
The inspection track on the left embankment of canal also has to be taken across the drain by means of a bridge just by the side of the canal trough.
The width of roadway between kerbs may be kept large enough to meet the demands of traffic proposed on the canal banks. In this case, it is kept as 3.65 meters (12 feet wide). Depending on the traffic, the road bridge may be designed. In the present case, the roadway is carried over plain concrete arches since there is enough headroom above water level. The springings of arches are kept above water level in the drain.
In this case the thickness of 50 cms adopted for the arches is quite enough and the detailed design of arch is not attempted.
Keep the springing level of arches a little above the rear M.F.L., i.e., +40.00. 

Bottom level of arch (intrados) is 40.00 + . 
= . . 
Thickness of arch = 0.50 m.
Therefore, top of arch (extrados) = 41.75.
This top level of road surface may be kept at +43.00. The space in between the road level and top of arch is covered with earth to act as cushion over the arches.
The road width between kerbs is kept at 3.65 meters with suitable parapets. The inspection track over the arches is suitably connected to the canal banks by canal transitions.
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Design of Syphon Aqueduct
Chapter
Design of
i.Thickness of cap = 600mm (assume)
ii.Projection on each side = 600mm (assume)
Reinforcement detailing
1.Minimumarea of steel, ast1min =0.12% gross area
=(0.12/100)*600*1000
=720mm2
2.Maximum area of steel, ast1max = 4% of gross area
=(4/100)*600*1000
=24,000mm2
Load on the pier V =2195.11 KN
Number of pier = 2
Load on each pile = 2195/2
V= 1097.5 KN
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Design of Syphon Aqueduct
Shear force v = 2 1097.5 = 21.8
W = 1220 KN/m
Here the beam is considerd as a continuous beam
Max bending moment = 122
1220 1.8 1.8 = 12
= 329.25
Factored moment = Mu = 1.5 X M = 1.5 X 329.25 = 493.875
Check for thickness 






Mu, limit = 0.36 


bd2 fck (1 â€“ 0.42 

) 





for 


= 0.48 







Here b= 1000 mm
D= 600 mm
d1= 50 mm
d = D  d1 = 600 â€“ 50 = 550 mm fck = 20 N/mm2
Mu, limit = 0.36 X 0.48 X 1000 X 5502 X 20 (1 â€“ 0.42 X 0.48)
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Design of Syphon Aqueduct
= 834
Mu < Mu, limit
Thickness is satisfied.
(a)Main steel
Mu= 438 KNm 





=Mu=0.87f. yastdÃ— (1 (Ast fy/b d fck ) ) 


= . 

Ã— 
Ã— 
2 ( 
âˆ’(( 
Ã— 
)/( 



6396 mm2 
( . 
Ã— 
âˆ’ 
) 

Ast = 
= 

âˆ’ 

Ast = 20109 mm2 





Adopt Ast = 6396 mm2 




Xu/d = 0.87fyAst/0.36fckbd = 0.42 ; 


(xumax/d) > (xu/d) 
(ok) 



Ast = 20109 mm2 





Xu/d =2.96 (not ok) 





Ast = 6396 mm2 





Let us adopt Ã˜=16 mm 




AÃ˜ = 4Ï€ * 162 = 201mm2 






Ã˜ 
= 

2240201 = 




= AstA 
= 





= 



= . 












Adopt 16mm Ã˜ @75mm c/c on both sides 

(b)Distribution steel: 

Ast 
Ast1 in 
= 760= 380mm2 
= 
2 
2 
(O.K)
Ã— Ã— )))
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Design of Syphon Aqueduct
Adopt Ã˜ = 10mm
AÃ˜ = 4Ï€ * 102 = 78.53mm2
= Ast = 380 = .
AÃ˜= 78.53 8
s = 206mm
Adopt 10mm Ã˜ @ 200mm c/c on both sides
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Design of Syphon Aqueduct
Chapter
Design of pile foundation
Pier cap size â€“ 2.4 wide *4.2m length
Adopt 6 numbers 450mm Ã˜ piles
Pier cap thickness â€“ 1.2m
20 mm dia @ 150mm c/c in top and bottom
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Design of Syphon Aqueduct
Chapter
Design of foundation of abutment and piers
Foundation of piers and abutments are to be taken down to hard ground. As per data, hard ground is available below +37.00.
So the foundation of piers level of foundation is +37.00.
As seen in the plan the drainage sill is kept at +37.00 and with a depth of drainage floor as 60 cms, the bottom level of the drainage apron also is at +36.40.
So, the drainage apron, foundation of piers and abutments will all be laid as one block of concrete of 60 cms. thick (for the drainage barrel portion) as shown in the plan.
This distributes the load of the structure evenly on the soil below and drainage apron will also be capable of acting as an inverted arch to take care of the extra uplift pressure.
Where the soil of enough bearing capacity is met with at a deeper level, the foundation will be taken deeper and the drainage apron will be at higher levels. in such cases, the actual pressure under the foundation of abutments will have to be checked and verified so that they do not exceed the safe bearing capacity.
The drainage apron in such cases, not being monolithic with the foundation of the abutments and piers will not be able to take care of the any uplift pressure by arch action. The uplift pressure that can be resisted is only due to the weight of the concrete apron.
In the present case, for safety the thickness of the pier adopted is 1.00 meter. Abutment under the road arches has a bottom width of 1.75 meters and top width of 1.00 meter .the abutment under the road arches has a bottom width of 2.25 meters and a top width of 1.25 meters. The abutment has a uniform face better 1 in 8.
These abutments, in actual construction, will have to be carefully checked for the stability taking into account the earth pressures, surcharge, etc. acting on them. The maximum pressures on the soil have to be checked so that they do not exceed the safe bearing pressure on the foundation soil.
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Design of Syphon Aqueduct
Arc lengths to fix the lengths of drainage wings
Downstream side of drain: 

Canal F.S.L 
+42.00 
Drainage bed 
+37.00 
Difference 
+5.00 m 
Arc length =5 meters. 

Upstream of drain: 

Canal F.S.L 
+42.00 
Drainage bed 
+38.00 
Difference 
+4.00 m 
Arc length along which creep may occur =4X4=16 meters.
Since the downstream transitions of canal will be lined with masonry even beyond the canal wings, the creep length is fixed from the end of canal aprons upstream and the arch length along which creep occurs is shown in the plan.
In the drawing, keeping the distance between the returns as 14 meters both upstream and downstream and keeping the lengths till the hydraulic gradient cuts the proposed drain bed level, the actual arc lengths along which the creep occurs are more than the required. Hence the proposed splays as in the drawing are adopted.
Solid apron in the drainage bed will be provided up to the end of the end of the drainage wings. The length of the drainage wings is limited by a hydraulic gradient as shown in dotted line in the drawing.
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Design of Syphon Aqueduct
Chapter
Design of anchorage arrangements
Since the barrel is flowing full and the drain M.L.F. on both sides is above the bottom level of the roof slab there will be an upward thrust acting on the roof slab there will be an upward thrust acting on the roof slab.so the roof slab have to be well anchored to the piers and abutments to prevent the upward movement of the R.C. slab.
The uplift is maximum when the barrel is full and canal empty. The worst condition is at upstream end of roof slab. M.F.L. just upstream of R.C. trough
Bottom level of the trough
Difference 
=1.14 
Thickness of roof slab
Roof slab will counteract
meters of uplift head
Net uplift head
Say 0.50 meters.
So, necessary anchoring arrangements are provided as
Design of anchor bolts:
Clear span of the slab =2.50m
Upward thrust acting on one span along the entire width of slab
= 2.5 X 12.60 X 0.5 X 1000 = 15750 kg.
Assuming 20 mm dia.rod, the thrust that can be registered by one
= 1260 X 3.14 = 3956 kg. No bolts required = 157503956 = 4 Noâ€™s (approx.)
So provide 4
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Design of Syphon Aqueduct
DRAWINGS
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Design of Syphon Aqueduct
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