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Design of Syphon Aqueduct

AQUEDUCT

Chapter 1: Introduction

3-10

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

14-15

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

16-19

Fluming of canal water way through the

 

Trough

 

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

20-22

Chapter 8: Design of side walls of canal trough

23-26

Chapter 9: Design of bottom slab of canal trough

27-30

Chapter 10: Design of tail channel

31-32

Chapter 11: Design of canal transitions

33-36

Chapter 12: Design of abutments

37-40

Chapter 13: Design of piers

41-44

Chapter 14: Design of wing walls

45-48

Chapter 15: Design of return walls

49-50

Chapter 16: Design of canal aprons

51-52

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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

55-58

Chapter 20: Design of pile foundation

59

Chapter 21: Design of foundation of abutment and piers

60-61

Chapter 22: Design of anchorage arrangements

62

Chapter 23: Drawings

63

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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

Diverting one stream into another.

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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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").

In this, canal water is carried across the drainage in a trough supported on piers.

Bridge carrying water

Provided when sufficient level difference is available between the canal and natural and canal bed is sufficiently higher than HFL.

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Classification of aqueduct and siphon aqueduct:

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.

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:

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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The structures that fall under this type are:

Super passage

Canal siphon or called syphon only.

Super passage:

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

A super passage is similar to an aqueduct, except in this case the drain is over the canal.

The FSL of the canal is lower than the underside of the trough carrying drainage water. Thus, the canal water runs under the gravity.

Reverse of an aqueduct

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Canal Syphon:

If two canals cross each other and one of the canals is siphoned under the other, then the hydraulic structure at crossing is called “canal siphon”. For example, lower Jhelum canal

is siphoned under the Rasul-Qadirabad (Punjab, Pakistan) link canal and the crossing structure is called “L.J.C siphon”

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.

The canal bed is lowered and a ramp is provided at the exit so that the trouble of silting is minimized.

Reverse of an aqueduct siphon

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:

Relative bed levels and water levels of canal and drainage

Size of the canal and drainage.

The following considerations are important

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When the bed level of the canal is much above the HFL of the drainage, an aqueduct is the obvious choice.

When the bed level of the drain is well above FSL of canal, super passage is provided.

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.

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.

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 canal-building.

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 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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Chapter -2
Hydraulic particulars
Canal:
Discharge = 35 m3/s Bed width = 20 m Bed level = +40.00 F.S.L = 42.00 Ultimate bed level = 39.75 Ultimate full supply level = 42.50 Top width of left bank = 5m Top width of right bank = 2m
T.B.L = +43.50 Slope of canal banks = 2:1
Drain:
Catchment area = 8 km2
Maximum discharge = 60 m3/s Bed level = 38.00 Average ground level = +38.00
Maximum flood level of drain at the site of crossing = +39.75 Hard soil for foundation is available at = +37.00
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Design of Syphon Aqueduct

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Design of Syphon Aqueduct

Chapter-3

Selection of type of aqueduct

The above data of hydraulic particulars, a type-3 aqueduct is designed. It is only purely from an economical aspect that we go in for the type-3 aqueduct. For major drains it will be uneconomical to go in for a type-3 aqueduct as the extra cost of barrel with a large number of vents will be more than the cost of other works necessary for a type-3 aqueduct.

So, whenever an aqueduct are to be actually constructed, comparative costs are to be worked out for a type-2 and a type-3, and whichever is economical is to be chosen and adopted.

In the case of a type-3 aqueduct, the canal will be flumed and taken through a masonry or reinforced concrete trough supported on piers and abutments. The maximum velocity through the trough is generally taken as twice the normal velocity or 1.5m/s whichever is less.

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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 – B.L= 42.00-40.00=2m

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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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

 

 

= 39.75-0.08-0.025=39.64 m

Bottom level of slab

 

= 39.75-0.25 = 39.50

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 drain=39.45-37=2.45 m

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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Chapter - 6

Check for loss of head in the canal due to fluming of canal water way through the trough

In a type-1 or type-2 aqueduct, the canal water way is not reduced and is taken over the drain as it is. Hence, there is no loss of heead in the canal.

However, in case of a type-3 aqueduct, the canal water-way is flumed or reduced, resulting in an increase in velocity through the trough. Unless there is a difference in water levels before entry and after exit, attainment of increased velocity in the trough is not possible.

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 A-A

 

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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Total energy line at A-A = F.S.L + (V12/2g) = 42.00+0.037 = 42.037

Consider section B-B

 

Canal width

= 20 m

Depth of water, y

=F.S.L- Bed level = 42.00 – 40.00 = 2.00

At B-B the canal is rectangle in cross section, area of flow a= 20x2 = 40 m2

Discharge, Q = 35 m3/s

Velocity of flow, V2 = Q/a = 35/40 = 0.87 m/s

Head loss from A-A to B-B due to change in the velocity V1 to V2

Head loss = (V22-V12)/2g

=(0.8752-0.832)/2x9.81

=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 B-B = T.E.L at A-A – eddy loss = 42.035 – 0.004 = 42.031

Section at the entrance of trough C-C

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 B-B to C-C. There is a loss of head from B-B to C-C due to change in velocity.

Head loss = 0.25 x ( V32- V22)/2g = 0.25 x (1.462-0.8752)/2 x 9.81 = 0.018

T.E.L at C-C with reference to section B-B = 42.035 – 0.018 = 42.017

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Consider section D-D

From C-C to D-D, there is a uniform velocity. The loss of head in the trough is only friction loss which manifests itself as surface fall to sustain the velocity.

This loss of head is calculated using manning’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

Manning’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 D-D = T.E.L at C-C – Head loss = 42.017 – 0.003 = 42.014 m Consider section E-E

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 D-D to E-E. There is a change in the velocity.

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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 E-E = T.E.L at D-D – Head loss = 42.014 – 0.018 = 41.99 m

Velocity head

= V52/2g = 0.832 / 2x 9.81 = 0.0351 m/s

T.E.L at E-E = H.F.L at TEE + Velocity head

41.996 = HFL at TEE + 0.0351

HFL at TEE = 41.961 m

F.S.L at A-A

= 42.00 m

Total loss of head = loss of head from A-A to E-E

=TEL at A-A – TEL at E-E

=42.037 – 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 – 37 = 1

M.F.L of the drain = 39.75 m

Bottom level of the canal trough = 39.45 m

Afflux required = 39.75 – 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 – 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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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 – Sill level = 42.50 – 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 = 35KN-m

Mu = 1.5 x 35 = 52.17 KN-m

Adopting M-20 grade concrete & Fe-415 grade steel

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Design of Syphon Aqueduct

= 0.48

 

 

 

 

 

D = 300 mm,

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

d = 300 – 40 = 260 mm

 

 

Mu, limit = 0.36

 

 

bd2 fck (1 – 0.42

 

)

 

 

 

=0.36 x 0.46 x 1000 x 2602 (1 – 0.42 x 0.48)x20

=186.6 KN-m

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 –

 

)

 

 

 

 

 

 

 

 

 

 

52.17 x 106 = 0.87x415x260x Ast1x

 

 

 

 

 

(1--

 

415

 

)

 

(7.98 x 10-6)

 

 

 

 

 

 

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 – 2000

 

1000

260

 

 

 

For, M-20,

100

= 0.224% then Ï„c = 0.81 N/mm2

Ï„v<Ï„c

(O.K)

 

 

 

 

As per IS – 456 – 2000, For M-20 grade concrete

Ï„c, max = 2.8 N/mm2

Ï„v<Ï„c, max (O.K)

Hence provide minimum shear reinforcement,

as per IS-456-2000, Sv is the least of

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 KN-m

 

10

 

10

 

 

 

 

Mu3 = 1.5 x M1 = 40 KN-m

Mu, limit = 0.36

 

bd2 fck (1 – 0.42

 

 

)

 

 

 

 

 

=0.36x0.48x (1 – 0.42 x 0.48) x1000x260 x 20

=186.6 KN-m

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 –

 

 

)

1000

3 415

 

 

 

 

40 x 106 = 0.87 x 415 x Ast3 x 260 x (1—

)

426.10 = Ast3- Ast32 (7.98 x 10-5)

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 IS-456-2000, for M-20 grade , Ï„c, max

=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 IS-456-2000, for M-20 grade, 100 = 0.17% then

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 -10

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 = 39.75-37.00 = 2.75m

Let us assume velocity of flow, V = 1.5m/sec

Q = A×V

60 =1.5A

A = 40m2

Slope = 12H: 1V (assume)

A = (B+ny) y

40 = (B+0.5×2.75)2.75

B = 13.17m

Adopt B = 14m

 

 

 

Slope of channel,

 

 

 

Manning’s formula, V = 1 (R)2/3 (S)1/2

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

A = (B+ny)y

 

 

 

= (14+0.5×2.75)

 

 

 

A = 42.3m2

(

2

 

Wetted perimeter, P = B+2

.y

= 14+2(

( .+)2)+

)×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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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 – 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 level=43.00-39.75=3.25m. Width of wing wall @ ultimate bed level=0.4Xheight

=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 level-bottom level

=43.00-37.00 =6.00m

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 – 0.6

= 36.40m Height = top level – bottom level

=43 – 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 level=43.00-39.75=3.25m.

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 level-bottom level

=43.00-37.00 =6.00m

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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Design of Syphon Aqueduct

Chapter -12

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 = 2× length of bearin g

= 2× 0.5 = 1m

Height of wall = top level – bott om level

=39.42 – 37.00

=2.42m

Bottom width = 0.4 × height

=0.4 × 2.42

=0.968m

Adopt bottom width = 2m

Front batter = 1 in 8

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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 × volume

=24 (0.5×b×h×l)

=24 (0.5×0.3×2.42×1)

=8.71KN

X1 = ( + 0.5) = 0.2m from point B

M1 = V1×X1 = 8.71 × 0.2 = 1.74 KN-m

Weigh of triangular portion 2, V2 = unit weight × volume

=24 (b×h×l)

=24 (1×2.42×1)

=58.08 KN

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Design of Syphon Aqueduct

X2 = (0.3 + 0.5) = 0.8m from point B

M2 = V2×X2 = 58.08 × 0.8 = 46.46 KN-m

Weigh of triangular portion 3, V3 = unit weight × volume

=24 (0.5×b×h×l)

=24 (0.5×0.7×2.42×1)

X3 = (0.3+1+ 31 ×

 

= 20.32 KN

. ) = 1.53m from point B

M3 = V3×X3 = 20.32 × 1.53 = 31.15 KN-m

Reaction from canal tough, V4 =

2

= 35.6×2.5

 

 

2

X4 = (0.3+ 21 × .

 

 

= 44.58 KN

) = 0.55m from point B

M4 = V4×X4 = 44.58 × 0.55 = 24.51 KN-m

Total vertical force, V = V1+V2+V3+V4

=8.71+58.08+20.32+44.58

=131.69KN

Earth pressure, p = KaγH

Ka = 13, γof earth = 20 KN/m3 p = 13 ×20×2.42 = 16.13 KN/m2

Total pressure P = area of pressure diagram × length

=( 12 × 16.13 ×2.42 ×1)

=19.51KN

Y = 13 × 2.42 = 0.81m

M5 = P × Y

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Design of Syphon Aqueduct

=19.51 × 0.81

=15.8 KN-m

Overturning moment, Mo = 15.8 KN-m

Net moment, M = MR – MO = 103.86 – 15.8 = 88.06 KN-m

Lever arm, a = MV =b13188.06.69 = 0.66m2

Eccentricity, e = ( 2 - a ) = ( 2 – 0.66 ) = 0.34m

Max stress, бmax = VB ( 1 + 6eB )

= 1312.69 ( 1 + 6×02.34 )

= 133 KN/m2

V 6e

Min stress, бmin = B ( 1 + B )

= 1312.69 ( 1 - 6×02.34 )

= -1.31N/mm2 (tension occurs)

Mr 103.86

Factor of safety against overturning = Mo = 15.8

= 6.57 > 1.5 ( ok ) Factor of safety against sliding = µVP = 0.6×13119.51.69 = 4.04 > 1 ( ok )

Allowable compressive stress in foundation concrete = 4 N/mm2 (for M-15 grade) = 4000 KN/m2

бmaxis less than 4000 KN/m2 ( ok )

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Design of Syphon Aqueduct

Chapter -13

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 = 2× length of bearin g

= 2× 0.5 = 1m Thickness of foundation = 0.6m

Height of wall = top level – bott om level

=39.42 – 37.00

=2.42m

Bottom width = 0.4 × height

=0.4 × 2.42

=0.968m

Adopt bottom width = 2m

Front batter = 1 in 8

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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 × volume

=(24×12×2.42×1)

=696.96 KN

It is acting at a distance, X1 = 0.5 × 12 = 6m from D

M1=V1×X1 = 696.96 × 6 = 4181.76 KN-m

Weight of canal tough, V2 = W×width of canal tough×length of canal trough in consideration

=35.67×12×3.5

=1498.14 KN

It is acting at a distance, X2 = 0.5 × 12 = 6m from D

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Design of Syphon Aqueduct

M1=V2×X2 = 1498.14 × 6 = 8988.84 KN-m

Total vertical force, V = V1 + V2

= 696.96 + 1498.14

= 2195.11 KN

Resisting moment, MR = M1 + M2 = 4181.76 + 8988.84

= 13170.6 KN-m

Weight of water =γw = 10KN/m3

Water pressure, p =γ×H =10×2.42 = 24.2 KN/m2

 

 

 

Total pressure, P = area of pressure diagram × width of water way

 

 

 

 

 

 

 

= ( 21

×24.2×2.42) (3.5)

 

 

 

 

 

 

 

 

 

 

 

= 102.5 KN

 

 

 

 

 

 

 

 

 

It is acting at a distance

 

= 31 .

 

 

= .

 

 

 

M3

 

 

 

 

 

 

 

 

 

 

 

 

 

3 =

 

−

 

 

 

Overturning moment, m

 

 

m

 

 

 

 

 

 

=

 

 

×

=

 

 

.

×o

=

.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

=13170.6−– 83

 

 

 

Net moment , m = (mr – mo) =

= 13087.6 KN-M

 

 

Lever arm, a =

=

130872195.1.6 = 5.9 m

. = .

 

 

 

Eccentricity, e = (

2

−

 

) =

122

−

 

 

 

σ max =

 

 

+

6

2=

2195.1

 

 

+

6×0.1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

=

 

.

 

/

12×1

 

 

 

12

 

 

 

 

2

 

σ min =

 

 

 

−6

= 219512.1

−6×012.1

=

 

.

/

 

 

 

 

 

 

 

 

Factor of safety against over turning =

 

= 1317083 .6

 

 

 

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43

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Design of Syphon Aqueduct

Factor of safety against sliding =

µ

=

=

.

 

(

)

 

 

 

0.6×2195102.5

.1

 

 

)

 

2

 

 

 

 

Allowable compressive stress in

foundation concrete

 

 

 

 

 

 

 

 

=

.

 

≥ (

=

/

 

=

/

2

 

 

 

 

 

 

 

 

 

σ max < 4000 KN/m2, σ min >0 (ok)

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Design of Syphon Aqueduct

Chapter – 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 – 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 – 0.6

 

= 36.40 m

 

Height = top level – b ottom level

 

= 41.50 – 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 – 0.6

 

= 36.40 m

 

Height = top level – b ottom level

 

= 41.50 – 37.00

 

= 4.50 m

 

Top width = 0.5 m

 

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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 – 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 -15

 

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 – 0.6

 

= 36.40 m

 

Height = top level – b ottom level

 

= 41.50 – 37.00

 

= 4.50 m

 

Top width = 0.5 m

 

Bottom width

 

Front batten

 

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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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Design of Syphon Aqueduct

Chapter -16

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 F.S.L-foundation level

=42.00-37.00

=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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4.16=14

Design of Syphon Aqueduct

Let us provide 60cm thick mass concrete for drainage floor

Thickness = residual head/(P-1)

0.6 = residual head/(2.40-1)

Residual head =0.84m

Net uplift head = gross uplift head -residual head

=5.0-0.84

=4.16

Let us assume exit gradient

GE= 1 inℎ4 = ¼1

=4

Therefore L = 17m

Length of apron(L)=17m.

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Design of Syphon Aqueduct

Chapter -17

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 40.36-3.56 = 37.38

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 -18

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.

Semi-circular arches or reinforced concrete deck slabs can be adopted.

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 -19

Design of pier-cap

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 KN-m

Factored moment = Mu = 1.5 X M = 1.5 X 329.25 = 493.875 KN-m

Check for thickness

 

 

 

 

 

Mu, limit = 0.36

 

 

bd2 fck (1 – 0.42

 

)

 

 

 

for Fe-415 grade steel

 

 

= 0.48

 

 

 

 

 

 

Here b= 1000 mm

D= 600 mm

d1= 50 mm

d = D - d1 = 600 – 50 = 550 mm fck = 20 N/mm2

Mu, limit = 0.36 X 0.48 X 1000 X 5502 X 20 (1 – 0.42 X 0.48)

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Design of Syphon Aqueduct

= 834 KN-m

Mu < Mu, limit

Thickness is satisfied.

(a)Main steel

Mu= 438 KNm

 

 

 

 

=Mu=0.87f. yastd× (1- (Ast fy/b d fck ) )

 

= .

 

×

×

2 (

−((

×

)/(

 

 

6396 mm2

( .

×

−

)

Ast =

=

 

−

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 Ø=16 mm

 

 

 

AØ = 4π * 162 = 201mm2

 

 

 

 

 

Ø

=

 

2240201 =

 

 

 

 

= AstA

=

 

 

 

 

=

 

 

 

= .

 

 

 

 

 

 

 

 

 

 

 

Adopt 16mm Ø @75mm c/c on both sides

(b)Distribution steel:-

Ast

Ast1 in

= 760= 380mm2

=

2

2

(O.K)

× × )))

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Design of Syphon Aqueduct

Adopt Ø = 10mm

AØ = 4π * 102 = 78.53mm2

= Ast = 380 = .

AØ= 78.53 8

s = 206mm

Adopt 10mm Ø @ 200mm c/c on both sides

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Design of Syphon Aqueduct

Chapter -20

Design of pile foundation

Pier cap size – 2.4 wide *4.2m length

Adopt 6 numbers 450mm Ø piles

Pier cap thickness – 1.2m

20 mm dia @ 150mm c/c in top and bottom

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Design of Syphon Aqueduct

Chapter -21

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 -22

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 holding-down bolts fixed on the piers through R.C slab.

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 holding-down bolt

= 1260 X 3.14 = 3956 kg. No bolts required = 157503956 = 4 No’s (approx.)

So provide 4 holding-down bolts on each pier.it is enough to provide half the number on the abutment, but in this case provide 3 bolts, one at each end of trough and one in the middle.

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Design of Syphon Aqueduct

DRAWINGS

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Design of Syphon Aqueduct

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