Waterway Design

8/3/2019 Waterway Design

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WATERWAY DESIGN for RLYBRIDGES and WEIR for RAT

A CASE STUDYA CASE STUDYCHENNAICHENNAIGUDUR SECTIONGUDUR SECTION

S.RLYS.RLY

Presented By

Sri D . Stanley

ADEN / SW /DHONE SCR

Sri S . Shanmughom

AXEN / MC / TVC SR

Guided By

Shri G.Bansal,Professor


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INTRODUCTION

Design of water way for Rly Bridges have been carried out

in the following circumstances.

1. Construction of New Lines

2. Doubling and Gauge Conversion

3. Rebuilding / Rehabilitation of Bridges

4. HFL raises above DL

5. Water over flowing the track

6. During Floods and breaches of track and Bridges


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Breach in embankment


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BR.NO.245


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DESIGN OF WATERWAY OF RLY BRIDGES

Criteria for design - based on catchment areafor catchment area < 25 Sq.Km

Using Improved Rational Formula

by IMD,RDSO and CWC( RBF-16)

for catchment area > 25 Sq.Km

Using Synthetic Unit Hydrograph Methodby IMD,RDSO and CWC ( Sub-zonal Report )


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CASE STUDY in S.RLY

Flash Flood on 15/16-Oct-2001. ( Rain fall =245mm )

MAS GDR Section @ Km.114 to Km.118

Touched the bottom of Girder @Br.239(6x12.2mGB )

Water crossed DL @ Br.No.240 (7x12.2m GB

Water Level above BOS @ Br.No.245 ( 2x1.83mRCC Slab-DN Line & 1x4.57PSC Slab UP Line


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Estmation of Q 50 Discharge forBr.244 and 245

Lattitude = 130

58 N , Longitude 790

54 ESub Zone 4(b)

Length,L = 1.5 Km

Height of Ridge above bed level ,H= 29.50 22.565 = 6.935m

Time of Concentration TC = (1.53/6.935)0.345

= 0.78 hours

R 50 ( 24 hours ) = 320mm

From graph short duration ratio for TC = 0.3


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ISOPLUVIAL MAP


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0.850.780.6825134

0.860.790.7013530.870.800.7152.52

0.880.810.722.501

60 - 18030 - 60< 30ToFrom

( in Minutes )( Sq.Km. )

Time of Concentration

catchment

Area

Sl.No.

Areal Reduction Factor


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Run off Coeffecient Constant(K)

0.498Hilly soil / Barren areas5

0.456Black cotton / Plain &Barren

//Submontene/Plateau areas

4

0.415Red soil / Clayey /Cultivated Plains / Tall

crops / wooded areas

3

0.332Alluivium / Silty / Coastalareas

2

0.249Sandy Soil/Arid Areas1

Value of K Description of CatchmentS.No


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Contd

Intensity of Rain fall , I= 0.30 * 320 / 0.78 = 123mm/hour

Catchment area ( A ) = 1.22 Sq.Km

,Areial Reduction Factor,F = 0.81

Run off Coeff,C = 0.415 *( 32* 0.81 )0.20 = 0.795

Using Improved Rational FormulaQ 50 = 0.278 * C*I*A = 0.278 * 0.795*123*1.22

= 33.18Cumecs.


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Capacity of Br.No.245( Exg 2 x 1.83m RCC Slab DN

and 1x 4.57 PSC slab UP )

B.O.S = 24.705 , Bed Level = 22.565

HFL = 24.800,Std VC = 0.600 + 3.180 * 0.60/269= 0.610m

Max Allowable HFL = 24.705 0.610= 24.095Max depth pf flow , DF = 1.53m

Wetted area , W A = ( 2*1.83 + 0.90 ) *1.53 =

6.98m2


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Wetted perimeter , WP = 4.56 + 2 * 1.53 = 7.62m

Hydraulic Mean radius , R = 6.98 / 7.62 = 0.92mSlope , S = 1 in 220

Velocity, V = (1 / 0.03) * ( 0.92) 0.67 * ( 1/220)0.50

= 2.12m/secDischarge, Q = 0.9 * 2 * 1.83 * 1.53 * 2.12

= 10.68 cumecs ( DN line Br. Capacity

I.e. < 33.18 cumecs ( Q 50 )

HFL Discharge of Br.245 ( UP line )

Similarly HFL Discharge = 25.94 cumecs < 250

VC available ( UP ) = 25.435 24.800 = 0.635

> 0.620m

VC (DN ) = 24.705 24.800 = -0.095 m


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Proposed 2 x 4.57m PSC slabBr.245Probable HFL = 24.165DF = 24.165 22.565 = 1.600m

Q = 0.90* 2 * 4.57 * 1.56 * 2.57 = 33.8 cumecs > Q 50VC available ( UP ) = 25.435 24.095 = 1.340 > 0.620m

VC (DN ) = 25.045 24.165 = 0.880 m > 0.620m

Free Board Available = 26.225 0.675 24.165 =1.385

I.e > 1.0m Hence OK

Hence It is proposed to rebuild Br.245 as 2 x 4.57 PSCslab ( UP & DN )


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Details of breaches of Tanks

16Damaragunta Tank ( RAT )11

140Kotambedu Tank10

25Chilamanuru Tank9

70Sangavaram Tank8

66Bhatlakanupuru Tank7

12Vengamamba puram Tank5

120Sagatooru Tank4

638Machavaram Tank3

60Mummayapalem Tank2

296Nemallapudi Tank ( RAT )1

Length of thebreach

Name of the TankSl.No.


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Estmation of Q 50 Discharge forBr.239 and 240

Latitude = 130 57 N , Longitude 790 47 E

Sub Zone 4(b)

Length,L = 32.47 Km,Lc=17.05 kmR 50 ( 24 hours ) = 340 mm

Catchment Area =250 SQ KM


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Computation of Equivalent slope

27.087180.58

118.790.1513732.75

1288.56

207.16103.5

8

61.7928032.554

591.2963.5841.799.36030.553463.0321.7921.7921.254021.252

000018.2101

Lix(Di-

1+Di

Di-

1+Di

Ht

Abov

Datm

(Di)

Length

(Li)

Redcd

levl

Dist

Fm Br

Sl No


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Tp=0.376(L*Lc/SQRT(S))0.43

S=1288.567/32.7^2=1.2 m/km : Tp=5.62 hrs=5.5 hrs

qp = 1.215/(tp)0.691 = 0.374cumcs / sq.km

W 50 = 2.211 / ( qp )1.07 = 6.33 hours

W 75 = 1.312 / ( qp ) 1.003 = 3.518 hours

WR 50 = 0.808 / ( qp )1.053 = 2.276 hours

WR 75 = 0.542 / ( qp ) 0.965 = 1.40 hours

TB = 7.621 * ( tp )0.623 = 22.04 hours

QP = qp * A = 0.374 * 250 = 93.50 cumecs

TM = tp + tr / 2 = 6 hours

Determination of Synthetic Unit

graph Parameters


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Unit Hydrograph


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l Estimation of Base FlowQb = 0.536 / ( A ) 0.523 = 0.03 cumecs / sq.km

Total base flow = 0.03 * 250 = 7.50 cumecs

Estimation of design storm duration :

Design storm duration , TD = 1.1tp=1.1*5.5

= 6 hoursEstimation of point rain fall & aerial rain fall

6 hour point rain fall coeff = 0.6950 year 6 h point rain fall = 0.69 * 340

Ariel fraction factor = 0.82

50 year 6hour aerial rain fall = 0.69 * 340 * 0.82= 192 mm


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Time distribution of Aerial Rain fall and Estimation of

Effective Rain fall units

0.00

0.410.40

1.55

3.09

9.62

1 houreffective

rain fall( in cm )

0.38

1.161.15

2.30

3.84

10.37

1 hour rainfall incriment

( in cm )

0.75

0.750.75

0.75

0.75

0.75

Designloss rate(

in cm /hour )

19.201.006

18.820.98517.660.924

16.510.863

14.210.742

10.370.541

StormRain

fall

DistCoeff

Duration (

inhour)


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Estimation of 50 yr Flood Peak

56.00

70.00

84.00

93.50

76.00

UGordinates(

cumecs )

1327.93Total22.400.409

28.700.418

259.563.097

899.479.626

117.781.555

Direct Runoff ( cumecs

)

1 hr effectiverain fall ( in

cm )

Time( inhours )

Q50 = 1327.93 + 7.50 = 1335 cumecs


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HFL Discharge of Br.No.239

( 6 x 12.2m ) GB & Br.No.240( 7 x 12.20mGB )HFL = 25.225 , BL = 18.900

DF = 25.225 18.9 = 6.325

WA =( 6 * 1.2.20 + 5 *1.60 ) * 6.325 = 513.2sq.m

WP = 6 * 12.19 + 5 * 1.60 + 2 * 6.325 = 93.79 m

R = 513.2/93.79 = 5.47 m

V = ( 1/ 0.03 ) * (5.47 ) 0.67 * ( 1 / 975 ) 0.50 = 3.32m/sec

HFL , Q = 0.9 * 6 * 12.2 * 6.325 * 3.32 = 1380 cumecsVC available ( DN ) = 25.475 25.225 = 0.250m < 1.50m ( Std VC )

Similarly HFL discharge of Br.No.240 ( exg 7 x12.20m GB ) = 1346.67cumecsTotal HFL = 1380 + 1346.67 = 2726 . 67 >> 1335 cumecsVC available ( DN ) = 25.860 25.575 = 0.285m

< 1.50m ( Std VC )


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Capacity of Br.No.239

( 6 x 12.2m ) GB & Br.No.240 ( 7 x 12.20m GB )Probable,HFL = 23.270 , BL = 18.900Depth of Flow , DF = 23.270 18.9 = 4.370m

WA =( 6 * 1.2.20 + 5 *1.60 ) * 4.370 = 354.58sq.mWP = 6 * 12.19 + 5 * 1.60 + 2 * 4.370 = 89.88 mR = 354.58 /89.88 = 3.945 mV = ( 1/ 0.03 ) * (3.945 ) 0.67 * ( 1 / 975 ) 0.50 = 2.67m/secQ = 0.9 * 6 * 12.2 * 4.370 * 2.67 = 767 cumecs

VC available ( DN ) = 25.475 23.270 = 2.20m > 1.50m ( Std VC )VC is available ( UP ) = 25.505 23.270 = 2.235mSimilarly capacity of Br.N0.240 ,Q = 0.9 * 7 * 12.2 * 3.300 * 2.26 = 573.60 cumecs

Total HFL = 767 + 573.60 = 1340 > 1335 ( Q 50 )

VC available ( DN ) = 25.860 23.270= 2.590m > 1.50m ( Std VC )VC ( UP ) = 25.800 23.270 = 2.530 > 1.50m ( Std VC )


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Catchment Area of tanks


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Flow pattern of Breached tanks


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Water way design of surplus weir for RAT

RAT Is a tank , a breach / damage / substandard

maintenance or an act of negligence or omission indue operation of which result in danger to anyrailway in the opinion of responsible railway officernot less than DEN.

Nemalla pudi Tank ( RAT ) Catchment area = 52.80 sq.m.Q 50 Discharge = 52.80 * 1335.43/ 250 = 278 cumecs.

Design depth of flow( H ) = 1.03 m = 1.03/0.305=3.37FT.Q = 2 * L * H 1.50 ( FPS units ).

Length of Weir required.L = 278 * 35.31 / ( 2 * (3.37 )1.50 ) = 790 ft = 790 * 0.305 = 240m.

Existing weir length = 42m.Hence Additional weir length is required.with 1.03m designed depth, 240 42 = 198m.


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Additional length of weir required


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Proposals & Conclusions1. Adequacy of waterway should be checked for all minor

bridges and major / important bridges, if it is affected by

RAT / RAW

2. The catchment area of RAT s and connected upper tanks

should be studied and length of surplus weir to be checked

for adequacy.

3. The ADEN in charge of the section should conduct joint

inspection with the engineers of state irrigation department

regarding the stability of bunds ,water way etc beforeonsoon as per guide lines specified in the relevant manuals

and codes.


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References

1. Flood Estimation Methods for catchments

< 25 sq.km in area ( RBF 16 ) by RDSO

2. Flood Estimation Report Eastern Coast Region

( Sub Zones 4 a,b, &c ) CWC and RDSO

3. IRS Code for sub structure and foundations

4. IRS Bridge Manual


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Acknowledgements

we are very much thankful to IRICEN Institute in

providing the well equipped library and computer centre as well as in the hostel premises also. For this we extend our sincere

thanks to the Director, IRICEN and faculty members.

We are very much grateful to our project guide shri G. Bansal , professor /Bridges, IRICEN ,Pune for his valuable

guidance in preparing the project work entrusted to us.

We extend our sincere thanks to the Chief BridgeEngineers office( Flood Section ) / Southern Railway and state

irrigation dept , GUDUR for providing us the records for the

case study.


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THANK YOU

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