Construction of Bridge Over Major River Naodhing

8/10/2019 Construction of Bridge Over Major River Naodhing

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Paper No. 503 +

CONSTRUCTION OF 637.6 METRES BRIDGE OVERRIVER NAODHING ON NH-52 IN ARUNACHALPRADESH : A CHALLENGE ACCOMPLISHED

By

T.P. V ELAYUDHAN , VSM 1, B.K. B ASU , SC, VSM 2 ,S. R OY CHOWDHURY , VSM 3, A.K. G UPTA 4 & D.D. S HARMA 5

CONTENTSPage

1. Introduction ... ... 3282. Behaviour of River Naodhing ... ... 3293. Bridge Scheme ... ... 3324. Construction Progress ... ... 3395. Problems Encountered during Construction ... ... 3446. Conclusions ... ... 355

SYNOPSIS

The Naodhing River has been a great obstacle in Socio-economic development of Lohit District of Arunachal Pradesh. Since time immemorial, the river was being crossedthrough power/man driven boats for communication between south bank of Lohit Districtand rest of the country. During the floods, even these boat crossing were not possibleand communications used to remain cut off for days together. Moreover during monsoon,the approaches to ferry ghat also remained slushy and it became extremely difficult topass through without 4 x 4 vehicles. The people of Arunachal Pradesh residing in theLohit district faced innumerable problems while crossing the river Naodhing at ferry ghat.

They had to walk kilometers in slushy and unsurfaced track and then kept on waitingfor long hours for ferry arrival which again depended on clear weather conditions/ discharge of river. All these inconveniences and difficulties did have a strong bearing oneconomic activities on the other side of the stream by way of insufficient goods flow,

+ Written comments on this Paper are invited and will be received upto 31st December2004

1 Addl. DGBR, HQ DGBR, New Delhi2 Ex ADG (BRO)3 Deputy Director Gen. (Brs), HQ DGBR, New Delhi4 EE (Civil), Officer Commanding, 51 R.C.C. (GREF)5 Proprietor, M/s. D.D. Sharma, New Delhi


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VELAYUDHAN , B ASU , C HOWDHURY , G UPTA & S HARMA ON328

sky rocketing prices of essential commodities and slow pace of the developmental

activities.

This Paper highlights as to how the construction of Naodhing bridge was undertaken,listing out the various difficulties faced during its execution. The construction of thisbridge has greatly changed the life style of the people and hastened the developmentalprojects across the river. Administrative supervision now has become all the more easierand effective. Now people can plan their movement to places like Guwahati, Tezpur,Itanagar etc. directly from Tezu/Wakro/Namsai. The prices of essential commodities havealso come down substantially and thereby further improving the living conditions of the

people.

1. INTRODUCTION

1.1. Construction of bridges in North - East India has always posedchallenges to the bridge Engineers. Instances of late commissioning of bridgeprojects due to various constraints resulting in abnormal delays are verycommon. The various constraints, common in this region are lack of trained

man power and essential bridging stores, lack of adequate machineries, limitedworking period and unexpected flash floods causing meandering of river,excess discharge, difficult accessibility to bridge site, administrative and securityconcerns.

1.2. Selection of bridge site in meandering channels has a greaterinfluence on the bridge cost as the additional bridge length increases thebridge cost. The concept of least bridge length with river training works is

the most economical solution for the rivers flowing in alluvial plains. However,the time gap between conceptual bridge scheme stage and its actual executionon ground can rarely be synchronized. Changes in the river course before,during and even after the construction of bridge in the North East region arecommon. This can be attributed to the flash floods in the upper reaches of the catchment area. This phenomenon has not only caused far reachingdamages resulting in time and cost over run of the bridge projects but alsoput the credibility and esteem of the engineering fraternity at stake. Forexample, the permanent bridge constructed over river Gai on NH-52 in Assamis in redundant state now, as the course of the river has changed completelyand the bridge is out flanked.

1.3. The progress of the construction of the bridge on river Naodhingin Arunachal Pradesh also retarded due to meandering of the river leading toincrease in the bridge length. The original proposed length of the bridge of 271.20 m, had to be increased to 637.60 m in stages. Inspite of this abnormalincrease in bridge length, the bridge was completed in a record period of 24working months. The paper highlights the various problems encountered andexperiences gained during the course of construction of the bridge.


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CONSTRUCTION OF 637.6 M ETRES B RIDGE O VER R IVER N AODHING ON NH-52 INARUNACHAL PRADESH : A C HALLENGE A CCOMPLISHED

329

2. BEHAVIOUR OF RIVER NAODHING

The Naodhing river catchment covers Poorvanchal range of mountainsin the far east of India and Myanmar. It enters India through the border townof Vijayanagar in the Changlang District of Arunachal Pradesh and bifurcatesinto two channels near Manabhum. The Old channel of this river is calledBuridihing and the new one Naodhing. Riverbed material is mostly boulderyat Manabhum and alluvial in nature at Naodhing bridge site. The river has atendency of meandering due to low lying and undefined banks. Before the

construction of the bridge across this river, the ferries and country boats werethe only means of crossing. Every year loss of life/materials/equipment usedto occur at the ferry crossing. During the floods the area remained cut off fordays together. The detailed investigations of the bridge site were carried outand the bridge site was selected two kms upstream of the ferry point whichoffered a firm bank on Mahadevpur and Namsai sides.

2.1. The original flow pattern of the river is marked in Fig 1.. ArunachalPradesh State Irrigation & Flood Control Department (I&FCD) had constructedearthen bunds to protect the flooding of low lying areas of Namsai andMahadevpur townships during monsoons. The detailed survey and subsoilinvestigation for the bridge was carried out in the year 1993. The actualconstruction of the bridge started in Jan 1996 and by then the river hasalready eroded the banks by 25 m on Mahadevpur side and 40 m on Namsaiside. The bridge length had to be revised to 341.40 m from original length of 271.20 m by adding one span of 25 m on Mahadevpur side and another spanof 45.2 m on Namsai side. The length of the bridge was increased mainly tofacilitate the construction of the guide bunds on high banks in view of thevery short working period of completion of the guide bunds within oneseason.

2.2. During the floods of 1997-98, the partially constructed guidebund on Mahadevpur side protected the approach road, even after washing

away of the earthen bund on upstream of the bridge. However, 74 m lengthof this bund was damaged and heavy bank erosion took place on Namsai sidebank along the bridge axis. The river started changing course and the flowpattern developed tendency of meandering near the bridge site. The problemwas referred to the ministry of Road Transport & Highways (MORT& H) anda High Level Committee was setup by the MORT & H consisting of seniorofficers of BRO, MOST, Brahmaputra Board and I & FCD Arunachal Pradeshto analyze the problem. The Committee in its report opined that the discharge

had not been properly analyzed earlier and that the actual discharge passingwas much more. The detailed calculations of the revised discharge phenomenonas given in Table 1 indicates that the river Buridihing was carrying much less


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F i g . 1 .


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331

T A B L E - 1 . D

E S I G N D I S C H A R G E , L A C K E Y L I N E A R W A T E R W A Y , N

O R M A L S C O U R D E P T H A N D M A X I M U M S C O U R D E P T H B A S E D O N D E S I G N E D H E L A N D

A C T U A L F L O O D L E V E L O F N A O D H I N G R I V E R A T B R I D G E A X I S

1 .

A p p r o x i m a t e

C r o s s

S e c t

i o n a r e a a t

B r i

d g e

A x i s w

i t h c h a n g e d c r o s s s e c t

i o n a n

d 1 4 5 . 8 0 m

d e s i g n

H F L

, A d

= 2 9 0 8 m

2

A p p r o x i m a t e

C r o s s

S e c t

i o n a l a r e a a t

B r i

d g e

A x i x w i t

h c h a n g e

d c r o s s s e c t

i o n a n

d 1 4 4 . 5 0 m o b s e r v e d

f l o o d l e v e

l ,

F l o o d

L e v e l

X - S e c

M e a n

D i s c h -

L a c e y

N o r m a l

M a x

M a x

M a x

S c o u r

D e s

i g n

A r e a

D e s i g n

a r g e

w a t e r

s c o u r

s c o u r

s c o u r

s c o u

r

L e v e l

R L

S c o u r

A

v e l o c i t y

Q

w a y

d e p t h

d e p t h

d e p t h

d p e t h

w i t h

l e v e l R L

( m 2 )

V

( m 3 / s )

W

d

2 d

w i t h

w i t h

4 7 7 m

( m )

( m

/ s )

( m )

( m )

( m )

3 4 1 . 4 0 m

4 7 7 m

l e n g t h

s p a n

s p a n

2 d 1

2 d l

( m )

( m )

1

2

3

4

5

6

7

8

9

1 0

1 1

A t D e s i g n

H F L

2 9 0 8

. 0 0

3 . 0

0

8 7 2 4

. 0 0

4 4 3 . 6 6

9 . 0 0

1 8 . 0

0

2 1 . 7

0

1 3 . 0 0

1 3 2 . 0 0

1 3 1

. 0 0

1 4 5 . 8 0 m

A t O b s e r v e

d

1 8 2 9

. 0 0

3 . 0

0

5 4 8 7

. 0 0

3 5 2 . 0 0

7 . 6 7

1 5 . 3

4

1 6 . 0

0

1 3 . 3 5

1 3 0 . 6 7

1 3 1

. 0 0

F l o o

d L e v e

l

1 8 2 9

. 0 0

3 . 5

0

6 4 0 1

. 5 0

3 8 0 . 0 0

8 . 0 0

1 6 . 0

0

1 7 . 6

6

1 4 . 7 8

1 2 9 . 2 2

1 3 1

. 0 0

1 4 4 m

1 8 2 9

. 0 0

4 . 0

0

7 3 1 6

. 0 0

4 0 6 . 0 0

8 . 4 7

1 6 . 9

4

1 9 . 3

3

1 6 . 1 6

1 2 7 . 8 4

1 3 1

. 0 0

2 .

C o n s i

d e r i n g

E x t e n s i o n o f

T h r e e

S p a n o f

4 5 . 2

0 m

E a c h i . e

. 1 3 7 . 6 0 m r e v i s e

d l e n g

t h o f

b r i d g e s c

h e m e c o m e s

t o 4 7 7 m .

3 .

L a c e y w a t e r w a y

W

=

4 . 7 5 ( Q ) 1 / 2

4 .

L a c y

N o r m a l s c o u r

d e p t

h

D

=

0 . 4 7 ( Q / f ) 1 / 3

5 .

N o r m a l

S c o u r

d e p t

h w

i t h r e s t r i c t e d w a t e r w a y ,

d 1

=

1 . 3 5 ( q / f ) 1 / 3

w h e r e ,

q

=

Q / L

L

=

L e n g t

h o f r e s t r i c t e d w a t e r w a y

F

=

1 . 2 5

, s i

l t f a c t o r c o n s

i d e r e d

f o r

f o u n

d a t i o n

d e s i g n

R e m a r

k s :

I t c a n

b e s e e n

f r o m

t h e

a b o v e

t a b l e

t h a t

t h e w e l l

f o u n

d a t i o n a l r e a d y c o m p l e t e d c o n s

i d e r

i n g s c o u r

l e v e l

A t R L 1 3 1 . 0 0 m a r e s a

f e i n s c o u r i n g w

i t h 4 7 7 m

b r i d g e

l e n g

t h a t

d e s i g n

d i s c

h a r g e

8 7 2 m

3 / s a n

d m e a n .

V e l o c

i t y 3 m

/ s


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discharge and main flow in Naodhing channel of the river Buridihing had

merged with Naodhing. The reason for this increase in discharge wasattributed to the silting up of the Buridihing channel. After analyzing theproblem, the Committee recommended further extension of the bridge onNamsai side by 135.60 m (3x 45.20 m), construction of guide bund onMahadevpur bank, spurs on Namsai side bank and repelling spurs upstreamof the bridge site. The Committee also recommended further observation of the flow of the river.

2.3. The revised bridge scheme 477 m long, proposed spurs and theerosion occurred during the floods of 1997-98 are shown in Fig. 2.

2.4. During the monsoon of 1998-99, the Namsai bank got furthereroded by another 135 m along bridge axis and there was heavy siltdeposition on u/s of the bridge axis where the Brahmaputra Board hadproposed spurs. After due consideration and in view of the immediatethreat to the Namsai township, Ministry of Road Transport & Highways

revised the bridge scheme by adding another four spans on Namsai side(3x45.2+25) and extended the straight length of Namsai side Guide Bundby 140 m on the down stream side. it was also decided that the Namsaiabutment be designed as abutment cum pier to cater for any futureextension of the bridge and further increase in length during the servicelife of the bridge.

3. BRIDGE SCHEME

3.1. Initially after extensive survey and detailed study of the river,a 271.20 m long bridge (6x 45.2 m ) and 492 m long guide bunds oneach bank was finalized in 1988-89. The properties of soil, foundinglevels, bearing capacity etc. ascertained from the SSI and subsequentchanges made in the founding levels are given in Table 2. Proposedbridge scheme and bore log data are shown in Figs. 3(a) & 3(b). Theinitial bridge scheme accepted by the department is shown in Fig. 4. Dueto changes in the river behaviour and bank erosion during subsequentyears, the bridge length was revised to 637.60 m and Namsai side guidebund was extended by 140 m on the down stream side. The plan of therevised bridge scheme, GAD and soil strata actually obtained at abutmentA1 location are shown in Figs. 5 and 6 respectively.

3.2. Properties of soil at the foundation level were as under:-

(a) Bulk density of the material - 1.8 t/m 2

(b) Angle of international friction - 34 0(c) Angle of wall friction - 20 0

(d) Submerged density - 1.0 t/m 2


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333

F i g . 2 .


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T ABLE -2. S OIL B EARING C APACITY AND F OUNDING L EVEL

Structure Founding Level RL in M Bearing Capacity atFounding Level

Initial Proposal Revised As per SSI RevisedProposal Report

Abutment A1 133.20 122.50 60 t/m 2 50 t/m 2

A2 120.00 122.50 60 t/m 2 50 t/m 2

Piers P1 125.40 122.50 60 t/m 2 50 t/m 2

P2 123.80 122.50 60 t/m 2 50 t/m 2

P3 120.00 122.50 60 t/m 2 50 t/m 2

P4 120.00 122.50 60 t/m 2 50 t/m 2

P5 120.00 122.50 60 t/m 2 50 t/m 2

Fig. 3 (a)


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335

DETAILS OF BOREHOLES

Fig. 3. (b)


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Fig. 4. Initial Bridge Scheme for 271.2 m long NaodhingBridge as proposed in CA based on SSI Report


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Fig. 6. SOIL PROFILE (Actually Obtained)All Dimmensions in mm


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339

3.3. Salient features of the revised bridge scheme are as under :-

(a) Length of bridge : 637.60 m(b) Span arrangements : 13 x 45.2 m +

2 x 25 m(c) Type of superstructure : PSC Box Girder &

RCC box girderfor end spans

(d) Type of foundation : Well

(e) Overall depth of girder : 3.0 m(f) Carriageway width : 7.5 m(g) Width of foot path : 1.5 m(h) Design discharge and velocity :

(i) Initial as per SSI report : 4766 m 3 /s(ii) As per Committee report : 8724 m 3 /s(iii) Velocity : 3.02 m/s

(i) Silt factor : 1.25(j) Safe bearing capacity at founding level : 50 t/m 2(k) Highest flood level : RL 145.80 m(l) Low flood level : RL 140.24 m(m) Founding RL of abutments and piers : RL 122.50 m(n) Deck level : RL 151.00 m(o) Number of pres tress ing cables in main spans : 13(p) Prestressing system : 12 T 13(q) Type of anchor : Usha Ismail(r) Sheathing pipe : 72 mm dia bright

metal(s ) Concrete mix

(i) Steining : M 25(ii) Substructure well curb and well cap : M 35(iii) Superstructure : M 35

4. CONSTRUCTION PROGRESS

4.1 Construction of bridge: Construction of the bridge startedin January 1996 and was completed in June 2002. The working periodavailable was approximately 4 months (mid November to mid March)every year. The reduced period of construction was offset by workinglate in the night. The year wise linear and cumulative progress of variousactivities are given at Fig. 7 and Fig. 8 and yearwise progress is shown

in Fig. 3.


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Fig. 7. Year wise progress 637.60 m long Naodhing bridge onNH-52 in Arunachal Pradesh

@ Cumulative progress in m = (Cost of executed work in the year) x Total length of bridge (637.60m) Total cost of work

Fig. 8. Comulative progress year wise of 6.37-60 m long Naodhing Bridge onNH-52 in Arunachal Pradesh

160140120100

80604020

0 86-97 97-98 98-99 99-00 00-01 01-02

PERIOD

P R O G R E S S I N M E T R E

4.2. Construction of guide bund on Mahadevpur side bank wastaken in the year 1998 and on Namsai side bank in the year 2001. Thedesign of Mahadevpur side guide bund was restricted as the guide bundwas to be made on the riverbank. Namsai side guide bund was designedas per IRC-89. The length of the guide bund was 632 m (140 + 492). Cross-sections of the guide bunds are shown in Figs. 9 and 10.


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341

T A B L E - 3 . Y E A R W I S E C O N S T R U C T I O N O F F O U N D A T I O N S / S U B S T R U C T U R E / P I E R S H A F T N A O D H I N G B R I D G E

S r .

N a m e o f

1 9 9 6 - 9 7

1 9 9 7 - 9 8

1 9 9 8 - 9 9

1 9 9 9 - 2 0 0 0

2 0 0 0 - 0 1

N o .

F o u n d a t i o n

D t . o f s t a r t

D t . o f C o m p l n .

D t . o f s t a r t D

t . o f c o m p l n .

D t o f s t a r t

D t . o f c o m p l n .

D t . o f s t a r t D t . o f c o m p l n .

D t . o f s t a r t

D t . o f c o m p l n .

S u b s t r u c t u r e

1 .

A 1 R

1 6 . 0

2 . 9 8

2 2 . 1 2 . 9 8

2 .

A 1 P 1

2 9 . 1

0 . 9 6

2 6 . 0

2 . 9 7

3 .

P 1

2 6 . 1

1 . 9 6

2 5 . 0

2 . 9 7

4 .

P 2

3 0 . 1

1 . 9 6

0 4 . 0

3 . 9 7

5 .

P 3

0 5 . 1

1 . 9 6

0 9 . 0

3 . 9 7

6 .

P 4

1 6 . 0

1 . 9 7

1 3 . 0 2

. 9 8

7 .

P 5

0 8 . 1

2 . 9 7

3 0 . 1 1 . 9 8

8 .

P 6

0 7 . 0

2 . 9 8

2 1 . 0 2 . 9 9

9 .

P 7

2 0 . 1

1 . 9 8

2 0 . 0 3 . 9 9

1 0 .

P 8

0 3 . 0

2 . 9 8

1 8 . 1

1 . 9 9

1 1 .

P 9

2 6 . 1

1 . 9 9

1 3 . 0

3 . 2 0 0 0

1 2 .

P 1 0

1 9 . 1

2 . 9 9

2 1 . 1 2 . 2

0 0 0

1 3 .

P 1 1

3 0 . 1

1 . 2 0 0 0

2 3 . 0 3 . 2

0 0 1

1 4 .

P 1 2

0 6 . 1

1 . 2 0 0 0

1 9 . 0 2 . 2

0 0 1

1 5 .

P 1 3

2 7 . 3 . 2

0 0 0

1 6 . 0 3 . 2

0 0 1

1 6 .

A 2 R R R

1 5 . 3 . 2

0 0 0

1 1 . 0 3 . 2

0 0 1


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PLAN AND CROSS SECTION OF GUIDE BUND OVER

RIVER NOADHING NAMSAI SIDE BANK

Note: All Dimensions in meters unless specified otherwise

Fig. 9.


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343

PLAN AND CROSS SECTION OF GUIDE BUND OVERRIVER NOADHING MAHADEVPUR SIDE

Note: All Dimensions in meters unless specified otherwise

Fig. 10.


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I tem Unit Quan i ty Item Unit Quanti ty

STEEL

25 mm M T 164.185 Concrete m3

1857420 mm M T 365.230 Aggregate m 3 1634516 mm M T 357.890 Fine Aggregate m 3 780112 mm M T 251.680 Cement M T 801310 mm M T 121.140 PC strand M T 14008 mm M T 22.610 Drainage Spout Nos. 22406 mm M T 17.930 Expansion Joint Nos. 5 6Binding wire M T 150.000 PTFE Bearing Set 1 6Total MT 1450.000

T ABLE -5. Q UANITY I NVOLVED IN THE C ONSTRUCTION OF THE G UIDE BUNDS

Mahadevpur Unit Quanti ty Namsai side Uni t Quanti tySide Bank Bank

Excavation m 3 31597.00 Excavation m 3 20658.00Filling m 3 5399.31 Filling m 3 24475.00Turfing m 2 6130.00 Filter Media m 2 14400.00Filter Media m 2 12098.80 Turfing m 2 6000.00Boulder Filling m 3 14000.00 Boulder Filling m 3 22750.00

5. PROBLEMS ENCOUNTERED DURING CONSTRUCTION

5.1. Shifting of Stores through Ferry

Since there was no bridge available to cross the river and work wasto be carried out from both the banks, all stores were transported throughferries during the monsoon period and through temporary timber bridgeduring the working period. The charges for ferrying the loaded truck wereexorbitant. Besides, the loaded trucks had to wait for long periods dueto local disturbances.

5.2. Obstruction of wells due to presence of Embedded Wooden Logs

The soil strata at bridge site was fine to coarse sand with anintermediate layer of stiff clay at about 7 m below LWL in few wells. The

4.3. Major stores utilized for the construction of the bridge and

the guide bunds are given in Tables 4 and 5. The volume of work and itsexecution in a total period of 24 months itself is a proof of the speed withwhich this bridge was completed.

T ABLE -4. Q UANTITY UTILIZED FOR B RIDGES


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345

sinking of wells was problematic due to buried roots of trees etc. at

regular intervals and in all the wells. The sizes of the logs were so hugethat it was not possible to remove them without cutting. Heavy chisel of ISMB-600 welded with 20 mm thick steel plate was fabricated to facilitatecutting of these logs. Water jetting and open excavation had to beresorted to expose the logs before the commencement of cutting operation.

5.3. Sand Blow During Sinking

Sand blowing at the final stages of sinking disrupted the progressconsiderably. The problem of sand blowing was tackled by usingconventional method of putting Jhar-Jhankar around the periphery of thewell and tilt rectification was carried out by controlled grabbing of thedredge holes in chosen areas in the well pocket.

5.4. Disruption of Works due to Rain

Untimely low intensity rain fall in the catchment of river Naodhingused to raise the water level in the river which some times inundated themake shift approach roads in the river bed thereby causing problems inshifting the construction stores to the work site. Not more than 120working days were available each working season. Work used to bestarted after 2 nd week of November each year and all works in the riverbed completed. The equipments etc. had to be removed by the middle of February during the succeeding year.

5.5. Recovery of Lost Curbs of Pier P-13

Sinking of pier well P13 was the most difficult since the pier locationwas coming in the deep water channel. After the casting of well curb,flood occurred and no further progress could be achieved. After recedingof flood, the curb was not visible and it was found that it had sunk by

3 m with considerable tilt.

5.5.1. To retrieve the curb, a coffer dam using wooden piles andsand filled polythene bags was made. By dewatering and manual removalof the deposited sand, well curb was retrieved and the top of the wellcurb was cleaned. The well curb reinforcement bars were cleaned andfalse steining of 3 m height was cast, leaving a gap of 15 cm all aroundfor putting up support to avoid further sinking of the well curb before

proceeding with casting of steining.


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PHOTOGRAPHS 1 TO 20 SHOWS VARIOUS ACTIVITIES

DURING EXECUTION OF THE PROJECT

Photo 1. Placement of well curb showing cutting edge and reinforcements

Photo 2. Logs being removed from the well P4


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347

Photo 3. Logs and stumps removed from P13

Photo 4. Logs removed from well P12


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Photo 5. Kentledge on the well to correct tilt and log being

removed from Well P9

Photo 6. Kentledge on the well P12 after the removal of the log(lying beside the well)


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349

Photo 7. Stump of the tree being removed from Well P10 (Logs were removed

from almost all the 16 wells during the process of well sinking)

Photo 8. Piling work in between spans for placing staging for thesuperstructure. Staging to be erected subsequently


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Photo 9. Acrow staging being erected for superstructure

Photo 10. Fabrication of cables and erection of staging etc. both acrow andtimber staging was used. Well Sinking work is also shown in the

background. Well Sinking, substructure and superstructure workprogressed simultaneously economizing the labour cost


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351

Photo 11. Box girder reinforcements showing cable ducts

Photo 12. Completed piers facing the full fury of floods

Photo 13. Mutlipull Jack 12 T 13 being used to prestress the cables of thesuperstructure


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353

Photo 17. Final Location of Abutment A1 R showing the A1 P (earlier abutmentalong with other spans). For Mahadevpur side

Photo 18. View of the Mahadevpur side guide bund (U/S)


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Photo 19. Inspection of the bridge by DGBR & C.E. (P) Udayak

Photo 20. Completed view of the bridge

5.5.2. Kentledge load with filled sand bags was placed on the wellsteining on the opposite side of the tilt and grabbing operation wascarried out from the same side. The well was brough within the permissiblelimit of tilt and shift. It took approximately 45 days for all these operations.The well was then sunk to the designed foundation.


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355

6. CONCLUSIONS

6.1. In the selection of the bridge site, the sequence of activity be asfollows:

(i) Finalization of the hydraulics of flow.(ii) Finalization of the bridge scheme alongwith the geometrics of the

approaches and the protection works like the guide bund andslope protection etc.

(iii) Physical construction and completion of the protection work of the both/either banks as the need may be.

(iv) Early commencement of construction of the bridge structure afterapproval of bridge scheme.

6.2. The construction of bridges in North East India requires specialattention with regard to selection of site and construction methodology.Completion of Naodhing I Bridge across Naodhing River in a record periodof 24 working months period was possible because of quick decisions, bettermanagement of resources and construction activities. The completion of this

bridge is a land mark achievement and has connected Prashuram Kund afamous pilgrimage centre on the bank of Lohit River.

6.3. As far as possible, river training works should not be done inphased manner and should be undertaken on both the banks simultaneously.It is also suggested that the construction of piers near to the river banksshould be undertaken after the completion of the river training works only.The problem of washing away of approaches embankment and extension of bridge can be minimized to a certain extent if these measures are given dueconsideration while constructing bridges in alluvial rivers.

6.4. The construction of the entire bridge length of 637.60 m couldbe started in one phase instead of the three phases as had to be resortedto in the present. The speed of construction could have definitely beenfurther accelerated reducing the time of completion. Further the type of superstructure could have been so chosen that work could be done duringthe monsoon. By proper advance planning, the time of completion and theresultant cost could have been further reduced.

6.5. For the original length of the bridge of 271.20 m, the piers werecylindrical and work was executed accordingly. However, with extension of the abutment on Mahadevpur side, the return walls of A1, P1 were dismantled,and the weep holes were used for providing shear connectors and jacketingthe abutment to convert it into the pier for supporting the end span of 25m. Accordingly for better aesthetics, all constructed piers were jacketed and

made rectangular with suitable cut waters. If the entire length of the bridgecould have been completed in one operation, this retrofitting could havebeen avoided. This is one more reason why the construction of the bridgestructure should proceed the construction of the protective works.

Documents

Construction of Bridge Over Major River Naodhing