Planning, Design, and Construction of
Bridge Over River Yamuna Near Geeta Colony, Delhi
The river Yamuna practically divides Delhi into two zones, namely Western Zone and Eastern Zone. Though geographically, major part of the territory lies on the western side of the river Yamuna, the eastern part of Delhi, popularly known as Trans-Yamuna, has nearly 25% of the population of Delhi with very high population density. The ever-increasing population on the Trans-Yamuna puts increasing pressure on the Highway Authorities to build number of bridges across the river, to meet the growing demand.
As on date (July 2008), 13 bridges exist in Delhi in between Wazirabad and Okhla and 3 more bridges are either presently under construction or in planning stage. The breakup of the 16 Bridges as per various Departments are as follows:
- PWD Bridges : 5 Constructed, 2 under planning stage
- DMRC Bridges : 2 Constructed
- Railway Bridges : 2 Constructed, 1 Underconstruction
- Haryana Irrigation : 2 Constructed
- UP Irrigation : 1 Constructed
- Noida Toll Bridge Authority : 1 Constructed
This road will connect Marginal Bund Pusta Road with Karkari Mode at Vikas Marg.
Starting right in front of Taj Enclave in Geeta Colony along the upcoming new eight-lane East Delhi Ring Road, the Geeta Colony Bridge will link East Delhi areas with Shanti Van where the bridge approach is planned to end. With a length of 560 metres for the main bridge and a cost of about Rs. 130 crores, the new link will greatly reduce the traffic congestion on ITO Bridge and Vikas Marg.
The administrative approval for the project was obtained on 10.07.2003 for an amount of 129.07 crores. Approval from Technical Committee of DDA was obtained on 11-03-2003. Comprehensive Security clearance from Delhi Police, Intelligence, Security and Operations was taken on 16-11-2002. Clearance from Yamuna Committee of CWC was taken on 06-6-2003.
The construction contract for this project was awarded to M/S Navayuga Engineering Co. Ltd. on 29.12.2004 for an amount of 99.765 rores. The construction period was allocated as 36 months. At the time of writing this paper (i.e. July 2008), the construction is almost nearing completion and the bridge is scheduled to be opened to traffic by the end of this month.
Constraints During Planning Stage
During the feasibility study stage, two alternative alignments were studied for the bridge:
- Shastri Nagar to Rajghat (Delhi Master Plan 2001 Alignment) [i.e. Rajghat Bridge Alternative]. The proposed alignment is 1.3 km u/s of the ITO Bridge.
- Raja Ram Marg to Shantivan [i.e. Geeta Colony Bridge Alternative]. The proposed alignment is 2.6 km from ITO Bridge and 1.3 km from Rail--Road bridge.
Being closer to the Rail--Road Bridge, the Geeta Colony Bridge alignment is found to be better located to handle traffic diverted from the ROR Bridge, should there be any restriction in ts use in future. Moreover, the Rajghat route would have had significant detrimental environmental impact on Rajghat and adjoining areas as it would require the upgrading of the tree-lined Rajghat road and will also lead to introduction of heavy traffic into this sensitive and calm area.
Approval from various agenciesBesides main waterway flowing channel of river Yamuna, lot of land had to be acquired from different government agencies, which required great effort & persuasion at different levels of the government. Details of land acquired for the bridge are:
- DDA for major part of bridge & western approach.
- Irrigation & Flood control department, Government of Delhi for part of Western Approach.
- Irrigation & Flood control department, Government of U.P for part of Eastern Approach.
- Delhi Police and U.P PAC : Police tents were removed for part of western approach near Shantivan.
Traffic Dispersal Scheme On Eastern & Western Banks
Figure 2 shows the ring road bypass alignment on the western side of Geeta Colony Bridge.
Eastern SideOn the Eestern side, a grade separator has been proposed connecting the bridge with the marginal bund road and ensuring completely signal free traffic. Figure 3 shows the proposed plan for the grade separator.
Salient Features of the BridgeLength of the Main Bridge is 560m. The bridge is having dual carriageways of 9m each (reduced 3 lanes each) with central median verge and footpath as well as cycle track on either side. The overall width of the bridge is 27.1m. The span arrangement for the bridge comprises 14 spans of 40.0m each. Expansion joints are provided at every alternate pier and at abutments. The two carriageways are structurally isolated and a longitudinal gap is provided at the centerline of the median along the entire length of the bridge. Figure 4 shows the General Arrangement of the Bridge
The Abutment on either side is provided as an RCC multicell box structure with intermediate stiffeners. Figure 9 shows Dimensions of RCC Cellular Abutment.
The bridge is connected on the western side (i.e. Shantivan side) by approach embankments approximately 1800 mtrs long. Figure 10 shows a Typical Cross Section of the Embankment Approach road. On the Eastern side (i.e. Geeta Colony Side), the original proposal was to connect the bridge to the existing bund road by approximately 540 mtrs long approach road. The cross section of the approach road is to provide dual carriageways of 9m each with central median verge and footpath as well as cycle track on either side.
Figure 9: Dimensions of Cellular Abuntment
Figure 10: Typical Details of Road Embankment
Hydraulic StudiesHydraulic Model studies were carried out for the bridge at Central Water & Power Research Station, Pune. 2 alternative alignments were considered for Model Studies.
Studies were undertaken by CWPRS on the existing river model constructed to a horizontal scale of 1:300 and a vertical scale of 1:60 covering a river reach of 29 km upstream and 21 km downstream of ISBT bridge. The model bed between Wazirabad Barrage and Indraprastha Barrage was moulded as per 1998 post-flood survey. Studies were carried out under existing conditions and with the bridge in position. Model studies were carried out under the following hydraulic conditions:
- Under existing condition.
- With proposed bridge in position with waterway of 560m, with double well piers, guide bunds, etc.
- With proposed bridge in position with waterway of 560m, with double well piers and with left and right guide bunds modified by CWPRS.
- 7,022 cum/sec (2.48 lakh cusecs) (maximum discharges observed in 1988 at Wazirabad barrage)
- 9,910 cum/sec (3.5 lakh cusecs) (design discharge considered for ISBT Bridge)
- 12750 cum/sec (4.5 lakh cusecs) (Check flood for substructure, foundation and protection works suggested by Central Water Commission.
- 14,866 cum/sec (5.25 lakh cusecs) (discharge considered for Delhi – Noida road bridge).
- The alignment of the bridge axis with its orientation making 1.4km and 2.0km on the right and left sides respectively downstream of the old rail-cum-road bridge is hydraulically satisfactory.
- The waterway of 560m (14 spans of 40m centre to centre) and the location of the left abutment 145m inside the river from left marginal bund are recommended.
- A water way of 560 m would cause an afflux of 15-20 cm at the proposed bridge axis. At the old rail--road bridge the afflux was reduced to 10-15 cm. That means the effect of afflux will not be going beyond old rail-cum-road bridge.
- On the right upstream side a guide bund of 218m long with curved head of multi-radii (220m and 90m) making an angle of 130° with the bridge axis. On the right downstream side a guide bund making an angle of 90° with the bridge axis having a length of 140m long followed curved tail of 120m radius. On the left upstream side a guide bund making an angle of 90° with the bridge axis having a length of 162m followed by a curved head of 96m radius upto the marginal bund. On the left downstream side a guide bund of 100m long making 100° with the bridge axis with curved tail of 120m radius. Figure 11 shows the details of Guide Bund.
- For the guide bund on river side along the right upstream guide bund beyond 150m from bridge axis and along the left guide bund 100m upstream and 90m downstream from bridge axis, a side slope of 1:2 and apron width of 45m should be provided. For the sloping portion of the river side, stones in crates of size 0.5m X 0.5m X 0.5m in one layer and for launching apron, stones in crates of size 1.0m X 1.0m X 0.75m in two layers were recommended. Protection materials are to be laid over geofabric filter. Over the geofabric filter, a 15cm thick layer of coarse sand should be provided before placing of stone crates to avoid rupture of geofabric material.
- The water levels for discharge of 12,750/s would be at RL 208.21m at the proposed bridge site and at RL 208.52m at old rail--road bridge. Hence considering a free board of 1.5m above water level of RL 208.21m observed at the proposed bridge site, the top level of guide bund and approach embankment could be 209.71m.
- The likely deepest scour level around the proposed bridge piers could be around RL 178.47m and may be considered for deciding the foundation level.
- No gap behind the left guide bund is advisable. The area could be filled up and brought to a level above HFL.
- Protection work for right approach embankment with a side slope 1:2 (on both sides) with top width of 40m having two layers of stones weighing 40-50 kg for the first 300m from right abutment, one layer of crates of 0.5m X 0.5m X 0.5m for next 400m (middle portion) and for remaining portion upto the marginal bund two layers of stones weighing 40-50 kg are recommended.
Geotechnical InvestigationsAt the proposed site 15 River bore holes and 8 land boreholes were drilled. River boreholes were 50m deep and were drilled at the proposed abutment and proposed pier locations. The land boreholes were 20m deep and were drilled for the proposed embankment.
River Bore HolesFrom the soil classification, it has been observed that the strata predominantly consist of non-plastic poorly graded sand and silty sand/ Sandy silt with traces of gravel upto the depth explored/refusal strata. However, layers of silty clay of low to medium plasticity of varying thickness were observed in some of the bore holes. Refusal strata (N>100) was observed in 6 bore holes with varying depths of 18m to 36m below the ground level. 4 bore holes were drilled under water. Beyond refusal the boreholes were advanced by hydraulic drilling machine upto 50m depth and representative samples have been collected. From the classification of the samples, it has been revealed that the strata beyond refusal predominantly consist of silty clay of medium plasticity. However, in 2 of the bore holes, sandy silt with gravel strata has been observed.
Silt FactorSilt factor was calculated using the following formula:
Ksf = 1.76 “m, Where, m = mean size particle in mm
m = 0.309.
The calculation revealed that silt factor within the anticipated scour depth is 1.02. This value has been considered for evaluating the scour depth.
Scour DepthDesign Discharge : 12,750 ecs (Based on Model Study Report) (check flood discharge for design of protection works, substructure etc.)
: 14,866 ecs (For design of Foundation only)
Effective linear waterway : 482.77m
Highest Flood level (affluxed) : 208.21 (Corresponding to discharge of 12750 ecs).
Maximum Scour depth below HFL : 178.47m (For piers–normal case)
: 181.44m (For piers–seismic case)
: 189.33m (For abutments–normal case)
: 191.22m (For abutments–seismic case)
Maximum Founding Level : 168.6m (For piers )
: 183.1m (For abutments)
Recommendations for Bearing CapacityFor the proposed Bridge Well Foundation of 8.0m diameter was analyzed at different founding levels the net Safe bearing pressure is given in the following table.
Land Bore HolesWhile advancing the boreholes, SPT tests were conducted at regular interval of 1.5-m depth and representative samples were collected and analyzed for soil classification. From the soil classification, it has been observed that the strata predominantly consist of non-plastic poorly graded sand and silty sand/Sandy silt with traces of gravel upto the depth explored. However, layers of silty clay of low to medium plasticity of two meter thickness were observed in 2 bore holes.
For the proposed 10m height embankment with base width of 50m and top width of 30m a safe bearing pressure of 18t/m2 is recommended at cutoff level of abut 2.0m below the ground surface for an allowable settlements of 218mm and 204mm at centre and edge of embankment respectively.
- The design of foundation is governed by the horizontal forces caused by braking, seismic bearing restraint, wind etc. Since this bridge is located in Delhi, which is seismically an active zone, the earthquake forces are most critical. In case of pile foundation, the free standing length of the piles during scour is likely to be about 20m, for which piles of diameter 1.5m or more is only considered suitable. There are only few contractors in India having experience of constructing large diameter piles in river.
- The technology for construction of large diameter deep bored pile foundation reliably in difficult site condition (such as deep water, fast following river) is limited in India. In contrast, the technology of constructing will foundation is well established.
- It is difficult to reliably establish the load carrying capacity of piles in scourable rivers. This is due to the fact that the scour condition can never be simulated during the load testing of piles.
- Floating debris during floods is high and vibration phenomenon of pile clusters. This aspect has not been studied adequately in India so far.
- In case of pile foundation, considering the large diameter pile and scour depth of 20m, a permanent liner of 6mm/8mm would have been required at least upto the scour level. The cost of piling with liner and with the high technology piling equipment would not have been lesser than the well foundations.
- The hydraulic model study carried out by M/s CWPRS for this bridge considers well foundation for model study. The recommen–dations of M/s CWPRS on scour depth, founding level, guide bund geometry, launching apron details and river protection works, has been followed in the stage design /drawings. Any change in the type of foundation after carrying out model study would not be desirable.
- All existing bridge across river Yamuna in Delhi, except the Delhi –Noida Tollway Bridge, are resting on well foundation. The practice and precedence in this case is therefore in favor of well foundation rather than pile.
- Clause 4.1 of the IRC:SP33-1989 (Special publication titled “Guidelines on Supplemental Measures for Design, Detailing and Durability of Important Bridge Structures”) clearly states that “Pile foundation shall not be accepted within the flood zone of the river with deep scour.”
Photo 1: Sinking of Well Foundation in progress
Photo 2: Bottom Plugging of Well Foundation in progress
The well foundation is designed as per conventional methods. The design of pier well foundation as well as abutment well foundation is carried out as per the provisions of IRC:78-2000. Since the abutment well is protected from scour by guide bund, the scour level for the purpose of design of abutment well is considered as the bottom of well cap. A tilt of 1 in 80 and a shift of 150mm for the well in the resultant direction of force has been considered in the design as per the code.
Photo 1 & Photo 2 show the sinking of well foundation in progress.
SuperstructureThe superstructure of the bridge is conceived as a 2 span continues structure with the continuity established through deck slab only. Expansion joints are provided at a spacing of 80m. Precast post tensioned girders chosen in order to speeed up the construction work at site. casting of 140 precast girders for the main bridge has been done simultaniously when well sinking was going on at the river bed.
Full continuity (i.e. continuity through deck slab as well as diaphragm), though considered a better structure system as compared to only deck continuity, it was ruled out for this bridge since the sub-soils strata showed presednce of clay layer, indicating possibility of large settlement(i.e. upto 75mm) that can be expected in foundations. Full continuity would have meant lager forces to be attracted by the Superstructure due to differential settlement between adjacent foundations.
The sequence of construction for a typical continuous unit is as follows;
- To cast precast prestressed girder on casting yard, placed behind shantivan side abutment.
- To prestress 1st stage cables in the casting bed and shift the girder to stacking yard.
- To launch the precast girder inposition.
- To cast deck slab over the precast girder by taking support from the launched girder.
- To prestress 2nd stage cables.
- To cast the railing, crash barrier & wearing coat over the girder, excluding the deck continuity portion.
- To cast the continuity slab between the girders.
- To cast the railing, crash barrier & wearing coat over the deck continuity portion.
Design Live LoadFor the 9.0m carriageway, the number of lanes for the design purpose shall be taken as 2 as per IRC:6-2000. One lane of Class 70R or one/two lanes of Class A whichever produces greater results shall be considered in such case.
The bridge has also been checked for carriageway width of 12.45m assuming that the crash barrier may be removed in future and the entire deck will become a wide carriageway. In such situation, the number of lanes for the design purpose shall be taken as 3 as per IRC:6-2000. One lane of Class 70R with one lane of class A or one/ two/three lanes of Class A whichever produces greater results has been considered in this case.
BearingsSelection of the bearing type and finalization of bearing layout in a continuous structure is one of the most important task, which is required to be established during the initial conceptual design process itself since the layout of bearing has significant influence on the structural system. Analysis of the whole structure and transfer of forces in the substructure and foundation largely depends upon the bearings arrangement.
The bearing arrangement for a typical two span continuous unit of this project is shown in Figure 12.
Expansion JointsModular Expansion joints (with 2 modules) have been used for all the intermediate pier locations. At the abutments, single strip seal type expansion joints have been used.
Launching & Erection Scheme for Precast GirderA unique scheme of launching and erection of the precast post tensioned girders has been adopted for this bridge. Instead of the conventional launching truss/ launching girder, which moves over the constructed piers/abutments, the proposed scheme involves moving the girder on the river bed itself. The girders are cast in the casting yard, which is located just behind the shantivan side abutment. The level of the casting yard has been kept above HFL so as to ensure that the precasting works are unaffected during the monsoon season.
Figure 13: Layout of Precasting Yard & Lowering Station for Launching of precast Girder
Figure 14: Erection of Precast Girder with Lifting Beam
From the pre-casting yard, a trolley track (rail track) will be laid parallel to centre line of the bridge axis at the casting level as well as at the river bed level. The girders are lowered to the river bed level first at the designated lowering station, in the first span and then moved along the river bed to the location. Steel trolley on rail will carry the pre-cast girder to its location where the girder is to be lifted. The pre-cast girder will be handled by means of hoisting frame with mechanical/hydraulic devices, and placed in its position. The hoisting frame will take support from the pier cap at one end. Figure 13 shows the plan of precasting yard and lowering station. Figure 14 shows the erection of precast girder with lifting beam.
Photo 3: Precast Girder lowered to Transport trolly at the casting Yard
Photo 4: Precast Girder moved from casting yard to lowering station
Photo 5: Precast Girder lowered to river bed at lowering station
Photo 6: Precast Girder moved to the location on rails over river bed
Photo 7: Girder lifted up from the trolly
Photo 8: Girder Erection in progress with lifting beam & Hoisting Frame
Photo 9: All Girders in a span erected in position
Photo 3 to Photo 9 show the launching and erection scheme used for the precast post tensioned girders in this project.