The Mighty Brahmaputra
There are a lot of legends and prophesies floating with the current of the mighty Brahmaputra River as it tracks its course from Tibet to Bangladesh, roaring down through narrow chasms and gobbling up land in its pursuit to reach the sea. A river as wide as an ocean, blood red with stories of sacrifice and patricide, unusually for a river it is male in its aspect, and unusually for India, it is not a holy river but often referred to as the Old Man River.
The Brahmaputra is not a river that can be tamed easily; it is a river that demands respect and submission. Indeed, rare to find a reference to this river without the adjective "mighty' attached to it. In Tibet, where the river leaps to freedom from the great glacier mass of the northern-most chain of the Himalayas, it is known as Tsangpo, meaning 'purifier'. Sweeping and leaping through chasms, plunging through narrow valleys and collecting various tributaries along the way, the river twists and turns and executes hairpin bends before it spills into the North Eastern states of India. Here, the river collects the Dhanasri River and becomes the Brahmaputra, son of Brahma. Rolling into the alluvial plains of Bengal, the Brahmaputra rushes to meet the River Goddess Ganga. United, they dissolve into each other and spread fingers into the Bay of Bengal, feeding and destroying the fragile river islands that exist in the area known as the Sunderbans.
Bridging the Brahmaputra has always been a daunting task. The river has been traditionally considered extremely difficult for bridging due to various reasons including its ferocious and unpredictable behaviour, high currents and turbulent waters, widespread erosion of the banks, very short working period, and high seismicity and remoteness of the area.
With a width ranging from 1.2 km to 18 km, the Brahmaputra river has been bridged four times in the past. HCC holds a distinction of building two of these bridges and has recently completed construction of the 5th bridge at Bogibeel, near Dibrugarh.
Saraighat Bridge in Guwahati was the first rail-cum-road bridge over the mighty Brahmaputra river in Assam. Although the first railway line in Assam came up in 1881, yet Brahmaputra was not bridged by the British. It was bridged by HCC by building the 1.3 km long bridge at Saraighat near Guwahati. This bridge was opened to traffic in April 1962 by Prime Minister Jawaharlal Nehru. In 2017, a new 1.49 km long road bridge was constructed at Saraighat.
Kolia Bhomora Setu at Tezpur was the second bridge constructed by HCC. This pre-stressed concrete road bridge connects Sonitpuron in the north bank, with Nagaon district in the south bank. The length of this bridge is 3015 m, and its construction went on from 1981 to 1987.
Naranarayan Setu is the third bridge constructed over the Brahmaputra river. This double-deck bridge has a railway track on the lower deck and a road on the upper deck. It has a length of 2.284 km and connects Jogighopa, a town in Bongaigaon District in the north with Pancharatna, a town of Goalpara District in the south. This bridge was inaugurated on April 15, 1998, by Prime Minister Atal Bihari Vajpayee.
Built in 2017, Dhola–Sadiya Bridge, also referred to as the Bhupen Hazarika Setu, is the fourth bridge built over the Brahmaputra river, connecting the north-east states of Assam and Arunachal Pradesh. The bridge spans the Lohit River, a major tributary of the Brahmaputra River, from the village of Dhola in the south to Sadiya to the north. At 9.15 kms, it has the honour of being the longest bridge in India.
Bogibeel Bridge is a combined road and rail bridge in the Dibrugarh district of the north eastern state of Assam. The 4940.5 m long bridge is the longest bridge of its kind in India. The bridge provides connectivity to nearly five million people residing in Upper Assam and Arunachal Pradesh. It also gives easy and direct access to the upper Assam from the rest of the country through the North bank, in contrast to the current route through Guwahati in the South bank, which is long and tortuous.
HCC in a joint venture with DSD Brouckenbau GmbH, Germany, and VNR Infrastructures Ltd, received a ₹987 crore order from the Northeast Frontier Railway to construct the superstructure of Bogibeel Rail-cum-road Bridge in November 2011. HCC's share in this order is 51%, DSD Brouckenbau GmbH is 20%, and VNR Infrastructures' is 29%. Bogibeel Rail-cum-road Bridge is a double decked bridge with two railway tracks on the lower deck and a 3-lane road on the upper deck, flanked by footpaths on each side. Highway alignment will meet the top level of road deck of the bridge suitably beyond the abutments while the rail alignment will continue in the same line and level.
The Bogibeel Bridge, situated 17 km downstream of Dibrugarh and Dhemaji, spans the Brahmaputra river and connects the town of Dibrugarh in the south to Dhemaji to the river's north. The bridge is located just over 20 km away from the Assam-Arunachal Pradesh border and is thus expected to act as an alternative to the Kolia Bhomora Setu, Tezpur, in providing connectivity to nearly five million people residing in Upper Assam and Arunachal Pradesh
Bogibeel is the fifth rail-road bridge on the Brahmaputra river in Assam. Due to its location, the bridge is of strategic importance to India as it significantly enhances India's ability to transport troops and supplies to its borders in Tibet Arunachal Pradesh. Being in an area of intense rainfall, construction has been significantly challenging.
Bogibeel bridge provides a connection between the Rangia-Murkongselek section of the North East Frontier Railway on the north bank of Brahmaputra and Lumding–Dibrugarh section that lies to the south of the Brahmaputra. A new Dibrugarh Railway Station, expected to be the largest in the region, has been proposed and is to be linked to the Rangia-Murkongselek line via Chaulkhowa and Moranhat. The Railways have initiated the gauge conversion of the Dhamalgaon to Sisiborgaon rail line to the north of the bridge and commissioned the 44 km Chalkhowa-Moranhat line to the south.
The project obtained approval of the federal Cabinet Committee on Economic Affairs (CCEA) in September 1997 and construction began in April 2002. For building the bridge, the Indian Railways had to construct the expanse of the Brahmaputra river from 10 km to 5 km; this involved construction of 'guide bunds'. The project required about 505 hectares of land, which was acquired across 19 villages. Major earthworks and strengthening of the north and south dykes were completed by June 2011.
Contractors involved in the Bogibeel rail-road bridge:
- The state-owned consultancy and project management enterprise Rites (Rail India Technical and Engineering Services) undertook the pre-construction studies, geo-technical investigations and detailed design of the rail-road bridge.
- Bhartia Infra constructed the guide bunds and approach embankments on the south bank of the bridge.
- Contract for construction of foundations and substructure of the bridge was awarded to Gammon India in April 2008.
- A joint venture of Hindustan Construction Company (HCC), Germany-based DSD Brouckenbau and VNR Infrastructures was awarded the contract to construct superstructure of the bridge in November 2011.
Bogibeel is India's first and only fully welded bridge construction. It is also for the first time that European codes and welding standards were adhered to in the construction of a bridge in India.
Normally, in a steel bridge construction, bolts and rivets are used, which need periodic replacement due to shear failure over traffic loads. Construction of trusses using welding makes the connection between the components a permanent one, thereby eliminating the above failures. A welded bridge not only reduces maintenance cost but also adds to the longevity of the superstructure. It is estimated that Bogibeel Bridge is durable and serviceable for 120 years.
For the construction of this mammoth bridge, HCC has set-up huge facilities on the left bank of the river, and had three sequences of Fabrication, Assembly and Launching.
Fabrication: The Fabrication Shops of 2000 MT per month capacity were set-up with two parallel Bays. The team had assembled customized platforms in-house to fabricate and fit various joints employing Gas Metal Arc Welding (GMAW). To ensure an error-free welding - Magnetic Particle Testing, Dry Penetration Testing and Ultra Sonic Testing were deployed. A specialized Beam making CMM Machine from Italy was used for the first time in India for fabrication of Box and I-Sections using Submerged Arc Welding (SAW) procedure. A blasting gun was used to achieve the surface roughness of SA 2½ before applying paint. The intermediate and final spray coatings are performed in a highly controlled climatic chamber with spray guns.
Assembly: Thereafter, these fabricated sections are moved to the assembly shop where they are installed on their designated beds. They are guided to their correct positions through jacking and welded by GMAW process. These segments are arranged in a sequence and sent for the vertical assembly using horizontal lifters. After installation of the top and bottom girders, the final Truss Bridge Dimension Design Chambers are examined thoroughly and approved to complete the fit-out. A Nose is fabricated and fitted on the first truss before launching it on the piers.
Launch: While determining the methodology of erecting the steel trusses on pillars, engineers had two choices — lift the spans with floating cranes or erect them with a launching truss. And they have to decide based on which option would be more practical and economical. After weighing the pros and cons, the HCC team came-up with a solution of pulling the steel trusses with a set of jacks and winches on the pillars. This eliminated the need to enter the river, which was often turbulent during monsoons. Besides, it also ensured safer working conditions, precluded the mobilisation of giant set-ups on either side of the 4.8 km wide river, and accelerated the pace of the project.
The strategy is a testimony of the company's value engineering, an important feature of the globally-practiced 'Lean Construction' that is changing the way projects are executed from design to construction.
1000-ton hydraulic jacks and strand jacks linked with the substructures were used for moving the steel truss over the pillars. Two sets of steel cable strands were anchored to the end cross beams of the Truss and hauled by hydraulic jacks. The Truss slides over the Launching Bearing with the help of Sliding Plates, which were inserted at one end and taken out at the other, thereby moving the Truss towards its desired position. In order to limit the required launching forces, the superstructure was pulled in 4 launching segments of 10 spans each. Thus, the superstructure was pulled over the pillars just like a train of ten spans. With each span weighing 1700 MT, the pulling force required was equivalent to pulling 26 Airbus A380 with maximum take-off weight over 650 tons, put together without any wheels.
Finally, the launching bearings were replaced by final bearings. The tracks were laid, and the road was constructed adapting RCC construction. After fulfilling the electrical and other ancillary requirements, the assignment was completed.
Construction supply chain is a network of suppliers, manufacturers, assemblers, sub-contractors, retailers, customers and other stakeholders. The main objective of effective supply chain management is to reduce the handling costs and on-site storage. Enterprise Resource Planning (ERP) solutions such as System Applications & Products (SAP), implemented at all HCC project sites offer flexibility in material planning as per the construction sequence and help overcome challenges during execution. This, in turn, minimises the idling time of equipment and material inventories and enhances the efficiency of operations.
HCC follows the Just-In-Time (JIT) inventory system, where it produces or acquires materials and products as per demand. This is a key component of its supply chain.
One of the major challenges at most construction sites is logistics management, which depends on the availability of various transporters and modern tracking systems. It allows a project manager to select the right transport mix to bring heavy equipment or material to the project site and improve delivery time. At the Bogibeel Bridge project, the team used a combination of rail and road transport to deliver 80,000 tons of steel plates from various parts of the country to the remote project site in Assam. The orders for extra wide plates were placed in advance as per the design of the superstructure. In this way, the team avoided any possible mismatch of material and ensured qualitative and timely execution of the job.
Steel plates and sections were procured mainly from three sources i.e. JSPL, Essar and SAIL. Of these 80,000 MT, approximately 20,000 MT (25% scope) was categorized as ODC (Over Dimension Cargo) and attracted special measures for transport to the project site from the sources in Hazira and Angul, which were more than 3200 km and 1800 km away, respectively. The average lead time of procuring these materials is 4 months. Procurement plan was made according to minimum order quantity required thickness-wise, also estimating future market price trends as the order lot sizes ranges from 3500 MT to 10000 MT.
Spherical bearings were inspected at Germany, shipped to China for load testing, and then shipped to Bhopal for the refitting of tested bearings, and then finally shipped to project site. The lead time of such consignments is 6 months. Average daily consumption of welding wire was 2000 kg per day; grinding wheels around 5000 per day; Argon + Co2 shielding gas more than 200 cylinders per day; O2 cylinders around 500 per day; and around 50 BMCG cylinders per day. Besides 4,50,000 Shear studs were imported from Nelson, USA, (lead time of 3 months), High Strength Friction Grip bolts of around 7,00,000 quantity were manufactured at different sources in India, and Diamant MM1018FL gap compensation were imported from Germany (lead time of 3 months). The team achieved perfect synergy between each of these project elements' procurement and uninterrupted construction flow.
Arjun Dhawan, Director & Group CEO
HCC has time and again undertaken complex infrastructure projects that are benchmarks in India’s infrastructure journey. Bogibeel Bridge is an engineering masterpiece which has many technical firsts to its name. It is India’s first fully welded Warren truss girder type steel bridge. Not only has an incremental launching technique for superstructure erection been used for the first time in India, it is also the world’s longest incrementally launched steel bridge. HCC is proud to create such marvels for the nation.
The HCC team through its sheer determination and grit completed this project, as bridging the mighty Brahmaputra has always been a daunting task. The river is extremely difficult to bridge due to various reasons including its ferocious and unpredictable behaviour, high currents and turbulent waters, widespread erosion of the banks, short working period, high seismicity and the sheer remoteness of the area.
Most 2D Software
The fabrication of various components, using reinforcement bars and plates, has become an integral part of infrastructure projects. Advanced software is used to determine the optimum sizes of bars and plates before procurement, thereby reducing wastage and volume.
At the Bogibeel project, the HCC team used 'Most 2D' automatic nesting software to generate efficient two-dimensional cutting plans for fabricating the steel superstructure for the bridge. The nesting technology was based on advanced cutting algorithms specifically designed to optimise the cutting layouts in shearing. The software generates high-utilisation layouts, significantly reducing waste, and maximizes productivity.
Railways have traditionally used steel rocker-roller bearings for bridges with larger spans. For the Bogibeel Bridge, the initial plan was to use Pot-PTFE bearing with metallic pins and guide bearings. However, it was found that the size of bearing required for taking the anticipated load cannot be accommodated in the pier cap, hence, Spherical Bearings were used.
Spherical Bearings are designed to carry combinations of vertical loads, horizontal loads, longitudinal and transversal movements and rotations. They are used in steel and concrete road and railway bridges. The bearings are made of steel elements coupled with a PTFE surface to allow movement and rotations. One side of the internal median plate is machined as a spherical surface to allow tilting movement (rotation) whilst on the other side, a flat sliding surface is obtained to allow displacements.
Spherical Bearings with 4 support system as per European bearing standard EN- 1337 have been used in the Bogibeel Bridge. A total of 164 bearings have been used to construct the bridge. Each span is supported by 4 Spherical Bearings. These bearings had been manufactured by Maurer AG, Germany, in accordance with the design finalized and approved by Ramboll / RITES.
Corrosion Protection Measures
The superstructure of Bogibeel Bridge has been constructed using a special grade copper-bearing steel plates to reduce corrosion. The average annual relative humidity in Bogibeel is 90% which goes up to 96 - 97%. To further reduce corrosion due to the excessive humidity, a complex Corrosion Protection System specific to different components of the bridge has been implemented during construction.
- Metal Spraying – Aluminum: Thermal Spray, basically known as Metallizing; is a process in which metal is melted and directly sprayed onto the surface of another metal to protect against corrosion, heat, traction, etc. Aluminum (Al) provides excellent corrosion resistance properties. TSA coating provides enhanced shelf life, maximum corrosion protection and very less curing time compared to painting. This method was used for the Gusset Plates and Brackets.
- For the exterior of Bottom Chord, Bottom Joint & Bottom Cross Girder, Hot Zinc spray has been carried out as a primer then epoxy with MIO & TIO2 coating on it and Aliphatic Polyurethane coating has been carried out on the top of it.
- For surfaces in contact with concrete that is the Top Chord and Top Joint, Metal Spray Zinc Coating of 80uM has been carried out.
- For exterior of Top Chord, Top Joint, Top Cross Girders and Diagonals, a primer of Inorganic Zinc Silicate having an intermediate coat of Epoxy with MIO and a top coat of Aliphatic Polyurethane has been carried out.
- For interior of Bottom Chord, Bottom Joint, Top Chord, Top Joint, Top Cross Girder and Diagonals, a primer of zinc-rich epoxy having an intermediate coat of PVC with MIO and a top coat of water-based Polyurethane was applied.
- And for surface with concrete that is Top Cross Girder, a final coat of Metal Spray Aluminum Coating was done again to ensure complete corrosion protection.
- Hot Dip Galvanizing is the process of coating iron and steel with zinc, which alloys with the surface of the base metal. It is done by immersing the metal in molten zinc at a temperature of around 840°F (449°C). Here, a coating of 250 uM was applied to the Stringers & Bracings of the bridge.
- Also, all enclosed spaces were sealed by welding and were vacuum tested so that no air can go inside and initiate corrosion.
Location of Bogibeel Bridge falls in Seismic Zone-V, which in Indian history, has been most vulnerable to earthquakes with magnitudes in excess of 7.0. In order to offer good stability to the heavy spans (1700 MT), they are provided with seismic restrainers.
This arrangement works like male & female connection with female pockets embedded onto piers and male parts arrangement on the span. For precise lowering of the span such that male joint fits into the female connections before the final lowering of the span on the permanent bearings, HCC team devised a unique circular slider frame made of stainless steel with jacks arrangement.
With this, the exact movement to fit the Seismic restrainers and final lowering of the heavy spans on permanent bearings were achieved.
Bogibeel Bridge: Asia's Longest & Most Famous
- The project boasts of benefits such as strategic and speedier access for defence forces to the Indo-China border, which means faster movement of troops and heavy weaponry.
- Provides better connectivity to nearly five million people inhabiting the upper Assam region and Arunachal Pradesh. Saves travel-time between Tinsukia in Assam to Naharlagun of Arunachal Pradesh by more than 10 hours, thereby saving fuel and travel cost. The 4.94 km bridge now connects the south bank of Brahmaputra river in Assam's Dibrugarh district with Silapathar in Dhemaji district close to Arunachal Pradesh, and cuts down the distance between the two by about 400 km.
- Its biggest benefit is the travel time that it will save: as of now, a train journey from Arunachal Pradesh to Assam's Dibrugarh requires a 500 km detour via Guwahati. Now, the journey is reduced to less than 100 km. Also, the train journey between Delhi and Dibrugarh has reduced by 3 hours.
- Tourist places of Arunachal Pradesh will become more accessible and give a fillip to the tourism industry. The bridge also cuts down the distance to the border with China by 10 hours.
- The bridge benefits the intra/inter-state transportation of medical patients seeking treatment in Dibrugarh district, which houses the prestigious Assam Medical College. Currently, if any emergency of super speciality kind arises along the northern bank, patients have to rely on the cumbersome boat ferries.
- The bridge is part of the infrastructure projects conceived by the government of India to improve logistics along the border in Arunachal Pradesh. By connecting two very important highways of Assam - NH37 and NH52, the bridge enhances the intra-state trade ecosystem. At present, cargo takes 10 to 12 hours to reach its destination. The Bogibeel Rail-Road link reduces trans-shipment time and takes maximum 2 hours, thus saving cost of transportation, fuel, and the time taken.
- At 32 meters above water level of the mighty Brahmaputra river, it is hailed as an engineering marvel of the country as construction of such a mega-bridge in a seismically sensitive zone was a herculean task for the engineers. About 30 lakh bags of cement, 19,250 mt reinforcement steel, and 2,800 mt structural steel were used.
- Has earned the distinction of being Asia's second largest bridge with three-lane roads on top and a double rail line underneath. Constructed at a cost of ₹5,920 crores, it assures a serviceable period of around 120 years.