Introduction
Enhanced operational preparedness along the borders and the need to be self-reliant are two major aspects that have seen a substantial impetus over the last few years. The Border Roads Organisation (BRO) has been a key contributor to the infrastructure development drive as well as the aspect of self-reliance through its execution of various works. The 140 feet modular double lane bridge being discussed has brought forth a new dimension of self-reliance wherein the BRO has integrated with an Indian manufacturer to launch the first ever indigenously developed Double Lane Modular Bridge at an altitude of 11,000 feet.
A key focus area identified in strengthening the defence preparedness along the borders has been that of rapid infrastructure development to address the existing infrastructure voids. This has resulted in enhanced impetus through demonstration of intent, resource allocation, and setting strict timelines to address this operationally critical requirement.
The Dokalam crisis of 2017 further highlighted the existing operational voids and the need to provide connectivity to the crucial sectors became paramount. An operationally crucial road was planned for construction. Besides serving as an alternate link to one of the important forward posts of the sector, it also provided Project Swastik of BRO the opportunity to launch the first ever indigenously developed 140 feet double lane modular steel bridge at an altitude of 11,000 ft effectively synergizing a significant operational requirement and the AatmaNirbharta drive.
Road Flag Hill-Dokala
The 34.00-km road aims to provide all-weather connectivity to the Dokalam sector and serve as a crucial link to the area, particularly during winters when heavy snowfall inevitably keeps one of the two axis closed for short durations. Spanning altitudes ranging from 11000 to 14500 feet, the road passes through extremely difficult and treacherous terrains, and has presented a formidable challenge to personnel as well as equipment of BRO during the construction phase.
While the quantum of hard rock to be cut, limited space, and extreme weather conditions, tested the physical capabilities of the BRO Karmyogis, and the mechanical reliability and sustainability of the vehicles, equipment and plant being employed, the extremely limited working season posed yet another challenge to complete the construction of the road within the laid down timelines.
The significance of the road having been established from the military point of view, it is pertinent to visualize the road alignment in order to fathom the requirement of bridging various gaps along the road. The area is characterized by numerous turns through dense forests, steep and rugged mountains, wildlife sanctuaries and biosphere reserves, that pose peculiar challenges to construction activities. Streams, nallahs and terrain undulations necessitated a careful and diligent terrain study to plan bridges, culverts, and causeways along the entire length of the road. It is in this context that the water obstacle where the Modular Bridge was planned to be launched presented a challenging gap of 140 feet to be bridged, while the other smaller gaps and low-lying areas were addressed through a mix of Bailey Bridges and culverts.
Picture 1 : Man Machine Harmony – Adding Storeys140 Feet Double Lane Modular Steel Bridge
The Bridge site is located at an altitude of 11,000 feet. With the road nearing completion at an exceptional pace, bridging this gap necessitated adoption of speedy means. The commonly used permanent RCC bridges were ruled out due to the time involved, more so in view of the extreme weather conditions restricting the construction of RCC bridges. Consequently, the time tested and reliable work horses, namely the Bailey Bridge and Extra Wide Bailey Bridge were considered as alternatives.
Fusing Operational Requirement and Make in India Concept
It was here that Garden Reach Shipbuilders and Engineers (GRSE) Kolkata, spurred by the drive of Make in India and committed towards achieving the goal of self-reliance (Aatmanirbharta), rose to the challenge and presented this double lane modular steel bridge for launch on a No-Cost-No-Commitment (NCNC) basis.
The fabrication of this bridge was an outcome of the Memorandum of Understanding (MoU) with the Government of India signed on 30 Jan 2019 to ‘fabricate bridges as part of the Honourable Prime Minister’s “Make in India” initiative and the Government’s resolve to provide faster connectivity to border areas.
A major milestone achieved in the manufacturing of this indigenous bridge was the overcoming of limitations in metallurgy that have severely impeded construction of major bridge systems within the country and made us reliant on foreign exchange depleting imports. GRSE not only came up with a state-of-the-art, fully indigenized bridge, but also ensured that the raw materials used were also 100 percent locally sourced from the domestic Public Sector Undertaking (PSU) Steel Authority of India (SAIL). The bridge was designed to cater to the terrain and weather peculiarities in its intended area of use and was found to be particularly suitable for launch in mountains and high-altitude areas.
Different from the routinely used Bailey and Extra Wide Bailey Bridges, which are characterized by reducing load class with increasing spans and a single lane roadway, the indigenously made modular bridge provides a load class of 70R at a maximum span of 140 feet due to its modular nature. While a maximum span of 140 feet is permissible with the existing Bailey and Extra Wide Bailey Bridges also in order to achieve a load class of 70R, the modular bridge providing load class of 70R at 140 feet in a Triple Double configuration becomes a significant game changer in addressing operational requirements by virtue of its 7.5m carriage akin to a double lane roadway making it suitable for use along all National Highway Double Lane (NHDL) roads. Even roads with National Highway Single Lane (NHSL)/ Cl 9 specifications can utilize the bridge as future expansions can benefit from its greater carriageway without the need for replacing the bridge yet again at substantial cost and time. The indigenous modular bridge provides a substantial fillip to induction and movement of heavy equipment and weapon platforms including those that are likely to be inducted in future modernization drives of the Indian Armed Forces.
Picture 2 : Adding One Bay at a TimeTechnical Specifications
Key technical parameters of the modular bridge developed indigenously are given in table 1. A factory cost of approximately Rs 3.5 crores for the 140 feet Triple Double Reinforced configuration makes it economical from a cost-benefit analysis perspective.
| Parameters | Specifications |
| Span | 140 Feet (Double Lane) |
| Width | 7.5m |
| Weight | 167 MT |
| Panel Size | 10 feet x 7 feet |
Load Class |
70R |
| Life | 25 years |
| Steel Deck | Yes |
| Configuration | Triple Double Reinforced (TDR) |
| Erection Time | 25 days in HAA 15 days in other trn Abutments ready and all stores available on site |
| Cost | Rs 3.5 Crores ex-factory |
The indigenously developed bridge was provided on a NCNC basis by GRSE, Kolkata for launch on the Flag Hill - Dokala Road. The construction of the specially designed abutments, catering for a dead load of 167 Metric Tonnes of the bridge itself, commenced in the first week of October 2020 and was completed by end of the month. Delivery of the stores by the firm commenced in November 2020 and was completed by 26 December 2020 resulting in the process of launch of the bridge starting with effect from 03 January 2021. Despite inclement weather and heavy snowfall causing disruptions in the construction schedule, the bridge was completed on 10 February 2021.
Picture 3 : Finalising the Approach and ExitChallenges During Construction
Addition to the challenges posed by the treacherous terrain and adverse weather, the additional challenges faced are discussed below:-
- Transportation: The long transoms posed multiple challenges in transportation including the need for providing longer than normal trailers for moving the components from Kolkata to Flag Hill. Further move of stores to the construction site required innovative measures to be undertaken to shift the longer components.
- Carriage and Handling: The bridge components being heavier than the normal and extra wide Bailey Bridges resulted in additional requirement of vehicles to carry stores to the construction site. The heavier components also required provisioning of multiple mechanical material handling equipment to be provisioned at the loading/ unloading sites. The configuration being a double storey, construction of the second storey proved challenging due to the increased weight and dimensions of the components.
- Construction in High Altitude Terrain: The bridge was launched at 11,000 feet altitude in an area with sub-zero temperatures requiring large scale acclimatization of the entire work force. Provisioning of special equipment such as gloves and other extreme climate clothing had to be catered for to prevent cold-related injuries. Launching Challenges
- Modifications to Drills: The heavier and longer components as also the fact that the bridge was being launched for the first time necessitated modifications to the existing drills and techniques resulting in delays. Practice and training will however reduce the difficulties on this account in future.
- Limited Backspace: The terrain precluded availability of the design backspace required for smooth launch necessitating on site supervisors and functionaries to modify launching techniques and innovate new methods.
- Replacement/Provisioning of Components: Any deficiencies/ additional requirements could be met only from the factory premises located at Kolkata thereby requiring diligent handling and careful planning/ forecasting.
- Design of Abutment: The abutments had to be specially designed and constructed to cater for the enhanced weight and width of 167 MT and 10m respectively.
The relatively low construction time of the bridge, as compared to permanent RCC bridges, allows for key operational requirements being met in a much faster timeframe. The bridge being of load class 70R also provides the option to induct operational equipment of Armed Forces to the intended area of operations.
BRO being a premier infrastructure construction agency, is engaged in comprehensive Nation Building activities. The infrastructure developed by the BRO in terms of its roads, bridges, tunnels and airfields, in addition to serving military requirements and enhancing defence preparedness, also provides a major boost to the socio-economic development of the Nation and the specific region in which these works are executed. The bridge provides a substantial boost to the Government’s resolve to provide faster connectivity to remote border areas and provides a platform for developing the economic potential of such areas. The class 70R bridge will also facilitate last mile connectivity to major infrastructure development projects such as expansion of the railway networks, power supply grids besides serving to enhance employment avenues, etc in the State of Sikkim in particular and the Nation in general. The bridge, due to relatively low construction time, can be used to plug breaches during disruption in communication network caused due to natural calamities.
Picture 4: 140 Feet Triple Double Reinforced Modular Steel Bridge on Road Flag Hill-DokalaPrognosis
Development of the Modular Bridge through indigenous means has proved to be a major boost, not just to the defence preparedness of the Nation but also to the goal of achieving self-reliance in key manufacturing sectors including Defence. The launching of this bridge on the Flag – Hill Dokala road by virtue of the load class and carriageway has given immense strategic benefits.
The metallurgy skills developed indigenously must be utilized to develop other bridge systems being used by the construction agencies like Bailey and Medium Girder Bridges. The need to further improve metallurgy in a qualitative manner necessitates greater impetus to research and development in this field in order to be truly self-reliant. Indigenous development must not remain limited to meeting domestic requirements and an export-oriented production facility needs to be setup. In addition to being a valuable source of foreign exchange, the export unit earnings therefrom, will also facilitate ploughing back these funds for research and development.
The Double Lane Modular Bridge by virtue of its indigenous make provides the much-needed boost to the quest for self-reliance by the country. This unprecedented first, achieved by the BRO in record time and at challenging altitudes, will go a long way in enhancing the country’s operational posture along the Northern borders, in addition to accelerating the socio-economic development of far-flung and remote areas due to its ability of being launched in extremely short periods of time.
