Bridges and tunnels in India serve as crucial infrastructural components that contribute to the advancement of transportation systems. These subsectors effectively enhance connectivity, particularly in regions that are geographically challenging to access. Moreover, these structures are designed with the purpose of mitigating traffic congestion and providing an alternative and expedited means of transportation.
India has an extensive network of bridges, including river and sea bridges, rail bridges and road bridges. Rail-cum-road bridges account for a major part of the Indian rail and road network. Further, Indian bridges establish critical linkages between cities. Tunnel construction has also become an integral part of infrastructure development in India. It has seen significant growth in the past few years, owing to development across sectors such as urban rail, highways, hydropower, irrigation and water. The rapid construction of tunnels in hilly northern areas has also enabled better connectivity with the rest of the country.
Safety first
With the rise in the number of tunnels being constructed and the growth in traffic volumes in existing tunnels, safety measures are assuming greater importance. The development of safe tunnels necessitates the consideration of factors such as tunnel design, ventilation system and firefighting procedures. Another essential safety consideration is the design of tunnel lights to ensure the safety of both labour and travellers. In line with these measures, the recently inaugurated D-shaped, single-tube, double-lane Nechiphu tunnel, at an altitude of 1,630 metres, is equipped with modern lighting, safety facilities, electromechanical systems and firefighting devices.
Meanwhile, in bridge construction too, safety considerations are paramount. Several Indian bridges have been found to be precarious. For instance, in June 2023, the four-lane Sultanganj-Aguani Ghat bridge collapsed, and in October 2023, another under-construction bridge in Panalpur, Gujarat, faced the same fate. More needs to be done to remedy such construction mishaps. There is scope for improvement in the conceptual specifications governing bridge construction methods. For instance, high levels of engineering diligence could go into detailed project reports.
Taking into consideration the importance of safety in tunnels and bridges, as of August 2023, the National Highways Authority of India (NHAI) has established a new design division for effective review of design and construction of bridges, tunnels, other specialised structures and reinforced earth walls. This is expected to contribute significantly to the overall quality and safety of India’s road network. Furthermore, over the past few years, with the help of the Indian Bridge Management System (IBMS), a multitude of bridges have been identified for renovation and replacement.
Sustainable construction
Several smart construction materials are emerging for the construction of bridges. These are engineered to respond to cracks, excessive stress and environmental effects such as temperature and pressure. One of the most innovative materials is self-healing concrete. Fly ash is also being used as the prime material in many cement-based products such as poured concrete, concrete blocks and bricks.
For tunnel construction, contractors are increasingly utilising innovative materials such as fibre bolts, fibre-reinforced shotcrete, geosynthetics, geomembranes and self-drilling rock bolts to increase the durability and strength of geologically challenging projects.
In recent times, preference has shifted to the use of refurbished tunnel boring machines (TBMs) as opposed to brand-new TBMs for each new tunnel project. In early 2023, TERRATEC, a renowned designer and manufacturer of TBMs, launched an earth pressure balance TBM for the Surat metro in Gujarat.
The utilisation of tunnel muck, a waste product of tunnel excavation in the Udhampur-Srinagar-Baramulla rail-link project, has resulted in the reduction of carbon emissions by 80 per cent, while simultaneously decreasing the project cost by 30 per cent. Furthermore, electrically powered equipment and electric drum cutters have the potential to be scaled up even further.
Technology backing
The bridge design and construction process has evolved significantly with the introduction of smart digital technologies. Building Information Modelling is one such technology. The Ministry of Road Transport and Highways has set up IBMS to identify distressed bridge assets and inform the concerned implementation agency to take corrective measures. South-Central Railway has also introduced drones for improving the inspection and maintenance of bridges.
For the construction of the Mumbai Trans Harbour Link, the country’s longest sea bridge, the Mumbai Metropolitan Region Development Authority is using modern bridge technology to overcome sea-related challenges. This includes reverse circulation drilling piling, orthotropic steel deck (OSD) bridge girders, wind tunnel testing for OSD bridge design, tuned mass dampers for OSD bridges, full-scale vehicle impact testing for new crash barrier design and seismic hazard analysis for design. The bridge would also feature an open road tolling system.
Some new technologies have been deployed to enhance the effectiveness of the drill blast method for tunnel construction. These include advanced blast fragmentation modelling software such as two-dimensional bench. Similarly, new technologies being deployed for TBMs include the TUnIS Ring Sequencing System and the Automatic Tailskin Clearance Measurement System.
Recently, Indian Railways has developed a new method of tunnelling, the (I)-TM method, for a 3.2 km long difficult section in the Katra-Banihal section of the Kashmir Rail Link project. This method involves pre-excavation support measures to tackle conditions that could be encountered during excavation.
Key project updates
In October 2023, the Border Roads Organisation (BRO) inaugurated around 90 infrastructure projects, of which 63 are bridge projects. During the same month, Dishom Guru Shibu Soren Setu, the longest bridge in Jharkhand spanning 2.34 km, was also inaugurated.
Under-construction bridge projects include the Godkhali-Gosaba Bazar Bridge Project in West Bengal, the Azhikode-Munambam Bridge Project in Kerala, the Beyt Dwarka-Okha Sea Bridge Project in Gujarat and the Gokhale Bridge Project in Maharashtra.
After a delay of around 20 years, the Brihanmumbai Municipal Corporation has resumed its plan to construct a vehicular bridge connecting Lokhandwala and Yari Road in Andheri. This bridge is expected to cut travel time from 35 minutes to just five minutes.
Approved at a cost of around Rs 16.81 billion in February 2023, the 4.1 km long Shinkun La tunnel is expected to be completed by December 2025. Further, the BRO is expected to complete the work on the world’s longest bi-lane tunnel at an altitude of more than 13,000 feet (post completion), the Sela Pass tunnel in Arunachal Pradesh, by the end of 2023.
Bengaluru has recently announced its plans to construct a 190 km long tunnel road to ease traffic congestion. Currently, eight companies have been shortlisted to determine the project’s feasibility and the possible areas it could cover, along with a starting and end point. Drilling activities on the all-weather Zojila tunnel are around 40 per cent complete.
Pain points
Even though cutting-edge technology is available and always advancing, its ecosystem (trained operators, maintenance and logistics) is expensive, making tunnel and bridge construction capital intensive. Permit and clearance delays also lower productivity, which, in turn, impacts the return on investments.
High investments in bridge construction equipment such as launching gantries, bridge builders and moulds also cannot be recovered in a single project. Furthermore, limited access roads hamper the deployment of heavy equipment such as TBMs in mountainous regions.
The way forward
Tunnel and bridge construction in India is witnessing a transformation. India can maximise this development potential by expediting clearances, investing in local workforce and reducing the reliance on imports for equipment. With many Tier I and Tier II cities planning metro systems, India needs to increase its domestic equipment manufacturing for at least TBMs, a key method for urban tunnelling. This journey, however, necessitates collaboration, innovation and an unwavering commitment to overcome industry challenges.
Going forward, deploying digital advancements in these structures will help ensure safety and quality. Geospatial technology for remotely monitoring the condition of these structures is also an area that requires focus.
Harman Mangat
