BrahmaputraTunnel TunnelEngineering RoadRailTunnel Assam

India first underwater road and rail tunnel under Brahmaputra

*Proposed Brahmaputra underwater road and rail tunnel corridor connecting Gohpur and Numaligarh in Assam. Source: Tunnel and Tunneling (image by muratart)*

India has approved the construction of its first underwater road-cum-rail tunnel beneath the Brahmaputra River in Assam, marking a major step for transport connectivity in the north-east of the country. The project will form part of a 33.7 km four-lane access-controlled greenfield corridor connecting Gohpur on NH-15 with Numaligarh on NH-715.

The approved scheme includes a 15.79 km twin-tube tunnel under the Brahmaputra, with road traffic and railway infrastructure integrated into the tunnel system. The project will be delivered under an Engineering, Procurement and Construction model, with an estimated total capital cost of Rs 18,662 crore, equivalent to roughly US$2.2bn at recent exchange rates.

At present, travel between Gohpur and Numaligarh depends on a 240 km route via the Kaliabhambhora road bridge, passing through Kaziranga National Park and Biswanath Town. The journey can take up to six hours. Once the new corridor is completed, the distance is expected to be reduced to about 34 km and the travel time could fall to around 20 minutes.

The twin-tube tunnel will form part of a 33.7 km access-controlled corridor linking national highways and railway lines. Source: Cabinet Committee on Economic Affairs

The Brahmaputra is one of Asia’s major river systems, with high seasonal flows, shifting sediment, deep alluvial deposits and complex floodplain conditions. Constructing a twin-tube tunnel beneath such a river will require detailed geotechnical, hydrogeological and construction risk management.

The tunnel is planned as a tunnel boring machine scheme, supported by cut-and-cover sections for both road and rail connections. The project includes 1.26 km of road cut-and-cover works and 4 km of rail cut-and-cover works. These transition zones are technically important because they connect the bored tunnel to surface infrastructure and must be designed for groundwater control, flood resilience, settlement management and long-term durability.

For engineers, the main challenges are likely to include face stability during tunnelling, groundwater pressure, segmental lining performance, emergency evacuation provisions, ventilation, drainage, railway integration and protection against long-term riverbed changes. The tunnel will also need to accommodate both transport safety requirements and strategic mobility needs in a region where river crossings are limited.

The project is intended to improve movement across Assam, Arunachal Pradesh, Nagaland and other north-eastern states. By linking NH-15 and NH-715 with the regional rail network, it will support both passenger travel and freight movement. The alignment will connect with the Rangia-Mukongselek railway section on the Gohpur side and the Furkating-Mariani loop line on the Numaligarh side.

The wider corridor is also planned to connect economic, social, tourism and logistics nodes, including railway stations, airports and inland waterway terminals. This makes the project more than a single river crossing. It is a multimodal transport corridor intended to reduce logistics costs, improve access to markets and strengthen regional economic integration.

The tunnel is also expected to support strategic mobility and create around 80 lakh person-days of direct and indirect employment during construction. Once operational, it could reduce pressure on existing routes, improve reliability during peak travel periods and support faster movement of goods across the north-east.

India’s Brahmaputra road-cum-rail tunnel will be a landmark project for underground infrastructure. Its success will depend on careful geotechnical investigation, robust tunnel design, strict construction control and long-term asset management beneath one of the country’s most challenging river environments.

Sources: tunnelsandtunnelling.com, newsonair.gov.in, www.pib.gov.in