The third longest railway tunnel in India will use the New Austrian Tunnelling Method

The third longest railway tunnel in the country will use the New Austrian Tunnelling Method (NATM) to connect the under-construction Vizhinjam International Seaport being developed by Adani Port with the railway mainline at Balaramapuram near Thiruvananthapuram. The construction, which is set to begin in January, will take 36 months to complete, plus three months for initial installation and another three months for track lining and commissioning, for a total of 42 months for the whole project.

The 12.75-kilometer-long T-49 railway tunnel is being built as part of the Udhampur-Srinagar-Baramula Rail Link (USBRL) project, exceeding the 11.2-kilometer-long Pir Panjal Tunnel on the Banihal-Qazigund segment. Vizhinjam International Seaport Limited (VISL), which is developing the Vizhinjam deep water multifunctional seaport on a PPP basis, chose the cost-effective NATM technology, which employs a modern drilling and blasting technique, instead of the expensive tunnel boring machine (TBM).

The cross-section profile of the single-line broad gauge railway tunnel is likely to be horseshoe-shaped. The authorities want to complete the tunnelling work in three or four phases concurrently by employing the NATM. This technology also allows machinery to be pushed in allowing tunnelling work to be reversed within the tube at any moment. According to reports, excavated boulders and soils can also be re-used for construction purposes to a larger extent.

The 9.02 km long tunnel at a depth of 25-30 metres below earth is not projected to be a difficult undertaking for the authorities because the soil layers reveal soft rock, worn rock, and silt along the route. However, because Vellayani Lake is adjacent to the route, subterranean aquifers prone to floods are anticipated. When completed, rakes from the Vizhinajm port would be able to go through the tunnel in about 36 minutes at an average speed of 15-30 kmph.

The 1,120-crore project necessitates 6.431 acres to connect the port to the Balaramapuram stopping station, a total distance of 10.7 km. The expense of upgrading the Balaramapuram stopping station to a connecting station will be met by the VISL. The project will be built on the Non-Governmental Railway (NGR) model, which guarantees private sector participation in providing last-mile connectivity. The State has approved signing a deal with Southern Railways to build the line under the NGR concept.

The National Bank for Agriculture and Rural Development (NABARD) will provide funding for the project. In 2018, VISL signed a deal with Konkan Railway Corporation Ltd, the implementing agency. Despite the fact that the Vizhinjam port has gained Environmental Clearance, the State has applied to change it since rail access to the port was originally planned over the surface. Following the modification in the building model, the State has now requested that the Central Institute of Mining and Fuel Research, Dhanbad, conduct an underground tunnel project study and provide a report within one month.