The third longest railway tunnel in the country connecting the under-construction Vizhinjam International Seaport being developed by the Adani Port with the railway mainline at Balaramapuram near Thiruvananthapuram will use the New Austrian Tunnelling Method (NATM) for undertaking the tunnelling works. The work scheduled to begin in January will take 36 months for the completion of tunnelling work alone plus three months of initial installation work and another 3 months for track lining and commissioning, taking a total of 42 months for the entire work.
The country’s largest 12.75 km long railway tunnel (T-49) is built as part of the Udhampur-Srinagar-Baramula Rail Link (USBRL) project, surpassing the 11.2-km long Pir Panjal Tunnel on the Banihal-Qazigund section. Instead of using the expensive tunnel boring machine (TBM), Vizhinjam International Seaport Limited (VISL) which is implementing the Vizhinjam deep water multipurpose seaport on a PPP basis, adopted the cost-effective NATM method which uses a modern drilling and blasting technique.
The cross-section profile of the single-line broad gauge railway tunnel is likely to be horseshoe-shaped. By using the NATM, the authorities are planning to do the tunnelling works in three or four phases simultaneously. Further, machines to be pressed in for tunnelling work can be reversed inside the tube at any point of time by adopting this method. In addition, the excavated boulders, and soils can also be re-used for construction purposes to a greater extent, said sources.
