Tech Behind India’s Longest Rail Tunnel Between Rishikesh and Karnaprayag-OxBig News Network

India’s longest railway tunnel is presently below building in Uttarakhand. Dubbed Tunnel No. 8 or T-8, will probably be a 14.57km tunnel between Rishikesh and Karnaprayag, and join Devprayag and Janasu in Uttarakhand. While the size of the tunnel in itself is a serious engineering achievement, the know-how that went into the excavation and building of the construction in such a difficult terrain additionally deserves recognition. To carve a gap within the mountains, engineers used a mix of a German-imported Tunnel Boring Machine (TBM) named ‘Shakti’ and the New Austrian Tunnelling Method (NATM).

Using TBM Shakti and NATM to Build India’s Longest Railway Tunnel

Larsen & Toubro (L&T) announced that it had achieved the breakthrough within the tunnel excavation venture in April. Tunnel breakthrough is the purpose of excavation when each ends of a tunnel lastly join for the primary time. The tunnel, which is a part of the Rishikesh-Karnaprayag Broad Gauge Rail Link Project of Rail Vikas Nigam Limited (RVNL), is predicted to be operational by the tip of 2026.

Once it’s operational, T-8 will supersede the 12.75km lengthy T-49 tunnel between Khari and Sumber stations on the Udhampur-Srinagar-Baramulla Rail Link in Jammu and Kashmir because the longest railway tunnel.

At the time, L&T stated that 10.4km of the tunnel was accomplished utilizing a Single-Shield TBM named Shakti. With a diameter of 9.11m, it’s stated to be the biggest TBM to be deployed within the Himalayan area. It excavated at a median fee of 413 metres per 30 days. The remaining 4.11km of the tunnel was accomplished utilizing the NATM.

A TBM is a huge cylindrical machine that’s able to excavating tunnels by each soil and rock whereas inflicting minimal disturbance to the encircling floor. It comprises a rotating metal disk with disc cutters that cuts by rocks at excessive strain. The cutterhead is designed to chop by quartzite, schist, and phyllite, that are frequent within the Himalayan rock deposits.

A phase erector system is positioned behind the cutterhead, which provides precast concrete segments so as to add structural integrity to the freshly excavated tunnel. Additionally, the particles (often known as muck) is frequently faraway from the tunnel utilizing a conveyor system.

While the TBM was used for the key portion of the tunnel, it can’t be utilized in difficult geological areas coinciding with fault zones, water ingress, and extra. Using a big machine to excavate these parts may negatively influence the structural integrity of your complete tunnel.

L&T says it used NATM, which makes use of drill-and-blast or mechanical excavation technique with fixed monitoring of floor situation. Usually, small sections are excavated at a time utilizing this know-how. Once rock and muck is eliminated, shotcrete (sprayed concrete), rock bolts, and metal ribs are added to the uncovered space to stop deformation and collapse.

Throughout this course of, crewmates monitor tunnel stress and motion utilizing devices akin to extensometers and cargo cells. NATM is crucial to tunnel excavation in difficult terrains, as they provide lowered dependence on massive equipment and adaptability within the building course of.