A case history of tunnelling through difficult ground

摘要

Udhampur-Katra section is the first leg of the prestigious and challenging Udhampur-Srinagar-Baramulla Rail Link project covering a total length of 287.0 km in Jammu & Kashmir state of India. The project envisages construction of a new single line broad gauge railway with maximum speed potential of 100 km/h with ruling gradient limited to 1 in 100. The Udhampur-Katra section of the project is 25 km long, and it involves construction of 8 tunnels, aggregating to a total length of 10 km. Out of 8 tunnels, 2 tunnels - Tunnel No. 1 (3.2 km) and Tunnel No. 3 (2.5 km) - are over 2 km long. The Tunnel No. 1 is D-shaped with excavation width of 6.5 m and excavated height approximately 8.2 m. Generally the primary supports are steel ribs ISHB 150 with varying spacing depending up on the rock type. At some places double rings of steel ribs are also used.