Udhampur-Katra section is the first leg of Udhampur-Srinagar-Baramulla Rail Link project. This section is 25km long and involves construction of 7 tunnels. The 3.11 km long D-shaped Tunnel No. 1, discussed in the paper, has excavation width of about 6.5m and height approximately 8.2m. The primary supports, generally, are steel ribs with varying spacing depending upon the rock type. The main rock types encountered along the tunnel alignment were sandstones, clay stones, silt stones and overburden comprising of boulders/pebbles in sandy/silty matrix. Due to presence of swelling minerals and weak rock formation with high rock cover (up to 313m), the tunnelling has experienced both swelling and squeezing ground conditions and the steel rib supports have buckled from the sides. Floor heaving has also been observed frequently. Tunnel instrumentation was carried out to study the rock and support behaviour. Simultaneously, the rock mass classification approach was also used to study the degree of squeezing and for estimating the support pressure and design of supports. A flexible system of support was adopted with success. (A) This paper was presented at Safety in the underground space - Proceedings of the ITA-AITES 2006 World Tunnel Congress and the 32nd ITA General Assembly, Seoul, Korea, 22-27 April 2006. For the covering abstract see ITRD E129148. Reprinted with permission from Elsevier.