ABSTRACT
Rohtang Tunnel is being constructed in the Pir Panjal ranges of Himachal Pradesh, India to provide all weather access between Manali and Lahaul on Manali-Sarchu-Leh road which remains closed for six months in a year. Total length of Rohtang Tunnel is 8.802 Km. Drill & Blast technique for excavation is being used for the construction of Rohtang Tunnel. The tunnel is a very deep with a maximum overburden close to 2 kms. Rohtang tunnel project is located within ‘Central crystalline’ litho-tectonic group of Himalayas. Main rock types along the alignment are Phyllites, Quartzites, Mica schist, Migmatite and Gneiss. During the excavation, the Tunnel has faced many geological challenges owing to the high overburden and peculiar Himalayan geology. The project has been delayed by almost four years after encountering a massive fault zone of almost 590 m which led to many muck flows coupled with heavy ingress of water. These extraordinary Tunnelling conditions besides being technically complex also posed many contractual challenges as the FIDIC contract agreement in force could not provide any robust resolutions to payment related disputes. This paper attempts to analyze the geological occurrences, reasons for rock mass failure, and recommend necessary measures to ensure smooth handling of both technical and contractual issues.
