Kameng Hydro Electric project (4x150MW), a ROR scheme was constructed by North Eastern Electric Power Corporation Ltd in the West Kameng District of Arunachal Pradesh, India. This project lies in the Lesser Himalaya consisting of Precambrian and Gondwana rock formations. A 14.5 km long tunnel was constructed to convey water from Bichom to Kimi for 600 MW of power generation. This paper deals with the challenges faced during tunnel boring in tectonically disturbed Himalayan terrain and the mitigation measures adopted in overcoming these geological challenges. The challenges comprised cavity formation, blow out, Squeezing, high seepage and very weak rockmass with high rock cover. The mitigation measures adopted to overcome these challenges included fore-poling, umbrella/canopy with channel/joist and chemical/cement grouting etc. After overcoming all these tunnelling challenges, the boring of HRT was successfully completed in March’2015.
North Eastern Electric Power Corporation Limited executed Kameng Hydro Electric Project located in West Kameng district of Arunachal Pradesh, India from Lat 27.30°N, Long 92.30°E to Lat 27.17°N, Long 92.69° E. It is a run-of-the-river scheme with a gross head of 536 meters. It was envisaged to generate 3353 MU of electricity annually by constructing two dams across Bichom river and Tenga river. A 69 m high concrete gravity dam with ogee shaped concrete spillway having 6 nos. of radial gates of size 9.00 m x 12.06 m was constructed on Bichom river about 3.00 km downstream of the confluence of Bichom and Digien rivers. Another 24.5 m high concrete dam with 2 nos. of radial gates of size 14.00 m x 14.00 m was constructed on Tenga river. Bichom and Tenga rivers are the tributaries of Kameng river. The reservoir water from Bichom dam is conveyed to Kimi powerhouse through 6.7 m diameter modified horse shoe shaped 14.47 km of Head Race Tunnel, 25 m uniform diameter 60 m deep surge shaft and 3.7 km of high pressure tunnels to feed four vertical Francis turbines having capacity of 150 MW each. The water of Tenga reservoir is used in the lean season. The horseshoe shaped concrete lined HRT of 6.7 M diameter was designed to convey 140 cumecs of power draft. The Tunnel Boring was carried out through 8(eight) faces with the construction of 4(four) adits with a total length of 1095 m. In absence of suitable locations for other adits, the tunnel boring activity was carried out for approx. 4 km in HRT from Face II and Face III each.
