The run-of-river hydro scheme is located on the Alaknanda River, a major tributary of the Ganga River, in the state of Uttarakhand, around 500km north-east of Delhi. The main contractor, Hindustan Construction Co Ltd, is building dams, head race, tail race, diversion and spillway tunnels, vertical shafts and a powerhouse with a generating capacity of 444MW.
The 9.86m diameter Terratec hard rock double shield TBM is constructing the 13km low-press head race tunnel. Terratec has also supplied a continuously advancing tunnel conveyor for the project.
The alignment for the Vishnugad-Pipalkoti Hydropower project comprises Dolomitic limestone (33%) and slates (64%), with the remaining 3% passing through critical geological sections. These include thrust zones, with shallow overburden of 150m; five shear zones; and three fault zones.
The TBM cutterhead features 19in disc cutters and 12 large bucket openings. The 4,200kW electric main drive is designed to help the TBM to excavate through the expected hard rock, delivering a torque of over 22,000kNm. As the TBM progresses, universal reinforced concrete lining rings, measuring 1,500mm wide and 350mm thick, will be installed. The lining rings consist of five segments plus a key.
The TBM also features a high-speed regripping system, single-shield advancing mode, high-pressure emergency thrust, and flood control doors. The key components of the TBM were manufactured in Australia and Japan, while the assembly took place at Terratec’s facilities in China.
