A significant step has been taken in the Vishnugad-Pipalkoti Hydropower Project in India as tunnel boring operations have kicked off. This hydroelectric project is located along the Alaknanda River, which is a key tributary of the Ganga River, in the Uttarakhand state, positioned about 500 kilometers northeast of Delhi.

Hindustan Construction Co Ltd, the main contractor for the project, is responsible for a range of construction activities including building dams, creating the head race and tail race tunnels, setting up diversion structures and spillways, constructing vertical shafts, and establishing a powerhouse with a capacity of 444MW.

The central focus of the construction effort involves the use of a specialized Terratec hard rock double shield Tunnel Boring Machine (TBM) with a diameter of 9.86 meters. Terratec has also provided a tunnel conveyor system that ensures a continuous and efficient construction process.

In terms of geology, the project's route is primarily composed of Dolomitic limestone (33%) and slates (64%). Negotiating the remaining 3% of the terrain presents some geological challenges, including thrust zones with a shallow overburden of just 150m, five shear zones, and three fault zones.

The TBM itself is equipped with a cutterhead featuring 19-inch disc cutters and 12 spacious bucket openings. Powered by a robust 4200kW electric main drive, the TBM is well-equipped to tackle the expected tough rock conditions, providing a torque of over 22,000 kilonewton-meters. As the TBM progresses, it will leave behind a trail of reinforced concrete lining rings, each measuring 1,500mm in width and 350mm in thickness.

The TBM boasts advanced features including a high-speed regripping system, single-shield advancing mode, a high-pressure emergency thrust capability, and flood control doors. The essential components of the TBM were sourced from Australia and Japan, while the assembly took place in Terratec's facilities in China.

by waterpowermagazine