Chamera Hydroelectric Project stage-II (3×100 MW) design of Dam spillway

Chamera Hydroelectric Project Stage-II is a run-of-the-river scheme for hydro power generation (3×100 MW) on river Ravi utilising gross head of 267m. The project is located around Chamba town, which is a District Head Quarter in Himachal Pradesh State.

The Chamera stage-II project comprises a 43m high Concrete gravity Dam & Spillway, power intake & inlet tunnels, 2 nos underground Sedimentation Chambers, 7.83 km long - 7m horse shoe shaped concrete lined Head Race Tunnel, 3 nos. - 300m long steel lined Pressure shafts, 104.5m high 17.2m dia restricted orifice type Surge Shaft, an underground Power House Caverns, 3.48 km long - 7m horse shoe shaped concrete lined Tail Race Tunnel.

The dam spillway comprises of a 78 m long overflow section (4 bays of 15 m wide & separated with 6 m wide piers). The design discharge is 9000 cumec corresponding to SPF. The spillway crest level has been provided about 3 m above the normal river bed level. Energy dissipation has been provided with the formation of standing wave. The profile of spillway glacis, size & level of stilling basin and alignment of the intake structure were optimized on hydraulic models run at CWPRS Pune. The foundation rock in dam area comprises of phillitic quartzite. The average permeability of the foundation rock is 50–60 lugeons. 6m deep consolidation grouting of entire dam foundation and abutments has been carried out. To increase the seepage path under the dam foundation, one row of 32 m deep grout curtain has been provided on upstream end of drainage and grouting gallery. The stability analysis of Dam block was carried out by using Pseudo Static Method conforming IS:6512–1984. Stability analysis has also been carried out using Simplified Dynamic Analysis Method presented by Shri A.K.Chopra & co-researchers at University of California at Berkely. Instrumentation comprising stress meters, strain meters, pore water cells, plumb lines etc. have been provided in the dam body and foundation of monitor its post construction behaviour.