SLBC tunnel project passes collapse zone as excavation accelerates

Work on Telangana’s Srisailam Left Bank Canal tunnel has moved beyond the difficult geological stretch where a collapse killed eight engineers, technicians and workers in February last year, Irrigation Minister N. Uttam Kumar Reddy said on Sunday. The minister said the progress would allow additional equipment to be deployed and improve operational efficiency, while safety measures remained in place.

He reviewed the project with engineers, contractors, elected representatives and other agencies in Hyderabad. Reddy said more than 700 metres had been excavated since work restarted in February. About 450 metres had been completed from the Devarakonda outlet and 250 metres from the Srisailam inlet.

The 43.968-kilometre main tunnel was described as nearly 79% complete, with about 9.1 kilometres still to be excavated. The government is targeting completion by June 2028 and water delivery within that timetable. Army tunnel expert Col.

Parikshit Mehra said work from the inlet had initially been slowed because of weak ground, rock bursts and the need to reduce risks. The team diverted around the point where a tunnel-boring machine had become stuck and worked through unstable conditions. The engineers installed 140-millimetre seamless pipes to create an umbrella canopy ahead of excavation.

Reinforced ribs, staged excavation, probe drilling and additional supports were also used, according to the project briefing. The minister said the removal of excavated material over distances of up to 21 kilometres remained a major constraint. When hauling fell behind, material accumulated inside the tunnel and forced work at the excavation face to stop until the backlog was cleared.

Officials said additional drilling equipment and a German locomotive were being deployed. Breakthrough in Tunnel 1 could occur in May or June 2028, while sprayed lining continued. Lining work on the 7.1-kilometre Tunnel 2 had also resumed after a prolonged interruption.