Hyderabad: Excavation on the SLBC tunnel has moved beyond a major geological challenge, Irrigation and Civil Supplies Minister N. Uttam Kumar Reddy said on Sunday. He said the progress clears the way for more equipment and better efficiency. Rigorous safety standards will stay in place.
The Minister held a marathon review with elected representatives and senior officials from the three districts of erstwhile Nalgonda. It covered key irrigation projects, including the Srisailam Left Bank Canal (SLBC) tunnel. The project should deliver over 30 TMC of water to the region’s parched upland areas. That should help end the perennial scarcity they have faced.
MPs K. Raghuveer Reddy and Chamala Kiran Kumar Reddy attended. So did MLAs Mandula Samel, K. Jaiveer Reddy, Vemula Veeresham and Anil Kumar Reddy, and MLC Shankar Naik. Irrigation Secretary E. Sridhar and Engineer-in-Chief O. V. Ramesh Babu were present. The Collectors of Suryapet, Nalgonda, Yadadri-Bhongir and Mahabubabad also took part.
Uttam Kumar Reddy commended the officials and workforce engaged in the arduous task. He said the passage through the precarious shear zone marked a significant advance. The Minister pressed for additional equipment, improved excavation cycles and close safety monitoring. He also sought a credible, closely monitored programme to achieve the June 2028 water-delivery goal.
The Minister directed officials and the contractor to build on the progress through the difficult geological stretch. He asked them to safeguard crews working more than 20 km inside the tunnel.
SLBC tunnel 79 per cent complete after 700-metre advance
The project team reported an advance of about 700 metres over the preceding five to six months. About 450 metres came from the outlet and 250 metres from the inlet. This included careful passage through the major shear zone, despite formidable geological, technical and logistical challenges. The 43.968-km main tunnel is reported to be about 79 per cent complete, with about 9.1 km of excavation remaining.
Col. Parikshit Mehra, an Indian Army tunnel expert spearheading the operations, explained the slow start. The team deliberately slowed excavation at the inlet in the initial months. Weak ground, rock bursts and the need to prevent another accident forced the caution. The diversion around the spot where the tunnel-boring machine got stuck took the working face through particularly poor geology.
Umbrella canopy and boomers help crews push ahead
Crews installed 140-mm seamless pipes to form an umbrella canopy. The canopy supports the ground ahead of excavation. Reinforced ribs, staged excavation, probe drilling and additional support measures helped control risks. Improving rock conditions now allow a return to normal working deep inside the tunnel.
The team reports a current combined advance of about eight metres a day. The sustained rate is seven to seven-and-a-half metres daily, and progress touched ten metres on one or two days. A three-arm drilling boomer already operates at the outlet, where progress is close to the required pace. Another is expected at the inlet in October. Electric loaders and advanced excavators also support construction.
German locomotive due by October-end, breakthrough eyed for 2028
A locomotive ordered from Germany is expected by the end of October. It should improve the removal of excavated material and shorten the construction cycle. Hauling material over distances of up to 21 km remains a major constraint. When removal falls behind, excavated material piles up inside the tunnel. Work at the face then stops until crews clear the backlog.
A construction cycle that once took about 48 hours now takes 20–24 hours. With better equipment and faster removal, the team expects to cut it to about ten hours. It anticipates faster progress from late October or early November.
The Minister hopes the breakthrough in Tunnel 1 can come by May–June 2028. Crews are spraying lining alongside excavation. Much of the lining work can therefore finish before the breakthrough.
Uttam Kumar Reddy directed that work on Tunnel 2, the balancing reservoir and associated components finish in time. Unfinished infrastructure should not obstruct water delivery. Tunnel 2, about 7.1 km long, has resumed lining work after a prolonged interruption.
