Careful excavation takes tunnel past collapse-hit shear zone
Over 700 metres of progress recorded so far
Additional drilling equipment and German locomotive to accelerate operations
Minister stresses worker safety
HYDERABAD, OCTOBER 04, 2026: Marking a decisive breakthrough in the Srisailam Left Bank Canal (SLBC) tunnel project, excavation has moved beyond a major geological challenge, paving the way for additional equipment deployment and improved operational efficiency while maintaining rigorous safety standards, Irrigation and Civil Supplies Minister N. Uttam Kumar Reddy said on Sunday.
The Minister held a marathon review with elected representatives and senior officials from the three districts of erstwhile Nalgonda on the implementation of key irrigation projects, including the SLBC tunnel. The project is expected to deliver over 30 TMC of water to the region’s parched upland areas, helping end the perennial scarcity they have faced.
MPs K. Raghuveer Reddy and Chamala Kiran Kumar Reddy; MLAs Mandula Samel, K. Jaiveer Reddy, Vemula Veeresham and Anil Kumar Reddy; MLC Shankar Naik; Irrigation Secretary E. Sridhar; Engineer-in-Chief O. V. Ramesh Babu; and the Collectors of Suryapet, Nalgonda, Yadadri-Bhongir and Mahabubabad participated in the meeting.
The Minister commended the efforts of officials and the workforce engaged in the arduous task. Successful passage through the precarious shear zone marked a significant advance in the project, he said.
Uttam pressed for the deployment of additional equipment, improved excavation cycles and close safety monitoring. He sought a credible, closely monitored programme to achieve the June 2028 water-delivery goal.
He directed officials and the contractor to build on the progress through the difficult geological stretch while safeguarding crews working more than 20 km inside the tunnel.
The project team reported an advancement of about 700 metres over the preceding five to six months, comprising approximately 450 metres from the outlet and 250 metres from the inlet. This included carefully negotiated passage through the major shear zone, overcoming formidable geological, technical and logistical challenges.
The 43.968-km main tunnel was reported to be approximately 79 per cent complete, with about 9.1 km of excavation remaining.
Careful passage through unstable ground
Col. Parikshit Mehra, an Indian Army tunnel expert spearheading the tunnel operations, explained that excavation at the inlet had deliberately been slowed during the initial months because of weak ground, rock bursts and the need to prevent another accident. The diversion around the point where the tunnel-boring machine had become stuck had taken the working face through particularly poor geological conditions.
To negotiate the unstable stretch, the team installed 140-mm seamless pipes to form an umbrella canopy, providing protective support ahead of excavation. Reinforced ribs, staged excavation, probe drilling and additional support measures helped control risks as work advanced. Improving rock conditions were enabling a return to normal working conditions deep inside the tunnel.
Equipment push to accelerate excavation
Uttam pressed for sustained progress supported by timely equipment deployment. The project team reported a current combined advance of about eight metres a day, with a sustained rate of seven to seven-and-a-half metres daily. Progress had reached ten metres on one or two days.
A three-arm drilling boomer was already operating at the outlet, where progress was reported to be close to the required pace. Another three-arm boomer was expected at the inlet in October. Electric loaders and advanced excavators were also supporting construction operations.
A locomotive ordered from Germany is expected by the end of October. Its deployment is expected to improve the removal of excavated material and shorten the construction cycle.
Hauling material over distances of up to 21 km remained a major constraint. When removal fell behind, excavated material accumulated inside the tunnel, eventually forcing work at the face to stop until the backlog was cleared.
The team reported that a construction cycle previously taking about 48 hours had been reduced to 20–24 hours. With improved equipment and faster material removal, it is anticipated to bring the cycle down to about ten hours and accelerate progress from late October or early November.
Breakthrough targeted for May–June 2028
The Minister expressed hope that breakthrough in Tunnel 1 could be achieved by May–June 2028. Sprayed lining was being undertaken alongside excavation, allowing much of the lining work to proceed before breakthrough.
Uttam directed that work on Tunnel 2, the balancing reservoir and associated components be completed in time so that unfinished infrastructure did not become an obstacle to water delivery. Tunnel 2, approximately 7.1 km long, had resumed lining work after a prolonged interruption.
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