Work on the SLBC tunnel is progressing past the problematic section and is set to pick up pace

Irrigation Minister N. Uttam Kumar Reddy at a meeting on SLBC tunnel project work in Hyderabad on Sunday. | Photo credit: By arrangement

Excavation of the Srisailam Left Bank Canal (SLBC) tunnel has moved past a major geological obstacle, the section where the tunnel caved in and claimed the lives of eight engineers, technicians and laborers in February last year, paving the way for deployment of additional equipment and improved operational efficiency while maintaining strict safety standards.

A major breakthrough in the implementation of the SLBC tunnel is now expected to pick up pace towards the government’s target of completing it by June 2028, Irrigation Minister N. Uttam Kumar Reddy said at a meeting on Sunday where he reviewed the progress of the project with engineers, agencies involved in the implementation and elected representatives of the areas that will benefit from the project.

The Minister appreciated the efforts of the officials and employees involved in the challenging task and successful passage of the work through the precarious and landslide-prone zone. He said over 700 meters of tunnel had been excavated since work resumed in February this year. To speed up operations, they deployed additional drilling equipment and a German locomotive.

Technicians inside the SLBC tunnel. | Photo credit: By arrangement

Pushing for deployment of more equipment, better excavation cycles and close monitoring of safety, the minister sought a closely monitored program to achieve the water supply target by June 2028. He tasked officials and the work agency (contractor) to build on progress through the difficult geological section while protecting crews working more than 20 km inside the tunnel from the Devarakonda side.

He said the project team has reported about 700 meters of progress in the previous five to six months, which includes about 450 meters from the exit (Devarakonda side) and 250 meters from the entrance (Srisailam side). It involved a carefully negotiated passage through a major shear zone, overcoming formidable geological, technical and logistical challenges.

The 43.968 km main tunnel is now almost 79% complete with about 9.1 km of excavation remaining. Colonel Parikshit Mehra, an Indian Army tunneling expert who led tunnel operations, explained that excavation at the inlet was deliberately slowed during the first months due to weak ground, rock cracks and the need to prevent another accident.

The diversion around the point where the tunnel boring machine got stuck has gone through the face in particularly bad geological conditions. To overcome the unstable section, the team installed 140mm seamless pipes to create an umbrella canopy to provide protective support against excavation, he explained, adding that reinforced ribs, progressive excavation, boreholes and other support measures helped control risks during the work.

The minister stated that the main limitation remains the removal of excavated material over distances of up to 21 km. When removal was delayed, the excavated material piled up inside the tunnel, eventually forcing a halt to work on the casing until the backlog could be cleared. Breakthrough in Tunnel 1 could be achieved in May-June 2028, and sprayed lining was taking place concurrently with the excavation. Work on lining 7.1 km of Tunnel 2 has also resumed after a long interruption, he said.

Published – 04 Oct 2026 21:01 IST