SLBC tunnel moves past toughest stretch, works set to gather pace
HYDERABAD: Srisailam Left Bank Canal (SLBC) tunnel project has made important progress. Specifically, excavation has moved past a major shear zone, a challenging geological section, which now allows additional tunneling equipment to be deployed and improves construction efficiency. Meanwhile, Telangana Irrigation Minister N. Uttam Kumar Reddy said on Sunday that safety protocols are being maintained at a high standard.
Earlier, the Minister met with elected representatives and senior officials from the three districts of the erstwhile Nalgonda region to review major irrigation projects, including the SLBC tunnel. The project is expected to bring over 30 TMC (thousand million cubic feet) of water to drought-prone upland areas, thereby helping to address the chronic water scarcity they have faced for years.
The Minister praised the officials and workforce for their efforts, stating that successfully negotiating the shear zone was a major milestone. Consequently, he called for additional equipment, improved excavation cycles, and strict safety monitoring to achieve the target of water delivery by June 2028. He further instructed officials and contractors to sustain progress through the geologically complex section and ensure worker safety during tunnel operations.
Over 700 metres of progress
The project team reported advancing about 700 metres in the last five to six months, approximately 450 metres from the outlet and 250 metres from the inlet. This included passage through the major shear zone, which posed significant geological, technical, and logistical challenges. The main tunnel is 43.968 kilometres in length and is now approximately 79 percent complete, with about 9.1 kilometres of excavation remaining.
Col. Parikshit Mehra, a tunneling expert from the Indian Army, explained that excavation at the inlet was deliberately slowed due to weak strata and the risk of rock bursts. As a result, the team implemented a diversion around the location where the tunnel-boring machine had become lodged, requiring them to advance through particularly poor geological strata.
To traverse the unstable section, the team installed 140-mm seamless pipes to construct an umbrella canopy, providing pre-excavation support to the tunnel face. Additionally, they used reinforced ribs, staged excavation, probe drilling, and additional support measures to mitigate risks. As rock conditions improved, the team resumed standard tunneling operations deep within the tunnel.
Equipment push to accelerate excavation
The project team said they are currently achieving a daily advance of about eight metres, typically maintaining a rate of seven to seven-and-a-half metres per day, on some days, progress has reached ten metres. For instance, a three-boom jumbo drill is already in operation at the outlet and is meeting the required tunneling pace. Another jumbo drill is expected at the inlet in October. Electric loaders and advanced excavators are also supporting tunneling activities.
A tunnel locomotive ordered from Germany is expected to arrive by the end of October. This equipment will facilitate muck removal and accelerate the construction schedule. However, hauling excavated material up to 21 kilometres remains a significant logistical challenge. When muck removal falls behind, debris accumulates in the tunnel, occasionally forcing work stoppages until the backlog is cleared.
The team reported that the construction cycle, which previously took around 48 hours, has been reduced to 20–24 hours. With improved equipment and more efficient muck removal, they expect to shorten the cycle to about ten hours, thereby accelerating progress from late October or early November.
Breakthrough targeted for May–June 2028
The Minister said he anticipates a breakthrough in Tunnel 1 by May or June 2028. Workers are applying shotcrete lining concurrently with excavation, so much of the tunnel lining will be completed prior to breakthrough. Meanwhile, Uttam directed the team to complete Tunnel 2, the balancing reservoir, and associated infrastructure on schedule to avoid delays in water delivery. Tunnel 2, which is about 7.1 kilometres long, has resumed lining operations after an extended hiatus.
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.
