A geology report had identified a high-risk ‘fault zone’ five years ago when a portion of the SLBC tunnel in Telangana collapsed on February 22, leaving eight workers trapped. The report ordered by Jaiprakash Associates Ltd pointed to weak rocks and possible water retention as well as the warning that some parts of the tunnel could collapse because of decreased rock stiffness and potential seepage of water.
2020 Report Pinned Hazard of SLBC Tunnel Instability
The Tunnel Seismic Prediction (TSP)-303 Plus report, which was submitted in January 2020 by Amberg Tech AG, identified a fault zone between 13,882 meters and 13,914 meters from the tunnel entrance. It reported weak rock masses, zones with water, and possible structural instability.
Jaiprakash Associates Ltd, the company that was awarded the contract for the tunnel in 2005, confirmed the existence of the report but refused to comment any further. “We have no comment on this,” the company said to The Indian Express. The report had highlighted a higher risk of collapse at the area identified and recommended caution.
The seismic analysis entailed propagating waves into the rock mass to determine irregularities. It indicated reduced rock stiffness and possible jointed or sheared rock structures. This warning notwithstanding, it is unknown if this important information was relayed to the Telangana Irrigation Department. A high-ranking SLBC project official alleged he cannot remember going through the report.
The fault zone was located where the tunnel collapsed, and its roof sank about three meters within this area. Persistent flooding within the tunnel has greatly hampered rescue efforts.
Fierce Rescue Operations Ongoing
Following the mishap, teams of rescuers from various agencies, such as the National Disaster Response Force (NDRF) and State Disaster Response Force (SDRF), have been sent. Geophysics involving robotics and seismic surveys is under consideration to try and find the trapped workers and access them. Cadaver canines of the Kerala Police, as well as an NDRF sniffer dog, are also being employed by search groups.
Lamentations Over The Absence Of Geological Surveys
The SLBC tunnel project has come under fire regarding its original geological studies. In accordance with The Indian Express, a 2020 research study co-authored by then Geological Survey of India Director General, Jaiprakash Associates geologist Ritu Deshmukh, and Mandapalli Raju showed that construction of the tunnel started without detailed subsurface exploration.
Because of restrictions within the Tiger Reserve Forest site, authorities were unable to make thorough investigations like excavating drifts and boring boreholes along the tunnel line. Construction then went ahead using limited preliminary appraisals, raising risks.
With rescue efforts now on their 13th day, crews are working to access trapped workers. The accident has prompted serious questions of whether authorities downplayed early indications and how enhanced geological evaluations would have averted the tragedy.