SLBC Tunnel Collapse: The Ongoing Struggle in One of India’s Toughest Rescues | TDG Explainer

Rescue operation at Telangana’s Srisailam Left Bank Canal (SLBC) tunnel has become a critical stage with several agencies toiling day and night to bring out the 8 trapped workers. The accident, which took place during an ongoing construction process, has been particularly tricky because of the water, rubble, and metal pipes within the tunnel.

More than 500 personnel, such as the National Disaster Response Force (NDRF), State Disaster Response Force (SDRF), and the Indian Army and Navy, are part of this dangerous SLBC tunnel rescue mission. Expert “rat-hole” miners have also been deployed to aid manual excavation. Despite their efforts, the process has been slow owing to water leakage and blockages from the wreckage of tunnel boring machine (TBM) equipment. The rescue teams are racing against time to keep both the workers who are trapped and those involved in the rescue safe.

But before going into the details of the operation, we should know how the workers trapped inside this under-construction tunnel.

How the Workers Got Trapped in SLBC Tunnel?

The Jaiprakash Associates Ltd. SLBC tunnel project was under-construction when a sudden collapse happened inside the tunnel near Domalapenta in Nagarkurnool district, approximately 14 kilometers from the tunnel’s inlet. It is reported that part of the tunnel collapsed because of geological instability and possible structural flaws. This trapped several workers deep inside the tunnel with poor access to air, food, and water.

At the time of the collapse, about 50 workers were inside the tunnel. Of these, 43 managed to escape, 29 were unhurt, while 13 sustained injuries but were able to exit with assistance.

Unfortunately, 8 workers remained trapped due to the sudden nature of the collapse and the ensuing debris and flooding.

Initial investigation suggest that the collapse could have been caused by too much seepage of water, which made the walls of the tunnel weak. Matters were made worse when construction gear, such as parts of the Tunnel Boring Machine (TBM), became jammed in the rubble, blocking the way for rescuers stuck inside.

What are the Problems in the Rescue Operation?

The rescue mission has been confronted with several challenges:

Water Seepage and Slush Formation: Water and slush inside the tunnel have rendered excavation very challenging. Water Pumps have been employed to drain water, but seepage continues at a high rate.

Blocked Pathways: The collapse has caused huge debris, including metal components of the TBM, to block the pathways, hindering easy access for workers.

Geological Uncertainty: The structural integrity of the existing tunnel is unknown. Any further excavation or drilling has the risk of causing more collapses, which will put the trapped workers and rescue teams in danger.

Limited Space: The tunnel’s narrow structure limits the mobility of heavy machinery, making teams use manual excavation in some sections.

Two cadaver dogs from the Kerala Police, known for their ability to detect human scents even from depths of up to 15 feet, have been introduced to assist in the operation.

These Belgian Malinois breed dogs, along with their handlers, arrived by air and entered the tunnel on March 6. Their deployment followed a request from the National Disaster Management Authority (NDMA) to the Kerala State Disaster Management Authority, aiming to enhance the search for the missing workers.

SLBC Tunnel Collapse: Was a 2020 Fault Zone Warning Overlooked?

A 2020 Tunnel Seismic Prediction (TSP)-303 Plus report prepared by Amberg Tech AG had already detected a fault zone at 13,882 meters to 13,914 meters from the tunnel mouth, indicating weak rock masses, water infiltration, and structural instability. The warning was ignored, and the Srisailam Left Bank Canal (SLBC) tunnel collapse took place exactly in this zone, which raises questions about whether the risks were properly addressed.

The Jaiprakash Associates Ltd, to whom the project was handed-over in 2005, admitted the report’s presence but refused to comment further. The report had clearly indicated a greater risk of collapse and recommended caution in construction.

The seismic study, which entailed propagating waves into the rock mass, indicated low rock stiffness and potential jointed or sheared structures, suggesting potential dangers. But it is not clear if this information was communicated properly to the Telangana Irrigation Department.

A top SLBC project official, when asked, said that he could not remember going through the report, creating more doubts about its use in project implementation. The absence of adequate mitigation measures could have led to the disaster.

The tunnel collapse caused its roof to sink by almost three meters, exactly in the fault zone that was located. Moreover, constant flooding within the tunnel has also greatly hindered rescue efforts, making it one of India’s most difficult rescue operations so far.

Uttarkashi Tunnel Tregedy

This tunnel collapse in SLBC has been compared with the Uttarkashi tunnel tragedy in November 2023, when 41 labourers got trapped in the fallen part of Silkyara Bend–Barkot tunnel in Uttarakhand. The rescue operation took more than 17 days with a series of methods, involving piercing through the wreckage and feeding supplies through a pipe.

Contrary to the case of the Uttarkashi collapse, when it was poor geology, SLBC’s tunnel rescue mission has been combating ingress of water and metal junk. Both the examples, nevertheless, point out that strong safety regulations are must, and preparedness for emergency purposes in underground digging projects has to be increased.

Major Rescue Operations in India

Meghalaya Mining Accidents

Illegal “rat-hole” mining practices in Meghalaya have led to several tunnel collapses. Notably, in 2018, 15 miners were trapped in a flooded mine, and in 2021, six miners died in a similar incident.

These incidents underscore the dangers associated with unregulated mining operations in the region.

Assam Coal Mine Flooding (2025)

9 miners were trapped in a 300-feet deep illegal coal mine after accidentally breaching a water source, leading to rapid flooding. One body was recovered on January 8, 2025, while the remaining five missing miners’ bodies were found after 44 days on February 19, 2025.

Raniganj Coal Mine Rescue (1989)

A group of miners breached an abandoned, waterlogged mine, leading to rapid flooding. Of the 232 workers, 161 escaped, but 71 remained trapped. 65 miners were successfully rescued, while six lost their lives. Gill was awarded the Sarvottam Jeevan Raksha Padak for his bravery.

Collapse Need Attention

The SLBC tunnel collapse again focused attention on the hazards inherent in large infrastructure projects and the need for safety measures to be enhanced. In the meantime, rescue operations remain ongoing, reminding everyone of the need for due planning, checks, and response systems to preclude such mishaps in the future.

While the world observes, hope continues to be pinned on the workers trapped being safely evacuated and learning from this disaster, informing improved tunnel construction and crisis management in India and the wider world.