The Silkyara-Barkot tunnel, which is a part of the Char Dham Pariyojana, collapsed in November 2023, after a landslide. This tunnel was planned to connect National Highway 134 in the Uttarkashi district of Uttarakhand. It was under construction by the National Highways and Infrastructure Development Corporation Ltd (NHIDCL), and M/Navayuga Engineering Company Limited, at a cost of ` 853.79 crore. While the tunnel was under construction, a part of the 4.5 km long tunnel collapsed and 41 migrant workers got trapped inside the tunnel. After a 17-day long ordeal, all the 41 migrant workers were rescued by a dozen of agencies from the state and the Centre.
The location of the tunnel was on the Yamunotri end of the National Highway 134. The tunnel was meant to connect Dharasu town on the south end to Yamunotri on the north end. The tunnel was to shorten the route by about 20 km. On the day of the incident, the 60-metre-long blockage happened about 200 metres (660 feet) from the entrance of the tunnel.
Various agencies such as the National Disaster Response Force (NDRF), State Disaster Response Force (SDRF), Border Roads Organisation (BRO), NHIDCL, Navayuga, Oil and Natural Gas Corporation, Tehri Hydro Development Corporation, Satluj Jal Vidyut Nigam, Rail Vikas Nigam Limited, Trenchless Engineering Works, as well as the state and district authorities, the Army and the Air Force cooperated in the rescue operation.
Reasons for Collapse
After investigation by the geologists sent by the state government of Uttarakhand, it was found that the tunnel was being built on a geological fault. (Geological fault is a discontinuity in a volume of rock across which there has been significant displacement as a result of rock-mass movement.) Thus, there was hardly any escape shafts for evacuation in case of an emergency. Further, the location of the tunnel is near to the Main Central Thrust which is a major geological fault where the Indian Plate has been pushed under the Eurasian Plate along the Himalayas. Additionally, the tunnel is in the shear zone or a thin zone within the Earth’s crust or the upper mantle which has been strongly deformed due to the walls of rock on either side of the zone slipping past each other. (Shear zones are the places of preferred accommodation of deformation and the relative movement between the crustal blocks in both Phanerozoic and Proterozoic orogens.) According to the BRO, the tunnel was being built in an extremely weak rock mass comprising meta-siltstone and phyllites. All these factors also made the rescue operations more difficult.
Rescue Operations
The Uttarakhand state government immediately launched ‘Operation Zindagi’ for saving the lives of the trapped workers. The rescue operations started by involving shotcreting or spraying concrete through a hose at a high velocity onto a surface. With great efforts, a small supply lifeline was established for providing ration and oxygen supply to the trapped workers. Food items like nuts, roasted chickpeas, etc., were sent to the trapped workers through this pipe. However, with the falling of debris, two workers were injured and the communication with the workers ceased. Once the communication was reestablished, the Chief Minister of Uttarakhand remained in constant touch with the three team leaders who were trapped in the tunnel.
On the seventh day after the tunnel collapse, the prime minister office (PMO) team reached the site to review the rescue operations. The team decided that multiple options should be pursued, including vertical drilling for creating escape channels.
Drilling
The rescue team began drilling with the locally sourced auger drilling machine for creating escape passage through the debris. As the performance of the machine was slow, American auger machine was used to insert 900 mm pipes into the debris. This machine broke and could not drill beyond 22 metres into the debris. Thereafter, horizontal micro-drilling was done to construct a rescue tunnel from Barkot end. However, drilling had to be suspended as cracking sounds were heard.
Furthermore, large metal pieces were hindering machine drilling. Hence, they had to resort to rat-hole mining. Rat-hole miners then tried cutting through the blade stuck inside the rescue pipes and removed it piece by piece. Rat hole miners had to enter the rescue pipes and use hand-held pipes.
After digging the pits, miners descended using ropes or bamboo ladders to reach the coal seams. Of the total of 57 metres of debris that was dug by the rescuers, 12 metres were dug manually by the six rat-hole miners.
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Rat-hole mining is a method of extracting coal from narrow, horizontal seams. It is referred to as ’rat-hole’ as narrow pits are dug into the ground which are just large enough for one person to descend and extract coal.
Rat-hole mining poses several safety and environmental hazards. It is poorly regulated and do not have any safety measures such as proper ventilation, structural support or safety gear for the miners. Due to its hazardous working conditions, environmental damage and several accidents leading to injuries and fatalities, rat-hole mining has faced severe criticism. Though many attempts have been made to ban this type of mining, it still persists because of economic factors and the absence of viable alternative livelihoods for the local population. The National Green Tribunal had banned the practice in 2014 and retained the ban in 2015. However, in Meghalaya, this was the prevalent procedure for coal mining, and hence, the state government had then appealed the order in the Supreme Court.
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A group of three rat-hole miners entered the pipe and crawled to the debris. While one miner did the digging, the second put the debris in the trolley and the third miner kept the trolley on the shaft through which the debris was pulled out. The 800 mm wide pipe was then inserted through the hole. On November 28, 2023, the miners achieved the crucial breakthrough. Once the rescue path was established, the NDRF team and doctors entered through the pipe to reach the trapped workers. Then one by one, each trapped worker was wheeled out on a stretcher through the pipe.
Meanwhile, with the help of Australian tunnel expert, Arnold Dix, a supply lifeline with six-inch pipe was established. An endoscopic camera was pushed through the pipe and the first visuals of the trapped workers emerged on the tenth day. Through this pipe, hot food was served for the first time to the trapped workers.
None of the 41 labourers rescued from the debris was in a critical condition. All the rescued workers were taken to a medical facility in Chinyalisaur Tehsil in Uttarkashi for initial assessment of their health. Then, on November 29, 2023, they were taken to the All India Institute of Medical Sciences (AIIMS), Rishikesh, by Indian Air Force CH-47 Chinook helicopter for further assessment. On December 1, 2023, they were finally declared fit to return home by the hospital authorities.
Strength of the Indian Disaster Management
The successful grand rescue operation showed the progress India has made over the years in relief and rescue operations. From an allocation of ` 1,04,704 crore in the SDRF, the Centre makes allocations to state governments. Between 2014 and 2023, the funds to the NDRF, too, have increased three times from ` 25,036 crore to ` 77,731 crore. In 2021, an additional NDRF fund was created with a corpus of ` 13,700 crore from the Centre and ` 32,000 crore from states. India also created a “Coalition for Disaster Resilient Infrastructure” with more than 100 countries to share experiences with the world.
Inquiry into the Incident
The government of Uttarakhand has formed a six-member expert committee led by the director of the Uttarakhand Landslide Mitigation and Management Centre to investigate the cause of the tunnel collapse. Large-scale construction in a most ecologically fragile zone of the Himalayas is required to complete the Char-Dham Project. Though connectivity and development are important for that region, focus on sustainability and environmental clearances should be of principal concern. This may require a different, more creative design of development for the region and beyond.
Primary investigation report Some key points of the report submitted by the committee are as follows:
- The selection of the site was in incorrect alignment in a shear zone, which is a significant structural feature and represents deformation markers in orogenic belts.
- There was a lack of adequate safety measures during re-profiling and a failure to learn from past accidents. The report unveiled that the tunnel had experienced around 21 landslides prior to the collapse. Therefore, the report has strongly recommended establishing a dedicated tunnel centre for roads and railways to avert any such catastrophes in the future.
- There was an absence of essential sensors and equipment inside the tunnel. These crucial instruments are responsible for monitoring ground behaviour during re-profiling. So, the timely implementation of necessary precautions was hampered.
- The construction company reportedly operated without proper authorisation for their working methods from the authorised engineer, appointed by the NHIDCL. Inadequate monitoring by NHIDCL officials during tunnel construction was also a concerning issue.
- A proper support system was not promptly provided after excavation despite the necessity for re-profiling in the tunnel, which led to precarious conditions. To make the matter worse, rebar ribs were used instead of garter ribs in the landslide-prone area. (Rebar is used to add extra strength to concrete and help avoid cracking when the material shifts. The rib patterns are used to stop the metal from moving around.)
- The report also emphasised on developing a new standard operating procedure (SOP) for tunnel safety and creating a collaborative geological platform, particularly tailored for project construction, specifically in the Himalayan region.
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