At approximately 5 am on the morning of Diwali, 12 November, a segment of the Silkyara Tunnel under construction on Chardham Road in Uttarakhand collapsed. The incident occurred around 200 meters from the Silkyara end, where forty-one tunnel workers were working. Although the precise cause of the collapse is under investigation, the tale of the rescue operation merits attention, highlighting the numerous commendable aspects of the mission.
On the fateful day of the initial 40-meter collapse, all hope for survivors seemed lost. As the site team mourned the tragedy, a sudden rush of water emerged from a surviving water pipeline, miraculously untouched by the debris of the collapsed rocks. To everyone’s relief, the men on the opposite side of the pipeline were unharmed and managed to send a life-affirming signal using a water pump. Swiftly, the site team employed an age-old method, using the hollow pipe as a conduit to communicate with those on the other end. It marked the first success in what would prove to be a challenging and arduous journey ahead.
Soon enough, the rescue team discovered that all 41 workers had miraculously remained safe, having moved away from the collapsed zone. They were alive and had relocated to the nearly 2 km of tunnel accessible on their side, much of which was protected by a thick concrete lining. In their frenzy to swiftly rescue their colleagues, the site workers, deploying excavators and loaders, began excavating the muck pile of debris. However, their actions inadvertently triggered a secondary collapse, expanding the affected area from 40 to 60 meters. Recognizing the need for a more prudent approach, senior engineers and leadership took charge of the site despite initial resistance from workers who believed that rapidly clearing the debris was the quickest way to evacuate their friends. They did not realise how precariously the tunnel was poised inside the fragile phyllites and meta sandstones, making any hasty measures potentially catastrophic. The risk of the tunnel collapsing or unfolding like a zipper was too great, rendering a safe evacuation nearly impossible.
Gradually, rescue leadership restored normalcy, and the small water pipe served as a conduit for delivering dry fruits and other essential food items to the trapped workers. Fortunately, they have access to electricity and drinking water courtesy of a heavily armoured electric cable and the natural water sources within the tunnel.
The site authorities swiftly focused on a potential solution and deployed a trenchless machine equipped with an auger to drill in the site. However, the initial machine proved insufficient for drilling through the challenging conditions. Subsequently, a more robust American Auger cum Pipe Jacking Machine was brought in. An auger, essentially a helical screw designed to remove soil from an opening as it is thrust into a consolidated mass, was employed in this instance to navigate through the tunnel muck, which was intertwined with steel supports from the collapsed tunnel lining.
As the machine was being mobilised and its foundation established, additional food supplies were delivered to the trapped workers through the water pipeline. It was achieved by pushing packets with compressed air through the pipeline, ensuring sustenance reached those inside while the rescue operation progressed.
On 18 November, around three in the afternoon, panic struck as a cracking sound resonated in the tunnel, indicating movement in the structure above. More cavities were forming, creating a dynamic and potentially seismic event. In response, an alternative food pipeline, with a diameter of 150 mm, was promptly devised to ensure a continuous supply of food inside the tunnel. Despite requiring two attempts over two days, a new pipeline was successfully laid.
To safeguard the ongoing rescue effort, precautionary measures were implemented, including the creation of a covered escape route for the rescue team operating on the tunnel face. A series of precast concrete boxes (culvert sections) and hume pipes were strategically arranged from the tunnel face to a point 67 meters away, providing a safe escape route for the rescue crew in the event of an emergency. Additionally, plans were made to further reinforce the tunnel’s primary lining, although this aspect could only be addressed later
Once the safety measures and food pipelines were in place, the foundation for the American Auger was ready, and the augering process commenced on 22 November. A 900 mm pipe was being driven, and the auger was tasked with creating space for it. As anticipated, the auger machine made initial progress but encountered steel obstacles. Subsequently, the auger had to be extracted multiple times, and welders entered the pipe to cut through the steel ahead of it. It was necessary to create additional space for subsequent advancements in the drilling process.
After advancing 21 meters, the auger encountered another obstruction, and it became evident that the pipe jacking mechanism lacked sufficient thrust to push the pipe further. The excessive skin friction between the pipe and the tunnel muck posed a significant challenge. The decision was made to extract the entire auger and introduce an 800 mm diameter pipe inside the existing 900 mm pipe to mitigate overall skin friction. New pipes were inserted by welding sections ranging from 2.5 meters to 6 meters in length. This process took an additional 24 hours before augering could resume.
As anticipated, the auger encountered more steel during the drilling process. It led to repetitive cycles of removing the auger, cutting through the steel, and resuming augering. However, the auger became stuck once more, this time approximately 45 meters inside. During a subsequent attempt to push through, the foundation frame gave way. To address this, the foundation was reinforced by incorporating rock bolts and surrounding the frame with concrete for added stability.
At this point, a Ground Penetrating Radar (GPR) scan was conducted from the pipe’s face, defying technical predictions that no steel would be encountered. Despite receiving advice to the contrary, and in an effort to expedite the operation, the decision was made to reinsert the auger. Despite instructions to the machine operators to limit torque and thrust, ensuring compliance proved challenging. Unfortunately, the auger head drew in numerous steel elements, including lattice girders and grout pipes, causing damage to some sections of the inserted 800 mm diameter pipe. It was only at this delayed stage that the decision was made to extract the auger and proceed with rat mining or drifting instead.
The arduous task of extracting the auger faced an unfortunate setback this time. After successfully removing 15 meters, the auger shaft broke, rendering the machine incapable of pulling the auger any further. In a moment of collective dismay, everyone was stunned, realising that all the effort invested over the past few days had suddenly become futile. This setback occurred almost two weeks after the initial collapse.
Was the strategy dependent solely on one approach? No, the strategy devised by MoRTH (Ministry of Road Transport and Highways) was prudent and founded on a scientific approach. Simultaneously with the ongoing augering efforts, multiple alternative options were being actively pursued. These included exploring a smaller tunnel through an unexcavated passage from the Barkot side by THDC Ltd. Other initiatives involved ONGC’s endeavour to construct a 300-meter-high inclined vertical rescue shaft with a two-foot diameter from a point on the hill, approximately 3 km from the Silkyara end. SJVNL was working on a 90-meter-high vertical rescue shaft with a 1.2-meter diameter, located 320 meters away from the Silkyara end. RVNL was involved in constructing a 90-meter-high vertical backup food supply shaft with a 200 mm diameter, situated 300 meters away from the Silkyara end.
Additionally, RVNL explored a 170-meter-long horizontal tunnel using a micro Tunnel Boring Machine (TBM) of 1.2-meter diameter. There were also considerations for side drift options from the face of the collapse, utilising precast rectangular and circular frames or constructing a full-size side drift employing grouting, tunnel shotcrete equipment, and a military bobcat excavator. The latter had already been brought to the site by a platoon from the Army Sappers contingent under the command of the officer leading the 201 Engineer Regiment, the Madras Sappers.
The Border Roads Organisation demonstrated exceptional efficiency by swiftly constructing a 1200-meter approach road for vertical drills by RVNL and SJVNL by 20 November, even as the drill rigs were still mobilised. Expert assessments, including those by Arnold Dix, President of the International Tunnelling Association, and Col Parikshit Mehra, renowned for his work on the Atal and Sela Tunnels, were conducted at hilltop locations. Suitable points along a nala (rivulet) with competent rock were identified for installing the drill rigs.
By 26 November, the drill rigs were successfully set up at designated locations, and drilling operations were initiated. Progress was notable, with the 200 mm diameter pipe by RVNL reaching a depth of 72 meters, while the 1.2 m diameter pipe by SJVNL had reached nearly 35 meters by 27 November. The mobilisation of equipment for the micro Tunnel Boring Machine (TBM) and the ONGC drill rig was efficiently conducted, utilising green corridors and Air Force cargo planes where feasible. This comprehensive effort reflected a national commitment, sparing no effort to explore all available options.
In preparation for potential scenarios, the sappers had already created rectangular and circular drift segments, ready to undertake an independent manual side drift if necessary. Recognising the passage of time, plans for a larger drift using a bobcat excavator were also developed, complete with basic support elements, ensuring readiness to pursue these options whenever required.
The Secretary of MoRTH, who had been overseeing progress from Delhi, personally visited the site on 22 November to observe and supervise the advancement of each option. His composed demeanour, coupled with his technical expertise as an IITian and the assistance of domain experts, played a crucial role in ensuring a graduated response with mitigated risks. The Secretary remained determined despite the best and seemingly least risky approach becoming uncertain.
The vertical drills were continued, which posed the risk of puncturing an aquifer from the top of the tunnel. Although the smaller 200 mm diameter drill, which reached a depth of 72 meters, did encounter water, this did not dissuade the leadership from halting the progress of the larger 1.2-meter diameter drill, recognising that time was running out.
Was time slipping away? Not at all. The supplementary food pipe effectively facilitated sufficient stocking of food for the stranded labourers. Continuous 3D monitoring indicated overall stability in the tunnel, prompting the implementation of additional safety measures. The prevailing seismic activity did not significantly impact the tunnel’s integrity—enhanced communication channels, including the installation of cameras, improved interactions with the trapped workers. Indeed, during a late-night conversation with a trapped survey professional, it became apparent that the unlined section of the tunnel, spanning from 260 meters to 280 meters, had experienced notable deformations.
Envisaging the trapped workers using the excavator, which had been with them for the past few meters, might have resulted in disaster. Similarly, a vertical breakthrough from the top could have triggered a collapse or introduced water, transforming the phyllite rock into a malleable paste. The safety of the workers relied on the tunnel remaining relatively undisturbed. A worker who had previously experienced a similar situation was present to offer comfort and leadership. Telecommunication facilitated communication between the workers and their families, with many senior individuals maintaining a continuous dialogue to ensure high morale among the trapped workers.
Devbhoomi posed a challenge to the rescue team but also bestowed hope and blessings with each testing moment. The welders and gas cutters exhibited exceptional skill and promptly commenced the task of cutting out the auger. Although the initial hours witnessed a painstakingly slow pace, the subsequent hours witnessed a miraculous acceleration. Laser cutters, plasma cutters, and magna cutters were swiftly flown into the site. The auger was successfully cut out, the final 1.5 meters of the damaged pipe and auger bit were removed, and the manual effort of rat hole miners was initiated on 28 November.
Gradually yet consistently, the miners played a pivotal role in creating space for the pipe to be pushed, instilling enough hope to warrant halting the risky 1.2-meter diameter vertical drilling option at a depth of 42 meters. Although there was a moment of false alarm when only the last 2.4 meters remained, it took just a couple of additional hours to successfully push the 800 mm diameter pipe through. The trapped workers were prepared to receive the pipe, and some crawled through. Utilising a safe stretcher contraption devised by the NDRF, all the trapped individuals were safely extracted within a matter of hours, marking the end of a 17-day-long ordeal.
Medical assistance, including psychiatric support, was provided at the triage setup inside the tunnel. Uttarakhand Chief Minister Pushkar Singh Dhami and Union Minister of State for MoRTH, General VK Singh (retired Chief of the Army Staff), warmly welcomed the liberated workers.
The entire nation had rallied its resources for the sake of 41 invaluable Indian lives. The Secretary of MoRTH and MD of NHIDCL displayed exceptional, mature, and composed leadership even in moments of adversity, while officers from the Prime Minister’s Office (PMO) extended unwavering support. Major technical organisations such as SJVNL, RVNL, ONGC, THDC, and many others wholeheartedly contributed to the operation. The Army, Air Force, and Border Roads Organisation stood in unity with NHIDCL and MoRTH, executing the operation with the utmost professionalism. This operation will continue to serve as an inspiring example of India’s national strength.
Could this incident be preventable? What measures can be implemented to prevent such occurrences in the future? Answering these questions requires a nuanced and in-depth exploration of the various aspects of today’s tunnel construction industry. A comprehensive analysis is needed, considering the government’s perspectives and contractors’ insights. However, this is a narrative for another day as the nation rightfully celebrates this truly commendable feat!
A Rescuer’s Personal Account
One Comment
Manish Kr MEENA
CSIR-CIMFR Roorkee Team was called up by the PMO for continuous monitoring of the ground vibration induced by the movement of HEMM’s. That helped in the installation of the drill rig at the designated location.