‘Fragile terrain not the cause of tunnel collapse but an excuse’

In November 2023, the under-construction Silkyara Bend-Barkot tunnel in Uttarakhand collapsed, trapping 41 workers under the rubble. The rescue operation in the 4.5 km tunnel lasted 17 days and involved multiple teams. Australian geologist Arnold Dix, who is also the president of Switzerland-based International Tunnelling and Underground Space Association, as well as an engineer, a barrister and a farmer, assisted in the mission at India's request. Dix has now written a book on the incident. In an interview with Aditya Misra, Dix says the mishap was a failure to adapt construction methods to the rock conditions encountered. Excerpts:

Aditya Misra (AM): How do you remember the incident one year after it happened?

Arnold Dix (AD): The Uttarakhand rescue feels as vivid as ever—a testament to what can be achieved when people from different backgrounds, disciplines, cultures and roles come together with a shared purpose. This was not just about engineering or problem-solving; it was about how humanitarian missions succeed because of the unyielding determination of countless individuals in a bigger team.

I promised everyone would be rescued and not one of us would get hurt. Our team believed that we could make the impossible possible—and we did. What stands out most was the collaboration across the multiple rescue organisations and teams.

Engineers, miners, welders, cutters, drivers, cooks and technicians all played an essential part in making the rescue succeed. Every challenge we faced was met with collective creativity and resolve.

I am so proud to have been part of the team. The rescue operation also reinforced a truth I have seen time and again: greatness is not achieved alone. The work of hundreds of people, each contributing their unique expertise, wove together to create a miracle. It also highlighted how cultural ties amplify human connections. The Indian community’s emotional embrace of this rescue effort reminds me that saving lives transcends borders and builds bonds far greater than we might otherwise imagine.

AM: What were the safety oversights in the way the project was being carried out? Or can such projects not be undertaken without any risk to the people involved?

AD: The scars of 21 prior collapses in the tunnel were stark warnings that things had gone wrong long before this disaster struck. So many prior collapses mean no lessons had been learned. Each collapse should have been an opportunity to pause, re-evaluate, and refine systems and construction methods.

Feasibility studies must take centre stage in such projects, ensuring that contractors, engineers and project managers understand the mountain’s complexities before tunnelling begins.

Contracts must anticipate and allow flexibility, embedding systems that monitor and dynamically respond to how the mountain behaves during construction. A rigid approach, prioritising speed or cost over adaptability, puts both lives and infrastructure at risk.

The collapse underscored the importance of collaboration at every level. It is not just about engineers or contractors—it is about bringing together geologists, safety specialists, project managers and policymakers to create systems that align visions with projects that can be built.

Tunnels must respect the mountains they pass through. They should be built in harmony with the rock, responsive to its behaviour. This unified approach, combined with smarter contracts and feasibility studies, is key to preventing disasters like this in the future.

AM: Would you blame accidents, such as this one, on the fragile landscape of the Himalayas or on the kind of technologies used for development activities like laying roads or tunneling?

AD: The Himalayas are ancient, powerful and unpredictable. Surface roads are prone to landslides and fatal crashes, making tunnels a safer option for pilgrims and locals. Tunnels have been successfully built in earthquake-prone mountains worldwide, so blaming the landscape is a distraction from the real issue: proper construction and design. This collapse was not a failure of technology but a failure to adapt construction methods to the rock conditions encountered.

Technologies are tools—they must be used thoughtfully and in harmony with the environment.

Projects must also include robust monitoring systems and contracts that empower teams to adapt methodologies based on observed rock behaviour. Collapses like this are entirely preventable when engineering teams prioritise collecting and interpreting real-time data and adjusting methods dynamically as conditions change.

Listening to the mountain, respecting its rhythms, and fostering collaboration among team members is what ensures success. The fragile terrain was not the cause of the collapse—it was an excuse.

AM: Can you cite examples of advanced technologies being deployed elsewhere in the world to minimise the risks of such accidents?

AD: Advanced technologies have revolutionised tunneling worldwide, but success ultimately depends on finding solutions that are in harmony with the environment.

In the Himalayas, where geology is variable, fragile and dynamic, this means achieving a balance between the rock’s natural behaviour and the demands of construction. Tunnels must work with the mountains, not against them. This requires careful monitoring of how the rock behaves in real time as the tunnel progresses, adapting support systems to respond to the mountain’s natural movements.

Pre-project feasibility studies should guide this process, providing a clear understanding of the mountain’s dynamics and informing strategies that anticipate challenges and solutions.

When I joined the Uttarakhand rescue operation, I worked alongside a remarkable team of Indian experts whose skill and experience set the foundation for success. Together, we adapted to the challenges we faced, finding solutions that honoured the unique environment we were working within.

For future projects, it is crucial to foster a commercial and regulatory environment that encourages contractors to adjust their construction methodologies and support systems based on the observed behaviour of the rock.

It is also essential that the workers building the tunnel are well-trained and competent in the skills needed to build a tunnel safely. All around the world, there is a widening gap between the sophistication of tunnel designs and the skill level of those employed to build them. Our tunnel workers need more and better competency training.

AM: Were there challenges unique to this rescue operation?

AD: This rescue was unlike anything I had experienced before—not only because of the geology of the Himalayas, with its complexity, but also because of the human and cultural challenges.

The spiritual significance of the region added a profound dimension to the operation. Local priests attributed the collapse to the razing of a small temple near the tunnel entrance, and these beliefs influenced the emotional and spiritual dynamics. This demanded not just technical solutions but also empathy and cultural understanding.

The immense emotional strain on the families of the trapped men also made clear communication and transparency essential. It was not enough to rely on advanced tools or engineering expertise; we had to ensure every stakeholder felt heard and included. The operation’s success was not just about technology or engineering—it was about teamwork.

AM: How would you describe the pressure to save lives? What was the feeling after the last of the 41 men was tunneled out?

AD: The pressure was immense—every decision carried the weight of lives. The ever-present risk of harming the trapped men or the rescuers was a constant test of our resolve. Every individual understood the stakes and brought their best to the table. When one approach failed, another was proposed; when morale wavered, someone else stepped up to reignite hope.

After the last man emerged, the emotions were overwhelming. Relief, pride, and joy were mixed with quiet gratitude for the people who made it happen. For me, personally, I felt contentment that has never left me.

‘That particular mountain was about as angry as I have ever seen…’

In a sense, tunnellers have to trick the mountain by using complex physics. We have to work out how to precisely distribute the crushing load of the mountain around the tunnel in such a way that it does not cave in.

Make no mistake. Modern tunnelling can be done very safely, as it is across the world every single day. Please do not find yourself terrified to drive through one on your way to and from work. Safe tunnelling is one of the greatest achievements of the twentieth century.

When you enter the remnants of a tunnel after something dire has taken place, like a collapse or landslide, you might notice something quite stark. What should be a perfect semicircle or semi-oval depending on its size­ – the sign of perfectly distributed pressure – now looks like someone has taken to it with a crowbar. You will notice the top is sagging and the sides are warped. We call this ‘convergence’. It describes the tunnel naturally healing itself.

Convergence is a sure sign that the mountain is about to completely reclaim the piece of itself that humans have clawed away. It has not been tricked. The mountain has cottoned on to what humans are trying to do and it is pretty pissed off about it.

This is exactly what I saw the first time I went inside the Silkyara Bend–Barkot tunnel. That particular mountain was about as angry as I have ever seen in my three-decade-plus career working underground...

As the elected president of the International Tunnelling and Underground Space Association, the world’s largest underground industry group, I was notified of the collapse within hours. I sent out an unofficial alert to the key technical members I trusted the most and began assembling an unofficial team of specialists who could be called on if and when needed. Experts from across the globe began sharing knowledge and advice with me, which I relayed to the Indian specialists, who were both onsite and working from afar, preparing a response. My call was not official – it was personal. We of the underground are like a global tribe – we help each other – we need to.

(Excerpted with permission of Simon & Schuster India)

This was first published in the 16-28 February, 2025 print edition of Down To Earth