Factors that marked the rescue of the 41 workers trapped in a tunnel in India

Small landslides, breakdowns and obstructions marked the rescue of 41 workers trapped in a tunnel under construction in the north of the Indiathat 17 days after they were trapped, they managed to emerge alive this Tuesday after a long operation that was plagued with adversity.

The optimism of the rescuers, who from the beginning wrongly envisioned a simpler operation, was progressively overshadowed by the facts on the ground, with a hard layer of rubble that was not so easy to penetrate and required two tunnel boring machines, hundreds of workers, and specialized miners to make their way into it.

Immediate response

The group of 41 workers were trapped in the early hours of November 12, when one of the sections of the tunnel under construction in which they were working collapsed in the state of Uttarakhand, a mountainous region plagued by this type of construction and vulnerable due to its orography to landslides, landslides and other natural disasters.

Initially, authorities estimated that around thirty people had been trapped behind a thick wall of rubble about 60 meters thick, but they later updated that figure to 41 workers.

The rescue work began on the same day of the collapse, when members of the National Disaster Management Force (NDRF) moved to the area and tried, unsuccessfully, to remove the debris manually and with the help of excavators and other vehicles. of construction.

At the same time, the rescuers managed to establish contact with the trapped workers using walkie-talkies and began to supply them with oxygen and food through a narrow pipe that had survived the collapse and connected both cavities.

False expectations

Small landslides and little progress during the first hours of the rescue led the authorities to require the presence of a first tunnel boring machine, which they would use to excavate a hole through which they would insert a series of pipes almost a meter in diameter that would once reach the the workers allowed their escape.

Already then, hopes of a quick rescue predominated among the teams, with recurring messages that predicted success in the next few hours, but that never arrived.

This optimism encountered its first obstacle on November 15, when the slow progress of the tunnel boring machine led the rescuers to request the sending of a new, more powerful machine, which was transferred from New Delhi by the Armed Forces.

Alternative plans

The rapid progress of the new machine during its first days, when it managed to pierce almost half of the layer of rubble, raised again the hopes of the authorities to conclude the rescue within a week, but since then the Setbacks became common and progress insufficient.

A problem in the tunnel boring machine on November 18 temporarily paralyzed work and led operators to draw up a list of five alternative plans in case the original idea of ​​drilling through the rubble wall failed.

Excavating a vertical tunnel to the cavity in which the workers are trapped, or drilling through the opposite end of the tunnel, crossing a wall more than 400 meters thick, were some of the ideas that were already underway.

In this context, on November 21, the authorities shared the first video of the workers since the day of the collapse, thanks to a small camera that they introduced through a pipe that they had previously installed to send hot food and other belongings to the workers.

In it, the rescue teams asked them about their state of health and asked them to go one by one before the camera, where they were seen equipped with their helmets and disheveled in a tunnel illuminated by powerful spotlights.

Manual excavation

Drilling continued in the following days in small steps, at a rate of about 2 or 3 meters per hour, which was often interrupted by new adversities, which ended up leading to a breakdown of the second TBM last Friday, and the Yesterday I began manual excavation using what is known as “mousetrap miners””, when there were still more than ten meters of rubble to remove.

This technique, used for coal exploitation in some regions of India and considered dangerous by some environmental organizations that point out the risk of sending people through the small tunnels, was carried out by three teams of six people who took turns inside the narrow cavity to advance steadily.

The lack of major obstacles in the excavation allowed the miners to advance at a pace that until now had been difficult to achieve regularly with the machines, and 17 days after the collapse, the escape route through which they They would end more than two weeks of isolation.