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Uttarkashi tunnel collapse: From rat-hole mining to vertical drilling, methods used to rescue 41 workers

Rescue workers drilled through the 60-metre stretch of rubble of the collapsed Silkyara tunnel in which 41 workers were trapped for the last 16 days, officials said.

Shashwat Bhandari Edited By: Shashwat Bhandari @ShashBhandari New Delhi Updated on: November 28, 2023 17:43 IST
Ambulances on standby during the ongoing rescue operation
Image Source : PTI Ambulances on standby during the ongoing rescue operation of the 41 workers trapped inside the under-construction Silkyara Bend-Barkot Tunnel, in Uttarkashi district

Uttarkashi Tunnel Collapse: India's biggest evacuation operation to rescue 41 trapped workers inside the Silkyara tunnel in Uttarakhand, who have been stuck for the last 16 days, is in the final stage and the evacuation of the stranded labourers is expected to begin very soon. The multi-agency rescue operation was conducted with the efforts of various government teams and there was hardly any department left that was not involved in this mission. The workers were trapped inside the under-construction tunnel being constructed under the ambitious Chardham project when it collapsed after a landslide on November 12. 

Rescue workers on Tuesday drilled through the 60-metre stretch of rubble of the collapsed Silkyara tunnel in which 41 workers are trapped for the last 16 days, officials said. State government's information department chief Bansi Dhar Tiwari told reporters a little after 1.30 pm that the drilling was over. Less than an hour later, Uttarakhand Chief Minister Pushkar Singh Dhami said the process of laying the escape pipe into the drilled passage was complete. “Soon all brother workers will be brought out,” he posted on social media.

Let's take a look at how the country's one of the biggest rescue operations was conducted.

Horizontal drilling approach to reach trapped labourers 

Horizontal drilling using the American auger machine was conducted to reach the trapped workers inside the Silkyara tunnel. This was one of the most trusted approaches to reach the workers. However, agencies faced a lot of hurdles, and technical snags sometimes with the machine or the topography of the region to create an escape passage.

The objective of this drilling was to create an escape route by pushing pipes into the dug-up area for the labourers. It took almost 17 days for agencies to drill a nearly 60-meter tunnel to reach the trapped labourers while facing several challenges. 

Manual drilling using rat miners 

When the American auger machine broke down after its blade or cutters got stuck in the debris-rock, around 10 meters of drilling were still left, and the rescue operation was put on hold again. However, the agencies then resorted to manually digging the remaining portion to push pipes inside and create an escape route for workers. To dig up the remaining portion manually, rat-hole mining by rat miners was initiated and in almost 24 hours, they were able to dig up the remaining part. Efforts to create escape tunnel is in final stage and the evacuation of the trapped labourers may start any time now.      

Vertical drilling from atop tunnel

Since, the American auger machine faced continuous technical glitches and finally broke down when it had drilled up to 56 meters, an alternative way to reach the trapped labourers was to create a vertical escape tunnel from atop the mountain. A total of 80 meters had to be dug up. 

The procedure is still underway and agencies have completed around 45 meters of drilling. Under this method, two tunnels -- one of 1.2 meters and the other of 0.80 meters are planned. Though the agencies have achieved the breakthrough in horizontal digging, efforts to prepare a vertical tunnel are still underway in order to have a safe side option if any last-minute hurdles are faced during evacuation. 

6 and 4 inches pipes to establish communication

Agencies already installed 6 and 4-inch pipes days ago and established communication channels with the trapped workers. Food, water, medicines, and other facilities were being provided to them using these small tunnels. 

Workers provided with food, medicines 

Rescue teams took full care of trapped workers inside the Silkyara tunnel as they were continuously provided with fresh food, medicines, board games to divert their minds. Labourers were also able to speak to their families to assure them that they were safe. A landline facility was also provided at the collapse site in just 12 hours. 

Temporary hospital set up at collapse site

A temporary arrangement of 5-10 beds is also ready at the collapsed tunnel site for any sort of emergency and to monitor the health of workers when they come out of the tunnel. 

Ambulances, and beds are ready in hospital 30-km away

A green corridor is prepared and all preparations are been done in a hospital where 41 beds are ready to monitor the health of trapped workers where they will be kept for 48-72 hours after they are evacuated to make sure they are physically and mentally well.  

ALSO READ | Uttarkashi tunnel collapse: How events unfolded | Timeline

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