Rat-hole mining experts begin manual drilling through tunnel debris, vertical boring makes headway

PTI, Nov 28, 2023, 9:00 AM IST

Uttarkashi/New Delhi: Rat-hole mining experts called in to help rescue 41 workers trapped inside the collapsed Silkyara tunnel began manual drilling Monday through the rubble.

Simultaneously, vertical drilling from above the tunnel has reached a depth of 36 metres out of the 86 metres needed.

Twelve rat-hole mining experts will be involved in manual drilling and excavation horizontally through the last 10- or 12-metre stretch of debris of the collapsed portion of the under-construction tunnel on Uttarakhand’s Char Dham route.

This drilling was earlier being carried out by a huge auger machine that got stuck in the rubble on Friday, forcing officials to focus on an alternative option — drilling down from above the tunnel. About 40 per cent of the 86-metre vertical drilling required is now done.

For the horizontal through-the-rubble option, officials decided that the final stretch would be handled through a manual approach in which individual workers will go into the escape passage with drills, as well as gas-cutters to tackle obstacles like iron girders.

By Monday evening, the last bit of the stuck auger had been cut out piece by piece and a steel pipe inserted further into the partially complete escape passage.

In Delhi, National Disaster Management Authority (NDMA) member Lt Gen (retd) Syed Ata Hasnain said vertical drilling, which began Sunday, has already reached a depth of 36 metres.

Rescuers hope to pull out workers through this one-metre-wide shaft when it breaks through the top of the tunnel below, hopefully by Thursday.

Another eight-inch wide shaft being drilled from a nearby point has reached about 75 metres down.

This probe, which is also expected to act as a supply line for the trapped workers, has indicated that there were no serious geological obstacles for the main shaft up to this point, the NDMA member and officials at Silkyara said.

The vertical drilling, however, encountered some water underground and “dewatering” was carried out, officials said. But it didn’t seriously affect the operation.

Two teams of seven and five men who are experts in the technique of rat-hole mining were called in by two private companies involved in the rescue operation.

Rat-hole mining is a controversial and hazardous procedure in which miners in small groups go down narrow burrows to excavate small quantities of coal.

Uttarakhand government’s nodal officer Neeraj Khairwal made it clear that the men brought to the site were not rat-hole miners but people who are experts in the technique.

They are likely to be divided into teams of two or three. Each team will go into the steel chute laid into the escape passage for brief periods.

Rajput Rai, a rat-hole drilling expert, said one man will do the drilling, another collect the rubble with his hands and the third place it on a trolley to be pulled out.

Principal Secretary to Prime Minister P K Mishra, Home Secretary Ajay Bhalla and Uttarakhand Chief Secretary S S Sandhu came to Silkyara Monday to take stock of the operation.

Mishra spoke to the trapped workers, assuring them that multiple agencies were at work to evacuate them and they should remain patient. Gabbar Singh Negi talked to the official through the communication link on behalf of other workers inside the tunnel.

They are in a two-kilometre built-up stretch of the tunnel and are being supplied food, medicines and other essentials through a six-inch pipeline. “They are in very good health,” Hasnain said.

He said it was difficult to give a timeline for the manual operation at this stage.

The NDMA member said a yellow alert has been issued by the meteorological department indicating light rains in the next 24 to 48 hours. “But there is no possibility that work will be hindered because of this,” he added.

He said Mishra has directed officials to ensure all medical facilities for the trapped workers as “difficulties could increase with the passage of time”.