Uttarkashi tunnel collapse | Drilling snags hold up rescue operation in Silkyara tunnel

Rescue teams spend November 24 fixing snags in the drilling machine, strengthening its platform, and using radar to scan the debris ahead in Silkyara tunnel; mock rescue drill conducted by NDRF

November 24, 2023 10:36 pm | Updated November 25, 2023 06:58 am IST - SILKYARA

There are only 10 metres of debris left between rescuers drilling in from the Silkyara end and the trapped workers, but officials say it is difficult to anticipate when this last leg of the operation will be completed.

There are only 10 metres of debris left between rescuers drilling in from the Silkyara end and the trapped workers, but officials say it is difficult to anticipate when this last leg of the operation will be completed. | Photo Credit: Shashi Shekhar Kashyap

Rescue teams were not able to move even an inch closer to the 41 workers trapped in the collapsed Silkyara tunnel by November 24 evening, as the entire day was taken up in fixing snags in the drilling machine and using radar to scan the debris ahead for any further obstacles. There are only 10 metres of debris left between rescuers drilling in from the Silkyara end and the trapped workers, but officials say it is difficult to anticipate when this last leg of the operation will be completed.

Some progress has been made on alternative rescue efforts by boring vertically into the tunnel, as well as drilling efforts being made from the other Barkot end.

First visuals of trapped workers 

Chief Minister Pushkar Singh Dhami visited the tunnel site on November 24 afternoon and also briefed Prime Minister Narendra Modi about the rescue operation, which is now in its 13th day.

Strengthening auger platform

The basic plan is to bore a hole in the debris and push in wide pipes which are welded together, through which the workers can be brought back out. A senior official involved in the Silkyara-end operation recapped the progress so far: the auger drilling machine started work in the early hours of November 22 but had to stop that evening as it struck an iron lattice girder, one of the structural elements of the tunnel. Gas cutters removed this hurdle overnight.

On November 22, the machine pushed a ninth pipe in for just 1.8 metres, before vibrations were noticed and drilling was halted again at the 48-metre mark. Late on November 23 night, it was found that a bent part of the forepole from the tunnel lining was stuck in the auger assembly, leading to the vibrations. The teams then worked to strengthen the auger machine’s platform using an accelerating agent for the rapid hardening of concrete.

“By November 24 morning, the platform for the auger machine was strengthened by way of anchoring, bolting, concreting foundation, etc. But work couldn’t resume as the auger was needed to further pull back fully to assess any other damage to the pipe,” the official said.

Radar shows no obstacles

The rescue teams also used ground penetration radar to scan for any further obstacles lying ahead, said senior Uttarakhand government official Bhasker Khulbe, a former advisor to the PM, adding that the scan showed that there are no major hurdles like rocks or iron objects in the next five metres of debris.

By 2:30 p.m., augur re-assembly work was completed and the machine was reinserted in the pipes to push them further. However, before the placing and positioning of the next pipe, the auger again developed a snag. Till 9 p.m., drilling had not restarted.

He never told us his work was dangerous: Brother of trapped Uttarkashi tunnel victim

Rescue drills and preparation

On November 24, the trapped workers were given roti, dal, mixed vegetables and fruits, as well as medicines, all pushed through a narrower pipe of just 150 mm diameter. A modified wire communication system was used to talk to the workers and give them a medical consultation.

In a mock rescue drill at the site, a jawan from the National Disaster Relief Force was sent inside the escape passage, pushing a wheeled stretcher tied to a rope and was later pulled back. He informed the rescue teams of the oxygen status inside the tunnel.

Forty-one ambulances are stationed outside the tunnel to rush workers after evacuation to the Chinyalisaur community health centre, where a separate ward has been set up with 41 oxygen-supported beds for them.

Alternative rescue routes

While there was no progress in horizontal drilling, a drilling point has been finalised for the vertical drilling efforts at Silkyara, and the drilling machine has been assembled. This vertical drilling is expected to be completed by November 26.

At the Barkot end, the horizontal drilling managed to make a drift of 9.10 metres after four blasts. Shotcreting and rib erection has been completed and additional rib fabrication work is in progress at this site. The platform for perpendicular-horizontal drilling was completed on Friday, and equipments will be set up for further work on Saturday morning.

On November 12, a collapse occurred in the under-construction tunnel from Silkyara to Barkot, with debris falling in a 60-metre stretch on the Silkyara side. The workers are trapped within a space measuring 8.5 metres in height and two kilometres in length which lies in the built-up portion of the tunnel, meaning that they have access to electricity and water supply.

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