After a brief glimmer of hope in the rescue of 41 labourers stuck inside the collapsed Silkyara tunnel in Uttarkashi district of Uttarakhand, the operation witnessed a setback again as the blades of the auger machine drilling through the tunnel broke.
Officials have been now forced to consider other options that could drag on the rescue of the trapped workers by several days – even weeks.
While more options are being continuously explored, let us look at what this drilling machine is and how it was planned to be used to rescue the workers.
What is an auger drilling machine?
An auger drilling machine is a drilling tool used for making holes in the ground. It typically consists of a rotating vertical metal rod or pipe with one or more blades attached at the lower end that cut or scrape the soil. In this case, however, it was a horizontal drilling machine, also known as a boring machine or directional drill.
It is used to install underground pipelines, cables and service conduits through trenchless methods. It used a specialised tool – a giant corkscrew-like device with a cutter at its end called an auger – attached to a central shaft or drill, which penetrates the chosen bore path by rotating through it. The machine works in three stages: drilling a pilot hole using the auger, pre-reaming it to enlarge its size, and pullback of the pipe.
What happened with the drilling machine in Silkyara?
American-made high-performance auger machine was flown down from Indore to assist in the rescue efforts and steel pipes of 800- and 900-millimetre diameter were brought to the tunnel site. This was after the initial plan to remove the debris blocking the tunnel exit failed.
The machine, called “60-1200”, is substantial in size and power, designed for heavy-duty large-scale projects.
The drilling of 800 mm diameter pipes from the Silkyara end was put on hold for nearly a week when the auger machine encountered a hard obstacle around the 22-metre mark, creating vibrations in the tunnel that caused safety concerns.
When the rescue operation resumed again, the hopes were high. A team of 15 doctors, including chest specialists, has been deployed at the site in anticipation of the evacuation. Twelve ambulances were on standby at the spot, and the plan was to keep a fleet of 40 ready.
A helicopter was also expected to be earmarked for the operation. A special ward to accommodate all evacuated workers was readied at the community health centre in Chinyalisaur. Officials said that all hospitals in the district, as well as AIIMS, Rishikesh are on alert.
What happened then?
The 25-tonne drilling machine created a horizontal passage of 46.9 metres into the rubble, out of the estimated total length of 60 metres. However, the blades of the auger machine drilling through the rubble got stuck, hampering the rescue again.
Subsequently, a steel chute was pushed through in sections, up to this point where the rotary blades were stuck, followed by the long auger.
Uttarakhand CM Pushkar Singh Dhami told reporters that about 20 metres of the auger in the chute had been cut out. A plasma cutter is being airlifted from Hyderabad to tackle the remaining 25 metres.
The workers are in a built-up two-kilometre stretch of the tunnel. They are being sent food, medicines and other essentials through the six-inch wide pipe. Mobile phones have been sent in through this tube and a landline established, officials said. Board games like Ludo were also provided. An endoscopic camera has been used to get live visuals from beyond the collapsed stretch.
What next?
Fourteen days after the accident, the development has added to the anxiety of families of trapped workers, some of whom are camping near the site and talking to them occasionally through the communication system set up by the rescue workers.
However, officials have now shifted focus to two alternatives – manual drilling through the remaining 10 or 12-metre stretch of the rubble or, more likely, drilling down 86 metres from above using vertical drilling methods.
“This operation could take a long time,” National Disaster Management Authority (NDMA) member Lt Gen (retd) Syed Ata Hasnain said at his media briefing.
International tunnelling expert Arnold Dix repeated his promise of getting the workers out “by Christmas”, which is a month away.
Officials are also looking at other possible options for a quicker solution.
