Uttarkashi (Uttarakhand): A team of rat-hole miners have begun manual drilling horizontally through the rubble to rescue the 41 workers trapped in the under-construction Silkyara tunnel after a portion of it collapsed on November 12.
Vertical and manual horizontal drilling are the two methods on which rescue efforts are being focused at the moment. Work on the other options, such as horizontal drilling from the Barkot end of the tunnel is also underway.
Officials and experts engaged in the Silkyara tunnel rescue operations have put into action multiple plans to save the 41 workers who have been trapped for the last 16 days. Vertical drilling resumed on the second day today and it was completed upto 31 metres out of the total 88 metres when reports last came in.
A total of 86 metres have to be drilled vertically to prepare an escape passage. Pipes of 1.2 metres in diameter have to be laid vertically through the top of the tunnel on which work began on Sunday as a second option to reach the stranded labourers.
During the press conference about the rescue operations, Lt Gen (retd) Syed Ata Hasnain of the National Disaster Management Authority mentioned on Monday evening that the final 15 meters of horizontal drilling seemed challenging due to the discovery of a high concentration of lattice bars and concrete, complicating the operation.
If a new auger machine becomes available, the evacuation operation may still opt to continue using the manual drilling method to avoid potential delays caused by another breakdown and the time-consuming process of cutting and pulling out debris. Hasnain did not specify a deadline due to uncertainty about future challenges involving more iron and cement in the debris.
Lt Gen Harpal Singh (retd), former engineer-in-chief of the Army, informed reporters in Silkyara that vertical drilling has been done up to 31 metres. Singh, who has also headed the Border Roads Organisation, is involved in the rescue operation. The 200-mm diameter pipes, which were inserted vertically earlier to learn about the soil strata and find out whether there are any obstacles on the way, have reached up to 70 metres, he said, adding preparations are also underway to start horizontal drilling inside the main tunnel manually.
"Frames of 800-mm diameter pipes have been prepared. We will move ahead by half a metre to one metre gradually. If all goes well and no obstacles are encountered a 10-metre stretch can be covered in 24-36 hours," he said.
The six-member team of rat-hole miners have started manual drilling which is a slow and difficult process in which they will go one after another through the 800-mm diametre pipes laid through the rubble and remove the debris with the help of shovels to insert more pipes. When asked whether going through the 800-mm diameter pipes would be difficult for them, a team member said they have experience in manually clearing debris through even 600-mm diameter pipes.
The rat-hole miners will go inside the pipes wearing a helmet, a uniform, a mask and glasses. Though a time-consuming process, manual drilling seems a feasible option as only around 10-12 metres through the rubble remain to be drilled to complete the escape passage. When asked which of these two options is likely to be completed first, Singh said it is difficult to predict as everything depends on whether or not any hurdle is encountered.
Manual drilling was resorted to as the auger drill -- a corkscrew-like device with a rotary blade at the front end -- which had drilled up to around 46.8 metres had to be withdrawn as it hit several hurdles on the way and finally got entangled in a girder in the debris. Auger blades have been removed from the rubble with the help of a plasma cutter flown in from Hyderabad. Now 1.5 metres of damaged pipe is being removed, Lt Gen Singh said, adding manual drilling will be done by experienced workers with the help of the Army.
Meanwhile, the PM's Principal Secretary PK Mishra, Home Secretary Ajay K Bhalla and Uttarakhand Chief Secretary S S Sandhu arrived in Silkyara to take stock of the ongoing rescue operations. Mishra spoke to the trapped workers and asked them to be patient as multiple agencies were working hard to evacuate them safely as early as possible. He also sought to know about their well-being. Gabbar Singh Negi talked to the PMO official on behalf of the trapped workers through a communication system set up in a part of the tunnel.
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