Vertical drilling from top of the Silkyara tunnel where 41 workers have been trapped for the last 15 days progressed to 31 metres on Monday as a six-member team of rat miners arrived at the site to start manual drilling horizontally through the rubble lying in the collapsed part of the structure.
Vertical and manual drilling are the two methods on which rescue efforts are focused at the moment while work on the other options like horizonal drilling from Barkot end of the tunnel is also simultaneously underway.
Vertical drilling has been done up to 31 metres so far, former engineer-in-chief and DG Border Roads Organisation Lt Gen Harpal Singh told reporters in Silkyara.
A total of 86 metres have to be drilled vertically to prepare an escape passage to evacuate the trapped workers. Pipes of 1.2 metre diametre have to be laid vertically through the top of the tunnel by this method on which work began on Sunday as the second alternative option to reach the stranded labourers.
“The 200 mm diametre pipes which were inserted vertically earlier to learn about the soil strata and find out whether there are any obstacles on the way have also reached up to 70 metres”, Singh said.
“Preparations are also underway to start horizontal drilling inside the main tunnel manually,” he said.
“Frames of 800 mm dia 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 ten metre area can be covered in 24-36 hours,” he said.
A six- member team of rat miners also arrived at the site to start manual drilling which is a slow and difficult process in which they will go one after another through 800 mm diametre pipes already laid through the rubble and remove the debris with the help of shovels to insert more pipes.
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When asked whether going through 800 mm dia pipes would not be difficult for them, one of the team members said they had experience of manually clearing debris through even 600 mm diametre pipes. The rat 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, Lt Gen Singh said it is difficult to predict that as everything depends on whether or not any hurdles are encountered.
Manual drilling was resorted to as the auger machine 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.
“Manual drill will be done by skilled workers who have experience in the field with the help of the army,” Singh said.
Meanwhile, Principal Secretary to the PM, PK Mishra, Home Secretary Ajay K Bhalla and Uttarakhand Chief Secretary S S Sandhu have arrived in Silkyara to take stock of the ongong rescue operations.