The American-made “horizontal dry drilling equipment with an auger” had to stop since, beyond a point, it started getting lifted off the ground when it tried to drill further. At the time of filing the report, rescuers were anchoring the machine to the platform to prevent this from happening.
By the time the machine stopped working, four six-metre pipes had already been inserted and a fifth was being put in place. The workers are expected to come out through these pipes once drilling through the 50-plus metres of rubble is complete.
Earlier in the day, National Highways and Infrastructure Development Corporation Limited Director Anshu Manish Khalkho said they had called for another high-capacity drilling machine from Indore as a backup.
“We are around 24 metres inside, which I think is very good. We are trying to reach the other side as soon as possible. For the redundancy of the machine already working, another machine is being airlifted from Indore and will reach here by Saturday morning. If the current machine stops, we can use that machine to finish the job,” said Khalkho in the afternoon.
Asked about the pace of the operation – the machine is drilling around 1 metre per hour – he said they want to be extra cautious and ensure that the pipes are not misaligned by even a centimetre. Khalkho said that, as per their estimate, after digging for around 35 metres more they will get a breakthrough.
“The pipes are six metres in length. We align the pipes on the machine and push. The auger drills the debris and pushes the muck backwards. This process does not take much time. However, the process of aligning the pipes and welding them is much more complicated. We do not want the pipes to be misaligned even by one centimetre. This is why the rate is slow, but with workers getting more experience, the rate will increase,” he said, adding that to ensure speed they have deployed four-five welders to work simultaneously.
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He mentioned that another important thing to keep in mind is that the machine runs on diesel, and it is working in an enclosed area. Therefore, continuous ventilation using the compressor is a must.
“Ideally diesel machines should not work in such a closed space but we do not have any other option. A vibration is created because of the machine’s working and continuous ventilation. There is a possibility of that vibration affecting the equilibrium already created inside the tunnel. This is why we want to work at an optimum speed and not be in a hurry,” he said.
On Thursday night, the NDRF conducted a mock drill to assess how they will rescue the workers once the drilling process is complete. The previous plan was to create a small but stable passage for the men to crawl through, but now they plan to use stretchers connected with ropes, with wheels on it. Once the pipes are through, the workers would climb on the stretchers and will be pulled to the other side using the ropes.
© The Indian Express Pvt Ltd
First published on: 17-11-2023 at 6:21 PM IST
