JANASU: The completion of India’s longest rail tunnel between Devprayag and Janasu in Uttarakhand faced significant challenges, including moments when it seemed the tunnel might collapse and jeopardise the whole project, Larsen & Toubro Limited (L&T) said on Saturday.”The tunnel boring machine (TBM) named ‘Shakti’ was about five km inside the tunnel when it encountered a gush of water from all directions at the rate of around 1,500 litres per minute,” Rakesh Arora, Project Director of the tunnel, told PTI.”Besides the TBM operator, there were 200 people inside the tunnel at that time. It was one of the toughest moments when the tunnel was at risk of flooding or collapsing. However, we took corrective measures immediately,” he said.Arora said the situation did not improve for around a month.His team struggled to overcome it by using a combination of chemical as well as cement grouting to stabilise the rings and surrounding rock, consequent to which, the water flow started reducing and the engineers could stabilise the interiors successfully, he added.”Besides, there were occasions when huge pressure from the surrounding soft rock posed a serious risk to the tunnel’s progress, which was successfully handled by speeding up the excavation works with a combination of lubricating the TBM shield using bentonite,” Arora added.
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