A week after the Silkyara tunnel collapse in Uttarkashi, in a big breakthrough in rescuing 41 trapped workmen in the tunnel, a six-inch diameter 53 metre-long pipe was inserted into the tunnel. Director, National Highways and Infrastructure Development Corporation Limited (NHIDCL), Anshu Manish Khalkho, told journalists that “this would help the trapped workers get better food, more air and anything else they require.” On Tuesday morning an endoscopic camera was sent in through the opening and the first visuals of the workmen was beamed to the world.  This is no mean feat. A previous attempt to speed up the rescue ran into a fresh mud collapse. The first 4 inch pipe inserted horizontally through the collapse, helped keep the workers safe by supplying them with air and dry fruits etc for nourishment. With the lateral insertion of the six-inch diameter pipe using trenchless tunnelling technology, they would be able to get more wholesome food than before. Khichidi, packed in water bottles, was supplied on Monday, November 20, 2023, to the trapped workmen for the first big meals since the collapse.  “Two DRDO robots of 20 and 50 kg have also been deployed to crawl on the ground and enter the tunnel. However the loose sand has cast doubts on the success of this operation,” said Khalkho of NHIDCL. The site has been prepared for tunnelling equipment, which is on its way by road from Indore. The machines are expected in a day or two. “The Border Roads Organisation (BRO), in the meantime, has made roads from the Silkyara and Barkot ends to facilitate the machines to reach the site,” said Khalkho, who is the official spokesperson for the entire operation. The operations had to be discontinued for a couple of days when there was a minor fresh collapse and when the American Augur machine, sourced from Delhi stopped working. Replacement machines are travelling by road from Indore as they can’t be airlifted because of the weight. A 22-metre, 900 mm pipe is now being installed. That should help in rescuing the trapped workers. The first success came through micro-tunneling using trenchless technology. So what is microtunneling. Aaroh Swarup, Head International, Indian Society for Trenchless Technology (IndSTT) said “Microtunneling is basically a smaller and modernised version of the tunnel boring process, where a micro tunnel boring machine (MTBM) is used. It is controlled remotely and normally guided by precision lasers. The advantages (if done right) include minimal disturbance to the existing features and efficient and safer installation of buried utilities.”The Silkyara tunnel in the Uttarkashi district of Uttarakhand is part of the Centre’s ambitious chardham all-weather route that would reduce distance between Yamunotri and Dharasu by 20 km and travel time by about an hour. This double-lane tunnel of 4.5 km is one of the longest in this NH 134 project, which aims to connect the four shrines of Gangotri, Yamunotri, Badrinath and Kedarnath. A portion of the under-construction tunnel between Silkyara and Dandalgaon on the Brahmakhal-Yamunotri national highway collapsed on Sunday morning on November 12, trapping 41 workmen behind the collapse. Efforts have since been on to rescue them, with major national agencies such as the National and state disaster response forces, the Prime Minister’s Office and the Border Roads Organisation working together in the operation. E Jayashree Kurup is senior editor Construction World & Director Wordmeister Editorial Services