More than 120 hours after the 40 construction workers got trapped inside an under construction tunnel in Uttarakhand’s Uttarkashi district, the Indian Air Force airlifted a specialised American drill system which is expected to safely rescue the workers.
In the wee hours of November 12 (Diwali), a landslide caused a section of tunnel to collapse and the debris blocked the entrance of the tunnel leading to the workers getting trapped inside. These workers belong to the states of Uttar Pradesh, West Bengal, Odisha, Uttarakhand and Himachal Pradesh. The 4.5 kilometres long tunnel was being constructed between Silkyara and Dandalgaon on the Brahmakal-Yamunotri national highway as part of the Char Dham project.
The primary purpose of the tunnel is to connect Yamunotri and Gangotri valley in Uttarakhand to facilitate travelling during pilgrim season. Once built, the tunnel passing beneath the Radi pass is to reduce the 25.6 kilometres long road journey to 4.5 kilometres through the tunnel.
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The location of the trapped workers is at a distance of about 200 metres from the mouth of the tunnel.
The plan to rescue the workers from the tunnel involves drilling a small but stable horizontal passage inside the tunnel to facilitate their safe exit. Meanwhile it is learnt that the trapped workers continue to be in good health with food and medicines being provided to them through a small duct.
“Machines are working well. They (trapped workers) were given food, they are talking. They are in good health. Five more pipes are being inserted today,” GL Nath, public relations officer of the Navayuga Engineering Company Limited (NECL) was quoted. The Hyderabad-based company has been provided the contract to construct the tunnel.
What’s special about the American Auger drill machine?
The drill machine that has been airlifted by the Indian Air Force is manufactured by a US-based heavy machinery company named American Augers. The machine drill deployed at the site uses the state of the art technology and can drill five to six metres through the debris in an hour – none of the machines deployed so far can match this rate of penetration.
The US-made drill has a digging segment of helical shape and is known to be better at digging through debris and has been used in such rescue operations before. The previous drill which was being used by the rescuers failed as the debris is composed of an inconsistent mixture of rocks of varying shapes and sizes.
The American Augers machine can narrow down the time window which is of immense importance in such rescue operations.
Explaining the challenges involved in the rescue operation, Anshu Manish Khalkho, director at the National Highways & Infrastructure Development Corporation Limited (NHIDCL) told the press that it takes 10-12 hours to drill 50 metres with this machine.
“The nature of the rock here is quite fragile, posing a significant challenge to the operation,” he said while underlining that the time duration of 10-12 hours is tentative as any fresh crumbling of the fragile rocks can impede the rescue operations.
Also as per Manoj Garnayak, a former project director at L&T and an expert in underground construction, the section that has collapsed is located around 200 metres from the mouth of the tunnel.
“It could have happened due to a loose patch (of rock), which wasn’t visible during the construction. The patch might have consisted of fractured or fragile rock, that is, rock with a lot of joints that may have made it weak,” he was quoted.
“Another reason could be the seepage of water through a loose patch. Water erodes loose rock particles over time, creating a void on the top of the tunnel, which can’t be seen. However, these are only general principles, and we must wait for the results of a comprehensive investigation in this case,” he added.
Meanwhile, VK Singh, Union Minister of State for Road Transport & Highways informed the press yesterday, on November 16 that rescue operations could stretch on for another two-three days.
