Rishikesh-Karanprayag rail tunnel boring work second fastest in world: Rail Vikas Nigam CMD

New Delhi: The upcoming 125-km Rishikesh-Karanprayag rail line in Uttarakhand has achieved remarkable progress in tunnel boring work, making it one of the fastest in the world, Rail Vikas Nigam Ltd (RVNL) Chairman and Managing Director Pradeep Gaur said.

Gaur told PTI on Tuesday that the 9.69-metre diameter Cabrera tunnel in Spain was built by a Double Shield tunnel boring machine (TBM) at an average rate of 423 metres per month while the 14.58-km tunnel between Devprayag and Janasu has just been completed by Single Shield TBM at an average rate of 413 metres per month, becoming the second fastest in the world.

When commissioned, the tunnel will become the longest transportation tunnel in the country, the RVNL CMD said.

"Out of 14.58 km, 10.47 km was built using a special tunnel boring machine from Germany and the rest was constructed using the conventional drill and blast method," he said.

Providing an update on one of the country's iconic mountain rail projects, the CMD highlighted several unique features and experiments in tunnel construction that RVNL has undertaken with meticulous planning and risk assessment.

"As the Himalayas are the most challenging geology, it makes the whole project extremely demanding and interesting. Out of a total of 125 km, 105 km pass through the tunnels. Around three km are covered through bridges and four km by Adits and cross passages; the left portion is just 12 to 13 km which consists of 12 station yards," Gaur said.

He said this is the first time that a TBM is being used for a rail project in the mountains. Other rail tunnels in the mountains were built or are under construction using the conventional drill and blast method.

"Even for non-railway projects such as hydroelectricity projects, TBM has been used in the Himalayas but they had a small diameter of around five metres. So, TBM being used in the Rishikesh-Karanprayag rail line has a diameter of 9.1 metres," he said.

Citing the benefits of experimenting with the TBM in the Himalayas, Gaur said the conventional drill and blast method is very slow as it can bore only 60 to 90 metres in a month.

"However, the use of TBM required immense risk assessment, thorough investigation and various other precautions because organisations have tried to put TBMs in the Himalayas in the past and there have been more failures than successes," Gaur said.

"So we ventured into this unknown territory for railways and decided to deploy this tunnel boring machine for the first time on Indian Railways in the mountainous region," he added.

A detailed estimate was sanctioned in 2016 and the first work of the project was awarded four years later in 2020 after complete land and forest clearance, according to RVNL.

"Almost 92 per cent of the tunnel construction work of the whole project has been completed," Gaur said.

"Total tunnel length is 213 km which includes escape tunnels also and out of these, 195 km tunnelling has been completed in just three years and nine months," he added.

Gaur mentioned the use of best international standards such as adhering to the National Fire Protection Association guidelines and environmental sustainability norms.

"We even planned the dumping of excavated muck in advance and lands were acquired accordingly. Those areas were also selected to be least vulnerable from an environmental point of view," Gaur said.

"As of now, we are planning by December 2026 to commission the complete project," he added.