India is stepping up efforts to build its domestic Tunnel Boring Machine (TBM) manufacturing capabilities as work advances on the 125-km Rishikesh-Karnaprayag railway line in Uttarakhand. The push comes amid China’s recent introduction of fresh global restrictions on TBMs, critical equipment used in metro rail, highway and other major infrastructure projects. Railway Minister Ashwini Vaishnaw said India, which previously depended on imported TBMs, is now manufacturing machines with diameters of 8 metres and 15 metres. The country is also preparing to produce machines exceeding 16 metres in diameter, strengthening domestic capabilities in a technology used for railway, highway and power infrastructure projects.
In separate social media posts on Thursday, Vaishnaw highlighted the engineering challenges involved in the Rishikesh-Karnaprayag railway project and the country's efforts to develop a complete domestic TBM ecosystem, from design and manufacturing to maintenance.
Rishikesh-Karnaprayag railway line: 83% of the route will pass through tunnels
The 125-km Rishikesh-Karnaprayag railway line is being built through difficult Himalayan terrain and is expected to improve connectivity to several parts of Uttarakhand.
Describing the project on X, Vaishnaw said, “Engineering through the Himalayas! 125 km, 12 stations, 83% tunnels. The Rishikesh-Karnaprayag rail line is not just a track, it's Uttarakhand's lifeline to the future.”
The project includes 16 tunnels and 19 bridges, with around 104 km of the alignment passing through tunnels. The minister described the route as a demanding engineering undertaking shaped by the region's geological conditions.
“Rishikesh to Karnaprayag is a very important railway project in Uttarakhand. This project has been designed amidst the complex geology of the Himalayas. In this 125-kilometre project, practically 83% consists of tunnels, which means approximately 104 kilometres of tunnels are being constructed. There are 16 tunnels and 19 bridges. If you look at it practically, this project is basically tunnel, bridge, tunnel, bridge, that is the nature of this project,” he said in a video post.
Why building tunnels in the Himalayas is difficult
One of the major challenges is the geology of the Young Fold Mountains, where sections of the terrain contain softer material rather than solid granite. Under pressure, the surrounding ground can squeeze inwards after a tunnel is bored, complicating construction.
Vaishnaw said engineers carried out extensive investigations before deciding to use TBMs on the project. The machines were then modified to handle the conditions.
“When the decision to use a Tunnel Boring Machine (TBM) was taken for this Karnaprayag project, extensive investigations were carried out beforehand. If a tunnel is bored through solid rock strata, it does not squeeze. However, in soft strata, the tunnel has a tendency to squeeze inward. By modelling this squeezing tendency, modifications were engineered into the Tunnel Boring Machine,” he said.
The changes included modifications to the cutter head and the shield that houses the segmental lining assembly. Engineers also made changes to the drive system to provide additional torque and thrust.
“Numerous modifications were made to the cutter head. Following that, significant modifications were also made to the shield where the segmental lining plate assembly is housed. A special design was implemented in its drive system to deliver extra torque and extra thrust. Due to this specialised design, the Tunnel Boring Machine has proven successful in the Rishikesh–Karnaprayag project,” the minister added.
Rishikesh-Karnaprayag railway project: Latest work status
Vaishnaw said construction has reached an advanced stage across most sections, with tunnels T-1 and T-5 among the key stretches where work continues.
Tunnel T-1, which is 11 km long, is particularly challenging because of the difficult geology and the presence of human settlements along the stretch. Micropiles are being used to stabilise the area, he said.
“Tunnel 1 is the most complex section. It spans 11 kilometres. It is the most complex because the geology here is the most difficult. Several tunnels ahead have already been completed. There is also considerable human habitation in this stretch, so micropiles are being utilised to stabilise the area. Overall, the progress on this project is very good... Work on T-5 and T-1 is also progressing at a rapid pace,” he said.
The stations listed along the route include Shivpuri, Byasi, Devprayag, Janasu, Maletha, Srinagar, Dhari Devi, Tilani, Gholtir, Gauchar and Karnaprayag.
How the railway line could improve access to Uttarakhand's pilgrimage sites
Once completed, the railway line is expected to make journeys towards Karnaprayag and Rudraprayag easier and improve access to pilgrimage destinations such as Kedarnath and Badrinath.
The project also has strategic significance because Karnaprayag, its terminal station, is around 123 km from the India-China border, according to Vaishnaw.
The line is intended to strengthen connectivity in the hill state, where road journeys can be affected by mountainous terrain and challenging travel conditions.
India aims to manufacture TBMs larger than 16 metres
Alongside the railway project, the government is working to expand India's domestic capacity to manufacture the machines needed for major tunnelling projects.
Vaishnaw said TBMs are essential for the country's expanding infrastructure programme, which includes railways, highways and power projects. India previously relied on imports, but domestic manufacturing has progressed to machines with 8-metre and 15-metre diameters.
“With the vast amount of infrastructure currently being built across the country, whether for railways, highways, or power, these various infrastructure projects heavily rely on Tunnel Boring Machines (TBMs). There was a time when all tunnel boring machines had to be imported,” he said.
“But now, all 8-meter diameter tunnel boring machines are being manufactured in India. Moreover, even 15-meter tunnel boring machines have now started being made in India. There is a TBM plant in Tamil Nadu. And very soon, TBMs with a diameter exceeding 16 meters will also be manufactured in India. This means India is becoming self-reliant (Aatmanirbhar) in TBMs, right from design and manufacturing to maintenance,” the minister added.
He said the development of domestic manufacturing and technical expertise was part of the Aatmanirbhar Bharat vision.
“The country is also preparing to manufacture TBMs with diameters exceeding 16 metres,” Vaishnaw said in a separate post.
With larger machines planned for domestic production, India is seeking to build a more complete TBM ecosystem and reduce dependence on imported technology for major infrastructure projects.