India is accelerating the development of indigenous Tunnel Boring Machines (TBMs) as construction progresses on the 125-kilometre Rishikesh-Karnaprayag railway line in Uttarakhand.

The initiative comes amid fresh Chinese restrictions on TBM exports and reflects the country's broader push towards self-reliance in critical infrastructure technologies.

Railway Minister Ashwini Vaishnaw said India, which once depended entirely on imported TBMs, is now manufacturing machines with diameters of 8 metres and 15 metres. The country is also preparing to manufacture TBMs exceeding 16 metres in diameter, strengthening domestic capabilities for railway, highway and power infrastructure projects.

In separate posts on social media, Vaishnaw highlighted both the engineering complexity of the Rishikesh-Karnaprayag railway line and India's efforts to establish a complete domestic TBM ecosystem covering design, manufacturing, operation and maintenance.

The 125-kilometre railway line is being constructed through the challenging terrain of the Himalayas and is expected to significantly improve connectivity across Uttarakhand. The project includes 12 stations, 16 tunnels and 19 bridges, with approximately 104 kilometres, or 83 per cent of the alignment, passing through tunnels.

Describing the scale of the undertaking, 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 minister noted that the project has been designed around the complex geology of the Himalayas. He explained that, in practical terms, the route consists of a sequence of tunnels and bridges because of the demanding landscape. “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.

One of the biggest challenges stems from the geology of the Young Fold Mountains. Unlike hard granite formations, some sections contain softer strata that can squeeze inward after excavation, creating significant engineering difficulties and requiring specialised construction methods.

Vaishnaw said extensive geological investigations were conducted before the decision was taken to deploy TBMs on the project. Engineers then modified the machines to cope with the tunnel squeezing phenomenon. “When the decision to use a Tunnel Boring Machine (TBM) was taken for this Karnaprayag project, extensive investigations were carried out beforehand,” he said.

To address these challenges, major modifications were made to the cutter head, shield and drive system of the TBMs. Engineers introduced additional torque and thrust capabilities and redesigned key components associated with segmental lining installation. According to Vaishnaw, “Due to this specialised design, the Tunnel Boring Machine has proven successful in the Rishikesh–Karnaprayag project.”

Construction has reached an advanced stage across much of the route, although work continues on several critical sections. Tunnel T-1, stretching 11 kilometres, remains the most complex segment due to particularly difficult geological conditions and the presence of nearby human settlements.

Vaishnaw said micropiles are being used to stabilise the area around T-1. “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 project also carries strategic importance. Karnaprayag, the terminal station, is located around 123 kilometres from the India-China border, enhancing connectivity in a region where travel is often affected by mountainous terrain and challenging road conditions.

Alongside the railway project, India is expanding its domestic TBM manufacturing capabilities to support the country's rapidly growing infrastructure sector. TBMs are increasingly vital for railway corridors, metro systems, highways, hydroelectric developments and other large-scale underground construction works.

“There was a time when all tunnel boring machines had to be imported,” Vaishnaw 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.”

He added that the development of domestic manufacturing expertise and technological capabilities forms an important part of the Aatmanirbhar Bharat vision. With plans to produce larger and more advanced TBMs domestically, India is seeking to establish a fully integrated tunnelling ecosystem and reduce dependence on imported technologies for future infrastructure expansion.