The two Herrenknect tunnel boring machines (TBM) that will bore the 16 km (10 mile) Chiltern tunnel will be assisted by robotic arms that are designed to improve safety and efficiency.

The Chiltern tunnel is part of the larger HS2 project in London, England, a high-speed rail project that will link London to the Midlands, the North and Scotland serving more than 25 station and connecting about 30 million people. The project will be completed in three phases. The Chiltern tunnel is one of the two phase one tunnels that will have 51 km (32 miles) off tunnels.

The two 170 m- (557-ft) long, 2 kt (2,200 st) TBMs – nicknamed Cecilia and Florence – were revealed in August. Beginning at a site near the M25, they will dig as deep as 90 m (300 ft) below the Chilterns, boring through 16 m (52 ft) of chalk and flint every day and lining the tunnels with a concrete ring.

Florence will begin work in early 2021, with Cecilia following soon after on the other half of the tunnel. They are expected to operate almost non-stop for three years to excavate the 16 km (10 mile) Chiltern Tunnel.

An onboard robot called Krokodyl was developed by Align: the joint venture team made up of Bouygues, Sir Robert McAlpine and VolkerFitzpatrick.

The robot works in a similar manner to robotic arms used on factory production lines, carrying out basic repetitive tasks: removing wooden spacers between tunnel segments and inserting connection dowels. Each of the 112,000 tunnel segments weighs up to 8 t (8.8 st) and they are delivered to the TBM with wooden spacers between them, which are typically removed by hand. The robot then places the dowels into position, in preparation for slotting the segment into place.

Automating these processes will reduce the need for humans to work in this potentially hazardous environment.

“Safety is a key priority for HS2 and the introduction of these innovations that essentially remove personnel from harm’s way is an excellent example of the sort of initiatives we are pleased to see implemented on the project,” said Eddie Woods, head of tunnelling at HS2 Ltd. “It is one of the ways that ‘safe at heart’ can be achieved by minimizing exposure in high-risk locations.”

Didier Jacques, underground construction director for Align, said: “A lot of work has been undertaken by all concerned that has enabled us to develop and introduce this robot, thereby reducing the risk to our personnel operating in our state of the art TBMs. We are very proud of these innovations, which we would be happy to share with tunnelling teams working on other projects across the world, to help reduce the likelihood of accidents and injuries.”

HS2 will connect London to Manchester and Leeds via Birmingham with a Y-shaped railway network. Trains will be able to travel at up to 360 km/h on the tracks. It is hoped that building the high-speed rail will boost capacity while causing minimal disruption to existing services, and eventually help rebalance the south-east-centric UK economy.

Following years of planning, disagreement, and reviews, the government gave HS2 the green light in February. Construction has started on the London-Birmingham segment with initial focus on major engineering challenges, such as tunneling.

HS2 has been criticized for its potential environmental disruption and its budget, which has ballooned from an estimated £30.9-£36 billion in 2010 to as high as £106 billion according to a 2019 review, which also warned that it could be delivered up to five years behind schedule. Anti-HS2 groups have also argued that the shift to remote working – triggered by the coronavirus pandemic – has raised further questions about the necessity of the project.