Tunneling on the U.K.’s 230-km London-Birmingham high-speed railroad launched May 13, as a 10.26-meter-dia tunnel boring machine (TBM) began work at the Chiltern Hills southern approach, about 30 kilometers northwest of England's capital.

“The start of HS2 project tunneling is a moment of genuine excitement for everyone involved,” stated Mark Thurston, CEO of HS2 Ltd., owner of the $17-billion project. Various project contractors will deploy 10 TBMs to bore the line’s 103 km of tunnels.

The first machine will excavate one of the 16-km tunnels over the next three years. A second machine will follow in a few weeks to drive the twin parallel tunnel. Supplied by Herrenknecht A.G., the variable density slurry machines are designed to deal with the region’s mixture of soft chalk and hard flint.

The two TBMS also incorporate novel robotic arms to ease lining segment erection and use a semi-continuous boring technique. These features “have never before been introduced on any previous TBMs, worldwide,” according to Daniel Altier, project director of the Align joint venture of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick.