240321_TBM Cecilia breakthrough at Chiltern Tunnel North Portal_DJI_0060

UK: On March 21, tunnel boring machine Cecilia broke through the north portal of the Chiltern Tunnel on High Speed 2, the truncated high speed line which will link London with Birmingham and a junction with the West Coast Main Line at Handsacre.

The breakthrough marks completion of the main excavation work on the 16 km twin-bore tunnel, the longest on the 190 km route. It follows the completion of the first bore by TBM Florence on February 27; excavation of the tunnels began in June 2021.

240321_HS2_Chiltern tunnel TBM Cecilia Breakthrough_656

The project promoter said the two Herrenknecht variable pressure TBMs had between them driven through more than 3 million cubic metres of chalk at depths of up to 80 m. Progress was on average 16 m/day, and the machines installed 56 000 precast concrete tunnel segments in a rolling ‘factory’ located behind the cutting faces.

The machines were operated by the Align JV of Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick.

‘Today is a remarkable achievement for all concerned. Cecelia’s arrival completes excavation of HS2’s 16 km twin-bore tunnel, but it’s only the end of the first chapter in the story of building Britain’s high-speed railway under the Chiltern Hills’, said HS2 Ltd’s head of civil works for this section of the route, Mark Clapp. ‘Several years of intensive, world class engineering lie ahead of us to complete the tunnels’ four ventilation shafts plus headhouses; install the mechanical and electrical plant and machinery, slab track and overhead electrical wires.’

The truncated HS2 route is expected to open between Old Oak Common in west London and Birmingham Curzon Street in the early 2030s.