Construction of the giant network of tunnels for HS2 has passed the halfway point, marking a major milestone for Britain’s new high-speed line.
HS2 is currently at peak construction and has completed the excavation of two of its five twin-bore tunnels, while the excavation of a further two tunnels is well underway.
In total, 27.4 miles of the 140-mile route will pass through tunnels, meaning that HS2s fleet of tunnel boring machines (TBMs) must excavate 54.8 miles of tunnel.
New analysis shows that the TBMs have so far excavated 29 miles, or 53%, of the required total, surpassing the length of tunnels bored for the Crossrail line beneath London.
Rail Minister Huw Merriman said: “Reaching this impressive milestone on a project of HS2’s scale shows just how much momentum is behind construction of the line, which, once complete, will have a transformative impact on rail travel for generations to come.
“It’s a significant achievement for the team helping deliver this railway and I’m delighted the project has now supported record numbers of new jobs, demonstrating the vital role it is playing in creating opportunities up and down the country.”
Two tunnels have already been fully excavated. In March 2023, TBM ‘Dorothy’ completed its second drive of the one-mile Long Itchington Wood Tunnel in Warwickshire.
In addition, TBMs ‘Florence’ and ‘Cecilia’ completed both drives of the 10-mile Chiltern Tunnel, the longest tunnel on the route.
The 8.4 mile Northolt Tunnel in London is currently being excavated, with four TBMs each at various stages of their drive. The fourth machine, ‘Anne’, has only just begun her drive.
TBM ‘Mary Ann’ is 1.3 miles into her 3.5-mile drive as she bores the Bromford Tunnel in the Midlands.
Meanwhile, excavation of the fifth and final tunnel, the Euston Tunnel, is yet to commence. Significantly preparatory works have already been completed, and two TBMs are currently being manufactured and tested ahead of their 4.5-mile dig.
Each TBM operates like an underground factory, excavating the tunnels, lining them with concrete segments and grouting them into place. The machines progress by between 12 and 16 metres each day.
Once the TBMs have completed their drives, HS2 will move to the next stage of the tunnelling project, which will see the completion of other vital structures such as cross-passages, vent shafts and portals.
The rest of the HS2 route includes six cut and cover, or ‘green’ tunnels, totalling 5.2 miles, and 70 cuttings totalling 44 miles. This means that around 76 miles of the 140-mile route will be below ground level in tunnels and cuttings.
Image and video credit: HS2
