We are excited to share that the construction of the Chiltern Tunnel, a 10-mile twin-bore tunnel and the longest on the HS2 route, the South Portal porous portal structures and the associated earthworks have been successfully completed.

Construction began in 2020 at the South Portal—the launch site for Tunnel Boring Machines Florence and Cecilia. Tunneling commenced in spring 2021, with both TBMs completing their drives to the North Portal in early 2024.

Following the TBM breakthroughs, the team has finalized a range of complex underground works including 38 cross passages, 5 adits, the removal of TBM services and slurry pipelines, the construction of emergency walkways, crossover slabs, drainage systems, and the completion of the South Portal structures.

Gall Zeidler Consultants (GZ) as part of the Align Team, provided the design for all cross passages, the ground treatment design and are serving as a geotechnical specialist. GZ’s scope also included the development of the Geotechnical Baseline Report, the Durability Report and Tunnel Obstructions Assessment as well as the Settlement and Potential Damage Assessment.

We extend our congratulations to Align JV, AlignD JV,  and everyone involved in reaching this remarkable milestone on the HS2 program and are proud to be part of this iconic project.

For more information about GZ’s project involvement please visit our project page.

To view full news entry please visit this link.

Project team coming together to recognize this milestone moment on the HS2 Ltd program. (Courtesy of Align JV / HS2 Ltd)