HS2 C1 – Cecilia Breaks Through

Tunnel Boring Machine (TBM) Cecilia has successfully completed excavation of the second of the two 16 km long bored tunnels through the chalk of the Chiltern Hills. Following on the heels of TBM Florence, which finished its run on February 27th of this year, Cecilia started its journey in June 2021 and broke through at the tunnel’s northern portal on March 21st.

Gall Zeidler Consultants (GZ), as part of the Align JV team, provided the design for all cross passages, the ground treatment design, and are serving as a geotechnical specialist with on-site support during construction.

 A video of the breakthrough can be seen here.

If you are interested in GZ’s involvement with the project, visit our project page.

Screenshot of HS2 video showing the Breakthrough of TBM Cecilia on March 21st, 2024. (Source: HS2 Youtube Channel – Final breakthrough for HS2’s longest tunnel)