By rosebell
The tunnel forms part of National Grid’s Great Grid Upgrade and will accommodate a high-voltage electricity cable linking Tilbury in Essex with Gravesend in Kent.
TBM Caroline Completes Thames Crossing
On September 27, TBM Caroline completed the final stage of excavation beneath the River Thames. During the breakthrough, the reception shaft was flooded to balance pressure between the shaft and the surrounding chalk and reduce the risk of groundwater entering the shaft.
National Grid’s delivery partner, Ferrovial BEMO JV, completed the drive 49 days ahead of the original programme, following what the company described as exceptional tunnelling performance.
Planning, favourable ground conditions and the TBM’s performance contributed to the accelerated programme. Continuous delivery of tunnel segments and efficient processing of excavated material through a dedicated separation plant also helped maintain production.
10,000 Tunnel Segments Installed
More than 10,000 precast concrete segments were installed to form the tunnel lining, creating almost 1,700 tunnel rings.
The Mixshield TBM achieved its highest monthly production rate at 926m, installing 712 tunnel rings during the same period. Its best weekly performance reached 229m, while the highest daily output was 41m of excavation and 31 tunnel rings installed within 24 hours.
Digital Technology Supports Tunnel Drive
Digital design tools and connected TBM data were also used throughout the project to improve visibility, quality assurance and construction decision-making.
An integrated underwater telescopic camera enabled remote inspections during the final stages of the drive, reducing the need for personnel to enter the shaft or work directly in challenging underwater conditions.
The completed tunnel will form a key part of the new high-voltage connection between Tilbury and Gravesend, supporting National Grid’s wider programme to upgrade electricity infrastructure across Great Britain.
