Re-engineered tunnel invert design
£5 million saved
Delivered five months early
The North Downs Tunnel is an award-winning 3.2 kilometre tunnel with an internal finished diameter of 12.8 metres, built to carry the Channel Tunnel Rail Link (CTRL). One of the largest and deepest twin-track rail tunnels ever constructed in the UK, it carries trains at up to 300 kilometres per hour at depths reaching 100 metres beneath the chalk hills of the North Downs.
UnPS designed the primary lining and temporary works for this project, working collaboratively with the customer’s engineer to develop an innovative solution for the secondary lining.
As a consequence of a highly collaborative partnership between the customer and project delivery teams, UnPS led an extensive value engineering process with the customer and its designers that resulted in savings of £5 million.