The Old Oak Common excavation has taken three years, after permanent construction to form the walls of the box began in June 2021.
The underground box has a 1.12-mile fibre-reinforced concrete diaphragm wall around it, and 1.3m tonnes of London Clay has been removed from inside.
Join venture contractor Balfour Beatty Vinci Systra (BBVS JV), working with their specialist structures contractor Expanded, completed the excavation section by section within the box, starting from the west and the east sides of the structure and meeting in the middle.
The box is 20 metres deep and a reinforced concrete base slab up to two metres in depth is being poured throughout. Some 32,000 tonnes of steel rebar, assembled by hand on site, has been used in the box alongside 160 reinforced concrete columns that have been installed inside the outer wall to help support the structure.
Now the box has been full excavated, the team will be working to pour the final sections of base slab to fully complete the box.
The east end of the underground box has been handed over to HS2’s London Tunnels contractor, Skanska Costain Strabag (SCS JV), which is are preparing to construct HS2’s running tunnel to Euston. Two giant boring machines will be lowered into the underground box later this year, before the station team commencing building the roof structure of the super-hub station. Timings and funding for the construction of the Euston Tunnel are subject to government decisions that have yet to be made.
Six 450-metre platforms will be constructed in the underground box for HS2 services. Above ground, eight further platforms are being built, and will be served by the Elizabeth Line, Great Western Mainline services and the Heathrow Express.
The east end of the underground box has been handed over to HS2’s London Tunnels contractor, Skanska Costain Strabag (SCS JV), which is are preparing to construct HS2’s running tunnel to Euston. Two giant boring machines will be lowered into the underground box later this year, before the station team commencing building the roof structure of the super-hub station. Timings and funding for the construction of the Euston Tunnel are subject to government decisions that have yet to be made.
Sam Clark, head of delivery for HS2 Ltd, said: “The tremendous progress made by our construction team to complete the excavation of the box is an exciting milestone for the project as it signals the next phase of construction where high speed platforms will be built, as well as the station building itself. HS2’s Old Oak Common station will be transformational for local and regional connectivity and attract huge investment, development and regeneration to the surrounding area.”
The huge amount of London Clay removed in the excavation has been taken away from site by a purpose-built conveyor, run by Fairport, took the nearby London Logistics Hub, managed by SCS JV, from where it has been transported by rail to reuse sites in Kent, Warwickshire and Cambridgeshire. With excavation now complete, the conveyor has been decommissioned.
When HS2 opens, Old Oak Common will be its southern terminus. It is presumed that this will only be a temporary situation and the line will continue on to Euston in due course.
Plans to develop the wider area around the station, a former railway and industrial site, are being led by the Old Oak & Park Royal Development Corporation (OPDC).
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