Sprayed concrete mined tunnels complete key HS2 station connection

HS2 has completed the twin mined tunnel connections between the Victoria Road crossover box and Old Oak Common station in west London, creating a continuous underground link between the future station and the West Ruislip tunnel portal.

The two tunnels are each approximately 360 m long and were excavated through London Clay using conventional tunnel excavators rather than tunnel boring machines. Excavation began from the Victoria Road crossover box in May 2024, with around 100,000 tonnes of material removed during the works, all of which has been taken to reuse projects in the UK.

The construction method was selected because the tunnel geometry changes significantly between the crossover box and the station. Each tunnel narrows from a width capable of accommodating two tracks to a single-track profile, making conventional mined excavation better suited to the changing cross-section.

Following excavation, the tunnels were initially supported using sprayed concrete, with approximately 30,000 m3 applied during construction. A permanent cast in situ concrete lining was then installed using travelling formwork.

The latest breakthrough into the station box, marked by a visit from Rail Minister Lord Hendy, followed completion of the northbound connection on 13 October and created a continuous 8.8 mile, or 14.2 km, underground route from Old Oak Common to the West Ruislip portal on London's northwestern edge.

A distinctive method was used for the final breakthroughs into the station box. Rather than demolishing the separating wall conventionally, the dividing wall was cut into blocks and pushed Jenga-style from the station side back into the completed tunnel behind, allowing them to be removed in a controlled sequence.

The approach had not previously been used elsewhere on HS2 and was adapted to the confined geometry around the station interface. David Hannon, Operations