TBM Emily lifted after 3.4-mile HS2 tunnel drive

HS2 has lifted a third tunnel boring machine (TBM) to the surface in west London, following the completion of a 3.4-mile section of the Northolt Tunnel.

On Saturday 26 July, the TBM known as Emily was lifted from the Green Park Way shaft in Greenford. The operation involved hoisting the machine’s 9.11 metre diameter cutterhead, front and middle shield — weighing 880 tonnes in total — using a large gantry crane.

Emily had previously completed her underground journey from Victoria Road in Ealing, arriving in a purpose-built reception chamber last month. During the drive, the TBM excavated approximately 775,000 tonnes of London Clay and installed 17,514 precast concrete segments, forming 2,189 tunnel rings. Each segment weighed around 7 tonnes and was part of a tunnel lining system designed to tight tolerances to ensure long-term durability under high-speed rail loads.

The machine is one of four used to construct the twin-bore Northolt Tunnel, which will carry HS2 trains between Old Oak Common and the outskirts of London. The fourth TBM is expected to be removed later this summer following the completion of its own drive.

In line with HS2 tradition, the TBM was named after a local historical figure: Emily Sophia Taylor, who helped establish Perivale Maternity Hospital in 1937 and later became Ealing’s first female mayor.

The London tunnels for HS2 are among the most technically complex parts of the route, with more than 83,000 precast concrete segments due to be produced and installed across the various drives. All segments are cast offsite using high-performance concrete and steel fibre reinforcement, designed to reduce embodied carbon while maintaining structural integrity.

The completed Northolt tunnel section marks another major milestone for the project’s civil engineering phase in the capital. HS2’s contractors for the London tunnels include Skanska Costain STRABAG JV, with STRABAG also operating the Hartlepool precast facility that manufactures the segment rings.