Euston tunnel is a

tunnel A tunnel is an underground or undersea passageway. It is dug through surrounding soil, earth or rock, or laid under water, and is usually completely enclosed except for the two portals common at each end, though there may be access and ve ...

currently planned in

London London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...

that will carry the

High Speed 2 High Speed 2 (HS2) is a high-speed railway which has been under construction in England since 2019. The line's planned route is between Handsacre – in southern Staffordshire – and London, with a Spur line, branch to Birmingham. HS2 is to ...

(HS2) railway between

Euston railway station Euston railway station ( ; or London Euston) is a major London station group, central London railway terminus and Euston tube station, connected London Underground station managed by Network Rail in the London Borough of Camden. It is the sout ...

and

Old Oak Common railway station Old Oak Common (OOC) is a railway station under construction on the site of the Old Oak Common TMD, Old Oak Common traction maintenance depot to the west of London in Old Oak Common, approximately south of Willesden Junction station. When bui ...

. Work to prepare the site for construction was undertaken in the late 2010s, such as the clearance of the old carriage sheds near Euston station in 2018. A legal challenge to the tunnel's design was defeated in mid-2020. During October 2020, HS2 Ltd ordered the two

tunnel boring machine A tunnel boring machine (TBM), also known as a "mole" or a "worm", is a machine used to excavate tunnels. TBMs are an alternative to drilling and blasting methods and "hand mining", allowing more rapid excavation through hard rock, wet or dry so ...

s (TBMs) from

Herrenknecht Herrenknecht AG is a German company that manufactures tunnel boring machines (TBMs). Headquartered in Allmannsweier, Schwanau, Baden-Württemberg, it is the worldwide market leader for heavy TBMs. Established by Martin Herrenknecht in 1975, the ...

that will excavate the tunnel.

History

To bring the HS2 high speed line into London, it was decided that a series of twin-bore tunnels underneath the city would be the most practical approach. These will have a combined total of , roughly equivalent in length to those built for the

Crossrail Crossrail is a completed railway project centred on London. It provides a high-frequency hybrid commuter rail and rapid transit system, akin to the Réseau Express Régional, RER in Paris and the S-Bahn systems of German-speaking countries, kn ...

programme. Responsibility for the construction of the section between central London and the M25 has been assigned to HS2's main works contractor, Skanska Costain STRABAG JV. In total, it has been envisaged that ten

s (TBMs) will be used to bore the of tunnelling along the HS2 route between the West Midlands and London. During 2018, the disused Euston Downside Carriage Maintenance Depot, close to Euston railway station, was demolished in order to clear space for the future construction work; the tunnel portal of the future Euston tunnel is to be present at this location. During 2019, a legal challenge to the design of Euston tunnel was launched by a local resident, alleging failures to address safety concerns; in June 2020, the High Court dismissed the challenge as "impossible to accept". During October 2020, HS2 Ltd signed a contract with the manufacturing group

to build and supply the two TBMs for Euston tunnel. These are to be custom-designed to suit the local

geology Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...

, which ground surveys indicated to consist largely of

clay Clay is a type of fine-grained natural soil material containing clay minerals (hydrous aluminium phyllosilicates, e.g. kaolinite, ). Most pure clay minerals are white or light-coloured, but natural clays show a variety of colours from impuriti ...

and

chalk Chalk is a soft, white, porous, sedimentary carbonate rock. It is a form of limestone composed of the mineral calcite and originally formed deep under the sea by the compression of microscopic plankton that had settled to the sea floor. Ch ...

, with which the tunnels are to be bored through. Delivery of the two TBMs was originally scheduled to take place sometime in late 2021. Initial boring was expected to begin in summer 2022, taking two years to complete. Boring is set to proceed on a non-stop working pattern, only shutting down temporarily for

Christmas Christmas is an annual festival commemorating Nativity of Jesus, the birth of Jesus Christ, observed primarily on December 25 as a Religion, religious and Culture, cultural celebration among billions of people Observance of Christmas by coun ...

and other bank holidays. During the excavation phase, it has been projected that of spoil (excavated material), weighing 2.46milliontonnes, will be removed by the TBMs. Between August 2021 and December 2033, a portion of

London Zoo London Zoo, previously known as ZSL London Zoo or London Zoological Gardens and sometimes called Regent's Park Zoo, is the world's oldest scientific zoo. It was opened in London on 27 April 1828 and was originally intended to be used as a colle ...

's car park is to be temporarily borrowed for use by construction vehicles while Euston Tunnel is being built. Work was paused in 2023, and was later announced that the line would not be extended into Euston without private funding. The two TBMs needed for the tunnels were lowered into the Old Oak Common station site in summer 2024, awaiting approval for the tunnels, to allow work on the rest of the station to progress. In the Autumn 2024 budget, funding commitments to complete the tunnelling were made, allowing for preparatory work to be completed by the end of the year and for tunnelling to begin from 2025.

Construction

Euston tunnel will be bored using

s launched from the western entrance, near

. The tunnel will be long, with an internal diameter of . At its deepest point, the tunnel will run below ground. The pre-cast concrete sections lining the tunnel will be manufactured by Pacadar UK at their factory on the

Isle of Grain Isle of Grain (Old English ''Greon'', meaning gravel) is a village and the easternmost point of the Hoo Peninsula within the unitary authority, district of Medway in Kent, south-east England. Once an island and now forming part of the peninsul ...

Kent Kent is a Ceremonial counties of England, ceremonial county in South East England. It is bordered by Essex across the Thames Estuary to the north, the Strait of Dover to the south-east, East Sussex to the south-west, Surrey to the west, and Gr ...

. These sections, each weighing seven tonnes, will be transported to site by rail. In excess of of concrete has been anticipated to be used to produce these sections. The use of

3D printing 3D printing, or additive manufacturing, is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer ...

technology will reportedly reduce the amount of concrete used in Euston tunnel in comparison to traditional methods. One of the few above-surface elements of the tunnel will be a three-storey building near Euston railway station, adjacent to the existing

West Coast Main Line The West Coast Main Line (WCML) is one of the most important railway corridors in the United Kingdom, connecting the major cities of London and Glasgow with branches to Birmingham, Manchester, Liverpool and Edinburgh. It is one of the busiest ...

, which will accommodate a diameter ventilation shaft from the surface to the twin tunnels below; this structure will also facilitate emergency access to the tunnel along with supporting electrical plant rooms. The top of this building will be covered by a green roof, stone-paved courtyard and have an entrance from Park Village East. In advance of the tunnel's boring, a smaller 853m long logistics tunnel is being bored using a separate smaller TBM that will facilitate access between the primary construction compound at Atlas Road and Old Oak Common Station, the launch site for the Northolt East and Euston TBMs, through which construction materials such as the precast concrete lining segments will be brought into the site and spoil removed. Boring on the Atlas Road Logistics Tunnel began with the launch of TBM ''Lydia'' (formerly TBM ''Ellie'' on the

project before being refurbished for HS2 by Herrenknecht) on 12 April 2023, and finished on 23 January 2024. Two long TBMs supplied by

will be used to bore the tunnels, with a cutterhead diameter of and weighing 1250 t each. They will start the drives in 2025, and are expected to take 18 months. They are named ''Karen'' after Karen Harrison, the UK's first female train driver, and ''Madeline'' after Madeline Nobbs, former president of the Women’s Engineering Society.

References

{{High Speed 2 articles Railway tunnels in London High Speed 2