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Factory testing complete for Sophia, Crossrail’s first slurry machine

By Juliet Whitcombe

Factory testing complete for Sophia, Crossrail’s first slurry machine

Sophia, Crossrail’s first slurry tunnel boring machine (TBM), has passed her factory testing and will now be dismantled and moved to the Plumstead work site later this year.  Sophia is Crossrail’s fifth TBM to complete factory testing and assembly of our sixth TBM, Mary, is also underway.

Sophia is named after the wife of Marc Isambard Brunel who built the first tunnel under the Thames.  Mary is named after the wife of the famous railway engineer Isambard Kingdom Brunel.

Sophia and Mary are Crossrail’s only mix shield or “slurry” TBMs and will be used to construct a new 2.6km tunnel beneath the River Thames, travelling westbound from Plumstead to North Woolwich.  Slurry TBMs are designed to tunnel in a wide range of ground conditions, using bentonite (a slurry of clay and water) to support the excavation face as they tunnel.

The project will also use six Earth Pressure Balance Machines to tunnel through ground which is predominantly London clay, sand and gravels.  A total of eight TBMs will undertake 10 tunnel drives to construct the Crossrail running tunnels. 

Crossrail’s first two TBMs, Phyllis and Ada, launched earlier this year and will construct the 6.4km of western tunnels between Royal Oak and Farringdon.

Elizabeth and Victoria have been delivered to our eastern tunnels launch site near Canning Town and are being assembled ready for launch later this year.  At approximately 8.3 km in length, Limmo Peninsular to Farringdon will be the longest of the Crossrail tunnel drives. 

A further two TBMs will be used to construct the remaining tunnels between Pudding Mill Lane and Stepney Green (2.7km) and Limmo Peninsular to Victoria Dock Portal (0.9km).