The UK’s largest tunnel boring machine (TBM) has passed its factory acceptance tests and will soon be sent from the factory in Germany to the UK, to arrive in East London and start digging the Silvertown road tunnel under the Thames.
TBM at Herrenknecht (c) Riverlinx / TfL
The Silvertown Tunnel is a new “pay to use” road tunnel being built under the Thames that connects North Greenwich and Silvertown, and once open, the toll crossing is aimed at reducing congestion at the Blackwall Tunnel. However, it has been criticized for the risk that an improvement of road connections will attract more road traffic to the area. To alleviate this, the tunnel will have dedicated bus routes that use it for the purpose of improving river connections by public transport with a fleet of electric buses.
To build the £ 1.2 billion project, in addition to the tunnel entrances on each side of the river, a giant tunnel boring machine is needed to get under the river.
In general, road tunnels are much larger than railway tunnels, and this new TBM’s cutting head has a diameter of 11.9 meters, which is comparable to 9.1 meters for HS2’s tunnels and 7.1 meters for Crossrails tunnels. It also has an unusually heavy tunnel shield needed to cope with tunnel driving under the river. It weighs 1,200 tons, compared to 526 tons for the heaviest Crossrail tunnel shield.
TBM at Herrenknecht (c) Riverlinx / TfL
The length of the TBM is approximately 82 meters, with the majority of the length being the tunnel segment processor and waste disposal, plus space for the miners to work and rest during their long shifts. Although the Silvertown road tunnel will be double drilled to allow traffic in both directions, only one TBM will be delivered. It will start from the north side and drive to North Greenwich, where it will be turned around to dig the second tunnel.
Construction work is well underway and operations have been established on both sides of the river in preparation for the arrival of TBM. The first pieces have already started to arrive on site and are sticking to the program for launch in the spring of 2022. Due to the extraordinary weight of the components and the location of the sites, just over half of the equipment arriving at the construction sites will arrive with river barge.
The project will excavate almost 600,000 tonnes of material to form the tunnel – all of which will be taken away by barges along the river, where it will be recycled to landscape-contaminated soil at Ingrebourne to a game reserve and also at the Rainham Marshes.
The tunnel work is expected to start next spring, and the tunnel will open in 2025.
Silvertown site – with TBM launch shaft just behind the blue building (c) Riverlinx / TfL
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