Flying shield tunnelling' method comes to the UK
20 February 2013The construction of Thames Tunnel got off to a good start due to a new tunnel machine launch method developed by Hochtief, Crossrail announced recently. This is the first time that the technique, flying shield tunnelling, has been used in the UK, having previously been used in Cologne, Germany, in 2005.
The pioneering method focuses on the very start of tunnelling, when the TBM cannot yet support itself on newly created tunnel walls. Traditional methods use a steel support structure and six or seven dummy concrete rings for the machine that provides a surface for the machine to brace itself against to push forward and begin tunnelling. However, the Hochtief method uses a hydraulic system to pull the TBM forward. As a result, the temporary tunnel is not needed.
Crossrail stated that it makes the launch quicker and that this approach also safer because it requires less space, making it ideal for constrained sites, such as Plumstead.
Sophia, Crossrail's fifth tunnelling machine, began her journey from Plumstead to North Woolwich earlier this year as part of the construction of a tunnel under the River Thames. The 110m long machine is scheduled to drill at an average rate of around 100m a week, installing precast concrete segments as rings to form the tunnel lining as it advances forwards.
