Connaught cofferdams10 February 2012
Crossrail announced that cofferdams will be placed in the Connaught Passage, water will be pumped out and a dry construction area created to allow workers to dig down to the tunnel and undertake enlargement works by cut and cover.
Crossrail originally intended to remove the existing steel linings and back fill the entire section with concrete firm. Enlargement would then be carried out by boring through the concrete to allow Crossrail trains to pass through.
Connaught Tunnel project manager Linda Miller said, “The central section of the Connaught Tunnel is in a poor structural condition. To ensure we can undertake the tunnel enlargement work as safely as possible we have now decided to drain a section of the Royal Docks and then dig down into the tunnel.
“This will be the first time the tunnel has been exposed from above ground since its construction in the 1870s. While we will be using modern techniques, we will be using a similar cut and cover approach that was used to build the original tunnel which saw the tunnel constructed first with the docks then built over the top.”
A Crossrail spokesman said, “Connaught Tunnel in the Royal Docks was built in 1878 and was part of the North London Line until 2006. The tunnel will be extensively refurbished as part of works to construct Crossrail’s new Abbey Wood branch.
“Sections of the existing tunnel are in a poor structural condition. In 1935, larger ships began scraping the bottom of the Royal Victoria Dock, which sits above the Connaught Tunnel. As part of work to deepen the dock, the central section of the tunnel was narrowed with brickwork removed and steel segments installed.”