The breaking out of the concrete plugs either side of the shaft at Blackfriars Bridge Foreshore signals the next step in secondary lining the main ‘super sewer’ tunnel. The operation also means all sections of the main tunnel are now connected up to where Tunnel Boring Machine Selina is digging the final eastbound stretch towards Abbey Mills.
The removal of the east and west plugs last weekend allowed the tunnelling team to take over the shaft bottom to install rails which will enable the secondary lining apparatus to cross the shaft on its way to the Chambers Wharf site in Bermondsey.
As the Blackfriars shaft was excavated through the main tunnel, the portion beneath was filled with foam concrete to ensure the team wasn’t excavating into a void.
Around 1,500 tonnes of removed grout material will be taken away by barge on the River Thames, preventing the need for hundreds of lorry journeys on London’s streets.