The first shutter, which will be used to cast the secondary lining of the new super sewer, has been lowered to the bottom of the shaft at Tideway’s Kirtling Street site.
The shutter is one of two which will be used to create the secondary lining for the 5km stretch of tunnel from Kirtling Street to Tideway's Carnwath Road site in Fulham. Millicent, the westbound tunnel boring machine (TBM) launched from Kirtling Street, completed excavation of this section of the tunnel in November 2019.
Each shutter weighs approximately 240 tonnes and totals 34m in length. Due to the size and weight of the machine, it was split into four pieces to be lifted to the bottom of the shaft before being reassembled deep below ground.
The shutters will move along the main super sewer tunnel, casting a 250mm thick layer of concrete against the tunnel’s primary lining made up of concrete segmented rings, reducing the total diameter of the tunnels to 7.3m.
The secondary lining provides the tunnel with further resistance to abrasion, ensuring the 120 year design life, while ensuring a smooth and consistent finish. Sewage will flow eastbound along the tunnel at a natural gradient meaning there is no need for pumps to be installed in the system.