Engineering’s past and present intersected beneath the River Thames last weekend as the tunnelling machine digging London’s ‘super sewer’ passed beneath Brunel’s Thames Tunnel near Wapping.
Tunnel Boring Machine Selina is constructing the final 5.5km stretch of the Thames Tideway Tunnel between Chambers Wharf in Bermondsey and Abbey Mills Pumping Station. Heading eastbound, the machine successfully crossed beneath the Thames Tunnel, which connects Rotherhithe and Wapping.
The original tunnel was constructed between 1825 and 1843, started by Marc Brunel and completed by his son Isambard Kingdom Brunel. It was the first ever use of a tunnelling shield, a technology still employed by Tunnel Boring Machines today – six of which have constructed the ‘super sewer’.
The shield was invented by the elder Brunel and Thomas Cochrane and was patented in January, 1818. Its key innovation was its support for the unlined ground in front and around it to reduce the risk of collapse. Despite challenges in construction, the 396-metre tunnel running at a depth of 23 metres is known as the first to have been built successfully underneath a navigable river.
Today, Tunnel Boring Machine Selina’s front shield and cutterhead weigh almost 800 tonnes while its diameter is over 8 metres. With the accompanying six gantries the TBM weighs almost 1500 tonnes and stretches 111 metres.
Tideway Programme Director Andy Alder said: “This was a historic event on Tideway over the weekend when the eastbound TBM passed under Brunel’s Thames Tunnel. That was the first ever use of a tunnelling shield, and while they experienced some major challenges, they paved the way for the TBMs that we use today. Well done to the team for safely tunnelling underneath this historic asset – a key moment in our Tideway programme.”
Selina was the last on the Tideway project to get underway, journeying to Abbey Mills Pumping Station and will complete the tunnelling phase of the 25km-long Thames Tideway Tunnel under construction to intercept sewage overflows before they pollute the River Thames.
The machine is named after Dr Selina Fox, who founded the Bermondsey Medical Mission in 1904. The small clinic and eight-bed hospital continues to this day as a local charity.