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BREAKTHORUGH FOR LONDON'S NEWEST UNDERGROUND TUNNEL
ALL PHOTOS: HERRENKNECHT
Construction is currently ongoing in London, UK, on the Silvertown Tunnel to address chronic congestion in the Blackwall Tunnel.
This will be the first newly built underground road link between the two banks of the Thames in over 30 years. The tunnel spans 1.4km and has two lanes on each side. It was excavated using a Herrenknecht TBM with a shield diameter of almost 12m, the largest ever used in the country.
The machine weighs 1,800 tonnes and is 82m in length. As of July 23, 2023, ‘Jill’ had inserted 1,120 segmental rings, weighing approximately 70 tonnes each, to reinforce the tunnel.
The Riverlinx CJV joint venture completed the southbound tunnel breakthrough in February 2023. Typically, Herrenknecht says, twin-tube tunnels are built using either two TBMs or a single TBM that is dismantled and returned to the original launch site for the second drive.
However, the Silvertown Tunnel project managers opted for a different approach. After completion of the first tunnel, the machine was rotated 180 degrees to bore the northbound tunnel. This required the excavation of an 18m-deep and 40m-long open-top shaft.
Herrenknecht developed a special procedure to turn the 1,450-tonne shield machine. The shield machine and cutting wheel were placed on a sled, which slid on cushions filled with compressed nitrogen. Using pneumatic chain hoists, it was turned and brought into the new position in a single day.
iC