On July 23, 2023, the site crews in London achieved the successful final breakthrough with the Herrenknecht EPB Shield in the Silvertown Tunnel project
180 Degree Turn With a 1450 Tonne Machine
When building twin-tube tunnels, usually either two TBMs are used or a single TBM is dismantled and returned to the original launch site for the second drive. However, due to the highly complex underlying conditions in terms of construction technology, time and finances, the project managers opted for a different, innovative approach for the Silvertown Tunnel: after completion of the first tunnel, the entire machine was rotated by 180 degrees in order to subsequently bore the northbound tunnel (click here to see a Video of the “U-turn”). To this end, the tunnellers specially excavated an 18 m deep and 40 m long shaft that was open at the top.
After the breakthrough of the first tunnel in February 2023, the 1450 tonne shield machine was rotated together with the cutting wheel by 180 degrees to drive the second tunnel in the opposite direction
In fact, turning such a huge machine required a special procedure developed by Herrenknecht: the shield machine and the cutting wheel are placed on a kind of sled. This in turn slides on cushions filled with compressed nitrogen so that with the help of pneumatic chain hoists the machine can be turned precisely and brought into the new position. The method had already been successfully used in Paris and on the new Stuttgart-Ulm railway line. The 180 degree turn of the 1450 t shield machine in London was accomplished by the Herrenknecht specialists in a single day.
The client of the Silvertown Tunnel project is Transport for London, the institution responsible for road, rail and public transport in the British capital. It awarded the contract for the design, construction, financing and operation of the project to the Riverlinx CJV (Construction Joint Venture) in November 2019. The joint venture comprises Ferrovial Agroman, BAM Nuttall Ltd and SK Engineering & Construction Ltd.