Transition Completes the Tunnel

Riverlinx CJV has reached another significant milestone after completing construction works for the connections between the open cut approaches and the tunnelling section of the Silvertown Tunnel.

Riverlinx CJV, a construction joint venture of Ferrovial Construction, BAM Nuttall and SK ecoplant working on behalf of Transport for London, celebrated the news after the final transition section of the tunnel was cast in Silvertown on 11 April 2024. This completes the work to connect both Northbound and Southbound tunnel structures from the Silvertown portal to the Greenwich portal. A complete transformation of the tunnel shape was needed to connect the circular TBM-constructed tunnel to the in situ concrete arch shaped Cut & Cover tunnels.

To construct the four transitions, a self-propelled, self-erecting formwork was used, nicknamed “The Crab”. This 70 tonne tracked structure was moved into position and folded out to create the unique shape using hydraulic rams. The Crab then acts as a temporary structure for the installation of steel reinforcement before concrete is placed and allowed to cure. Once the concrete has cured enough to be self-supporting, the machine folds the shutters inward for transport through the bored tunnel to the next transition location.

Below left is the bespoke formwork, a miniature version of the transition traveller, which functions in a similar way to the Crab, with the sides folding inward to enable striking the formwork out and removal. The final of eight cross passages, which all allow people to travel between tunnels in case of emergency, is now ready for fit-out to commence, below right.

Left: A wall shutter fitted with the Reckli form liner used to create the distinctive patterned finish to the walls of the Open Cut sections that will greet tunnel users in both Silvertown and Greenwich.

Creative use of architectural design has been incorporated throughout both the Tunnel and the Portal Building on the north side of the Thames. Considerable progress has been made on The Newham Portal Rotunda copper rainscreen cladding has been designed with aesthetics and sustainability in mind. Its cladding has continuous horizontal welted seams, which align precisely with the top and bottom edges of the windows, creating a subtle, seamless connection between the openings.

This is contrasted by deep vertical standing seams which help accentuate the tower's height. These seams, which are aligned with window openings and equally distributed across the façade, cast dynamic and ever-changing shadows throughout the day.

This deliberate arrangement gives a sense of balance and rhythm to the overall architectural composition and architectural lighting will also illuminate and enhance the facade material at night.

The project is now moving towards the completion of the final stages, and remains on track for the new tunnel to open in 2025.