Steel props aid construction of new Thames tunnel

A series of steel tubular props are being installed to aid the construction of the Silvertown Tunnel, which will provide a new road link under the River Thames between North Greenwich and east London.

A total of 247 CHS props, ranging in length from 9m to 41.5m, are being supplied by Severfield to support the 600m of access ramps at both ends of the tunnel. Overall, the company is fabricating and supplying 4,000t of steelwork for the project, including 600t of waler beams.

The 1.4km-long twin-bore tunnel is being delivered by a joint venture between Ferrovial Construction, BAM Nuttall and SK E&C.

Following a similar route to the alignment of the Emirates Air Line cable car, the project has been designed to ease congestion around the adjacent and existing Blackwall Tunnel.

Only one tunnel boring machine (TBM), with a diameter of approximately 12m, is being used to bore both tunnels through geology including alluvium, London clay and the Lambeth Group. Launched in Silvertown, the TBM has completed the first tunnel and, having been rotated in North Greenwich, it is now working on the return second tunnel.

Overall, the construction team will manage a total excavation of 600,000m³ and 100% of the suitable excavated material will be transported away from site by river, minimising the impact of construction traffic for neighbouring communities and routes.

The project is expected to be completed in 2025.