Tunnelling complete at Silvertown
Jill, our Tunnel Boring Machine (TBM) which is delivering the Silvertown Tunnel in east London, has now completed work on the second bore, meaning that all main tunnelling work on the new river crossing is completed.
The TBM, named in honour of Jill Viner, the first female bus driver in London, completed the 1.1km (1106m) drive from Greenwich to Newham in late July 2023, after completing the first bore in February 2023, meaning that all main tunnelling works were completed in less than a year.
Aside from a small section around the tunnel entrances being built using a ‘cut and cover’ technique, the two bores that make up the Silvertown Tunnel have been built using one 82 metre-long, 11.9 metre-diameter TBM. During tunnelling of the second bore, the TBM averaged around 22 metres a day as it worked its way under the river from Newham to Greenwich.
The conveyor system, built to remove TBM bored materials, has helped transport more than 780,000 tonnes of spoil via barge so far. The use of river transport to deliver to or from the site has avoided the need for more than 60,000 HGV and other delivery vehicle journeys to date. All TBM bored materials from tunnelling are being transported along the Thames to a former landfill site in Essex as part of a restoration scheme.
The tunnelling of the second bore follows the successful rotation of the TBM in Greenwich, where it was placed on ‘nitrogen skates’ within a rotation chamber and turned around in a highly innovative and complex process. Spoil from the second tunnel was fed back via the conveyor systems installed within the first tunnel to allow it to be removed by barge from the Newham site.
With the main tunnelling work completed, we are now excavating the seven cross-passages which will run between the main tunnels. Passages will be built using either ground freezing or dewatering methods. Ducting which will be located underneath the carriageway within the tunnel is also currently being installed, so that by the end of the year the main road surface within the tunnel can start to be installed to allow for testing and final fitout of the tunnel systems to commence.
Work on the ‘cut and cover’ sections of the Silvertown tunnel, which includes the portal entrances, continue to be delivered, as well as the new road layout into the Tidal Basin roundabout in Newham, and link roads into the A2 south of the Blackwall Tunnel.
Helen Wright, Head of the Silvertown Tunnel programme for TfL, said: "The completion of tunnelling works on the Silvertown Tunnel is a massive milestone, and to complete it in under a year shows the hard work and close collaboration of everyone working on the project. Engineers are working around the clock to deliver this project with minimal impact to those living, working and visiting the local area and we remain committed to delivering a project that supports growth in the local area and provide new public transport connections across the river."
Juan Angel Martinez, Project Director at Riverlinx CJV said: “This is such an important milestone for the Silvertown Tunnel construction and I would like to congratulate everyone involved in delivering it. The technical expertise, focus and collaboration of this team have enabled us to safely complete the main tunnel drive to programme. The CJV formed by Ferrovial Construction, Bam Nuttall and SK Ecoplant has done a fantastic job implementing innovative and pioneering solutions for the UK such as the TBM rotation and frozen cross-passages. Working together with TfL as well as our many local stakeholders, Riverlinx is now focusing on the next stages of construction to successfully deliver this vital piece of infrastructure for London.”
This major milestone for the project follows the new walking and cycling bridge across the A102 opening to the public. TfL and Riverlinx are also actively working on the designs for the walking, cycling and landscaping improvements, which will be delivered around either side of the tunnel entrances. These will see new dedicated cycleways and footways, as well as 'shared space' and new public realm installed across Tidal Basin Road roundabout, which will link in with wider improvements planned by Newham Council across the Royal Docks area.
The proposed landscaping around the tunnel entrances, as well as a green roof on both tunnel portal buildings, will also form part of the scheme's commitment to environmental improvements and promoting biodiversity across the wider area – forming part of the Mayor’s wider plans to make London a cleaner and greener place to live, work and travel in.