Another key milestone has been achieved at the UK’s Hinkley Point C construction site in Somerset, with the completion of the first of three off-shore tunnels needed for the power station’s cooling-water system. The first TBM, named Mary, reached the end of her 3.5km journey under the Bristol Channel to complete intake tunnel 1 on 9 December 2020.
Roger Frost, Balfour Beatty Project Director, said: “This is a significant achievement – one that marks another step towards the successful delivery of the UK’s landmark nuclear power station, Hinkley Point C. The unrivalled expertise of our people, combined with our state-of-the-art offsite manufacturing facility in Avonmouth, has made it possible for us to break through the first of three off-shore tunnels. I am immensely proud of the commitment everyone has shown.”
The 3.5km-long, 7m diamter intake tunnel 1 was mined at a depth of 33m below the Bristol Channel, using one of three Herrenknecht TBMs needed for the project.
The tunnel comprises more than 2,300 x 6 segment rings, with nearly 14,000 segments needed to complete the lining.
The nuclear-standard precast segments were produced at Balfour Beatty’s purpose-built manufacturing plant in Avonmouth and transported to site. Some 38,000 segments will be needed to complete the three tunnels.
Mary’s cutter head removed around 340,000 tonnes of earth, with muck removal via seven different conveyors, both belt conveyors and a ‘bucket’-style vertical conveyor, down the length of the tunnel, up and out of the bore. From here it was loaded onto trucks and used for landscaping on site.
Parts of the TBM will now be stripped and installed on another machine, with the remainder immortalised under the Channel as a time capsule to the incredible feat of engineering.
Attention now turns to the two remaining tunnels for the cooling-water system. Emmeline, the largest of the TBMs, has just started on her 1.8km journey mining the outfall tunnel, and Beatrice, supplemented by equipment from Mary and responsible for intake tunnel 2, is set to launch early next year.