Following the completion of a 1.6km drive beneath Long Itchington Wood in Warwickshire, the High Speed 2 (HS2) scheme has attained its very first tunneling breakthrough.
The first operator on the high-speed rail project to complete a bore, is HS2 Ltd’s main works civils contractor Balfour Beatty Vinci’s tunnel boring machine (TBM) Dorothy with 2,000t weight and 125m length.
Launching from the Long Itchington Wood tunnel’s north portal on 2 December 2021, the TBM broke through the wall of the reception box at the south portal site on Friday, 22 July, following seven months of excavation.
According to Balfour Beatty Vinci managing director Michael Dyke: “Thanks to the hard work and dedication of our team, Dorothy – our cutting-edge tunnel boring machine – has made history, becoming the first to safely and successfully breakthrough along the route.”
With help of around 400 people working for Balfour Beatty Vinci delivery of this milestone on the HS2 project was done.
The TBM has installed 790 concrete rings, with each ring made from eight 2m long segments.
In order to create both bores of the tunnel, the machine is removing almost 250,000m3 of mudstone and soil and the material is then transported to the on-site slurry treatment plant, where it is separated out before being reused on embankments and landscaping along the route.
The process of dismantling and transferring the cutterhead and front section of the TBM back to the north portal will be done over the next four months, while the bulk of the machine will be brought back through the tunnel. It will be reassembled, and ready to launch for the second bore of the tunnel.
Additionally, a conveyor with 254m length at the north portal site, which takes the dug material over the Grand Union Canal, removes the equivalent of approximately 30,000 HGVs from local roads.
HS2 Ltd’s CEO Mark Thurston said: “This is a historic moment for the HS2 project, and I’d like to congratulate everyone involved in delivering it. The 400-strong team, including tunneling engineers, TBM operators, and the construction workers at both portal sites, have pulled out all the stops to achieve this fantastic milestone.”
“This is, quite literally, a ground-breaking moment – demonstrating that we are getting on with delivering on our promises and progressing our transformative plans to boost transport, bring communities together, and level up the North and Midlands,” added HS2 minister Trudy Harrison.
While the intention is to preserve the ancient woodland above the tunnel, it is classified as a site of special scientific interest and has complex ecosystems that have taken hundreds of years to establish.