[VIDEO] HS2 celebrates final boring tunnel breakthrough

The 125-metre-long tunnel boring machine – named Elizabeth after the 19th century philanthropist Elizabeth Cadbury – was launched near the Warwickshire village of Water Orton in March 2024 and arrived at Washwood Heath yesterday morning(13 October)

Two identical boring machines were used to dig the 3.5-mile long Bromford tunnel that will carry high speed trains under the M6 and eastern outskirts of the city, with the first one – Mary Ann – breaking through earlier this year.

Together, Elizabeth and Mary Ann have excavated more than 1.8m tonnes of material and installed 5,804 concrete ring segments for the twin, eastbound and westbound tunnels. The spoil – made up of various grades of Mercia Mudstone – is being used to landscape the railway on the approaches to the city.

This milestone means that all the excavation is now complete for the 23 miles of deep bore tunnel between Old Oak Common in west London and the railway’s terminus at Birmingham Curzon Street. Construction teams are now mainly focused on internal walkways, ventilation shafts and cross passages.

All major HS2 tunnelling works have broken through

Alan Morris, HS2 Ltd’s construction delivery director said: “Today’s breakthrough is a major milestone for the tunnelling team here in Birmingham and for the HS2 project. All eight of the TBMs digging our tunnels between Old Oak Common and Curzon Street have now broken through, which means that the focus is now on the internal concrete work, ventilation shafts and cross passages.

“I’m immensely proud of the men and women who have worked round the clock to bring our TBMs and their crews home safely, and I look forward to seeing more progress inside the tunnels in the years ahead.”

Each TBM is an underground factory – working 24/7 to excavate, install the concrete ring segments that form the walls and grout them into place as it moves forward at an average speed of around 10 metres per day.

Eight TBMs have been used on the project so far, with an incredible 9.4m tonnes of material excavated during their tunnel drives. The longest tunnel – under the Chilterns – stretches for 10 miles, while the Northolt tunnels run for 8.4 miles from West Ruislip to Old Oak Common in west London. Additionally, there is a short 1-mile twin bore tunnel beneath Long Itchington Wood in Warwickshire.

Two more TBMs are expected to launch next year to begin digging the tunnels from Old Oak Common to HS2’s final destination, London Euston. A short section of mined tunnel is also being dug between the Victoria Road Crossover Box and Old Oak Common.

With the breakthrough complete, Elizabeth will now be removed from the tunnel to allow work to progress on the concrete finishing works, base slabs, and emergency and maintenance walkways.

“The culmination of exceptional engineering, dedication, and collaboration.”

Jules Arlaud, Balfour Beatty VINCI’s tunnelling director, said: “Today is a historic moment for Balfour Beatty VINCI, as TBM Elizabeth completes her three-and-a-half-mile journey in Washwood Heath. This is BBV’s fourth and final TBM breakthrough, delivered by our expert tunnelling team who’ve worked around the clock over 19 months to arrive at this point.

“A sense of achievement and pride is felt by everyone connected with the project and follows years of planning and preparation. This has allowed us to guide Elizabeth safely and successfully underneath complex ground conditions and critical live infrastructure, including energy networks, the M6 and the River Tame. A breakthrough is always a unique moment, and it marks the culmination of exceptional engineering, dedication, and collaboration.”

Apart from this milestone, HS2 is notoriously behind schedule

Although the tunnel milestone marks a significant achievement for the teams in Birmingham, other parts of the railway’s civil engineering are further behind.

Mark Wild, HS2 Ltd’s chief executive, is now leading a comprehensive reset of the programme to deliver the railway in the most efficient way possible and for the lowest reasonable cost.

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