By rosebell
As an indication for completion of major tunnel excavation between London’s Old Oak Common and the West Midlands, breakthrough was made on HS2’s Birmingham approach tunnels on 13 Octoer.
The launching location of the 125m-long TBM Elizabeth, named after the 19th century philanthropist Elizabeth Cadbury, was near the Warwickshire village of Water Orton in March 2024, whereas it finished its journey at Washwood Heath.
With the aim of carrying high-speed trains beneath the M6 and eastern outskirts of the city, Balfour Beatty Vinci (BBV) used two TBMs to bore the 5.6km-long Bromford tunnel and the date of commissioning TBM Mary Ann was May this year.
The quantity of excavated material by Elizabeth and Mary Ann is over than 1.8 million tonnes, while they 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.
Considering the breakthrough on 13 October, currently digging process is complete for the 45km of deep-bore tunnel between Old Oak Common in west London and the railway’s terminus at Birmingham Curzon Street and construction teams are now mainly focused on internal walkways, ventilation shafts and cross passages.
Despite that this landmark is a remarkable achievement for the teams in Birmingham, other parts of the railway’s civil engineering are further behind.
In order to delivering the railway in the most efficient way possible and for the lowest reasonable cost, HS2 Ltd chief executive Mark Wild is leading a comprehensive reset of the program.
According to HS2 Ltd construction delivery director Alan Morris: “I am immensely proud of the men and women who have worked round the clock to bring our TBMs and their crews home safely.”
Benefiting eight TBMs, already 9.4 million tonnes of material has been excavated on this project. With 16.1km length the Chiltern Tunnel is the longest on the route, and the Northolt tunnels stretch for 13.5km from West Ruislip to Old Oak Common in west London. There is a short 1.6km twin-bore tunnel beneath Long Itchington Wood in Warwickshire
For commencing digging the tunnels from Old Oak Common to HS2’s London Euston destination, two more TBMs are expected to be started upin the coming.
Also a short section of mined tunnel is being dug between the Victoria Road Crossover Box and Old Oak Common.
Moreover, delivering almost 8km of shallow cut-and-cover tunnels in rural areas such as Burton Green in Warwickshire, Chipping Warden in West Northamptonshire and Wendover in Buckinghamshire, is the plan of HS2 alongside these deep tunnels.
The working location of team building the Bromford tunnel over their 18-month mission was at depths of up to 40m . They navigated the two TBMs under the M6 motorway, key National Grid infrastructure and the River Tame, which they crossed four times, with an overburden as low as 5m.
In order to advancing work on the concrete finishing works, base slabs, as well as emergency and maintenance walkways, TBM Elizabeth is now due to be removed from the tunnel.
“Everyone connected with the project felt a sense of achievement and pride and the breakthrough followed years of planning and preparation. This has allowed us to guide Elizabeth safely and successfully underneath complex ground conditions and critical live infrastructure. A breakthrough is always a unique moment, and it marks the culmination of exceptional engineering, dedication, and collaboration,” said Balfour Beatty Vinci tunnelling director Jules Arlaud.
As well as being the arrival point for the two Bromford tunnel TBMs, Washwood Heath will also become the nerve centre for HS2’s operations. HS2’s Depot and Network Integrated Control Centre will be built next to the tunnel portal. Here trains will be serviced and stored, and the real-time operation of the railway will be controlled.
