HS2 engineers are ready to start installing the roof beams on a new box structure that will span both carriageways of the M42 near Solihull.
Once complete, vehicles will drive through the 300-metre-long ‘twin box’, while trains travel above.
The installation follows the successful completion of two supporting walls - constructed on either side of the carriageway. Inside the central reservation, a central pier of 46 supporting columns is nearing completion.
The 10-metre-high walls have been built using prefabricated hollow blocks, likened to giant Lego bricks. Weighing an average of 14-tonnes, each block was lifted into position and stitched together using reinforced concrete to support the 9,800-tonne beamed roof.
The walls and columns have been built using a modular construction approach, known as Design for Manufacture and Assembly (DfMA), which has significantly reduced the need for lengthy motorway closures.
With the walls now structurally complete, engineers working for HS2’s construction partner, Balfour Beatty VINCI (BBV), will turn their attention to the next significant phase - the beamed roof installation.
Over a series of four separate weekends in June, July, August and September, 175 prefabricated beams will be installed, each weighing between 56 and 92 tonnes. The 23-metre-long beams will be lifted into position using a 300-tonne crawler crane, effectively bridging the gap between the supporting walls and columns.
The scale and complexity of the operation means this element of the build can only take place during temporary closures of the carriageway. HS2 Ltd has worked closely with National Highways to agree the work schedule and determine access dates to the north and southbound carriageways.
The twin box structure is situated on the mainline of the HS2 route, less than a mile from where the new Interchange Station will be built in Solihull. It will carry four railway tracks over the motorway and sits directly between the Packington embankment and the Pool Wood embankment.
It is one of three major structures being built over the Midlands motorway network this year – alongside the Water Orton twin viaducts and the M6 South viaduct.
The design and installation approach for the twin box is spearheaded by UK-based Expanded Structures – a pioneer in modular bridge systems. The pre-cast elements for the twin box have been produced by Explore Manufacturing, a Nottinghamshire-based organisation which employs over 400 people at its facility in Worksop.
Agnes Usciak, HS2 Ltd’s Senior Project Manager for the works, said:
“This is a huge moment for the project, and a clear sign of the progress we are making as we begin bridging the gaps over the region’s motorway network.
“This is British engineering at its very best, and it’s fantastic that a UK-based firm has led the way in developing this innovative design solution for the twin box, with manufacturing taking place in the midlands.”
To minimise impacts on commuters, the roof installation works will take place at weekends and BBV and Expanded’s engineers have meticulously planned the construction schedule across the four allocated weekends. During each closure, the team expects to install around 44 beams, with the works scheduled to conclude in September.
Oliver Shore, Project Director at Balfour Beatty VINCI said:
“This ambitious structure, spanning a busy stretch of the M42 motorway near Solihull, is a huge engineering challenge which has required precision planning and close collaboration with many stakeholders.
“Now the supporting walls are complete, we’re getting ready to move to the next exciting phase of construction, which is the installation of the roof over four weekend carriageway closures throughout the summer.”
A team of 180 engineers and specialists from BBV and Expanded will lead the installation programme. They will work in shifts, around the clock, to ensure phase one is completed in time for the motorway to reopen at 5am on Monday, 29th June.
Expanded is playing a key role in HS2’s construction. In 2020, it installed the first permanent structure on the route of the railway – a modular bridge spanning the width of the M42. More recently, it was subcontracted to deliver the station box at Old Oak Common Station, including removal of 1.3 million tonnes of London clay.
Tim Rowe, Project Leader at Expanded said:
“Throughout the planning for this project it was an underlining principle that that there would be minimal disruption to road users. Our modular bridge solution offers a quicker and safer installation to that of traditional bridge construction, leveraging the benefits of off-site manufacture to take risk and disruption away from the site and public interfaces.
“Whilst the bridge is already an impressive structure we have been looking forward to this moment, installing the beams and connecting all the individual elements in one continuous structure.”
National Highways has played a pivotal role in the planning process for the twin box and has worked closely with HS2 and BBV to deliver a series of community events to ensure residents, businesses, and commuters are aware of the closure dates and the approved diversion routes.
M42 Northbound traffic road users are advised that the M42 will be closed from Junction 5a and are advised to leave the M42 at junction 5a to join the A4545 towards the A45 Coventry Road and then join the A45 eastbound to Stonebridge Island and then join northbound A452 Chester Road and continue on A446 Stonebridge Road/Lichfield Road to junction 9 and rejoin the M42.
Traffic wishing to access the NEC/Resorts World and National Motorcycle Museum will be able to gain access from A45/M42 junction 6 where signed exits are in place.
Ian Doust, National Highways’ Head of Network Planning and Development, said:
"Throughout the process our focus has been on minimising disruption for those who use our roads and we have worked closely with HS2 and their partners to that end. We welcome the innovative measures being taken which will substantially reduce the impact of this huge infrastructure project on our road users.
“We appreciate that there will still be some disruption during these weekend closures so we would advise people to leave extra time for journeys and choose alternative routes if at all possible.”
For more information about the planned closures and diversion routes, click here or visit www.hs2.org.uk/hs2-motorway-works
