HS2 engineers are set to start the installation process of 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.”
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.”
(Pictures: HS2 Ltd)
