A complex network of 13 viaducts under construction for HS2 has hit a major milestone, with the completion of the first 920-tonne deck span.
The 39-metre span was installed on the first precast segmented viaduct that is being built at Delta Junction in Warwickshire. Once complete, the River Tame West Viaduct will span 472 metres.
HS2’s Delta Junction is a triangular section of line, enabling trains to travel between London and Birmingham, Birmingham and Manchester, and direct between London and Manchester without stopping at Birmingham.
It is made up of embankments, cuttings and a total of 13 viaducts taking high speed tracks over motorways, local roads, existing rail lines, rivers and floodplains. The viaducts include six precast segmental viaducts, four composite viaducts, and three low viaducts.
The River Tame West Viaduct is a precast segmental viaduct at the northern tip of the Delta Junction, crossing the River Tame near Water Orton, and joins the Curdworth Box, which will take high speed trains over the existing Birmingham to Derby railway.
Sam Hinkley, HS2’s senior project manager for the Delta Junction, said: “This is a great moment for the Delta Junction team, as construction gets into full swing on this linchpin section of HS2. Building this triangular network of 13 viaducts is a huge feat of engineering, with a total of 10km of HS2 tracks crossing a network of motorways, local roads, railways and rivers to enable high speed trains to travel between London, Birmingham and the North.”
In this complicated section of the Delta Junction, there are six tracks of the railway running alongside each other as they join the southern end of the Curdworth Box. The River Tame West Viaduct carries three tracks, the River Tame East Viaduct carries one track and the Water Orton Viaducts carry two tracks.
To the south, the 1,400 metre Water Orton No.1 Viaduct and 1,300 metre Water Orton No.2 Viaduct curve towards Birmingham allowing trains to travel to and from Curzon Street Station. The other four lines – on the River Tame Viaducts – join on to the HS2 mainline to Interchange Station and on to London.
The 16 concrete segments for the first span were lifted by crane, placed one-by-one onto two 42 metre truss beams, moved into place with a skidding trolley, and secured by temporary and then permanent post-tensioning techniques.
The span, weighing 920 tonnes, was then jacked up and the truss was moved onto the adjacent abutment and pier, so the process can start again on the next span.
The three initial spans, all from the same abutment and next to each other, will be completed by Spring this year. The further spans will be constructed using temporary staying masts, swivel cranes, and temporary and permanent post-tensioning techniques.
The project is being delivered by HS2’s main works contractor for the West Midlands, Balfour Beatty VINCI (BBV), which is constructing 90km of HS2 between Long Itchington in Warwickshire to the centre of Birmingham and on to Staffordshire.
Nicolas Gallone, section manager at BBV, said: “It’s an exciting moment to see the River Tame West Viaduct starting to take shape, now we’ve successfully completed the first deck span. It’s the clearest sign yet of the huge progress we’re making on this complex network of viaducts, known as the Delta Junction.
“Construction of this iconic stretch of the route is set to ramp up further over the coming weeks and months, as we continue assembly of more deck spans along this 472-metre-long viaduct, and the adjacent viaducts that run alongside it.”
The delivery of all the design requirements for the BBV and HS2 works between London and Birmingham is through a Mott MacDonald and SYSTRA Design Joint Venture (MMSDJV). As well as bringing a wealth of in-house design knowledge and expertise, Mott MacDonald and SYSTRA are utilising a local supply chain the length and breadth of the Midlands.
Ian Johnson, project director with MMSDJV, said: “This is a fantastic milestone moment for the project team. Seeing the first span in place is the realisation of the collaborative, innovative approach to design that the Mott MacDonald and SYSTRA Design Joint Venture has embraced, which will ultimately help high speed trains to run from Old Oak Common to Birmingham.”
A total of 153 piers will be built for the viaducts in the triangle-shaped Delta Junction, with 15 completed already. At total of 2,762 viaduct segments are being made at HS2’s outdoor factory near Lea Marston using a ‘match-casting’ technique. This involves casting each segment against the following segment in a production line, creating a seamless viaduct deck when installed.
Each segment is said to be uniquely precise and adjustable by minimal tolerances. This approach – where each segment is poured against the previous one – ensures the whole geometry fits perfectly when assembled on site.
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