Over 50 viaducts measuring about 9 miles (15km) in length will be built along the Phase One route. The UK’s longest viaduct will cross the Colne Valley. It will be over 2 miles (3.4km) long, which is 0.6 miles longer than the Forth Rail Bridge. Construction will begin with the biggest engineering challenges – such as the stations and tunnels – then the main viaducts and bridges, and finally meet in the middle with the route surface works.
Viaducts need to be sensitively and aesthetically sited, whilst addressing the technical demands of the project. For major viaducts, concepts are developed around key criteria, set by HS2 in consultation with the HS2 Independent Design Panel. These include whether the design fits the landscape, maintains views and landscape ‘flow’, is well proportioned and elegant.
The Colne Valley Viaduct
The Colne Valley viaduct will be one of the longest viaducts in the UK, and one of HS2’s best-known structures. Set low in the landscape, the design was inspired by the flight of a stone skipping across the water, with a series of elegant spans, some up to 80m long, carrying the railway around 10m above the surface of the lakes, River Colne and Grand Union Canal.
The structure will be supported by 56 piers, with the widest spans reserved for where the viaduct crosses the lakes, and narrower spans for the approaches. This design was chosen to enable views across the landscape, minimise the viaduct’s footprint on the lakes and help complement the natural surroundings.
Water Orton viaducts
There are designs for 2 viaducts near the village of Water Orton in Warwickshire, including new landscaped areas that will provide green public spaces and wildlife habitats.
The section of the HS2 route where the 2 viaducts are located is known as the Delta Junction, a triangular section of line where the new railway curves west towards Birmingham and runs north towards Crewe and beyond.
The landscape design will provide a new setting for the viaducts which are designed with slim support piers to enhance their design and reduce shading of the areas over which the railway will pass.
Wendover Dean viaduct
The Wendover Dean viaduct is set within an open side valley, which is defined by a rolling landform, overlaid by a simple historic field pattern, holloway, copses and tree lines. The design allows the natural landscape to flow beneath the new structure, whilst retaining important field boundary hedgerows and copses, and in particular the historic holloway which winds its way up the valley side.
Across the entire railway there will be around 60km of viaducts used. Phase One of the railway which runs from London to Birmingham, and is currently under construction, will have over 50 viaducts (15km). Over 500 bridging structures will also be constructed under and over the route.