The HS2 project is on track and Rendel and Ingerop have been developing models on the Colne Valley Viaduct and south Chiltern Tunnel portal designs. The present article will focus on the Colne Viaduct.

The £240-million, 3.4km-long, Colne Valley viaduct will run across four lakes and areas of woodland. The new viaduct is a multi-span, post-tensioned concrete segmental box-girder structure with a typical 60m-span variable-depth deck arrangement over the woodland areas. When the route crosses the lakes, the form evolves into a series of 80m-spans with V-shaped piers and an arched soffit. The viaduct has a continuous hybrid (opaque/non-opaque) noise mitigation system, performing as a noise barrier to avoid trains impacting wildlife and key noise receptors.  

Rendel and Ingerop are engaged to develop and deliver the scheme design of the Colne Valley Viaduct in Stage 1 followed by the Detailed Design in Stage 2, to the Design-and-Build Contractor ALIGN (Bouygues Travaux Publics, Sir Robert McAlpine and VolkerFitzpatrick JV). The services provided include: the design of the Colne Valley Viaduct and other structural elements (e.g. abutments); the design of associated approach embankments; geotechnical modelling, ground risk assessments and earthworks; soil-structure interaction analysis for piled foundations and earth-retaining structures; geological interpretation of data; development of ground models; highway designs for road diversions, realignments, new junctions, new access roads to compounds and transformer sites, highway scope definition, pavements, emergency hard standings, road drainage and vehicle swept path analysis and track alignments.
In addition, our work involves the production of 2D drawings and 3D BIM models of the designs to meet the ultimate client’s BIM and data management requirements. We are also carrying out environmental assessments, hydraulic modelling for river realignments/diversions, and acoustic modelling for the design of the noise barriers.

The viaduct design responds to the varied water and woodland environment it passes through with different shaped piers according to the landscape.

1. Woodland Piers

• Straight piers create typical spans of between 45-60m

• Increased number of piers compared to water areas in response to enclosed, intimate character of the wooded areas where long-distance views are limited

• As the woodland piers will be seen close-up, the texture and colour will be explored during the next design stage

2. Water piers

• V-shaped piers to allow wider structural spans of 80m

• Allow more openness over water and views through to the landscape beyond

• The curvature creates a more elegant silhouette which will give more pleasing water reflections

• The continuous curve creates a sense of flow and movement across the water

• Bearings will be 500mm above flood level

• The pier footings are designed to allow for 600mm movement whilst not appearing misaligned with the pier above

The Colne Valley Viaduct will be one of the longest viaducts in the UK. Together with the south Chiltern Tunnel also included in the section to be built by ALIGN it constitutes one of the most technical challenges of HS2 project.