HS2 Ltd's main works contractor, Align JV, comprising Bouygues Travaux Publics, Sir Robert McAlpine, and VolkerFitzpatrick, has embarked on an ambitious endeavour—the construction of the longest rail viaduct in the United Kingdom, known as the Colne Valley Viaduct. This monumental project involves the installation of around 300 piles that will serve as the foundation for this engineering marvel.
The Colne Valley Viaduct, an architectural masterpiece envisioned by Grimshaw Architects, spans an impressive 3.4 kilometres, surpassing the renowned Forth Rail Bridge by nearly 1 kilometre. Elevated approximately 10 meters above the picturesque River Colne, Grand Union Canal, and nearby lakes, this viaduct will play a pivotal role in facilitating the smooth passage of the railway.
To support the colossal structure, a network of 56 piers will be meticulously erected, featuring wider spans of 80 meters over the lakes and narrower spans at the approaches. This careful design approach was chosen to ensure that the viaduct seamlessly blends into the natural landscape, offering panoramic vistas and minimising its impact on the surrounding lakes.
The pile foundations, an integral component of the viaduct's stability, will delve deep into the earth, reaching depths of up to an astonishing 55 meters. Each pile will be meticulously capped with concrete to provide robust support to the piers, which, in turn, will bear the weight of the entire 6,000-ton bridge structure. To create these foundations, an innovative and efficient approach will be employed, involving the use of boring techniques followed by precise backfilling.
The main deck of the viaduct will be assembled with meticulous attention to detail. Manufactured in sections at a nearby temporary factory, this assembly process will take place from north to south, ensuring optimal construction practices and minimising disruptions to road traffic. The utilisation of a massive launching girder will further enhance the efficiency of this remarkable construction endeavour.
Daniel Altier, the project director at Align, exudes confidence that the Colne Valley Viaduct will become an iconic symbol of HS2 phase 1 upon its completion. Its awe-inspiring construction process is expected to captivate engineers of all generations, showcasing the ingenuity and expertise involved in bringing such a monumental structure to life. Altier joyfully celebrates the achievement of this significant milestone in the viaduct's construction, heralding the beginning of a new era in railway infrastructure.
Extensive testing of the piling process has already been undertaken, yielding valuable geological and structural data. This comprehensive analysis has greatly informed the viaduct's design, resulting i a remarkable 10-15% reduction in pile depth and the associated time and cost savings—a testament to the meticulous planning and innovative techniques employed throughout this ground-breaking project.