HS2 Pioneers Innovative Viaduct Construction Method

HS2 contractors are employing a specialist cantilever construction process for the first time in the country. This innovative method is being used to build the complex viaduct spans at the Delta junction in the West Midlands, a critical part of the HS2 high-speed rail project. The viaduct intersection is being constructed by Balfour Beatty Vinci, using a technique initially developed by the French civil engineering firm Campenon Bernard, now part of Vinci.

_{The Cantilever Construction Method}

The construction of the viaduct began with conventional methods, where precast viaduct segments were placed onto two 42-meter truss beams. These segments were then moved into position using a skidding trolley and secured using post-tensioning techniques. However, the project has since advanced to a more sophisticated phase, involving the use of a giant cantilever structure to extend the viaduct.

_{How the Cantilever Method Works}

The innovative cantilever method involves erecting a 22-meter high mast that anchors post-tensioning cable stays. These stays are crucial for supporting the concrete segments being installed at the leading edge of the construction. A 14-meter high mobile swivel crane is used to position these segments accurately. This approach is somewhat similar to the techniques used in constructing cable-stayed bridges, where temporary structures are essential to maintain stability during the building process.

Once the box viaduct is completed and the permanent post-tensioning tendons have been stressed, the temporary mast and stays are removed, leaving behind a fully extended and stable viaduct structure. This method not only allows for precise construction in challenging conditions but also ensures the structural integrity of the viaduct as it spans the complex junction.

Key Benefits

• Innovation in Construction: This is the first time the specialist cantilever method has been used in the UK, showcasing the ability to adopt and innovate with new techniques in large-scale infrastructure projects.
• Precision and Safety: The method allows for the safe and precise installation of viaduct segments, ensuring the long-term stability and safety of the structure.
• Efficiency: By using advanced techniques such as post-tensioning and temporary masts, the construction process is streamlined, reducing the time required for building complex intersections like the Delta junction.

The use of this innovative cantilever method by Balfour Beatty Vinci at the HS2 Delta junction marks a significant milestone in UK construction. It highlights the potential for adopting advanced engineering techniques to overcome complex challenges in infrastructure development.

As HS2 progresses, the success of this method could pave the way for its application in other challenging infrastructure projects across the UK. The ability to leverage such innovative techniques demonstrates the industry's commitment to advancing construction practices, ensuring that the UK's infrastructure continues to meet the demands of modern transportation.