A46 Kenilworth box slide completed

Box slide for A46 Bypass Overbridge for High Speed Two (HS2) – Kenilworth, Warwickshire, UK
Autoripage of 14750 tonne box structure across A46

Client: Balfour Beatty VINCI (BBV)
Location: A46, near Kenilworth, Warwickshire, United Kingdom
Duration: Box structure constructed in 2024; box push completed in April 2025

The A46 is a key strategic highway in England, serving as an essential link within the national transport network by connecting the East and West Midlands. In Warwickshire, it provides direct access from Coventry to several major towns including Kenilworth, Leamington Spa, Warwick, and Stratford-upon-Avon, before continuing southward toward the M40. With over 480,000 vehicles travelling along the route each week, the A46 plays a vital role in supporting both local commuting and regional long-distance travel.

As part of the High Speed Two (HS2) – the UK’s landmark high-speed rail project – extensive infrastructure developments are underway between London and Birmingham. One such development is the construction of a new box structure beneath the A46 near Kenilworth. This structure is designed to carry the HS2 line under the existing highway without causing major disruption to road users.

To minimise the impact on the travelling public and nearby communities, the A46 Bypass Overbridge box structure – comprising approximately 4,300 cubic metres of concrete and 120 precast beams, weighing a total of around 14,750 tonnes – was constructed offline adjacent to the A46 throughout 2024.

Freyssinet was appointed by the client to carry out the box slide using Autoripage®, a patented method developed in-house. Leveraging our specialist knowledge in structural movement and heavy jacking systems, the operation was executed in April 2025 using a guided sliding system powered by hydraulic jacks, supported by 60 kilometres of strand cables and a purpose-built pushing slab.

One of the major challenges was the need to push the box uphill on a 1% gradient, which demanded precise control over the box’s vertical alignment throughout the operation. This required continuous monitoring and adjustment to ensure the structure remained within strict tolerances during movement.

Despite the complexity, the entire box push was successfully completed in 9.5 hours, 6.5 hours ahead of schedule, achieving outstanding results in terms of precision, safety, and minimal disruption to road users.

This milestone not only highlights the effectiveness of advanced construction methodologies but also underscores the value of strong collaboration between contractors, designers, and engineering specialists. Freyssinet is proud to have delivered this crucial component of the HS2 programme.

Scope of Work by Freyssinet in Autoripage ®

• Design of temporary guiding raft and pushing slab
• Design and supply of all necessary components for Autoripage ® including the anchorage blocks, passive/active deviators, steel inserts, strands, Ipalen plate, grease, bentonite etc.
• Installation of the strands for jacking operation.
• Design, supply, installation & commissioning of the hydraulic jacking system.
• Operate the box push operation.