Lifts, lizards and load cells at the M25 Wisley Interchange
If you drive around the southern section of the M25, you’ll be acutely aware of the major works happening at junction 10, aka the Wisley Interchange. (You’ve probably had plenty of time to look at the works too, as the tailbacks some days have been horrendous!)
All that work is moving towards a brand new bridge that will whisk drivers over the M25 when heading north or south. It’s a massive undertaking, given that 300,000 vehicles normally pass through the junction every single day. National Highways says that the project “Will create better connections and smoother traffic flows for the drivers who use it every day.”
Lifting and load cells
Load cells are no doubt at the very heart of the £317m project. During October 2023, a specialist 750t crane reached far across the (closed) M25 carriageway to lift ten 80 tonne precast concrete bridge beams into place. Commenting on the lift operation, National Highways senior project manager Jonathan Wade said:
“The upcoming bridge beam lift is another significant milestone for this transformative scheme. The beams measuring 33m in length, around the same as three double decker buses, and lifting them into place is a remarkable engineering feat by a highly skilled team of specialists.”
Building bridges
The main carriageway bridge is just one of eight new bridges at the interchange, five of which replace existing bridges due for demolition. Each bridge is a major undertaking in its own right. According to National Highways,
“Stratford Brook bridge…may be the smallest bridge on our scheme, it was the first to have all its beams lifted into place. Each of the nine pre-cast concrete beams weighs an impressive 45 tonnes – that’s roughly six adult elephants per beam, or a total of eight adult whales!”
UK’s first ever heathland bridge
The good news is that there will also be a new non-motorised bridge for cyclists, walkers and horse riders. It’s more than just a regular footbridge however:
“The Cockcrow bridge (is) the UK’s first ever heathland bridge. Spanning an impressive 30 metres in width and 68 metres in length, it will connect Ockham and Wisley commons for the first time and provide a safe, natural corridor for local wildlife.
” A four-metre track will weave across the bridge, laid with heather and other heathland shrubs for pedestrians, cyclists and horse-riders to enjoy. It will also help local creatures, such as sand lizards, silver studded butterflies and heath tiger beetles, to spread across the local area and encourage them to grow in numbers.”
In addition, the 14 acres of common land areas around the junction will be restored to woodland and native heathland, an important habitat for native British wildlife in this part of southern England.
Sensors in the soil
The new A3 bridges are also the subject of specialist research conducted by National Highways, AtkinsRéalis, and Cambridge University. It will look into the amount of materials actually required, as an article in The Construction Index explains:
“A new integral bridge on the M25 Wisley Interchange (junction 10) improvement scheme is going to be covered in sensors to measure the actual strain and stress profiles within the bridge and surrounding soil. The array of sensors and gauges will reveal whether the bridge could have been built with fewer materials.”
Commenting on the research, National Highways head of research Phillip Proctor said:
“This trial is important because integral bridges could offer greater durability and lower maintenance costs and provide a more sustainable alternative to the conventional design of bridge structures.”
And according to research partner AtkinsRéalis:
“This is the first data trial of its kind in the UK and demonstrates the value of cross-industry collaboration to support innovation and accelerate research in a real-world scenario. It will not only provide a rich data set that can be used to support further research into how Integral Bridges perform over time, it will also result in significant material and cost efficiencies over the lifespan of the bridge, positively contributing towards Net Zero targets.”
More about the Wisley Interchange Project
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