Engineering news
Researchers have been using hundreds of sensors in a disused Royal Mail tunnel underneath London's West End to develop new techniques for monitoring and maintaining old tunnels.
The motion-detecting sensors are being used to ensure that the excavation of a new Crossrail platform tunnel at Liverpool Street Station doesn't disturb an existing 30m stretch of the “Mail Rail” tunnel, which runs just 3m above the new tunnel in some places.
The network of sensors can detect movements as small as one hundredth of a millimetre and uses optical fibre to show if the tunnel is deforming, wireless displacement transducers, photogrammetry or computer vision techniques and low power sensors to measure temperature, humidity, acceleration and tilt.
Researchers on the project, which is being run by the University of Cambridge with Crossrail and consultancy Arup, hope the low cost and long lasting sensor network will lead to improved techniques for the continuous monitoring and infrastructure in the future.
Researcher on the project, Mehidi Alhaddad, said: “The sensors paint an accurate and detailed picture of how the older tunnel is behaving, which will inform the best way to protect and maintain it.
“In future this type of technology could also be used to efficiently and economically monitor much of the UK's Victorian and 20th Century infrastructure, such as the miles of tunnels of the London Underground, 70% of which is made of cast iron, similar to the Royal Mail tunnel.”
The six mile long Mail Rail tunnel was used from 1927 to 2003 to shift mail from one side of London to the other while avoiding traffic jams and is just 2.5m in diameter. The Crossrail tunnel being excavated nearby is almost 11m in diameter.
The research team has helped with the ground monitoring at several Crossrail sites to reduce the possibility of damage at adjacent properties, and said that its sensor networks provide a complete picture of the entire tunnel and are cheaper and easier to install.
Sensors in the Mail Rail tunnel have detected only minor movement within acceptable parameters since the project started last year.
Professor Robert Mair, head of Civil Engineering and the Centre for Smart Infrastructure and Construction, said: “By installing the kind of sensors that can give a continuous update about how much those tunnels might be moving and what changes are taking place, we can answer a lot of important questions about the value of our current infrastructure, the future of it, whether it needs to be maintained, whether it needs to be replaced - all those kinds of issues can be much better quantified.”