Monitoring sediment buildup in underwater bridge tunnels with the help of high-energy muons

More than 200 submarine bridge tunnels exist for the circulation of vehicles worldwide, providing connectivity between cities. Once built, however, these tunnels are difficult to monitor and maintain, often requiring invasive stops or methods that have structural risks.

MUOGRAPHY – An imaging technique using high energy particles, called muons, which can cross hundreds of meters in the earth – can provide a non -invasive approach to examine the underground infrastructure.

In the Journal of Applied PhysicsA group of researchers from public and private organizations in Shanghai applied this technique to the tunnel of the exterior ring of Shanghai, which takes place under the Huangpu river as part of the city’s Ring motorway.

Because sediments made up of muddy soil and silt clay have higher density than water surrounding the tunnel, it is more effective in reducing the flow of muon than water alone. When placed in the tunnel, the researchers’ portable muon flow detection system is sensitive to these differences, proving useful to identify locations with high levels of sediment accumulation.

“Muons lose energy mainly by ionization, where they interact electromagnetically with electrons and eject electrons – denseness materials cause higher energy loss, effectively blocking more muons,” said author Kim Siang Khaw. “The granular or clay composition of the sediment intensifies this effect.”

Using a combination of a space scan lengthwise and a simulation of muons passing through a simplified tunnel model, the researchers have mapped the thickness of the sediments. They took 10 minutes of data per location at 50 meters intervals as proof of their technique, but in its real deployment, they plan to permanently install several detectors at fixed points throughout the tunnel, allowing 24 -hour surveillance.

They intend to extend their studies to several other tunnels in Shanghai and note that other cities can easily adopt technique in their own infrastructure. All that is necessary are basic information on the geometry and materials of the tunnel, environmental data and basic muon flow measurements.

“No complex model is necessary in advance – the method works with simplified inputs, validated by simulations in this study,” said Khaw. “This technique can also identify dangerous underground cavities, such as those formed when a hose exploded by the ground, creating a risk of hidden collapse.”

Muography has been used for archaeological studies, exploration of mines, and even more, but monitoring the change of a system over time is a relatively new and real application.

“We are now in a really exciting time for muography,” said Khaw. “We hope to collaborate with more researchers to apply this progress in fundamental sciences to the resolution of urgent societal challenges.”