Beneath our feet are numerous underground cavities. Their presence is likely to affect the stability of the ground and therefore impact our roads. To prevent this risk, the departmental road teams are vigilant. Explanations.
According to the Northern Prefecture, nearly one in five northern municipalities have underground cavities in their basement. These galleries can be natural or result from the former industrial activity of our region (chalk quarries, mining, etc.).
Cutting-edge technology to prevent risks
Cambrésis is one of the areas where underground cavities are numerous and have already caused the subsidence of small portions of roads. To detect these galleries, the Department is currently testing a new technique called “microgravimetry”. This non-destructive method makes it possible to measure variations in subsoil densities using a device placed directly on the bitumen.
We are currently analyzing the subsoil of the RD 111 in Élincourt on a section of road 800 meters long
explains Gautier Cheval, division manager at the Cambrai road district. No particular risk has yet been noted there but the sector has numerous cavities. Detecting them makes it possible to anticipate possible road stability problems.
The device can probe the subsoil up to 15 meters deep. If it detects a particularly low underground density, the presence of a void or gallery is confirmed. In this case, a new intervention by the departmental roads is planned to fill what needs to be filled. And thus ensure your safety on the 4,500 km of roads for which the Department is responsible in the North.
Photo credits: C. Arnould
